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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Compensation de la fréquence des résonateurs MEMS pour des applications de référence temps / Control of the frequency of the electromechanical resonators MEMS

Civet, Yoan 16 May 2012 (has links)
A l’heure actuelle, les Micro-Electro-Mechanical-Systems (MEMS) sont devenusincontournables dans les produits technologiques quotidiens. De par leur taille,leurs performances et leur intégration, les microsystèmes résonants se sontinscrits dans la diversification de la fameuse Loi de Moore. Cependant les applications detype base de temps demeurent le segment de marché où les MEMS ne parviennent pas às’imposer durablement. En effet, grâce à une stabilité en fréquence de quelques parties parmillions, l’oscillateur à base de résonateur en Quartz reste le produit numéro 1 d’unmarché estimé à dix-sept milliards de dollars.Etant donné le lien entre la fréquence d’un résonateur silicium MEMS et ses dimensionsintrinsèques, les différentes étapes de fabrication induisent un décalage de cette fréquencepar rapport à la valeur visée. C’est donc cet écart que nous tenterons d’adresser. Dans cecontexte, nous avons proposé une nouvelle méthode de correction à l’échelle du substrat.Cette méthode consiste en une ultime étape technologique, après une première mesureélectrique des dispositifs qui permet de quantifier l’erreur, à ramener la fréquence à lavaleur souhaitée par un ajout localisé de matière. Nous montrerons qu’il est possible, enune seule étape, de réduire la Gaussienne représentative de la variation de la fréquence ausein du substrat à quelques parties par million. Pour cela, nous avons développé deuxmodèles physiques qui permettent de quantifier la correction pour atteindre les objectifs.En parallèle, nous avons mis en place un processus de fabrication compatible avec la filièreCMOS avec seulement dix-sept étapes et deux masques photolithographiques dont le pointde départ est un substrat de type SOI. Ce procédé a permis la fabrication de résonateur àmodes de flexion et ondes de volume, dont les performances intrinsèques (f et Q)permettent de concurrencer les résonateurs Quartz. Enfin, nous avons validé notre conceptet nos modèles physiques par des caractérisations électriques de nos dispositifs.L’analyse des résultats nous a permis de dresser une liste des pistes d’amélioration pourétablir une voie vers l’industrialisation durable des résonateurs MEMS. Dans un premiertemps, une attention toute particulière se portera sur le choix du substrat et la technologieutilisée pour garantir des performances optimales. La méthode de correction nécessite unemesure électrique intermédiaire, cette étape doit être précisée et il faudra s’assurer qu’ellen’augmente pas le coût global de la fonction. Bien que discutés, le packaging du MEMS etl’intégration seront des points à étudier, tout particulièrement pour conserver lesspécifications du résonateur lui-même. / Present, Micro-Electro-Mechanical-Systems (MEMS) have become essential ineveryday technology products. Thanks to their size, performances andintegration, resonant microsystems have been enrolled in the diversification ofthe famous Moore's Law. However, the time based applications remain the market segmentwhere MEMS are unable to settle permanently. Indeed, the oscillator-based Quartz is thenumber one product on the market, a market estimated at $ 17 billions, thanks to afrequency stability of a few parts per million over its lifetime.Given the link between the frequency of a MEMS resonator and its intrinsic dimensions,the various manufacturing steps induce a shift of this frequency from the target value. Wewill try to address this difference.In this context, we proposed a new method of correction across the wafer. This methodconsists of a final technological step after a first electrical measurement to quantify theshift. We will show that it is possible in one step, to reduce the Gaussian representing thefrequency variation within the wafer to a few parts per million. From this perspective, wehave developed two physical models that quantify the correction to achieve the objectives.Moreover, we set up a manufacturing process CMOS compatible with only 17 steps and2 photolithographic masks starting with a SOI wafer. This process has enabled theproduction of flexural mode resonators and bulk mode resonators, whose intrinsicperformances (f, Q) can compete with Quartz. Finally, we validated our concept and ourphysical models thanks to electrical characterization of our devices.Analysis of the results allowed us to develop a list of possible improvements to establish aroute to the industrialization of MEMS resonators. First, special attention will be focusedon the choice of substrate and the technology used to ensure perfect performances.Correction method requires a preliminary electrical measurement, this step must bedetailed and one have to ensure that it does not increase the overall cost. Although partiallystudied, the packaging of MEMS and integration are the points to consider in particularkeeping the specifications of the resonator itself.
62

