• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 62
  • 12
  • 8
  • 8
  • 6
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 118
  • 118
  • 26
  • 16
  • 16
  • 13
  • 13
  • 12
  • 11
  • 11
  • 10
  • 10
  • 9
  • 9
  • 9
  • 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.
81

Spectroscopic Analysis of Resin-Bound Peptides: Glutathione and FK-13

Chan, Michael January 2014 (has links)
High-resolution magic angle spinning (HRMAS) NMR spectroscopy is used to study solid samples that are normally difficult to analyze due to broadening of peaks. Solid-phase peptide synthesis can bind peptides to an insoluble resin that can be analyzed with HRMAS NMR spectroscopy. A combination of HRMAS NMR and IRMPD spectroscopy, along with computational chemistry, was applied to analyze and evaluate the structure of resin-bound glutathione. Two-dimensional 1H-1H NMR experiments such as COSY, TOCSY, and ROESY were employed to assign and predict the structure of the resin-bound peptide. IRMPD results were used along with calculated protonated structures and spectra to evaluate the conformation of the peptide. The experimental spectrum was compared to the spectra and structures of the protonated species to hypothesize the most favoured structure. Molecular mechanics, molecular dynamics and DFT calculations were implemented to collect structures that best resembled the free and resin-bound glutathione peptide. The results from these methods were compared to determine the structure that is most probable for the glutathione peptide. A semi-folded conformation is the structure the resin-bound GSH most preferred as concluded from the NMR and DFT results. The IRMPD results were analyzed as separate from the resin-bound experiments and suggested protonated GSH had a folded conformation. FK-13 was another peptide synthesized using the solid-phase peptide synthesis technique. The peptide was synthesized using a modified technique different from conventional methodology used in the past. The peptide was also analyzed using COSY, TOCSY, and ROESY to confirm that the synthesis was done correctly and hypothesize a structure. The low substitution of the peptide on the resin gave rise to minimal NOE interactions, but there was some evidence suggesting that the synthesis was successful and the peptide adopted a cyclic conformation. These initial results are useful for future analyses and conformational studies of this resin-bound peptide. Further work needs to be done for both peptides to explore the structures in more detail. The explicit model of solvation should be used to explore the effect of solvent molecules on the conformation of the glutathione peptide as opposed to the implicit model that PCM provides. FK-13 could be synthesized better so that a higher substitution is achieved and better NMR results are obtained. The IRMPD results obtained by the McMahon group can then be compared to the NMR results and computational calculations can be performed to obtain realistic structures of the peptide.
82

Analýza stáda a vlivů působících na reprodukční užitkovost prasnic

MUŽÍKOVÁ, Martina January 2017 (has links)
The aim was selected in a commercial breeding (AGRO Vodňany a.s.) to analyze and evaluate herd reproductive performance of sows used for the production of piglets (final hybrids). The analysis was focused on the age structure of the sow, when the first and second litter was 28.8% on the 3rd to 5th litter 23.5% and the sixth and other litters of sows 47.7%.The annual renewal of the herd was culled 22.9% and 25.5% included sows for breeding.This breeding is used natural reproduction, where for the purposes of reproduction bred four boars lines of 48 (White paternity x Pietrain).The average gestation length breeding was 115.2 of days. In 2016, it was born an average of 13.8 piglet per litter, of which 11.5 piglet of live and been preserved was 10.2 piglet per litter.The length of the farrowing interval was 171,1 days and the onset of estrus after weaning piglets was an average of 4.9 days.Weaning is in monitored husbandry carried out between 28 to 31 day age of piglets.Part of this work was to evaluate zoohygiene also at stud and compared with the results of performance farms in the Czech Republic and recommendations for improving the results of husbandry evaluated. When comparing the results of selected indicators identified in Agro Vodňany a.s. with selected data published by the Czech Statistical Office for the South Bohemian Region and the Czech Republic in 2016, it was found that the number of piglets born per sow in the Czech Republic was 30.1 piglets. Piglets was born25.1 in South Bohemia and 24.3piglets was born per sow in Vodňany. The death of piglets from the number of births in the Czech Republic was 10.6% in the South Region accounted for 15.6% and in Vodňany it was 11.9%.The number of surviving piglets per sow in the Czech Republic was 26.9 piglets in South Bohemia have been preserved 21.3 piglet per sow and Vodnany during the reporting period have been preserved 21.4 piglets per sow.
83

