To see the other types of publications on this topic, follow the link: Mobility of molecules.
Dissertations / Theses on the topic 'Mobility of molecules'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Mobility of molecules.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lapthorn, Cristian Lewis. "The application of ion mobility mass spectrometry to molecules of pharmaceutical significance." Thesis, University of Greenwich, 2016. http://gala.gre.ac.uk/18125/.
Full textAbstract:
Ion mobility-mass spectrometry experiments have been conducted to measure the drift-time and calculate collision cross-sections (CCSs) using travelling wave ion mobility spectrometry, and determine the CCS using drift-tube ion mobility spectrometry systems of analytes. The aim of the study was to identify if predictive approaches could facilitate rapid and definitive assignment of charge location sites and chemical structure. Molecular modelling was conducted to determine the energy minimised/geometry optimised structures and charge distribution of the protonated molecules studied. The geometry and charge distribution data were utilised in subsequent ion mobility calculations using two main methods 1) projection approximation and 2) trajectory method. Fluoroquinolone antibiotics were investigated as previous literature had postulated the ion mobility separation of charge location isomers differing only by their protonation site with little expected difference in their geometry (see Chapter 2). Projection approximation prediction of theoretical CCSs (tCCSs) for the singly protonated molecules of norfloxacin (with the proton assigned to all possible oxygen or nitrogen-containing protonation sites to generate candidates) revealed < 2 Å2 difference in tCCSs based on molecular modelling. In stark contrast the experimental CCS (eCCS) demonstrated > 10 Å2 difference between different components. The product ion spectra are consistent with the hypothesis of charge location isomer mobility separated components. Investigations with other fluoroquinolones, with both drift-tube ion mobility and travelling wave ion mobility, and using the trajectory method, remain consistent with the hypothesis of charge location isomers (see Chapter 3). A larger scale study sought to probe the accuracy of tCCSs over a large number of small molecule drug structures. If tCCSs accurately predict eCCSs, then tCCSs could be used to identify compounds and isomers based on their CCSs (see Chapter 4). Finally, software was developed to considerably accelerate the calculation of trajectory method tCCSs from 8-100 times faster than existing published approaches depending on available computing infrastructure (see Chapter 5). In summary this research project has explored whether eCCSs and tCCSs may be useful as a key structural tool alongside other traditional measurements including chromatographic retention time and m/z.
2
Chen, Yun Jacobson Ken. "Studying lateral mobility of surface molecules on the plasma membrane using biophysical approaches." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,964.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.<br>Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the Doctor of Philosophy degree in the Department of Biomedical Engineering." Discipline: Biomedical Engineering; Department/School: Medicine.
3
Khalifeh, Iman. "Determination of self association constant between bovine insulin molecules by capillary zone electrophoresis." Thesis, Uppsala University, Department of Medical Biochemistry and Microbiology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6155.
Full textAbstract:
<p>Capillary electrophoresis (CE) is an analytical technique that is very useful for investigating processes that modify the charge and mass of proteins and polypeptide pharmaceuticals. This report explores the ability of CE to determine the aggregation constant between insulin molecules. Bovine insulin is a polypeptide (Mw=5733, pI = 5.3) that has two α-amino groups (Gly and Phe) and one ε–amino group (Lys). Analysis of concentration dependence of electrophoretic mobility of insulin at different conditions yields the association constant for dimerization of insulin. The association constant estimates how tight the peptide molecules are associated. The association constant is a useful factor to evaluate the purity of a peptide or protein sample.</p><p>The association reaction of bovine insulin molecules was found to be favoured by temperature. The association constants were 7200 M -1, 8000 M -1, and 36000 M -1 at 15 oC, 25 oC and 35 oC, respectively. The interactions between the peptide molecules increase at higher temperature, resulting in stronger association. The association constant was estimated to be 3000 M -1in the presence of dioxane (5%, w/v %) at 25 oC. However, the interaction sites remain to be explored.</p>
4
Bahra, Sukhvinder Singh. "Investigations into the mobility of cell-surface MHC molecules using an IgG-Oregon Green probe : a FRAP investigation." Thesis, University of Essex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396061.
Full text
5
Platt, Sean P. "Interactions of the Naphthalene Radical Cation with Polar and Unsaturated Molecules in the Gas Phase." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4210.
Full textAbstract:
Characterizing the interactions of solvent molecules with ions is fundamental in understanding the thermodynamics of solution chemistry. These interactions are difficult to observe directly in solution because the number of solvent molecules far exceed that of ions. This lend the gas phase to be the ideal medium in the study ion-solvent interactions on a molecular level. Ionized polycyclic aromatic hydrocarbon (PAH) molecules can readily form hydrogen bonds with neutral solvent molecules in aqueous and interstellar medium. Previous research has been done for stepwise solvation of small molecules such as benzene+, pyridine, and phenylacetylene. The similarity in these results show that these organic ions can be considered prototypical model systems for aromatic ion-neutral solvent interactions. The goal of this dissertation is to demonstrate that naphthalene can act as a prototypical model of PAH ions for ion-solvent interactions.
Two types of experiments are considered throughout this dissertation using ion mobility mass spectrometry: (1) ion-neutral equilibrium thermochemistry and (2) mobility measurements. For thermochemistry experiments, the naphthalene radical cation was injected into the drift cell containing helium and/or neutral solvent vapor and the enthalpy and entropy changes were measured by varying the drift cell temperature and measuring the equilibrium constants. The results of these studies showed that small polar molecules bind to naphthalene with similar energy based on the measured by the enthalpy changes. Unsaturated aliphatic molecules behave similarly, but with much lower binding energy. Aromatic ions tend to bind to the naphthalene with lower binding energy than that observed with the benzene ion. The results for small polar molecules were compared to similar studies using the phenyl cation. The second series of experiments required the coexpansion of the naphthalene and benzene or pyridine. Injecting theses dimers into the drift cell allowed the measurement of reduced mobility on the dimers at a series of temperatures. These were used to calculate the average collision cross section and thus give insight in to the structure of these aromatic dimers. Structures were determined by comparing these results to those predicted by DFT calculations.
6
Pearcy, Adam C. "Non-covalent and covalent interactions between phenylacetylene and quinoline radical cations with polar and non-polar molecules in the gas phase." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5990.
Full textAbstract:
Gas phase molecular clusters present an ideal medium for observing factors that drive chemical reactions without outside interferences from excessive solvent molecules. Introducing an ion into the cluster promotes ion-molecule interactions that may manifest in a variety of non-covalent or even covalent binding motifs and are of significant importance in many fields including atmospheric and astronomical sciences. For instance, in outer space, molecules are subject to ionizing radiation where ion-molecule reactions become increasingly competitive to molecule-molecule interactions. To elucidate individual ion-molecule interaction information, mass spectrometry was used in conjunction with appropriate theoretical calculations.
Three main categories of experiment were conducted in this dissertation. The first of which were thermochemical equilibrium measurements where an ion was introduced to an ion mobility drift cell wherein thermalizing collisions occur with helium buffer gas facilitating a reversible reaction with a neutral molecule allowing the standard changes in enthalpy and entropy to be determined. The second type of experiment was an ion mobility experiment where an ionized homo- or hetero-cluster was injected into the drift cell at specific conditions allowing the reduced mobility and collisional cross-section to be evaluated. Thirdly, kinetics measurements were taken following injection of an ion into the drift cell were an irreversible reaction ensued with the neutral species hindering equilibrium, but prompting rate constant assessment.
Previous research has laid the groundwork for this dissertation as the results and discussion contained herein will build upon existing data while maintaining originality. For example, past work has given support for ion-molecule reactions involving precursor species such as acetylene and hydrogen cyanide to form more complex organics, perhaps leading to biologically relevant species. The chemical systems studied for this research are either ionized substituted benzenes like phenylacetylene and benzonitrile or polycyclic aromatic nitrogen-containing hydrocarbons like quinoline and quinoxaline interacting with a variety of neutral species.
Hydrogen bonding and its many sub-sections are of the utmost importance to the kinds of reactions studied here. Past work has shown the tendency of organic radical cations to form conventional and unconventional ionic hydrogen bonds with gas phase solvents. Other non-covalent modes of interaction have also been detected in addition to the formation of covalently bound species. Gas phase reactions studied here will explore, via mass-selected ion mobility, reversible and irreversible reactions leading to binding enthalpy and entropy and rate constant determination, respectively, in addition to collisional cross-section determination.
7
Täuber, Daniela, Mario Heidernätsch, Michael Bauer, Günter Radons, Jörg Schuster, and Christian von Borczyskowski. "Single molecule tracking of the molecular mobility in thinning liquid films on thermally grown SiO 2." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-191721.
Full textAbstract:
Diffusion coefficients obtained from weighted mean square displacements along probe molecule trajectories within ultrathin liquid TEHOS films show a correlation with film thickness. By studying cumulative distributions obtained with a time resolution of 20 ms,
we could show that the diffusion is heterogeneous within our liquid films which consist of a few molecular layers only.
We detected two components of the diffusion process, a slower and a faster one. Thinning of the film due to evaporation caused a slowdown of the whole diffusion process. But this resulted not from a slowdown in the two contributing components itself. Instead their relative contributions changed in favor for the slow component. We conclude that there is no pronounced difference in the diffusion coefficients attributed to the molecular layers 3 to 5 vertically above the substrate, but with the loss of upper layers along with the thinning process the concentration of probe molecules in the near surface region containing only one or two molecular layers is increased.
8
Täuber, Daniela, Mario Heidernätsch, Michael Bauer, Günter Radons, Jörg Schuster, and Christian von Borczyskowski. "Single molecule tracking of the molecular mobility in thinning liquid films on thermally grown SiO 2." Diffusion fundamentals 11 (2009) 107, S. 1-11, 2009. https://ul.qucosa.de/id/qucosa%3A14081.
Full textAbstract:
Diffusion coefficients obtained from weighted mean square displacements along probe molecule trajectories within ultrathin liquid TEHOS films show a correlation with film thickness. By studying cumulative distributions obtained with a time resolution of 20 ms,
we could show that the diffusion is heterogeneous within our liquid films which consist of a few molecular layers only.
We detected two components of the diffusion process, a slower and a faster one. Thinning of the film due to evaporation caused a slowdown of the whole diffusion process. But this resulted not from a slowdown in the two contributing components itself. Instead their relative contributions changed in favor for the slow component. We conclude that there is no pronounced difference in the diffusion coefficients attributed to the molecular layers 3 to 5 vertically above the substrate, but with the loss of upper layers along with the thinning process the concentration of probe molecules in the near surface region containing only one or two molecular layers is increased.
9
Carsí, Rosique Marta. "Molecular mobility. Structure-property relationship of polymeric materials." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/59460.
Full textAbstract:
[EN] The present work examines the influence of the chemical structure of polymers on thermal, mechanical and dielectric behavior. The experimental techniques used for the purpose are differential scanning calorimetry, dynamo-mechanical analysis and dielectric spectroscopy. Additionally, in order to confirm the results obtained using the above methods, other techniques such as ray diffraction have also been employed.
Chapters 1 and 2 contain the introduction and the objectives, respectively. Chapter 3 briefly describes the experimental techniques used.
