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1
Zeng, Yong. "Optical properties of active photonic materials". Doctoral thesis, Stockholm : Bioteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4497.
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Baumann, Martin J. "Xyloglucan-active enzymes : properties, structures and applications". Doctoral thesis, Stockholm : Bioteknologi, KTH, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4314.
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Omiccioli, Nicola. "Evaluation of antioxidant properties of new active polymers". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Active packaging by radical scavenging of the free radical species involved in the biochemical degradation of food is an innovative way to extend the shelf-life of a food product. Current drivers such as consumer’s demand for safer, “healthier,” and higher-quality foods have led to the development of new packaging materials which contain natural extracts. This kind of materials could act as free radical scavengers and thus permit to avoid the use of synthetic and dangerous for the human health antioxidant.
In this work, multilayer polymeric materials of different types containing natural extracts of ginger, rosemary and green tea available in the market have been produced and tested. Production was carried out using technologies that could be compatible with the processes used at industrial level. For the test, the scavenging power of the materials was evaluated analysing the quantity of scavenged radicals from a gaseous stream containing in situ produced •OH radicals.
The antioxidant power was also evaluated measuring the degradation rate in samples of fried potato chips packed with the materials produced by carrying out TBARs (thiobarbituric acid reaction system) assay.
Finally, with the available data, an analysis of the compositions of the materials before and after the oxidation due to the absorbed •OH radicals was carried out, to understand which compounds, belonging to the natural extracts, was responsible of the observed scavenger action.
4
Raimundo, Sandra Isabel de Jesus. "Measuring the physical properties of active galactic nuclei". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609908.
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Huang, Caijin. "Optical nano-antennas : passive properties and active control". Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS011/document.
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Les nano-antennes optiques sont de nouveaux éléments, généralement métalliques, permettant d’améliorer les interactions électromagnétiques entre le rayonnement lumineux et un objet sub-longueur d’onde. Ces dispositifs innovants, fonctionnant dans une gamme de longueur d’onde correspondant au spectre visible et proche infrarouge, répondent à certaines contraintes inhérentes à l’optique lorsque les échelles d’interactions relèvent du nanomètre. En particulier, les propriétés des antennes optiques métalliques sont régies par l’apparition de résonances plasmons qui permettent, d’une part de confiner le champ électromagnétique dans des volumes très inférieurs aux limites imposées par la diffraction, et d’autre part d’exalter fortement les processus optiques à faibles sections efficaces. L’objectif de cette thèse est de comprendre par l’expérience quels sont les paramètres clés qui caractérisent une nano-antenne optique afin d’en contrôler son fonctionnement. Ces paramètres ont été accessibles expérimentalement grâce au développement d’une microscopie adaptée basée sur une illumination diascopique à faible ouverture numérique avec soit une détection coronographique confocale ou conoscopique. Cet appareillage nous a permis de mesurer la capacité d’une antenne optique unique à diffuser un rayonnement lumineux. Les études ont débutées avec des systèmes modèles simples (nanoparticules) pour évoluer vers des antennes couplées (dimères). Par analogie avec le domaine radiofréquences, les paramètres importants d’une antenne optique que sont la plage fréquentielle, le désaccord, le gain et le diagramme de rayonnement ont été définis et mesurés. L’influence des caractéristiques morphologiques de l’antenne sur ces paramètres a complété l’étude. Toujours par comparaison avec les antennes radiofréquences, nous avons introduit le concept de tuner optique. Le principe est de modifier la réponse optique de la charge de l’antenne, c’est-à-dire le milieu dans lequel elle émet son rayonnement. Dans ce but, nous avons utilisé un milieu anisotrope composé des molécules de cristal liquide dont l’orientation de l’ellipsoïde des indices peut être commandée par un champ électrostatique. Le fonctionnement du tuner, c’est-à-dire l’accord de l’antenne à une fréquence de travail, a été démontré pour des antennes optiques coupléesOptical nanoantennas are a new class of optical devices, generally constituted of metal nanoparticles, used for enhancing the interaction between an electromagnetic wave and a nano-scale object. These components are operating in the visible to near infra-red part of the spectrum and are offering solutions for the inherent limitations of optics at the nanometer scale. In particular, the properties of optical antennas are governed by the surface plasmon resonances of the underlying structure. These resonances are associated with a large field confinement, beyond the diffraction limit, and an enhancement of the local electromagnetic response that is used to amplify weak optical processes. The objective of this doctoral thesis is to understand by an experimental approach what are the key parameters characterizing an optical antenna with the aim to control its operation. Through the development of an original microscopy based on a low numerical aperture diascopic illumination and a subsequent spatial filtering, the scattering characteristics of a single optical nano-antenna were successfully measured. Our approach was first tested with simple model antennas (nanoparticles) before investigating multi-element coupled antennas (dimers). In analogy to radiofrequency theory, we have defined and measured important antenna characteristics: operating frequency, detuning factor, gain and emission diagram. We have studied the influence of the morphology of the antenna on these characteristics. Continuing the comparison with microwave antennas, we have introduced the concept of an optical tuner. The operating principle is to modify the medium in which the antenna is emitting its radiation i.e. the load of the device. To this aim, we have employed anisotropic liquid crystal molecules. With this load medium, the orientation of the anisotropy can be controlled by a static electric field. The operation of the optical tuner, i.e. tuning of the antenna to a broadcasting frequency, is demonstrated for electromagnetically coupled antennas
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Nilsson, Frederik. "Alkylglucosides physical-chemical properties /". Lund : Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39761789.html.
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Chaudhary, Pooja. "Properties of the integrated spectrum of active galactic nuclei". Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-137908.
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DeBoo, Brian J. "Investigation of polarization scatter properties using active imaging polarimetry". Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280600.
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This work investigates complete Mueller matrix polarization signatures in scattered light. A number of samples are studied using Mueller matrix imaging polarimetry, where samples are actively illuminated with a sequence of known polarization states. The capabilities of the Mueller matrix imaging polarimeter for scatter measurements are explored. Measuring polarization properties in scattered light from targets is important in remote sensing because polarization offers additional information unavailable from intensity measurements alone. Polarization helps discriminate surface features or material properties. The Mueller matrix contains detailed polarization and depolarization information possible for scattering objects, and every Mueller element conveys polarization coupling information. Polarization signatures are obtained at a number of different illumination and scatter angles, and a Mueller matrix bidirectional reflectance distribution function (MBRDF) in one dimension is used to compare various targets. Polarization metrics including diattenuation, retardance, and depolarization obtained from Mueller matrix data images provide methods for comparison, classification, and discrimination of targets. This work examines these reduced polarization parameters and how they vary as a function of scattering geometry, in order to determine which polarization signatures are the best discriminants for remote sensing or metrology. The Mueller matrix bidirectional reflectance distribution function, diattenuation, retardance, and depolarization properties are studied for a diverse group of manmade samples. A group of leaf samples is also studied, to see how natural samples behave and to compare natural and manmade samples. The most prevalent and useful discriminants for scattering samples appear in the depolarization data. Although this is not unexpected, these depolarization properties have not been studied in detail before and are not well described in the literature. Most depolarizing samples investigated showed an inverted Gaussian profile of depolarization magnitude versus scatter angle, with minimum depolarization for specular reflection which increases asymptotically as the scatter angle changes. Other patterns are found in the more noisy diattenuation and retardance data.
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Burkitt, S. J. "Properties of flurocarbon and hydrocarbon surface active agent mixtures". Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375002.
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Goldspink, Mark Richard. "Synthesis and properties of some novel electrically active ionophores". Thesis, Royal Holloway, University of London, 1988. http://repository.royalholloway.ac.uk/items/60a2c468-741c-43ea-a9a8-459ae6a5eff5/1/.
