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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.
181

Genomic Analysis of Nematode-Environment Interaction

Adhikari, Bishwo 15 July 2010 (has links) (PDF)
The natural environments of organisms present a multitude of biotic and abiotic challenges that require both short-term ecological and long-term evolutionary responses. Though most environmental response studies have focused on effects at the ecosystem, community and organismal levels, the ultimate controls of these responses are located in the genome of the organism. Soil nematodes are highly responsive to, and display a wide variety of responses to changing environmental conditions, making them ideal models for the study of organismal interactions with their environment. In an attempt to examine responses to environmental stress (desiccation and freezing), genomic level analyses of gene expression during anhydrobiosis of the Antarctic nematode Plectus murrayi was undertaken. An EST library representative of the desiccation induced transcripts was established and the transcripts differentially expressed during desiccation stress were identified. The expressed genome of P. murrayi showed that desiccation survival in nematodes involves differential expression of a suite of genes from diverse functional areas, and constitutive expression of a number of stress related genes. My study also revealed that exposure to slow desiccation and freezing plays an important role in the transcription of stress related genes, improves desiccation and freezing survival of nematodes. Deterioration of traits essential for biological control has been recognized in diverse biological control agents including insect pathogenic nematodes. I studied the genetic mechanisms behind such deterioration using expression profiling. My results showed that trait deterioration of insect pathogenic nematode induces substantial overall changes in the nematode transcriptome and exhibits a general pattern of metabolic shift causing massive changes in metabolic and other processes. Finally, through field observations and molecular laboratory experiments the validity of the growth rate hypothesis in natural populations of Antarctic nematodes was tested. My results indicated that elemental stoichiometry influences evolutionary adaptations in gene expression and genome evolution. My study, in addition to providing immediate insight into the mechanisms by which multicellular animals respond to their environment, is transformative in its potential to inform other fundamental ecological and evolutionary questions, such as the evolution of life-history patterns and the relationship between community structure and ecological function in ecosystems.
182

Furnitura multipla di servizi ecosistemici da culture energetiche poliennali / MULTIPLE ECOSYSTEM SERVICES PROVISION FROM PERENNIAL BIOENERGY CROPS / Multiple ecosystem services provision from perennial bioenergy crops

