Siga este link para ver outros tipos de publicações sobre o tema: Structure fine de l’exciton.
Teses / dissertações sobre o tema "Structure fine de l’exciton"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Structure fine de l’exciton".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
1
Prin, Elise. "Propriétés optiques fondamentales de nanocristaux de semi-conducteurs individuels aux températures cryogéniques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0182.
Texto completo da fonteResumo:
Les nanocristaux de semi-conducteurs présentent des propriétés optiques et électroniques remarquables en raison du confinement quantique de leurs porteurs de charge, ce qui les rend avantageux pour diverses applications en optoélectronique, dans les dispositifs émetteurs de lumière et dans les technologies basées sur le spin. La compréhension de la physique de l’exciton de bord de bande, dont la recombinaison est à l’origine de leur photoluminescence, est cruciale pour le développement de ces applications. Cette thèse porte sur l’étude expérimentale des propriétés optiques des nanocristaux de phosphure d’indium et de pérovskites d’halogénure de plomb. En utilisant une méthode de spectroscopie de magnéto-photoluminescence sur des nanocristaux uniques à basse température, nous révélons des empreintes spectrales très sensibles à la morphologie des nanocristaux et élucidons la structure fine de l’exciton de bord de bande et les énergies de liaison des complexes de charge. Dans les nanocristauxd’InP/ZnS/ZnSe, l’évolution des spectres et des déclins de luminescence sous champ magnétique montrent l’existence d’un niveau d’exciton noir situé à moins d’un millielectronvolt en dessous du triplet brillant de l’exciton, résultats étayés par un modèle tenant compte de l’anisotropie de forme du coeur d’InP. Dans les pérovskites d’halogénure de plomb, nous démontrons que l’état fondamental de l’exciton est noir et se situe plusieurs millielectronvolts en dessous des sous-niveaux d’exciton brillants les plus bas, résolvant ainsi le débat sur l’ordre des niveaux brillants et noirs de l’exciton dans ces matériaux. En combinant nos résultats avec des mesures spectroscopiques sur divers composés de nanocristaux de pérovskite, nous établissons des lois d’échelle universelles qui relient l’éclatement de la structure fine de l’exciton et les énergies de liaison du trion et du biexciton à l’énergie de l’exciton de bord de bande dans les nanostructures de pérovskite d’halogénure de plomb, quelle que soit leur composition chimique. Enfin, des analyses préliminaires de spectroscopie sur des nano-bâtonnets de pérovskite avec un grand rapport d’aspect suggèrent leur potentiel en tant qu’émetteurs de lumière quantique grâce à leur émission composée d’une raie uniqueSemiconductor nanocrystals exhibit outstanding optical and electronic properties due to the quantum confinement of their charge carriers, making them valuable for various applications in optoelectronics, light-emitting devices, and spin-based technologies. Understanding the physics of the band-edge exciton, whose recombination is at the origin of their photoluminescence, is crucial for developing these applications. This thesis focuses on the experimental study of the optical properties of indium phosphide and lead halide perovskites nanocrystals. Using magneto-photoluminescence spectroscopy onsingle nanocrystals at low temperatures, we reveal spectral fingerprints highly sensitive to nanocrystal morphologies and elucidate the entire band-edge exciton fine structure and charge-complex binding energies. In InP/ZnS/ZnSe nanocrystals, the evolution of photoluminescence spectra and decays under magnetic fields show evidence for a ground dark exciton level lying less than a millielectronvolt below the bright exciton triplet, findings supported by a model accounting for the shape anisotropy of the InPcore. In lead halide perovskites, we demonstrate that the ground exciton state is dark and lies several millielectronvolts below the lowest bright exciton sublevels, settling the debate on the bright-dark exciton level ordering in these materials. Combining our results with spectroscopic measurements on various perovskite nanocrystal compounds, we establish universal scaling laws relating exciton fine structure splitting, trion and biexciton binding energies to the band-edge exciton energy in lead-halide perovskitenanostructures, regardless of their chemical composition. Lastly, preliminary spectroscopy analyses on perovskite nanorods with a high aspect ratio suggest their potential as candidates for quantum light emitters due to their characteristic single emission line
2
Smiciklas, Marc. "A Determination of the Fine Structure Constant Using Precision Measurements of Helium Fine Structure". Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc31547/.
Texto completo da fonteResumo:
Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electro-optic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new determination of the fine structure constant α. An apparatus was designed and built to overcome limitations encountered in a previous experiment. Not only did this allow an improved level of precision but also enabled new consistency checks, including an extremely useful measurement in 3He. I discuss the details of the experimental setup along with the major changes and improvements. A new value for the J = 0 to 2 fine structure interval in the 23P state of 4He is measured to be 31 908 131.25(30) kHz. The 300 Hz precision of this result represents an improvement over previous results by more than a factor of three. Combined with the latest theoretical calculations, this yields a new determination of α with better than 5 ppb uncertainty, α-1 = 137.035 999 55(64).
3
Johnson, Colin Terence. "Fine structure transitions in astrophysics". Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317096.
Texto completo da fonte
4
Turnbull, Alexander James. "Fine structure in elliptical galaxies". Thesis, University of Hertfordshire, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323441.
Texto completo da fonte
5
Jankowski, Charles Robert. "Fine structure features for speaker identification". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11012.
Texto completo da fonteResumo:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 193-198).
by Charles Robert Jankowski, Jr.
Ph.D.
6
Tovena, Lucia M. "The fine structure of polarity sensitivity /". New York ; London : Garland, 1998. http://catalogue.bnf.fr/ark:/12148/cb37081866c.