Chapter 4 contains the findings of the comparative analysis of the response to electrical noise fields for three poly(benzyl methacrylates) with different structures. The analysis was carried out under a wide range of frequencies and temperatures on three poly(benzyl methacrylates) containing two dimethoxy groups in positions 2,5-, 2,3- and 3,4-. The results show that the position of the dimethoxy groups on the aromatic ring has a significant effect on the molecular dynamics of poly(benzyl methacrylate). The spectra obtained were of high complexity and therefore, in order to perform a better analysis, numerical methods for time-frequency transformation including the use of parametric regularization techniques were used. We studied the effect of this structural change on the secondary relaxation processes and relaxation process , relating to the glass transition. We also analyzed the effect of the dimethoxy group position on the formation of nanodomains, in which the side chains are predominant, and on the conduction processes of the materials tested.
In Chapter 5, the conductivity of rubbery liquids was studied by analyzing poly(2,3-dimethoxybenzyl methacrylate), which exhibits its own particular behavior. The chapter analyzes the principle of time-temperature superposition, employing different interrelated variables.
Chapter 6 focuses on how the presence of crosslinking affects the molecular mobility of polymethacrylates containing aliphatic alcohol ether residues. In this case, the effect of crosslinking on the secondary and primary relaxation processes was analyzed. The creation of nanodomains in the side chains as a result of the presence of crosslinking was also studied.<br>[ES] En este trabajo se presenta un estudio de la influencia de la estructura química de los polímeros en su comportamiento térmico, mecánico y dieléctrico. Las técnicas experimentales empleadas para ello han sido la calorimetría diferencial de barrido, el análisis dinamo-mecánico y la espectroscopia dieléctrica. Adicionalmente, se han empleado otras técnicas como la difracción de rayos, con objeto de corroborar los resultados obtenidos por las primeras.
En los Capítulos 1 y 2 se recoge la introducción y los objetivos, respectivamente. El Capítulo 3 presenta una breve descripción de las técnicas experimentales empleadas.
En el Capítulo 4 se recogen los resultados obtenidos en el análisis comparativo de la respuesta a campos de perturbación eléctrica en un amplio rango de frecuencias y temperaturas para tres polimetacrilatos de bencilo con dos grupos dimetoxi en posiciones 2,5-, 2,3- y 3,4-. Los resultados obtenidos señalan el importante efecto de la posición de los grupos dimetoxi en el anillo aromático, sobre la dinámica molecular del polimetacrilato de bencilo. Los espectros obtenidos fueron muy complejos, por ello en orden a llevar a cabo un mejor análisis se emplearon métodos numéricos para la transformación tiempo-frecuencia que incluyeron el uso de técnicas de regularización paramétrica. Se ha estudiado el efecto que dicho cambio estructural ejerce tanto sobre los procesos de relajación secundaria como sobre el proceso de relajación α, relacionado con la transición vítrea. Así mismo, se ha analizado el efecto de la posición de los grupos dimetoxi en la formación de iii
nanodominios en los que predominan las cadenas laterales, y su efecto en los procesos de conducción de los materiales analizados.
En el Capítulo 5 se recoge el estudio de la conductividad de líquidos gomosos tomando como modelo el poli (metacrilato de 2,3-dimetoxibencilo), por su peculiar comportamiento. En este capítulo se ha realizado un análisis del principio de superposición tiempo-temperatura, empleando para ello diferentes variables relacionadas entre sí.
En el Capítulo 6 se recoge el efecto de la presencia de entrecruzante en la movilidad molecular de polimetacrilatos que contienen residuos de éteres de alcoholes alifáticos. En este caso, se ha analizado el efecto de la presencia de entrecruzante tanto en los procesos de relajación secundarios, como en el proceso de relajación principal. También se llevó a cabo un análisis del efecto que la presencia de entrecruzante tiene sobre la creación de nanodominios gobernados por las cadenas laterales.<br>[CAT] En aquest treball es presenta un estudi de la influència de l'estructura química dels polímers en el seu comportament tèrmic, mecànic i dielèctric. Les tècniques experimentals utilitzades han sigut la calorimetria diferencial de rastreig, l'anàlisi dinamo-mecànic i l'espectroscòpia dielèctrica. Addicionalment, s'han empleat altres tècniques com la difracció de rajos X a fi de corroborar els resultats obtinguts per les primeres.
En els Capítols 1 i 2 s'arreplega la introducció i els objectius, respectivament. Al Capítol 3 es presenta una breu descripció de les tècniques experimentals emprades.
En el Capítol 4 es recull els resultats obtinguts en l'anàlisi comparativa de la resposta a camps de pertorbació elèctrica en un ampli rang de freqüències i temperatures de tres polimetacrilats de benzil amb dos grups metoxi en posicions 2,5-, 2,3- i 3,4-. Els resultats obtinguts assenyalen l'important efecte de la posició dels grups metoxi en l'anell aromàtic, sobre la dinàmica molecular del polimetacrilat de benzil. Els espectres obtinguts van ser molt complexos, per aquesta raó per a dur a terme un millor anàlisi es van emprar mètodes numèrics per a la transformació temps-freqüència que van incloure l'ús de tècniques de regularització paramètrica. S'ha estudiat l'efecte que el dit canvi estructural exerceix tant sobre els processos de relaxació secundària com sobre el procés de relaxació , relacionat amb la transició vítria. Així mateix, s'ha analitzat l'efecte de la posició dels grups metoxi en la formació de nanodominis en els que predominen les cadenes laterals, i el seu efecte en els processos de conducció dels materials analitzats.
En el Capítol 5 s'arreplega l'estudi de la conductivitat de líquids gomosos prenent com a model el poli-(metacrilat de 2,3-dimetoxibencilo), pel seu peculiar comportament. En aquest capítol s'ha realitzat un anàlisi del principi de superposició temps-temperatura, emprant per a això diferents variables relacionades entre sí.
En el Capítol 6 s'arreplega l'efecte de la presència d'entrecreuat en la mobilitat molecular de polimetacrilats que contenen residus d'èters d'alcohols alifàtics. En aquest cas, s'ha analitzat l'efecte de la presència d'entrecreuat tant en els processos de relaxació secundaris, com en el procés de relaxació principal. També es va dur a terme un anàlisi de l'efecte que la presència d'entrecreuat químic té sobre la creació de nanodominis governats per les cadenes laterals.<br>Carsí Rosique, M. (2015). Molecular mobility. Structure-property relationship of polymeric materials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59460<br>TESIS<br>Premiado
10
Le, Quang Hien 1972. "Diversity and mobility of transposons in Arabidopsis thaliana." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38497.
Full textAbstract:
Transposons are a diverse collection of mobile genetic elements and are important components of nearly every genome. Because of their mobile and repetitive nature, transposons can have considerable effects on host gene expression, genome organization and evolution. The recent availability of genomic sequence information has expedited the discovery and study of transposons, as exemplified in this thesis by the complete genome analysis of the model plant system Arabidopsis thaliana. Data mining in Arabidopsis has revealed a rich diversity of transposons, of which Basho and Terminal-repeat Retrotransposons In Miniature (TRIM) elements were previously unknown types. The identification of Related to Empty Sites (RESites) provide evidence for past transposition events. Examples of elements contributing to coding regions, acquiring cellular sequences, along with in-depth analysis of the insertions, their target sites and their distribution illustrate the impact of transposons on gene and genome structures. Computer-based searches of genomic sequences has also improved our understanding of previously identified transposon families, such as the origin, classification and mobilization of Tourist elements. In addition, information on transposons gathered from in silico analysis of genomic sequences has served to design in vivo experiments. In a whole genome strategy, Transposon Display was used to investigate transposition and regulation of mobility of Tourist-like elements in A. thaliana and in the nematode Caenorhabditis elegans.
11
Griffiths, John Robert. "Structural studies using ion mobility spectrometry." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366069.
Full text
12
NUR, MUHAMMAD. "Etudes des décharges couronne dans l'argon et l'azote très purs : transport des charges, spectroscopie et influence de la densité." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10297.
Full textAbstract:
Cette these presente les resultats des etudes electriques et spectroscopiques des decharges couronnes en geometrie point-plan dans l'argon et l'azote tres purs (de la densite du gaz au liquide). Les phenomenes du transport des porteurs de charge tels que la mobilite des porteurs (electron et ions) et sa dependance avec la densite et la purete du fluides ont ete etudies a partir des mesures electriques. L'analyse spectroscopique a ete effectuee dans la zone d'ionisation (plasma hors-equilibre) : pour l'argon, les effets de la pression sur les raies atomiques tels que l'elargissement et le deplacement ont ete etudies. Dans la zone d'ionisation, les temperatures d'excitation (t#e#x#c. ), electronique (t#e) et du plasma (t#p) ont ete determinees, en utilisant l'emission des raies atomiques et le fond continu. Nous avons egalement distingue entre la zone d'ionisation et la zone de transport a partir de l'etude spatio-temporelle des spectres d'emission des raies atomiques et celui du rayonnement continu. Pour l'azote, les spectres d'emissions de la molecule excitee et de la molecule ionisee sont montres et analyses. A l'aide de l'analyse spectrale du deuxieme systeme positif (c#3u-b#3g) de n#2 et du premier systeme negatif (b#2#+#u - x#2#+#g) de n#2#+, nous avons determine les differentes temperatures (rotationnelle t#r t#p, vibrationnelle t#v et electronique t#e) de la zone de la decharge luminescente continue. L'etude spatio-temporelle des spectres d'emission dans cette decharge, nous a permis de distinguer la zone d'ionisation et la zone de transport a partir de l'analyse de l'emission des radicaux comme nh et cn. Nous discutons les resultats obtenus en les confrontant avec ceux obtenus par d'autres auteurs et par fois avec la theorie correspondente.
13
Farhat, Imad Akil. "Molecular mobility and interactions in biopolymer-sugar-water systems." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339660.
Full text
14
Muir, J. "Molecular mechanisms controlling GABAA receptor clustering and lateral mobility." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1338986/.
Full textAbstract:
γ-aminobutyric acid type A receptors (GABAARs) are the major mediators of inhibitory neurotransmission in the mammalian CNS. They play a critical role in regulating the excitatory/inhibitory balance required for correct brain function. Inhibitory synaptic strength depends on the number of GABAARs at the synapse, which can be regulated by trafficking mechanisms controlled by protein-protein interactions and post-translational modifications. Recently, it has become clear that neurotransmitter receptors can undergo lateral exchange between synaptic and extrasynaptic regions. This thesis is centred on the study of GABAAR surface trafficking with live-cell imaging techniques in cultured hippocampal neurons. GABAAR clustering at inhibitory synapses is monitored via super-ecliptic pHluorin tagging, and single particle tracking with quantum dot labelling is used to image GABAAR lateral mobility. Computational tools developed for single particle tracking of GABAARs are described herein. Characterisation of GABAAR clustering and lateral mobility under baseline conditions reveals that GABAAR clusters are stable, but that single GABAARs can move rapidly into and out of synapses. GABAAR surface trafficking is found to be activity-dependent. Ca2+ in ux through NMDA receptors drives the rapid dispersal of GABAAR clusters from synapses and increases GABAAR lateral mobility. This requires activation of calcineurin and dephosphorylation of serine 327 on the GABAAR γ2 subunit. Finally, GABAAR clustering and lateral mobility in the axon initial segment (AIS) is analysed. A chronic depolarisation stimulus which shifts the AIS away from the cell body is then used. GABAAR cluster positions remain xed along the axon, but GABAAR lateral mobility in the AIS and proximal axon is increased. These effects require activation of voltage-gated Ca2+ channels. In summary, this work reveals that GABAAR surface trafficking can be modulated by multiple molecular mechanisms, which may have important functional consequences for information processing in the brain.