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This thesis reports an investigation of the synthesis and properties of a series of electrically active crown ethers and cryptand complexes. The work has fallen into a number of distinct categories: (i) The synthesis of and structural studies on an ion-binding ferrocene-bridged cryptand in which the ferrocene unit as a potential redox centre has been investigated. The ion-binding abilities of andselectivities shown by these materials have been established by a variety of chemical and spectroscopic techniques. The results obtained have been compared with their receptor cavity sizes as established by X-ray structural studies. There is no spectroscopic evidence for any direct interaction between the iron atom and a metal ion residing in the cryptand cavity. (ii) The effect of crown ether or cryptand encapsulation of a metal ion on the properties of some electrically active salts have been investigated. Two different types of material have been studies; (a) TCNQ salts which show metallic/semiconducting behaviour and (b) oxonol dye salts which are semi-insulators. It has been shown that the presence of crown ethers significantly modifies the electronic behaviour of these materialsand can cause a complete change in the dominant conduction mechanism. (iii) A series of substituted and polymeric crown ethers have been prepared and synthetic routes to a polymerisable cryptand have been explored. Polymeric crown ether/TCNQ salts are found to show similar electrical behaviour to that seen for the monomeric anaolgues.
11
Vaughan, Simon. "Properties of soft X-ray bright Active Galactic Nuclei". Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/30654.
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Studies of the extremes of behaviour observed in Active Galactic Nuclei (AGN) constrain the physics of their emission processes by pushing existing models to their limits. Narrow-Line Seyfert 1 (NLS1s) represent one extreme of the AGN phenomenon, and soft X-ray selection is an efficient way to find NLS1s. This thesis examines the X-ray and optical properties of soft X-ray bright AGN and NLS1s in particular. The X-ray spectral properties, as observed by ASCA , of a sample of 22 NLS1s are discussed. The X-ray continua show a wide range in slope, with a mean only slightly steeper than that of 'normal' Seyfert Is and most show 'soft excess' emission, often containing a significant fraction of the X-ray luminosity. In addition, some NLS1s show spectral features in the range 0.7-0.9 keV and 1.1-1.4 keV, which are described in terms of absorption in photoionised material along the line-of-sight. The X-ray properties of the bright NLS1 Ark 564 are examined in detail and the X-ray spectrum is found to be consistent with a model comprising a power-law plus 'reflection' from ionised matter. A re-analysis of the ROSAT Wide Field Camera all-sky survey data is presented. A total of 19 AGN are detected in the extreme-ultraviolet, including eight NLS1s, making this the first complete sample to contain a high fraction of NLS1s. This work is extended using a larger, complete sample of AGN selected on the basis of 0.25 keV flux. Correlations between the measured X-ray and optical properties are discussed and the sample is used to isolate objects at the extreme ends of the parameter space explored. The luminosity function of the sample is presented, along with the luminosity functions of Seyferts classified on the basis of H/3 width and X-ray spectral slope.
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Asmus, Daniel [Verfasser]. "Mid-infrared properties of local active galactic nuclei / Daniel Asmus". Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/102237608X/34.
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Jupe, Samuel Charles Edward. "Active management of distributed generation based on component thermal properties". Thesis, Durham University, 2010. http://etheses.dur.ac.uk/265/.
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Power flows within distribution networks are expected to become increasingly congested with the proliferation of distributed generation (DG) from renewable energy resources. Consequently, the size, energy penetration and ultimately the revenue stream of DG schemes may be limited in the future. This research seeks to facilitate increased renewable energy penetrations by utilising power system component thermal properties together with DG power output control techniques. The real-time thermal rating of existing power system components has the potential to unlock latent power transfer capacities. When integrated with a DG power output control system, greater installed capacities of DG may be accommodated within the distribution network. Moreover, the secure operation of the network is maintained through the constraint of DG power outputs to manage network power flows. The research presented in this thesis forms part of a UK government funded project which aims to develop and deploy an on-line power output control system for wind-based DG schemes. This is based on the concept that high power flows resulting from wind generation at high wind speeds could be accommodated since the same wind speed has a positive effect on component cooling mechanisms. The control system compares component real-time thermal ratings with network power flows and produces set points that are fed back to the DG for implementation. The control algorithm comprises: (i) An inference engine (using rule-based artificial intelligence) that decides when DG control actions are required; (ii) a DG set point calculator (utilising predetermined power flow sensitivity factors) that computes updated DG power outputs to manage distribution network power flows; and (iii) an on-line simulation tool that validates the control actions before dispatch. A section of the UK power system has been selected by ScottishPower EnergyNetworks to form the basis of field trials. Electrical and thermal datasets from the field are used in open loop to validate the algorithms developed. The loop is then closed through simulation to automate DG output control for increased renewable energy penetrations.
14
Motamedi, Ali Reza. "Ultrafast nonlinear optical properties of passive and active semiconductor devices". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66017.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references.
Nonlinear optical properties and ultrafast carrier dynamics of slab-coupled optical waveguide amplifiers, silicon nanowaveguides, and III-V semiconductor saturable Bragg reflectors are studied. The limits imposed by two photon absorption and free-carrier absorption on the gain and output powers of an InGaAsP/InP slab-coupled optical waveguide amplifier with a confinement factor of [gamma] = 0.5% are determined. The two-photon absorption coefficient and the induced freecarrier absorption cross-section were measured to be 65cm/GW and 7x10-4 cm2, respectively. The effects of two-photon absorption begin to limit the gain significantly for pulses shorter than 40ps. The carrier recovery times were observed to vary between 390 to 160ps for 1A to 4A bias currents, and the short-pulse saturation fluence of the gain was determined to be 1.4mJ/cm2. Furthermore, nonlinear optical processes in high-index-contrast waveguide circuits consisting of 106nm x 497nm silicon waveguides with Si0 2 and HSQ cladding layers were studied using a heterodyne pump probe experimental setup. The linear loss of the waveguides was determined to be 6.5dB/cm. The two-photon absorption coefficient and free-carrier absorption effective crosssection were determined to be 0.68cm/GW, and 1.9x10-17 cm 2, respectively. Coefficients for the index changes due to optical Kerr effect, and free-carrier density were determined to be 3.2x10- 4 cm 2/W, and -5.5x10-21 cm3. Effects of the proton bombardment on linear loss and carrier lifetimes in the devices were also studied. Carrier lifetime reduction to 33ps with a linear loss of only 14.8dB/cm was achieved using a proton bombardment level of 105 /cm 2. Ultrafast dynamics of semiconductor saturable absorber mirrors were also investigated. The addition of resonant layers to the absorbers resulted in lower saturation fluence and increased non-saturable loss. Proton bombardment was utilized on these devices as well, to decrease the carrier recovery times. With proton bombardment of single-absorber layer devices with 40KeV proton energies at a dose of 1015/cm2, a 1.5ps carrier recovery time was achieved in single-absorber structures.
by Ali Reza Motamedi.
Ph.D.
15
Abdullah, Mat Johar. "A study of electro-active properties of polymer/ceramic composites". Thesis, Bangor University, 1990. https://research.bangor.ac.uk/portal/en/theses/a-study-of-electroactive-properties-of-polymerceramic-comosites(dd268320-00aa-47ac-831c-1f640b6edb77).html.
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Terada, Kayo. "Synthesis and Properties of Amino Acid-derived Optically Active Polymers". 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/77990.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第14642号
工博第3110号
新制||工||1463(附属図書館)
26994
UT51-2009-D354
京都大学大学院工学研究科高分子化学専攻
(主査)教授 中條 善樹, 教授 木村 俊作, 准教授 三田 文雄
学位規則第4条第1項該当
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Figueroa, Morales Nuris. "Active bacterial suspensions : from microhydrodynamics to transport properties in microfluidic channels". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066693/document.