Texto completo da fonte
7
Givors, Fabien. "Vers une structure fine des calculabilités". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20160/document.
Texto completo da fonteResumo:
La calculabilité est centrée autour de la notion de fonction calculable telle que définie par Church, Kleene, Rosser et Turing au siècle dernier. D'abord focalisée sur les nombres entiers, la calculabilité a été généralisée aux ensembles, notamment par le biais de la théorie axiomatique des ensembles de Kripke-Platek. Dans cette thèse, nous définissons une notion générale de calculabilité, les sous-calculabilités, dont les axiomes sont satisfaits à la fois par de nombreux fragments récursifs de la calculabilité classique, mais également par des calculabilités d'ordre supérieur sur les ensembles admissibles. Nous montrons, sur cette structure composée d'une énumération de fonctions totales et d'une énumération de fonctions partielles, que les théorèmes classiques de calculabilité (isomorphisme de Myhill, Rogers, théorème s-m-n,point fixe de Kleene, théorème de Rice, créativité, etc.) sont présents sous différentes formes alors même que les sous-calculabilités ne comprennent qu'un fragment des objets de la calculabilité classique. Les structures de degrés associées aux notions de récursivité que nous définissons reflètent également des propriétés de la calculabilité (degrés intermédiaires, high, low, etc.), mais nos réductions étant plus fortes, une structure fine apparaît à l'intérieur même des degrés récursifs. Finalement, nous montrons que les calculabilités sur les admissibles sont interprétables dans le formalisme des sous-calculabilités. En particulier, les énumérations des ensembles alpha-finis et alpha-énumérables présents dans ce contexte nous permettent de transférer certains résultats d'un modèle à l'autreComputability is centered on computable functions, as defined by Church, Kleene,Rosser and Turing in the twentieth century. Initially focused on integers,computability has been generalised to sets, in particular thanks toKripke-Platek's Axiomatic Set Theory.In this thesis, we define a general notion of computability,sub-computabilities, whose axioms are satisfied by numerous recursive fragmentsof classical computability, and also by higher-order computabilities overadmissible sets. We show how in sub-computabilities, containing an enumeration oftotal functions and an enumeration of partial functions, classical theoremssuch as Myhill and Rogers isomorphisms, s-m-n theorem, Kleene's fixed-point orRice's theorem hold in a slightly different way, even if a large part ofthe objects of computability are missing. Along with each of thesesub-computabilities and their different notions of recursivity comes a structureof degrees (with intermediate, high and low degrees, etc.), refining theclassical one, our notions of recursivity being stronger.Moreover, we show how admissible computability can be interpreted through theformalism of sub-computabilities. In particular, the enumerations ofalpha-finite and alpha-enumerable sets present in this setting allowsome interesting results to be carried from one model to the other
8
ISHIHARA, TAKASHI, e YUKIO KANEDA. "Fine-scale structure of thin vortical layers". Cambridge University Press, 1998. http://hdl.handle.net/2237/10287.
Texto completo da fonte
9
Macindoe, Owen. "Investigating the fine grained structure of networks". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60103.
Texto completo da fonteResumo:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 107-109).
In this thesis I explore a novel representation for characterizing a graph's fine grained structure. The key idea is that this structure can be represented as a distribution of the structural features of subgraphs. I introduce a set of such structural features and use them to compute representations for a variety of graphs, demonstrating their use in qualitatively describing fine structure. I then demonstrate the utility of this representation with quantitative techniques for computing graph similarity and graph clustering. I show that similarity judged using this representation is significantly different from judgements using full graph structural measures. I find that graphs from the same class of networks, such as email correspondence graphs, can differ significantly in their fine structure across the institutions whose relations they model, but also find examples of graphs from the same institutions across different time periods that share a similar fine structure.
by Owen Macindoe.
S.M.
10
Kane, Frances. "The fine structure of the Irish NP". Thesis, Ulster University, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675469.
Texto completo da fonteResumo:
This thesis is a structural analysis of the DP in Irish. The thesis is based on analysis of a number of different types of noun phrases and a consideration of the observed patterns in relation to other languages and syntactic theory in general. The proposal accounts for the typical data that has been analysed previously in the literature as well as novel data not yet accounted for within existing analyses. As well as providing a full structural account of the Irish NP, the findings of this thesis provide evidence in Support of the universal existence of a number of functional projections, which have been shown to be projected for language in general.
11
Hitchen, Gregory James. "Measurement and analysis of LEED fine structure". Thesis, Hitchen, Gregory James (1990) Measurement and analysis of LEED fine structure. PhD thesis, Murdoch University, 1990. https://researchrepository.murdoch.edu.au/id/eprint/51661/.
Texto completo da fonteResumo:
LEED fine structure features arise from an interference between the measured beam and a pre-emergent beam internally reflected at the surface potential barrier. Such features are observed at very low energies (typically 0-40eV) and usually consist of a rydberg-like series of peaks converging on the emergence energy of the pre-emergent beam. These features provide a means of determining the shape of the surface potential barrier of a metal.
It is possible to calculate theoretical fine structure spectra by using a barrier model with adjustable parameters. These parameters can be altered to give the best fit to experiment. To obtain an unambiguous fit it is necessary to perform this matching over a range of angles and for multiple peaks within the structure. Thus a good data base for analysis consists of high resolution intensity versus energy spectra at various angles of incidence and azimuths. For this work an electron spectrometer capable of fulfilling these requirements designed and was built. It was used to measure fine structure features from the clean and oxygen covered surfaces of Cu(00l) and Cu(lll).
