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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.
331

The Effects of Omega-3 Supplementation on Human Skeletal Muscle Sarcolemmal and Mitochondrial Membrane Fatty Acid Composition and Whole Body Substrate Oxidation

Gerling, Christopher 07 September 2013 (has links)
This thesis investigated the effects of omega-3 supplementation (2.0 g/day EPA + 1.0 g/day DHA) for 12 weeks on human skeletal muscle sarcolemmal and mitochondrial membrane fatty acid (FA) composition and whole body energy expenditure in young healthy males. Supplementation resulted in significant incorporation of EPA and DHA into sarcolemmal and mitochondrial membranes, with an increase in total unsaturation of mitochondrial membranes. The incorporation profile of the sarcolemma and mitochondria differed, with the mitochondria mimicking changes in whole muscle. There were no changes in the protein content of mitochondrial and selected proteins involved in energy metabolism, except for a significant increase in the long form of UCP3. Despite changes in membrane FA compositions, there were no changes in whole body substrate oxidation at rest or during exercise. These data demonstrate that omega-3 supplementation for 12 weeks altered the FA composition of sarcolemmal and mitochondrial membranes in human skeletal muscle.
332

Design and Characterization of RF-LDMOS Transistors and Si-on-SiC Hybrid Substrates

Lotfi, Sara January 2014 (has links)
With increasing amount of user data and applications in wireless communication technology, demands are growing on performance and fabrication costs. One way to decrease cost is to integrate the building blocks in an RF system where digital blocks and high power amplifiers then are combined on one chip. This thesis presents LDMOS transistors integrated in a 65 nm CMOS process without adding extra process steps or masks. High power performance of the LDMOS is demonstrated for an integrated WLAN-PA design at 2.45 GHz with 32.8 dBm output power and measurements also showed that high output power is achievable at 5.8 GHz. For the first time, this kind of device is moreover demonstrated at X-band with over 300 mW/mm output power, targeting communication and radar systems at 8 GHz. As SOI is increasing in popularity due to better device performance and RF benefits, the buried oxide can cause thermal problems, especially for high power devices. To deal with self-heating effects and decrease the RF substrate losses further, this thesis presents a hybrid substrate consisting of silicon on top of polycrystalline silicon carbide (Si-on-poly-SiC). This hybrid substrate utilizes the high thermal conductivity of poly-SiC to reduce device self-heating and the semi-insulating properties to reduce RF losses. Hybrid substrates were successfully fabricated for the first time in 150 mm wafer size by wafer bonding and evaluation was performed in terms of both electrical and thermal measurements and compared to a SOI reference. Successful LDMOS transistors were fabricated for the first time on this type of hybrid substrate where no degradation in electrical performance was seen comparing the LDMOS to identical transistors on the SOI reference. Measurements on calibrated resistors showed that the thermal conductivity was 2.5 times better for the hybrid substrate compared to the SOI substrate. Moreover, RF performance of the hybrid substrate was investigated and the semi-insulating property of poly-SiC showed to be beneficial in achieving a high equivalent substrate parallel resistance and thereby low substrate losses. In a transistor this would be equal to better efficiency and output power. In terms of integration, the hybrid substrate also opens up the possibility of heterogeneous integration where silicon devices and GaN devices can be fabricated on the same chip.
333

Analysis and Design of a Fluidic-Reconfigurable Substrate Integrated Waveguide Resonator

Barrera, Joel 2011 December 1900 (has links)
Microwave filters play key roles in controlling the frequency response at specific locations of any communications, radar, or test system. Microwave resonators provide the frequency selective building blocks necessary for filter design. Reconfigurable/ tunable microwave resonators have facilitated the design of tunable filters. Recently, MEMS based tuning mechanisms developed widely tunable resonators maintaining high Q; however, limit in the number of reconfiguration states. This thesis proposes a fluidic-reconfigurable Xband SIW resonator capable of continuous tunability across the reconfiguration range. A dielectric post of fluidic dispersions with variable material properties embedded in a two inductive post static SIW resonator defines the tuning mechanism. The development of an analytical closed-form expression for the resonant frequency and Q across reconfiguration, a circuit model, and full-wave simulation predicts the tunable performance with estimated material properties of the fluidic dispersion. Measured data on an initial tunable SIW resonator design showed good reconfiguration performance but more losses than expected which could potentially be explained from the discovery of a major design error not associated with the resonator itself. A second tunable SIW resonator designed and fabricated proves the material properties of the fluidic dispersions contain more losses than estimated and hinder the resonators performance. By comparing simulated and measured data new estimates for the material properties of the fluidic dispersion are proposed which agree with trends in recent literature. Low-loss fluidic dispersions will enable a significant performance increase in the current tunable SIW resonator. Two low-cost material measurement systems are designed to expedite research efforts in finding low-loss microwave fluidics. Both systems accurately compute dielectric constant but not loss tangents. The initial systems provide necessary first steps in the design of future highly accurate material measurement systems.
334