FERRARINI, ANDREA 17 March 2016 (has links)
La sfida nel 21esimo secolo è quella di fornire cibo e energia ad un mondo in continua crescita demografica e allo stesso tempo conservare l’ambiente. In questa tesi uno scenario alternativo di uso del suolo per la produzione di bioenergia è stato testato: le fasce tampone bioenergetiche. Considerate le problematiche ambientali legate al trilemma “cibo-energia-ambiente”, la struttura del Millennium Ecosystem Assessment sui servizi ecosistemici (SE) fornisce l’opportunità di esaminare l’impatto ambientale di questo nuovo scenario bioenergetico. In questa tesi ho mirato a determinare in che misura le colture bioenergetiche poliennali influenzino la fornitura multipla di SE quando coltivate come fasce tampone. Per raggiungere questo obiettivo, ho combinato una revisione sistematica della letteratura sui SE forniti da colture energetiche poliennali (CEP) con una prova sperimentale su fasce tampone bioenergetiche. Applicando una metodologia di attribuzione di punteggi agli impatti sui SE estratti dal materiale bibliografico raccolto, ho mostrato come coltivando le CEP lungo i margini dei campi coltivati esista una grande opportunità per sostenere la fornitura multipla di SE. La coltivazione delle CEP come fasce tampone adiacenti a campi agricoli può migliorare i SE di regolazione del clima, dell’acqua e della biodiversità, sostenere la salute del suolo e fornire biomassa dedicata alla produzione di bioenergia. Al contrario, la conversione di margini di campo di prati stabili ha mostrato un impatto netto negativo sulla fornitura multipla di SE. Tuttavia, due sono i principali svantaggi che sono stati individuati relativamente alla creazione e alla gestione delle fasce tampone bioenergetiche. Primo, diversi sono i fattori sito-specifici di tipo idro-pedologico lungo i margini dei campi che devono essere tenuti in considerazione poiché possono avere un impatto negativo sull’affrancamento delle colture e la loro produttività a medio-lungo termine. Secondo, riguardo la catena di approvvigionamento della biomassa, uno spazio di lavoro limitato per le macchine agricole è stato riconosciuto come principale inconveniente per le fasce tampone bioenergetiche rispetto alle CEP coltivate in pieno campo. Questo limite logistico di natura spaziale può inevitabilmente incrementare i tempi e le operazioni di taglio e raccolta della biomassa e quindi in ultima il consumo di combustili fossili. Grazie ad una prova sperimentale su fasce tampone bioenergetiche condotta in un terreno sabbioso-limoso con falda acquifera poco profonda contaminata da nitrati di origine agricola, si è dimostrato come fasce tampone coltivate con miscanto e salice siano in grado di intercettare e rimuovere i nitrati in falda (>60%) tanto quanto fasce tampone con specie avventizie. CEP come miscanto e salice, grazie ai loro apparati radicali profondi, hanno mostrato essere in grado di promuovere delle relazioni pianta-suolo-microorganismi lungo l’intero profilo del suolo utili ai fini ambientali delle fasce tampone bioenergetiche. Infatti, negli strati più profondi, una maggiore biomassa radicale ha portato le CEP a superare le specie avventizie in termini di rimozione biologica dei nitrati dal suolo e mitigazione potenziale dei gas serra. Inoltre, i risultati relativi alla produzione di biomassa e le asportazioni di N legata alla fase di raccolta hanno confermato ulteriormente come la coltivazione di CEP lungo i corsi d’acqua sia una strategia win-win: produzione di biomassa e protezione dell’ambiente. In conclusione, il potenziale rivelato dalle CEP in termini di fornitura multipla di SE suggerisce che la loro coltivazione, come elementi paesaggistici perenni in posizioni strategiche all'interno di paesaggio agricolo, è un'opzione promettente per promuovere l'intensificazione ecologicamente sostenibile degli agroecosistemi. / The 21st century will challenge agriculture to feed and fuel a growing world while conserving the environment. In this thesis an alternative bioenergy land use scenario to the conversion of marginal land has been tested: the bioenergy buffers. Given the environmental issues related to “food-energy-environment” trilemma, the Millennium Ecosystem Assessment framework on ES provides an opportunity to examine the environmental impacts of this new bioenergy land use scenario. In this thesis I aimed to determine to what extent do the perennial bioenergy crops affect the delivery of multiple ES when cultivated as bioenergy buffers. To reach this aim, I combined a systematic revision of literature on ES provided by perennial bioenergy crops with a field experiment on bioenergy buffers. Applying an impact scoring methodology to the effects on ES extracted from literature, I showed that, cultivating perennial bioenergy crops along field margins of former croplands offer a great opportunity to sustain the provision of multiple ES. The cultivation of perennial bioenergy crops on field margins can improve climate, biodiversity and water regulation services, sustain soil health and provide biomass for energetic purposes. On the contrary, grassland conversion showed a net negative impact on multiple ES provision. Nevertheless, I found two main shortcomings related to bioenergy buffers establishment and management. First, several site-specific factors along field margins must be taken into account, because they can affect crop establishment and buffers long-term productivity. Second, regarding to biomass supply chain, a limited working space for the farm machinery operations has been recognized as the main disadvantages of bioenergy buffers compared to large-scale bioenergy plantations. This spatial logistics constraint may inevitably increase harvest and collection operation times and fossil fuel consumption. Conducting a field experiment with bioenergy buffers in a nitrate-enriched shallow groundwater, I showed that miscanthus and willow buffers are able to efficiently intercept and remove from groundwater the incoming NO3-N as much as buffer strips with spontaneous species. Yet, due to their deep rooting systems, bioenergy buffers promote significant plant-microbial linkages along the soil profile. At deeper soil layers, a higher fine root biomass led perennial bioenergy crops to outperform patches of adventitious vegetation in terms of biological N removal from soil and belowground GHG mitigation potential. The results on biomass production and N removal via harvesting further confirmed that the cultivation of perennial bioenergy crops along watercourses is an effective win-win strategy: biomass production and protection of the environment. In conclusion, the revealed potential of perennial bioenergy crops on multiple ES provision implies that their cultivation as perennial landscape elements in strategic locations within landscape is a promising option to promote the ecological sustainable intensification of agroecosystems.
183