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Nous étudions la dynamique de nage de bactéries Escherichia coli dans différents environnements. Leur mouvement 3D est déterminé au moyen d'un système de suivi Lagrangien 3D automatisé pour suivre des objets fluorescents que nous avons développé. Les bactéries étudiées avec ce système présentent une dispersion du coefficient de diffusion rotationnel particulièrement large, ce qui contredit la vision communément admise de la dynamique "run-and-tumble" qui a été établie pour une bactérie qui nage. Ce résultat est interprété comme une conséquence de la distribution en loi de puissance des temps de "run" expérimentaux d'un flagelle individuel, qui jusqu'alors restait indépendant de la description cinématique. Dans des écoulements confinés, la migration vers l'amont d'E. coli sur les bords reste possible pour des taux de cisaillement bien plus grands que ceux de la surface plane. La vitesse des bactéries sur les bords n'est pas influencée par l'écoulement advectif. Le mouvement vers l'amont a lieu près des parois dans une "couche limite" dont la taille varie avec le taux de cisaillement imposé. La migration vers l'amont sous écoulement et persistance de direction se combinent lors du processus de contamination. Nous montrons que les bactéries peuvent contaminer des régions propres par nage vers l'amont dans des environnements confinés.Un modèle simple, qui prend en compte la statistique de rotation du moteur, décrit de manière satisfaisante les principales caractéristiques du processus de contamination, en faisant l'hypothèse d'une distribution en loi de puissance des temps de “run”. Le modèle échoue à reproduire la dynamique quanlitative lorsque l'on prend en compte la distribution classique de run-and-tumble. Nous en concluons que le transport macroscopique de bactéries est déterminé pour la statistique de rotation du moteurWe present a study of the swimming dynamics of Escherichia coli bacteria in different physical conditions. Their 3D motion is assessed by means of a device for automated 3D Lagrangian tracking of fluorescent objects, that we developed for that purpose. Bacteria studied in that way display consistently large dispersion of the rotational diffusion coefficient, contradicting the standard vision of run-and-tumble dynamics established for an adapted bacterium. The result is interpreted as a consequence of the power law distribution of run times experimentally found for individual flagella, that up to now remained uncoupled with the motility description.We also study the bacterial swimming in polymeric suspensions, as well as in more concentrated active suspensions.In confined flows, upstream migration of E. coli at the edges remains possible at much larger flow rates compared to the motion at the flat surfaces. The bacteria speed at the edges is not influenced by the advective flow. Upstream motion takes place close to the edges in an “edge boundary layer” whose size varies with the applied flow rate. Upstream migration under flow and direction persistence combine during contamination processes. We show that bacteria can contaminate clean regions by upstream swimming in confined environments. A simple model considering the motor rotation statistics describes well the main features of the contamination process, assuming a power law distribution of run times. The model fails to reproduce the qualitative dynamics when the classical run-and-tumble distribution is determined by the motor rotation statistics
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Furukawa, Shuhei. "Studies on structures and properties of redox-active metal complex assemblies". 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144943.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第11599号
工博第2545号
新制||工||1346(附属図書館)
23242
UT51-2005-D348
京都大学大学院工学研究科合成･生物化学専攻
(主査)教授 北川 進, 教授 杉野 目道紀, 教授 年光 昭夫
学位規則第4条第1項該当
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Sobocinski, Raymond Louis 1962. "LASER-INDUCED THERMAL DECAY OF PYRIDINE AND CHLORIDE SURFACE-ENHANCED RAMAN SCATTERING AS A PROBE OF SILVER SURFACE-ACTIVE SITES". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276553.
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The activation parameters for the temperature dependent irreversible loss of surface-enhanced Raman scattered (SERS) intensity from pyridine and chloride adsorbed at silver surfaces in an electrochemical environment have been determined. Laser-induced heating is introduced as a probe of the chemical nature of SERS-active sites. Surface temperatures are calculated from spectroscopic data. The activation energies associated with the destruction of SERS-active sites at a surface roughened by an illuminated oxidation-reduction cycle (ORC) are 12.8 ± 3.2 kcal/mole and 27.7 ± 3.1 kcal/mole for pyridine at two different types of sites on the Ag surface. Similarly, values for coadsorbed chloride are found to be 11.1 ± 2.4 kcal/mole and 24.5 ± 3.8 kcal/mole. An activation energy of 27.4 ± 1.9 kcal/mole is obtained for pyridine on a silver surface roughened by a nonilluminated ORC. Evidence for the desorption of pyridine and chloride is presented.
20
Mobbs, Tamara Leah. "Effects of four soil surfactants on four soil-water properties in sand and silt loam". Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Spring2010/t_mobbs_050110.pdf.
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Thesis (M.S. in biological and agricultural engineering)--Washington State University, May 2010.Title from PDF title page (viewed on June 23, 2010). "Department of Biological Systems Engineering." Includes bibliographical references (p. 16-22).
21
Åkesson, Henrik. "Active control of vibration and analysis of dynamic properties concerning machine tools". Licentiate thesis, Karlskrona : Blekinge Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00360.
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Vibration in internal turning is a problem in the manufacturing industry. Vibrations appear under the excitation applied by the material deformation process during the machining of a workpiece. In order for a lathe to perform an internal turning or boring operation, for example, in a pre-drilled hole in a workpiece, it is generally required that the boring bar should be long and slender; therefore extra sensitive to vibrations. These vibrations will affect the result of machining, in particular the surface finish, also the tool life may be reduced. As a result of tool vibration, severe acoustic noise frequently occurs in the working environment. This thesis comprises three parts and the first part presents a method for active control of boring bar vibration. This method consists of an active boring bar controlled by, for example, an analog controller. The focus lies on the analog controller and the advantages that may be obtained from working in the analog domain. The controller is a lead-lag compensator with digitally controlled parameters, such as gain and phase. However, signals remain in the analog domain. In addition, the analog controller is compared with a digital adaptive controller and it is found that both controllers yield an attenuation of the vibration by up to 50 dB. The second part of this thesis concerns the dynamic properties of a clamped boring bar used by the industry. In order to design a robust controller for a certain system, knowledge about the system's dynamic properties is required. On the workshop floor, a boring bar is dismounted and remounted, and reconfiguration of boring bars will alter the dynamic properties of the clamped boring bar. The dynamic properties of a standard boring bar and an active boring bar for a number of possible clamping conditions, as well as for a linearized clamping have been investigated based on an experimental approach. Also simple Euler-Bernoulli modeling of clamped boring bars incorporating simple non-rigid models of the boring bar clamping are investigated. Initial simulations of nonlinear SDOF systems have been carried out: one with a signed squared stiffness and one with a cubic stiffness. The purpose of these simulations was to identify a nonlinearity that introduces a similar behavior in the SDOF system dynamics as the nonlinear behavior observed in the dynamic properties of a clamped boring bar. The third and final part of this thesis focuses on vibration analysis methods in engineering education. A signal analyzer (which is a commonly used instrument in signal processing and vibration analysis) was made accessible via the Internet. Assignments were developed for students to learn and practice vibration analysis on real signals from a real setup of a relevant structure; a clamped boring bar. Whilst the experimental setup was fixed, the instrument and sensor configuration nonetheless enable a variety of experiment, for example: excitation signal analysis, spectrum analysis and experimental modal analysis.
22
Krumpe, Mirko. "X-ray and optical properties of X-ray luminous active galactic nuclei". Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1699/.
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Giacconi et al. (1962) discovered a diffuse cosmic X-ray background with rocket experiments when they searched for lunar X-ray emission. Later satellite missions found a spectral peak in the cosmic X-ray background at
~30 keV. Imaging X-ray satellites such as ROSAT (1990-1999) were able to resolve up to 80% of the background below 2 keV into single point sources, mainly active galaxies. The cosmic X-ray background is the integration
of all accreting super-massive (several million solar masses) black holes in the centre of active galaxies over cosmic time. Synthesis models need further populations of X-ray absorbed active galaxy nuclei (AGN) in order to explain the cosmic X-ray background peak at ~30 keV. Current X-ray missions such as XMM-Newton and Chandra offer the possibility of studying these additional populations.
This Ph.D. thesis studies the populations that dominate the X-ray sky. For this purpose the 120 ksec XMM-Newton Marano field survey, named for an earlier optical quasar survey in the southern hemisphere, is analysed. Based on the optical follow-up observations the X-ray sources are spectroscopically classified. Optical and X-ray properties of the different X-ray source populations are studied and differences are derived. The amount of absorption
in the X-ray spectra of type II AGN, which are considered as a main contributor to the X-ray background at ~30 keV, is determined. In order to extend the sample size of the rare type II AGN, this study also includes objects from another survey, the XMM-Newton Serendipitous Medium Sample. In addition, the dependence of the absorption in type II AGN with redshift and X-ray luminosity is analysed. We detected 328 X-ray sources in the Marano field. 140 sources were spectroscopically classified. We found 89 type I AGN, 36 type II AGN, 6 galaxies, and 9 stars. AGN, galaxies, and stars are clearly distinguishable by their optical and X-ray properties. Type I and II AGN do not separate clearly. They have a significant overlap in all studied
properties. In a few cases the X-ray properties are in contradiction to the observed optical properties for type I and type II AGN. For example we find type II AGN that show evidence for optical absorption but are not absorbed in X-rays. Based on the additional use of near infra-red imaging (K-band), we were able to identify several of the rare type II AGN.
