Lactobacillus kunkeei is one of the most abundant bacteria within the honey crop of the honey bee. Genome sequencing of L. kunkeei isolated from honey bees all over the world showed several genes unique for L. kunkeei. Among these orphan genes, an array of four to five highly conserved genes coding for giant extracellular proteins were found. Cryogenic electron microscopy imaging of a giant-protein preparation from L. kunkeei A00901 showed an overall structure similar to a long string with a knot at the end. Further analysis showed high similarity between the different giants at the N-terminus, and secondary structure predictions showed that the same region was rich in β-sheets.  These results, combined with the knowledge of other large extracellular proteins, led to the hypothesis that the “knot” domain is located at the N-terminus and that these proteins are used by the cell to latch on to the intestine lining or other cells in the honey crop. In this study, predictions were made to locate the N-terminal domains of two of these giant proteins. Four different constructs were made for each protein, where three constructs were designed for expression and purification of the N-terminal domain with different end-positions, and one construct was for a predicted β-solenoid domain located downstream from the N-terminal domain. The protein constructs were recombinantly produced in E. coli, and three of the N-terminal constructs from both proteins were purified. Thermal stability was tested using nano differential scanning fluorimetry (nanoDSF), Thermofluor, and circular dichroism (CD), which all showed characteristic melting curves at low melting temperatures, ranging from 33 °C to 44 °C, for all three constructs. During CD measurements, all three constructs showed refolding after thermal denaturation and a higher abundance of antiparallel β-sheets over α-helices. Looking at the protein structure, small angle X-ray scattering data indicated that all three proteins formed elongated structures. These results indicate that a folded domain has been found for both proteins. Although, further analysis will be required to determine the boundaries of the N-terminal domains, and to elucidate if these domains have anything to do with ligand binding and the L. kunkeei ability to latch onto the honey crop.

No description available.

No / The in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness (similar to 50 angstrom) and bulk crystallinity (similar to 20%), were low at, for all processing conditions investigated, which is attributed to the significant short-chain branching in the polymer acting as point defects limiting lamellae crystal growth. (C) 2013 Elsevier Ltd. All rights reserved.

<p>This dissertation discusses the theoretical methods for quantum scattering in the context of x-ray scattering from electrons and classical scattering in the context of collisions between Rydberg atoms.</p> <p><br></p> <p>A method for describing non-relativistic x-ray scattering from bound electrons is presented. The approach described incorporates the full spatial dependence of the incident x-ray field and is non-perturbative in the incident x-ray field. The x-ray scattering probability obtained by numerical solution for the case of free-electrons is bench-marked with well known analytical free-electron results.</p> <p><br></p> <p>A recent investigation by Fuchs \emph{et al.} [Nat. Phys. 11, 964 (2015)] revealed an anomalous frequency shift of at least 800 eV in non-linear Compton scattering of high-intensity x-rays by electrons in solid beryllium. The x-ray scattering approach described is used to explore the role of binding energy, band structure, electron-electron correlation and a semi-Compton channel in the frequency shift of scattered x-rays for different scattered angles. The results of the calculation do not exhibit an additional redshift for the scattered x-rays beyond the non-linear Compton shift predicted by the free-electron model. </p> <p><br></p> <p>The interference between Compton scattering and nonlinear Compton scattering from a two-color field in the x-ray regime is theoretically analyzed for bound electrons. A discussion of the underlying phase shifts and the dependence of the interference effect on the polarizations of the incident and outgoing fields are presented. </p> <p><br></p> <p>The problem of using x-ray scattering to image the dynamics of an electron in a bound system is examined. Previous work on imaging electronic wave-packet dynamics with x-ray scattering revealed that the scattering patterns deviate substantially from the notion of instantaneous momentum density of the wave packet. Here we show that the scattering patterns can provide clear insights into the electronic wave packet dynamics if the final state of the scattered electron and the scattered photon momentum are determined simultaneously. The scattering probability is shown to be proportional to the modulus square of the Fourier transform of the instantaneous electronic spatial wave function weighted by the final state of the electron.</p> <p><br></p> <p>Collisional ionization between Rydberg atoms is examined. The dependence of the ionization cross section on the magnitude and the direction of orbital angular momentum of the electrons and the direction of the Laplace-Runge-Lenz vector of the electrons is studied. The case of exchange ionization is examined and its dependence on the magnitude of angular momentum of the electrons is discussed.</p> <p><br></p>