The success of LEED fine structure analysis depends upon a precise knowledge of the quantities that characterize each spectrum, namely the incidence angle, the azimuth angle and the contact potential difference between the filament emitting the electrons and the crystal surface. These need to be known to a precision that reflects the total resolution of the experiment. In this work techniques were developed for determining these values and these were applied to the data collected from the Cu(00l) and Cu(111) surfaces.
Analysis of this data yielded information regarding the shape of the surface potential barrier. It was also possible to reach some conclusions about the chemisorption sites for oxygen adsorption. The importance of using the full LEED theory for substrate scattering effects in the analysis of fine structure features is also demonstrated.
12
Giemza, Joanna. "Fine-scale genetic population structure in France". Thesis, Nantes, 2019. http://www.theses.fr/2019NANT1007/document.
Texto completo da fonteResumo:
La structure génétique à fine échelle des populations humaines est intéressante pour deux raisons principales : 1) elle reflète des événements historiques et démographiques, 2) elle informe la recherche sur les études d’association de maladies. Cette thèse a pour objectif de procéder à une analyse approfondie de la structure génétique de la population de France métropolitaine dans un premier temps, en de façon plus détaillée de la population du nord-ouest de la France, et de mettre en lumière les événements historiques, démographiques et culturels qui l’ont façonnés, en tirant parti de trois jeux de données (SU.VI.MAX/3C et PREGO). Au niveau de la France, nous rapportons la corrélation entre les données génétiques et les lieux de naissance d’individus appartenant à deux cohortes françaises indépendantes (1 414 et 770 individus) et identifions six groupes, concordants entre les jeux de données. La deuxième étude tire parti de la cohorte PREGO, qui comprend 3 234 personnes ayant trois générations d’ascendance liée à des régions spécifiques du nord-ouest de la France. Je révèle une structure à fine échelle à un niveau sans précédent (154 sous-populations).historique de la France et des explications potentielles de la prévalence de différentes maladies dans cette région du nord-ouest. Dans l’ensemble, mes travaux de thèse indiquent des niveaux substantiels de stratification de la population dans une région géographiquement limitée, probablement en raison de différents antécédents démographiques dans la régionFine-scale genetic structure in human populations is interesting for two main reasons: 1), it reflects historical and demographic events, 2) it informs research on disease association studies. This thesis aims to perform a thorough analysis of the genetic structure of the population from continental France, in particular Northwestern France, and shed light on the historical, demographic and cultural events that have shaped it, by taking advantage of three genome-wide datasets (SU.VI.MAX/3C and PREGO) At the country level we report the correlation between genetic data and birthplaces of individuals in two independent French cohorts (1,414 and 770 individuals in SU.VI.MAX and 3C, respectively) and identify six clusters, concordant between datasets, and may correspond to ancient political, cultural and geographical borders. The second study takes advantage of the PREGO cohort including 3,234 individuals with three generations of ancestry linked to specific regions of Northwestern France and reveals fine-scale structure at an unprecedented level (154 subpopulations). The resulting genetic clusters and the characterisation of their effective population size and ancestry proportions compared to other European groups provide important and novel insights into the historical peopling of France and potential explanations for different disease prevalence within this northwestern region. Overall, my thesis work indicate substantial levels of population stratification within a geographically limited region likely caused by different demographic histories across the region
13
Robinson, Kate. "The Integrity of the Structure". Thesis, Mills College, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1551689.
Texto completo da fonteResumo:
The Integrity of the Structure is an artists' book installation made of mono-printed and hand-worked masa paper framed in wood to create a series of screens (one with a video projection) that construct a space for the reader/audience to walk through. The text and video on the screens, as well as the reader/audience themselves moving through the space constitute the content of the book. This paper is a creative/critical hybrid reflection on the installation and its concepts.
14
Behrens, Anna-Janina. "Fine structure of the HIV-1 glycan shield". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:3cec0ef7-c305-411e-a76b-125d5e7e9954.
Texto completo da fonteResumo:
The HIV-1 envelope glycoprotein trimer (Env) is covered by an extensive array of glycans that shield it from immune surveillance. The high density of glycans on the trimer surface imposes steric constraints that limit the actions of glycan processing enzymes, such that multiple under-processed structures remain on specific locations. These oligomannose-type glycans are recognized by broadly neutralizing antibodies (bNAbs) that are not thwarted by the glycan shield but, perhaps paradoxically, target it. In multiple studies, bNAbs have been shown to be capable of providing passive protection from viral challenge, making Env a focus of antibody-mediated vaccine design. Here, the development of a workflow for the semi-quantitative, site-specific N-glycosylation analysis of a soluble recombinant, native-like trimer mimic (BG505 SOSIP.664) is reported. The resulting data reveal a mosaic of dense clusters on the outer domain of Env and allow mapping the extremes of simplicity and diversity of glycan processing. Although individual sites usually minimally affect the global integrity of the glycan shield, examples are identified of how deleting certain glycans can subtly influence neutralization by bNAbs that bind at distant sites. Env is a trimer of heterodimers of gp120 and gp41, which is generated by cleavage of an endogenous protease. In this thesis, the detailed effect of protease cleavage on glycan processing is examined by comparing the site-specific N-glycosylation profiles of the native-like trimer mimic to the corresponding uncleaved pseudotrimer and the matched gp120 monomer. Trimer-associated glycan remodeling forms a localized subdomain of the native mannose patch. Furthermore, the glycosylation analysis of further Env immunogens â a glycan-depleted trimer and a flexibly-linked, uncleaved trimer (both based on BG505 SOSIP.664) â provides important insights into the robustness of the HIV-1 glycan shield and the Env maturation pathway. Overall, this thesis reveals how structural constraints shape Env glycosylation and the network of bNAb-targeted glycans that should be preserved on recombinant vaccine candidates.
