Relevant bibliographies by topics / Optical activity / Dissertations / Theses
To see the other types of publications on this topic, follow the link: Optical activity.

Dissertations / Theses on the topic 'Optical activity'

Author: Grafiati
Published: 4 June 2021
Last updated: 25 May 2024

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 dissertations / theses for your research on the topic 'Optical activity.'

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

Thomas, P. A. "Optical activity in crystals." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379979.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Tebbutt, Iain John. "Optical activity and crystal structure." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302911.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Murphy, Veronica L. "Optical Activity of Achiral Molecules." Thesis, New York University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10192177.

Full text
Abstract:

Optical activity is typically first introduced to a prospective chemist in her sophomore year organic chemistry course. Here, she is taught that optical activity is a consequence of chirality, for example, L-tartaric acid has a specific rotation of +12° at the sodium D-line. However, this leaves said chemist with a wildly skewed and rather vague understanding of the concept of optical activity. There are two major problems with the current understanding of optical activity. The first is that both theory and experiment have shown that optical activity is, in fact, not a consequence of chirality. Molecules belonging to one of four achiral point groups (Cs, C2 v, S4, and D 2d) can display optical activity in particular directions. However, measurement requires an anisotropic medium which presents major challenges. The second problem is that we lack structure-property relationships; specific rotations generally speaking are impossible to connect to molecular structure. Herein, we emphasize optical activity in achiral molecules whose high symmetry and simplified electronic structure are used to establish structure–property relationships. First, achiral optical activity is emphasized by showing that achiral polyaromatic hydrocarbons (PAH) are actually significantly more optically active than their helicene isomers. Next, small, planar, conjugated hydrocarbons are used to interpret optical activity by analysis of their π wave functions that can be intuited from structure. Finally, it is shown that aromaticity is generally deleterious for optical activity. A simple explanation is offered based on Kekule structures.

APA, Harvard, Vancouver, ISO, and other styles
4

Escribano, Rivero Juan Ricardo. "Studies on natural Raman optical activity." Thesis, University of Glasgow, 1985. http://theses.gla.ac.uk/8690/.

Full text
Abstract:
Optical activity associated with vibrations of chiral molecules can provide much stereochemical information. There are two techniques which observe vibrational optical activity (VOA), namely: infrared circular dichroism (IRCD) and vibrational Raman optical activity (VROA). The first, IRCD, is an extension of circular dichroism into the infrared and measures a difference in absorbance of incident left and right circularly polarized infrared radiation. VROA is concerned with a difference in the intensity of Raman scattering when the chiral system is illuminated with left and right circularly polarized radiation. Recent reviews that cover both techniques are in the references of the Summary. This thesis is divided into two main parts. The first (Chapters 1 to 4) is concerned with theoretical studies of ROA. The second (Chapters 5 to 8) with calculations of the observable parameters in VROA and their comparison with experimental results. Chapter 1 comprises a theoretical study in molecular scattering tensors: one significant new result was the discovery of a Stokes-antiStokes asymmetry in the ROA observables. In Chapter 2 is reviewed the experimental conditions in which VROA experiments have been carried out and how the artifacts will affect their spectra. For this, firstly, it has been necessary to provide a general extension of the established equations which give the ROA observables at any point in space. Subsequently a new and more realistic parameter in ROA is defined in terms of power. The difference with the original one is not important in the experimental conditions in which the spectra are recorded, but it is relevant from the scientific aesthetic point of view. Particular cases are derived from these general equations in total agreement with the original and well established ones. In all cases the influence of artifacts coming from imperfectly modulated right and left circularly polarized incident light has been considered. Chapter 3 is a generalization of the "two group model" in VROA using the bond polarizability theory. The model has been extended to include deformations of non-axially symmetric groups. A general critical revision of these formulae is provided. Chapter 4 is a survey of miscellanea in VROA. An interesting prediction is given in the case of Fermi resonance. At the end of this chapter a new selection rule is proposed in VROA which relates polarized and depolarized VROA spectra. This rule is analogous to that which relates polarized and depolarized conventional Raman spectra. The second part of the thesis is devoted to calculations of the observable parameters in VROA and their comparison with the experimental results. The molecule CBrC1FH has not yet been studied experimentally but it is a good (Chapter 5) example for calculations because the results can be compared with those from other theories such as the "atom dipole interaction model". Chapter 6 treats another easy chiral molecule, epoxypropane. The advantage of this molecule is that it can be tested with its experimental spectrum and considering the approximate force field we can say that the comparison is good. Chapters 7 and 8 deal with small chiral molecules derived from cyclohexanone, deuterated and methylated.
APA, Harvard, Vancouver, ISO, and other styles
5

Jonas, Gregory David. "On-line detection of optical activity." Thesis, Birkbeck (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286460.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Zaidi, Syed Anwar Hyder. "Optical Redox Imaging of Metabolic Activity." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1484672916027993.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Arzt, Steffi. "Measurements of optical activity and absolute optical chirality in birefringent crystals." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282424.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Matos, Gomes E. De. "Relationship between optical activity and crystal structures." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303933.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Smyth, Edward. "Raman optical activity of proteins and glycoproteins." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312130.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Lingard, R. J. "Optical activity in the presence of linear birefringence." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239284.

Full text
APA, Harvard, Vancouver, ISO, and other styles
11

Wilson, Gary. "Vibrational Raman optical activity of peptides and proteins." Thesis, University of Glasgow, 1996. http://theses.gla.ac.uk/6144/.

Full text
Abstract:
Vibrational Raman optical activity (ROA) which is the difference in the Raman scattering of left and right circularly polarised incident light, has recently emerged as a new and incisive probe of biomolecular structure. This thesis is based on new applications of ROA to some current biochemical problems. The first chapter is a brief explanation of the origin of chirality and the development of vibrational optical activity with special emphasis on ROA. Chapter 2 is a theoretical analysis of ROA and provides a fundamental explanation of the phenomenon. This involves a description as to how the ROA effect is generated using molecular property tensors. The third chapter concentrates on the instrumentation required to measure ROA and the importance of CCD detectors and holographic notch filters in establishing the technique with respect to biopolymers. Chapter 4 is a brief introduction to protein structure and includes an analysis of the strengths and weaknesses of current biophysical techniques used for structure determination. Chapters 5 and 6 describe detailed applications of ROA to polypeptides and native proteins. The polypeptides are a suitable starting point since from other spectroscopic techniques they are known to adopt certain conformations, such as -helix, -sheet and random coil. Native proteins are examined in Chapter 6 and the ability of ROA to detect not only secondary but also tertiary structure is highlighted. Chapter 7 is concerned with the important topics of the structure and dynamics of unfolded proteins, molten globules and ligand bound proteins. Finally, in the appendix there is a summary of the assignments made to secondary structure and to loops and turns.
APA, Harvard, Vancouver, ISO, and other styles
12

McColl, Iain H. "Raman optical activity studies of model polypeptide conformations." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410833.