Hintergrund: Die Entwicklung von Nanotechnologien und insbesondere integrierten Schaltkreisen beruht auf dem Verständnis von Struktur und Funktion auf der Nanoskala, wofür exakte Messungen erforderlich sind. Kleinwinkel-Röntgenstreuung unter streifendem Einfall (GISAXS) ist eine Methode zur schnellen, berührungs- und zerstörungsfreien dimensionellen Messung von nanostrukturierten Oberflächen. Ziele: Es soll die Möglichkeit untersucht werden, die zunehmend komplexeren Proben aus Wissenschaft und Industrie mit Hilfe von GISAXS präzise zu vermessen. Ein weiteres Ziel ist es, Messtargets aus der Halbleiter-Qualitätskontrolle mit einer Größe von ca. 40x40 µm² zu messen, deren Signal typischerweise nicht zugänglich ist, weil ein Bereich von ca. 1x20 mm² auf einmal beleuchtet wird. Methoden: Synchrotron-basierte GISAXS-Messungen verschiedener Proben werden mit Hilfe einer Fourier-Konstruktion, der "distorted wave Born approximation" und einem Maxwell-Gleichungs-Löser basierend auf finiten Elementen analysiert. Ergebnisse: Aus GISAXS-Messungen kann die Linienform von Gittern mit einer Periode von 32 nm rekonstruiert werden und sie weicht weniger als 2 nm von Referenzmessungen ab. Eine sorgfältige Bayes'sche Unsicherheitsanalyse zeigt jedoch, dass wichtige dimensionelle Parameter innerhalb der Unsicherheiten nicht übereinstimmen. Für die Messung von kleinen Gittertargets entwerfe ich ein neuartiges Probendesign, bei dem das Target in Bezug auf die umgebenden Strukturen gedreht wird, und stelle fest, dass dadurch parasitäre Streuung effizient unterdrückt wird. Fazit: GISAXS-Messungen von komplexen Nanostrukturen und kleinen Targets sind möglich, jedoch würde GISAXS enorm von effizienteren Simulationsmethoden profitieren, die alle relevanten Effekte wie Rauhigkeit und Randeffekte einbeziehen. Hier gibt es vielversprechende theoretische Ansätze, so dass GISAXS eine zusätzliche Methode für die Halbleiter-Qualitätskontrolle werden könnte. / Background. The development of nanotechnology such as integrated circuits relies on an understanding of structure and function at the nanoscale, for which reliable and exact measurements are needed. Grazing-incidence small angle X-ray scattering (GISAXS) is a versatile method for the fast, contactless and destruction-free measurement of sizes and shapes of nanostructures on surfaces. Aims. A goal of this work is to investigate the possibility of precisely measuring the increasingly complex samples produced in science and industry using GISAXS. A second objective is to measure targets used in semiconductor quality control with a size of approx. 40x40 µm², whose signal is typically not accessible because an area of approx. 1x20 mm² is illuminated at once. Methods. I take synchrotron-based GISAXS measurements and analyze them using reciprocal space construction, the distorted wave born approximation, and a solver for Maxwell's equations based on finite elements. Results. I find that the line shape of gratings with a period of 32 nm can be reconstructed from GISAXS measurements and the results deviate less than 2 nm from reference measurements; however, a careful Bayesian uncertainty analysis shows that key dimensional parameters do not agree within the uncertainties. For the measurement of small grating targets, I create a novel sample design where the target is rotated with respect to the surrounding structures and find that this efficiently suppresses parasitic scattering. Conclusions. I show that GISAXS measurements of complex nanostructures and small targets are possible, and I highlight that further development of GISAXS would benefit tremendously from efficient simulation methods which describe all relevant effects such as roughness and edge effects. Promising theoretical approaches exist, so that GISAXS has the potential to become an additional method in the toolkit of semiconductor quality control.

No description available.

