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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.
411

A suplementação crônica com ácido linoléico conjugado promove redução da massa adiposa e compromete a sensibilidade à insulina no tecido adiposo branco periepididimal. / Chronic supplementation with conjugated linoleic acid reduces adipose mass and mpairs insulin sensitivity in periepidydimal white adipose tissue.

Tarcila Beatriz Ferraz de Campos 23 April 2008 (has links)
O ácido linoléico conjugado (CLA) é um ácido graxo poliinsaturado, encontrado nos produtos da alimentação. Estudos indicam que o CLA possui ações contra câncer, aterogênese e DM 2 e obesidade. O presente trabalho avaliou os efeitos da suplementação crônica com CLA em ratos Wistar machos e teve como objetivo investigar o desenvolvimento corporal e o perfil metabólico dos animais e dos adipócitos isolados do tecido adiposo branco periepididimal. Após quatro semanas de suplementação os animais apresentaram redução no ritmo de ganho de peso, acompanhado de redução da ingestão alimentar, redução da massa adiposa e do volume celular dos adipócitos. A menor incorporação dos substratos acetato e glicose em lipídeos, o aumento lipólise e diminuição da expressão do PPAR?, também contribuíram para menor adiposidade encontrada. A redução de massa adiposa foi acompanhada por resistência à insulina, elevados níveis de citocinas inflamatórias e desenvolvimento de esteatose hepática. Esses fatores estão relacionados com o desenvolvimento de síndrome lipodistrófica em animais. Portanto, a efetividade do CLA em reduzir massa adiposa foi comprovada no presente estudo, mas os efeitos devem ser considerados. / Conjugated linoleic acid (CLA) is a natural polyunsatured fatty acid found in many dietary sources. Animal studies demonstrated that CLA has properties against cancer, atherogenesis, diabetes and obesity. This work evaluated the effects with chronic CLA supplementation in young adults Wistar male rats for four weeks, aiming to investigate the possible changes in corporal development and metabolic profile as well as the effects in isolated adipocytes of periepidydimal white adipose tissue of these supplemented animals. We observed a reduction of the rhythym of body weight gain, followed by diminished food intake, regression of adipose mass, and also a reduction of adipocyte volume. The findings of low incorporation of acetate and glucose substrates into lipids, elevation on the lipolytic response and reduction of PPAR-gamma gene expression, also contributed to the lower adiposity. This reduction in adipose mass was followed by insulin resistance, high levels of inflammatory citokines and the development of hepatic steatosis, features related to the development of lipodystrophic syndrome. Therefore, this study demonstrated the CLA effect on reduction of adipose mass, although adverse effects associated with CLA chronic supplementation must be considered.
412

MODELING THE CONDENSED-PHASE BEHAVIOR OF Π-CONJUGATED POLYMERS

Mask, Walker 01 January 2019 (has links)
It is well established that the morphology and physical properties of an organic semiconducting (OSC) material regulate its electronic properties. However, structure-function relationships remain difficult to describe in polymer-based OSC, which are of particular interest due to their robust mechanical properties. If relationships among the molecular and bulk levels of structure can be found, they can aid in the design of improved materials. To explore and detail important structure-function relationships in polymer-based OSC, this work employs molecular dynamics (MD) simulations to study various π-conjugated polymers in different environments. Two independent investigations are discussed in this work. One investigation examines how the purposeful disruption of the π-conjugated backbone to increase the chain flexibility impacts the chain structure and packing in the condensed phase. This is done by adding a conjugation break spacer (CBS) unit of one to ten carbons in length into the monomer structure of diketopyrrolopyrrole-based polymers. It is found that trends in the folding and glass structure follow the increase and the parity (odd versus even) of the CBS length. The second investigation analyzes a variety of polymers and small molecule acceptor (SMA) blends to observe the effects of changing the shape of either component and the physical properties of the material, as well as the structure of the polymer chains. It is found that the conjugated core, the side chains, and the planarity or sphericity each influence the density and diffusion of the materials made.
413

Peptide and Protein Supramolecular Assemblies Studied by Solid-State NMR Spectroscopy

Qi, Zhe 07 September 2017 (has links)
No description available.
414

Activity and mRNA abundance of enzymes for fatty acid synthesis and desaturation in mammary cell cultures