15
Sills, Scott E. "Interfacial nanorheology : probing molecular mobility in mesoscopic polymeric systems /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9832.
Full text
16
Anyetei-Anum, Cyril S. "Acetylation Controls Thyroid Hormone Receptor Intracellular Localization and Intranuclear Mobility." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153816.
Full textAbstract:
Thyroid hormone receptor (TR) is responsible for mediating the expression of genes involved in growth, development, and homeostatic regulation, in response to thyroid hormone. There are two main subtypes of TR, TRα1 and TRβ1, that mediate these physiological processes. Dysregulation of TR mediated processes is a contributing factor in disease pathology. Our prior studies show that TR is shuttled rapidly between the nucleus and cytosol, while localizing primarily to the nucleus. TRα1 contains two nuclear localization signals (NLSs) that act together to confer strong nuclear localization, while TRβ1 only contains one NLS (NLS-1). Recently, we found that the intracellular localization of TR is regulated, in part, by post-translational modification of lysines within NLS-1 by acetylation. We constructed GFP or mCherry-tagged TRα1 and TRβ1 acetylation-mimic and nonacetylation-mimic (unable to be endogenously acetylated) expression plasmids, transfected them into HeLa cells, and used fluorescence microscopy to determine the nuclear/cytosolic (N/C) ratio of the mutant receptors by measuring fluorescence intensity. Data show that the TR acetylation mimic has a significantly lower N/C ratio compared to wild-type TR, indicating a striking decrease in nuclear localization, whereas the TR nonacetylation mimic's N/C ratio was the same as wild-type TR. Previously, we showed that TR nuclear import is mediated by importins 7, β1, and α1. We hypothesized that acetylation state alters either TR's ability to bind importins or its intranuclear mobility, and that inhibition of the acetyltransferase CBP/p300 would lead to enhanced TR nuclear localization, while inhibition of the deacetylase SIRT1 would lead to TR cytoplasmic localization. Using GFP-Trap co-immunoprecipitation, we found that importins 7, β1, and α1 interact with both the TRα1 acetylation and nonacetylation mimics, suggesting that the TRα1 acetylation mimic's decreased nuclear localization is due to factors other than reduced importin binding. Intriguingly, fluorescence recovery after photobleaching (FRAP) revealed that the GFP-TRα1 nonacetylation mimic has a significantly slower rate of recovery than wild-type TRα1, suggesting that this reduced mobility correlates with greater nuclear retention. in contrast, the GFP-TRα1 acetylation mimic had the same rate of recovery as wild-type TRα1. Lastly, pharmacological inhibition of CBP/p300 by C646 increased GFP-TRβ1's nuclear localization in a dose-dependent manner (GFP-TRβ1 has a slight cytosolic population due in part to having one NLS); however, inhibition of SIRT1 by EX-527 did not alter GFP-TRα1's localization. Taken together, these data provide further evidence that acetylation plays a key regulatory role in TR shuttling and retention and extends our understanding of how acetylation interplays with TR-regulated processes of growth and development.
17
Brás, Ana Rita Elias. "Influence of constraining and confinement in the molecular mobility of low molecular weight materials." Doctoral thesis, FCT - UNL, 2009. http://hdl.handle.net/10362/2670.
Full textAbstract:
Dissertation presented to obtain a Ph.D. Degree in Chemical Physics<br>Despite the importance that the glassy state has nowadays, the transition from liquid to the glass, glass transition, still remains a matter of debate which constitutes one of the great condensed matter physics challenges. Since this fact is closely related to the cooperativity dynamics, the study of this phenomenon in glass-forming liquids under confinement in the nanometer scale, has recently emerged as a strategy to clarify factors such as the existence of an
inherent length scale of the cooperative dynamics that determines the glass transition
temperature. In this context, this thesis represents an additional contribution to the study of molecular dynamics of glass-forming liquids under confinement in nanoporous inorganic materials. As target compounds the liquid crystal E7 and the drug Ibuprofen were selected.
Since the first exhibit various transitions makes it more sensitive to perturbations and thus appears as the ideal candidate to evaluate confinement effects. The study of ibuprofen is of particular interest because confinement emerges as a method of stabilizing the amorphous phase that is mostly important in pharmaceutical applications. Dielectric Relaxation Spectroscopy(DRS) is the main technique used to obtain detailed information about the molecular mobility in a wide range of frequencies (10-2-109Hz) (Chapter I and II).
The first part of the thesis is devoted to the characterization of the two target compounds in the bulk state. The combination of DRS with the specific heat spectroscopy allowed to determine which of the E7 observed relaxation processes (a process in the isotropic phase and two processes in the nematic phase: δ and tumbling) is responsible for the glass transition
temperature Tg (tumbling process). Detailed studies of ibuprofen molecular mobility in the liquid, supercooled liquid and glassy states are also presented in this chapter, where four relaxation processes are detected: two secondary processes (γ and β), the cooperative process related to Tg (α ) and the Debye process (D), probably related to the hydrogen bonding dynamics. This study was preceded by an optimization of the conditions to obtain amorphous Ibuprofen which is a crystal in its natural state (Chapter III).
In the next chapter (Chapter IV), the molecular dynamics of E7 confined to untreated and phospholipid lecithin treated rigid inorganic membranes with 20 nm pore diameter was evaluated. It was found that both the liquid crystal alignment, as well as the dynamics is influenced by confinement and treatment of the surface pores. Additionally, E7 was further studied confined to the mesoporous materials MCM-41 and SBA-15 type, 100% silica composition and pore size between the 2.8 and 6.8 nm. A multiplicity of relaxation processes was revealed by DRS, including the modes already observed in the bulk E7. In addition, two<br>Fundação para a Ciência e Tecnologia (FCT),financial support by means of the PhD grant SFRH/BD/23829/2005
18
Meneau, Aurélie Yvette Béatrice. "Charge transport physics of high-mobility, solution-crystallised molecular semiconductors." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708741.
Full text
19
Guo, Zhenrong. "Characterization of ionic, dipolar and molecular mobility in polymer systems." W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539623474.
Full textAbstract:
Changes in the ionic and dipolar molecular mobility in a polymer system are the basis for the changes in the dielectric mechanical properties of polymer materials. Frequency Dependent Dielectric Measurements (FDEMS) and Ion Time-of-Flight (ITOF) are two important techniques to investigate ionic and dipolar molecular mobility in polymer systems. The results can be related to the macro- and molecular dielectric, electrical and dynamic properties of polymeric materials. The combination of these two methods provides a full view of electric, dielectric and dynamic behavior for the systems as they undergo chemical and/or physical changes during polymerization crystallization, vitrification, and/or phase separation.;The research on microscopic mass mobility in polymer systems was done on three aspects: (1) ion mobility in an epoxy-amine reaction system; (2) dipolar mobility and relaxation during dimethacrylate resin cure and (3) dye molecule migration and diffusion in polymer films.;In the ion mobility study, we separately monitor the changes in the ion mobility and the number of charge carriers during the epoxy-amine polymerization with FDEMS and ITOF measurements. The isolation of the number of carriers and their mobility allows significant improvement in monitoring changes in the state and structure of a material as it cures.;For the dipolar mobility and relaxation study, FDEMS measurements were used to detect structural evolution and spatial heterogeneity formation during the polymerization process of dimethacrylate resins. The dielectric spectra, glass transition (Tg) profiles and dynamic mechanical measurements were used to investigate the existence of two cooperative regions of sufficient size to create two alpha-relaxation processes representing oligomer rich and polymer microgel regions during the polymerization.;For the dye migration research, we tried to develop a visually color changing paper (VCP) due to dye molecule migration in polymer films. The mobility of dye molecules in polyvinyl films was controlled by the acidity of the environment. Ionamine derivatives of dyes were stable when mixed with acid. their diffusion in polymer films can be quickly triggered as the result of an acid/base neutralization reaction. The effect of the type of base, acid and the compatibility of polymer films on the diffusion rate is discussed.
20
Lontine, Derek Michael. "Stress Modulated Grain Boundary Mobility." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7348.
Full textAbstract:
This thesis consists of a thermodynamically based kinetic model that more accurately predicts grain boundary mobility (GBM) over a large range of thermodynamic states including changes in temperature, pressure and shear stress. The form of the model was validated against calculated GBM values for Al bicrystals via molecular dynamics (MD) simulations. A total of 98,786 simulations were performed (164 different GBs, each with a minimum of 250 different thermodynamic states, and 2 different driving forces). Methodology for the computation of the GBM via MD simulations is provided. The model parameters are directly linked to extensive thermodynamic quantities and suggest potential mechanisms for GBM under combined thermal and triaxial loads. This thesis also discusses the influence of GB character on the thermodynamic mobility parameters. The resulting insights about GB character and thermodynamic state on GBM suggest an opportunity to achieve designed microstructures by controlling thermodynamic state during microstructure evolution.
21
Holden, Nicola Kathleen. "Atmospheric ion measurements using novel high resolution ion mobility spectrometers." Thesis, University of the West of England, Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288184.
Full text
22
Roussenova, Mina. "Molecular organisation and mobility in glass forming systems : a free volume perspective." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541646.
Full text
23
Ravi, Sankar Ashwin. "Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50414.
Full textAbstract:
Organic π-conjugated Donor-Acceptor copolymers are emerging as potential candidate materials for organic field effect transistor (OFET) and organic photovoltaic (OPV) applications. The electron-deficient benzothiadiazole group coupled with an electron-rich oligothiophene to form donor-acceptor copolymers has attracted significant attention. These low optical band gap materials absorb photons in the range of 400-800 nm and exhibit good thermal stability. In particular, poly(benzothiadiazole-sexithiophene) (PBT6) exhibits excellent performance in optoelectronic devices and high thermal stability. Here, we present the chemical synthesis and characterization of the polymer, PBT6. Three samples of PBT-6 with differing molecular weights in the range of Mn 18000-45000 Da were synthesized. Each polymer was characterized with respect to its photophysical, thermal properties and field-effected mobility was determined. Devices were prepared by drop-casting polymer solutions in 1,2-dichlorobenzene (DCB) onto an OFET (bottom gate/bottom contact) substrate and the devices were used to examine the charge transport properties of each polymer system. The optimal solvent to be used for processing technique was determined and surface techniques using OTS-8 and OTS-18 were compared through contact angle measurements. The measured charge carrier mobilities were in the range of 0.45-0.6 cm² / V.s. Polymer films prepared via drop-casting and which were thermal annealed exhibit mobilities as high as 0.825 cm² / V.s. This work examines the effect of molecular weight on the charge carrier transport properties and demonstrates the correlation of performance with molecular ordering. Drop-casted films of PBT-6 exhibit highly ordered crystalline lamellar structure with high degree of π- π stacking with edge-on orientation on the substrate. The longer conjugation lengths promote intrachain charge transfer. This high degree of molecular ordering in high MW samples of PBT6 improves the interchain and intrachain charge transfer leading to enhanced mobilities. The increased molecular weight (MW) facilitates in forming more uniform thin films which is vital in processing and application of polymer thin film technologies. These results and observations clearly demonstrate the potential of PBT-6 as a semiconducting material for Optoelectronic devices.
24
Magri, Andrea. "Multifunctional complexes for molecular devices." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE036/document.
