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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

Design of Glutathione Transferase Variants for Novel Activities with Alternative Substrates

Shokeer, Abeer January 2010 (has links)
Glutathione transferases (GSTs) play a pivotal role in cellular defense, since they are main contributors to the inactivation of genotoxic compounds of exogenous and endogenous origins. Directed evolution was used to improve the catalytic activities of Theta class GST T1-1 toward different substrates. The library was constructed by recombination of cDNA coding for human GST T1-1 and rodent Theta class GSTs, resulting in the F2-F5 generations. The clones were heterologously expressed in Escherichia coli and screened for variants with enhanced alkyltransferase activity. A mutant, F2:1215, with a 70-fold increased catalytic efficiency with 4-nitrophenethyl bromide (NPB) compared to human GST T1-1, was isolated from the second generation. NPB was used as a surrogate substrate of the anticancer drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in order to facilitate the screening process. The catalytic efficiency of the F2:1215 with BCNU had improved 170-fold compared to wild-type human GST T1-1, suggesting that NPB is a suitable model substrate for the anticancer drug BCNU. The sequence of the F2:1215 mutant differs from wild-type human GST T1-1 by three residues; one of these differences is Arg234, which corresponds to Trp in the human enzyme. Upon replacing the Trp234 in the human GST T1-1 with Arg, the resulting mutant (hTrp234Arg) showed enhanced alkyltransferase activity with a wide range of substrates (e.g. haloalkanes and other typical GSTs substrates). The three-dimensional structures of both wild-type human GST T1-1 and hTrp234Arg mutant help to explain the higher activity showed by of hTrp234Arg mutant compared to wild-type enzyme. The reciprocal mutation of the residue 234 in mouse GST T1-1 to that found in human, mArg234Trp, caused a dramatic decrease in the activity of the mouse enzyme to be similar to human GST T1-1. This indicates that residue 234 can be considered as a master switch of activities between human and rodent GST T1-1. Another important residue in the C-terminal helix of GST T1-1 is Met232. Although residue 232 points away from the H-site, it influences the catalytic activity and substrate selectivity of the mouse GST T1-1. A minor modification of Met232 induces major changes in the substrate-activity profile of the mouse GST T1-1 to favor novel substrates such as isothiocyanates and hydroperoxides and decreases the activity toward substrates that catalyzed by the wild-type enzyme.
62

Synthesis and study of new oxazoline-based ligands

Tilliet, Mélanie January 2008 (has links)
This thesis deals with the study of oxazoline-based ligands in metal-catalyzed asymmetric reactions. The first part describes the synthesis of six new bifunctinal pyridine-bis(oxazoline) ligands and their applications in asymmetric metal-catalysis. These ligands, in addition to a Lewis acid coordination site, are equipped with a Lewis basic part in the 4-position of the oxazoline rings. Dual activation by means of this system was probed in cyanide addition to aldehydes. The second part is concerned with the synthesis of two pyridine-bis(oxazoline) ligands bearing bulky triazole groups in the 4-position of the oxazoline rings and a macrocyclic ligand consisting of a pyridine-bis(oxazoline) moiety and a diaza-18-crown-6 ether. The synthesis of these compounds benefits from the use of “click chemistry”. The ligands thus obtained were tested in different asymmetric catalytic reactions. Complexation studies with different bifunctional molecules that could bind into the cavity of the macrocycle were carried out using NMR spectroscopy. A third chapter is devoted to the synthesis of a supported pyridine-bis(oxazoline) catalyst and its use in catalysis. The pyridine-bis(oxazoline) ligand was efficiently connected to a polystyrene resin via a robust triazole linker. This resin could be employed in different metal-catalyzed asymmetric reactions and good results were obtained in terms of yield and enantioselectivity. Moreover, this polymer-bound ligand could be easily and efficiently recycled. Finally, the last part deals with the use of a hydroxy-containing phosphinooxazoline ligand in the hydrosilylation of imines and in the asymmetric intermolecular Heck reaction. A cationic iridium complex of this ligand was studied by NMR spectroscopy. / QC 20100914
63

Synthesis of a Novel Tocopherol/Carotenoid Derivative

Haugland, Marius Myreng January 2012 (has links)
The goal of this work is the synthesis of a tocopherol/carotenoid hybridderivative (1, figure II). The novel derivative is believed to exhibitsynergistic antioxidant effects between its chromanol and polyene consituents.The synthesis of 1 was completed up to and including theimmediate precursor 12.Commercially avaliable Trolox (7) was reduced by Red-Al® to 8(step a) in 95% yield. Chromanol aldehyde 9 was formed by Swernoxidation of 8 in 65% yield (step b). Wittig reaction between 9 andphosphonium salt 10 afforded 11 in 33% yield and varying cis : transratio (step c), and subsequent elongation produced 12 (14% yield, stepd). The Wittig reactions were performed with reflux and microwaveirradiation.Various attempts at protecting the phenolic group in intermediate8 by silylation or benzylation did only lead to formation of 8B.Oxidation of 8 by the Dess-Martin oxidation formed the unexpectedquinone-like derivative 27. Efforts to protect the phenolic group in intermediate9 by benzoylation and silylation only produced 9A, foundto be unsoluble in all common laboratory solvents.
64