Beiträge zur räumlich aufgelösten Analyse mittels Scanning Laserablation-ICP-Massenspektrometrie unter besonderer Berücksichtigung von Schichtsystemen und Supraleitern

Plotnikov, Alexei 19 September 2004 (has links) (PDF)
Die vorliegende Arbeit stellt die Ergebnisse der methodologischen Entwicklung räumlich aufgelöster Analyse mittels Scanning Laserablation-ICP-Massenspektrometrie dar. Eine neue Behandlung zur Quantifizierung transienter analytischer Signale wurde für die Wiederherstellung von Konzentrationsprofilen vorgeschlagen. Die Anwendung der entwickelten Modelle auf die räumlich aufgelöste Analyse mittels LA-ICP-MS ermöglicht verbesserten Informationsgewinn und lässt dadurch eine höhere räumliche Auflösung erreichen. Die Anwendbarkeit der LA-ICP-MS für die räumlich aufgelöste Bestimmung der Stöchiometrie in supraleitenden Borokarbiden wurde untersucht. Der Einfluss apparativer Größen auf das analytische Signal wurde aufgeklärt, um die Messbedingungen zu optimieren. Zusätzlich wurden Fraktionierungseffekte untersucht, um die Ursache und deren Auswirkung auf die Analyse supraleitender Borokarbiden zu erklären. / This work represents the results of the methodological development of spatially resolved analysis by scanning laser ablation ICP mass spectrometry. A new approach to the quantification of transient analytical signals was proposed to reveal the concentration profile. An application of the developed models on spatially resolved analysis by LA-ICP-MS allows to gain more information from experimental data and hence to achieve better spatial resolution. The applicability of LA-ICP-MS to the spatially resolved determination of the stoichiometry of superconducting borocarbides was investigated. The effect of experimental parameters on analytical signals was elucidated in order to optimize the experimental conditions. In addition, fractionation effects were investigated to identify the causes for fractionation and their influence on the analysis of superconducting borocarbides.
184

Stabilité et vieillissement des études de nickelates base praséodyme comme cathodes pour oxyde solide piles à combustible / Stability and ageing studies of praseodymium-based nickelates as cathodes for Solid Oxide Fuel Cells