Full text
APA, Harvard, Vancouver, ISO, and other styles
13

Zhang, Wen. "Optical activity and applications of planar chiral metamaterials." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437113.

Full text
APA, Harvard, Vancouver, ISO, and other styles
14

Syme, Christopher D. "The analysis of Raman optical activity spectra of proteins." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/5322/.

Full text
Abstract:
Measurement of the Raman optical activity (ROA) spectra of biomolecules has become an experimental possibility due to significant advances in the available technology, and its successful implementation into the ROA instruments at the University of Glasgow. The ease with which the ROA spectra of biological molecules can be successfully measured lends itself perfectly to the ever-growing demand for biomolecular structural information, especially in the context of proteomics and the Human Genome Project. ROA spectroscopy is able to probe the chiral peptide backbone of proteins, and as such the ROA spectrum of a protein contains a wealth of structural information from within the whole molecule, across the whole vibrational spectrum. As well as containing detailed information from specific structural elements such as sections of secondary structure and motifs, the ability of ROA to see the molecule as a whole also enables the global fold of the protein to be deduced from the ROA spectrum. The development of the analysis of ROA spectra has largely been based upon the correlation of ROA spectra of proteins of known structure with structural information from alternative sources, chiefly X-ray crystallography and multidimensional nuclear magnetic resonance (NMR). As the database of ROA spectra of polypeptides and proteins has grown, it has been possible to tighten up the assignment of ROA spectral bands and band patterns to aspects of known structural content. With a basis for the correlation between the ROA spectrum and the known crystal structure (or NMR structure) being well established, it is possible to interpret the ROA spectra of proteins that do not have (for whatever reason) well defined structures. This means that ROA spectroscopy can provide invaluable structural information for proteins that are precluded from analysis by other techniques, and also cast new light on the structures of proteins that have not been well defined. In order to fully interpret an ROA spectrum of a protein, it is necessary to be familiar with protein structure and the ROA experiment as a whole. Analysing an ROA spectrum is a detailed and highly subjective process. Depending on the experience of the analyst, the information contained within the spectra can be extracted readily or not so readily. For this reason, it would be desirable to develop a technique that is capable of interpreting not only individual spectra, but also whole data sets in a manner that is independent of the analyst, and therefore independent of any preconceptions (or inexperience) the analyst may have. This project presents an up-to-date collection of newly obtained ROA spectra of a large number of proteins across a range of structural class types. In addition, the statistical technique of principal component analysis (PflA) has been used as a tool for the analysis of this new data. It is hoped that the result of this work will provide a basis for the future analysis of protein ROA spectra that is both mathematically rigorous and convenient.
APA, Harvard, Vancouver, ISO, and other styles
15

Nakagawa, Harumichi, Masatoshi Yamazaki, Motoki Nihei, Ryoko Niwa, Tatsuhiko Arafune, Akira Mishima, Shiho Nashimoto, et al. "Virtual Electrode Polarization-Induced Reentrant Activity." Research Institute of Environmental Medicine, Nagoya University, 2003. http://hdl.handle.net/2237/7595.

Full text
APA, Harvard, Vancouver, ISO, and other styles
16

Fuhrmeister, Birgit. "Chromospheric and coronal activity analysing optical spectra of M dwarfs /." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976758318.

Full text
APA, Harvard, Vancouver, ISO, and other styles
17

Yoon, Young Gyu. "Optical and computational approaches for mapping brain activity and structure." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118100.

Full text
Abstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 181-189).
Neuroscience always has been a heavily technology-starved field that has been often revolutionized with the rise of a new technology; and arguably the future advancement of neuroscience will also depend largely on the development of new technologies that allow acquiring new data sets that can provide deeper insights into the brain. While there is no universal agreement as to what data sets are needed to fully reveal the underlying principles of brain computation, neurons will certainly serve as an important layer to study the brain considering their discreteness and electrical characteristics. In other words, seeing a brain as a circuitry that is made of the neurons, it is important to study the relation between the brain's structure and its function at the neuronal level. Unfortunately, a brain is a huge network that consists of a huge number of neurons which makes it difficult to see the "big picture" while retaining the single neuron resolution. The aim of this study is to the develop such technologies that allow to see and analyze the large network's structure and dynamics with the single neuron resolution. The core strategy is to use optical microscopy to acquire the raw data and to infer the information of our interests with computational techniques with designing both optical and computational parts with each other in mind to maximize the synergy. The first part of the thesis describes the development and application of computational imaging techniques to monitor the brain activity in 3-D which allowed us to see how the neurons interact at an unprecedented speed. The second part describes a computational approach to extract a wiring diagram of a brain from an optical image of the brain rather than an electron microscopy image, as optical microscopy is undergoing rapid development and is likely to outperform electron microscopy in terms of scalability which will be an important criterion to map the whole brain. These will be the tools of great utility in neuroscience that can generate rich data sets that will be of wide interests to system neuroscientists as well as cellular/molecular neuroscientists.
by Young Gyu Yoon.
Ph. D.
APA, Harvard, Vancouver, ISO, and other styles
18

Amanna, Ashwin E. "Optical method of recording electrical activity in isolated rabbit hearts." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10312009-020219/.

Full text
APA, Harvard, Vancouver, ISO, and other styles
19

Hough, Loren E. "Layer curvature and optical activity in bent core liquid crystalline phases." Connect to online resource, 2007. 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:3256461.

Full text
APA, Harvard, Vancouver, ISO, and other styles
20

Mackinnon, Jonathan AG. "A novel biosensor for the long-term optical integration of neuronal activity." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-147018.

Full text
APA, Harvard, Vancouver, ISO, and other styles
21

Wong, S. "A fast webcam photogrammetric system to support optical imaging of brain activity." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1344106/.