The X-ray spectra of type II AGN from the XMM-Newton Marano field survey and
the XMM-Newton Serendipitous Medium Sample were analysed. Since most of the sources have only ~40 X-ray counts in the XMM-Newton PN-detector, I carefully studied the fit results of simulated X-ray spectra as a function of fit statistic and binning method. The objects revealed only moderate absorption. In particular, I do not find any Compton-thick sources (absorbed by column densities of NH > 1.5 x 10^24 cm^−2). This gives evidence that type II AGN are not the main contributor of the X-ray background around 30 keV. Although bias effects may occur, type II AGN show no noticeable trend of the amount of
absorption with redshift or X-ray luminosity.Giacconi et al. (1962) entdeckten mit Hilfe von Raketenexperimenten auf der Suche nach Röntgenstrahlung vom Mond eine scheinbar diffuse extragalaktische Röntgenhintergrundstrahlung. Spätere Satellitenmissionen detektierten ein Maximum dieser Strahlung bei ~30 keV. Abbildenden Röntgensatelliten wie ROSAT (1990-1999) gelang es, bis zu 80% des diffusen Hintergrundes unter 2 keV in einzelne Punktquellen aufzulösen, von denen die überwiegende Mehrheit aktive Galaxienkerne waren. Der Röntgenhintergrund ist somit wahrscheinlich als die Emission der Gesamtheit aller akkretierenden superschweren (mehrere Millionen Sonnenmassen) schwarzen Löcher in den Zentren von Galaxien in der kosmischen Geschichte zu verstehen. Zur Erklärung des Maximums der spektralen Energieverteilung der Röntgenhintergrundstrahlung bei ~30 keV benötigen theoretische Modelle jedoch zusätzliche Populationen von röntgenabsorbierenden aktiven Galaxienkernen (AGN). Derzeitige Röntgenmissionen wie XMM-Newton und Chandra ermöglichen die Untersuchung dieser Quellklassen. Die vorliegende Arbeit untersucht die Quellpopulationen, die den Röntgenhimmel dominieren. Dazu wird die 120 ksec XMM-Newton Beobachtung im Marano Feld, Ziel einer früheren optischen AGN-Durchmusterung am Südhimmel, ausgewertet. Die optischen und Röntgeneigenschaften der unterschiedlichen Quellpopulationen werden untersucht und Unterschiede erarbeitet. Für die röntgenabsorbierende Objektklasse der Typ II AGN, die man als möglichen Erzeuger der Röntgenstrahlung um 30 keV betrachtet, wird aus den Röntgenspektren das Ausmaß der Absorption ermittelt. Um die Anzahl dieser selten gefundenen Objekte zu erhöhen, werden in dieser Arbeit zusätzliche Objekte aus der Röntgendurchmusterung des “XMM-Newton Serendipitous Medium Sample” einbezogen. Die Abhängigkeit der Absorption von der Rotverschiebung und der Röntgenleuchtkraft wird untersucht. Von 328 Röntgenquellen im Marano Feld konnten 140 spektroskopisch klassifiziert werden. Es wurden 89 Typ I AGN, 36 Typ II AGN, 6 Galaxien und 9 Sterne gefunden. Nur basierend auf den optischen und Röntgeneigenschaften können AGN, Galaxien und Sterne unterschieden werden. Typ I und II AGN lassen sich nicht klar trennen und zeigen große Gemeinsamkeiten in den untersuchten Eigenschaften. Mit Hilfe von zusätzlichen Aufnahmen im nahen Infraroten (K-Band) konnten erfolgreich mehrere seltene Typ II AGN identifiziert werden. Die Röntgenspektren von Typ II AGN aus dem XMM-Newton Marano Feld und dem “XMM-Newton Serendipitous Medium Sample” wurden ausgewertet. Die Objekte weisen nur eine mäßige Absorption auf und scheinen somit nicht einen Hauptbestandteil des Röntgenstrahlungshintergrundes um 30 keV zu erzeugen. Obwohl Selektionseffekte nicht vollständig verstanden sind, zeigen Typ II AGN keine erkennbare Abhängigkeit der Absorption von der Rotverschiebung oder der Röntgenleuchtkraft.
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Åkesson, Henrik. "Active control of vibration and analysis of dynamic properties concerning machine tools /". Karlskrona : Department of Signal Processing, School of Engineering, Blekinge Institute of Technology, 2007. http://www.bth.se/fou/Forskinfo.nsf/allfirst2/c1c8b0fe1d34f181c12572b3003518d4?OpenDocument.
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Veglio, Paolo <1982>. "Global scale investigation of cirrus clouds properties using active and passive sensors". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5716/.
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A year of satellite-borne lidar CALIOP data is analyzed and statistics on occurrence and distribution of bulk properties of cirri are provided.
The relationship between environmental and cloud physical parameters and the shape of the backscatter profile (BSP) is investigated. It is found that CALIOP BSP is mainly affected by cloud geometrical thickness while only minor impacts can be attributed to other quantities such as optical depth or temperature.
To fit mean BSPs as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. It is demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.
The IWC parameterization is included into the RT-RET retrieval algorithm, that is exploited to analyze infrared radiance measurements in presence of cirrus clouds during the ECOWAR field campaign.
Retrieved microphysical and optical properties of the observed cloud are used as input parameters in a forward RT simulation run over the 100-1100 cm-1 spectral interval and compared with interferometric data to test the ability of the current single scattering properties database of ice crystal to reproduce realistic optical features.
Finally a global scale investigation of cirrus clouds is performed by developing a collocation algorithm that exploits satellite data from multiple sensors (AIRS, CALIOP, MODIS). The resulting data set is utilized to test a new infrared hyperspectral retrieval algorithm. Retrieval products are compared to data and in particular the cloud top height (CTH) product is considered for this purpose. A better agreement of the retrieval with the CALIOP CTH than MODIS is found, even if some cases of underestimation and overestimation are observed.
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Ionov, Leonid. "Active Stimuli-Responsive Polymer Surfaces and Thin Films: Design, Properties and Applications". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-159666.
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Design of 2D and 3D micropatterned materials is highly important for printing technology, microfluidics, microanalytics, information storage, microelectronics and biotechnology. Biotechnology deserves particular interest among the diversity of possible applications because its opens perspectives for regeneration of tissues and organs that can considerably improve our life. In fact, biotechnology is in constant need for development of microstructured materials with controlled architecture. Such materials can serve either as scaffolds or as microanalytical platforms, where cells are able to self-organize in a programmed manner. Microstructured materials, for example, allow in vitro investigation of complex cell-cell interactions, interactions between cells and engineered materials. With the help of patterned surfaces it was demonstrated that cell adhesion and viability as well as differentiation of stem cells1 depend of on the character of nano- and micro- structures 2 as well as their size.
There are number of methods based on optical lithography, atomic force microscopy, printing techniques, chemical vapor deposition, which have been developed and successfully applied for 2D patterning. While each of these methods provides particular advantages, a general trade-off between spatial resolution, throughput, “biocompatibility of method” and usability of fabricated patterned surfaces exists. For example, AFM-based techniques allow very high nanometer resolution and can be used to place small numbers of functional proteins with nanometer lateral resolution, but are limited to low writing speeds and small pattern sizes. Albeit, the resolution of photolithography is lower, while it is much faster and cheaper.
