Browsing Research Scholars Theses by Title
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Evetts, Elizabeth A.; Peterson, Jacqueline A. (September 30, 2009)[more][less]
Abstract: The above- and below-ground litter from fallen foliage and root exudates and their decomposition has an impact on forest soil. The objective of this research project was to determine the effect of above- and below-ground litter manipulation on the retention and release of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), nitrate and ammonium in the soil profile at 0-5 and 5-15 cm depths. The soils were obtained from a Long Term Ecological Research site in the Sikfokut Forest in Hungary. The site is a mature oak forest and the soil has no organic layer; the leaf litter sits directly on the A horizon. There are six treatments applied to the soil: doubling of annual leaf litter (DL), doubling of annual wood litter (DW), removal of annual leaf litter (NL), removal of roots (NR), removal of leaf and roots (NI) and control (C). Each plot is 7 x 7 m, and each soil sample taken was 15 x 15 cm square. A stock solution of leaf litter was added in different concentrations to soils from each treatment in a 50 mL centrifuge tube. Because I was investigating retention or release of carbon and nitrogen, I inverted the tube gently over a period of 2 hours prior to centrifugation and removal of supernatant. The supernatant solution was analyzed for DOC, DON, ammonium and nitrate to determine retention and release values for each dependant upon the different treatments. The results of the study were interesting. Dissolved organic nitrogen was neither retained nor released in the 0-5 cm layer for any treatment yet nitrate, typically considered a mobile anion showed retention and release in this layer. In the 5-15 cm layer we had no retention or release of nitrate but dissolved organic nitrogen was retained and released between the solid and solution phases. URI: http://handle.tamu.edu/1969.1/88040 Files in this item: 1
Evetts_Approved_Thesis.pdf (131.3Kb) -
LaFleur, Adrienne; Charlton, William (September 17, 2007)[more][less]
Abstract: An algorithm was developed that uses measured isotopic ratios from fission product residue following the detonation of a high-enriched uranium nuclear weapon to compute the original attributes of the material used in the device. The specific attributes assessed are the uranium isotopics (considering 234U, 235U, 236U, and 238U) and the enrichment process used to create the material (e.g., gaseous diffusion, gas centrifuge, etc.). Using the original attributes of the weapon significantly increases the probability of identifying the perpetrator of the attack. In this study, research was conducted to perform sensitivity analysis of the calculated values, analyze alternate enrichment methods, determine the source (uranium mine) from which the feed material was taken and assess potential “spoofing” techniques. The purpose of this research was to verify that the analytical method developed would remain valid for a multitude of variations that could be used to disguise the origin of the nuclear material in the device. It is envisioned that this methodology could serve as a preprocessing step to a more computationally intensive and more accurate system in the event of a nuclear terrorist attack. URI: http://handle.tamu.edu/1969.1/5720 Files in this item: 1
2007 LaFleur Thesis.pdf (1.048Mb) -
Chateau, Morgan (September 17, 2007)[more][less]
Abstract: Many neurodegenerative diseases are associated with protein misfolding where the protein forms β-sheet rich polymers called amyloid. Alzheimer’s disease (AD) is an amyloid aggregation disease involving the Aβ(1-42) peptide fragment of the Amyloid Precursor Protein (APP) in the nervous tissue of the brain. Within the peptide there are regions thought to be more critical for amyloid formation; one of which is Aβ(25-35). This sequence has the ability to form amyloid at sufficient peptide concentrations. Within this region, residues 33-35 have been found by terminal deletions to be a core region (1), the residues necessary for amyloid formation. Using Cys-scanning mutagenesis the estimated core region (31-34) is slightly different. Previous papers have shown, the peptide loses the ability to form amyloid fibrils when the sequence of amino acids is changed (2). For this experiment, four different Aβ(25-35) sequences were tested, each having the same composition but a different sequence. FPLC was used in conjunction with Thioflavin-T fluorescence to monitor amyloid development. The results showed a definite effect on amyloid formation as compared to wild type. Sequence S-N showed nearly no change in behavior. Sequence S-M appeared to loose all amyloid forming ability. The remaining two sequences were unable to remain in solution long enough to be accurately tested. URI: http://handle.tamu.edu/1969.1/5722 Files in this item: 1