Full text
Abstract:
Optical topography (OT) is an emerging neuroimaging technique utilising the tight coupling between neural activity and regional cerebral blood flow to monitor relative regional changes of haemoglobin concentration. OT systems are compact, low cost, easily portable, and relatively tolerant of body movements enabling clinical diagnosis, psychological experiments and even monitoring brain activities during daily living. There is a requirement for such systems to present their output functional data in a brain model based coordinate space in order to map to the signal source with brain anatomy. However OT data are obtained from a network of OT sensing devices (optodes) placed in contact with the head surface and cannot capture structural information of the underlying brain which might otherwise be used for registration. An appropriate registration method, widely used in Electroencephalography (EEG), is the 10-20 system which utilises bony landmarks as common points to co-register locations on the scalp with a brain model to a repeatability of a few millimetres in clinical applications to an MRI set of reference points. Inheriting the low cost and portability of OT, this thesis develops and validates a novel registration approach utilising off-the-shelf webcam technology in combination with photogrammetric bundle adjustment techniques in order to reliably coordinate targets on optodes and bony landmarks within the 10:20 reference frame to an accuracy of better than 1mm. Initial research includes an assessment of the 3D coordination accuracy, precision and stability of a series of low cost webcams in order to prove their suitability for clinical applications. Results demonstrate the capability of a system based on these cameras to reliably coordinate 3D target locations to the order of 0.5mm and better. Difficulties in automated clinical target image extraction due to poor image quality are circumvented through the development of new target image detection methods. Incremental improvements in image quality from successive webcam generations, up to and including the latest HD systems, are shown to increase coordination accuracy by one order of magnitude. The result is a novel webcam photogrammetric system that is able to rapidly and consistently coordinate targets on optodes and bony landmarks to better than 1mm in OT studies and is able to take advantage of the rapid advances being made in consumer webcam technology. The system is proven in pre-clinical studies to evaluate its coordination accuracy and in simulated clinical OT studies with a head-sized phantom conducted in collaboration with Department of Medical Physics and Bioengineering. Clinical OT studies with human subjects, demonstrate the capability of the system to continuously coordinate targets on optodes and scalp and detect differential movement between optodes and scalp which would invalidate a static registration procedure.
APA, Harvard, Vancouver, ISO, and other styles
22

Boeheim, Jamie Lynn. "Human activity recognition using limb component extraction /." Online version of thesis, 2008. http://hdl.handle.net/1850/7764.

Full text
APA, Harvard, Vancouver, ISO, and other styles
23

Thurston, Mark Robert. "X-ray and optical observations of the young open cluster NGC 2516." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366165.

Full text
APA, Harvard, Vancouver, ISO, and other styles
24

Rioult-Pedotti, Marc Guy. "Optical multisite recording of neural activity patterns in organotypic spinal cord tissue cultures /." [S.l.] : [s.n.], 1991. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9393.

Full text
APA, Harvard, Vancouver, ISO, and other styles
25

Lai, Lo Ming. "Synthesis, optical activity, and liquid crystallinity of polyacetylenes containing naturally occurring building blocks /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202006%20LAI.

Full text
APA, Harvard, Vancouver, ISO, and other styles
26

Rothmeier, Greggory H. "Brain tissue temperature dynamics during functional activity and possibilities for optical measurement techniques." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/phy_astr_theses/14.

Full text
Abstract:
Regional tissue temperature dynamics in the brain are determined by the balance of the metabolic heat production rate and heat exchange with blood flowing through capillaries embedded in the brain tissue, the surrounding tissues and the environment. Local changes in blood flow and metabolism during functional activity can upset this balance and induce transient temperature changes. Invasive experimental studies in animal models have estab- lished that the brain temperature changes during functional activity are observable and a definitive relationship exists between temperature and brain activity. We present a theoreti- cal framework that links tissue temperature dynamics with hemodynamic activity allowing us to non-invasively estimate brain temperature changes from experimentally measured blood- oxygen level dependent (BOLD) signals. With this unified approach, we are able to pinpoint the mechanisms for hemodynamic activity-related temperature increases and decreases. In addition to these results, the potential uses and limitations of optical measurements are dis- cussed.
APA, Harvard, Vancouver, ISO, and other styles
27

Camphouse, R. Chris. "Modeling and Numerical Approximations of Optical Activity in the Chemical Oxygen-Iodine Laser." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28640.

Full text
Abstract:
The chemical oxygen-iodine laser (COIL) has several important military and industrial applications. The concern of this work is do develop a partial differential equation model describing optical behavior in the COIL. Optical behavior of the COIL has traditionally been investigated via a ray tracing method. Photons are represented as discrete particles, and their behavior is described by the geometry of the system. We develop an optical model wherein photons have a wave description. In order to construct the mathematical model, we utilize the theory of paraxial wave optics and Gaussian beams. Doing so allows us to incorporate physical effects such as diffusion/diffraction and refraction into the model. After describing the optical model, we present numerical methods for obtaining approximate solutions to the model in the cases of one and two transverse directions. Results are presented illustrating the efficacy of the numerical methods.
Ph. D.
APA, Harvard, Vancouver, ISO, and other styles
28

Ballerini, Paola. "Effects of starspots activity on optical and near infrared observations of planetary transits." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1377.