Investigating the substrate specificity of 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAH7P) synthase

Tran, David January 2011 (has links)
The shikimate pathway is a biosynthetic pathway that is responsible for producing a variety of organic compounds that are necessary for life in plants and microorganisms. The pathway consists of seven enzyme catalysed reactions beginning with the condensation reaction between D-erythrose 4-phosphate (E4P) and phosphoenolpyruvate (PEP) to give the seven-carbon sugar DAH7P. This thesis describes the design, synthesis and evaluation of a range of alternative non-natural four-carbon analogues of E4P (2- and 3-deoxyE4P, 3-methylE4P, phosphonate analogues of E4P) to probe the substrate specificity of different types of DAH7P synthases [such as Mycobacterium tuberculosis (a type II DAH7PS), Escherichia coli (a type Ialpha DAH7PS) and Pyrococcus furiosus (a type Ibeta DAH7PS)].
335

Controlling the substrate specificity of α-isopropylmalate synthase and related enzymes

Hunter, Michael Forbes Clifford January 2013 (has links)
The enzyme α-isopropylmalate synthase (IPMS) catalyses the reaction between acetyl coenzyme A (AcCoA) and α-ketoisovalerate (KIV) to produce free coenzyme A and α isopropylmalate (IPM). This reaction is a key control point in the biosynthesis of a leucine, a pathway absent in animals but present in plants, fungi and bacteria. As a result, IPMS is a antibiotic and herbicidal target that has been validated by knockout studies for M. tuberculosis, the causative agent of tuberculosis. Engineered IPMSs have also been used in the fermentative production of long chain alcohols for use as fuels. IPMS belongs to a family of related enzymes called α-ketoacid: AcCoA re-aldolases (KARAs), with each subfamily differing in the specific α-ketoacid that AcCoA is reacted with. The known KARA subfamilies are IPMS, citramalate synthases (CMSs), homocitrate synthases (HCSs), methylthioalkylmalate synthases (MAMSs) and re-citrate synthases (RCSs), respectively involved in the biosynthesis of isoleucine, lysine, glucosinolates and TCA cycle intermediates. This thesis describes work aimed at improving understanding of both specific subfamilies of KARA enzymes and also the genetic and functional relationships between the subfamilies. A particular emphasis is placed on relating primary structure to function, allowing the inference of function from a very small subset of residues. IPMSs are divided into two classes, the Mtu-like IPMSs and the much less studied Eco-like IPMSs. Chapter 2 details the expression and characterisation of the Eco like IPMS from N. meningitidis (NmeIPMS). Overall NmeIPMS showed similar properties to MtuIPMS, but unlike that enzyme NmeIPMS is inhibited by high divalent metal ion concentrations, does not require monovalent metal ions, and shows some activity with the α-ketoacid 3-methyl α ketovalerate. Several previous results showing inhibitory activity of Zn2+, Cd2+ and bromopyruvate were also found to be the results of interference with the assay system and all three were found to be much weaker inhibitors than previously determined.   Phylogenetic analysis of the different KARA subfamilies revealed certain specific positions that were believed to control substrate specificity. Chapter 3 details mutagenesis experiments on MtuIPMS that probe the function of these residues. Once the importance of the residues had been established, substitutions were made in which IPMS residues were replaced with their equivalents from HCSs and CMSs in order to change substrate specificity. The most successful result was the Y169L substitution based on HCS, which decreased the specificity constant with KIV by four orders of magnitude while improving other activities, successfully shifting the best activity to the unbranched α-ketoacid α-ketobutyrate. Chapter 4 of this thesis details the purification and functional testing of the RCS from C. saccharolyticus (CscRCS), the first thermophilic RCS characterised. CscRCS was found to have an extremely low Km for its substrate oxaloacetate (1.7 µM), believed to be an adaptation to the instability of oxaloacetate at the temperatures CscRCS operates at in vivo. The enzyme also showed competitive affinity by α-ketoglutarate, the end product of the pathway. Unlike other characterised RCSs, CscRCS showed no oxygen sensitivity. The phylogenetic analysis conducted for this thesis identified a subfamily of KARAs dubbed pseudo-IPMSs (PIPMSs) that showed no substantial homology to any studied subfamily. In Chapter 5 the PIPMS from T. thermophilus (TthPIPMS) was expressed and characterised. TthPIPMS showed many features of a CMS, being most active with the same substrate (pyruvate) and sensitive to the same inhibitor (isoleucine). Unlike the previously studied CMS subfamilies, TthPIPMS possesses a nanomolar IC50 for its inhibitor, and also shows substantial activity as an RCS. The results of these chapters are then drawn together in Chapter 6 to create a picture of the relationships between the KARA enzymes, in terms of their functional characteristics as well as the sequence and evolutionary relationships between them that have bought about their diverse functions.
336