15
Reichelt, Uwe J. M. "The physical meaning of the fine structure constants". Uwe J. M. Reichelt, 2021. https://slub.qucosa.de/id/qucosa%3A75202.
Texto completo da fonteResumo:
The article solves the riddle of the fine structure constants with the help of the Planck units, derives its physical meaning and shows the consequences.:Abstract
Introduction
What is the fine structure constant?
Consequence from the existence of the fine structure constant.
16
Poiarkova, Anna V. "X-ray absorption fine structure Debye-Waller factors /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9731.
Texto completo da fonte
17
Douin, Joël. "Structure fine des dislocations et plasticité dans NiAl". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37604626p.
Texto completo da fonte
18
Evans, Jason L. "On the variability of the fine structure constant /". Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd496.pdf.
Texto completo da fonte
19
Collier, David Clifford Robert. "The fine structure of orbits in dynamical systems". Thesis, University of Manchester, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489633.
Texto completo da fonte
20
Evans, Jason Lott. "On the Variability of the Fine Structure Constant". BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/144.
Texto completo da fonteResumo:
This thesis addresses the issue of the time variability of the fine structure constant, alpha. Recent claims of a varying alpha are set against the established standards of quantum electrodynamical theory and experiments. A study of the feasibility of extracting data on the time dependence of alpha using particles in Penning traps is compared to the results obtained by existing methods, including those using astrophysical data and those obtained in atomic clock experiments. Suggestions are made on the nature of trapped particles and the trapping fields.
21
Fantin, Daniele S. M. "Ultra-fine dark matter structure in the solar neighbourhood". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11877/.
Texto completo da fonteResumo:
Dark matter plays a fundamental role in theories of the formation and evolution of galaxies. Thus every attempt to model galaxy formation and evolution has to take into consideration the presence of dark halos. Moreover, mergers and accretion appear to be fundamental driving mechanisms in determining the present day properties of galaxies. The aim of this thesis is to study the ultra-fine distribution of dark matter in the Solar neighbourhood, and to investigate the implications for the current and next generation of dark matter directional detectors. For this purpose we develop a model for halo mergers in a Milky Way-like galaxy. The signals expected in lab-based dark matter detection experiments depend on the phase-space distribution on sub-milliparsec scales. With our numerical technique it is possible to resolve structures produced by minor mergers of subhalos with a larger parent halo. This type of substructure is unaccessible to conventional N-body simulations. When applied in a cosmological context,this method becomes a powerful instrument to reproduce and analyse the complete multiple merger history of a Milky Way-like system. The results obtained simulating the Galactic halo suggest that the velocity distribution in the solar neighbourhood after an evolution time corresponding to the lifetime of our galaxy (≃ 14Gyr) is smooth. This result suggests the presence of a huge number of dark matter streams that overlap to form a smooth distribution. Nevertheless, the final velocity distribution has overdensities for all the cases that has been analysed. They are generated by a very large number of merger events, but the current generation of detectors have not the angular resolution required to observe these features. A future generation of detectors with a resolution of ~ 1◦ would start to resolve them, allowing the merger history of the Galaxy to begin to be unravelled using this diagnostic.
22
MACHKOV, IGOR. "Structure fine des excitons dans les superreseaux gaas/alas". Paris 7, 1996. http://www.theses.fr/1996PA077094.
Texto completo da fonteResumo:
La structure fine des excitons dans les superreseaux gaas/alas est etudiee par battements quantiques, resonance magnetique detectee optiquement (odmr) et anticroisement de niveaux. 1) dans les superreseaux gaas/alas de type-2 l'exciton est localise aux interfaces par les defauts d'epaisseur des couches et la degenerescence des etats radiatifs d'exciton est levee. En excitant en impulsions une superposition coherente de ces etats, on observe des oscillations d'intensite de luminescence au cours du temps (battements quantiques). On obtient la difference d'energie des etats, le temps de vie et le temps de relaxation de spin des excitons. En champ magnetique longitudinal ou transverse on determine les facteurs de lande des porteurs. Les battements quantiques sont observes sous excitation resonante et bande-a-bande. Le calcul du taux de polarisation de la luminescence resolue en temps permet d'interpreter les differentes periodes observees. 2) dans les echantillons ou le temps de vie est superieur a 100 ns, il est possible de faire des experiences d'odmr. On deduit l'interaction d'echange electron-trou dans l'exciton et les facteurs de lande de l'exciton et des porteurs libres. 3) pour deux valeurs du champ magnetique longitudinal, un niveau optiquement interdit de l'exciton anticroise successivement les niveaux permis de l'exciton. Pour ces valeurs du champ la polarisation de la luminescence augmente. Ce phenomene est mis a profit pour l'etude de la structure fine des excitons dans les superreseaux gaas/alas de type-2, pour l'etude des structures proches de la transition type-2/type-1 et les structures de type-1. L'observation des anticroisements de niveaux excitoniques nous permet de relier l'ordre des sous-niveaux radiatifs avec la nature de l'interface (gaas-sur-alas ou alas-sur-gaas) sur laquelle les excitons sont localises
23
Naughton, David Vincent. "On the fine structure of dynamically-defined invariant graphs". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/on-the-fine-structure-of-dynamicallydefined-invariant-graphs(0e81b14b-af68-4433-a983-f98a7b8c5d86).html.
Texto completo da fonte
24
Sutter, Jon. "Structure and Repetition". VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1834.