Full text
Abstract:
In this thesis, I report on the effects that magnetic stellar activity of solar-type stars induces on stellar light curves involved in the photometric technique for the detection and characterization of transiting extra-solar planets that is one of the most effective detection methods, the first being the radial velocity technique. Stellar magnetic activity is a source of noise in the study of the transits of extra-solar planets since it induces flux variations that significantly affect the transit depth determination and the derivations of planetary and stellar parameters. Surface brightness inhomogeneities, such as starspots or bright faculae, on star disc have an intrinsic dependence on wavelength and thus on the stellar colours. The colour dependence of stellar activity may significantly influence the characterization of planetary atmospheres since it produces stellar flux variations that may mimic those due to the presence of molecular or atomic species in the transmitted planetary spectra. In this thesis I focus on the effects due essentially to stellar spots present in the visible hemisphere of solar-type stars. The proposed method is a theoretical one, aiming to predict the starspot-induced effects with the use of stellar atmospheric models and I present a systematic approach to quantify the corresponding stellar flux variations as a function of wavelength bands. Therefore I consider a star with spots covering a given fraction of its disc and model the variability in both the UBVRIJHK photometric system and the Spitzer/IRAC wavebands for dwarf stars from G to M spectral types. Then I compare starspot-induced flux variations in these different passbands with planetary transits and quantify how they affect the determination of the planetary radius and the analysis of the transmission spectroscopy in the study of planetary atmospheres. My results suggest that the monitoring of the systems by using broad-band photometry, from visible to infrared, helps to constrain spots effects by estimating the R parameter, i.e. the ratio of the relative variations in the stellar fluxes at short wavelength optical bands (e.g., U or B) to near-infrared ones (e.g., J or K). Its numerical value can be used to distinguish starspot brightness dips from planetary transits in a single stellar light curve. In addition to the perturbations in the measurement of the planetary radius, the perturbations in the transit light curve profiles due to starspots can affect the determinations of orbital parameters, i.e., the relative semi-major axis and the inclination of the planetary orbit, that are directly derived by fitting procedure of the transit light curves. These distortions in the transit light curves have a significant impact on the derivation of stellar parameters and, above all, on the stellar density thus bothering the stellar evolutionary estimates. The results derived from the synthetic photometric analysis are presented and discussed in Ballerini et al. 2012.
APA, Harvard, Vancouver, ISO, and other styles
29

Srinivasan, Geetha. "Characterization of neuronal activity in the auditory brainstem of rats an optical imaging approach /." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971872821.

Full text
APA, Harvard, Vancouver, ISO, and other styles
30

Zangui, Soumya. "The application of time-domain spectroscopy to the study of optical activity in metamaterials." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669045.

Full text
Abstract:
The terahertz time-domain spectroscopy (TDS) technique which combines broadband and highly sensitive coherent detection with time revolution and strong immunity to background has found application in a wide range of fundamental disciplines. This work presents the development of a polarisation resolved THz-TDS spectrometer that enables sensitive studies of the optical activity of chiral metamaterials in the terahertz frequency range. The thesis is divided into two principal parts. The first (chapters 2 to 4) describes the principles of the time-domain spectroscopy. This is followed by descriptions of a crossed-bowtie antenna which simultaneously detects both orthogonal field components and devices for measuring the state of polarisation of THz waves. In particular we present experimental and computational studies of four linear polarisers. One is a pile-of-plates which relies on the different reflectivity of s and p-polarised light incident on a dielectric surface at Brewster’s angle and the others are wire-grids of different dimensions and different substrates which rely on the anisotropic conductivity of thin metal wires. The design of the polarisation resolved spectrometer and a formalism for describing optical activity and analysis data are then described in the fourth chapter. The second part of the thesis describes applications of the polarisation sensitive terahertz TDS system to the study of optical activity exhibited by artificial materials. Four structures have been studied in this work; metal screw hole arrays, quasi-two-dimensional gammadions and Archimedean spiral metamaterials and a quasi-three-dimensional array of spirals. Experimental and computational studies of the polarisation characteristics and the optical properties of these structures are discussed in chapters 5, 6 and 7.
APA, Harvard, Vancouver, ISO, and other styles
31

Fan, Zhiyuan. "Optical Activity of Chiral Nanomaterials: Effects of Short Range and Long Range Electromagnetic Interactions." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1394998277.

Full text
APA, Harvard, Vancouver, ISO, and other styles
32

Dunmire, David Allen. "Experimental and theoretical measurements of vibrational circular dichroism and instrumental development of Raman optical activity." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2002. http://wwwlib.umi.com/cr/syr/main.

Full text
APA, Harvard, Vancouver, ISO, and other styles
33

Lizio, Maria Giovanna. "Exploring peptide foldamer-membrane interactions using optical spectroscopic techniques." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/exploring-peptide-foldamermembrane-interactions-using-optical-spectroscopic-techniques(694db937-1fb6-430d-98af-ba147c857e6e).html.

Full text
Abstract:
The evolution of drug resistant pathogens creates the need for the introduction of new antimicrobial drugs. Peptaibols, a class of naturally occurring peptides, contain large amounts of alpha aminoisobutyric acid (Aib). They are known to exhibit their antimicrobial activity by perturbing the membranes of pathogens. However, a comprehensive model of action for these peptides has not yet been identified. Aib residues support the formation of 310-helix conformation and it is thought that this secondary structure is important for their antimicrobial activity. It is possible to design small synthetic peptides, known as foldamers, endowed with specific properties; in particular, Aib-rich foldamers are used as a model for the understanding of the folding and membrane interaction of the naturally occurring species. The aim of this thesis is to investigate the conformational preference of monodisperse Aib-oligomers as well as understanding their interaction with bilayer membranes. A large set of spectroscopic techniques have been used to establish the conformation of Aib-rich foldamers both in solution and when bound to membranes. In particular: Raman, Raman Optical Activity (ROA), Infrared (IR), Vibrational Circular Dichroism (VCD), Linear Dichroism (LD) and Neutron Scattering (NR) were employed to provide new structural insights. These vibrational analysis (VA) and vibrational optical analysis (VOA) investigations in solution were focused on the identification of spectral features for 310-helix conformation, particularly with Raman and Raman Optical Activity spectroscopies. Spectroscopic markers for this conformation in the amide I region were successfully identified. Moreover, it is known that chiral Aib-rich peptides can show a right or left handed screw-preference based on the primary sequence. VOA studies successfully distinguished between peptides with opposite helicity. VCD, ROA, LD and NR of Aib-foldamers bound to membranes were shown to be useful for identification of conformational preferences of the peptides within the membrane as well as for determining their orientation in the bilayer, and ultimately the effect of the peptides on the membrane structure.
APA, Harvard, Vancouver, ISO, and other styles
34

Jin, Lei Verfasser], Andreas [Akademischer Betreuer] Offenhäusser, and Marc [Akademischer Betreuer] [Spehr. "Optical control of primary rat cortical neural activity in vitro / Lei Jin ; Andreas Offenhäusser, Marc Spehr." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130590542/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
35

Hobro, Alison J. "Structural investigations of RNA through the application of Raman, Raman optical activity and surface enhanced spectroscopies." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491481.