Inferences on Structure and Function of Proteins from Sequence Data : Development of Methods and Applications

Mudgal, Richa January 2015 (has links) (PDF)
Structural and functional annotation of sequences of putative proteins encoded in the newly sequenced genomes pose an important challenge. While much progress has been made towards high throughput experimental techniques for structure determination and functional assignment to proteins, most of the current genome-wide annotation systems rely on computational methods to derive cues on structure and function based on relationship with related proteins of known structure and/or function. Evolutionary pressure on proteins, forces the retention of sequence features that are important for structure and function. Thus, if it can be established that two proteins have descended from a common ancestor, then it can be inferred that the structural fold and biological function of the two proteins would be similar. Homology based information transfer from one protein to another has played a central role in the understanding of evolution of protein structures, functions and interactions. Many algorithmic improvements have been developed over the past two decades to recognize homologues of a protein from sequence-based searches alone, but there are still a large number of proteins without any functional annotation. The sensitivity of the available methods can be further enhanced by indirect comparisons with the help of intermediately-related sequences which link related families. However, sequence-based homology searches in the current protein sequence space are often restricted to the family members, due to the paucity of natural intermediate sequences that can act as linkers in detecting remote homologues. Thus a major goal of this thesis is to develop computational methods to fill up the sparse regions in the protein sequence space with computationally designed protein-like sequences and thereby create a continuum of protein sequences, which could aid in detecting remote homologues. Such designed sequences are further assessed for their effectiveness in detection of distant evolutionary relationships and functional annotation of proteins with unknown structure and function. Another important aspect in structural bioinformatics is to gain a good understanding of protein sequence - structure - function paradigm. Functional annotations by comparisons of protein sequences can be further strengthened with the addition of structural information; however, instances of functional divergence and convergence may lead to functional mis-annotations. Therefore, a systematic analysis is performed on the fold–function associations using binding site information and their inter-relationships using binding site similarity networks. Chapter 1 provides a background on proteins, their evolution, classification and structural and functional features. This chapter also describes various methods for detection of remote similarities and the role of protein sequence design methods in detection of distant relatives for protein annotation. Pitfalls in prediction of protein function from sequence and structure are also discussed followed by an outline of the thesis. Chapter 2 addresses the problem of paucity of available protein sequences that can act as linkers between distantly related proteins/families and help in detection of distant evolutionary relationships. Previous efforts in protein sequence design for remote homology detection and design of sequences corresponding to specific protein families are discussed. This chapter describes a novel methodology to computationally design intermediately-related protein sequences between two related families and thus fill-in the gaps in the sequence space between the related families. Protein families as defined in SCOP database are represented as position specific scoring matrices (PSSMs) and these profiles of related protein families within a fold are aligned using AlignHUSH -a profile-profile alignment method. Guided by this alignment, the frequency distribution of the amino acids in the two families are combined and for each aligned position a residue is selected based on the combined probability to occur in the alignment positions of two families. Each computationally designed sequence is then subjected to RPS-BLAST searches against an all profile pool representing all protein families. Artificial sequences that detect both the parent profiles with no hits corresponding to other folds qualify as ‘designed intermediate sequences’. Various scoring schemes and divergence levels for the design of protein-like sequences are investigated such that these designed sequences intersperse between two related families, thereby creating a continuum in sequence space. The method is then applied on a large scale for all folds with two or more families and resulted in the design of 3,611,010 intermediately-related sequences for 27,882 profile-profile alignments corresponding to 374 folds. Such designed sequences are generic in nature and can be augmented in any sequence database of natural protein sequences. Such enriched databases can then be queried using any sequence-based remote homology detection method to detect distant relatives. The next chapter (Chapter 3) explores the ability of these designed intermediate sequences to act as linkers of two related families and aid in detection of remote homologues. To assess the applicability of these designed sequences two types of databases have been generated, namely a CONTROL database containing protein sequences from natural sequence databases and an AUGMENTED database in which designed sequences are included in the database of natural sequences. Detailed assessments of the utility of such designed sequences using traditional sequence-based searches in the AUGMENTED database showed an enhanced detection of remote homologues for almost 74% of the folds. For over 3,000 queries, it is demonstrated that designed sequences are positioned as suitable linkers, which mediate connections between distantly related proteins. Using examples from known distant evolutionary relationships, we demonstrate that homology searches in augmented databases show an increase of up to 22% in the number of /correct evolutionary relationships "discovered". Such connections are reported with high sensitivities and very low false positive rates. Interestingly, they fill-in void and sparse regions in sequence space and relate distant proteins not only through multiple routes but also through SCOP-NrichD database, SUPFAM+ database, SUPERFAMILY database, protein domain library queried by pDomTHREADER and HHsearch against HMM library of SCOP families. This approach detected evolutionary relationships for almost 20% of all the families with no known structure or function. Detailed report of predictions for 614 DUFs, their fold and species distribution are provided in this chapter. These predictions are then enriched with GO terms and enzyme information wherever available. A detailed discussion is provided for few of the interesting assignments: DUF1636, DUF1572 and DUF2092 which are functionally annotated as thioredoxin-like 2Fe-2S ferredoxin, putative metalloenzyme and lipoprotein localization factors respectively. These 614 novel structure-function relationships of which 193 are supported by consensus between at least two of the five methods, can be accessed from http://proline.biochem.iisc.ernet.in/RHD_DUFS/. Protein functions can be appreciated better in the light of evolutionary information from their structures. Chapter 6 describes a database of evolutionary relationships identified between Pfam families. The grouping of Pfam families is important to obtain a better understanding on evolutionary relationships and in obtaining clues to functions of proteins in families of yet unknown function. Many structural genomics initiative projects have made considerable efforts in solving structures and bridging the growing gap between protein sequences and their structures. The results of such experiments suggest that often the newly solved structure using X-ray crystallography or NMR methods has structural similarity to a protein with already known structure. These relationships often remain undetected due to unavailability of structural information. Therefore, SUPFAM+ database aims to detect such distant relationships between Pfam families by mapping the Pfam families and SCOP domain families. The work presented in this chapter describes the generation of SUPFAM+ database using a sensitive AlignHUSH method to uncover hidden relationships. Firstly, Pfam families are queried against a profile database of SCOP families to derived Pfam-SCOP associations, and then Pfam families are queried against Pfam database to derive Pfam-Pfam relationships. Pfam families that remain without a mapping to a SCOP family are mapped indirectly to a SCOP family by identifying relationships between such Pfam families and other Pfam families that are already mapped to a SCOP family. The criteria are kept stringent for these mappings to minimize the rate of false positives. In case of a Pfam family mapping to two or more SCOP superfamilies, a decision tree is implemented to assign the Pfam family to a single SCOP superfamily. Using these direct and indirect evolutionary relationships present in the SCOP database, associations between Pfam families are derived. Therefore, relationship between two Pfam families that do not have significant sequence similarity can be identified if both are related to same SCOP superfamily. Almost 36% of the Pfam families could be mapped to SCOP families through direct or indirect association. These Pfam-SCOP associations are grouped into 1,646 different superfamilies and cataloguing changes that occur in the binding sites between two functions, which are analysed in this study to trace possible routes between different functions in evolutionarily related enzymes. The main conclusions of the entire thesis are summarized in Chapter 8, contributing in the area of remote homology detection from sequence information alone and understanding the ‘sequence-structure-function’ paradigm from a binding site perspective. The chapter illustrates the importance of the work presented here in the post-genomic era. The development of the algorithm for the design of ‘intermediately-related sequences’ that could serve as effective linkers in remote homology detection, its subsequent large scale assessment and amenability to be augmented into any protein sequence database and exploration by any sequence-based search method is highlighted. Databases in the NrichD resource are made available in the public domain along with a portal to design artificial sequence for or between protein families. This thesis also provides useful and meaningful predictions for protein families with yet unknown structure and function using NrichD database as well as four other state-of-the-art sequence-based remote homology detection methods. A different aspect addressed in this thesis provides a fundamental understanding of the relationships between protein structure and functions. Evolutionary relationships between functional families are identified using the inherent structural information for these families and fold-function relationships are studied from a perspective of similarities in their binding sites. Such studies help in the area of functional annotation, polypharmacology and protein engineering. Chapter 2 addresses the problem of paucity of available protein sequences that can act as linkers between distantly related proteins/families and help in detection of distant evolutionary relationships. Previous efforts in protein sequence design for remote homology detection and design of sequences corresponding to specific protein families are discussed. This chapter describes a novel methodology to computationally design intermediately-related protein sequences between two related families and thus fill-in the gaps in the sequence space between the related families. Protein families as defined in SCOP database are represented as position specific scoring matrices (PSSMs) and these profiles of related protein families within a fold are aligned using AlignHUSH -a profile-profile alignment method. Guided by this alignment, the frequency distribution of the amino acids in the two families are combined and for each aligned position a residue is selected based on the combined probability to occur in the alignment positions of two families. Each computationally designed sequence is then subjected to RPS-BLAST searches against an all profile pool representing all protein families. Artificial sequences that detect both the parent profiles with no hits corresponding to other folds qualify as ‘designed intermediate sequences’. Various scoring schemes and divergence levels for the design of protein-like sequences are investigated such that these designed sequences intersperse between two related families, thereby creating a continuum in sequence space. The method is then applied on a large scale for all folds with two or more families and resulted in the design of 3,611,010 