Full textAbstract:
Les semi-conducteurs organiques à base d’aluminium ont été systématiquement synthétisés et caractérisés par méthodes photo-physiques et électrochimiques. Une étude de leur relation structure-propriétés électroniques a été menée. Les orbitales frontières ont été comparées à celles obtenues par calcul. De nouvelles méthodes ont été utilisées permettant une description de la morphologie des SCOs et un calcul de mobilité des porteurs de charges associés. La mobilité des trous dans Al(Op)3 a été mesurée sur des transistors en film minces: 0.6-2.1×10−6cm2V−1s−1. Par des techniques de spectroscopie en photoémission, la surface de l’hybride Co/Al(Op)3 a été sondée, révélant deux états d’interfaces hybrides, où la polarisation de spin de HIS1 est 8% plus élevée comparée au cobalt nu, et 4% plus faible dans HIS2. Enfin, des aimant moléculaires à base de phénalényle ont été étudiés. [Dy(Op)2Cl(HOp)(EtOH)] présente notamment un gap énergétique de 43.8K et un temps de relaxation de 5x10-4 s<br>Aluminum-based organic semiconductors (OSCs) were systematically synthesized and studied by photophysical and electrochemical methods to identify a relationship between their chemical structure and electronic properties, using Alq3 as benchmark. Experimental HOMO and LUMO were compared to those computed. In addition, newly developed methods were implemented to generate morphologies and calculate charge carrier mobilities. The hole mobility of Al(Op)3 was measured in thin film transistors: 0.6-2.1×10−6 cm2V−1s−1. By photoemission spectroscopy techniques, the Co/Al(Op)3 hybrid interface was probed. Two hybrid interface states (HISs) were unraveled; the SP (spin polarization) of HIS1 is 8% higher than bare cobalt, whereas the SP of HIS2 is 4% lowered. At last, phenalenyl-based dysprosium SMMs (single-molecule magnet) were investigated. [Dy(Op)2Cl(HOp)(EtOH)] showed an energy gap of 43.8K and a quantum relaxation time of 5x10-4s
25
Masavang, Supuksorn. "Sugar reduction in extruded cereal based products : impact of water content on the structure and molecular dynamics in such material." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK025/document.
Full textAbstract:
Les systèmes à base de biopolymères à faible teneur en humidité sont couramment rencontrés dans les aliments. Bien entendu, il est primordial de comprendre les bases physiques de leur qualité: texture, performances dans le temps ou en fonction de leur composition. Le vieillissement physique des systèmes composites rend les changements survenant dans le stockage des produits comestibles difficiles à prévoir. Les objectifs de ce travail étaient d'évaluer l'incidence de la présence de saccharose et de la teneur en eau de fabrication sur les propriétés physico-chimiques du produit fini. La stabilité physique de ces matériaux a été contrôlée grâce à une étude à différentes échelles moléculaires. Ensuite, les relations entre les données multi-échelles ont été examinées. L'effet du saccharose (0 à 20%) et de l'eau d'alimentation (10 et 15%) sur les mélanges d'extrusion a été étudié à l'aide d'un extrudeur double vis conduit dans les mêmes conditions. Les propriétés physiques et microstructurales des produits extrudés expansés ont été examinées sous diverses conditions d'humidité relative. La réduction des teneurs en sucre et en eau d’alimentation a fait augmenter la pression et l’énergie mécanique spécifique, ce qui a réduit la dégradation de l’amidon et augmenté la viscosité dans l’extrudeur en particulier à la teneur en eau la plus élevée. L'augmentation de la pression dans l’extrudeur a entraîné une expansion plus importante des extrudés. Par contre, la technique d'imagerie neutronique montré que le saccharose réduisait la taille des pores, et donc augmentait la densité apparente et ce qui était particulièrement évident en utilisant. Cette technique a été appliquée pour la première fois sur des produits extrudés. Les images de tomographie 2D ont indiqué des différences structurelles internes entre les extrudés à différentes teneurs en saccharose et stockés à humidité relative différente. Toutefois, l'analyse d'images 3D a montré que l'impact de ces facteurs sur la distribution de la taille des pores et le taux de porosité n'était pas significatif. En fin d'extrusion, les échantillons étaient à l'état amorphe à la suite de la gélatinisation de l'amidon et de la fonte du sucre. Leursrs propriétés thermiques ont été analysées par analyse enthalpique différentielle (AED) et les températures e transition vitreuse ont été étudiées. Les thermogrammess d’AED ont été minutieusement étudiés via une déconvolution de la dérivée première de la variation d’enthalpie. Cette approche a mis en évidence que les systèmes composites étudiés présentaient des phases multiples avec des transitions vitreuses distinctes. Ces dernières sont associées à une phase riche en polymère (amidon principalement) et / ou à une phase riche en plastifiant (sucre) dont le comportement dépendait de la teneur en eau de l'échantillon. Les isothermes de sorption ont montré qu’aux faibles Aw et pour une valeur donnée, a la teneur en eau des extrudés diminuait avec l’augmentation des teneurs en saccharose et que l'effet inverse était observé aux aw élevées. L’étude de la cinétique apparente de lala diffusion de l'eau a mis en évidence deux sites de sorption différents. Le premier est caractérisé par une cinétique quasi constante qui pourrait correspondre à un phénomène d'adsorption à la surface. Le second site présente d’abord un ralentissement initial de la cinétique de sorption, tandis qu’une forte augmentation est constatée lorsque la teneur en eau était plus élevée. Ce comportement peut être lié à un effondrement de la structure. Une étude par RMN à cyclage de champ rapide à basse fréquence a montré que les temps de relaxation dépendaient de la teneur en saccharose et en eau. Une carte de stabilité a été tracée pour modéliser les évolutions rhéologiques des matrices avec la teneur en eau en lien avec les transitions de phases des matériaux (...)<br>Low-moisture biopolymer-based systems are commonly encountered in food. Obviously, understanding the physical basis of their quality: e.g texture, or performance over time or as a function of their composition is of primary importance. The objectives of this work were to evaluate how the presence of sucrose and water content affects physico-chemical properties. The physical stability of these materials were monitored through an insight at different molecular scales. Then the relations between the multi-scale studies were investigated. The effect of sucrose (0–20%) and feed water (10 and 15%) on extrusion blends was studied using a twin screw extruder under the same processing settings. The physical and microstructural properties of extruded products were examined at various RH. Reducing both sugar levels and feed water increased die pressure and specific mechanical energy, as a consequence, it reduced starch degradation and increased in viscosity. The effect was more pronounced with increasing feed water content. The increased die pressure resulted in higher expansion of the porous extrudates. Sucrose was shown to increase the bulk density and reduce the pore size, this was particularly evident by using neutron imaging technique. This technique was applied for the first time in extrudate. 2D tomography images indicated internal structural differences between extrudates containing different sucrose content and stored at low and high % RH, while 3D image analysis showed impact of these factors on pore size distribution and % porosity were not significant. The extruded samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with DSC and their Tg were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat low. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a plasticizer-rich phase which behavior depended on the sample water content. Physical aging accompanied with an increase in rigidity at low aw, resulted in an increased bulk density and more pronounced with increasing sucrose content. Sorption isotherms showed the water content of extrudates decreased when product contains high sucrose at low aw range and the inverse effect was observed at high aw. Apparent kinetics of water diffusion showed two different sorption sites, the first kinetics was almost constant and could be adsorption phenomena at the surface. The second one reflected first an initial slowing in dynamics whereas a sharp increase was found at higher water content. Addition of sucrose or water decreased both Tgs in extrudates. Young's modulus showed water acts as anti-plasticizer at low aw, while it shows a plasticizing effect at high aw. A stability map can explain the brittle-ductile transition occurred below Tg. Fast field cycling NMR study at low frequency highlighted that T1 depended on sucrose and water content. T1 and T2 measured using Low field NMR decrease as a function of water content, while the impact pf sucrose were not significant. T2 showing a minimum probably indicating the exchange of protons of water and macromolecules in composite system. The impact of sucrose content was not significant for T1 and for T2 at low water content. FFC NMR showed T1 results consistent with the LF NMR measurement.In conclusion, physicochemical studies of the influence of water and sucrose content on glassy materials showed that the material properties can be investigated at different levels from the macro- to the microscopic scale and these results clearly presented the need for complementary techniques to probe the dynamics in the glassy state of heterogeneous food systems that could be facilitated to manage the stability during storage of this type of dry products
26
Kreouzis, Theodore. "Measurement of photocarrier mobility and range in quasi one dimensional columnar molecular systems." Thesis, Queen Mary, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298247.
Full text
27
Plaza, María Teresa Viciosa. "Molecular mobility of n-ethylene glycol dimethacrylate glass formers upon free radical polymerization." Doctoral thesis, FCT - UNL, 2007. http://hdl.handle.net/10362/1672.
Full textAbstract:
Quando um líquido evita a cristalização durante o arrefecimento, diz-se que
entra no estado sobrearrefecido. Se a temperatura continuar a diminuir, o consequente aumento da viscosidade reflecte-se na mobilidade molecular de tal maneira que os tempos característicos se tornam da mesma ordem de grandeza que os tempos acessíveis experimentalmente. Se o arrefecimento continuar, o líquido altamente viscoso acaba por vitrificar, i.e. entra no estado vítreo onde apenas os movimentos locais são permitidos.
Os monómeros da família n -etileno glicol dimetacrilato ( n -EGDMA, para n = 1 até 4,
que constituem o objecto deste estudo, facilmente evitam a cristalização, sendo pois
bons candidatos para estudar a mobilidade molecular nos estados sobrearrefecido e
vítreo. A Espectroscopia de Relaxação Dieléctrica (DRS) foi a técnica escolhida para obter informação detalhada sobre a sua dinâmica molecular (Capítulos 1 e 2).
A primeira parte deste trabalho consistiu na caracterização dieléctrica dos processos de relaxação existentes acima e abaixo da temperatura de transição vítrea
(g T ), a qual aumenta com o aumento do peso molecular (w M ), sendo este resultado
confirmado por Calorimetria Diferencial de Varrimento (DSC). No que respeita ao processo cooperativo a , associado à transição vítrea, e ao processo secundário b,
observa-se uma dependência com w M , enquanto que o outro processo secundário, g ,
aparenta ser independente deste factor (Capítulo 3).
Nos capítulos seguintes, foram levadas a cabo diferentes estratégias com o objectivo de clarificar os mecanismos que estão na origem destas duas relaxações secundárias (b e g ), assim como conhecer a sua respectiva relação com a relaxação principal (a ).
Do estudo, em tempo real, da polimerização isotérmica via radicais livres do TrEGDMA por Calorimetria de Varrimento Diferencial com Modulação de Temperatura (TMDSC), levado a cabo a temperaturas abaixo da g T do polímero final, concluem-se entre outros, dois importantes aspectos: i) que a vitrificação do polímero em formação conduz a graus de conversão relativamente baixos, e ii) que o monómero que está por reagir é expulso da rede polimérica que se forma, dando lugar a uma clara separação de fases (Capítulo 4). Com base nesta informação, o passo seguinte foi estudar separadamente a polimerização isotérmica do di-, tri- e tetra-EGDMA, dando especial atenção às alterações de mobilidade do monómero ainda por reagir. Com as restrições impostas pela formação de ligações químicas, as relaxações a e b detectadas no monómero tendem a desaparecer no novo polímero formado, enquanto que a relaxação g se mantém quase inalterada. Os diferentes comportamentos que
aparecem durante a polimerização permitiram a atribuição da origem molecular dos
processos secundários: o processo g foi associado ao movimento twisting das unidades
etileno glicol, enquanto que a rotação dos grupos carboxilo foi relacionada com a
relaxação b (Capítulo 5).