Reutilização de resíduo SiO2 como potencial na confecção de massa refratária de sílica / Reuse of SiO2 waste for potential use as paste production of refractory silica

Santos, Maria de Lourdes dos 26 February 2013 (has links)
Made available in DSpace on 2016-12-08T17:19:20Z (GMT). No. of bitstreams: 1 resumo.pdf: 33365 bytes, checksum: c0d79b06b712dd7d33a99ff2c405578a (MD5) Previous issue date: 2013-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The silica refractory is nowadays one of the most used linings in the world due to its excellent cost/benefit ratio. The silica sand is available in abundance in the market for use as a raw material for production of ordinary applications refractories, and this does not encourage the search for new usages of its wastes. However, in some industrial sectors where the natural raw materials are used, it has been noticed an increased difficulty to find materials with adequate purity grades to its applications. Furthermore, most of the productive sector is looking for alternatives to reduce the generation of industrial wastes that must be disposed in specific landfills. In this study one aimed to evaluate the potential use of a waste from the synthesis of SiO2 refractory for the application with Alkaline Sodium Silicate and Silica Refractory Paste. This paste is utilized as lining for Ingots and Pouring Ladles in the Foundry Process. This proposal is supported by the demand of Tupy S/A to recover that waste. This company is totally committed to the environment care of your productive processes, always aiming the reduction of wastes generation and its discard. In this proposal it was considered an initial processing stage to partially remove the excess iron present in the wastes that is deleterious to the silica lining. The refractories were produced making waste additions up to 100% in weight. The obtained refractories characterizations, as well as each process step efficiency evaluation, were done through techniques like thermal analysis, X-ray diffraction analysis, grain size distribution curves and ambient temperature compression strength measurements. The results showed good performance with the addition of silica waste, especially a significant increase in ambient temperature compression strength; provided by incorporation of the waste with higher amount of grain small, medium and large. The economic viability of the economy is considerable and preservation of raw materials, conventional silica sand, and the reuse of waste silica mix, avoiding disposal at a landfill. / O refratário de sílica é hoje um dos revestimentos mais utilizados no mundo pelo seu excelente custo/benefício. A areia de sílica como matéria prima para a obtenção de refratários de uso convencional está disponível no mercado em abundância, o que não incentiva a busca por alternativas para a reutilização de seus resíduos. Entretanto, em diversos setores industriais onde matérias primas naturais são utilizadas tem notado o aumento na dificuldade de obtenção de materiais com grau de pureza adequado a suas aplicações. Além disso, todo o setor produtivo tem buscado por alternativas para redução da geração de resíduos industriais a serem descartados em aterros específicos. O presente trabalho busca avaliar o potencial do uso de um resíduo refratário na síntese de refratário de SiO2 para aplicação com Massa Refratária de Silica e Silicato de Sódio Alcalino (MRSNA) para revestimentos de lingoteiras e panelas de vazamento utilizados no processo de Fundição. Esta proposta está baseada na necessidade da reutilização desse resíduo pela empresa Tupy S. A. Esta empresa tem como premissa a constante preocupação ambiental nos seus processos produtivos, buscando sempre a redução da geração de resíduos ou descarte destes. Para o desenvolvimento desta proposta foi considerada inicialmente uma etapa de beneficiamento para a remoção parcial do excesso de ferro presente no resíduo que é um contaminante para o revestimento de sílica. Os refratários foram produzidos considerados adições de resíduos em teores em peso de resíduo de até 100%. Para a caracterização dos refratários obtidos, assim como para avaliação da eficiência das diferentes etapas de processamento foram utilizadas ferramentas como análise térmica, difratometria de raios-X, construção de curvas de distruibuição granulométrica e medidas de resistência à compressão a tempertura ambiente. Os resultados mostraram um bom desempenho com a adição do resíduo de sílica, especialmente um aumento significativo na resistência à compressão à temperatura ambiente; proporcionado por uma curva de distribuição granulométrica heterogênea (grãos pequenos, médios e grandes). A viabilidade econômica é considerável pela economia e preservação da matéria prima, areia de sílica convencional, e pela reutilização do resíduo de sílica mix, evitando o seu descarte em aterro industrial.
63

Etude des corrélations entre les défauts structuraux et les inhomogénéités spatiales des détecteurs de rayons X à base de CdTe pour l'imagerie médicale / Study of correlation between the structural defects and inhomogeneities of CDTE based radiation detectors used for medical imaging