intermediately-related sequences for 27,882 profile-profile alignments corresponding to 374 folds. Such designed sequences are generic in nature and can be augmented in any sequence database of natural protein sequences. Such enriched databases can then be queried using any sequence-based remote homology detection method to detect distant relatives. The next chapter (Chapter 3) explores the ability of these designed intermediate sequences to act as linkers of two related families and aid in detection of remote homologues. To assess the applicability of these designed sequences two types of databases have been generated, namely a CONTROL database containing protein sequences from natural sequence databases and an AUGMENTED database in which designed sequences are included in the database of natural sequences. Detailed assessments of the utility of such designed sequences using traditional sequence-based searches in the AUGMENTED database showed an enhanced detection of remote homologues for almost 74% of the folds. For over 3,000 queries, it is demonstrated that designed sequences are positioned as suitable linkers, which mediate connections between distantly related proteins. Using examples from known distant evolutionary relationships, we demonstrate that homology searches in augmented databases show an increase of up to 22% in the number of /correct evolutionary relationships "discovered". Such connections are reported with high sensitivities and very low false positive rates. Interestingly, they fill-in void and sparse regions in sequence space and relate distant proteins not only through multiple routes but also through SCOP-NrichD database, SUPFAM+ database, SUPERFAMILY database, protein domain library queried by pDomTHREADER and HHsearch against HMM library of SCOP families. This approach detected evolutionary relationships for almost 20% of all the families with no known structure or function. Detailed report of predictions for 614 DUFs, their fold and species distribution are provided in this chapter. These predictions are then enriched with GO terms and enzyme information wherever available. A detailed discussion is provided for few of the interesting assignments: DUF1636, DUF1572 and DUF2092 which are functionally annotated as thioredoxin-like 2Fe-2S ferredoxin, putative metalloenzyme and lipoprotein localization factors respectively. These 614 novel structure-function relationships of which 193 are supported by consensus between at least two of the five methods, can be accessed from http://proline.biochem.iisc.ernet.in/RHD_DUFS/. Protein functions can be appreciated better in the light of evolutionary information from their structures. Chapter 6 describes a database of evolutionary relationships identified between Pfam families. The grouping of Pfam families is important to obtain a better understanding on evolutionary relationships and in obtaining clues to functions of proteins in families of yet unknown function. Many structural genomics initiative projects have made considerable efforts in solving structures and bridging the growing gap between protein sequences and their structures. The results of such experiments suggest that often the newly solved structure using X-ray crystallography or NMR methods has structural similarity to a protein with already known structure. These relationships often remain undetected due to unavailability of structural information. Therefore, SUPFAM+ database aims to detect such distant relationships between Pfam families by mapping the Pfam families and SCOP domain families. The work presented in this chapter describes the generation of SUPFAM+ database using a sensitive AlignHUSH method to uncover hidden relationships. Firstly, Pfam families are queried against a profile database of SCOP families to derived Pfam-SCOP associations, and then Pfam families are queried against Pfam database to derive Pfam-Pfam relationships. Pfam families that remain without a mapping to a SCOP family are mapped indirectly to a SCOP family by identifying relationships between such Pfam families and other Pfam families that are already mapped to a SCOP family. The criteria are kept stringent for these mappings to minimize the rate of false positives. In case of a Pfam family mapping to two or more SCOP superfamilies, a decision tree is implemented to assign the Pfam family to a single SCOP superfamily. Using these direct and indirect evolutionary relationships present in the SCOP database, associations between Pfam families are derived. Therefore, relationship between two Pfam families that do not have significant sequence similarity can be identified if both are related to same SCOP superfamily. Almost 36% of the Pfam families could be mapped to SCOP families through direct or indirect association. These Pfam-SCOP associations are grouped into 1,646 different superfamilies and cataloguing changes that occur in the binding sites between two functions, which are analysed in this study to trace possible routes between different functions in evolutionarily related enzymes. The main conclusions of the entire thesis are summarized in Chapter 8, contributing in the area of remote homology detection from sequence information alone and understanding the ‘sequence-structure-function’ paradigm from a binding site perspective. The chapter illustrates the importance of the work presented here in the post-genomic era. The development of the algorithm for the design of ‘intermediately-related sequences’ that could serve as effective linkers in remote homology detection, its subsequent large scale assessment and amenability to be augmented into any protein sequence database and exploration by any sequence-based search method is highlighted. Databases in the NrichD resource are made available in the public domain along with a portal to design artificial sequence for or between protein families. This thesis also provides useful and meaningful predictions for protein families with yet unknown structure and function using NrichD database as well as four other state-of-the-art sequence-based remote homology detection methods. A different aspect addressed in this thesis provides a fundamental understanding of the relationships between protein structure and functions. Evolutionary relationships between functional families are identified using the inherent structural information for these families and fold-function relationships are studied from a perspective of similarities in their binding sites. Such studies help in the area of functional annotation, polypharmacology and protein engineering.
84