Budgetstyrning i företag med kraftig organisk tillväxt : En fallstudie på Infocare Workshop AB

Green, Henrik, Sundbom, Magnus, Törnström, Håkan January 2006 (has links)
Budgeten verkar vara ett bra styrmedel i början av året men ju längre året går desto mindre aktuell blir den. Prognoserna tar vid och blir det verkliga styrmedlet. Trots detta fortsätter företaget att jämföra verkligt utfall med budgeterat resultat. Budgeten kan när företaget når mogen fas åter bli aktuell som styrmedel.
65

Budgetstyrning i företag med kraftig organisk tillväxt : En fallstudie på Infocare Workshop AB

Green, Henrik, Sundbom, Magnus, Törnström, Håkan January 2006 (has links)
<p>Budgeten verkar vara ett bra styrmedel i början av året men ju längre året går desto mindre aktuell blir den. Prognoserna tar vid och blir det verkliga styrmedlet. Trots detta fortsätter företaget att jämföra verkligt utfall med budgeterat resultat. Budgeten kan när företaget når mogen fas åter bli aktuell som styrmedel.</p>
66

Triton – Beneath Our Feet : att hitta ett sound till Tritons debutalbum

Nylén, Martin January 2013 (has links)
Syftet med mitt examensarbete har varit att skriva, arrangera och spela in musik till Tritons kommande debutskiva, Beneath Our Feet. Arbetet består av två delar, en skriftlig del där jag redogör för dels en sammanfattning av den förberedande kursen 2012, som legat till grund och möjliggjort mitt arbete. Dels också huvudarbetet under 2013 där jag i egenskap av projektledare, producent och musiker genomfört den studioinspelning som utgjort vårt mål.Den andra, konstnärliga och klingande delen av mitt arbete gestaltas av de 8 låtinspelningarna jag tillsammans med Triton åstadkommit i Studio 2 på KMH. / <p>Bilaga: 2 CD</p>
67

Impact of increased production on TOC to the Waste Water Treatment Plant : Piteå 750

Lundberg, Johan January 2017 (has links)
Today there are strict demands regarding emissions to water and air from the Swedish industries. This degree project, conducted at Smurfit Kappa Piteå, will focus on the emissions of organic material in waste water from the paper mill. The overall goal was through dynamic simulations predict the Total Organic Carbon (TOC) emissions from the paper mill at the time a foreseen increase of production is implemented. The recovery boiler is currently a bottleneck in the process and the production of sulphate pulp has today its maximum capacity. This means that production growth will occur exclusively by increasing the intake of recycled fiber. The work started with a comprehensive mapping of TOC, in which ingoing pulps in pulp towers, head boxes and effluent flows were mapped. This was done over a period of two weeks and thus covered a whole production cycle. A TOC method evaluation was conducted where the most suitable analysis method was determined. Mapped data were thereupon evaluated and significant variables were identified. It was determined that use of recycled fiber was the single most important variable to TOC load from paper machine 1 (PM1), but also starch addition to paper machine 2 (PM2) was found to be significant. The work then continued with the simulation phase, consisting of two main parts. The first part consisted of preparatory work where the model was developed to be able to accurately measure TOC load to the waste water treatment plant. This part also included work to identify necessary process changes as a result of an increased production. The second part consisted of the simulation. Three different scenarios were simulated for each paper machine plus two scenarios for the recycled fiber plant. The dynamic simulation model was successively calibrated with respect to TOC concentration and trends followed the ones expected by experience. In the production increase scenario simulated, TOC load distribution between PM1, PM2 and recycled fiber plant will more evenly distributed compared to current production. The largest increase of TOC load will come from the recycled fiber plant, which according to the simulation will increase with about 30 %. / Idag ställs höga krav på de svenska industrierna vad avser utsläpp till vatten och luft. I detta examensarbete som utförts på Smurfit Kappa Piteå undersöktes avloppsflöden från pappersbruket till bioreningsanläggningen. Den övergripande målsättningen var att genom dynamiska simuleringar prediktera de TOC utsläpp pappersbruket kommer att generera efter planerad produktionsökning. Sodapannan är i dagsläget en flaskhals i processen, något som medför att produktionen av nyfibermassa idag så hög den kan vara. Detta medför att produktionsökningen uteslutande kommer att bestå av ökat intag av returfibermassa. Arbetet startade med en omfattande TOC kartering där ingående massor, inloppslådor samt avloppsflöden karterades. Detta utfördes under två veckor och täckte på så sätt en hel produktionscykel. En metodutvärdering genomfördes där lämplig metod för att mäta TOC i just de karterade provpunkterna bestämdes. Erhållna data från karteringen analyserades därpå och signifikanta variabler utvärderades. Det konstaterades att användningen av returfibermassa var den enskilt mest korrelerade variabeln till TOC nivå för pappersmaskin 1 (PM1), samt att stärkelsetillsats på pappersmaskin 2 (PM2) påvisades vara signifikant under den karterade perioden. Simuleringsfasen tog sedan vid, vilken bestod av två delar. En del bestod av förberedande arbete där modellen utvecklades för att simulera TOC halt med så god precision som möjligt. I denna del ingick även arbete för att ta fram nödvändiga processförändringar i och med den ökade produktionen. Den andra delen bestod av själva simuleringsfasen där tre olika scenarion simulerades för respektive pappersmaskin samt två stycken för returfiberanläggningen. Den dynamiska simuleringsmodellen lyckades på ett bra sätt balanseras med karterade mätdata. De utförda simuleringarna av TOC belastning till bioreningen påvisade rimliga resultat och följde de trender som erfarenhetsmässigt kan förklaras. Vid den simulerade produktionsökningen scenariot kommer TOC fördelningen mellan PM1, PM2 och returfiberanläggningen vara mer jämnt fördelat. Den största ökningen av TOC belastning kommer från returfiberanläggningen som enligt simuleringen kommer att öka med omkring 30 %.
68

