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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.
31

Non-aqueous polyvanadate chemistry

Bakri, Ridla January 1998 (has links)
No description available.
32

Pseudo-dynamic combinatorial chemistry

Soriano Del Amo, David January 2009 (has links)
Pseudo-dynamic combinatorial chemistry (pDCC) combines the synthesis, screening and destruction of combinatorial libraries to kinetically resolve inhibitors based on their affinity for a target. In our proof-of-principle studies, a library of dipeptides was formed in the presence of a target, carbonic anhydrase (CA), and a destruction mechanism, a protease. Since the target and the protease were separated by a dialysis membrane, only the proportion of dipeptides that was not bound to the target was available for destruction and therefore, the rate of hydrolysis of the pseudo-dynamic combinatorial library (pDCL) could be correlated to the librarie's relative affinity for the target. The first set of proof-of-principle pDCC experiments were found to be flawed. Rather than reflecting the binding affinity of the library for the target, the final product distribution reflected the protease's substrate specificity. The main problems with these pDCLs were insufficient and imbalanced rate of destruction of the peptides in the absence of the target, pH drift, and insufficient permeability across 1000 MWCO cellulose ester membranes. A dipeptide amide based pDCL that was efficiently cleaved by thermolysin was designed. The new pDCL could be used in pH 7.5 75 mM HEPES, 16.6 mM CaCl2 buffer, provided that the chambers were limited by 3500 MWCO membranes. A 4th generation pDCC experiment that evolved reflecting the library's affinity for the target was performed. In order to study pDCC behavior a simplified pDCC mimic (pDCCm) was designed. In pDCCm, synthesis was replaced by a static library of compounds and destruction by dilution. The design of a pDCCm based kinetic model led to a / La chimie combinatoire pseudo dynamique (pDCC) combine la synthèse, le criblage et la destruction de libraires combinatoires afin de sélectionner cinétiquement des inhibiteurs sur la base de leur affinité pour une cible. Nos études préliminaires ont été basées sur une librairie de dipeptides formés en présence de l'anhydrase carbonique (CA) comme cible et détruits grâce à une protéase. Étant donné que la cible et la protéase étaient séparées par une membrane de dialyse, seuls les dipeptides non complexés avec la cible étaient susceptibles d'être détruits. Ainsi, la vitesse d'hydrolyse des membres de la librairie combinatoire pseudo-dynamique (pDCL) peut correspondre aux affinités relatives des molécules pour la cible. Les premières expériences prototypes de pDCC étaient défectueuses. Plutôt que de refléter l'affinité des membres de la librairie pour la cible, la distribution finale des produits reflétait la préférence de la protéase pour les substrats. Les principaux problèmes de ces pDCL étaient: une vitesse de destruction des peptides insuffisante et inégale en l'absence de la cible, une déviation progressive du pH et une perméabilité insuffisance au travers les membranes d'ester de cellulose 1000 MWCO. Une pDCL basée sur des amides dipeptidiques, aptes à être efficacement clivés par thermolysine a été élaborée, et utilisée avec succès. Afin d'étudier les pDCC, une expérience modèle simplifiée (pDCCm) a été créée. Dans ce modèle, la synthèse a été remplacée par une librairie statique de molécules et la destruction par une dilution. Le design d'un modèle cinétique basé sur la pDCCm a mené à la cr
33

THE CHEMISTRY OF N-NITROSOKETIMINES

THOMAN, CHARLES JAMES 01 January 1966 (has links)
Abstract not available
34

Parametri emato-biochimici e contaminanti ambientali in Tartarughe e Chirotteri / Blood chemistry and envirnomental contaminants in Tortoise and Bats