Análise de vigas mistas de aço e concreto semicontí­nuas em situação de incêndio. / Composite steel and concrete semicontinuous beams analysis under fire.

Lucas Coscia Romagnoli 21 June 2018 (has links)
Na Dissertação de Mestrado foi realizado um estudo sobre o comportamento de vigas mistas de aço e concreto biapoiadas sob iteração completa, compostas por perfis classificados como compactos em situação de incêndio. Apesar de ditas biapoiadas, a ideia principal da Dissertação é considerar, na análise em situação de incêndio, a reserva de capacidade existente nas extremidades dessas vigas, usualmente desprezada no dimensionamento à temperatura ambiente, provinda da continuidade da armadura longitudinal negativa presente na laje de concreto, sendo possível dispensar o revestimento contra fogo nesses elementos. Serão abordados, de início, os métodos de dimensionamento ao Estado-Limite Último de vigas mistas à temperatura ambiente, a fim de explicar o comportamento estrutural desse tipo de elemento, dando base para a posterior análise térmica. A análise térmica foi realizada, em uma primeira etapa, por métodos simplificados segundo normas vigentes e tomando hipóteses simplificadoras em que se desprezam esforços indiretos provocados pela dilatação térmica e gradiente térmico, sendo possível aplicar os conceitos no dia a dia de projeto. Numa segunda etapa foi realizada análise termestrutural com modelos numéricos para estudar o comportamento e colapso da viga, sendo os resultados suficientes para validar os valores de TRF encontrados por análise simplificada seguindo métodos normativos. Como conclusão, o ganho de capacidade estrutural da viga, proporcionado pela adoção da ligação mista no apoio, foi suficiente para situações de TRRFs entre 15 min e 21 min, no caso de perfis mais leves, com geometria própria para serem utilizados como vigas de piso de edifícios. Análises mostraram que não é possível justificar a ausência de revestimento contra incêndio para TRRFs de 30 min ou superiores. Tempos inferiores podem ser adotados de acordo com o denominado método do tempo equivalente, limitado a 15 min e são mais usuais para edificações de pequeno porte. / A study will be carried out on the behavior of simply supported, full interaction composite steel and concrete beams composed by compact profiles in fire situation. Despite being designed as simply supported, the main idea is to consider, in the fire situation analysis, the moment resistance capacity reserve on the beam supports, usually neglected during room temperature design, due to the upper longitudinal reinforcement present in the concrete slab, being possible to dispense fireproof coating in these elements. First, room temperature design procedures of composite beams will be approached in order to explain the structural behavior of this type of elements, providing a basis for subsequent thermal analysis. The thermal analysis will be carried out, in a first stage, by simplified methods according to design procedures and adopting simplifying hypotheses in which indirect stresses caused by thermal expansion and thermal gradient are neglected, being possible to apply those concepts in structural design offices. In a second step, thermal stress analyses were performed with aid of numerical models to study the structural behavior and collapse time of the beam. The results were sufficient to validate the fire resistance time values found by the simplified analysis following design methods. As a conclusion, the structural capacity increase of the beam, provided by the adoption of the composite connection at the support in case of lighter steel profiles usually chosen to be used as buildings floor beams, was sufficient for situations of standard fire resistance requirements between 15 min and 21 min. Analyzes have shown that it is not possible to justify the absence of fire resistant coating for standard fire resistance requirements of 30 min or higher. Lower times can be adopted according to the so-called equivalent time method, limited to 15 min, which are more common for small buildings.
85