Synthesis and Characterization of Acrylfentanyl Metabolites

Alfredsson, Maria January 2017 (has links)
Acrylfentanyl is a synthetic opioid that has been widely used in the last year. To help in the fight against synthetic drugs two potential metabolites of acrylfentanyl, one monohydroxy and one dihydroxy were synthesized. These metabolites will hopefully later be implemented in the analytical methods for metabolites of acrylfentanyl in urine by the Swedish National Board of Forensic Medicine. To have metabolites for analysis are very important as they are the main target in drug testing. The method used to synthesize the metabolites is a five-step synthesis with an additional 6th step for the dihydroxy metabolite. The methods used in the synthesis includes protection of amine with tert-butyloxycarbonyl, reductive amination with sodium triaceto boronhydride, alkylation and demethylation with boron tribromide. The methods used produced good results with high yields in nearly all steps.
69

Synthesis, characterization and water oxidation activity of iron, cobalt and copper complexes of a tetradentate polypyridine ligand

Ziyi, Peng January 2021 (has links)
No description available.
70

Organisk Rankine cykel i konfiguration med naturgasdrift.

Hektor, Eric January 2023 (has links)
Organisk Rankine cykel är en förångningscykel med användningen av en organisk fluid för att få bättre lågtempererade egenskaper än vid användningen av vattenånga. Naturgas är ett bränsle som används inom industrin och sjöfarten, den förvaras mycket kallt i vätskeform för att spara utrymme. Detta bränsle förångas antingen naturligt eller med syftet att förbränna den i gasform. Detta för att minska behovet av kryogenisk teknik. Förångningen sker med att tillföra värme till bränslet. Genom att förgrena ångcykelns behov av kondensering och bränslets behov av värme kommer massflödet för kondenskylningen att minska. Det ger i sin tur en stadigare drift i varma miljöer. Frågeställningen var hur mycket effekt som kunde hämtas ur denna konfiguration. Hur mycket mindre kondenseringsanläggningen blir och den möjliga systemkonfigurationen utifrån aspekten av säkerhet, effekt och goda möjligheter till reglering. Tillvägagången var först att studera systemen ingående, hur de funkar och för att ta fram de fysikaliska data. Sedan teoretiskt bygga samman systemen och göra beräkningar. Resultatet påvisade låg effekt men med ett behov av en 11 gånger mindre kondensor jämfört med vattenkylning. Slutsatsen är att denna konfiguration begränsar den potentiella effekten mycket men minskar effektbehovet för att driva ångprocessen och att kondenseringsanläggningen blir mindre. / Organic Rankine cycle is a vaporization cycle where an organic fluid is used toobtain better low-temperature properties than when using water vapor. Natural gasis a fuel used in industry and shipping it is stored very cold in liquid form to savespace. This fuel is either vaporized naturally or with the aim of burning it in gaseousform. This is to reduce the need for cryogenic technology. Vaporization takes placeby adding heat to the fuel. By branching the steam cycle's need for condensation andthe fuel's need for heat, the mass flow for condensation cooling will decrease. Thisin turn provides a more stable operation in warm environments. The question washow much power could be extracted from this configuration. How much smaller thecondensing plant will be and the possible system configuration from the aspect ofsafety, power, and good solutions for control. The approach was to first study thesystems in detail, how they work and to produce the physical data that was required.Then theoretically build the systems together and make calculations. The resultshowed low power but with a need for an 11 times smaller condenser compared towater cooling. The conclusion is that this configuration greatly limits the potentialpower but reduces the power requirement to drive the steam process and thecondensing plant becomes smaller.

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