No que respeita ao próprio polímero, um processo de relaxação adicional foi
detectado, pol b , no poly-DEGDMA, poly-TrEGDMA e poly-TeEGDMA, com
características similares ao encontrado nos poli(metacrilato de n -alquilo). Este processo foi confirmado e bem caracterizado aquando do estudo da copolimerização do
TrEGDMA com acrilato de metilo (MA) para diferentes composições (Capítulo 6).
Para finalizar, o EGDMA, o elemento mais pequeno da família de monómeros estudada, além de vitrificar apresenta uma marcada tendência para cristalizar quer a partir do estado líquido ou do estado vítreo. Durante a cristalização, a formação de uma fase rígida afecta principalmente o processo a , cuja intensidade diminui sem no entanto se observarem modificações significativas na dependência do tempo de relaxação característico com a temperatura. Por outro lado, o processo secundário b torna-se melhor definido e mais estreito, o que pode ser interpretado em termos de uma maior homogeneidade dos micro-ambientes associados aos movimentos locais(Capítulo 7).
28
Adrjanowicz, Karolina. "The Role of Molecular Mobility in Governing the Physical Stability of Amorphous Pharmaceuticals." Doctoral thesis, Katowice : Uniwersytet Śląski, 2012. http://hdl.handle.net/20.500.12128/5285.
Full textAbstract:
The amorphous state is probably one of the most interesting and curious state of matter.
This confirms large number of futuristic and next-generation materials that turned out to be
partially or completely amorphous. However, physical properties of amorphous solids are
incomprehensible in many aspects. Even the glassy formation is considered as one of the most
important unsolved problems of solid state physics. Understanding what drives supercooled
liquids and glasses towards crystallization is fundamental not only in the context of
unexplained issues of condensed matter physics, but also many practical applications. In this
Ph. D. dissertation I have made an attempt to answer the most important in recent days
questions that relate to molecular dynamics of amorphous materials. The robustness of the
‘universal’ relationships between dynamics and crystallization tendencies of glass-formers
was also uncovered.
The first raised issue concerned dynamical properties of amorphous materials depending on
the preparation method. Collected results for compounds of great pharmaceutical interest,
Telmisartan and antibiotics, remarkably showed that dynamical properties of amorphous
substances prepared using two different amorphization routes (vitrification and cryomilling)
might differ. However, observed discrepancies in molecular dynamics results only from the
fact that during manufacturing they uptake different amount of water from the surroundings,
and this absorbed water has critical influence on their dynamical properties. Particularly
interesting here are results for antibiotics. The presence of y-relaxation, of most probably the
same molecular origin, was reported in anhydrous glassy state of Clarithromycin and
Roxithromycin. In the anhydrous vitrified Azithromycin the lack of y-relaxation was reported,
while in cryomilled amorphous sample this process became suddenly activated due to the
presence of water.
29
French, Jarin C. "Molecular Dynamics Studies of Anisotropy in Grain Boundary Energy and Mobility in UO₂." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/89643.
Full textAbstract:
Nuclear energy is a proven large-scale, emission-free, around-the-clock energy source. As part of improving the nuclear energy efficiency and safety, a significant amount of effort is being expended to understand how the microstructural evolution of nuclear fuels affects the overall fuel performance. Grain growth is an important aspect of microstructural evolution in nuclear fuels because grain size can affect many fuel performance properties. In this work, the anisotropy of grain boundary energy and mobility, which are two important properties for grain growth, is examined for the light water reactor fuel uranium dioxide (UO₂) by molecular dynamics simulations. The dependence of these properties on both misorientation angle and rotation axis is studied. The anisotropy in grain boundary energy is found to be insignificant in UO₂. However, grain boundary mobility shows significant anisotropy. For both 20º and 45º misorientation angles, the anisotropy in grain boundary mobility follows a trend of M₁₁₁>M₁₀₀>M₁₁₀, consistent with previous experimental results of face-centered-cubic metals. Evidences of grain rotation during grain growth are presented. The rotation behavior is found to be very complex: counterclockwise, clockwise, and no rotation are all observed.<br>M.S.<br>Energy needs in the world increase year after year. As part of the effort to address these increasing needs, an increasing effort is needed to study each aspect of energy generation. For energy generated via nuclear fission, i.e., nuclear energy, many things need to be understood to gain maximum efficiency with maximum safety. At the core of a nuclear reactor, transport of energy generated by nuclear fission is heavily dependent on the microscopic structure (microstructure) of the materials being used as fuel. Thus, this work examines the microstructure of the most common nuclear fuel, uranium dioxide (UO₂). The microstructure changes based on at least two properties: grain boundary energy, and grain boundary mobility. This work examines how these properties change based on the orientation of individual crystallites within the polycrystalline material. An additional aspect of microstructural evolution, namely grain rotation, is briefly discussed.
30
Fernandes, Nassar Samira. "Compréhension de la relation entre la microstructure du polylactide, sa mobilité macromoléculaire et ses propriétés barrière pour la création des emballages issus de ressources renouvelables de demain." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLA006/document.
Full textAbstract:
Ces dernières années, une attention particulière a été portée aux polymères biodégradables et biocompatibles, notamment du point de vue écologique. Le développement de biopolymères pour des applications d'emballage alimentaire implique des exigences industrielles spécifiques telles qu’un bas prix ainsi que de bonnes propriétés mécaniques, thermiques et barrières. Le Polylactide (PLA) a attiré beaucoup d’attention car il est produit à partir de ressources naturelles renouvelables, et en raison de sa capacité de mise en œuvre et de ses bonnes propriétés mécaniques. Pour que le PLA puisse être développé à grande échelle pour des applications industrielles dans le domaine de l’emballage, ses propriétés barrières doivent être améliorées. La cristallisation est une méthode très utilisée pour améliorer les propriétés barrières mais n'est pas suffisante dans le cas du PLA. De nouvelles stratégies sont étudiées pour obtenir des effets plus importants. L'une d'entre elles consiste à confiner géométriquement le polymère jusqu’à l’échelle nano en utilisant le procédé de co-extrusion multicouche combiné éventuellement avec un recuit. Cette technologie respecte l'environnement et a déjà prouvé son efficacité pour améliorer les propriétés barrières aux gaz dans le cas d'autres polymères.Cette étude propose d'abord le développement de films PLA avec des structures cristallines différentes dans le but d'optimiser les conditions de cristallisation pour obtenir de meilleures propriétés barrières à l'oxygène. Parmi les différentes structures cristallines obtenues, la perméabilité est la meilleure lorsque le PLA a été cristallisé rapidement à partir de l’état vitreux pour atteindre un degré de cristallinité élevé et un bon découplage de la phase amorphe et cristalline. Ensuite, le PLLA a été confiné par deux polymères amorphes, le Polystyrène et le Polycarbonate. Nous avons montré que le polymère confineur peut influencer la structure cristalline et la mobilité de la phase amorphe du PLLA, influençant ainsi sa perméabilité<br>In recent years, much attention has been focused on biodegradable and biocompatible polymers, particularly from an ecological viewpoint. The development of biopolymers for food-packaging applications implies ecofriendly character to specific industrial requirements as low-cost and good mechanical, thermal and barrier properties. Polylactide (PLA) has been attracting great attention, because it can be obtained from renewable sources, and due to its good process ability and mechanical properties. As one of the major challenges for high performance PLA packaging at a large scale is the improvement of its gas barrier properties, the tailoring of the PLA microstructure. Crystallization is a method used to improve barrier properties but is not sufficient in the case of PLA. New strategies are actually studied to obtained stronger effects. One of them consists in the geometrical confinement of the polymer at the molecular scale using the layer-multiplying co-extrusion process combined eventually with annealing processes to create nanometric thickness layers.This technology is environmentally friendly and has already proved its efficiency to improve the gas barrier properties in case of other polymers. This study first proposes the development of PLA films with different structures crystalline with the aim of optimize the crystallization conditions to get better oxygen barrier properties. Among the different crystalline structures obtained, permeability was better when PLA was rapidly crystallized from glass to reach a high crystallinity degree and decoupling of the amorphous and crystalline phase. Then, PLLA was confined by two amorphous polymers, polystyrene and polycarbonate, and its crystals structure and amorphous mobility was changed. We showed that the confiner polymer could influence PLLA confinement, both in the crystalline phase and in the amorphous phase, thus influencing its permeability
31
Triplett, Gregory Edward Jr. "Process modeling of InAs/AISb materials for high electron mobility transisitors grown by molecular beam epitaxy." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/9458.
Full text
32
Busch, Mark [Verfasser], and Patrick [Akademischer Betreuer] Huber. "Soft condensates in hard confinement : structure and molecular mobility / Mark Busch ; Betreuer: Patrick Huber." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2019. http://d-nb.info/1202990746/34.
Full text
33
Copeman, Kayla. "Evaluating Epoxy Cure And Adhesion Strength Through Single-Sided Nmr Measurements Of Molecular Mobility." W&M ScholarWorks, 2021. https://scholarworks.wm.edu/etd/1627047854.
Full textAbstract:
Commonly used in aerospace, automotive, marine, defense, electronic, and manufacturing industries, epoxy adhesives offer advantages over mechanical joints by providing stronger and/or more flexible bonds, more uniform stress distribution, low shrinkage, and lightweight connections between materials. Determination of curing kinetics and properties of interfaces between epoxy and inorganic substrates provides insight that is useful for quality control and defect detection for such applications. Single-sided NMR provides a nondestructive and inexpensive method for probing epoxy materials and spatially resolving the decay of spin-lattice and spin-spin relaxation times (T1 and T2) during and after curing of epoxy resins onto substrates. In this thesis, we report the use of single-sided NMR for both characterizing the strength of adhesion between epoxy and inorganic substrates and monitoring the cure of epoxy at various temperatures. Multi-dimensional T1 –T2 measurements were performed to correlate with changes in surface energies that provide insight on the chemical adhesion of various epoxy samples. Furthermore, we used NMR measurements to monitor in-situ room-temperature and heat curing of epoxy to probe reductions in molecular mobility throughout the curing process. NMR relaxation properties were correlated with DSC data for comparison of the cure extent and cure rates. Our results show the efficacy of single-sided NMR measurements for studying curing, the extent of cure, adhesion strength of epoxies, and interphase phenomena.
34
Saadat, Abdelkader. "Etude de la mobilite moleculaire du collagene par courants thermostimules : modelisation du vieillissement cutane." Toulouse 3, 1988. http://www.theses.fr/1988TOU30178.
Full text
35
Dutton, Anna Louise. "An investigation into the effects of dystrophin on the lateral mobility of muscle membrane components." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4576/.