The ability to quickly develop predictions of the time-to-failure under different loading levels allows designers to choose the best polymeric material for a specific application. Additionally, it helps material producers to design, manufacture, test, and modify a polymeric material more rapidly. In the case of polymeric pipes, previous studies have shown that there are two possible time-dependent failure mechanisms corresponding to ductile and brittle failure. The ductile mechanism is evident at shorter times-to-failure and results from the stretching of the amorphous region under loading and the subsequent plastic deformation. Empirical results show that many high-performance polyethylene (PE) materials do not exhibit the brittle failure mechanism. Hence, it is critical to understand the ductile mechanism and find an approach to predict the corresponding times-to-failure using accelerated means. The aim of this study is to develop an innovative rupture lifetime acceleration protocol for PE pipes which is sensitive to the structure, orientation, and morphology changes introduced by changing processing conditions. To accomplish this task, custom fixtures are developed to admit tensile and hoop burst tests on PE pipes. A pressure modified Eyring flow equation is used to predict the rupture lifetime of PE pipes using the measured mechanical properties under axial tensile and hydrostatic pressure loading in different temperatures and strain rates. In total, the experimental method takes approximately one week to be completed and allows the prediction of pipe lifetimes for service lifetime in excess of 50 years. / Master of Science

Un nouveau modèle de biomembrane de type liposome a été développé à partir de lipides synthétisés comportant une unité biphényle sur leur chaînes sn2 et une chaîne aliphatique sn1 de longueur et insaturation variables. L’anisotropie de susceptibilité magnétique positive de ces molécules induit une déformation en oblate de ces liposomes dits « biphényles » dans le champ magnétique B0. Cette déformation spécifique a été caractérisée par RMN des solides 31P et 2H en faisant varier différents paramètres : l’intensité de B0, l'élasticité membranaire, la température et la taille des liposomes (Helfrich, 1973). Ces vésicules déformées ont pu être observées par microscopies optiques et électroniques et la rémanence de la déformation en dehors de B0 a pu être analysée par diffusion des rayons X aux petits angles (SAXS). Enfin, les premières applications des liposomes biphényles comme nouveau modèle de biomembrane pour analyser la structure et l’orientation (par RMN des solides 15N) de peptides ou protéines membranaires, ont été étudiées. / A new model of biomembrane (liposome) was developed from synthesized lipids containing a biphenyl unit on the sn2 aliphatic chain and possessing a sn1 aliphatic chain which varies in length and unsaturation. The positive magnetic susceptibility anisotropy of these molecules induces an oblate deformation of these «biphenyls » liposomes under the magnetic field B0. This particular deformation has been characterized by 31P and 2H solid state NMR by varying different parameters: the intensity of B0, the membrane elasticity, the temperature and the size of the liposomes (Helfrich, 1973). These deformed vesicles were observed by optical and electron microscopy and the remanence of the deformation outside B0 has been analyzed by Small angles X-ray scattering (SAXS).Finally, the first applications of biphenyls liposomes as new biomembrane model to analyze the structure and orientation of membrane proteins or peptides were studied by 15N solid state NMR

L'utilisation de matériaux polymères a su s'imposer au cours du 20ième siècle, en remplaçant ou se combinant aux matériaux métalliques, pour des applications mécaniques toujours plus techniques. La grande diversité des propriétés physiques des polymères est intimement lié à leur forte complexité microstructurale, qui malgré leur utilisation massive reste, au demeurant, encore très incomprise. Afin de mieux comprendre les évolutions microstructurales aux échelles nano et micrométrique dont résultent le comportement macroscopique il est nécessaire de développer de nouvelles techniques de caractérisation in situ. Ce travail fait état de l'utilisation de la spectroscopie Raman couplée au système VidéoTractionTM afin d'obtenir des informations microstructurales de la déformation de polymère semi-cristallins. Pour cela, des polypropylènes de formulations diverses ont été étudiés, permettant de souligner le rôle joué par la matrice et les charges organiques et minérales dans le processus de déformation plastique. Des mesures in situ de l'orientation des chaînes macromoléculaires déterminées in situ par Raman ont été confirmées, au synchrotron Petra III d'Hambourg, par une expérience couplant le système VidéoTractionTM-Raman à un dispositif de diffusion des rayons X aux grands angles. L'endommagent volumique des matériaux a été étudié post mortem par Tomographie X et radiographie X. Les améliorations apportées au système VidéoTractionTM-Raman ainsi qu'une étude de la diffusion de la lumière incohérente de nos matériaux au cours de leurs déformations ont permis l'établissement d'un critère de mesure de l'endommagement volumique in situ par Raman / The use of polymer materials - replacing or combining with metallic materials - has successfully established itself in the 20th century for increasingly technical mechanical applications. The great diversity of polymers physical properties is closely related to their high microstructural complexity, which is still very misunderstood despite their massive use. The development of new techniques for in situ characterization allows to better understand the microstructural evolutions on nanoscale and micrometer scale which affect the macroscopic behavior. This work report the use of Raman spectroscopy coupled with the VideoTractionTM system in order to obtain information about the microstructural deformation of polymer. Various formulations of polypropylene were studied to highlight the role played by the polypropylene matrix and the organic and mineral fillers in the plastic deformation process. The in situ measures of the macromolecular chains' orientation determined by Raman were confirmed by the performing of an experimental setup coupling the Raman-VideoTractionTM system with a device of Wide angle X-ray scattering. The volume damage of material was studied post mortem using X-ray tomography. The improvements made to VideoTractionTM-Raman system and a study of the incoherent light scattering of our materials enabled the setting of a Raman criterion for measuring in situ the volume damage. The studies carried out to evaluate in situ macromolecular orientation and volume damage highlight the existence of competition between these two processes. The degree of influence of organic and mineral fillers in this competition within the polypropylene matrix was determined