Flamelet/progress variable modelling and flame structure analysis of partially premixed flames

Hartl, Sandra 13 September 2017 (has links) (PDF)
This dissertation addresses the analysis of partially premixed flame configurations and the detection and characterization of their local flame regimes. First, the identification of flame regimes in experimental data is intensively discussed. Current methods for combustion regime characterization, such as the flame index, rely on 3D gradient information that is not accessible with available experimental techniques. Here, a method is proposed for reaction zone detection and characterization, which can be applied to instantaneous 1D Raman/Rayleigh line measurements of major species and temperature as well as to the results of laminar and turbulent flame simulations, without the need for 3D gradient information. Several derived flame markers, namely the mixture fraction, the heat release rate and the chemical explosive mode, are combined to detect and characterize premixed versus non-premixed reaction zones. The methodology is developed and evaluated using fully resolved simulation data from laminar flames. The fully resolved 1D simulation data are spatially filtered to account for the difference in spatial resolution between the experiment and the simulation, and experimental uncertainty is superimposed onto the filtered numerical results to produce Raman/Rayleigh equivalent data. Then, starting from just the temperature and major species, a constrained homogeneous batch reactor calculation gives an approximation of the full thermochemical state at each sample location. Finally, the chemical explosive mode and the heat release rate are calculated from this approximated state and compared to those calculated directly from the simulation data. After successful validation, the approach is applied to Raman/Rayleigh line measurements from laminar counterflow flames, a mildly turbulent lifted flame and turbulent benchmark cases. The results confirm that the reaction zones can be reliably detected and characterized using experimental data. In contrast to other approaches, the presented methodology circumvents uncertainties arising from the use of limited gradient information and offers an alternative to known reaction zone identification methods. Second, this work focuses on the flame structure of partially premixed dimethyl ether (DME) flames. DME flames form significant intermediate hydrocarbons in the reaction zone and are classified as the next more complex fuel candidate in research after methane. To simulate DME combustion processes, accurate predictions by computational combustion models are required. To evaluate such models and to identify appropriate flame regimes, numerical simulations are necessary. Therefore, fully resolved simulations of laminar dimethyl ether flames, defined by different levels of premixing, are performed. Further, the qualitative two-dimensional structures of the partially premixed DME flames are discussed and analyses are carried out at selected slices and compared to each other as well as to experimental data. Further, the flamelet/progress variable (FPV) approach is investigated to predict the partially premixed flame structures of the DME flames. In the context of the FPV approach, a rigorous analysis of the underlying manifold is carried out based on the newly developed regime identification approach and an a priori analysis. The most promising flamelet look-up table is chosen for the fully coupled tabulated chemistry simulations and the results are further compared to the fully resolved simulation data.
86

Low Temperature Oxygen Mobility Applied to Catalysis / Mobilité de l’oxygène à basse température appliquée à la catalyse