Full text
Abstract:
RNA molecules are involved in a wide range of cellular processes from genetic coding to catalytic activities, and determination of their secondary and tertiary structures is essential for the understanding of their functions. The work presented in this thesis shows the structural information that can currently be obtained using Raman and ROA spectroscopies for nucleic acid components and RNA molecules. Raman and ROA spectra can be used to identify particular building blocks, for example, with some marker bands characteristic for mono- and tri-nucleotides. In oligonucleotides and RNA sequences, Raman is particularly sensitive to the environment of the bases, while ROA is most sensitive to the conformation of the ribose-phosphate backbone. Therefore this complementary information can be used to identify single base changes and the introduction of a bulge sequence in the EMCV IRES Domain I, as well as allow tentative identification of structural features within the Adenovirus VA RNAr. Moreover, perturbation induced changes can also be monitored using Raman spectroscopy. Results presented here show these studies can be used to identify changes in specific parts of the molecule with particular temperatures, as well as identifying particular changes in secondary and/or tertiary structure with other perturbations, such as Mg2+ concentrations. The main limitation for ROA studies of RNA is the requirement for relatively high concentrations and long data collection times which can limit the range of RNA molecules that can be studied. Surface enhanced spectroscopic techniques can reduce the sample concentration and data collection requirements through the interaction of a molecule with surface plasmons associated with a nanoscale· roughened metal surface. The second half of this thesis concentrates on the implications of surface enhancement for Raman (SERS) and ROA (SEROA) studies of RNA. The application of SERS to RNA appears to be more complex than for other analyte species because the enhancement process is strongly time dependent. This, together with the spectral profile, can be influenced by a number of factors, including the nature of the aggregating agent and the concentration of the reagents involved. The effects of changes of these variables on the spectral profile and the time dependence of SERS enhancement are presented and discussed in the context of physical changes occurring during the experiment. Overall, Raman and ROA studies of RNA have provided information about the secondary and tertiary structures of RNA molecules despite their varying conformations and transitions, a matter that can be complicated for high-resolution techniques, such as X-ray crystallography. Surface enhanced Raman studies of RNA can, with careful preparation, provide meaningful results whilst reducing sample concentration requirements. However, the processes involved in generating surface enhanced ROA spectra appear to be significantly more complex and, for nucleic acid components, SEROA has not been successfully measured.
APA, Harvard, Vancouver, ISO, and other styles
36

Jin, Lei [Verfasser], Andreas Akademischer Betreuer] Offenhäusser, and Marc [Akademischer Betreuer] [Spehr. "Optical control of primary rat cortical neural activity in vitro / Lei Jin ; Andreas Offenhäusser, Marc Spehr." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130590542/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
37

Pickering, Jon W. "Applications of Optical Properties from Nanomaterials for Enhanced Activity of a Titania Photocatalyst under Solar Radiation." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5760.

Full text
Abstract:
In recent years, employing advanced oxidation processes (AOPs) as a means of wastewater remediation has emerged as a promising route towards maintaining a sustainable global water management program. The heterogeneous photocatalytic oxidation process has been of particular interest due to the prospective of utilizing solar radiation as the driving force behind the degradation of pollutants. Of the photocatalyst studied to date, TiO2 remains the most attractive material for environmental applications due to its affordability, stability, biocompatibility and high quantum yield. A key draw back however is roughly only 5% of solar radiation incident on earth can provide the energy required (3.0-3.2 eV) to generate the electron-hole pairs necessary for photo-oxidation. As a means to improve the process under solar irradiance, optical properties such as surface plasmon resonance of metallic nanoparticles and upconversion luminescence of rare earth ions have been exploited for improved light harvesting as well as the generation of more usable UV light from lower energy photons. In order to explore these phenomena and their role in the enhancement of this AOP, the photocatalytic degradation of organic dyes was studied under various conditions employing Degussa P25 TiO2 as the photocatalyst. Ag nanocubes, Ag-Pd core-shell nanoparticles and YAG:Yb+3,Er+3 served as the dopants for the various studies which resulted in enhanced degradation rates, insight into the applicability of utilizing Yb+3 as sensitizing ion under solar radiation and a novel core-shell nanoparticle synthesis.
APA, Harvard, Vancouver, ISO, and other styles
38

Noeske, Kai Gerhard. "Optical and near infrared studies of the photometric structure and starburst activity of blue compact dwarf galaxies." Doctoral thesis, [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969518021.

Full text
APA, Harvard, Vancouver, ISO, and other styles
39

Jones, Nathaniel. "In Vivo Characterization of Cortical Noradrenergic Activity During Motor Learning Using an Optical Noradrenaline Sensor in Mice." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41027.

Full text
Abstract:
The locus coeruleus (LC) projects ubiquitously to the cortex, and noradrenaline (NA) exerts powerful neuromodulatory control on cortical excitation and inhibition. Previous work has shown that NA plays an important role in motor processes, and further posits that dysregulation in NA function could be one of the culprits of motor-related deficits in many neurodevelopmental disorders, including Autism Spectrum Disorder. In order to characterize the change in NA levels during motor learning in awake and behaving mice, I employed a newly developed optical NA sensor, combined with in vivo two-photon imaging, to visualize spatiotemporal activation patterns of NA in the motor cortex. This experimental approach allows us to track and chronically image the same region of the motor cortex over multiple days, thus permitting the characterization of NA activity throughout the entirety of the motor learning process. I found that NA levels increase significantly during the initial phase of learning, which coincides with the structural and functional plastic changes that have been previously reported in the motor cortex during early stages of motor learning. The NA activity returns to baseline levels as the mice develop their movement strategy; however, the regions of NA release become more spatially clustered during the learning process. The results reported in this thesis provide a novel glimpse into the dynamics of NA activity in the motor cortex during motor learning, and it will provide new direction for the development of therapeutic strategies and diagnostic criteria for motor-related dysfunction in neurodevelopmental diseases.
APA, Harvard, Vancouver, ISO, and other styles
40

Bray, Natasha. "IL-1β-mediated changes in cerebral perfusion and neural activity in a rat model of neuroinflammation and excitotoxicity." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/il1mediated-changes-in-cerebral-perfusion-and-neural-activity-in-a-rat-model-of-neuroinflammation-and-excitotoxicity(f9784ec8-0438-4d3c-aef1-b56a9b86ac01).html.