Buis, Camille 11 October 2013 (has links)
Ces travaux de doctorat proposent d’apporter une contribution à l’identification et à la compréhension des phénomènes limitant les performances de détecteurs de rayon X à base de CdTe:Cl développés pour des applications en radiographie. En effet, des inhomogénéités spatiales non-stables dans le temps sont observées dans la réponse de ces capteurs. Les défauts des cristaux utilisés pour la détection ont été caractérisés. Notamment, les dislocations révélées par attaque chimique et par topographie X présentent des arrangements en mur à la surface des échantillons, ces défauts sont majoritairement traversant dans toute l’épaisseur du cristal. Il a ensuite été montré que ces murs de dislocations sont responsables des inhomogénéités de photo-courant sous irradiation par des rayons X et de courant de fuite d’un détecteur à base de CdTe:Cl. De plus, les niveaux pièges dans le gap du CdTe ont été investigués par des méthodes de spectroscopie optique à basse température : les images de cathodoluminescence mettent en évidence le caractère non-radiatif des murs de dislocations, mais ne montrent pas l’apparition de la luminescence Y au niveau de ces défauts, normalement attribuée aux dislocations dans la littérature. Enfin, l’influence des murs de dislocations sur les propriétés de transport des porteurs de charge a été étudiée par la méthode « Ion Beam Induced Current » (IBIC) montrant qu’ils entraînent une diminution de la valeur du produit mobilité-temps de vie des électrons et des trous / In the present Ph.D. thesis, we investigate microstructural defects in a chlorine-doped cadmium telluride crystal (CdTe:Cl), to understand the relationship between defects and performance of CdTe-based radiation detectors. Characterization tools, such as diffraction topography and chemical etching, are used for bulk and surface investigations of the distribution of dislocations. Dislocations are arranged into walls. Most of them appear to cross the whole thickness of the sample. Very good correlation is observed between areas with variations of dark-current and photo-current, and positions of the dislocation walls revealed at the surface of the sample. Then spectroscopic analysis of these defects was performed at low temperatures. It highlighted that dislocation walls induce non-radiative recombination, but it didn’t show any Y luminescence usually attributed to dislocations in the literature. Ion Beam Induced Current (IBIC) measurements were used to evaluate the influence of dislocation walls on charge carrier transport properties. This experiment shows that they reduce the mobility-Iifetime product of the charge carriers. A very clear correlation was, in fact, established between the distribution of the dislocation network and the linear defects revealed by their lower CIE on the device
64

Dual-band impedance transformation networks for integrated power amplifiers

Wolf, Robert, Joram, Niko, Schumann, Stefan, Ellinger, Frank 02 June 2020 (has links)
This paper shows that the two most common impedance transformation networks for power amplifiers (PAs) can be designed to achieve optimum transformation at two frequencies. Hence, a larger bandwidth for the required impedance transformation ratio is achieved. A design procedure is proposed, which takes imperfections like losses into account. Furthermore, an analysis method is presented to estimate the maximum uncompressed output power of a PA with respect to frequency. Based on these results, a fully integrated PA with a dual-band impedance transformation network is designed and its functionality is proven by large signal measurement results. The amplifier covers the frequency band from 450 MHz to 1.2 GHz (3 dB bandwidth of the output power and efficiency), corresponding to a relative bandwidth of more than 100%. It delivers 23.7 dBm output power in the 1 dB compression point, having a power-added efficiency of 33%.
65

Etude et modélisation des dégradations des composants de puissance grand gap soumis à des contraintes thermiques et électriques / Study and modeling of large gap power components degradations subjected to thermal and electrical constraints