Vibhu, Vaibhav 12 February 2016 (has links)
Ce travail de thèse est consacré à l’étude des nickelates La2-xPrxNiO4+δ, comme nouveaux matériauxde cathodes pour piles à combustible haute température, SOFC, et en particulier à la caractérisationde leur stabilité chimique et leur comportement en fonctionnement. En effet, du fait de leurpropriété de conduction mixte ionique et électronique, MIEC, les nickelates de structure typeK2NiF4, Ln2NiO4+δ (Ln = La, Pr, Nd), correspondant au terme n = 1 de la série de Ruddlesden-Popper (An+1MnO(3n+1)), sont des matériaux prometteurs pour des fonctionnements à températureintermédiaire, IT-SOFC (T < 800 °C). Compromis entre la stabilité chimique de La2NiO4+δ et lestrès bonnes performances électrochimiques de Pr2NiO4+δ, les phases La2-xPrxNiO4+δ, ont étésynthétisées et leurs propriétés physico-chimiques, de transport et électrochimiques ont étédéterminées. L’étude approfondie des caractéristiques des électrodes par spectroscopied’impédance en cellules symétriques a été réalisée à courant nul et sous polarisation anodique etcathodique sur des périodes d’un mois. De façon surprenante, même après la dissociation complètede Pr2NiO4+δ en PrNiO3-δ, Pr4Ni3O10+δ et Pr6O11, la résistance de polarisation ne montre pas dechangement significatif. L’étude de PrNiO3-δ et Pr4Ni3O10+δ, comme matériau de cathode pour pilesà combustible, démontre l’excellent comportement de la phase Pr4Ni3O10+δ et ceci en cellulesymétrique (Rp (Pr4Ni3O10+δ) = Rp (Pr2NiO4+δ) = 0.15 Ω.cm² à 600 ° C) et cellule complète (1.6W.cm-2 at 800 °C). / This PhD work is dedicated to stability and ageing studies of Praseodymium based nickelates ascathodes for Solid Oxide Fuel Cells (SOFCs). With this respect Ln2NiO4+δ (Ln=La, Pr or Nd)compounds with the K2NiF4 type structure act as alternative cathode materials for IT-SOFC due totheir mixed ionic and electronic conductivity (i.e. MIEC properties). Pr2NiO4+δ shows excellentelectrochemical properties at intermediate temperature (i.e. low polarization resistance Rp value, Rp= 0.03 Ω.cm² at 700 °C), while La2NiO4+δ exhibits higher chemical stability. So, the properties ofLa2-xPrxNiO4+δ nickelates were investigated with the aim to find best compromise between chemicalstability and electrochemical performances. After synthesis, the physical and chemical properties aswell as their transport and electrochemical properties have been determined. Measurements of thepolarization resistance of symmetrical half-cells have been carried out by impedance spectroscopy.Then, the chemical stability and the electrochemical performance of the materials have been studiedfor duration up to one month. As an interesting point, even after complete dissociation of Pr2NiO4+δinto PrNiO3-δ,Pr4Ni3O10+δ and Pr6O11, the polarization resistance does not show significant change.So finally, two new materials PrNiO3-δ and Pr4Ni3O10+δ were investigated as SOFCs cathodeshowing very promising results for Pr4Ni3O10+δ in symmetrical cell (Rp (Pr4Ni3O10+δ) = Rp(Pr2NiO4+δ) = 0.15 Ω.cm² à 600 ° C) and complete cell (1.6 W.cm-2 at 800 °C).
185

Thiol-ene and Thiol-ene-epoxy Based Polymers for Biomedical Microdevices

Vastesson, Alexander January 2017 (has links)
Within healthcare there is a market pull for biomedical devices that can rapidly perform laboratory processes, such as diagnostic testing, in a hand-held format. For this reason, biomedical devices must become smaller, more sophisticated, and easier to use for a reasonable cost. However, despite the accelerating academic research on biomedical microdevices, and especially plastic-based microfluidic chips, there is still a gap between the inventions in academia and their benefit to society. To bridge this gap there is a need for new materials which both exhibit similar properties as industrial thermoplastics, and that enable rapid prototyping in academia. In this thesis, thiol-ene and thiol-ene-epoxy thermosets are evaluated both in terms of their suitability for rapid prototyping of biomedical microdevices and their potential for industrial manufacturing of “lab-on-chips”. The first part of the thesis focuses on material development of thiol-ene and thiol-ene-epoxy thermosets. Chemical and mechanical properties are studied, as well as in vitro biocompatibility with cells. The second part of the thesis focuses on microfabrication methods for both thermosets. This includes reaction injection molding, photostructuring, and surface modification. It is demonstrated how thiol-ene and thiol-ene-epoxy both provide advantageous thermo-mechanical properties and versatile surface modifications via “thiol-click chemistry”. In the end of the thesis, two applications for both polymer platforms are demonstrated. Firstly, thiol-ene is used for constructing nanoliter well arrays for liquid storage and on-demand electrochemical release. Secondly, thiol-ene-epoxy is used to enhance the biocompatibility of neural probes by tuning their flexibility. It is concluded that both thiol-ene and thiol-ene-epoxy thermosets exhibit several properties that are highly suitable for rapid prototyping as well as for scalable manufacturing of biomedical microdevices. / <p>QC 20171003</p>
186