Therefore, it is highly desirable to develop methods for high-resolution patterning at reasonably low cost and high throughput. Although many approaches to fabricate sophisticated surface patterns exist, they are almost entirely limited to producing fixed patterns that cannot be intentionally modified or switched on the fly in physiologic environment. This limits the usability of a patterned surface to a single specific application and new microstructures have to be fabricated for new applications. Therefore, it is desirable to develop methods for design of switchable and rewritable patterns. Next, the high-energy of the ultraviolet radiation, which is typically used for photolithography, can be harmful for biological species. It is also highly important to develop an approach for photopatterning where visible light is used instead of UV light. Therefore, it is very important for biotechnological applications to achieve good resolution at low costs, create surface with switchable and reconfigurable patterns, perform patterning in mild physiologic conditions and avoid use of harmful UV light.
3D patterning is experimentally more complicated than 2D one and the applicability of available techniques is substantially limited. For example, interference photolithography allows fabrication of 3D structures with limited thickness. Two-photon photolithography, which allows nanoscale resolution, is very slow and highly expensive. Assembling of 3D structures by stacking of 2D ones is time consuming and does not allow fabrication of fine hollow structures. At the same time, nature offers an enormous arsenal of ideas for the design of novel materials with superior properties. In particular, self-assembly and self-organization being the driving principles of structure formation in nature attract significant interest as promising concepts for the design of intelligent materials 3. Self-folding films are the examples of biomimetic materials4. Such films mimic movement mechanisms of plants 5-7 and are able to self-organize and form complex 3D structures. The self-folding films consist of two materials with different properties. At least one of these materials, active one, can change its volume. Because of non-equal expansion of the materials, the self-folding films are able to form a tubes, capsules or more complex structure. Similar to origami, the self-folding films provide unique possibilities for the straightforward fabrication of highly complex 3D micro-structures with patterned inner and outer walls that cannot be achieved using other currently available technologies. The self-folded micro-objects can be assembled into sophisticated, hierarchically-organized 3D super-constructs with structural anisotropy and highly complex surface patterns.
Till now most of the research in the field of self-folding films was focused on inorganic materials. Due to their rigidity, limited biocompatibility and non-biodegradability, application of inorganic self-folding materials for biomedical purposes is limited. Polymers are more suitable for these purposes. There are many factors, which make polymer-based self-folding films particularly attractive. There is a variety of polymers sensitive to different stimuli that allows design of self-folding films, which are able to fold in response to various external signals. There are many polymers changing their properties in physiological ranges of pH and temperature as well as polymers sensitive to biochemical processes. There is a variety of biocompatible and biodegradable polymers. These properties make self-folding polymer highly attractive for biological applications. Polymers undergo considerable and reversible changes of volume that allows design of systems with reversible folding. Fabrication of 3D structures with the size ranging from hundreds of nanometers to centimeters is possible. In spite of their attractive properties, the polymer-based systems remained almost out of focus – ca 15 papers including own ones were published on this topic (see own review 8, state October 2011).
Thereby the development of biomimetic materials based on self-folding polymer films is highly desired and can open new horizons for the design of unique 3D materials with advanced properties for lab-on-chip applications, smart materials for everyday life and regenerative medicine.
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Sogawa, Hiromitsu. "Synthesis and Properties of Amino Acid-derived Optically Active π-Conjugated Polymers". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174959.
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Mahenthirarajah, Thushitha. "Synthesis and characterisation of electronically active species". Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/954.
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An exploration of some early transition metal (oxy) fluoride systems using solvothermal techniques has been carried out. 30 novel materials have been synthesised, which fall into three classes based on different metal centres; vanadium (21), molybdenum (5) and niobium (4). Some of these also contain secondary metal centres, namely copper (22) and zinc (1). Simultaneously, the relationship between the SHG values and the crystal structures of the hilgardites family members Pb₂B₅O₉Cl, Pb₂B₅O₉Br, Sr₂B₅O₉Cl and Ba₂B₅O₉Cl was investigated. In particular, the Pb–containing members of the hilgardite family of borate halides exhibit an abnormally large non–linear optical response, which was analysed based on neutron powder diffraction. Using solvothermal synthesis in HF–containing media, 21 novel vanadium oxyfluorides containing interesting structural features, were synthesised at 160˚C using a range of organo-amine compounds as a ligand, template, linker or structure directing agent. The architectures of the crystal structures may be categorised into; four clusters including monomeric vanadium units, five clusters including vanadium dimers, eight 1–D chains, two 2–D layers and two 3–D networks. ‘Composition–space’ diagrams with three components were used to study the effect of stoichiometry changes of reactants and to map out the crystallisation fields. The combination of early (Nb⁵⁺, Mo⁶⁺) and late (Cu²⁺) transition metals with different organo-amines produced nine novel compounds incorporating monomers, chains and 2– D interpenetrated networks. The chains and layers were synthesised from a systematic series of reactions at 160˚C and can be subdivided into four pairs, the topologies of which are essentially unique to each ligand, containing in each case a Cu–based cationic species, but alternately either [MoO₂F₄]²⁻ or [NbOF₅]²⁻, in an isomorphous manner, as the anionic moiety. The overall structures of these materials reflect the influence of the organo–amine ligands. The materials have been studied for their magnetic properties and characterised by thermogravimetric analysis, Rietveld refinement and elemental analysis where relevant.
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Tucker, Ian Malcolm. "The surface and solution properties of complex mixed surfactant systems". Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670103.
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Blunt, Gina H. "Worksite supportive environments for active living survey (worksite SEALS) : development and psychometric properties /". Full text available from ProQuest UM Digital Dissertations, 2006. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1260794081&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1193081064&clientId=22256.
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Sun, Zheng y 孙诤. "In vitro studies of antiglycoxidative properties of microalgal extracts and their active compounds". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46480638.
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Kadem, Burak Yahya. "P3HT:PCBM-based organic solar cells : optimisation of active layer nanostructure and interface properties". Thesis, Sheffield Hallam University, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.713504.
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Organic solar cells (OSCs) have attracted a significant attention during the last decade due to their simple processability on a flexible substrate as well as scope for large-scale production using role to role technique. Improving the performance of the organic solar cells and their lifetime stability are one of the main challenges faced by researchers in this field. In this thesis, work has been carried out using a blend of Poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) as an active layer in the ratio of (1:1) (P3HT:PCBM). The efficiency and stability of P3HT:PCBM-based solar cells have been examined using different methods and employing novel materials such asl-[N-(2- ethoxyethyl) pent-4-ynamide] -8 (11), 15 (18), 22 (25) - tris -{2-[2-(2-ethoxyethoxy) ethoxy] -l-[2-((2- ethoxyethoxy) - ethoxy) methyl] ethyloxy] phthalocyaninato zinc (II) (ZnPc) to construct a ternary hybrid as the active layer. Controlling the morphology and crystallinity of P3HT:PCBM active layer was carried out using different solvents including chloroform (CF), chlorobenzene (CB) and dichlorobenzene (DCB) and their co-solvents in the ratio of (1:1) to dissolve the P3HT:PCBM blend. Optimum morphology and crystallinity were achieved using a co-solvent made of CB:CF with the obtained solar cell exhibiting the highest performance with PCE reaching 2.73% among other devices prepared using different solvents. Further device performance improvement was observed through optimization of active layer thickness with studied thickness falling in range 65-266 nm. Measurements of the PV characteristics of the investigated OSC devices have revealed optimum performance when active layer thickness was 95 nm with PCE=3.846%. The stability of the P3HT:PCBM-based devices on optimisation of the active layer thickness has shown a decrease in PCE of about 71% over a period of 41 days. Furthermore, P3HT has been blended with different fullerene derivatives (PC60BM, PC61BM, PC70BM and PC71BM) and the active layers were processed using the optimum solvent as well as optimum film’s thickness.
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Bayoudh, Mehdi. "Active Diagnosis of Hybrid Systems Guided by Diagnosability Properties - Application to Autonomous Satellites". Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT069H.