Quantum spin liquids (QSLs) are strongly correlated systems displaying fascinating phenomena like long-range entanglement and fractionalized excitations. The research on these states has since its beginning followed trends generated by the synthesis of new compounds and the construction of new theoretical tools. In coherence with this history, a manifold of new results about QSLs were established during the past decade due to studies on the integrable Kitaev model on the honeycomb lattice. This j = 1/2 model displays bond-dependent and anisotropic exchanges that are essential to stabilize its QSL ground state with Majorana fermion excitations and emergent Z2 gauge field. Even more interestingly, this model is relevant to understand the magnetism of a certain class of 4/5d5 Mott insulators with specific lattice constraints, t2g orbital degeneracy and strong spin-orbit coupling (SOC). This mechanism defining these so-called Kitaev materials can be applied to similar compounds based on transition metal ions in different electronic configurations. In this thesis, I investigate minimal models for two types of 4/5d1 Mott insulators: the ones on the ordered double perovskite structure (ODP) and the ones isostructural to the Kitaev materials. Their effective models generically show bond-dependent and anisotropic interactions involving multipoles of an effective j = 3/2 angular momentum. Such degrees of freedom are conveniently written in terms of pseudospin s and pseudo-orbital &tau; operators resembling spin and orbital operators of Kugel-Khomskii models with twofold orbital degeneracy. Despite their anisotropy, the two realistic models display continuous global symmetries in the limit of vanishing Hund\'s coupling enhancing quantum fluctuations and possibly stabilizing a QSL phase. Parton mean-field theory was used to propose fermionic QSLs that will be called quantum spin-orbital liquids (QSOLs) due their dependence with s and &tau;. On ODPs, I studied a chiral QSOL with Majorana fermion excitations and a gapless spectrum characterized by nodal lines along the edges of the Brillouin zone. These nodal lines are topological defects of a non-Abelian Berry connection and the system exhibits dispersing surface states. Several experimental responses of the chiral QSOL within the mean-field approximation are compared with the experimental data available for the spin liquid candidate Ba2YMoO6. Moreover, based on a symmetry analysis, I discuss the operators involved in resonant inelastic X-ray scattering (RIXS) amplitudes for 4/5d1 Mott insulators and show that the RIXS cross sections allow one to selectively probe pseudospin and pseudo-orbital degrees of freedom. For the chiral spin-orbital liquid in particular, these cross sections provide information about the spectrum for different flavors of Majorana fermions. The model for materials isostructural to the Kitaev materials has an emergent SU(4) symmetry that is made explicit by means of a Klein transformation on pseudospin degrees of freedom. The model is known to stabilize a QSOL on the honeycomb lattice and instigated the investigation of QSOLs on a generalization of this lattice to three dimensions. Parton mean-field theory was used once again to propose the liquid states, and a variational Monte Carlo (VMC) method was used to compute the energies of the projected wave functions. The numerical results show that the lowest-energy QSOL corresponds to a zero-flux state with a Fermi surface of four-color fermionic partons. Further VMC computations also revealed that this state is stable against formation of plaquette ordering (tetramerization). The energy of this QSOL is highly competitive even when Hund\'s coupling induced perturbations are included, as shown by comparison with simple ordered states. Extensions and perspectives for future work are discussed in the end of this thesis. / Líquidos de spin quânticos (QSLs) são sistemas fortemente correlacionados que apresentam fenômenos fascinantes como emaranhamento de longo alcance e excitações fracionárias. A pesquisa