OSTE Microfluidic Technologies for Cell Encapsulation and Biomolecular Analysis

Zhou, Xiamo January 2017 (has links)
In novel drug delivery system, the encapsulation of therapeutic cells in microparticles has great promises for the treatment of a range of health con- ditions. Therefore, the encapsulation material and technology are of great importance to the validity and efficiency of the advanced medical therapy. Several unsolved challenges in regards to versatile microparticle synthesis ma- terials and methods form the main obstacle for a translation of novel cell therapy concepts from research to clinical practice. Thiol-ene based polymer systems have emerged and gained great popular- ity in material development in general and in biomedical applications specif- ically. The thiol-ene platform is broad and therefore of interest for a variety of applications. At the same time, many aspects of this material platform are largely unexplored, for example material and manufacturing technology developments for microfluidic applications . In this Ph.D. thesis, thiol-ene materials are explored for use in cell encap- sulation. The marriage of these two technology fields breeds the possibility for a novel microfluidic cell encapsulation approach using a novel encapsulation material. To this end, several new manufacturing technologies for thiol-ene and thiol-ene-epoxy droplet microfluidic devices were developed. Moreover, core-shell microparticle synthesis for cell encapsulation based on a novel co- synthesis concept using a thiol-ene based material was developed and inves- tigated. Finally, a thiol-ene-epoxy system was also used for the formation of microwells and microchannels that improve protein analysis on microarrays. The first part of the thesis presents the background and state-of-the-art technologies in regards to cell therapy, microfluidics, and thiol-ene based ma- terials. In the second part of the thesis, a novel manufacturing approach of thiol-ene-epoxy material as well as core-shell particle co-synthesis in micro- fluidics using thiol-ene based material are presented and characterized. The third part of the thesis presents the cell viability studies of encapsulated cells using the novel encapsulation material and method. In the final part of the thesis, two applications of thiol-ene-epoxy gaskets for protein detection mi- croarrays are presented. / Inkapsling av levande celler i mikrokapslar för terapeutiska ändamål är mycket lovande för frmatida behandling av många olika sjukdomar. Emeller- tid är en behandlings effektivitet i hög grad beroende av vilka material som används för inkapsling och vilken teknisk lösning som används för att ska- pa mikrokapslarna. För närvarande återstår det många utmaningar för att omvandla grundforskningresultat till klinisk verklighet, vilken kräver mer än- damålsenliga tillvägagångssätt för att tillverka mikrokapslar i material som är kompatibla med användningsområdena. De senaste åren har tiol-en baserade polymerer har blivit mycket använda för materialutveckling i stort och för biomedicinska tillämpningar i synnerhet. Med tiol-en kemi kan en mycket stor mängd helt olika syntetiska material framställas, vilket gör tiol-ener intressanta för en mängd applikationer. För närvarande är dock mycket inom denna materialklass outforskat, t.ex. inom material och tillverkningmetodik för mikrofluidiktillämpningar. I denna avhandling används tiol-ener för cellinkapsling. Sammanslagning av dessa teknologier möjliggör en ny typ av cellinkapsling med nya materi- alegenskaper. En mängd olika tillverkningssätt där tiol-en eller tiol-en-epoxi används för droplet-mikrofluidiksystem utvecklades. Core-shell mikrokapsel- syntes för cell-inkapsling baserat på en ny metod för samtidig syntes av både core och shell utvecklades och karaktäriserades. Slutligen utvecklades ett tiol- en-epoxi system för enkel integrering med proteinmikroarrayer på objektsglas. I avhandlingens första del presenteras bakgrund och dagens bästa teknolo- gier för terapeutisk cellinkapsling, mikrofluidik och tiol-en baserade material. I avhandlingens andra del presenteras en ny tillverkningsmetod för mikro- strukturerade tiol-en-epoxi artiklar och samtidig syntes av core och shell för mikrokapslar med användande av mikrofluidik. I den tredje delen presenteras cellöverlevandsstudier för de celler som inkapslats med de nya materialen och de nyutvecklade metoderna. I den avslutande delen beskrivs två specifika fall där tiol-en-epoxi komponenter används för proteindetektion och mikroarrayer. / <p>QC 20171122</p>
187