Texto completo da fonteResumo:
This work is the result of an exploration into the relationship of form and pattern. Its inspiration began as an experiment where certain two dimensional graphical patterns were interpreted as three dimensional elements in a lattice-like assembly. The resulting compositions are built entirely of MDF, and each piece is made from multiple copies of one or two identically shaped parts that are joined with shallow grooves. Some of the pieces resemble Asian architectural lattices as well as the scientific models of molecules in crystals. Often, the flat components seem to undulate in space or twist into impossible shapes. Although the various compositions appear dissimilar, the differences are a result of only minor changes to the individual parts that comprise them. Therefore, the work is metaphorically analogous to other complex systems made from simple components such as the structure of matter, the organization of cells, or primordial life in general.
25
Buades, Bárbara. "Attosecond X-ray absorption fine-structure spectroscopy in condensed matter". Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/663092.
Texto completo da fonteResumo:
Attoscience aims to study electron dynamics in matter with unprecedented temporal resolution by using the shortest pulses generated on Earth. Currently, such resolution is only provided by sources that deliver attosecond pulses based on the high-harmonic generation (HHG) process. In this thesis we make use of the demonstration of the generation of isolated attosecond pulses in the soft X-ray (SXR) regime covering the entire water window (284 eV to 543 eV) with pulse durations shorter than 300 as. Such a source is used to explore its own development, the spectroscopic capabilities of the pulses as well as the spectroscopic differences from existing X-ray sources, and finally to exploit the potential of the provided extraordinary temporal resolution.
We report on the ability to spectrally tune our source 150 eV across the water window by controlling the pressure during the HHG process and the HHG target position with respect to the focal plane of the driving laser pulse. We associate the changes in pressure and target position to a phase matching change between the driving laser pulse of the HHG process and the generated SXR radiation that is mainly caused by a change in the ionisation fraction. These phase matching changes are also compared to a carrier-to-envelope phase changes of the driving laser field.
The attosecond SXR source is used for X-ray absorption fine structure (XAFS) spectroscopy. Our XAFS studies enable the simultaneous probing of extended XAFS (EXFAS) and near edge XAFS (NEXAFS) in graphite, providing element specificity and orbital sensitivity with identification of the sigma* and pi* orbitals in synchronicity with the material’s four characteristic bonding distances. This illustrates the potential capability of correlating electron dynamics with structural dynamics with attosecond resolution being able to resolve charge migration, electron-phonon coupling and structural transitions. Our XAFS investigations also reveal spectral changes in graphite and TiS2 as a consequence of the shorter attosecond pulse compared to the longer picosecond pulse that are typically used in synchrotron facilities. An extended theory is still required to link Auger electron spectroscopy, total electron yield and XAFS using synchrotron radiation with attoXAFS to decouple the different electron dynamics involved on each of the measurements.
Finally, the attosecond pulses are employed to interrogate charge dynamics with unprecedented temporal resolution inside a compound quasi-2D material, TiS2. By synchronising a 1.85 µm pump pulse with the probing attosecond SXR pulse, we observe that the shape of the X-ray absorption line changes from a Lorentzian distribution to a Fano-type distribution oscillating with twice the pump electric field frequency. The absorption changes appear due to an acquired dipole phase response of the photo-excited core-level electron induced by the consecutive arrival of the infrared pump pulse. This demonstrates that field-driven intra-band dynamics dominate over inter-band dynamics. SXR radiation also provides element specificity of attoXAFS which permits, in combination with theory, the visualisation of the flow of charge amongst the atoms inside the unit cell in real time. The combined spatio-temporal capabilities of attosecond transient XAFS may prove decisive to investigate the correlated motion of carriers in quantum materials such as phase-transitions and superconductors.La Attociencia tiene como objetivo estudiar la dinámica de electrones en la materia con una resolución temporal sin precedentes mediante el uso de los pulsos más cortos generados en la Tierra. Actualmente, dicha resolución solo se puede lograr con fuentes de pulsos de attosegundos basados ¿¿en el proceso de generación de armónicos altos (HHG). En esta tesis hacemos uso de la demostración de la generación de pulsos aislados de attosegundos en el régimen de rayos X blandos (SXR) que cubre toda la ventana de agua (284 eV a 543 eV) con duraciones de pulso más cortos que 300 as. Dicha fuente se utiliza para explorar su propio desarrollo, las capacidades espectroscópicas de los pulsos, así como las diferencias espectroscópicas con las fuentes de rayos X existentes, y finalmente explotar el potencial de la resolución temporal extraordinaria proporcionada. Presentamos primero la capacidad de ajustar espectralmente nuestra fuente 150 eV a lo largo de la ventana de agua mediante el control de la presión del gas atómico involucrado en el proceso de HHG y de la posición del proceso de HHG con respecto al plano focal del láser impulsor de activación del proceso. Asociamos los cambios en la presión y en la posición a un cambio de coincidencia de fase entre el láser impulsor y la radiación SXR generada que es causada principalmente por un cambio en la fracción de ionización. Estos cambios de fase también se comparan con los cambios de fase entre la envolvente del campo y el campo (CEP). La fuente de SXR de attosegundo se utiliza para la espectroscopía de estructura fina de absorción de rayos X (XAFS). Nuestros estudios XAFS permiten el sondeo simultáneo de XAFS extendido (EXFAS) y XAFS cercano al borde (NEXAFS) en grafito, proporcionando especificidad de elemento y sensibilidad orbital con identificación de los orbitales sigma* y pi* en sincronicidad con las cuatro distancias de enlace características del material. Esto ilustra la capacidad potencial de correlacionar la dinámica de electrones con la dinámica estructural con resolución de attosegundos, pudiendo resolver la migración de carga, el acoplamiento electrón-fonón y las transiciones estructurales. Nuestras investigaciones XAFS también revelan cambios espectrales en grafito y TiS2 como consecuencia del pulso de atosegundo más corto en comparación con el pulso de picosegundo más largo que se utilizan normalmente en las instalaciones de sincrotrón. Todavía se requiere una teoría extendida para vincular la espectroscopia electrónica de Auger, el campo total de electrones (TEY) y XAFS utilizando radiación sincrotrón con attoXAFS para desacoplar las diferentes dinámicas electrónicas involucradas en cada una de las mediciones. Finalmente, los pulsos de attosegundo se emplean para analizar la dinámica de carga con una resolución temporal sin precedentes dentro de un material compuesto de cuasi-2D, TiS2. Al sincronizar un pulso de luz de bombeo de 1.85 µm con el pulso SXR de attosegundo, observamos que la línea de absorción de rayos X cambia de una distribución de Lorentzian a una distribución de tipo Fano que oscila con el doble de la frecuencia del campo eléctrico de bombeo. Los cambios de absorción aparecen debido a una respuesta de fase dipolar adquirida del electrón excitado por fotoionicaición por la llegada consecutiva del pulso de bombeo infrarrojo. Con esto se demuestra que las dinámicas dentro de la banda impulsadas por el campo dominan sobre la dinámica entre bandas. La radiación SXR también proporciona especificidad de elemento de attoXAFS que permite, en combinación con la teoría, la visualización del flujo de carga entre los átomos dentro de la celda unitaria en tiempo real. Las capacidades espaciotemporales combinadas del XAFS transitorio de attosegundo pueden ser decisivas para investigar el movimiento correlacionado de portadores en materiales cuánticos, como transiciones de fase y superconductores.