Full text
Abstract:
Neuroinflammation is a major driver of secondary brain cell death after ischaemic stroke, seizure activity and traumatic brain injury. In a model of excitotoxic neuroinflammation, striatal injection of a toxic dose of AMPA causes cell death in the striatum after 24 hours. Co-injection of AMPA with the pro-inflammatory cytokine interleukin-1β (IL-1β) leads to additional cortical cell death. Injected alone, IL-1β leads to little or no cell death. It is hypothesised that IL-1β may exacerbate cell death by interfering with blood flow coupling. In the first study, two-dimensional optical imaging spectroscopy was used to measure early changes in the haemodynamic response in the anaesthetised rat barrel cortex before and for 6 hours after injection of vehicle, AMPA, IL-1β, or AMPA+IL-1β. After injection of IL-1β, with or without AMPA, the oxygenated blood flow response to mechanical whisker stimulation approximately halved over the course of 6h. In the second study, to determine whether the IL-1β-dependent changes in blood flow response are reflected by altered cellular activity, local field potentials, multi-unit activity and local tissue oxygenation responses to whisker stimulation were recorded simultaneously from the active barrel before and up to 6h after injection. A similar reduction in the size of the oxygenation response was seen again in the IL-1β- and AMPA+IL-1β-treated groups. Importantly, the level of gamma frequency oscillations at stimulus onset decreased within the first hours after injection of AMPA+IL-1β or IL-1β, suggesting a disruption of the fast-spiking interneuron network in the barrel cortex. These findings, along with histological observations of IL-1β-dependent markers of neuroinflammation, suggest that IL-1β may exacerbate AMPA-induced excitotoxicity by potentiating seizure activity and decoupling the neurovascular response in the cortex.
APA, Harvard, Vancouver, ISO, and other styles
41

Sable, Jeffrey J. "Electrical and optical investigations of event-related brain activity in human auditory cortex elicited by rapidly presented tones /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115587.

Full text
APA, Harvard, Vancouver, ISO, and other styles
42

Annan, Bernard Derek. "Optical modulation of high-affinity biomolecules function via photochromic dyes : a step towards an artificial control of biological activity." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/4438.

Full text
Abstract:
Prior to this study, there has yet to be a clear demonstration of an artificial control of antibody affinity via photochromic dyes. The research described in this thesis sets out to address this by investigating photochromic dyes and their subsequent applications with high affinity biomolecules - primarily to photomodulate the functions of biomolecules. The main avenue of investigation explored the conjugation of photochromic dyes (spiropyrans) to proteins (an enzyme and five different antibodies), to achieve reversible photomodulation of protein function for possible applications in biosensor technology (such as the development of reagentless bio¬reversible sensing systems). A secondary aim involved the investigation of the feasibility of antibody-antigen binding in the presence of ionic liquids. Ionic liquids have recently experienced growing interest as replacements for traditional organic solvents in a number of industrial applications. The practicability of spiropyrans in ionic liquids was also investigated (with the future possibility of photomodulated antibody-antigen interactions in ionic liquids to deliver a variety of improved analytical performances). The synthesis and photoswitching properties of an appropriate range of spiropyran dyes are reported. The spiropyran dyes are synthesised to possess a carboxyl group to aid carbodiimide mediated conjugation to lysine amino groups of proteins. The photochromic behaviour of the spiropyran dyes in various solvents, temperature and pH ranges were observed. Conjugation of carboxylated spiropyran dyes to an enzyme: horseradish peroxidise, was initially observed to aid development of experimental protocol for the target study group i.e. antibodies. Photomodulation of the modified horseradish peroxidase was found to demonstrate ~ 60 % decline in enzyme activity, an effect which was reversible as a result of the photoswitching capabilities of the attached spiropyran dyes. The five different antibodies; anti Atrazine, anti GroEL, anti Phytanic Acid, anti FITC and anti Staphylococcus aureus were modified with spiropyran dyes as with horseradish peroxidase. Reversible antibody affinity photomodulation was observed via their reaction in an ELISA which yielded a decline of ~ 15 %, ~ 40 %, ~ 50 %, ~ 55 % and ~ 65 % in binding signal respectively. A fatigue assessment was conducted on the photoswitching capabilities of both the conjugated and the unconjugated spiropyran dyes. This was expressed as ten photoswitching cycle experiments, the first evenly spaced over ten days and a second over ten weeks. The initial results suggested dye degradation increased with consecutive photoswitching cycles of the conjugated spiropyran dyes. It was observed that the level of degradation for the unconjugated spiropyran dyes was independent to the timing interval between photoswitching cycles, suggesting storage stability of the compound. However the level of degradation for the conjugated spiropyran dyes was dependent to the timing interval between photoswitching cycles, suggesting storage instability. A subsequent study involved the demonstration of the feasibility of antibody-antigen binding in ionic liquids for the first time. Various combination ratios of ionic liquids with aqueous phosphate buffered saline were employed. Initial experimentation of antibody-antigen binding showed that use of solutions with an ionic liquid content of 50 % and below, produced identical results to that of the standard aqueous phosphate buffered saline. At 95 % ionic liquid content, a lower level of binding activity was observed. The possibility of a photomodulated antibody-antigen interactions in ionic liquids did not produce a significant result on this occasion with the observation of spiropyran dyes failure to photoswitch in solutions with as low as 10 % ionic liquid content. In summary, although the development of a reagentless bio-reversible sensing system continues beyond the period of this PhD thesis, significant progress has been made with regards to photochromic antibodies as possible candidates for further studies and applications, also the establishment of antibody-antigen binding in various ionic liquids can serve as ways to further enhance the applicability of such reactions under different environmental conditions.
APA, Harvard, Vancouver, ISO, and other styles
43

Mackinnon, Jonathan A. G. [Verfasser], and Oliver [Akademischer Betreuer] Griesbeck. "A novel biosensor for the long-term optical integration of neuronal activity / Jonathan A. G. Mackinnon. Betreuer: Oliver Griesbeck." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1025224353/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
44

Gong, Zhijun, and 龚志军. "Application of optical dating to late quaternary uplift and thrust activity in the northern piedmont of Tian Shan, China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hdl.handle.net/10722/193394.