A unique serpin P1′ glutamate and a conserved β-sheet C arginine are key residues for activity, protease recognition and stability of serpinA12 (vaspin)

Ulbricht, David, Pippel, Jan, Schultz, Stephan, Meier, René, Sträter, Norbert, Heiker, John T. 06 March 2019 (has links)
SerpinA12 (vaspin) is thought to be mainly expressed in adipose tissue and has multiple beneficial effects on metabolic, inflammatory and atherogenic processes related to obesity. KLK7 (kallikrein 7) is the only known protease target of vaspin to date and is inhibited with a moderate inhibition rate. In the crystal structure, the cleavage site (P1-P1′) of the vaspin reactive centre loop is fairly rigid compared with the flexible residues before P2, possibly supported by an ionic interaction of P1′ glutamate (Glu379) with an arginine residue (Arg302) of the β-sheet C. A P1′ glutamate seems highly unusual and unfavourable for the protease KLK7. We characterized vaspin mutants to investigate the roles of these two residues in protease inhibition and recognition by vaspin. Reactive centre loop mutations changing the P1′ residue or altering the reactive centre loop conformation significantly increased inhibition parameters, whereas removal of the positive charge within β-sheet C impeded the serpin–protease interaction. Arg302 is a crucial contact to enable vaspin recognition by KLK7 and it supports moderate inhibition of the serpin despite the presence of the detrimental P1′ Glu379, which clearly represents a major limiting factor for vaspin-inhibitory activity. We also show that the vaspin-inhibition rate for KLK7 can be modestly increased by heparin and demonstrate that vaspin is a heparin-binding serpin. Noteworthily, we observed vaspin as a remarkably thermostable serpin and found that Glu379 and Arg302 influence heat-induced polymerization. These structural and functional results reveal the mechanistic basis of how reactive centre loop sequence and exosite interaction in vaspin enable KLK7 recognition and regulate protease inhibition as well as stability of this adipose tissue-derived serpin.
188

Beiträge zur räumlich aufgelösten Analyse mittels Scanning Laserablation-ICP-Massenspektrometrie unter besonderer Berücksichtigung von Schichtsystemen und Supraleitern

Plotnikov, Alexei 03 December 2003 (has links)
Die vorliegende Arbeit stellt die Ergebnisse der methodologischen Entwicklung räumlich aufgelöster Analyse mittels Scanning Laserablation-ICP-Massenspektrometrie dar. Eine neue Behandlung zur Quantifizierung transienter analytischer Signale wurde für die Wiederherstellung von Konzentrationsprofilen vorgeschlagen. Die Anwendung der entwickelten Modelle auf die räumlich aufgelöste Analyse mittels LA-ICP-MS ermöglicht verbesserten Informationsgewinn und lässt dadurch eine höhere räumliche Auflösung erreichen. Die Anwendbarkeit der LA-ICP-MS für die räumlich aufgelöste Bestimmung der Stöchiometrie in supraleitenden Borokarbiden wurde untersucht. Der Einfluss apparativer Größen auf das analytische Signal wurde aufgeklärt, um die Messbedingungen zu optimieren. Zusätzlich wurden Fraktionierungseffekte untersucht, um die Ursache und deren Auswirkung auf die Analyse supraleitender Borokarbiden zu erklären. / This work represents the results of the methodological development of spatially resolved analysis by scanning laser ablation ICP mass spectrometry. A new approach to the quantification of transient analytical signals was proposed to reveal the concentration profile. An application of the developed models on spatially resolved analysis by LA-ICP-MS allows to gain more information from experimental data and hence to achieve better spatial resolution. The applicability of LA-ICP-MS to the spatially resolved determination of the stoichiometry of superconducting borocarbides was investigated. The effect of experimental parameters on analytical signals was elucidated in order to optimize the experimental conditions. In addition, fractionation effects were investigated to identify the causes for fractionation and their influence on the analysis of superconducting borocarbides.

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