Cannavacciuolo, Annunziata <1982> 12 July 2013 (has links)
La biochimica clinica dei rettili e dei cheloni in particolare, non ha ottenuto al momento lo stesso livello di attenzione rivolto ai mammiferi. Con il presente lavoro viene proposta la valutazione dei più importanti parametri ematologici e biochimici in campioni di sangue di Testudo hermanni al fine di facilitare l'interpretazione dei dati di laboratorio e la diagnosi di eventuali patologie. A questo scopo, sono stati calcolati gli intervalli di riferimento di questi parametri in individui clinicamente sani e sono state analizzate le influenze di fattori ambientali e fisiologici. Sono state inoltre determinate le concentrazioni di alcuni importanti elementi chimici sia essenziali che non essenziali. Su campioni di chirottero del genere Tadarida teniotis sono state determinate le concentrazioni di PCB DL, PCB NDL, PCDD/F, PFAS e di elementi chimici essenziali e non, al fine di valutare: il possibile livello di contaminazione in relazione alla specie e all’habitat, la prevalenza e/o il rapporto delle classi di composti nel caso di una possibile contaminazione, la eventuale fonte di contaminazione. A quanto ci risulta, il nostro lavoro rappresenta il primo tentativo di analizzare su vasta scala le concentrazioni di questi inquinanti in una popolazione di pipistrelli residenti in un’area urbana. Tra i vari contaminanti esaminanti in questo studio, il Pb e le diossine possono costituire un serio problema per Tadarida teniotis. / Hermann’s tortoise, Testudo hermanni, is currently on the IUCN red list of endangered species. Reptile medicine uses laboratory analyses to evaluate health status, but data on hematology, blood biochemistry and protein electrophoresis are limited in tortoises.The purposes of this study were to establish the most important hematological and biochemical parameters for health assessment in Hermann’s tortoises, calculate the reference intervals and evaluate the impact of environmental and physiological factors.The reference intervals defined in the present study can be considered a useful tool for clinical pathologists and researchers working in tortoise medicine and conservation. In Europe bat populations are gradually declining due to environmental pollution; in this thesis we have studied the concentrations of many contaminants including essential and non essential trace elements, dioxins, PCB DL and NDL and PFAS in tissues of juveniles Tadarida teniotis. The high concentrations of Pb and dioxin determined are indicative of acute evnironmental exposure.
35

Chemistry /

Sato, Hiroki. January 2008 (has links)
Thesis (M.F.A.)--Rochester Institute of Technology, 2008. / Typescript.
36

Chemické a biologické aspekty vůní a jejich zařazení do výuky chemie / Chemistry and Biology of Smell Components in the A- Level Chemistry Curriculum

Jičínská, Lucie January 2009 (has links)
No description available.
37

Chemické a biologické aspekty chutí a jejich zařazení do výuky chemie / Chemistry and Biology of Taste Components in the A- Level Chemistry Curriculum