Penkala, Bartosz 06 November 2015 (has links)
Accomplir les spécifications des nouvelles réglementations concernant les gaz d'échappement de post-traitement des technologies automobiles, par exemple, TWC, implique la disponibilité et l'utilisation de matériaux catalytiquement actifs et notamment des composés tampons d'oxygène, ce qui peut réversible stocker et libérer de grandes quantités de l'oxygène. Oxyde de cérium dopé présente encore aujourd'hui le seul composé de référence pour un support approprié, en raison de sa grande capacité de stockage de l'oxygène et possibilité de créer facilement des lacunes en ions d'oxygène. Cependant, pour des raisons économiques et de l'abondance naturelle très limitée à quelques pays, la substitution de l'oxyde de cérium semble être obligatoire; Dans ce contexte, nous notons que l'oxyde de cérium est partie de la liste des 13 matières premières économiquement importants qui ont été identifiés par la Commission européenne comme soumis à un risque élevé d'interruption de l'alimentation. Dans ce contexte, les oxydes de type brownmillérite sont d'un intérêt potentiel, car ils révèlent oxygène mobilité ionique jusqu'à la température ambiante. En outre, ils permettent de régler la présence de défauts étendus par exemple frontières anti-phase au cours de conditions de synthèse, et qui se sont avérés diminuer de manière significative l'énergie d'activation pour la diffusion d'oxygène. Nous avons ainsi pu montrer que vice-riche nano-Ca2Fe2O5, traditionnellement connue comme une ligne phase stoechiométrique, peut être oxydé dans des conditions douces à CaFeO3, tandis que l'oxydation de Ca2Fe2O5 ordinaire nécessite généralement des conditions de réaction extrême, soit 1100 ° C et plusieurs GPa pression partielle d'oxygène. Ainsi, l'introduction d'une forte concentration de défauts semble être un concept prometteur pour transformer ligne phases stoechiométriques même traditionnellement connus pour devenir une sorte d'éponge de l'oxygène et de se comporter en tant que composé de stockage / tampon d'oxygène à des températures très modérées. Ce comportement est donc comparable à la capacité de stockage d'oxygène d'oxyde de cérium dopé, et dispose d'un potentiel réel pour l'application dans la catalyse. Par conséquent, le brownmillérite Ca2Fe2O5 semble être un candidat prometteur pour étudier en raison de ses oxygène connue propriétés de conductivité ionique.Objectif principal de ce travail est d'établir la relation fondamentale entre structure / microstructure, propriétés de mobilité de l'oxygène et de l'activité catalytique, simultanément entrepris pour deux systèmes: Ca2Fe2O5 avec la structure brownmillérite-type et CeO2 avec une structure de type fluorite. Nous essentiellement exploré les critères sous-jacents qui régissent leur composition chimique / activité catalytique, utilisant de l'oxygène comportement d'échange des isotopes par TG expériences couples de MS. D'autres études utilisant la spectroscopie Raman essentiellement permis de conclure à partir d'une dynamique de réseau modifiées pour différents isotopes de l'oxygène à la différence entre masse et la participation à l'oxygène de la surface au mécanisme d'oxydation du CO en CO2. Pour une meilleure compréhension mécaniste de l'oxydation de CO, nous avons développé un nouveau test catalytique, par rapport à une variation dynamique de la pression partielle d'oxygène dans le récipient de réaction, ce qui permet de conclure à la fois sur l'activité catalytique du catalyseur et sa libération de l'oxygène / comportement absorption , non accessible par le test d'activité catalytique classique interprétée sous un flux de gaz constant. De cette façon, nous avons eu un nouvel aperçu de différencier la participation de la surface et de l'activité vrac d'oxygène pour les catalyseurs à base d'oxyde de cérium et Ca2Fe2O5 différente. / Accomplishing specifications of new regulations regarding automotive exhaust after-treatment technologies, e.g. TWC, imply the availability and usage of catalytically active materials and especially oxygen buffer compounds, which can reversibly store and release high quantities of the oxygen. Doped cerium oxide presents still today the only reference compound for a suitable support, due to its high oxygen storage capacity and ability to easily create oxygen ion vacancies. However, for economic reasons and very limited natural abundance to a few countries, the substitution of ceria appears to be mandatory; in this context we note that ceria is part of the list of 13 economically important raw materials which were identified by the European Commission as subject to a high risk of supply interruption.In this context, Brownmillerite-type oxides are of potential interest, since they reveal oxygen ion mobility down to ambient temperature. Furthermore, they allow to adjust the presence of extended defects e.g. anti-phase boundaries, during synthesis conditions, and which have been shown to significantly decrease the activation energy for oxygen diffusion. We were thus able to show that defect-rich nano-Ca2Fe2O5, traditionally known as a stoichiometric line-phase, can be oxidized under mild conditions to CaFeO3, while the oxidation of ordinary Ca2Fe2O5 usually requires extreme reaction conditions, i.e. 1100°C and several GPa oxygen partial pressure. Thus, introducing a high concentration of defects seems to be a promising concept to transform even traditionally known stoichiometric line-phases to become a kind of oxygen sponge and behave as oxygen storage/buffer compound at very moderate temperatures. This behavior is thus comparable to the oxygen storage capacity of doped cerium oxide, and offers a true potential for application in the catalysis. Consequently, the Brownmillerite Ca2Fe2O5 appears to be a promising candidate to study due to its known oxygen ion conductivity properties.Primary aim of this work is to establish fundamental relation between structure/microstructure, oxygen mobility properties and catalytic activity, simultaneously undertaken for two systems: Ca2Fe2O5 with Brownmillerite-type structure and CeO2 with Fluorite-type structure. We essentially explored the underlying criteria governing their chemical/catalytic activity, using oxygen isotope exchange behavior by TG couples MS experiments. Further studies using essentially Raman spectroscopy allowed concluding from a modified lattice dynamics for different oxygen isotopes to differentiate between bulk and surface oxygen participation to the oxidation mechanism of CO to CO2. For a deeper mechanistic understanding of the CO oxidation, we developed a new catalytic test, based on a dynamic variation of the oxygen partial pressure in the reaction vessel, allowing to conclude simultaneously on the catalytic activity of the catalyst and its oxygen release/uptake behavior, not accessible by the classical catalytic activity test performed under constant gas flow. In this way we got a new insight to differentiate the participation of surface and bulk oxygen activity for different Ca2Fe2O5 and ceria based catalysts.
87

Návrh systému řízení rekreačního zařízení / Proposal of a solution for a recreational facility management system

Valová, Anežka January 2017 (has links)
The aim of this masters thesis is to propose a new organizational structure of the hotel castle Valeč and to evaluate its financial situation. In order to assess the financial situation, financial methods such as horizontal and vertical analysis, cost-effectiveness, return on revenues and accommodation indicators (occupancy, average price per room and price for the available room) are applied to the enterprise. The thesis consists of a theoretical and practical parts. The theoretical part defines methods of management of small and medium enterprises, which include marketing strategy, financial management, management of the company development and growth. It is followed by a practical part, which contains a description of the hotel castle Valeč, a SWOT analysis, a financial analysis and an analysis of the current state of the organizational structure. In the conclusion of the masters thesis, problems are identified based on these analyses and changes in the organizational structure are proposed.
88

Comparing Three Effect Sizes for Latent Class Analysis

Granado, Elvalicia A. 12 1900 (has links)
Traditional latent class analysis (LCA) considers entropy R2 as the only measure of effect size. However, entropy may not always be reliable, a low boundary is not agreed upon, and good separation is limited to values of greater than .80. As applications of LCA grow in popularity, it is imperative to use additional sources to quantify LCA classification accuracy. Greater classification accuracy helps to ensure that the profile of the latent classes reflect the profile of the true underlying subgroups. This Monte Carlo study compared the quantification of classification accuracy and confidence intervals of three effect sizes, entropy R2, I-index, and Cohen’s d. Study conditions included total sample size, number of dichotomous indicators, latent class membership probabilities (γ), conditional item-response probabilities (ρ), variance ratio, sample size ratio, and distribution types for a 2-class model. Overall, entropy R2 and I-index showed the best accuracy and standard error, along with the smallest confidence interval widths. Results showed that I-index only performed well for a few cases.
89

Řízení nákladů developerské činnosti / Cost management development activities

Smola, Albert January 2015 (has links)
This thesis takes the form of two separate fractions. Theoretical context, in which the real estate developer, the construction project is defined, costs in connection therewith arise are characterized and also methods for analyzing these costs are mentioned, is Chapter 1. Practical fraction consisting of a cost analysis of model development company and model construction project, forms Chapter 2 and Chapter 3. In conclusion, the practical analysis outputs are interpreted and some recommendations to optimize costs are presented.
90

Využití molekulárních simulací při komplexní strukturní analýze vrstevnatých materiálů / Application of Molecular Simulations in Complex Structural Analysis of Layered Materials

Veteška, Marek January 2015 (has links)
Title: Application of Molecular Simulations in Complex Structural Analysis of Layered Materials Author: RNDr. Marek Veteška Department: Department of Chemical Physics and Optics Supervisor: RNDr. Miroslav Pospíšil, Ph.D., Dept. of Chemical Physics and Optics Abstract: Techniques of molecular simulations were used together with experimental measurements (X-ray diffraction, thermogravimetry, infrared spectroscopy, elemental analysis and others) to clarify the structure properties of various types of layered materials. The structure of Zn-Al-layered double hydroxide intercalated by pyrenetetra- sulfonate acid was solved. Depending on the relative humidity, the samples showed different arrangements with three planes of water molecules and with either one or two planes of pyrenetetrasulfonate anions. At the same time considerable variability of anions arrangement was demonstrated. The adsorption behavior of natural montmorillonite and montmorillonite modified by tetramethylammonium cations in relation to aniline and phe- nol was explored. Adsorption features differed according to both the type of adsorbed molecules and the type of adsorbents. An important role was played by the plane of water molecules right above the surface which medi- ated adsorption of anilines. The water plane area was reduced by...

Page generated in 0.0702 seconds