How does nutrients and light affect algal growth in Swedish headwater streams? : A study using nutrient diffusing substrate and natural gradients of light / Hur påverkar näring och ljus algtillväxt i svenska bäckar? : En studie med diffunderande näringssubstrat och naturliga ljusgradienter

Andersson, Jannika January 2014 (has links)
Gaining knowledge about what factors determine benthic algal biomass and productivity is vital for understanding food webs in aquatic systems, especially in woodland streams with naturally low rates of primary productivity. The aim of this study was to investigate what factors determine algal growth in Swedish headwater streams. Nutrients, in terms of nitrogen (N) and phosphorus (P), and light are factors known to affect algal growth. By using nutrient diffusing substrate (NDS) and different gradients of light, it was possible to test the importance of these factors. To determine the effect of the experiment, the study was carried out in a forested reference stream, which is largely shaded with extreme low nutrient levels, and in a stream running through a clear-cutting plantation with high nutrient levels and incident light. In the forested reference stream it became clear that algal growth increased by experimentally adding N (P<0.005), although light did not affect the productivity. In the stream running through the clear-cut, algal productivity increased significantly with higher levels of light (P<0.005), regardless of nutrient addition. The results from this study suggest that light only becomes the depending factor when sufficient amounts of nutrients are available. However, it is still unclear at what nutrient levels this shift occur, and therefore future research is recommended.
337

ROLE OF REPLICATION PROTEIN A (RPA) AND PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) IN DNA MISMATCH REPAIR

Guo, Shuangli 01 January 2005 (has links)
PCNA and RPA are required for DNA mismatch repair (MMR), but their rolesin the pathway are not fully understood. Using an affinity pull-down approach, weshow that (1) increased PCNA binding to DNA heteroduplexes is associated withthe appearance and accumulation of excision products; and (2) RPAphosphorylation occurs when DNA polymerase ?? binds to the DNA substrate. Wetherefore hypothesize that PCNA plays an important role in mismatch-provokedexcision and that RPA phosphorylation plays an important role in DNA resynthesis.To determine the role of PCNA in MMR, mismatch-provoked and nick-directedexcision was assayed in a cell-free system in the presence of the PCNA inhibitor,p21CIP1/WAF. We show that whereas PCNA is essential for 3' directed excision, it isdispensable for the 5' directed reaction, suggesting a differential role for PCNA inMMR. We further find that the PCNA-dependent pathway is the only pathway for3' directed excision, but there are at least two pathways for 5' directed excision,one of which is a PCNA-independent 5' excision pathway. To determine if RPAphosphorylation facilitates DNA resynthesis, a gap-filling assay was developedusing both a cell-free system and a purified system, and we demonstrate that RPAphosphorylation stimulates DNA polymerase ??-catalyzed resynthesis in bothsystems. Kinetic studies indicate that phosphorylated RPA has a lower affinity forDNA compared with un-phosphorylated RPA. Therefore, the stimulation ofresynthesis by phosphorylated RPA is likely due to the fact that phosphorylationpromotes the release of RPA from DNA, thereby making DNA template availablefor resynthesis.
338