Jouha, Wadia 29 November 2018 (has links)
Ce travail vise à étudier la robustesse de trois générations de MOSFET SiC de puissance (Silicon Carbide Metal Oxide Semiconductor Field E_ect Transistors). Plusieurs approches sont suivies : la caractérisation électrique, la modélisation physique, les tests de vieillissement et la simulation physique. Un modèle compact basé sur une nouvelle méthode d'extraction de paramètres et sur les résultats de caractérisation électrique est présenté. Les paramètres extraits du modèle (tensionde seuil, transconductance de la région de saturation et paramètre du champ électrique transverse) sont utilisés pour analyser avec précision le comportement statique de trois générations de MOSFET SiC. La robustesse de ces dispositifs sont étudiées par deux tests : le test HTRB (High Temperature Reverse Bias) et le test ESD (Electrostatic Discharge). Une simulation physique est réalisée pour comprendre l'impact de la température et des paramètres physiques sur les caractérisations électriques des MOSFETs SiC. / This work aims to investigate the robustness of three generations of power SiC MOSFETs (SiliconCarbide Metal Oxide Semiconductor Field E_ect Transistors). Several approaches are followed :electrical characterization, device modeling, ageing tests and physical simulation. An improvedcompact model based on an accurate parameters extraction method and one electrical characterization results is presented. The parameters extracted precisely from the model (thresholdvoltage, saturation region transconductance...) are used to accurately analyze the static behaviorof two generations of SiC MOSFETs. The robustness of these devices are investigated bytwo tests : HTRB (High Temperature Reverse Bias) stress and an ESD (Electrostatic Discharge)stress. Physical simulation is conducted to understand the impact of the temperature and thephysical parameters on the device electrical characterizations.
66

Modeling Biosynthesis and Transport of Volatile Organic Compounds in Plants

Shaunak Ray (8801096) 07 May 2020 (has links)
<div>To compensate for their sessile existence, plants synthesize and emit a wide diversity of volatile organic compounds (VOCs) that serve important biological functions pertaining to defense, reproduction, and plant-plant signaling. In addition to their importance in plant secondary metabolism, VOCs are used as fragrances, flavoring agents, and therapeutics. Plant metabolic engineering has successfully been implemented towards the design of value-added plants with enhanced defense, improved aroma and flavor, and increased production of specialty chemicals. However, rational design requires rigorous characterization of the mechanisms controlling metabolic fluxes in a network. Thus, the major aims of this dissertation are to study biological and physical mechanisms controlling the synthesis and emission of plant VOCs. This dissertation focuses on (i) modeling 2-phenylethanol biosynthesis in Arabidopsis and (ii) characterization of the biophysical properties of flower cuticles with respect to the emission of VOCs.</div><div><br></div><div>2-Phenylethanol (2-PE) is a naturally-occurring aromatic volatile with properties that make it a candidate oxygenate for petroleum-derived gasoline. In plants, 2-PE biosynthesis competes with the phenylpropanoid pathway for the common precursor L-phenylalanine (Phe). The phenylpropanoid pathway directs up to 30% of fixed carbon towards the production of lignin, a major constituent of plant cell walls that renders biomass recalcitrant to pretreatment techniques impeding the economical production of biofuels. An initial genetic engineering approach was proposed, whereby a portion of the carbon flux towards lignin production is diverted towards the biosynthesis 2-PE. Transgenic Arabidopsis thaliana expressing enzymes catalyzing the biosynthetic steps from Phe to 2-PE were generated. Excised stems from transgenic Arabidopsis were supplied 13C6-ring labeled Phe, and isotopic enrichment of downstream metabolites were quantified to calculate fluxes. By combining flux measurements with predictions from a kinetic model of the Phe metabolic network, we hypothesized that 2-PE biosynthesis in transgenic Arabidopsis was limited by endogenous pools of cytosolic Phe. Multiple independent genetic strategies were proposed based on model-guided predictions, such as inducing Phe hyper-accumulation, reduction of the activity of the competing phenylpropanoid pathway, and sequestering the 2-PE biosynthesis pathway in plastids. Combining kinetic modeling with time-course in vivo metabolomics led to successful rational engineering of 2-PE accumulating plants.</div><div><br></div><div>The plant cuticle is the physical interface between the flower and its surrounding environment. Passage of VOCs through the cuticle is driven solely by diffusion and is thus dependent on the cuticle physicochemical properties. Wax compounds in the cuticular matrix self-assemble into a multiphase system of crystalline and amorphous regions, where their relative amounts and arrangements govern VOC diffusion. To investigate the effect of wax composition on the crystallinity and permeability of the cuticle, we characterized the cuticular waxes of Petunia hybrida petals using GC-MS, FTIR, DSC, and XRD. Petal waxes were found to be enriched with long-chain hydrocarbons forming semi-crystalline waxes localized on petal surfaces. A ternary system of wax compounds was proposed as a model for petal cuticles to investigate the effect of wax composition on cuticle crystallinity and permeability. Atomistic simulations of VOC displacement in waxes of varying chemical composition were performed at 298 K and 1 bar under NPT conditions to estimate diffusivities. Wax anisotropy was found to be highly dependent on the elongation of methylene chains, restricting the molecular diffusion path. Changes in crystalline symmetry were found to have measurable effects on VOC diffusion. Simulations of compositional variants of the model cuticle shows that changes in relative crystallinity exert differential control on the dynamics of VOC emissions.</div><div><br></div><div>To directly determine the effect of the cuticle on VOC emissions in petunia flowers, the wax exporter PhABCG12 was silenced using RNA interference, resulting in flowers with thinner cuticles. However, VOC emissions were found to have significantly decreased in transgenic flowers relative to the wild-type control. Dewaxing wild-type and transgenic petunia revealed that the cuticle serves as a site of VOC build-up during emission, and deficient coverage limits the extent to which compounds can accumulate. In addition, the cuticle was found to impart differing levels of mass transfer resistance for certain VOCs, suggesting that the cuticle controls the dynamics of VOC emissions. Taken together, petal cuticles provide an additional layer of regulation in emission of VOCs from plants.</div><div><br></div>
67