a respeito destes estados seguiu tendências geradas pela síntese de novos compostos e construção de novas técnicas teóricas desde seu princípio. Coerentemente com essa história, uma variedade de novos resultados a respeito de líquidos de spin foram estabelecidos na última década graças a estudos feitos sobre o modelo integrável de Kitaev na rede colmeia. Este modelo de spins j = 1/2 apresenta interações de troca anisotrópicas e direcionalmente dependentes que são essenciais para estabilizar um estado fundamental do tipo QSL com férmions de Majorana e campo de gauge Z2 emergente. Ainda mais interessante, este modelo é relevante para se entender o magnetismo de uma certa classe de isolantes de Mott baseados em metais de transição na configuração 4/5d5 em redes específicas, degenerescência orbital t2g e acoplamento spin-órbita forte (SOC). Esse mecanismo que define os chamados materiais do tipo Kitaev podem ser aplicados a compostos baseados em metais de transição em configurações eletrônicas diferentes. Nesta tese, eu investigo modelos mínimos para dois tipos de isolantes de Mott do tipo 4/5d1: os que se apresentam na estrutura perovskita dupla ordenada (ODP) e os isostruturais aos materiais do tipo Kitaev. Seus modelos efetivos genericamente apresentam interações multipolares anisotrópicas e direcionalmente dependentes de um momento angular efetivo j = 3/2. Estes graus de liberdade são convenientemente escritos em termos de operadores de pseudospin s e pseudo-orbital &tau; semelhantes a operadores de spin e orbital de modelos do tipo Kugel-Khomskii com orbitais duplamente degenerados. A despeito da anisotropia, esses dois modelos realísticos apresentam simetrias globais contínuas no limite de acoplamento de Hund nulo que incrementam flutuações quânticas e possivelmente estabilizam uma fase do tipo QSL. A teoria de campo médio com partons foi usada para propor QSLs fermiônicos que serão chamados de líquidos spin-orbitais quânticos (QSOLs) devido à dependência deles com s e &tau;. Em ODPs, eu estudei um líquido de spin quiral com excitações do tipo férmion de Majorana e um espectro sem gap caracterizado por linhas nodais ao longo das arestas da zona de Brillouin. Essas linhas nodais são defeitos topológicos de uma conexão de Berry não-abeliana e o sistema apresenta estados de superfície dispersivos. Várias respostas experimentais foram calculadas para o QSOL quiral dentro da aproximação de campo médio e comparadas com os dados experimentais disponíveis para o candidato a líquido de spin Ba2YMoO6. Além disso, baseado em uma análise de simetria, discuto os operadores envolvidos nas amplitudes de espalhamento de raios-x ressonante para isolantes de Mott na configuração 4/5d1 e mostro que seções de choque de RIXS permitem estudar seletivamente os graus de liberdade de pseudospins e pseudo-orbitais. Para o caso particular do líquido spin-orbital quiral, essas seções de choque nos fornecem informações sobre o espectro de diferentes sabores de férmions de Majorana. Esse modelo possui uma simetria SU(4) emergente que é tornada explícita através de uma transformações de Klein nos graus de liberdade de pseudospin. Sabe-se que este modelo estabiliza um QSOL na rede colmeia, o que instigou uma investigação de QSOLs na generalização desta rede em três dimensões. A teoria de campo médio com partons foi usada novamente para propor estes líquidos quânticos, e o método de Monte Carlo Variacional (VMC) foi usado para calcular as energias das funções de onda projetadas. Os resultados numéricos mostraram que o QSOL de menor energia corresponde a um estado de fluxo-zero com superfície de Fermi envolvendo partons fermiônicos de quatro cores. Cálculos adicionais com VMC também demonstraram que este estado é estável à formação de ordem de plaquetas (tetramerização). A energia deste QSOL é altamente competitiva mesmo quando perturbações induzidas pelo acoplamento de Hund são incluídas, o que é mostrado através da comparação com estados ordenados simples. Extensões e perspectivas para trabalhos futuros são discutidas no final desta tese.