Integrated Treatment Processes For Primary Wool Scouring Effluent

Savage, Matthew John January 2003 (has links)
The increasing cost of effluent treatment in the wool scouring industry is rapidly becoming a determining factor in the viability of existing scouring operations and new installations alike. This thesis details the development of an integrated effluent treatment process capable of treating the worst polluted effluent from a wool scour "heavy flow-down", to the point where it can either be economically discharged to local trade waste sewer, or directly discharged to river or ocean outfall with minimal environmental impact. The existing proprietary chemical flocculation process, Sirolan CF™, was improved by the addition of a bio-flocculation stage and turbidity monitoring and control, and the product from this process fed to an aerobic biological treatment system based upon the traditional activated sludge process. The biological treatment process was found to remove up to 98% of the BOD5 loading from the pre-treated liquor with a hydraulic residence time of at least 50 hours being required in the aerobic digestion vessels. A residual biorefractory COD of approximately 3,600mg/L was identified which could not be removed by biological treatment. When operating continuously, the biological process was observed to metabolically neutralise the pH 3.0 - 4.5 feed from the chemical flocculation system to pH &gt 7.0 without the need for supplemental addition of neutralising agents such as sodium hydroxide. This in itself provides a significant economic incentive for implementation of the process. Kinetic analysis of the biological process carried out under controlled laboratory conditions using a Bioflo 3000 continuous fermentor showed that the bio-chemical process followed substrate inhibition kinetics. An appropriate kinetic model was identified to represent the behaviour of the substrate degradation system, and modified by inclusion of a pseudo toxic concentration to account for the effect of pH inhibition upon the biological growth rate. The process was verified both at pilot plant scale and at demonstration plant scale at an operational wool scour. The demonstration plant was of sufficient size to handle the full heavy effluent flow-down from a small wool scour. At the time of publishing three full-scale effluent treatment systems based on this research had been sold to both domestic and international clients of ADM Group Ltd. who funded the research.
339

FABRICATION OF VERTICALLY ALIGNED CARBON NANOTUBES AND HORIZONTAL NANO-STRUCTURES

Hu, Wenchong 01 January 2002 (has links)
Fabrication of ordered anodic alumina nanopore arrays and anodization parameters including electrolyte, concentration, voltage, temperature and time have been investigated. Cobalt nanoparticles were electrodeposited at the bottom of the pores. Vertically aligned, open-tipped multi-walled carbon nanotube arrays of high density and uniformity were synthesized via a flame method on silicon substrates using a nanoporous template of anodized aluminum oxide. The diameter and length of the nanotubes are controlled by the geometry of the aluminum oxide template. It is the cobalt catalyst particles, not the porous aluminum templates, help the growth of carbon nanotubes through graphitization and bonding of carbon nanotubes to the silicon substrates. Fabrication of nano-structures has been demonstrated. Nano-trenches of 20 nm have been achieved using single-walled nanotube bundles as shadow masks, which were aligned across electrodes under high frequency AC voltage.
340

FABRICATION AND CHARACTERIZATION OF POROUS ALUMINA AND CADMIUM SULFIDE FOR OPTOELECTRONIC APPLICATIONS

Jayaraman, Vivekanand 01 January 2004 (has links)
In this research work, porous films on aluminum foil, with vertical through and through pores, were fabricated. The films were anodized at different applied voltages and the conditions were reported. In some cases, aluminum foil films were anodized under constant current conditions. Thicker aluminum films, referred to as aluminum tape in this thesis, were also anodized to get good porous films. While the porous alumina films using aluminum tape produced pores with good uniformity, the films did not produce through and through pores. Porous alumina films were also prepared on aluminum evaporated ITO substrate. The films on ITO substrate were different from the porous alumina films using aluminum foil/tape. In case of ITO substrate based films, an additional condition, temperature was also varied. The anodization process on ITO substrate based films was done at lower temperatures in order to reduce the effect of high currents on the process. The SEM images for different anodization conditions were compared and the porosity of films was calculated. CdS was electrodeposited inside porous alumina. D.C as well as a.c. voltages were applied and duration of the process was varied to study their effect on film morphology and the thickness of the deposited CdS. The current-voltage characteristics of the CdS-deposited alumina films were plotted and the phase of the electrodeposited CdS was found to be hexagonal using XRD.

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