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Motivée par les besoins du domaine spatial en termes de diagnostic embarqué et d’autonomie, cette thèse s’intéresse aux problèmes de diagnostic, de diagnosticabilité et de diagnostic actif des systèmes hybrides. Un formalisme hybride est proposé pour représenter les deux dynamiques, continues et discrètes, du système. En s’appuyant sur ce modèle, une approche de diagnostic passif est proposée en mariant les techniques des systèmes à événements discrets et des systèmes continus. Un cadre formel pour la diagnosticabilité des systèmes hybrides a également été établi proposant des définitions et des critères pour la diagnosticabilité hybride. Suite à un diagnostic passif ambigu, le diagnostic actif est nécessaire afin de désambiguïser l’état du système. Cette thèse propose donc une approche de diagnostic actif, qui partant d’un état de croyance incertain, fait appel aux propriétés de diagnosticabilité du système pour déterminer la configuration où les fautes peuvent être discriminées. Une nouvelle machine à états finis appelée diagnostiqueur actif est introduite permettant de formaliser le diagnostic actif comme un problème de planification conditionnelle. Un algorithme d’exploration de graphes ET-OU est proposé pour calculer les plans de diagnostic actif. Finalement, l’approche de diagnostic a été testée sur le Système de Contrôle d’Attitude (SCA) d’un satellite de Thales Alenia Space. Le module de diagnostic a été intégré dans la boucle fermée de commande. Des scénarios de faute ont été testés donnant des résultats très satisfaisantsMotivated by the requirements of the space domain in terms of on-board diagnosis and autonomy, this thesis addresses the problems of diagnosis, diagnosability and active diagnosis of hybrid systems. Supported by a hybrid modeling framework, a passive approach for model-based diagnosis mixing discrete-event and continuous techniques is proposed. The same hybrid model is used to define the diagnosability property for hybrid systems and diagnosability criteria are derived. When the diagnosis provided by the passive diagnosis approach is ambiguous, active diagnosis is needed. This work provides a method for performing such active diagnosis. Starting with an ambiguous belief state, the method calls for diagnosability analysis results to determine a new system configuration in which fault candidates can be discriminated. Based on a new finite state machine called the diagnoser, the active diagnosis is formulated as a conditional planning problem and an AND-OR graph exploration algorithm is proposed to determine active diagnosis plans. Finally, the diagnosis approach is tested on the Attitude Control System (ACS) of a satellite simulator provided by Thales Alenia Space. The diagnosis module is successfully tested on several fault scenarios and the obtained results are reported
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Mahajan, Kamal. "Synthesis and Characterization of New Active Barrier Polymers". University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271339021.
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Lowry, Curtis Wayne. "Optical nonlinearities in passive and active gallium arsenide with applications to optical switching and laser instabilities". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186295.
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Nonlinear optical properties of passive and active semiconductors are investigated experimentally and theoretically. Improvement of switching cycle time in optical nonlinear etalons to 40 ps is demonstrated, and strained-layer InGaAs/GaAs quantum well material is used in an asymmetric etalon to greatly improve switching power and contrast. Coherent energy transfer (CET) induced by injection of an external light field is demonstrated in a GaAs quantum well vertical-cavity surface-emitting laser (VCSEL). The evolution of CET induced asymmetric gain with increasing injected power is investigated experimentally and theoretically, and it is found that the CET induced effective gain peak and dip are detuned proportionally with injected power as in homogeneously broadened media and in contrast to other multi-wave effects in GaAs which are detuned proportionally with the light field. Transfer of gain modification between orthogonally polarized modes of the VCSEL and cascading of gain modification within a mode is observed and investigated. The approach of a laser to an injection locked state through increased injected power is investigated experimentally and theoretically, showing new emission frequencies produced which evolve to chaos-like behavior before reaching the phase locked state. CET induced gain modification is used to demonstrate low-power high-contrast switching between polarization modes of the VCSEL with differential gain of 3,510. Switching speed and switching bistability is observed and investigated. Injection induced modification of VCSEL transverse modes is studied experimentally and theoretically. Field defects in the resulting field are observed, and their locations are dependent on the frequency of the injected field, in contrast to the temporally evolving defects normally observed. The rich behavior of nonlinear properties, especially in gain media provide interesting results and valuable applications.
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Chaudhary, Pooja [Verfasser] y Ralf [Akademischer Betreuer] Bender. "Properties of the integrated spectrum of active galactic nuclei / Pooja Chaudhary. Betreuer: Ralf Bender". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1019074574/34.
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Walter, Felicitas [Verfasser]. "Optical properties and encoding of information of nonlinear and active plasmonic metasurfaces / Felicitas Walter". Paderborn : Universitätsbibliothek, 2018. http://d-nb.info/1171897685/34.
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Kubavat, Harshal A. "The influence of crystallization on the mechanical and interfacial properties of active pharmaceutical ingredients". Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548090.
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Ichikawa, Kohei. "Study of Dust-Torus Properties around Supermassive Black Holes". 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199105.
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Zaki, Afroditi Maria. "Molecular dynamics study of biomembrane interactions with biologically active polymers". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/molecular-dynamics-study-of-biomembrane-interactions-with-biologically-active-polymers(0e61623d-d73c-4f84-a1ef-6698026c4aa2).html.
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Among the great breakthroughs in nanoscience and nanotechnology is the emergence of synthetic polymers that demonstrate biological activity and thus can be exploited for biomedical applications, extending from agents in therapeutics to drug delivery and tissue engineering. A key factor in the fabrication of such polymeric materials is the ability to tune and control their properties. To this end, an insight into the mode of interactions with biological systems is imperative. Computer simulations have proved to be a valuable tool that can compliment experiments and provide -otherwise inaccessible- information. In the context of this thesis, different aspects of the polymeric biological activity were investigated by studying two polymeric materials suitable for different types of applications, aiming to clarify yet undisclosed mechanisms that govern the polymers' behaviour either in solution or in conjunction with model lipid membranes. The first part of the thesis is dedicated to a nonionic amphiphilic copolymer known as Pluronic L64 that is considered as a candidate for the design of novel hybrid polymer-lipid vesicles that will act as carriers for drugs or genes. The hybrid bilayers are subjected to mechanical stress and their properties are compared to those of pure lipid bilayers. The simulations showed that the hybrid membranes can sustain increased surface tension prior to rupture, are stiffer, thicker and the polymers can induce higher lipid tail packing and also reduce the lipid mobility, rendering the membranes more ordered and less fluid. At high values of lateral pressure, which leads to pore formation, the copolymer chains decelerate the pore growth. The examination of the defect formation mechanism reveals that the hydrophilic PEO segment plays the most vital role. The same systems were also observed in varying temperatures and the impact of the inserted polymers on the phase behaviour was investigated. The data suggested that the polymers change the nature of the phase transition from a discontinuous to a continuous one. The hybrid membranes transform between the ordered and the disordered phase in a continuous manner and not at a critical melting temperature. Interestingly, the effect of polymers is different at the low and high temperature regions, as proved by the analysis of the mechanical, structural and dynamic membrane properties. The second part is focused on the study of polyhexamethylene biguanide (PHMB), a biguanide-based polyelectrolyte, that possesses remarkable biocidal properties. Even though PHMB's activity is known, the specific mode of action against bacterial membranes is still puzzling. Our work revealed that the polyelectrolyte assumes a counterintuitive behaviour in aqueous solution tending to self-organise into ordered compact structures, despite the repulsive electrostatic interactions of its positively charged segments. The formed nano-objects are thermodynamically stable, as was confirmed by free energy calculations and could be linked to PHMB's antibacterial mechanism. These findings pave the way for further computational and experimental exploration of these fascinating and promising materials that could lead to the design of novel smart biologically active nanoparticles.
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Mitchell, Lee. "Investigation of Selected Optically-Active Nanosystems Fashioned using Ion Implantation". Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5259/.
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Opto-electronic semiconductor technology continues to grow at an accelerated pace, as the industry seeks to perfect devices such as light emitting diodes for purposes of optical processing and communication. A strive for greater efficiency with shrinking device dimensions, continually pushes the technology from both a design and materials aspect. Nanosystems such a quantum dots, also face new material engineering challenges as they enter the realm of quantum mechanics, with each system and material having markedly different electronic properties. Traditionally, the semiconductor industry has focused on materials such Group II-VI and III-V compounds as the basis material for future opto-electronic needs. Unfortunately, these material systems can be expensive and have difficulties integrating into current Si-based technology. The industry is reluctant to leave silicon due in part to silicon's high quality oxide, and the enormous amount of research invested into silicon based circuit fabrication. Although recently materials such as GaN are starting to dominate the electro-optical industry since a Si-based substitute has not been found. The purpose of the dissertation was to examine several promising systems that could be easily integrated into current Si-based technology and also be produced using simple inexpensive fabrication techniques such ion implantation. The development of optically active nano-sized precipitates in silica to form the active layer of an opto-electronic device was achieved with ion implantation and thermal annealing. Three material systems were investigated. These systems consisted of carbon, silicon and metal silicide based nanocrystals. The physical morphology and electronic properties were monitored using a variety of material characterization techniques. Rutherford backscattering/channeling were used to monitor elemental concentrations, photoluminescence was used to monitor the opto-electronic properties and transmission electron microscopy was used to study the intricate morphology of individual precipitates. The electronic properties and the morphology were studied as a function of implant dose, anneal times and anneal temperatures.