PHOTOLYTIC LABELING TO PROBE PEPTIDE-MATRIX INTERACTIONS IN LYOPHILIZED SOLIDS

Yuan Chen (5929574) 25 June 2020 (has links)
<p>Therapeutic proteins are often lyophilized with excipients such as sucrose or trehalose to protect them during manufacturing and achieve a longer shelf-life. Formulation design for therapeutic proteins has been a trial-and-error process, and the mechanisms responsible for the stabilizing effects of excipients are not fully understood. Two proposed theories have been widely accepted: the water replacement theory and the vitrification theory.<sup>1,2</sup>The water replacement theory suggests that excipients stabilize protein molecules in the solid state by forming hydrogen bonds that “replace” the hydrogen bonds to water that stabilize the protein in solution, while the vitrification theory asserts that proteins are stabilized by a glassy solid matrix of low mobility and does not require direct interactions between excipient and protein. A better understanding of the interactions between proteins and other components of the lyophilized matrix can facilitate rational formulation design and shorten the time in development. However, most of the analytical methods available can only provide information on the bulk properties of the lyophilized matrix such as moisture content and glass transition temperature (<i>T</i><sub>g</sub>); it has been difficult to measure the interactions between protein and excipient directly, if they exist. In order to characterize the interactions between protein and excipients in a lyophilized matrix with high resolution, a photolytic labeling method was developed in this dissertation, building on previous work in our research group. Photolytic labeling has long been used to identify protein-protein interactions <i>in vivo</i>.<sup>3,4</sup>Common types of photo-reaction reagents and their applications are summarized in Chapter 1. The research described in this dissertation utilizes the diazirine functional group, which is activated after UV exposure and undergoes a free radical reaction to form covalent bonds with nearby molecules. The reaction can be used to identify the interactions between excipients and protein or peptide in a solid formulation. Previous studies in our lab have shown that photo-reaction can be applied to lyophilized solids to study protein-matrix properties and interactions in the solid.<sup>5,6</sup>This dissertation seeks to further identify photo-reaction products and analyze them in a more quantitative way. </p><p> </p><p>Chapter 2 describes a quantitative analysis of photo-reaction products in solution and lyophilized solids using a model peptide, KLQ (Ac-QELHKLQ-NHCH<sub>3</sub>). The purpose of the work in this chapter is to establish a quantitative analytical method for photo-reaction products, enabling studies of peptide-excipient interactions in lyophilized solids. KLQ was derivatized with a bifunctional probe NHS-diazirine (succinimidyl 4,4’-azipentanoate; SDA) at Lys5 to be photo-reactive. The SDA derivatized KLQ (KLQ-SDA) was used to study the photo-reaction products and examine excipient interactions. Identification and quantitation of photo-reaction products of KLQ-SDA was achieved with liquid chromatography mass spectrometry (LC-MS) and reversed phase HPLC (rp-HPLC). Important reaction products such as peptide-excipient adducts and peptide water adducts varied in different formulations. Unexpected reaction products such as unproductive “dead-end” products and peptide-phosphate adducts from buffer salt were also detected and quantified. Together, the photo-reaction products reflected the local environment near Lys5 of the peptide in the solid state. This study has provided a better understanding of photo-reaction with diazirine in the lyophilized solids together with a quantitative description of the local environment near Lys5. </p><p> </p><p>In Chapter 3, the photo-reaction products in lyophilized solids exposed to increasing moisture were analyzed, and the effect of increasing moisture on the local environment near the peptide was examined. Using the analytical method developed in Chapter 2, these studies explored whether peptide-water interactions, as measured by the formation of water adducts formed by photolytic labeling, are linearly correlated with an increase in solid bulk moisture content. Formulations containing the KLQ-SDA peptide were exposed to various relative humidity conditions and photolytic labeling was induced. Solids containing disaccharide excipients behaved differently from those containing amino acids when exposed to the same relative humidity condition, showing different levels of peptide-excipient and peptide-water adducts. With increasing moisture content in the solids, the formation of photo-reaction products did not mimic the pattern of solutions with same composition, indicating differences in the local environment. </p><p> </p><p>An alternative approach to studying lyophilized formulations using photolytic labeling is to incorporate photo-reactive excipients into the solid matrix. In Chapter 4, a new diazirine-labeled photo-excipient, photo-glucosamine (pGlcN), was chemically synthesized and incorporated into formulations of the therapeutic peptide salmon calcitonin (sCT) and compared with the commercially available diazirine-labeled amino acid, photo-leucine (pLeu). The studies in Chapter 4 further compared peptide-excipient interactions at the molecular level with two different photo-excipients, ionizable pLeu and unionizable pGlcN. Changing solution pH prior to lyophilization was expected to change ionic interactions between sCT and pLeu in the solid samples, resulting in different distributions of photo-reactions products; pH-dependent differences were not expected for pGlcN. The results demonstrated that the distribution of photo-reaction products varied with the composition of the formulation and the pH of the solution prior to lyophilization. The photo-reaction products in the pGlcN-containing formulation differed from those pLeu, showing a difference in the interactions of unionizable (pGlcN) and ionizable (pLeu) excipients with sCT in solid samples. </p><p> </p><p>The work in this dissertation has developed photolytic labeling as a tool to study lyophilized peptide formulations, and has provided a more quantitative understanding of the photo-reaction products that are produced from diazirine-labeled peptides or excipients in the solid state. A new photo-reactive excipient has also been presented (pGlcN), which showed different photo-reaction products than a commercially available photo-excipient (pLeu) and is promising for future study. Photolytic labeling for formulation development is still in its early stages, and additional research regarding reaction mechanism and complementary stability studies is needed. Nevertheless, the results presented in this dissertation support continued development of photolytic labeling as a practical method for formulation design and development. </p><p> </p>
68