Full textAbstract:
Dystrophin is the product of the Duchenne Muscular Dystrophy gene locus, whose absence results in progressive skeletal muscle breakdown. Despite considerable work on the localisation of dystrophin and its associated complex, its role in muscle function remains unclear. In the light of the structural and mechanical instability of the dystrophic membrane, the idea was tested that dystrophin might impart membrane integrity and strength by anchoring membrane proteins and/or delineating the surface into specialised subcellular functional domains. Specifically, because dystrophin shows high sequence, structural and spatial similarities to the cytoskeletal protein spectrin; and because spectrin is proven to sterically restrict protein lateral diffusion through a subplasmalemmal network; the capacity of dystrophin to act as a 'molecular fence' to membrane diffusion was studied by comparing lateral mobility of membrane glycoproteins by fluorescence photobleach recovery in mdx and normal tissue. Secondly, as dystrophin has been proven to interact directly with proteins of the dystrophin associated glycoprotein complex in vivo, experiments addressed whether specific binding and immobilisation of the complex by dystrophin at the membrane was essential for function. Finally, given the homology of dystrophin and spectrin, the presence of dystrophin at the neuromuscular junction, and the importance of spectrins in immobilisation of voltage gated sodium channels in the nervous system, the role of dystrophin in regulating voltage gated sodium channel distribution at the neuromuscular junction was investigated. The results show that membrane glycoproteins were immobile in the presence and absence of dystrophin, suggesting dystrophin is not an essential molecular fence component. Alternatively, viability may have been the major influence on protein and lipid diffusion in these fibres and suggestions are made as to how this may be recognised and overcome for subsequent investigation. Three novel exon specific anti-dystrophin peptide antibodies were generated during the work that will be useful for studies into Duchenne muscular dystrophy in general, and dystrophin revertant fibres in particular.
36
Hellrup, Joel. "Pharmaceutical Nanocomposites : Structure–Mobility–Functionality Relationships in the Amorphous State." Doctoral thesis, Uppsala universitet, Institutionen för farmaci, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-300159.
Full textAbstract:
Amorphous materials are found in pharmaceutical formulations both as excipients and active ingredients. Indeed, these formulations are becoming an essential strategy for incorporating drugs into well-performing solid dosage forms. However, there is an unmet need of better understanding of the microstructure and component interactions in amorphous formulations to be able to design materials with improved functionalities. The aim of this thesis is to give deepened knowledge about structure-mobility-functionality relationships in amorphous for-mulations by studying composites produced from sugars and filler particles. The structure, the mobility, and physical stability of the composite materials were studied using calorimetry, X-ray diffraction, microscopy, spectroscopy, and molecular dynamics simulations. Further, the moisture sorption of the composites was determined with dynamic vapor sorption. The compression mechanics of the composites was evaluated with compression analysis. It was demonstrated that fillers change the overall properties of the amorphous material. Specifically, the physical stability of the composite was by far improved compared to the amorphous sugar alone. This effect was pronounced for formulations with 60 wt% filler content or more. Amorphous lactose that normally recrystallizes within a few minutes upon humidity exposure, could withstand recrystallization for several months at 60% RH in composites with 80 wt% cellulose nanocrystals (CNC) or sodium montmorillonite (Na-MMT). The increased physical stability of the amorphous sugars was related to intra-particle confinement in extra-particle voids formed by the fillers and to immobilization of the amorphous phase at the surface of the fillers. Also, the composite formation led to increased particle hardness for the lactose/CNC and the lactose/Na-MMT nanocomposites. The largest effect on particle hardness was seen with 40-60 wt% nanofiller and could be related to skeleton formation of the nanofillers within the composite particles. The hygroscopicity for the lactose/Na-MMT nanocomposites decreased as much as 47% compared to ideal simple mixtures of the neat components. The nanofillers did not influence the water sorption capacity in the amorphous domains; however, lactose (intercalated into Na-MMT) interacted with the sodium ions in the interlayer space which led to the lowered hygroscopicity of this phase. The thesis advanced the knowledge of the microstructure of amorphous pharmaceutical com-posites and its relationship with pharmaceutical functionalities. It also presented new approaches for stabilizing the amorphous state by using fillers. The concept illustrated here might be used to understand similar phenomena of stabilization of amorphous formulations.
37
Charton, Christophe. "Matrices expérimentales à usage odontologique : formulation, élaboration, caractérisation et leurs influences sur les contraintes de contraction." Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL023N/document.
Full textAbstract:
Les résines composites à base de polymères diméthacrylates sont des biomatériaux fréquemment employés en dentisterie où la matrice est synthétisée in vivo par photopolymérisation en chaîne radicalaire. En Odontologie Conservatrice, la contraction volumique dont cette matrice est le siège au cours de sa synthèse est un inconvénient majeur. Elle est, en effet, à l’origine de contraintes physiques souvent néfastes et mal contrôlées dès lors que le matériau, collé aux murs cavitaires, est élaboré en milieu confiné. Aucune étude n'a permis à ce jour d’analyser de manière approfondie ce phénomène de contraintes de contraction au regard des conditions opératoires de la synthèse de la matrice. Le but de ce travail est donc d'isoler la problématique des contraintes internes en orientant exclusivement l’étude vers l'analyse de la matrice. En élaborant des prototypes à base de Bis-GMA et d’UEDMA et après caractérisation de certaines propriétés physico-chimiques, rhéologiques et thermodynamiques des mélanges de ces comonomères et des copolymères résultants, ce travail a permis de contribuer à une meilleure compréhension de la phénoménologie de la relaxation viscoélastique qui gouverne la dissipation des contraintes de contraction<br>Composite materials containing polymers are biomaterials frequently employed in dentistry where the matrix is synthesized in vivo by photocured radical chain. In Operative Dentistry, the resulting shrinkage strain produced during the synthesis of this matrix is a major disadvantage. It is, indeed, at the origin of often harmful and badly controlled physical stresses since the material, stuck to the cavity walls, is elaborated in confined surroundings. No study to date allowed analyzing thoroughly this phenomenon of contraction taking into consideration the operating conditions of the synthesis of the matrix. The goal of this work is thus to exclusively isolate the set of problems of the internal stresses by directing the study towards the matrix analysis. By elaborating prototypes based on Bis-GMA and UEDMA and after characterization of certain physicochemical, rheological and thermodynamic properties of mixtures of these comonomers and of the resulting copolymers, this work made it possible to contribute to a better understanding of the phenomenology of the viscoelastic relaxation which governs the dissipation of the shrinkage stress
38
Ensor, V. M. "the molecular epidemiology and genetic mobility of the blaCTX-M extended spectrum beta-lactamase genes." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.743413.
Full text
39
Triplett, Gregory Edward. "Process modeling of InAs/AISb materials for high electron mobility transisitors grown by molecular beam epitaxy." Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131359/unrestricted/triplett%5Fgregory%5Fe%5F200405%5Fphd.pdf.
Full text
40
Young, Lydia Mary. "Defining the mechanism of small molecule inhibition of amyloid fibril formation using ion mobility spectrometry-mass spectrometry." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11887/.
Full textAbstract:
The study of protein/peptide folding, misfolding, structure, and interactions are vital to understanding complex biological problems. The work presented in this thesis describes the development and application of mass spectrometry -based techniques to investigate protein structure, aggregation and interference with aggregation, providing insights into the self-assembly and inhibition of several disease-related peptides. Mass spectrometry has evolved significantly over the past decade, its applications varying from small molecules to macromolecules. Travelling wave ion mobility spectrometry (TWIMS), when combined with mass spectrometry (MS), has the unique and unrivalled capability of separating molecular ions based on their collision cross-sectional area in addition to their mass-to-charge ratio, thus facilitating structural studies of co-populated protein conformations and structural isomers of protein complexes that cannot be separated by molecular weight alone. One biological system that has benefitted enormously from such advances is the study of in vitro amyloid formation. The ability of amyloidogenic protein/peptides to assemble into insoluble fibrils is the basis of a vast array of human disorders. Human islet amyloid polypeptide (hIAPP) is one such peptide able to readily assemble into amyloid fibrils in vitro at neutral pH, despite being intrinsically disordered. Identifying oligomeric states occupied between monomer and final fibrils creates an enormous challenge, given that few techniques are able to separate and characterise such lowly-populated and transient species. In addition to characterisation of fibril precursors, recent research has focussed on the identification of small molecule inhibitors of the amyloid cascade and understanding their mechanism of action is of great interest to this field. In the work presented here, the power of TWIMS-MS has been harnessed to achieve the separation and characterisation of oligomeric precursors of the type-2 diabetes-related peptide hIAPP along with IAPP mutants and peptides corresponding to its core sequence. In addition, the effects of small molecule inhibitors on oligomer population and fibril formation have been studied and described in detail. Further, an experimentally simple, in vitro MS-based screen has been developed and implemented that provides rapid and accurate analysis of protein aggregation and its inhibition. All of the results highlight the powers of MS to provide important insights into the mechanism of amyloid formation and demonstrate the potential of this approach for screening for novel inhibitors of disease-related amyloid assembly.
41
Wagner, Sasha. "Black Carbon: Sources, Mobility and Fate in Freshwater Systems." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2213.
Full textAbstract:
Black carbon (BC) is a complex mixture of polycondensed aromatic compounds produced by the incomplete combustion of biomass during events such as wildfires and the burning of fossil fuels. Black carbon was initially considered to be a refractory form of organic matter. However, recent studies have shown that BC can be quite mobile and reactive in the terrestrial environment. Black carbon can be translocated from soils and sediments in the form of dissolved BC (DBC). A global correlation between DBC and bulk dissolved organic carbon (DOC) has been established for fluvial systems where DBC comprises approximately 10% of the total DOC pool, which suggests that DBC may be a significant contributor to the global carbon cycle.
The primary objective of this thesis was to further characterize DBC and elucidate some of the specific physical and chemical processes that promote its transfer to the aqueous phase and drive the DBC-DOC relationship. The molecular composition and qualitative distribution of DBC was assessed using Fourier transform ion cyclotron resonance mass spectrometry. Black carbon in both dissolved and particulate (PBC) phases was quantified by the benzenepolycarboxylic acid method. Dissolved BC was found to contain considerable amounts of nitrogen and the export of this dissolved black nitrogen was linked to watershed land use in global rivers. The riverine flux of PBC, a previously unstudied BC removal mechanism, was significantly increased by local wildfire activity. However in-stream DBC did not appear to be affected by short-term fire events. Once translocated to surface waters, DBC is susceptible to photodegradative processes. Dissolved BC in high molecular weight DOC fractions was more photoreactive than DBC associated with lower molecular weight fractions.
In the coming decades, wildfire frequency is expected to increase with climate change and natural lands will continue to be altered for anthropogenic use. These processes have already been shown to significantly impact the composition of DOC and associated DBC exported to inland waters. The quality of DBC influences its stability in soil and resistance to degradation. Therefore, it is essential that we aim to fully understand DBC dynamics in natural systems in order to assess its contribution to global carbon cycling.
42
Million, Passe Christina M. "Role and regulation of the high mobility group protein p8 in gonadotrope development, function, and tumorigenesis." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3330816.
Full textAbstract:
Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2008.<br>Title from PDF t.p. (viewed on Jul 23, 2009). Source: Dissertation Abstracts International, Volume: 69-10, Section: B, page: 5924. Adviser: Christine Quirk.
43
Alsharaeh, Edreese Housni. "Gas Phase Studies of Molecular Clusters Containing Metal Cations, and the Ion Mobility of Styrene Oligomers." VCU Scholars Compass, 2004. http://scholarscompass.vcu.edu/etd/1200.