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Weyna, David Rudy. "Crystal Engineering of Multiple Component Crystal Forms of Active Pharmaceutical Ingredients". Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3406.
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Enhancing the physicochemical properties of solid-state materials through crystal engineering enables optimization of these materials without covalent modification. Cocrystals have become a reliable means to generate novel crystalline forms with multiple components and they exhibit different physicochemical properties compared to the individual components. This dissertation exemplifies methodologies to generate cocrystals of active pharmaceutical ingredients (API's) based upon knowledge of supramolecular interactions (supramolecular synthons), while focusing on enhanced delivery through in vitro and in vivo processes with both salts and cocrystals respectively.
The utility of mechanochemistry involving small amounts of an appropriate solvent, or solvent drop grinding (SDG), has been shown to reliably reproduce cocrystals with the anti-convulsant carbamazepine that were originally obtained by solution crystallization. This technique has been confirmed as a reliable screening method using solvents in which both components exhibit some solubility. The benefits of this technique lie in the time and cost efficiency associated with it as well as its inherently small environmental impact making it a "Green" method. SDG was also used as an efficient way to discover cocrystals of the anti-inflammatory meloxicam with carboxylic acids after analysis of existing reports and the analysis of structural data from the Cambridge Structural Database (CSD) to guide the choice of coformer. It has been shown that SDG can be used to screen for cocrystalline forms that are also obtainable by solution crystallization which is important in later stage development and manufacturing including but not limited to large scale up processes. Single crystals suitable for single crystal X-ray diffraction were obtained with meloxicam and two of the coformers, fumaric and succinic acid. Some of the meloxicam cocrystals exhibited enhanced pharmacokinetic (PK) profiles in rats exemplifying significantly higher serum concentrations after only fifteen minutes and consistently higher exposure over the time studied while others maintained lower exposure. This reveals that cocrystals can fine tune the PK profile of meloxicam in order to reduce or enhance exposure.
Two different sulfonate salts, 4-hydroxybenzenesulfonate (p-phenolsulfonate) and 4-chlorobenzenesulfonate, of the anti-spastic agent (R,S) baclofen were developed by strategically interrupting the intramolecularly stabilized zwitterionic structure of baclofen. This zwitterionic structure results in low solubility associated with physiological pH required for intrathecal administration. Structural data for both salts in the form of single crystal X-ray diffraction data was successfully obtained. Solubility based on baclofen was assessed and shown to increase in pure water and at pH's 1 and 7. Only the 4-chlorobenzenesulonate salt maintained an increased solubility over two days at pH 7 making it a viable candidate for further study in terms of intrathecal administration. During crystallization experiments with (R,S) baclofen two polymorphic forms of the baclofen lactam were generated, Forms II and III. Both forms are conformational polymorphs confirmed by single crystal X-ray diffraction and Form II has a Z' of 4 with an unusual arrangement of enantiomers.
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Vaičienė, Marija. "Influence of the active additives on the structure and properties of expanded-clay lightweight concrete". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120119_143017-08407.
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Two active mineral additives were selected in the investigation described in the dissertation: unground catalyst from the reactor of catalytic oil cracking (CAT) and unburned mullite wool (MW). The possibilities to utilise these raw materials in the production of the expanded-clay lightweight concrete are not analysed yet. Main topic of the research: influence of the active mineral additives (CAT and MW) on the main characteristics of the expanded-clay lightweight concrete.Disertacijoje aprašytuose tyrimuose buvo pasirinkti du aktyvūs mineraliniai priedai: nemaltas katalizatorius iš katalitinio naftos krekingo reaktoriaus (KAT) ir nedegta mulitinė vata (MV). Galimybės šias atliekas naudoti keramzitbetonio gamyboje iki šiol netirtos. Pagrindinė tyrimo tematika – aktyviųjų mineralinių priedų (KAT ir MV) įtaka pagrindinėms keramzitbetonio charakteristikoms.
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Jin, Chichuan. "A systematic study of the optical to X-ray spectral properties of active galactic nuclei". Thesis, Durham University, 2012. http://etheses.dur.ac.uk/3476/.
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In this thesis I present a detailed study of the optical to X-ray spectral properties of Active Galactic Nuclei (AGN). We propose a new broadband SED model which combines the standard accretion disc emission, low and high temperature Comptonisation components by introducing a corona radius. Applying the new models to broadband spectral data, we found that RX J0136.9-3510 and RE J0134+396 have similar {\it rms} spectra and broadband SEDs, representing a distinct spectral state which can only be attained by super Eddington flows. A detailed optical and X-ray spectral analysis is then carried out for a big sample of 51 unobscured nearby type 1 AGNs. We find that NLS1s tend to have softer 2-10 keV spectra, lower black hole mass, higher Eddington ratio, higher $\alpha_{ox}$ index and smaller coronal radius. The edge of Balmer continuum is shifted redwards and smoothed by more than predicted by the FWHM of the Balmer emission lines. A new method called `Correlation Spectra Technique (CST)' is proposed, which is powerful for multi-waveband spectral analysis. We find that among the three Balmer line components, the broad component has the best correlation with hard X-ray emission. Optical oxygen forbidden lines all well correlate with the hard X-ray emission. We conducted a systematic cross-correlation among the 9 key SED parameters: $\Gamma_{2-10keV}$, $\kappa_{2-10keV}$, $\kappa_{5100A}$, $\lambda_{Edd}$, FWHM$_{H\beta}$, M$_{BH}$, $\alpha_{ox}$, L$_{bol}$ and L$_{2-10keV}$, and found the driven parameters to be M$_{BH}$, $\lambda_{Edd}$ and L$_{bol}$ (or equivalently $\dot{M}$). AGN's intrinsic SEDs exhibit strong diversity and changes similarly with $\lambda_{Edd}$, $\kappa_{2-10keV}$, $\kappa_{5100}$, $\Gamma_{2-10keV}$, FWHM$_{H\beta}$ and M$_{BH}$. However, the SED shape is not sensitive to L$_{bol}$.
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Bernhard, E. P. W. "The relationship between Active Galactic Nuclei and the star-forming properties of their host galaxies". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19651/.
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It is now accepted that there is a co-evolution between galaxies and their central super massive black holes (SMBHs). Primarily, cosmological simulations suggest that accreting SMBHs (or Active Galactic Nuclei, AGN) must somehow quench their hosts' star-formation rates (SFRs). In contrast, empirical results report that there is no evidence of a strong (anti-)correlation between SFR and X-ray luminosity (a proxy for AGN power). In this thesis, we aim to investigate further this apparent contradiction between AGNs and their host star-forming properties. The hypothesis we test is that a powerful AGN will have a higher impact on a low mass host galaxy than on a high mass one. Therefore, instead of the previously used X-ray luminosity, we investigate the relationship between the X-ray luminosity relative to the host stellar mass (a proxy for Eddington ratio) and the host SFR. We first used a sample of 1620 X-ray selected AGNs, for which we measured Eddington ratios and their host far-infrared luminosities (a proxy for SFR) that we corrected for AGN contamination. By doing this, we found a slight enhancement of SFR at higher Eddington ratios when compared to the SFR of star-forming galaxies with similar stellar masses that do not host AGNs. Furthermore, the change in the star-forming properties at higher Eddington ratio indicates that the Eddington ratio distribution must change with the host star-forming properties. To investigate further how the Eddington ratio distribution of AGNs changes with the star-forming properties of their hosts, we used a model for which we assumed the Eddington ratio distribution simply split between star-forming and quiescent galaxies. Overall, we find that our model is able to reproduce the X-ray luminosity function but fails to reproduce the flat relationship between SFR and X-ray luminosity. Finally, we found that this can be resolved if we introduce a mass-dependency into our model.