26
Mauermann, Manfred Dieter. "Fine structure in distortion product otoacoustic emissions and auditory perception". [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972885544.
Texto completo da fonte
27
Hankemeier, Sebastian [Verfasser]. "The magnetic fine structure of thin-film elements / Sebastian Hankemeier". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2011. http://d-nb.info/1010757768/34.
Texto completo da fonte
28
Durno, W. Evan. "Precise correlation and metagenomic binning uncovers fine microbial community structure". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62360.
Texto completo da fonteResumo:
Bacteria and Archaea represent the invisible majority of living things on Earth with an estimated numerical abundance exceeding 10^30 cells. This estimate surpasses the number of grains of sand on Earth and stars in the known universe. Interdependent microbial communities drive fluxes of matter and energy underlying biogeochemical processes, and provide essential ecosystem functions and services that help create the operating conditions for life. Despite their abundance and functional imperative, the vast majority of microorganisms remain uncultivated in laboratory settings, and therefore remain extremely difficult to study. Recent advances in high-throughput sequencing are opening a multi-omic (DNA and RNA) window to the structure and function of microbial communities providing new insights into coupled biogeochemical cycling and the metabolic problem solving power of otherwise uncultivated microbial dark matter (MDM). These technological advances have created bottlenecks with respect to information processing, and innovative bioinformatics solutions are required to analyze immense biological data sets. This is particularly apparent when dealing with metagenome assembly, population genome binning, and network analysis.
This work investigates combined use of single-cell amplifed genomes (SAGs) and metagenomes to more precisely construct population genome bins and evaluates the use of covariance matrix regularization methods to identify putative metabolic interdependencies at the population and community levels of organization. Applying dimensional reduction with principal components and a Gaussian mixture model to k-mer statistics from SAGs and metagenomes is shown to bin more precisely, and has been implemented as a novel pipeline, SAG Extrapolator (SAGEX). Also, correlation networks derived from small subunit ribosomal RNA gene sequences are shown to be more precisely inferred through regularization with factor analysis models applied via Gaussian copula. SAGEX and regularized correlation are applied toward 368 SAGs and 91 metagenomes, postulating populations’ metabolic capabilities via binning, and constraining interpretations via correlation. The application describes coupled biogeochemical cycling in low-oxygen waters. Use of SAGEX leverages SAGs’ deep taxonomic descriptions and metagenomes’ breadth, produces precise population genome bins, and enables metabolic reconstruction and analysis of population dynamics over time. Regularizing correlation networks overcomes a known analytic bottleneck based in precision limitations.Science, Faculty of
Graduate
29
Pierseaux, Yves. "La structure fine de la théorie de la relativité restreinte". Doctoral thesis, Universite Libre de Bruxelles, 1998. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212021.
Texto completo da fonte
30
Henriques, Vasco M. J. "Three-dimensional mapping of fine structure in the solar atmosphere". Doctoral thesis, Stockholms universitet, Institutionen för astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-86798.
Texto completo da fonteResumo:
The effects on image formation through a tilted interference filter in a converging beam are investigated and an adequate compensation procedure is established. A method that compensates for small-scale seeing distortions is also developed with the aim of co-aligning non-simultaneous solar images from different passbands. These techniques are applied to data acquired with a narrow tiltable filter at the Swedish 1-meter Solar Telescope. Tilting provides a way to scan the wing of the Ca II H line. The resulting images are used to map the temperature stratification and vertical temperature gradients in a solar active region containing a sunspot at a resolution approaching 0''10. The data are compared with hydro-dynamical quiet sun models and magneto-hydrodynamic models of plage. The comparison gives credence to the observational techniques, the analysis methods, and the simulations. Vertical temperature gradients are lower in magnetic structures than in non-magnetic. Line-of-sight velocities and magnetic field properties in the penumbra of the same sunspot are estimated using the CRISP imaging spectropolarimeter and straylight compensation adequate for the data. These reveal a pattern of upflows and downflows throughout the entire penumbra including the interior penumbra. A correlation with intensity positively identifies these flows as convective in origin. The vertical convective signatures are observed everywhere, but the horizontal Evershed flow is observed to be confined to areas of nearly horizontal magnetic field. The relation between temperature gradient and total circular polarization in magnetically sensitive lines is investigated in different structures of the penumbra. Penumbral dark cores are prominent in total circular polarization and temperature gradient maps. These become longer and more contiguous with increasing height. Dark fibril structures over bright regions are observed in the Ca II H line core, above both the umbra and penumbra.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.