Full textAbstract:
This study is divided into three parts. Part I deals with the mechanism of the self-initiated polymerization (or thermal polymerization) of styrene in the gas phase. In this work, we present the first direct evidence for the thermally self-initiated polymerization of styrene in the gas phase. Our approach is based on on-line analysis of the gas phase Oligomers by mass-selected ion mobility. The mobility measurements provide structural information on the ionized oligomers based on their collision cross-sections (Ω) which depend on the geometric shapes of the ions. Theoretical calculations of possible structural candidates of the Oligomers ions are then used to compute angle averaged Ω for comparison with the measured ones. The agreement between the measured and calculated Ω of the candidate structures provides reliable assignments to the structures of the oligomers. Furthermore, collisional-induced dissociations of the mass-selected oligomer ions provide further support for the structures obtained from the mobility measurements. Our results indicate that the gas phase polymerization of styrene proceeds via essentially the same initiation mechanism (the Mayo mechanism) as in condensed phase polymerization. The structural evidence, the mechanism of formation and the observed fragmentation pathway of the growing dimers and trimers in the gas phase are presentedIn Part II the solvation of a variety of metal cations by benzene clusters have been studied using laser vaporization, cluster beam and time-of-flight mass spectrometry techniques. In this work strong magic numbers were observed for clusters containing 10, 13 and 14 benzene molecules depending on the nature of the metal cation involved. The metal cations exhibiting preference solvation by 14 benzene molecules show a strong tendency to form sandwich structures with two benzene molecules. The interpretation of these results in view of the proposed structures and the growth patterns of the clusters are presented. In Part III, the work is focused on the investigation of the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile).
44
Sebastian, Ahlberg. "A Monte Carlo study of the particle mobility in crowded nearly one-dimensional systems." Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-92769.
Full textAbstract:
The study of crowding effects on particle diffusion is a large subject with implications in many scientific areas. The studies span from pure theoretical calculations to experiments actually measuring the movement of proteins diffusing in a cell. Even though the subject is important and has been studied heavily there are still aspects not fully understood. This report describes a Monte Carlo simulation approach (Gillespie algorithm) to study the effects of crowding on particle diffusion in a quasi one-dimensional system. With quasi meaning that the particles diffuses on a one-dimensional lattice but has the possibility to disassociate from the lattice and then rebind at a latter stage. Different binding strategies are considered: rebinding to the same location and randomly choosing the binding location. The focus of the study is how these strategies affects the mobility (diffusion coefficient) of a tracer particle. The main result of this thesis is a graph showing the diffusion coefficient as a function of the binding rate for different binding strategies and particle densities. We provide analytical estimates for the diffusion coefficient in the unbinding rate limits which show good agreement with the simulations.<br>Hur "trängsel" (från engelskans "crowding" t ex molecular crowding) påverkar diffusionsprocesser är viktigt inom många olika vetenskapliga områden. Forskningen som för tillfället utförs sträcker sig från rent teoretiska beräkningar till experiments där man kan följa enskilda proteiners rörelse i en cell. Även fast ämnet är viktig och väl undersökt finns det fortfarande många aspekter som man inte förstår till fullo. I det här examensarbetet beskrivs en Monte Carlo metod (Gillespie algoritmen) för att studera hur trängsel påverkar en partikel som diffunderar i ett "nästan" en-dimensonellt system. Det är nästan en-dimensionellt i det avsedde att partiklarna diffunderar på ett gitter men kan binda av från gittret och binda tillbaka i ett senare skedde. Olika metoder för hur partiklarna binder till gittret undersöks: Återbinding till avbindingsplatsen och slumpmässigt vald återbindingsplats. Fokus ligger på att förklara hur dessa påverkar mobiliteten (diffusionskonstanten) av en spårningspartikel (tracer particle). Resultatet är en graf som visar diffusionskonstanten för spårningspartikeln som en funktion av avbindingsfrekvens för olika bindingstrategier och partikeldensiteter. Vi ger också analytiska resultat i gränsvärdet för höga och låga avbindingstakter vilka stämmer bra överens med simuleringar.
45
Constantinidès-Mégret, Colette. "Etude de la structure physique de l'elastine par spectroscopies thermostimulees (aed, cts)." Toulouse 3, 1988. http://www.theses.fr/1988TOU30128.
Full text
46
Redondo, Foj María Belén. "A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/59457.
Full textAbstract:
[EN] The development of new and more complex polymeric materials involves challenging problems to basic sciences. The relationship between structure and molecular dynamics assumes great importance for the future development of novel technologies based on such polymers. Thus, the understanding of how small changes in the chemical structure affect the properties of the material is essential to progress in the technological and scientific area. An in-depth analysis of the molecular mobility leads to establish the structure-properties relationships. On this basis, the main aim of the present work is to study the molecular mobility of two different families of polymeric materials. For this purpose, the experimental techniques mainly used were Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS).
The first family of polymers characterized was a series of chemically cross-linked copolymers composed by Vinylpyrrolidone (VP) and Butyl Acrylate (BA) monomers.
In the first place, the influence of the monomer molar ratio (XVP/YBA) on the copolymer properties was studied. Thus, a Fourier Transform Infrared Spectroscopy (FTIR) analysis verified dipole-dipole interactions between amide groups. The influence of these interactions on several parameters related to the molecular mobility was evidenced by the DSC, DRS and Dynamic Mechanical Analysis (DMA) techniques. Secondly, the effect of the cross-link density on the molecular dynamics of 60VP/40BA copolymers was analyzed using DSC and DRS. One single glass transition was detected by DSC measurements. The DRS analysis showed that an increase of the cross-linking produced a typical effect on the alpha process dynamics. However, the beta process, which possessed typical features of pure JG relaxation, unexpectedly lost the intermolecular character for the highest cross-linker content. The fastest gamma process was relatively unaffected.
The second family of polymeric materials studied was a series of segmented polycarbonatediol polyurethane (PUPH) modified with different amounts of expanded graphite (EG) conductive filler. Scanning Electron Microscopy (SEM), X-ray diffraction measurements and FTIR analysis demonstrated a homogeneous dispersion of the EG filler in the matrix. DRS was used to study the dielectric properties of the PUPH/EG composites. The dielectric permittivity of the composites showed an insulator to conductor percolation transition with the increase of the EG content (2030 wt%). The addition of expanded graphite to the matrix caused a dramatic increase in the electrical conductivity of ten orders of magnitude, which is an indication of percolative behavior.<br>[ES] El desarrollo de nuevos materiales poliméricos de mayor complejidad produce un desafío cada vez mayor en el área de las ciencias básicas. La relación entre la estructura y la dinámica molecular resulta de gran importancia para el desarrollo de nuevas tecnologías basadas en estos materiales poliméricos. Así, una mayor comprensión de cómo pequeños cambios en la estructura química afectan a las propiedades de los materiales resulta esencial para el progreso científico y tecnológico. Un análisis en profundidad de la movilidad molecular permite establecer las relaciones estructura-propiedades. Partiendo de esta base, el principal objetivo del presente trabajo es el estudio de la movilidad molecular de dos familias diferentes de materiales poliméricos. Para ello, las técnicas experimentales utilizadas fueron principalmente la Calorimetría Diferencial de Barrido (DSC) y la Espectroscopia de Relajación Dieléctrica (DRS).
La primera familia de polímeros caracterizada fue una serie de copolímeros entrecruzados químicamente compuestos por los monómeros Vinilpirrolidona (VP) y Acrilato de Butilo (BA).
En primer lugar, se estudió la influencia de la proporción molar de monómero (XVP/YBA) en las propiedades del copolímero. A través de un análisis por Espectroscopia de Infrarrojo por Transformada de Fourier (FTIR), se verificó la existencia de interacciones dipolo-dipolo entre los grupos amida. Mediante el análisis por DSC, DRS y Análisis Dinamomecánico (DMA), se evidenció la influencia de estas interacciones en diferentes parámetros relacionados con la movilidad molecular.
En segundo lugar, se analizó el efecto de la densidad de entrecruzamiento en la dinámica molecular de los copolímeros 60VP/40BA usando DSC y DRS. A través de las medidas de DSC se observó una única transición vítrea para todos los entrecruzamientos. El análisis por DRS mostró como el incremento en entrecruzante produjo el típico efecto en la dinámica del proceso alpha, pero sin embargo, el proceso beta, que tenía las características típicas de una relajación JG, perdió de forma inesperada su carácter intermolecular para el mayor contenido en entrecruzante. El proceso gamma no se vio afectado.
La segunda familia de materiales poliméricos estudiada fue una serie de poliuretanos segmentados (PUPH) modificados con diferentes cantidades de grafito expandido (EG), utilizado como relleno conductivo (desde 0 a 50% en peso). El análisis de los resultados obtenidos mediante Microscopía Electrónica de Barrido (SEM), Difracción de Rayos X y FTIR demostró la homogénea dispersión del relleno de EG en la matriz de PUPH. La técnica DRS se usó para estudiar las propiedades dieléctricas de los materiales compuestos PUPH/EG. La permitividad dieléctrica de los materiales mostró una transición de percolación desde aislante a conductor al incrementarse el contenido en EG (rango de 20-30% en peso). La adición de grafito expandido a la matriz de PUPH causó un incremento significativo en la conductividad dieléctrica de diez órdenes de magnitud, lo que indica el comportamiento de percolación.<br>[CAT] El desenvolupament de nous materials polimèrics de major complexitat produeix un desafiament cada vegada major en l'àrea de les ciències bàsiques. La relació entre l'estructura i la dinàmica molecular resulta de gran importància per al desenrotllament de noves tecnologies basades en aquests materials polimèrics. Així, una major comprensió de com petits canvis en l'estructura química afecten a les propietats dels materials, resulta essencial per al progrés científic i tecnològic. Un anàlisis en profunditat de la mobilitat molecular permet establir les relacions estructura-propietats. Partint d'aquesta base, el principal objectiu del present treball és l'estudi de la mobilitat molecular de dues famílies diferents de materials polimèrics. Per a això, les tècniques experimentals utilitzades van ser principalment la Calorimetria Diferencial de Rastreig (DSC) i l'Espectroscòpia de Relaxació Dielèctrica (DRS).
La primera família de polímers caracteritzada va ser una sèrie de copolímers entrecreuats químicament compostos pels monòmers Vinilpirrolidona (VP) i Acrilat de Butilo (BA) .
En primer lloc, es va estudiar la influència de la proporció molar de monòmer (XVP/YBA) en les propietats del copolímer. A través d'una anàlisi per Espectroscòpia d'Infraroig per Transformada de Fourier (FTIR), es va verificar l'existència d'interaccions dipol-dipol entre els grups amida. Mitjançant l'anàlisi per DSC, DRS i Anàlisi Dinamomecánico (DMA), es va evidenciar la influència d'aquestes interaccions en diferents paràmetres relacionats amb la mobilitat molecular.
En segon lloc, es va analitzar l'efecte de la densitat d'entrecreuament en la dinàmica molecular dels copolímers 60VP/40BA mitjançant DSC i DRS. A través de les mesures de DSC es va observar una única transició vítria per a tots els continguts d'agent entrecreuant . L'anàlisi per DRS va mostrar com l'increment en agent entrecreuant va produir l'efecte esperat en la dinàmica del procés alfa. En canvi, el procés beta, que tenia les característiques típiques d'una relaxació JG, va perdre de forma inesperada el seu caràcter intermolecular per al major contingut en agent entrecreuant. El procés més ràpid gamma no es va veure afectat.