Final 2007 Spring Thesis.pdf (171.1Kb) -
Qiu, Xiaofan (September 17, 2007)[more][less]
Abstract: As portable electronic devices become a part of daily life, it creates a huge market for electronic components for those battery driven devices. Low-dropout (LDO) voltage regulator is an important part that provides steady DC supplies for other components. Low power, low noise and high stability are the desired features of a regulator. Detailed analyses on CMOS LDO design and the designs of two different compensation schemes for LDO are presented in this thesis. Experimental results of the designed compensation programmable low-power low-dropout (LDO) Voltage Regulator, in comparison with an existing compensated LDO, are also presented. The designed compensation implementation demonstrates a fast transient response and high stability in all programmable output levels. Testing chip fabricated in a standard 0.35 CMOS technology provided the important parameters of the regulator, e.g. transient response, load regulation, line regulation, power supply rejection ratio (PSRR). URI: http://handle.tamu.edu/1969.1/5721 Files in this item: 1
Research_Scholar_Thesis_Xiaofan_Qiu.pdf (317.1Kb) -
Pritchard, Megan (July 11, 2006)[more][less]
Abstract: Gas-cooled nuclear reactors have been receiving specific attention for Generation IV possibilities due to desired characteristics such as relatively low cost, short construction period, and inherent safety. Attractive inherent characteristics include an inert, single phase helium coolant, refractory coated fuel with high temperature capability and low fission product release, and graphite moderator with high temperature stability and long response times. The passively safe design has a relatively low power density, annular core, large negative temperature coefficient, and passive decay heat removal system. The objective of the U.S. DOE NERI Project is to assess the possibility, advantages and limitations of achieving ultra-long life VHTR (Very High Temperature Reactor) configurations by utilizing minor actinides as a fuel component. The present analysis takes into consideration and compares capabilities of pebble-bed core designs with various core and reflector configuration to allow spectrum shifting for advanced actinide fuels. Whole-core 3D models for pebble-bed design with multi-heterogeneity treatments in SCALE 5.0 are developed to compare computational results with experiments. Obtained results are in agreement with the available HTR-10 data. By altering the moderator to fuel ratio, a shift in the spectrum is observed. The use of minor actinides as fuel components relies on spectrum shifting capabilities. Actinide fueled VHTR configurations reveal promising performance. With an optimized pebble-bed model, the spectrum shifting abilities are apparent and effects of altered moderator to fuel ratio, and Dancoff factor are investigated. This will lead to a facilitated development of new fuel cycles in support of future operation of Generation IV nuclear energy systems. URI: http://handle.tamu.edu/1969.1/3663 Files in this item: 1
MPritchardUGRS.pdf (628.3Kb) -
Pritchard, Megan; Tsvetkov, Pavel (September 30, 2009)[more][less]
Abstract: Gas-cooled nuclear reactors have been receiving specific attention for Generation IV possibilities due to desired characteristics such as relatively low cost, short construction period, and inherent safety. Attractive inherent characteristics include an inert, single phase helium coolant, refractory coated fuel with high temperature capability and low fission product release, and graphite moderator with high temperature stability and long response times. The passively safe design has a relatively low power density, annular core, large negative temperature coefficient, and passive decay heat removal system. The objective of the U.S. DOE NERI Project is to assess the possibility, advantages and limitations of achieving ultra-long life VHTR (Very High Temperature Reactor) configurations by utilizing minor actinides as a fuel component. The present analysis takes into consideration and compares capabilities of pebble-bed core designs with various core and reflector configuration to allow spectrum shifting for advanced actinide fuels. Whole-core 3D models for pebble-bed design with multi-heterogeneity treatments in SCALE 5.0 are developed to compare computational results with experiments. Obtained results are in agreement with the available HTR-10 data. By altering the moderator to fuel ratio, a shift in the spectrum is observed. The use of minor actinides as fuel components relies on spectrum shifting capabilities. Actinide fueled VHTR configurations reveal promising performance. With an optimized pebble-bed model, the spectrum shifting abilities are apparent and effects of altered moderator to fuel ratio, and Dancoff factor are investigated. This will lead to a facilitated development of new fuel cycles in support of future operation of Generation IV nuclear energy systems. URI: http://handle.tamu.edu/1969.1/88044 Files in this item: 1