Full text
Abstract:
Tian Shan is one of the most important orogenic belts in central Asia. It has been reactivated as a result of the Cenozoic India-Eurasia collision. Dating of the late Cenozoic tectonic deformation of Tian Shan and its piedmonts is important for understanding the mountain building as well as evaluating seismic hazards in the region. This study is focused on the applications of optical dating to the late Quaternary uplift and thrust activity along Manas River, in the northern piedmont of the Tian Shan, China. The sediments on river terraces were dated with optical dating. The elevations were measured with the kinematic global position system (GPS). The results suggest that two phases can be identified according to the significantly different river incision rates. One phase was from ~20 ka to ~4.8 ka, with a much slower incision rate of ~ 2.2 ± 0.6 mm/yr. The other phase was from ~4.8 ka to present, with a faster incision rate of ~ 13.5 ± 0.6 mm/yr. The accelerated incision rate of Manas River was mainly attributed to the tectonic forces, suggesting that the tectonic uplift was significantly intensified since ~4.8 ka in the northern piedmont of Tian Shan. The study region has suffered from multiple thrust activities during the late Quaternary, which led to the intensive deformations of the river terraces. By studying the deformed terraces, I evaluated the timing of the past thrust activities as well as the vertical slip rate of the thrust faults. The results demonstrated that the thrust activity intensified during the late Holocene, as manifested by the more frequent thrust activities and higher vertical slip rates. Both quartz and potassium feldspar can be as dosimeters for optical dating of sediments. However, quartz OSL is sometimes seriously impeded with problems such as very dim signals and insufficient bleaching problems. K-feldspar has attractive advantages over quartz, despite of problem of anomalous fading. K-feldspar was explored in this study, by investigating the relationship between the infrared stimulated luminescence (IRSL) and blue light stimulated luminescence (BLSL) signals. For IRSL and BLSL at 60 °C, it was suggested that most of the IRSL could be bleached by blue light (BL), while the BLSL could only be partially bleached by infrared (IR) stimulation. Besides, the fast and medium components of BLSL were mainly associated with the IRSL. If IR stimulation temperature was raised from 60 to 200 °C, at least two portions of the IRSL signals at 200 °C were observed. One portion could be bleached by BL at 60 °C and the other portion was hardly bleached by BL at 60 °C. Dating of K-feldspar from the various signals provided cross-checking for the reliability of quartz OSL for dating sedimentary samples.
published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
APA, Harvard, Vancouver, ISO, and other styles
45

Kinalwa-Nalule, Myra. "Using machine learning to determine fold class and secondary structure content from Raman optical activity and Raman vibrational spectroscopy." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/using-machine-learning-to-determine-fold-class-and-secondary-structure-content-from-raman-optical-activity-and-raman-vibrational-spectroscopy(7382043d-748c-4d29-ba75-67fb35ccdb19).html.

Full text
Abstract:
The objective of this project was to apply machine learning methods to determine protein secondary structure content and protein fold class from ROA and Raman vibrational spectral data. Raman and ROA are sensitive to biomolecular structure with the bands of each spectra corresponding to structural elements in proteins and when combined give a fingerprint of the protein. However, there are many bands of which little is known. There is a need, therefore, to find ways of extrapolating information from spectral bands and investigate which regions of the spectra contain the most useful structural information. Support Vector Machines (SVM) classification and Random Forests (RF) trees classification were used to mine protein fold class information and Partial Least Squares (PLS) regression was used to determine secondary structure content of proteins. The classification methods were used to group proteins into α-helix, β-sheet, α/β and disordered fold classes. The PLS regression was used to determine percentage protein structural content from Raman and ROA spectral data. The analyses were performed on spectral bin widths of 10cm-1 and on the spectral amide regions I, II and III. The full spectra and different combinations of the amide regions were also analysed. The SVM analyses, classification and regression, generally did not perform well. SVM classification models for example, had low Matthew Correlation Coefficient (MCC) values below 0.5 but this is better than a negative value which would indicate a random chance prediction. The SVM regression analyses also showed very poor performances with average R2 values below 0.5. R2 is the Pearson's correlations coefficient and shows how well predicted and observed structural content values correlate. An R2 value 1 indicates a good correlation and therefore a good prediction model. The Partial Least Squares regression analyses yielded much improved results with very high accuracies. Analyses of full spectrum and the spectral amide regions produced high R2 values of 0.8-0.9 for both ROA and Raman spectral data. This high accuracy was also seen in the analysis of the 850-1100 cm-1 backbone region for both ROA and Raman spectra which indicates that this region could have an important contribution to protein structure analysis. 2nd derivative Raman spectra PLS regression analysis showed very improved performance with high accuracy R2 values of 0.81-0.97. The Random Forest algorithm used here for classification showed good performance. The 2-dimensional plots used to visualise the classification clusters showed clear clusters in some analyses, for example tighter clustering was observed for amide I, amide I & III and amide I & II & III spectral regions than for amide II, amide III and amide II&III spectra analysis. The Random Forest algorithm also determines variable importance which showed spectral bins were crucial in the classification decisions. The ROA Random Forest analyses performed generally better than Raman Random Forest analyses. ROA Random Forest analyses showed 75% as the highest percentage of correctly classified proteins while Raman analyses reported 50% as the highest percentage. The analyses presented in this thesis have shown that Raman and ROA vibrational spectral contains information about protein secondary structure and these data can be extracted using mathematical methods such as the machine learning techniques presented here. The machine learning methods applied in this project were used to mine information about protein secondary structure and the work presented here demonstrated that these techniques are useful and could be powerful tools in the determination protein structure from spectral data.
APA, Harvard, Vancouver, ISO, and other styles
46

Rackham, Benjamin, Néstor Espinoza, Dániel Apai, Mercedes López-Morales, Andrés Jordán, David J. Osip, Nikole K. Lewis, et al. "ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623098.

Full text
Abstract:
GJ. 1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanet 's atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260 angstrom) of GJ. 1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of Rp R-s = 0.1146. 2 x 10(-4) and mean uncertainty of sigma(R-p/R-s) = 8.7 x 10(-4) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanet's limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r = 0.1 mu m and haze-forming efficiency f(haze) = 10% and (2) faculae in the unocculted stellar disk with a temperature contrast Delta T= 354(-46)(+46) K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.
APA, Harvard, Vancouver, ISO, and other styles
47

Srinivasan, Anandi. "Paramagnetic extended metal atom chains : synthesis, structures, magnetic properties and chiro-optical studies." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0734.