31
Mota, David Fonseca. "Variations of the fine structure constant in space and time". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615756.
Texto completo da fonte
32
Crapper, M. D. "X-ray absorption fine structure of adsorbates on metal surfaces". Thesis, University of Warwick, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377093.
Texto completo da fonte
33
Young, Robert James. "Controlling the fine structure splitting in single InAs quantum dots". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613860.
Texto completo da fonte
34
Bui, Thi Hanh [Verfasser]. "The excitonic fine structure of colloidal nanocrystals / Thi Hanh Bui". Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/123055517X/34.
Texto completo da fonte
35
Shorrosh, Raed Saed. "An x-ray absorption fine structure study of semiconductor nanoclusters". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/30867.
Texto completo da fonte
36
Ilango, Kandan. "Phlebotomine sandfly reproduction : fine structure and function of the spermathecae". Thesis, London School of Hygiene and Tropical Medicine (University of London), 1995. http://researchonline.lshtm.ac.uk/1416608/.
Texto completo da fonteResumo:
In contrast to most blood sucking flies, the structure of the spermathecae in phlebotomine sandflies exhibits extraordinary diversity. The objective of this study was to investigate the fine structure of the spermathecae in relation to mating of phlebotomine sandflies. Light microscopy and electron (scanning and transmission) microscopy were used to examine species of four representative subgenera from the Old World Sergentomyia (Parrotomyia) babu, Phlebotomus (Euphlebotomus) argentipes, P. (Phlebotomus) papatasi and P. (Larroussius) langeroni. The spermathecae of P. papatasi is composed of a pair long spermathecal ducts, a cylindrical spermatheca surrounded by a visceral muscle and a spherical gland attached by an epithelial layer. The internal histology of the spermathecae in all the four species includes: a simple epithelial layer of class 1 epidermal cells, elaborate glandular cells (class 3 epidermal cells) each having receiving and conducting ductules ("end apparatus") and a cytological apodeme, which is a new finding for the insect epidermis. The glandular cells are connected to the lumen of the spermatheca by cuticular ductules passing through a cuticular block which has a high resilin content. The spermathecal complex is enveloped in a supercontracting visceral muscular system and has a myoneural junction. Based on this study a new terminology for the spermathecal morphology is proposed. The spermathecae undergo substantial physiological changes during the female gonotrophic cycle based on studies with Phlebotomus papatasi and P. argentipes. A histochemical study revealed a mucopolysaccharide secretory-mass in the newly emerged fly. During insemination, spermatophores are deposited in the spermathecal ducts. Previous reports of mating plugs in sandflies appear to be artifacts. The histology of the spermatophore is described and the anatomical evidence for sperm competition and and II displacement presented. Blood-feeding stimulates the release of sperm from spermatophoroand then they migrate to the lumen of the spermatheca. The fine structure of spermatozoa in P. papatasi and P. argentipes during their morphological change, such as acrosomal membrane casting off described. Physical evidence suggests that P .papatasi is inseminated more than once in each gonotrophic cycle, and that further insemination is necessary for subsequent cycles. The lock-and-key hypothesis has been suggested as an important mechanism for species evolution. To test this, the length of the spermathecal duct and aedeagal filament were examined from 28 species of 13 subgenera of the Old World phelebotomine sandflies. In general, there was a positive correlation between these variables but in most taxa the aedeagal filaments were long for direct insemination of the spermathecal proper. that These findings indicate.sperm competition takes place. Given the structural diversity of the spermathecae and its significance in mating strategies, and the importance of spermathecae in phlebotomine systematics, a comparative morphological study of spermathecal variation with male genitalic variation d· was made to classify the Old World phlebotomines. Twenty nine taxa representative.all the Old World subgenera were analyzed by cladistic methods. The phylogenetic groupings based on these characters generally confirmed the presently accepted system, and that all the vectors of human leishmaniasis are in recent terminal taxa
37
Douin, Joël. "Structure fine des dislocations et plasticité dans Ni(3)Ai". Poitiers, 1987. http://www.theses.fr/1987POIT2313.
Texto completo da fonteResumo:
Etude detaillee de l'evolution de la structure fine des dislocations dans une large gamme de temperature autour du pic de limite elastique (600-700c). Analyse cristallographique de la structure ordonnee l1::(2) et des defauts plans de cette structure. Presentation, a partir de cette analyse, des resultats des simulations atomiques de paroi d'antiphase. Calcul de forme et d'energie de dislocations en elasticite anisotrope. Analyse du mecanisme de formation des defauts d'empilement. Etude, en fonction de la temperature d'essai, de la structure fine des dislocations. Influence d'une variation de composition sur la morphologie des dislocations
38
DeRose, Guy Arthur. "X-ray absorption fine structure strain determination in thin films". Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1060005230.
Texto completo da fonte
39
Pierseaux, Yves. "La structure fine de la théorie de la relativité restreinte /". Paris ; Montréal (Québec) : l'Harmattan, 1999. http://catalogue.bnf.fr/ark:/12148/cb37050978s.