DETERMINATION OF THE STRUCTURE AND SEQUENCE OF GAS-PHASE PEPTIDES USING SPECTROSCOPIC AND MASS SPECTROMETRIC METHODS

Joshua L Fischer (11115042) 22 July 2021 (has links)
The function of many biological processes depends on the structure and composition of the biomolecules involved. Both spectroscopy and mass spectrometry provide complimentary information regarding the three-dimensional conformation and the composition, respectively, as well as many other things. Here, double resonance conformer specific spectroscopy coupled with the latest ab inito computational methods is used to make structural assignments at the atomic resolution as well obtain information regarding propensities of intramolecular interactions. Additionally, rapid cooling in conjunction with IR excitation to modulate and measure the relative populations of conformers present in the expansion. Two different designer peptide systems are studied, including an achiral acylated 𝛼-aminoisobutryic acid dipeptide (Ac-AIB2-R) with various C-terminal protecting groups (R=NHBn, NHBnF, 𝛼-methylbenzylamine) and an acylated 𝛾4-phenylalanine (Ac-𝛾4Phe-NHMe) with the a methyl amine C-terminal protecting group. Mass spectrometry is used to determine the kinetics of gas-phase covalent tagging reactions used to enhance the sequence coverage. The covalent modification reactions utilize click chemistry between NHS or HOBt substituted sulfobenzoic acid tags with nucleophiles present on the residues of the amino acids composing the backbone. Effective temperatures are approximated using the Tolmachev model, which relates the statistical average internal energy of the molecule to a temperature.
69

Influence of Two-Step Heat Treatments on Microstructure and Mechanical Properties of a β-Solidifying Titanium Aluminide Alloy Fabricated via Electron Beam Powder Bed Fusion