Jayan, Geetha C. Jr. 01 September 1998 (has links)
The effect of exogenous unsaturated fatty acids on cellular fatty acid biosynthesis in mammary cells was examined. Under normal situations, even though the diet of a dairy cow contains considerable amounts of unsaturated fatty acids, viz. oleic acid (18:1) and linoleic acid (18:2), the major 18-carbon fatty acid that enters the circulation post-ruminally for delivery to the mammary gland is saturated fatty acid, viz. stearic acid (18:0). This is due to extensive ruminal biohydrogenation of unsaturated fatty acids. Studies have indicated that saturated fatty acids such as 18:0 are enhancers and that certain unsaturated fatty acids are inhibitors of de novo fatty acid synthesis in tissues such as the liver and adipose tissue. The present study investigated the effect of cis and trans isomers of 18:1 and 18:2 on de novo fatty acid synthesis and desaturation in mouse and bovine mammary epithelial cell cultures, and compared it with the effect caused by 18:0. In the first experiment 12.5, 25, 50 or 100 micromoles stearic acid (SA), oleic acid (OA), elaidic acid (EA), trans-vaccenic acid (TVA), linoleic acid (LA) or conjugated linoleic acid (CLA) were supplemented in the media of mouse mammary epithelial (MME) cells that were grown to confluence in Dulbecco's modified Eagle's medium (DMEM). As indicated by cellular palmitic acid (16:0) content and fatty acid synthetase (FAS) activity, when compared with SA all unsaturated fatty acid treatments inhibited de novo fatty acid synthesis in MME cells. In addition, OA at all concentrations and LA and CLA at 50 and 100 micromoles inhibited cellular stearoyl-CoA desaturase (SCD) activity and mRNA abundance. However, EA and TVA, when compared with SA, enhanced SCD activity and mRNA abundance at 12.5 and 25 micromoles. In the second experiment 25, 50 or 100 micromoles SA, OA, TVA, LA or CLA were supplemented in the media of bovine mammary epithelial cells that were grown to confluence in DMEM. As indicated by cellular 16:0 content, acetyl-CoA carboxylase (ACC) activity and FAS activity, treatment with the unsaturated fatty acids inhibited de novo fatty acid synthesis at all concentrations, when compared with SA. Unsaturated fatty acid treatments also reduced the abundance of ACC and FAS mRNA in the cells. When compared with SA at all treatment-concentrations, OA and LA inhibited whereas TVA and CLA enhanced cellular SCD activity and mRNA abundance in the bovine cells. In both cell types, CLA and TVA appeared to be the most potent inhibitors of saturated fatty acid biosynthesis. / Ph. D.
415

Conjugated polymers for the elaboration of optical and ohmic sensors for water monitoring / Polymères conjugués pour l'élaboration de capteurs optiques et résistifs pour l'analyse de l'eau

Wang, Xinyang 11 October 2018 (has links)
Le but de mon projet est de développer des capteurs moins chers qui sont capables de détecter rapidement les présences des ions métalliques dans l'eau. Deux types de capteurs sont élaborés dans la cadre de ce projet: des capteurs optiques sont développés à partir de polymères conjugués (PCs) avec des ligands spécifiques car ils peuvent amplifier le signal de fluorescence et faciliter la migration des électrons, améliorant ainsi la sensibilité des capteurs1 ; et des capteurs ohmiques qui permettent des mesures in-situ.Concernant les capteurs optiques, deux séries de polymères conjugués avec trois ligands différents sont synthétisés pour étudier l’influence des groupes ligands ainsi les structures des squelettes des polymères sur leur capacité à reconnaître des ions métalliques (Figure 1). Les titrations photoluminescences de ces polymères avec dix ions métalliques (Al3+, Ca2+, Cd2+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Ni2+, et Zn2+) ont montré que le polymère nommé P1 est sensible à Cu2+ et Ni2+, et le polymère P6 émet une couleur orange en présence des ions Cd2+ et Zn2+ sous lumière UV (Figure 2). Ces faits permettent d’utiliser les polymères comme capteurs optiques pour ces ions à partir des quantités en ppb (µg/L). Nous avons aussi montré la possibilité d’utiliser ces polymères sous forme solide ce qui permet de recycler ces capteurs en films (Figure 3).Les capteurs ohmiques sont développés en combinant des PCs avec des nanotubes de carbone (NTC) comme éléments de détection2. Une telle combinaison devrait apporter à la fois une sélectivité par une fonctionnalisation chimique adéquate des PC3, et une sensibilité grâce aux propriétés électriques des NTC. En effet, dans les nanohybrides PC/NTC, les squelettes conjugués des polymères sont physisorbés sur les parois du NTC par des interactions d'empilement (Figure 4 - a). La modification électronique induite par l'interaction entre les PC et les analytes devrait être transférée aux NTC, qui agissent comme des transducteurs dans les capteurs, en modifiant leur conductivité. Les polymères synthétisés précédemment sont fonctionnalisés sur les parois de NTC afin de formuler des nanohybrides PCs/NTC pour l’élaboration des capteurs ohmiques. Les nanohybrides PCs/NTC sont caractérisés par des méthodes expérimentales (microscopie électronique en transmission, Raman, etc.) et numérique (simulation, Figure 4 - b) pour confirmer l’interaction entre PCs et NTC. Les nanohybrides sont ensuite déposés sous forme de films sur des puces avec les électrodes (Figure 4 - c) qui servent d’éléments résistif dans les dispositifs. La réponse des dispositifs aux concentrations métalliques est mesurée et étudiée. / Different pollutants can be found in water, inorganic material (chloride, chlorine, heavy metal ions…) and organic material (trace of medicament…). Among them, heavy metal ions are of among the most toxic for human and the environment. 
Analysis of water contaminants that are toxic for human being and aquatic life is of primary importance. Especially, the measurements of the quality of drinking water delivered in private dwelling is a significant public health concern. A family of undesired contaminants is heavy metals. An elevated concentration of metal ions in water is mostly due to an intensive human activity (industry, farming, and housing). In small quantities, certain heavy metals (e.g., iron, copper, manganese, and zinc) are nutritionally essential for a healthy life. However, heavy metals show a great trend to form complexes, especially with ligands of biological matter containing nitrogen, sulfur, and oxygen. As a result, changes in the molecular structure of proteins, breaking of hydrogen bonds, or inhibition of enzymes can occur[1]. These interactions, among others, may explain the toxicological and carcinogenic effects of heavy metals. These ions can cause damages to many organs and are responsible of diseases, including Parkinson’s and Alzheimer’s diseases[2-6]{Liu, 2015 #101;Liu, 2015 #101;Kim, 2012 #102;Kim, 2012 #102;Liu, 2015 #101;Kim, 2012 #102;Liu, 2015 #101;Kim, 2012 #102;Liu, 2015 #101}. Respiratory and cardiac problems can be caused by nickel ingestion[7], and accumulation of the Ni2+ ion in the body leads to oxidative stress[8]; Ni2+ and Cu2+ are also noxious to teeth and bones. These negative effects result from the formation of coordination complexes between the metal ions and biological matter.Heavy metals are not biodegradable and therefore they remain in ecological systems and in the food chain indefinitely, exposing top-level predators to very high levels of pollution.Different methods are used to determine their quantity concentration in aqueous phase such as anodic stripping voltammetry (ASV) [4, 6], solid phase extraction combined with inductively coupled plasma optical emission spectrometry ICP-OES[4, 6] and cold-vapor atomic absorption spectroscopy (AAS) method[9]. These methods are well established, but are costly, time consuming, lack portability, and rely on trained personnel because of their complexity[10].Therefore, cheap, portable and real-time response real-time sensors for the determination of heavy metals in aqueous solutions are needed, particularly in sensitive environments, such as drinking water and industrial wastewater effluents. Here we design and elaborate The aim of the project is to develop these kinds of sensors to satisfy the current need. Two kinds of sensors have been elaborated in the project: the first one is optical sensors based on functionalized conjugated polymers (CPs). The second one is a communicating resistive sensors based on conjugated polymers (CPs)/carbon nanotubes (CNTs) nanohybride for the quick detection of pollutants in aqueous water. To our knowledge, no this kind of resistive of sensors has been developed yet. The start of the project focuses onWe start the project for the detection of metal ions, however, it can later be extended to other kinds of pollutants (such as nitrate, chloride, even drugs) using different polymers with the same working mechanism.
416

Luminescent hybrid materials for LED lighting / Matériaux hybrides luminescents pour l'éclairage à LED

Lin, Qiqiao 04 September 2019 (has links)
Cette thèse visait à concevoir et à synthétiser des matériaux hybrides organiques-inorganiques à luminescence contrôlée et à les étudier en tant que luminophores pour l'éclairage à LED. L'objectif final était d'obtenir une source de lumière blanche. En effet, les LED blanches commerciales sont constituées d'un dispositif émetteur bleu recouvert d'un luminophore jaune. La combinaison de ces deux couleurs produit une lumière blanche. Cependant, cette lumière n'est pas de bonne qualité car il lui manque une composante rouge. Cela entraîne un mauvais rendu des couleurs des objets éclairés par ces sources de lumière. Dans notre travail, des polymères conjugués de différentes couleurs d'émission ont été obtenus avec succès. En particulier, plusieurs émetteurs de blanc ont pu être isolés.Dans cette thèse, non seulement les procédures de synthèse et les caractérisations chimiques sont présentées en détail, mais également les études des propriétés photophysiques des polymères, en solution et à l'état solide. Des études à l'état solide ont été effectuées sur les polymères et sur les polymères dispersés dans une matrice polymère. Ces études ont permis d'identifier les facteurs limitants quant aux utilisations pratiques de ces matériaux. Des solutions ont été proposées pour améliorer les performances d’émission et de stabilité des matériaux. De plus, ces travaux ont permis d'introduire la 2,2’-bipyrimidine comme nouvelle unité constitutrice pour le développement de polymères conjugués. / This thesis aimed at designing and synthesizing organic-inorganic hybrid materials with controlled luminescence and at investigating them as phosphors for LED lighting. The final goal was to obtain a white source of light. Indeed, commercial white LEDs are made up of a blue emitting device covered with a yellow phosphor. Combining these two colors yields white light. However, this light is not of good quality as it lacks some red component. This results in a bad rendering of the colors of objects illuminated by these sources of light. In our work, conjugated polymers with different emission colors have successfully been obtained. In particular, several single white emitters have been isolated.In this PhD thesis, not only the synthetic procedures and chemical characterizations are presented in detail, but also the studies of the photophysical properties of the polymers, either in solution or in the solid state. Solid state studies were performed on the bulk polymers and on the polymers dispersed into a polymeric matrix. These studies have lead to identify the limiting factors that could hamper the use of the materials. Solutions have been proposed to improve the materials performance and stability. Furthermore, 2,2’-bipyrimidine has been introduced as a new synthon for designing and developing conjugated polymers.
417

Development of Functional Organic Materials with an Intramolecular B-N Coordination Bond as a Key Scaffold / 分子内B-N配位結合を鍵骨格にもつ機能性有機材料の開発

Shimogawa, Hiroyuki 23 March 2017 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20394号 / 工博第4331号 / 新制||工||1671(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 村田 靖次郎, 教授 辻 康之, 教授 中村 正治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
418

Polyaniline-derivatives based on poly (heterocyclic diphenylamine) with improved electrochemical stability and processability

Almtiri, Mohammed Noifa 09 August 2022 (has links) (PDF)
Today, smart innovation has become an essential part of human life; thus, contemporary technologies are always looking for intelligent, responsive, and efficient materials to satisfy these demands. Consequently, synthetic "metals" or, more precisely, intrinsically conducting polymers (CPs) have begun to find a place as valuable and practical materials for a new generation of devices. Amongst all intrinsic conducting polymers, polyaniline (PANI) has attracted significant attention due to its outstanding air and moisture stability, simple preparation technique, and high electrical conductivity (chapter I). Chapter II represents the synthesis of a new PANI derivative that contains a phenoxazine unit co-polymerized with p-phenylenediamine derivatives by the Buchwald/Hartwig reaction. These polymers are soluble in many common organic solvents, which permit their full characterization and allow for solution processing. The polymers' optical properties mimicked PANI; however, they were more electrochemically stable and soluble compared to PANI. In addition, the analogous PANI emeraldine base forms a large bathochromic shift in the absorption spectra upon acidic doping to form analogues of PANI emeraldine salts. Chapter III describes our strategy to prepare economical, electrochemically stable, and processable PANI derivatives from carbazole and 1,4-aryldiamines for supercapacitor device. The polymers exhibit good solubility in various organic solvents, enabling a scalable spray-coating method to fabricate electrodes. The polymers were used to fabricate electrodes for supercapacitor devices and exhibit a maximum area capacitance of 64.8 mF cm−2 and specific capacitance of 319 F g−1 at a current density of 0.2 mA cm−2. Chapter IV MXene has been recently widely applied to energy storage devices due to its metallic conductivity and excellent electrochemical Activities. However, MXene sheets suffer from the restacking phenomena during cycling. Restacking restricts the ion diffusions and storage capability between the MXene layers, which lowers the accessible surface area. The restacking phenomena of MXene sheets was shown to be eliminated by the deposition of conductive polymers on the surface of MXene sheets.
419

Conjugated Linoleic Acids Alter Body Composition Differently According to Physiological Age in Moulard Ducks

Fesler, Jeff, Peterson, Daniel 01 December 2013 (has links) (PDF)
Conjugated linoleic acids (CLA) have been shown to have remarkable yet inconsistent metabolic effects in mice, rats, hamsters, chickens, cattle, and humans. In particular, effects on lipogenesis vary with tissue, physiological state and specie. In this study we tested the hypothesis that CLA would differentially affect ducks of the same genetic background but of differing age. Growing (7 wk) and maintenance (11 wk) Moulard ducks were grouped by age and fed a standard diet supplemented with either 5% soybean oil (control) or 5% CLA isomer mixture. Animals were harvested after 3 weeks or 6 weeks for assessment of body composition including adipose, liver, viscera, and empty carcass weight. Serum nonesterified fatty acid (NEFA) and glucose concentrations were evaluated, and gene targets were cloned from the duck to use in quantifying mRNA abundance for genes involved in lipogenesis (fatty acid synthase, FAS; acetyl-CoA carboxylase, ACC) and lipid oxidation (carnitine palmitoyl transferase-1, CPT-1) in liver tissue from maintenance animals. After 3 weeks, the growing CLA group exhibited a 24% decrease in dissectible adipose tissue (P < 0.05) while maintenance animals showed no significant diet effect. After 6 weeks, the growing CLA group exhibited a 20% increase in liver mass compared to the control (P < 0.05), but no diet effect on adipose tissue. Maintenance animals receiving dietary CLA had a 42% decrease in adipose tissue mass after 6 weeks, increased serum NEFA, ACC and CPT-1 mRNA after 3 and 6 weeks (P < 0.05), and increased FAS mRNA after 3 weeks of treatment (P < 0.05). These data indicate that CLA have potent effects on lipid metabolism in ducks, but that these effects differ dependent on physiological age.
420

ORGANIC IONO-OPTOELECTRONICS

Ke Chen (17382961) 13 November 2023 (has links)
<p dir="ltr">Conjugated polymers are organic macromolecules that are characterized by a backbone chain of alternating double- and single-bonds. This alternating pattern results in delocalized π electronic systems, contributing to electronic conduction. In the solid state, conjugated polymers exhibit weak intermolecular interactions, rendering them soft nature in comparison to many of their inorganic counterparts, such as silicon, which consist of ‘hard' three-dimensional networks of rigid covalent bonds. In electrolyte, this weak intermolecular interaction creates free pathways for ion penetration and facilitates mixed ionic-electronic coupling. The ionic-electronic coupling of conjugated polymers impacts nearly all their properties, including light absorption, electronic conductivity, mechanical strength, etc.</p><p dir="ltr">Organic iono-optoelectronics represent a class of devices where the ionic-electronic coupling in conjugated polymers can be synergistically or independently controlled by light irradiation and electrical voltage, enabling multimode electronic and optical functionalities. This dissertation explores two types of organic iono-optoelectronic devices: electrochromic devices and artificial eyes. In electrochromic devices, the ionic-electronic coupling is dynamically modulated by electrical voltage, which induces optical changes of conjugated polymers for applications in information visualization, thermal management, camouflage, etc. Conversely, artificial eyes utilize optical stimulation to tailor the electronic-ionic coupling, with electrical potential changes serving as readout. This paradigm shift opens the door to the development of light-driven biomedical electronics and intelligent visual systems. In the development of electrochromic devices, we introduce two strategies that expand the color palette and enhance the optical control of electrochromic devices, promoting their potential use in display and camouflage. In the development of artificial eye development, we introduce an electrochemical transistor device with integrated functions of light perception, memorization, and recognition by leveraging photon-modulated ion-electronic coupling. This device demonstrates great potential for intelligent visual systems and promises future optoelectronic neural interfaces.</p>

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