La segona família de materials polimèrics estudiada va ser una sèrie de poliuretans segmentats (PUPH) modificats amb diferents quantitats de grafit expandit (EG) , utilitzat com a farcit conductiu (des de 0 a 50% en pes). L'anàlisi dels resultats obtinguts per mitjà de Microscòpia Electrònica de Rastreig (SEM), Difracció de Rajos X i FTIR va mostrar la dispersió homogènia del EG en la matriu de PUPH. La tècnica DRS es va utilitzar per a estudiar les propietats dielèctriques dels materials compostos PUPH/EG. La permitivitat dielèctrica dels materials va mostrar una transició de percolació des d'aïllant a conductor amb l'increment de contingut en EG (20-30% en pes). L'addició d'EG a la matriu de PUPH va causar un increment significatiu en la conductivitat dielèctrica, de deu ordes de magnitud.<br>Redondo Foj, MB. (2015). A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59457<br>TESIS
47
Nikaj, Erisela. "Mobilité moléculaire aux interfaces de systèmes nanostructurés." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10255.
Full textAbstract:
Ce travail a consisté en l’étude par Spectroscopie Diélectrique de la mobilité moléculaire dans trois systèmes nanostructurés et confinés à base de polymère. La dynamique moléculaire des films de copolymères greffés à base d’Acétate de Cellulose (chaîne principale, peu mobile) et de poly(méthyl (diéthylène glycol) méthacrylate) (chaîne greffée, très mobile) a été analysée. Nous avons dans ce cas, observé une augmentation de la mobilité de la chaîne principale et une réduction de la mobilité des greffons. Ensuite nous avons mis en évidence les effets de confinement induits par la phase cristalline sur la phase amorphe des films de Poly(éthylène naphtalène - 2,6 - dicarboxylate) (PEN) cristallisés à différents temps et températures de cristallisation, en fonction de la morphologie des matériaux. Une forte influence de la température de cristallisation sur la dynamique moléculaire du PEN a pu être observée : la mobilité des chaînes dans le cas des échantillons cristallisés aux hautes températures de cristallisation s’est révélée être plus élevée que celle des échantillons cristallisés aux basses températures. Le troisième système choisi consiste en des nanocomposites à base de Polyamide 6 (PA6) et de Montmorillonite (MMT) ont été les derniers matériaux étudiés. Aucune influence significative des feuillets de MMT sur la mobilité des chaînes de PA6 n’a été observée dans ces systèmes. Cependant, les deux relaxations interfaciales observées sont très sensibles au taux de charge<br>The aim of this work was to study the molecular dynamics in several polymeric nanostructured and confined systems. Thus, by means of Dielectric Spectroscopy, the molecular mobility of cellulose acetate (rigid chain) grafted poly(methyl (diethylène glycol) methacrylate) (very mobile chains) copolymers were studied. In this case, an increase of the mobility of the main chain and a reduction of the mobility of the grafted moieties have been observed. The confinement effects induced by the presence of the crystalline lamellae on the mobility of the chains belonging to the amorphous region, was also studied as a function of the morphology, in the case of the amorphous films of Poly(ethylene naphtalene - 2,6 - dicarboxylate) (PEN) which were crystallized at different crystallization temperatures during different crystallization times. A strong influence of the crystallization temperature on the molecular dynamics of PEN has been evidenced: in the case of the samples crystallized at high temperatures, the mobility of the chains was higher than in the case of the samples crystallized at low temperatures. Finally, the confinement effects induced by the Montmorillonite (MMT) platelets on the Polyamide 6 (PA6) matrix were studied in the PA6/MMT nanocomposites. No significant influence of the filler on the molecular mobility of the PA6 chains was observed. Nevertheless, as expected, the two interfacial relaxations were very sensitive to the filler content
48
Sawyer, Holly Ann. "Investigation of the effect of intra-molecular interactions on the gas-phase conformation of peptides as probed by ion mobility-mass spectrometry, gas-phase hydrogen/deuterium exchange, and molecular mechanics." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3093.
Full textAbstract:
Ion mobility-mass spectrometry (IM-MS), gas-phase hydrogen/deuterium (H/D) exchange ion molecule reactions and molecular modeling provide complimentary information and are used here for the characterization of peptide ion structure, including fine structure detail (i.e., cation-π interactions, β-turns, and charge solvation interactions). IM-MS experiments performed on tyrosine containing tripeptides show that the collision cross-sections of sodiated, potassiated and doubly sodiated species of gly-gly-tyr are smaller than that of the protonated species, while the cesiated and doubly cesiated species are larger. Conversely, all of the alkali-adducted species of try-gly-gly have collision cross-sections that are larger than that of the protonated species. The protonated and alkali metal ion adducted (Na+, K+ and Cs+) species of bradykinin and bradykinin fragments 1-5, 1-6, 1-7, 1-8, 2-7, 5-9 and 2-9 were also studied using IM-MS and the alkali metal ion adducts of these species were found to have cross-sections very close to those of the protonated species. Additionally, multiple peak features observed in the ATDs of protonated bradykinin fragments 1-5, 1-6 and 1-7 are conserved upon alkali metal ion adduction. It was observed from gas-phase H/D ion molecule reactions that alkali adducted species exchange slower and to a lesser extent than protonated species in the tyrosine- and arginine-containing peptides. Experimental and computational results are discussed in terms of peptide ion structure, specifically the intra-molecular interactions present how those interactions change upon alkali salt adduction, as well as with the sequence of the peptide.
Additionally, IM-MS data suggests the presence of a compact conformation of bradykinin fragment 1-5 (RPPGF) when starting from organic solvent conditions. As water is added stepwise to methanolic solutions, a more extended conformation is populated. When the starting solution is composed of ≈90% water, two distinct mobility profiles are observed as well as a shoulder, indicating the presence of three gas-phase conformations for RPPGF. Gas-phase H/D exchange of [M+H]+ ions prepared from aqueous solvents show a bi-exponential decay, whereas samples prepared from organic solvents show a single exponential decay. The effect of solvent on gas-phase peptide ion structure, i.e., solution-phase memory effects, is discussed and gas-phase structures are compared to know solution-phase structures.
49
Manoella, de Souza Lima Gláucia. "Ocorrencia de bacteriocinas e caracterizacao molecular de linhagens de Zymomonas mobilis." Universidade Federal de Pernambuco, 2002. https://repositorio.ufpe.br/handle/123456789/1295.
Full textAbstract:
Made available in DSpace on 2014-06-12T15:48:52Z (GMT). No. of bitstreams: 2
arquivo4384_1.pdf: 698040 bytes, checksum: a2b800bfa7c3059293b11eb6eda9e1fa (MD5)
license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5)
Previous issue date: 2002<br>O fermentado de Zymomonas mobilis tem apresentado diversas aplicações
terapêuticas contra várias infecções bacterianas. Diante desse fato, o presente trabalho
teve como objetivo relacionar a ação terapêutica de Z. mobilis com a produção de
bacteriocina além de caracterizar as linhagens através de SDS-PAGE, RAPD e rep-PCR.
Para verificar a ocorrência de bacteriocina, foram testadas 6 linhagens de Zymomonas
mobilis (CP4, Z1-86A, Z1-86B, Z1-87, Z1-88 e Z2-88) contra as linhagens Escherichia coli
K12, E. coli BH57, E. coli ATCC 9637, Salmonella enteritidis, Staphylococcus aureus e
Streptococcus faecalis. Os resultados obtidos mostram que todas as linhagens de
Zymomonas produzem bacteriocina, exibindo um amplo espectro de ação. Os perfis de
atividade antimicrobiana mostraram diferenças significativas em relação ao
heteroantagonismo. Foi avaliada também a influência do meio de cultura (SSDL e
Schreder) e temperatura (30ºC e 37ºC) na expressão da atividade antagonista produzida
pela Z. mobilis. Os dois meios foram eficientes para produção de bacteriocina, porém foi
observada melhor atividade bacteriocinogênica para a linhagem Z1-87 no meio Schreder
a 37ºC. As bacteriocinas permaneceram estáveis até 80ºC por 15 minutos e foram
inativadas pela proteinase K. Não foram observados bacteriófagos e ácidos atuando como
prováveis inibidores de crescimento. A cinética da produção de bacteriocina da linhagem
Z1-87 no meio Schreder revelou que a produção iniciou na fase logarítmica e se
estabilizou na fase estacionária. A análise eletroforética de proteínas totais não foi eficaz
para a caracterização genética das linhagens de Z. mobilis. Com a técnica de RAPD
foram selecionados sete primers os quais originaram 47 bandas, sendo possível
evidenciar o polimorfismo entre as linhagens. O rep-PCR foi bastante sensível para
detectar diferenças genéticas entre as linhagens, utilizando os primers ERIC e REP. As
linhagens apresentaram um nível de similaridade em torno de 62%
50
Friedman, Ross Aaron. "The dehydration of pharmaceutical hydrates under mechanical load." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/3224.
Full textAbstract:
Nearly one-third of all pharmaceutical substances on the market are able to sorb water into their crystal lattices to form hydrates, which can often compromise stability during processing and/or storage[1]. The tendency of a hydrate to lose its water of crystallization during the manufacturing process of tablet compression is of particular concern to formulation scientists. The amount of water freed as a function of increasing compaction pressure can be explained by the mobility of water within the compact. The mobility of water is determined by the size and shape of the crystal lattice, the numbers and strengths of the hydrogen bonds, and the presence of high-energy sites of disorder[2]. Due to their differing crystal structures, theophylline monohydrate (THM), citric acid monohydrate (CAM), theophylline-water-citric acid cocrystal hydrate (CATHP hydrate), and dicalcium phosphate dihydrate (DCPD) make for interesting model systems to examine the dehydration under mechanical load.
The thermal dehydration of both powders and tablets was carried out via thermal gravimetric analysis (TGA). By comparing the temperatures required to start removal of water loss from the powder to that of the tablet, the average amount of water of crystallization that is freed by the compaction process may be quantified. The average amount of water freed by the compaction process results from a competition between the mechanically-induced disorder of the crystal structure that increases the molecular mobility of water within the tablets, and the trapping of water within the interparticulate void spaces at high compaction pressures.
The compressibilities, compactabilities, and tabletabilities of the materials were calculated as a function of increasing compaction pressure. The consolidation of the powder bed under pressure was modeled by out-of-die Heckel Analysis which demonstrated the ease of deformation of the model compounds. XRD was utilized to show the decrease in overall order of the crystal lattice as a result of compression as well as anisotropy within the tablets. Crystallographic approaches were utilized to demonstrate the compactness of the crystal structure, and how it affects water mobility.
Relaxation pulse experiments (T1, T2) utilizing solid-state NMR were used to directly probe the mobilities of the water molecules within the crystal lattice of THM. The results from T1 and T2 relaxation experiments directly measure the change in molecular mobility of water within the tablets as a function of compaction pressure. This provided independent verification of the trends in molecular mobility and average water freed as a function of compaction pressure observed during TGA dehydration. Raman spectroscopy was used to indirectly measure the polarizability and vibrational motions of THM, and these results corroborate those obtained from ssNMR and TGA dehydration experiments. Overall, this work highlights the potential impact that tablet compression can have on API hydrate stability.
1. Hilfiker R (editor). 2006. Polymorphism in the Pharmaceutical Industry. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co, KGaA.
2. Byrn SR, Pfeiffer RR, Stowell JG. 1999. Solid-state chemistry of drugs. SSCI, Inc.