Full text
Abstract:
Cette thèse décrits la synthèse et caractérisations de chaines métalliques étendues (EMACs:extended metal atom chains) construite à partir des ligands dipyridylamine (dpa) etdipyridylformamidinate (DpyF). Le Chapitre I fait une brève introduction sur les liaisons métalmétalet sur les chaines métalliques étendues. Le Chapitre II présente les propriétés de conversionde spin (SCO: spin crossover) d’une série d’EMACs de tris-cobalt de formule générale[Co3(dpa)4X2]. L’influence des ligands axiaux et de la symétrie des molécules a été examinée etcorrélée aux propriétés de conversion de spin. Le Chapitre III porte sur la résolutionénantiomérique et activité RX optique de l’EMAC tris-cobalt [Co3(dpa)4(MeCN)2]2+. Dans lechapitre IV, La chimie de coordination du ligand N,N’-di(2-pyridyl)formamidinate (DpyF), quiconduit à des complexes présentant des propriétés structurales and magnétiques remarquable,est explorée. Finalement, le chapitre V présente nos études préliminaires pour obtenir despolymères unidimensionnelles d’EMAC de tris-cobalt en utilisant des radicaux de type thiazyle
This thesis describes the synthesis and characterizations of extended metal atom chains (EMACs)supported by dipyridylamine (dpa) and dipyridylformamidinate (DpyF) ligands. Chapter Iprovides a brief introduction to metal-metal bonds and extended metal atom chains. In Chapter IIspin crossover properties of series of tricobalt EMACs based on [Co3(dpa)4X2] motifs arepresented. The influence of the axial ligands and the symmetry of the molecule was examined andcorrelated with the SCO properties. Chapter III describes the enantiomeric resolution and X-rayoptical activity of tricobalt EMAC, [Co3(dpa)4(MeCN)2]2+. In chapter IV, the coordination chemistryof N,N’-di(2-pyridyl)formamidinate, (DpyF) is explored, a ligand which gives rise to complexeswith remarkable structural and magnetic properties Finally, chapter V presents our initial effortsto obtain one-dimensional coordination polymers of tricobalt EMAC using thiazyl radicals
APA, Harvard, Vancouver, ISO, and other styles
48

Rodgers, Bernadette. "What's happening around Herbig Ae stars? : investigating circumstellar activity in young intermediate mass stars with optical and near-infrared spectroscopy /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5431.

Full text
APA, Harvard, Vancouver, ISO, and other styles
49

Silva, Sinhara Rishi Malinda. "Manipulating Electromagnetic waves with enhanced functionalities using Nonlinear and Chiral Metamaterials." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7443.

Full text
Abstract:
Metamaterials are artificial structures, which periodically arranged to exhibit fascinating electromagnetic properties, not existing in nature. A great deal of research in the field of metamaterial was conducted in a linear regime, where the electromagnetic responses are independent of the external electric or magnetic fields. Unfortunately, in linear regime the desired properties of metamaterials have only been achieved within a narrow bandwidth, around a fixed frequency. Therefore, nonlinearity is introduced into metamaterials by merging meta-atoms with well-known nonlinear materials. Nonlinear metamaterials are exploited in this dissertation to introduce and develop applications in microwave frequency with broadband responses. The nonlinearity was achieved via embedding varactor diode on to split ring resonator (SRR) design, which demonstrates tunability in resonance frequency and phase of the transmission signal. SRR exhibits power and frequency dependent broadband tunability and it is realized for external electro-magnetic signals. More importantly, the nonlinear SRR shows bi-stability with distinct transmission levels, where the transition between bi-states is controlled by the impulses of pump signal and it can be used as a switching device in microwave regime. In order to increase its functionality in other frequencies, a new design, double split ring resonator (DSRR) is introduced with two rings, which has two distinct resonance frequencies. The double split ring resonator also demonstrate similar behavior as the SRR but it is broadband. Furthermore, by designing the structure such that the inner ring has a frequency twice as outer ring resonance frequency; we observed the enhancement of harmonic generation. We exhibit enhancement in second harmonic generation and methods that can use to increase the harmonic signal power. Arranging the unit cells in an array and particular orientation further increases the harmonic power. In addition, we show that using a back plate to create a cavity will help to increase harmonic power. Furthermore, we have demonstrated that applying an external DC voltage can be used to tune resonance frequency as well as phase of the signal. Exploring these ideas in THz frequency regime is also important. So simulation results were obtained with advanced designs to achieve non-linearity in terahertz frequency regime to realize tunability, hysteresis and bi-stable states. A negative refractive index can be realized in metamaterials consisting of strong magnetic and electric resonators with responses at the same frequency band. However, high loss and narrow bandwidth resulting from strong resonances have impeded negative index optical components and devices from reaching expected functionalities (e.g. perfect lens). Here, we demonstrate experimentally and numerically that a 2D helical chiral metamaterial exhibits broadband negative refractive index with extremely low loss. With Drude-like dispersion, its permittivity leads to zero-index, and broadband chirality further brings the index to negative values for left-handed circularly polarized light in the entire range below the plasma frequency. Non-resonant architecture results in very low loss (<2% per layer) and an extremely high Figure-of-merit (>90). Tunable THz metamaterials has shown great potential to solve the material challenge due to the so-called “THz gap”. However, the tunable mechanism of current designs relies on using semiconductors insertions, which inevitably results in high Ohmic loss, and thereby significantly degrades the performance of metamaterials. In this work, we demonstrate a novel tunable mechanism based on polymeric microactuators. Our metamaterials are fabricated on the surface of patterned pillar array of flexible polymers embedded with magnetic nanoparticles. The transmission spectrum of the metamaterial can be tuned as the pillars are mechanically deformed though applied magnetic field. We observed and measured several type of deformation including bending, twisting and compressing when the applied magnetic field is polarized along different direction with respected to the axis of the magnetic particles. Compared to previous semiconductor based tunable mechanism, our structure has shown much lower loss. We demonstrate using simulations and experimentally that with an external magnetic field, we can achieve phase modulation using magnetic polymeric micro-actuators.
APA, Harvard, Vancouver, ISO, and other styles
50

Lübcke, Peter [Verfasser], and Ulrich [Akademischer Betreuer] Platt. "Optical remote sensing measurements of bromine and sulphur emissions: Investigating their potential as tracers of volcanic activity / Peter Lübcke ; Betreuer: Ulrich Platt." Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1180031458/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the bibliographies on the topic 'Optical activity' for other source types:
Journal articles Books
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography