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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

Derivation and application of response functions for nonlinear absorption and dichroisms

Fahleson, Tobias January 2017 (has links)
This thesis explores and expands upon theoretical means of quantifying a number of nonlinear spectroscopies, including two-photon absorption, resonant-inelastic x-ray scattering, Jones birefringence, and magnetic circular dichroism. On top of that, detailed information is given for the derivation and program implementation of damped cubic response functions. Complex-valued cubic response functions have been implemented in the quantum chemistry package DALTON, based on working equations formulated for an approximate-state wave function. An assessment of the implementation, such that for small frequencies the second-order hyperpolarizability should behave according to an analytic function that depends quadratically on the optical frequencies. It is demonstrated how two-photon absorption (TPA) can be described either through second-order transition moments or via the damped cubic response function. A few calculated TPA profiles are produced for a set of smaller molecules, in order to display the capability of the cubic response function in the x-ray frequency region. Resonance-inelastic x-ray scattering (RIXS) is explored in a similar manner as two-photon absorption. It is shown how the second-order hyperpolarizability can represent RIXS in the limit of intermediate-state and final-state resonances. Complications emerging from the complex dispersion of the hyperpolarizability are discussed. Moreover, linear birefringences, with focus on the Jones birefringence, are investigated for noble gases, monosubstituted benzenes, furan homologues, and a pure acetonitrile liquid. A linear relation between the Jones birefringence and the empirical para-Hammett constant as well as the permanent electric dipole moment is presented. Estimations of three linear birefringences --- Kerr, Cotton--Mouton, and Jones ---are obtained by averaging over a set of liquid snapshots. The Jones effect for acetonitrile turns out to be unusually large inmparison to the other two investigated linear birefringences. The final chapter of the thesis investigates magnetically induced circular dichroism (MCD). A question regarding relative stability of the first set of excited states for DNA-related molecular systems is resolved through MCD by exploiting the signed nature of circular dichroisms. Furthermore, to what extent solvent contributions affect MCD spectra is explored. The effect on uracil MCD spectrum due to thionation is studied, for which the degree of redshifting for systems 2-thiouracil and 4-thiouracil can be seen to be addative as compared to the 2,4-dithiouracil system. / <p>QC 20171129</p>
62

Photophysical studies of silver(I), platinum(II), palladium(II), and nickel(II) complexes and their use in electronic devices.

Hudson, Joshua M. 12 1900 (has links)
This dissertation deals with two major topics that involve spectroscopic studies of (a) divalent group 10 metals and (b) silver(I)-phosphine complexes. The scope of the work involved the delineation of the electronic structure of these complexes in different environments and their use in electronic devices. The first topic is a look at the luminescence of tetrahedral silver(I)-phosphine complexes. Broad unstructured emissions with large Stokes shifts were found for these complexes. Computational analysis of the singlet and triplet state geometries suggests that this emission is due to a Jahn-Teller type distortion. The second topic represents the major thrust of this research, which is an investigation into the electronic structure of M(diimine)X2 (M= Pt(II), Pd(II), or Ni(II); X = dichloro, or dithiolate ligands) complexes and their interactions with an electron acceptor or Lewis acid. Chapter 3 assesses the use of some of these complexes in dye sensitized solar cells (DSSCs); it is shown that these complexes may lead to a viable alternative to the more expensive ruthenium-based dyes that are being implemented now. Chapter 4 is an investigation into donor/acceptor pairs involving this class of complexes, which serves as a feasibility test for the use of these complexes in organic photo-voltaics (OPVs) and thin-film field-effect transistors (OTFTs). The mixing of a donor Pt molecule with an electron deficient nitrofluorenone gives rise to new absorption bands in the NIR region. Computational studies of one of the solids suggest that these complexes may have metallic behavior. Chapter 5 demonstrates association in solution, previously unobserved, for Pt(diimine)Cl2 complexes. This chapter is an investigation into the effects of the association mode for this class of complexes on the absorption and emission properties. One of the complexes was used as the emitter in organic light emitting diodes (OLEDs). The results of this study show that these complexes have tunable absorption and emission energies that are concentration dependant. The concentration dependence of the absorption and emission energies is utilized in the OLED device where association enhances the performance.
63

Efecto del tratamiento por altas presiones hidrostáticas (HHP) en la calidad de queso fresco y en las proteínas de suero de queserías

TORRES BELLO, EDWIN FABIÁN 26 March 2017 (has links)
[EN] High Hydrostatic Pressure technology emerged several years ago in response to consumer interest for products having greater organoleptic and nutritional quality than those traditionally processed by heat. The food industry initially improved preservation processes developing continuous heat treatment HTST, UHT and aseptic packaging. However, despite these improvements foodstuffs preserved by heat still have quality losses. Although initially the application of High Hydrostatic Pressure in the field of food was focused towards preservation, with the development of technology and research around new applications raised that make it very interesting for the sector. In this context, the aim of this thesis has been the application of High Hydrostatic Pressure on the preservation of fresh cheese and the revalorization of by-products from cheese factories. For this, the effect of treatments by high hydrostatic pressure (HHP) on pathogenic microorganisms (S. aureus, L. monocytogenes) and spoilage microorganisms (Rhodotorula glutinis, aurantiogriseum Penicillium, Pseudomonas fluorescens) that are present in lactic products is evaluated as well as the effect of various factors (sodium chloride (NaCl), initial treatment temperature) on microbial inactivation. To study this effect peptone water at concentrations of 0; 0.1; 0.5; 0.8% NaCl was used as reference medium and fresh cheese as complex matrix containing 0.5% NaCl. Pressure ranges between 200 and 550 MPa (Mega Pascals) were used with short treatment times (in the order of seconds to several minutes), combined with a moderate initial temperature of 20 to 50 °C.The results of microbial inactivation were fitted to the mathematical model that best described the behavior of inactivation curves, allowing predicting the behavior of the microorganisms being treated by HHP under different environmental factors. Treatments by HHP of R. glutinis and P. aurantiogriseum around 350 - 400 MPa generated more than 5 log10 reductions on the initial contamination. The NaCl concentration present in the reference medium for these two microorganisms was an additional control factor. Regarding the effect of the substrate significant differences between the mean values obtained for the reference medium and the complex matrix (cheese) were observed, fresh cheese showed a lower reduction in the initial inoculated load. Due to the production processes of cheesemaking large amount of residual whey generated is a problem under the environmental point of view. In this thesis the use of residual liquid whey was also studied in conjunction with whey protein isolates (WPI) for the purpose of producing gels with a high biological value through various HHP processes. The various mixtures of whey and different percentages of WPI (5, 7, 11, 15% w/v) processed by HHP resulted in gels with different characteristics. The pH values, color (L * a * b *) vary slightly directly depending on the WPI concentration and the storage time. The hardness values and gumminess were modified depending on the liquid medium and the concentration of WPI. The use of cheese whey to gelation favored water retention, significantly reducing the syneresis under refrigeration. This study shows the potential of HHP as control measure, demonstrating the effectiveness of these treatments to prolong the shelf life of fresh cheeses and as unconventional technique to generate new textures that can have great industrial interest at the same time that revalorize some wastes. / [ES] La tecnología de las Altas Presiones Hidrostáticas (HHP) emergió hace varios años como respuesta al interés de los consumidores por disponer de productos de una mayor calidad organoléptica y nutricional que los tradicionalmente procesados por calor. La industria agroalimentaria inicialmente mejoró sus procesos de conservación por calor desarrollando los tratamientos continuos HTST, UHT y el envasado aséptico. Sin embargo, a pesar de estas mejoras los productos alimenticios conservados por calor siguen presentando pérdidas en su calidad final. Aunque al principio la aplicación de las Altas Presiones Hidrostáticas en el campo de la alimentación se enfocó hacia la conservación, con el desarrollo de la tecnología y la investigación alrededor de ella han surgido nuevas aplicaciones que la hacen muy interesante para el sector. En este contexto, el objetivo de la presente tesis doctoral ha sido la aplicación de las Altas Presiones Hidrostáticas en la conservación de queso fresco y en la revalorización de subproductos de queserías. Para ello, se evalúa el efecto de los tratamientos por Altas Presiones Hidrostáticas (HHP) sobre microorganismos patógenos (Staphylococcus aureus, Listeria monocytogenes) y alteradores (Rhodotorula glutinis, Penicillium aurantiogriseum, Pseudomonas fluorescens) de productos lácteos y el efecto de diversos factores presentes en los alimentos (cloruro sódico (NaCl), temperatura inicial de tratamiento) sobre la inactivación microbiana. Para estudiar este efecto se utilizó como medio de referencia agua peptona a concentraciones de 0; 0,1; 0,5; 0,8% de NaCl y como matriz compleja queso fresco con un contenido de 0,5% de NaCl. Se utilizaron intervalos de presión entre 200 y 550 MPa (Mega Pascales) con tiempos de tratamiento cortos (en el orden de segundos a varios minutos), combinados con una temperatura inicial moderada de 20 a 50 °C. Los resultados de inactivación microbiana se ajustaron al modelo matemático que mejor describía el comportamiento de las curvas de inactivación, lo que permite predecir el comportamiento de los microorganismos frente a las HHP y bajo los diferentes factores. En cuanto a las HHP para R. glutinis y P. aurantiogriseum tratamientos en torno a los 350 - 400 MPa generaron más de 5 reducciones log10 de la carga inicial. La concentración de NaCl presente en el medio de referencia para estos dos microorganismos fue un factor adicional de control. Con respecto al efecto del medio de trabajo se observaron diferencias significativas (p<0,05) entre los valores medios obtenidos para el medio de referencia y la matriz compleja (queso fresco): el queso fresco presentó una menor reducción en la carga inicial inoculada.Debido a los procesos productivos de la fabricación del queso se genera gran cantidad de suero lácteo residual que es un problema bajo el punto de vista medioambiental. En esta tesis también se estudió la utilización del suero lácteo líquido residual en conjunto con aislados proteicos del suero (WPI) con la finalidad de producir geles con un elevado valor biológico mediante diversos procesos de HHP. Las diversas mezclas de suero de queso junto con los porcentajes de 5, 7, 11, 15% p/v de WPI procesadas por HHP dieron lugar a geles con diversas características. Los valores de pH, color (L*a*b*) variaron ligeramente dependiendo directamente tanto de la concentración de WPI como del tiempo de almacenamiento. Los valores de dureza y gomosidad sufrieron modificaciones dependiendo del medio líquido y la concentración de WPI. La utilización de suero de queso para la formación del gel favoreció la retención de agua, reduciendo significativamente la sinéresis en refrigeración.Este estudio muestra el potencial de las HHP como una medida de control, demostrándose la efectividad de estos tratamientos para prolongar la vida útil de los quesos frescos y como técnica no convencional para generar nuevas texturas que pueden tener gran inte / [CAT] La tecnologia de les altes pressions hidrostàtiques va emergir fa diversos anys com a resposta a l'interés dels consumidors per disposar de productes d'una qualitat organolèptica i nutricional major que la dels processats per calor tradicionalment. La indústria agroalimentària inicialment va millorar els seus processos de conservació per calor desenvolupant els tractaments continus HTST, UHT i l'envasat asèptic. No obstant això, malgrat aquestes millores els productes alimentaris conservats per calor continuen presentant pèrdues en la seua qualitat final.Tot i que al principi l'aplicació de les altes pressions hidrostàtiques en el camp de l'alimentació es va enfocar cap a la conservació, amb el desenvolupament de la tecnologia i la investigació al voltant d'ella han sorgit noves aplicacions que la fan molt interessant per al sector. En aquest context, l'objectiu de la present tesi doctoral ha sigut l'aplicació de les altes pressions hidrostàtiques en la conservació del formatge fresc i en la revalorització de subproductes de formatgeries. Per a això, s'avalua l'efecte dels tractaments per altes pressions hidrostàtiques (HHP) sobre microorganismes patògens (Staphylococcus aureus, Listeria monocytogenes) i alteradors (Rhodotorula glutinis, Penicillium aurantiogriseum, Pseudomonas fluorescens) de productes lactis i l'efecte de diversos factors presents als aliments (clorur sòdic (NaCl), temperatura inicial de tractament) sobre la inactivació microbiana. Per a estudiar aquest efecte es va utilitzar com a medi de referència aigua peptona a concentracions de 0; 0,1; 0,5; 0,8% de NaCl i com a matriu complexa formatge fresc amb un contingut de 0,5% de NaCl. Es van utilitzar intervals de pressió entre 200 y 550 MPa (Mega Pascals) amb temps de tractament curts (en l'orde de segons a diversos minuts), combinats amb una temperatura inicial moderada de 20 a 50 °C. Els resultats d'inactivació microbiana es van ajustar al model matemàtic que millor descrivia el comportament de les corbes d'inactivació, el que permet predir el comportament dels microorganismes front a les HHP i baix els diferents factors. En referència a les HHP per a R. glutinis i P. aurantiogriseum tractaments al voltant dels 350 - 400 MPa van generar més de 5 reduccions log10 de la càrrega inicial. La concentració de NaCl present en el medi de referència per a aquestos dos microorganismes va ser un factor addicional de control. Respecte a l'efecte del medi de treball es van observar diferències significatives (p<0,05) entre els valors mitjans obtinguts per al medi de referència i la matriu complexa (formatge fresc): el formatge fresc va presentar una menor reducció en la càrrega inicial inoculada. Degut als processos productius de la fabricació del formatge es genera gran quantitat de sèrum lacti residual que és un problema baix el punt de vista mediambiental. En aquesta tesi també es va estudiar la utilització del sèrum lacti líquid residual en conjunt amb aïllats proteics del sèrum (WPI) amb la finalitat de generar gels amb un elevat valor biològic mitjançant diversos processos de HHP. Les diverses mescles de sèrum de formatge juntament amb els percentatges de 5, 7, 11, 15% p/v de WPI processades per HHP van generar gels amb diverses característiques. Els valors de pH, color (L*a*b*) van variar lleugerament depenent directament tant de la concentració de WPI com del temps d'emmagatzematge. Els valors de duresa i gomositat van sofrir modificacions depenent del medi líquid i la concentració de WPI. La utilització del sèrum de formatge per a la formació del gel va afavorir la retenció d'aigua, reduint significativament la sinèresi en refrigeració.Aquest estudi mostra el potencial de les HHP com a una mesura de control, demostrant-s'hi l'efectivitat d'aquestos tractaments per a prolongar la vida útil dels formatges frescos i com a tècnica no convencional per a generar noves textures que poden tindre gran interés / Torres Bello, EF. (2016). Efecto del tratamiento por altas presiones hidrostáticas (HHP) en la calidad de queso fresco y en las proteínas de suero de queserías [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/72866 / TESIS
64