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Corujeira, Gallo Santiago. "Active screen plasma surface engineering of austenitic stainless steel for enhanced tribological and corrosion properties". Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/275/.
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Low temperature plasma surface engineering has been a useful method for increasing the hardness and wear resistance of austenitic stainless steel without reducing the corrosion resistance of this alloy. Plasma carburising is of particular interest as it produces thicker hardened layers than plasma nitriding, and an equivalent improvement in the tribological and corrosion performance of the base material. In this project, the active screen (AS) plasma technique was used to carburise austenitic stainless steel AISI 316 and the obtained layer of carbon expanded austenite was compared with the one produced by conventional DC plasma treatments. The hardening and wear resistance produced by AS and DC plasma carburising were equivalent. With regard to corrosion, the AS treated material performed better than its DC counterpart as a consequence of the improved surface quality of the former. The mechanism of AS carburising was comparatively studied with its AS nitriding counterpart. Different experimental arrangements and two plasma diagnostic techniques were used for this purpose: optical emission spectroscopy and electrostatic probes. The evidence shows that AS nitriding relies on the deposition of iron nitrides and the active species in the plasma to produce hardening, whilst AS carburising requires the plasma activation and moderate ion bombardment.
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Tanimizu, Naoki. "Conformational properties of amino acid residues in the active site of bovine pancreatic ribonuclease A". Kyoto University, 1999. http://hdl.handle.net/2433/181366.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第7960号
農博第1069号
新制||農||785(附属図書館)
学位論文||H11||N3294(農学部図書室)
UT51-99-M265
京都大学大学院農学研究科農芸化学専攻
(主査)教授 林 力丸, 教授 池田 篤治, 教授 岩村 俶
学位規則第4条第1項該当
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Sanders, Stephen Anthony. "The effect of selected active site mutations on the properties of horseradish peroxidase isoenzyme C". Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357651.
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Seotsanyana-Mokhosi, Itumeleng. "Photosensitizing properties of non-transition metal porphyrazines towards the generation of singlet oxygen". Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1006086.
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Metallophthalocyanine complexes containing non-transition metals are very useful as sensitizers for photodynamic therapy, a cure for cancer that is based on visible light activation of tumour localized photo sensitizers. Excited sensitizers generate singlet oxygen as the main hyperactive species that destroy the tumour. Water soluble sensitizers are sought after for the convenience of delivery into the body. Thus, phthalocyanine (pc), tetrapyridinoporphyrazines (tppa) and tetramethyltetrapyridinoporphyrazines (tmtppa) with non-transition central metal atoms of Ge, Si, Sn and Zn were studied. First was the synthesis of these complexes, followed by their characterisation. The characterisation involved the use of ultraviolet and visible absorption spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, electrochemical properties and elemental analysis. Photochemical properties of the complexes were then investigated. Photolysis of these macrocycles showed two processes; -reduction of the dye and photobleaching, which leads to the disintegration of the conjugated chromophore structure of the dye. Photobleaching is the reductive quenching of the excited state of the sensitizers. The intensity of the quenching decreased progressively from tmtppa, tppa to pc metal complexes with photobleaching quantum yields, 6.6 x 10.5⁻¹, 1.8 x 10.5⁻¹ and 5.4 x 10⁻⁶ for Zntmtppa, Zntppa and Znpc, respectively. Efficiency of singlet oxygen sensitization is solvent dependent with very different values obtained for the same compound in different solvents, for example, 0.25 and 0.38 were observed as singlet oxygen quantum yields for Gepc complex in DMSO and DMF respectively. In DMSO the efficiency of ¹O₂ generation decrease considerably from pc to tppa and finally tmtppa. In water Getmtppa exhibits much higher singlet oxygen quantum yield, hence promising to be effective as a sensitizer for photodynamic therapy.
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Rafter, Stephen E. "The Optical and Radio Properties of a Low-Redshift Sample of Broad-lined Active Galactic Nuclei". Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/phy_astr_diss/39.
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The question as to whether the distribution of radio loudness in active galactic nuclei (AGN) is actually bimodal has been discussed extensively in the literature. Furthermore, there have been claims that radio loudness depends on black hole mass and Eddington ratio. We investigate these claims using the low redshift broad line AGN sample of Greene & Ho 2007, which consists of 8434 objects at z < 0.35 from the Sloan Digital Sky Survey (SDSS) Fourth Data Release. We obtained radio fluxes from the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey for the SDSS AGN. Out of the 8434 SDSS AGN, 846 have radio emission within 4" of the optical counterpart and are considered to be core emission. We also perform a systematic search for extended emission in FIRST that can be positively associated with the optical counterparts and find 51 out of the 846 previously detected core sources have extended emission that must be taken into account when calculating the total radio luminosity. Further, we find an additional 12 objects that have extended radio emission but no detectable radio core and have classic FR II type morphologies. Using these data, the question of radio bimodality and the dependence of radio-loudness on physical parameters are investigated for different subsets of the total sample. We find modest trends in the radio-loud fraction as a function of black hole mass and Eddington ratio, where the fraction of RL AGN increases for the largest black hole mass group and decreases with increasing Eddington ratio. With extended emission taken into account, we find strong evidence for a bimodal distribution in radio-loudness, where the lower radio luminosity core-only sources appear as a population separate from the extended sources with a dividing line at log(R) = 1.75. This dividing line is interesting in that it requires the radio luminosity to be 50 times the optical luminosity, ensuring that these are indeed the most RL AGN, which may have different or extreme physical conditions in their central engines when compared to the more numerous radio quiet AGN in this sample.
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Åkesson, Henrik. "Analysis of Structural Dynamic Properties and Active Vibration Control Concerning Machine Tools and a Turbine Application". Doctoral thesis, Karlskrona : Blekinge Institute of Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00452.
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Vibration in metal cutting is a common problem in the manufacturing industry, especially when long and slender tool holders or boring bars are involved in the manufacturing process. Vibration has a detrimental effect on machining. In particular the surface finish is likely to suffer, but tool life is also most likely to be reduced. Tool vibration also results in loud noise that may disturb the working environment. The first part of this thesis describes the development of a robust and manually adjustable analog controller capable of actively controlling boring bar vibrations related to internal turning. This controller is compared with an adaptive digital feedback filtered-x LMS controller and it displays similar performance with a vibration attenuation of up to 50 dB. A thorough experimental investigation of the influence of the clamping properties on the dynamic properties of clamped boring bars is also carried out in second part of the thesis. In relation to this, it is demonstrated that the number of clamping screws, the clamping screw diameter size, the screw tightening torque and the order the screws are tightened, have a significant influence on a clamped boring bar’s eigenfrequencies as well as on its mode shape orientation in the cutting speed - cutting depth plane. Also, an initial investigation of nonlinear dynamic properties of clamped boring bars was carried out. Furthermore, vibration in milling has also been studied in relation to millingtool holders with a long overhang. A basic investigation concerning the spatial dynamic properties of the tool holders of milling machines, both when not cutting and during cutting, has been carried out. Also, active control of milling tool holder vibration has been investigated and a first prototype of an active milling tool holder was implemented and tested. The challenge of transferring electrical power while maintaining good signal quality to and from a rotating object is addressed and a solution to this is proposed. Finally, vibration is also a problem for the hydroelectric power industry. In Sweden, hydroelectric power plants stand for approximately half of Sweden’s electrical power production and are also considered to be a so-called green source of energy. When renovating water turbines in small-scale hydroelectric power plants and modifying them to optimize efficiency, it is not uncommon that disturbing vibrations occur in the power plant. These vibrations have a negative influence on the production capacity and will wear various components quickly. Occasionally, these vibrations may cause severe damage to the power plant. To identify this vibration problem, experimental modal analysis and operating deflection shape analysis were utilized. To reduce the vibration problem, active control using inertial mass actuators was investigated. Preliminary results indicate a significant attenuation of the vibrations.