Texto completo da fonte
40
Wellings, John Victor. "Fine structure and mechanical design of cylindrical tension-transmitting cytoskeletons". Thesis, University of St Andrews, 1985. http://hdl.handle.net/10023/14013.
Texto completo da fonteResumo:
All cells contain cytoskeletal components which perform static 'spatial organizing' and dynamic 'motile' functions. The studies described in this thesis concern two types of cytoskeletal component of universal biological importance: microtubules and microfilaments, and various other structures which are associated with them. The general properties of microtubules and microfilaments and of other cytoskeletal components are reviewed in the introduction. Examples of the functions they perform in various systems are described, with emphasis on Protozoa and metazoan morphogenetic systems. The ciliate Nassula aurea was the first system studied. The cytopharyngeal basket is a tube shaped feeding organelle through which rapid cytoplasmic streaming occurs. The basket becomes deformed during transport of a food vacuole through its lumen. Ultrastructural examination of deformed baskets reveal that part of the basket, the tubular 'sheath', becomes stretched, probably in an elastic manner. Links between the microtubules in the sheath also appear to become stretched, so these could be responsible for the elastic properties. The nature of the links between microtubules within the 'rods', components of the basket responsible for its longitudinal rigidity, is also discussed, as are some other features relevant to the function of the basket as a feeding organelle. The second system studied was oogenesis in Drosophila melanogaster. Several stages in the development of the oocyte and the surrounding follicle cells and nurse cells were examined ultrastructurally. The arrangement of microtubules and microfilaments is described, as are the changes that occur in these and other structures during oogenesis, and the related changes in morphology. A circumferentially oriented layer of microfilaments was discovered in vitellogenic oocyte follicles. The oocyte expands rapidly during vitellogenesis, as cytoplasm flows into it from the nurse cells, and as yolk proteins and nutrients flow in across the follicle. The microfilamentous layer could cause the oocyte to elongate as it expands by restricting its increase in diameter. The layer is destroyed by cytochalasin B, and can be decorated by heavy meromyosin. Therefore it is concluded that the microfilaments are actin-like. Various other structures in the developing egg chamber (the oocyte plus follicle and nurse cells) are described.
41
Danilović, Sanja. "Magnetic fine structure in the solar photosphere observations and MHD simulations". Berlin Uni-Ed, 2009. http://d-nb.info/1002469767/04.
Texto completo da fonte
42
Ng, Sui-chung. "Variation of the fine structure constant in 5D Kaluza-klein theory". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31993175.
Texto completo da fonte
43
Kleindienst, Thomas. "The fine scale structure of synaptic inputs in developing hippocampal neurons". Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-126626.
Texto completo da fonte
44
Willinger, Marc-Georg. "Investigation of the oxygen K-edge fine structure in vanadium oxides /". Online version, 2001. http://bibpurl.oclc.org/web/20813.
Texto completo da fonte
45
Rottenfußer, Günter [Verfasser]. "On the dynamical fine structure of entire transcendental functions / Günter Rottenfußer". Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2008. http://d-nb.info/1034768298/34.
Texto completo da fonte
46
Vaumousse, David. "An atom probe study of fine scale structure in A1MgSi(Cu)". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401025.
Texto completo da fonte
47
Ng, Sui-chung, e 吳瑞聰. "Variation of the fine structure constant in 5D Kaluza-klein theory". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31993175.
Texto completo da fonte
48
McKerr, G. "The fine structure and physiology of a trypanorhynch tapeworm Grillotia erinaceus". Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233293.
Texto completo da fonte
49
Jackson, Helen Mary. "The role of temporal fine structure in pitch and speech perception". Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608187.
Texto completo da fonte
50
Yu, Jung-Suk. "Essays on Fine Structure of Asset Returns, Jumps, and Stochastic Volatility". ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/431.
Texto completo da fonteResumo:
There has been an on-going debate about choices of the most suitable model amongst a variety of model specifications and parameterizations. The first dissertation essay investigates whether asymmetric leptokurtic return distributions such as Hansen's (1994) skewed tdistribution combined with GARCH specifications can outperform mixed GARCH-jump models such as Maheu and McCurdy's (2004) GARJI model incorporating the autoregressive conditional jump intensity parameterization in the discrete-time framework. I find that the more parsimonious GJR-HT model is superior to mixed GARCH-jump models. Likelihood-ratio (LR) tests, information criteria such as AIC, SC, and HQ and Value-at-Risk (VaR) analysis confirm that GJR-HT is one of the most suitable model specifications which gives us both better fit to the data and parsimony of parameterization. The benefits of estimating GARCH models using asymmetric leptokurtic distributions are more substantial for highly volatile series such as emerging stock markets, which have a higher degree of non-normality. Furthermore, Hansen's skewed t-distribution also provides us with an excellent risk management tool evidenced by VaR analysis. The second dissertation essay provides a variety of empirical evidences to support redundancy of stochastic volatility for SP500 index returns when stochastic volatility is taken into account with infinite activity pure Lévy jumps models and the importance of stochastic volatility to reduce pricing errors for SP500 index options without regard to jumps specifications. This finding is important because recent studies have shown that stochastic volatility in a continuous-time framework provides an excellent fit for financial asset returns when combined with finite-activity Merton's type compound Poisson jump-diffusion models. The second essay also shows that stochastic volatility with jumps (SVJ) and extended variance-gamma with stochastic volatility (EVGSV) models perform almost equally well for option pricing, which strongly imply that the type of Lévy jumps specifications is not important factors to enhance model performances once stochastic volatility is incorporated. In the second essay, I compute option prices via improved Fast Fourier Transform (FFT) algorithm using characteristic functions to match arbitrary log-strike grids with equal intervals with each moneyness and maturity of actual market option prices.