Moritz, Juliane, Teschke, Mirko, Marquardt, Axel, Heinze, Stefan, Heckert, Mirko, Stepien, Lukas, López, Elena, Brueckner, Frank, Walther, Frank, Leyens, Christoph 27 February 2024 (has links)
Additive manufacturing technologies, particularly electron beam powder bed fusion (PBF-EB/M), are becoming increasingly important for the processing of intermetallic titanium aluminides. This study presents the effects of hot isostatic pressing (HIP) and subsequent two-step heat treatments on the microstructure and mechanical properties of the TNM-B1 alloy (Ti–43.5Al–4Nb–1Mo–0.1B) fabricated via PBF-EB/M. Adequate solution heat treatment temperatures allow the adjustment of fully lamellar (FL) and nearly lamellar (NL-β) microstructures. The specimens are characterized by optical microscopy and scanning electron microscopy (SEM), X-ray computed tomography (CT), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical properties at ambient temperatures are evaluated via tensile testing and subsequent fractography. While lack-of-fusion defects are the main causes of failure in the as-built condition, the mechanical properties in the heat-treated conditions are predominantly controlled by the microstructure. The highest ultimate tensile strength is achieved after HIP due to the elimination of lack-of-fusion defects. The results reveal challenges originating from the PBF-EB/M process, for example, local variations in chemical composition due to aluminum evaporation, which in turn affect the microstructures after heat treatment. For designing suitable heat treatment strategies, particular attention should therefore be paid to the microstructural characteristics associated with additive manufacturing.
70

Développement de films extrudés à propriétés spécifiques grâce aux technologies de traitement de surfaces : fluoration, plasma et combinaisons / Development of extruded films with specific properties thanks to surface treatment technologies : fluorination, plasma and combinations

Peyroux, Jérémy 05 February 2015 (has links)
En raison de leurs nombreux avantages, les matériaux polymères sont aujourd'hui reconnus comme des éléments essentiels de notre quotidien. Ils composent une quantité importante d'objets de la vie courante dans lesquels ils ont souvent substitué les substances naturelles initialement utilisées. Néanmoins, pour une utilisation dans le domaine de l’emballage, ces matériaux présentent des contraintes non négligeables qui nécessitent une recherche permanente. L’amélioration et l’optimisation des propriétés d’imprimabilité, barrières aux gaz et de machinabilité représentent un enjeu crucial pour répondre aux nouvelles réglementations, législations mais aussi phénomènes sociétaux et exigences industrielles. La solution d'étude retenue ici est de traiter la surface de matériaux commerciaux. Les différents traitements plasma, relativement bien maitrisés sur ce type de matériaux, ont été combinés avec des procédés de fluoration, plus originaux. La fluoration directe est ainsi apparue comme une solution privilégiée du fait de son efficacité avérée sur ce type de matériaux. La maitrise des différents paramètres intrinsèques à chaque procédé a permis d’identifier l’unicité de chaque traitement et combinaison afin d’ajuster, non seulement la morphologie, mais surtout la composition de surface des films traités en fonction des propriétés ciblées. Des caractérisations spectroscopiques ont tout d’abord été mises en place pour identifier les mécanismes associés à chacun de ses traitements seuls ou combinés. La morphologie des surfaces a également été caractérisée par des techniques classiques de microscopie. Enfin, l’étude des propriétés résultantes et leur stabilité dans le temps ont permis de mettre en évidence l’intérêt de ces procédés pour améliorer les propriétés actuelles des films d’emballages et leur stabilité ; notamment leur imprimabilité, et leur comportement barrière aux gaz. / Currently, polymeric materials are currently well-recognized as essential elements of our daily life due to the advantages that they exhibit, in which they can replace the originally natural products. However, the use of these materials for packaging applications has still significant drawbacks. The interest of research on polymeric materials is potentially required in order to provide a good compromise of properties such as printability, gas barrier and machinability. Aims are to follow the new regulations, laws, but also societal phenomena and industrial phenomena.In this study, surface treatments were directly applied on material polymers dedicated to packaging applications. Plasma treatments, relatively well mastered, were combined with original fluorination processes. In comparison, direct fluorination was effectively used to increase polymer properties. Each treatment and their combination were carried out with various intrinsic parameters under control to adjust both surface morphology and surface composition of treated polymers according to targeted film properties.Spectroscopic characterizations were first monitored to identify the mechanisms associated with each treatment (alone or in combination). Surface morphology was also observed on standard microscopic techniques. The resulting properties and their long-termed stability were carried. These studies highlight the effectiveness of those treatments to improve the current properties of packaging films and stability: including printability, and barrier properties.

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