Receptor mediated catabolism of plasminogen activators

Grimsley, Philip George, Medical Sciences, Faculty of Medicine, UNSW January 2009 (has links)
Humans have two plasminogen activators (PAs), tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), which generate plasmin to breakdown fibrin and other barriers to cell migration. Both PAs are used as pharmaceuticals but their efficacies are limited by their rapid clearance from the circulation, predominantly by parenchymal cells of the liver. At the commencement of the work presented here, the hepatic receptors responsible for mediating the catabolism of the PAs were little understood. tPA degradation by hepatic cell lines was known to depend on the formation of binary complexes with the major PA inhibitor, plasminogen activator inhibitor type-1 (PAI-1). Initial studies presented here established that uPA was catabolised in a fashion similar to tPA by the hepatoma cell line, HepG2. Other laboratories around this time found that the major receptor mediating the binding and endocytosis of the PAs is Low Density Lipoprotein Receptor-related Protein (LRP1). LRP1 is a giant 600 kDa protein that binds a range of structurally and functionally diverse ligands including, activated α2 macroglobulin, apolipoproteins, β amyloid precursor protein, and a number of serpin-enzymes complexes, including PA??PAI-1 complexes. Further studies for the work presented here centred on this receptor. By using radiolabelled binding assays, ligand blots, and Western blots on cultured cells, the major findings are that: (1) basal LRP1 expression on HepG2 is low compared to a clone termed, HepG2a16, but appears to increase in long term culture; (2) a soluble form of LRP1, which retains ligand-binding capacity, is present in human circulation; (3) soluble LRP1 is also present in cerebral spinal fluid where its role in neurological disorders such as Alzheimer??s disease is a developing area of interest; and (4) the release of LRP1 is a mechanism conserved in evolution, possibly as distantly as molluscs. The discovery, identification, and characterisation of soluble LRP1 introduces this protein in the human circulation, and presents a possible further level of regulation for its associated receptor system.
65

Možnosti prodloužení kvality ("čerstvosti") rybího masa a analýza změn při jeho skladování

KLEČACKÝ, David January 2018 (has links)
No description available.
66

Everything you wanted to know about the TPA molecule adsorbed on Au(111)

Svensson, Pamela H.W. January 2020 (has links)
The electronic properties of Triphenylamine (TPA) in gas phase and adsorbed on gold(111) have been simulated with Quantum Espresso using Density Functional Theory (DFT). To better understand how the presence of a gold surface affects sunlight absorption in the system, partial Density Of States (pDOS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) of the system have been calculated. To describe the electronic excitation, three different methods have been used, No Core Hole (NCH), Full Core Hole (FCH) and Half Core Hole (HCH) approximation. The excitation of the TPA molecule was made in the nitrogen (N) atom and in the four different carbon (C) atoms with different electronic environments, C-ipso, C-ortho, C-meta and C-para. When using the HCH method, the absorbing atom must be described by a pseudopotential (PP) which includes half of a hole in the 1s orbital. This PP has been generated and a detailed summary of the process is described. The TPA/gold system relaxes to a position with the central N atom of TPA above an gold (Au) atom in the second layer of the surface and at a distance of 3.66 Angstrom, to the first layer. TPA keeps its symmetry with only small differences in the length of atomic bonds when adsorbed. The most striking result of this study is how the band gap of TPA is affected by the gold layer. From the pDOS we can observe that TPA in gas phase has a clear band gap of 2.2 eV with C-ortho dominating in the valence region and the four carbons dominating in the first unoccupied states. When depositing the molecule on the surface of Au(111), the band gap is essentially gone and a number of states appear between the previous highest occupied and lowest unoccupied molecular orbital in TPA. These new states align in energy with three clusters of states of the gold suggesting an interaction between the molecule and the surface. In the generated NEXAFS of nitrogen and carbon in TPA gas phase, one can observe a small pre-peak before the first unoccupied state. This is reinforced when adsorbing the molecule, which generates a pre-peak of approximately 3 eV in width. The pre-peak is connected to the new peaks seen in pDOS, correlating with experimental results on the same system.
67

Catalysts with Increased Surface Affinity for Chemical Recycling of PET Waste

ABEDSOLTAN, HOSSEIN 07 September 2022 (has links)
No description available.
68

Mecanismes de regulació en l'activitat biològica del factor de transcripció Snail

Domínguez Solà, David 03 April 2003 (has links)
Els factors de transcripció de la família Snail són fonamentals en la "transició epiteli-mesènquima", procés morfogènic essencial en el desenvolupament embrionari i en els fenòmens metastàsics tumorals.En els mamífers l'activitat d'Snail és modulada per dos mecanismes. (i) En el promotor humà es troben regions definides de resposta a factors repressors, predominants en les cèl·lules epitelials, i elements diferenciats de resposta a inductors de la "transició epiteli-mesènquima". (ii) L'activitat d'Snail és condicionada també per la seva localització subcel·lular, modulada per mecanismes no transcripcionals: la fosforilació d'Snail determina si és o no exclós del nucli. Al citosol no pot actuar com a repressor transcripcional però pot interaccionar amb la xarxa microtubular, que estabilitza i en condiciona el dinamisme. Això coincideix amb l'activació de la GTPasa RhoA i la reorientació dels filaments de vimentina, fets associats a l'adquisició de capacitat migratòria. L'efecte com a repressor transcripcional i la modulació del dinamisme microtubular són possiblement esdeveniments coordinats necessaris per al rol biològic d'Snail en mamífers. / Snail family of transcription factors is fundamental to the "epithelial-mesenchymal transition", morphogenic process essential to embryonic development and metastatic phenomena in tumors.Snail's activity is modulated in two ways in mammals. (i) The human promoter harbors definite regions that respond to repressor factors, which prevail in epithelial cells; and differentiated elements that respond to known inducers of the "epithelial-mesenchymal transition". (ii) Snail's activity is also conditioned by its subcellular localization, mechanism not dependent on its transcriptional control: Snail phosphorylation determines whether Snail is excluded or not from the nucleus. When in the cytosol, Snail is unable to act as a transcriptional repressor, but however binds to the microtubular meshwork, which becomes stabilized and whose dynamism is conditioned as a result. This fact coincides with the activation of the RhoA GTPase and reorientation of vimentin filaments, both phenomena being related to the acquisition of cell motility. The transcriptional repressor and the microtubule dynamics effects are probably two coordinated events necessary to Snail's biological role in mammals.

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