Křivská, Štěpánka January 2009 (has links)
No description available.
38

Ocean chemistry and the evolution of multicellularity

Hammarlund, Emma U. January 2012 (has links)
Oxygen has been assumed to be a vital trigger for the evolution of multicellular life forms on Earth, partly based on its power to promote substantial energy flux in cell respiration and partly as biosynthesis of compounds like collagen require oxygen. However, the co-evolution of large life and the Earth’s chemical environment is not well understood at present, and there is particular disagreement in the field about whether the Cambrian explosion of animal life forms was a chemical or biological event. Here, I discuss the evolution of multicellularity, divided in simple or complex forms, in light of the evolution of ocean water column chemistry in both the Proterozoic and the early Paleozoic. Even if the appearance of animals is confined to the Ediacaran, other fossil evidence of complex multicellularity can be argued to occur in the Paleo-, Meso- and Neoproterozic. These finds are, if anything, reason enough to keep searching for early experiments in complex multicellularity. In this search, we may have to expand our toolbox by looking at e.g. trace element aggregations and the isotopic composition of key elements.  Research over the last couple of years have accentuated that much of the interval between the Ediacaran and the Devonian was dramatic with transitional ocean chemistry at the same time that large forms of animal life experienced dynamic radiation and ecological expansion. Results presented here describe some aspects of this time, including geochemistry from Chengjiang and a mechanism for preserving non-mineralized Cambrian animals that was partly dependent on specific ocean chemistry. Also, geochemical proxies using iron and molybdenum are used to infer a Paleozoic atmosphere with less than 50% of present levels of oxygen. The possibility that the subsequent rise is due to terrestrial plants and linked to the appearance of large predatory fish is discussed. Finally, the first mass extinction in the end-Ordovician is linked to low oxygen concentrations in the water column. It appears that more than oxygen was critical to allow the radiation of large life forms on Earth, but that chemistry and tectonic activity were intimately intertwined to biology, in a dance of permitting and being determined by certain aspects of ecology. / Under lång tid har vi sett atmosfärens syrehalt som avgörande för att stora livsformer skulle börja utvecklas på jorden, delvis eftersom syre är ett energirikt bränsle men också för att det krävs vid sammansättningen av vissa ämnen som djur behöver, till exempel proteinet kollagen. Men, i själva verket, har vi inte lyckats reda ut detaljerna om hur utvecklingen av tidigt, stort liv och miljö satt samman, och om den kambriska explosionen framförallt var en biologisk eller kemiskt händelse. I den här avhandlingen diskuterar jag hur utvecklingen av flercellighet, då uppdelat i enkla och komplexa former, kan vara kopplad till hur havens kemi förändrats både i proterozoikum (2.5-0.5 miljarder år sedan) och paleozoikum (0.5-0 miljarder år sedan. Även om fossil från moderna djur dyker upp runt ediacaran och kambrium, så finns det långt äldre fossil som kan påvisa flercellighet. Dessa fossil ger, om inte annat, anledning att leta vidare efter fler spår av pre-kambrisk flercellighet och kanske kan vi utöka våra sökmetoder till att också tolka ansamlingar, eller isotopsammansättningar, av spårmetaller. Den kambriska explosinen av djurliv (med startskott för 543 miljoner år sedan) är ett etablerat begrepp, men den senaste årens forskning har satt fokus på att en längre period, från ediacaran till devon, var en dynamisk tid med skiftande havskemi, nya djurarter och experimentella ekologiska nätverk. I den här avhandlingen presenteras några resultat som belyser just denna övergångstid, som geokemin i Chengjiang som beskriver hur havets kemi skiftar från syrefritt till sulfatfritt till syrerikt, och hur djur utan skal och ben kunde bli bevarade genom att flera unika förhållanden sammanföll. En annan studie visar hur molybden använts för att påvisa att atmosfärens syrehalt, under den här perioden, var högst hälften av vår moderna nivå. Vi hävdar att stigningen som skedde i devon, delvis tack vare växternas intåg på land, och att stigningen kan speglas i att fiskar först då hade råd att jaga och växa sig stora. Slutligen visar jag också på hur det första stora massutdöendet kan vara sammankopplat med syrefria hav, snarare än kyla och mer syre än djuren klarade av. Ett komplext samspel mellan flera kemiska ämnen, utöver syre, tektonisk aktivitet och biologi ser ut att höra samman med den dramatiska uvecklingen för stora livsformer på jorden.
39

Studies on the chemistry of lichens

Wachtmeister, Carl Axel January 1958 (has links)
Särtryck ur Svensk kemisk tidskrift 70:3(1958). Härtill 8 uppsatser. Uppsatserna saknas.
40

Kemi i grundskolan / Chemistry in secondary school

Eskilsson, Eva January 2000 (has links)
Då målen i nuvarande läroplan, Lpo 94 inte preciserar vilka avsnitt som ska tas upp i kemiämnet i grundskolan har jag i denna studie undersökt detta. Studien omfattar en enkätundersökning som besvarats av lärare i årskurserna 7-9 och en litteraturstudie. I litteraturstudien har jag studerat läromedel och kemiundervisningen i gamla styrdokument såsom läroplaner, studieplaner, undervisningsplaner och kursplaner från 1919 och framåt. Resultatet från enkätstudien visar bl.a. att de flesta skolorna som deltagit i min studie läser kemi som ett separat ämne och utgår från någon lärobok när de lägger upp undervisningen. Litteraturstudien visade att gamla styrdokument är förvånansvärt moderna när det gäller innehåll och upplägg av kemundervisningen. Man har dock tidigare oftast mera utförligt beskrivit vad som bör tas upp. I stort sett rekommenderar man samma innehåll i kemiundervisningen genom åren men med tiden ger man mera frihet för lärarna att lägga upp undervisningen.

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