MPritchardUGRS.pdf (659.8Kb) -
Hickey, Matthew (June 9, 2009)[more][less]
Abstract: Toll-like receptors are an important part of the innate immune system and mediate infection via the recognition of pathogen-associated molecular patterns (PAMPs). Toll-like receptor 3 (TLR3) recognizes foreign-derived double stranded RNA as its ligand, and is active as a homodimer. Previous research has indicated that specific residues in TLR3’s extracellular domain (ECD) are responsible for dimer-dimer interactions between TLR3s, and the apparent specificity of this interaction has allowed for modulation of TLR3 signal through the use of dominant negative mutants. Here we present a class of mutants which lack the inter-disulfide cap region of the ECD (Δ123-635, hereafter called TLR3N-CT), yet still exhibit dominant negative properties. The degree of dominant negative inhibition of TLR3N-CT is comparable to that of TLR3 ΔToll interleukin-1 receptor (TIR), the previously established standard for dominant negativity. Tyrosine mutants, such as Y759F, have been shown to dramatically reduce TLR3 signal induction by interfering with cytoplasmic signaling adapters. Our mutant, TLR3N-CT Y759F, retained the ability to act as a dominant negative inhibitor of TLR3, thus indicating that the observed reduction in induced/uninduced signal was not due to ligand-independent activation of the mutant. Furthermore, the mutant TLR3N-CTΔTIR was generated to investigate the role of the cytoplasmic TIR domain in dimer-dimer interactions. This mutant was not a dominant negative inhibitor of TLR3 activity, indicating a possible role of the TIR domain in the dominant negative interaction between TLR3N-CT and wild type TLR3. It is possible that this TIR-TIR interaction is either in the incorrect confirmation for signaling or, contrary to previous reports that ligand binding and dimerization are necessary only to bring the TIR domains together, that more than simple TIR-TIR interaction is required for TLR3 signaling. However, expression studies by western blot have been unable to prove expression by any of the mutants previously discussed. Several explanations are possible, but it is likely that expression levels are sufficient for cell-based activity assays but too low for western blot detection. URI: http://handle.tamu.edu/1969.1/86490 Files in this item: 1
Hickey_Thesis[FINAL].pdf (235.5Kb) -
Fortenberry, Stephen (September 30, 2009)[more][less]
Abstract: In this effort, the temporal behavior of a manufactured alumina (Al2O3) – water nanofluid was evaluated. Measurements of nanofluid effective thermal conductivity were acquired over an extended time period. Analysis of acquired measurements elucidated the degradation of nanofluid effective thermal conductivity with respect to time. Specifically, the measured thermal conductivity of nanofluid decreased from an initial value of 0.6365 W/m-ºC to a final value of 0.6130 W/m-ºC over a period of several months. This corresponded to a change in the thermal conductivity enhancement realized due to the suspension of nanoparticles in fluid from an initial value of 11.2% to a final value of 7.2%. Temporal evolution of the nanofluid’s thermal conductivity is attributed to changes in the stability of the colloidal suspension. Future work is planned to investigate the physical mechanisms controlling this phenomenon. URI: http://handle.tamu.edu/1969.1/88032 Files in this item: 1
Fortenberry_Thesis_(Corrected)2.pdf (830.4Kb) -
Bartek, Christopher (June 9, 2009)[more][less]
Abstract: This thesis examines the production and distribution of ancestral Polynesian pottery on Tutuila Island, American Samoa and evaluates the extent of intra-island interactions. Currently, very little is known about ceramic production and exchange in Samoa. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is used to source clay and temper material to raw clay sources. Ceramic attribute analysis is used to identify technological styles, which will determine specific production groups. Variations of clays and tempers within a site determine the extent of exchange that occurred. By combining ceramic analysis and LA-ICP-MS, this research will help determine the number of production groups per village and demonstrate exchange patterns between villages. In 2006 Eckert argued that the presence of two technological styles in ancestral Polynesian pottery reflects two different production groups on the Samoan archipelago. Using LA-ICP-MS and ceramic attribute analysis, I show that exchange has occurred between four production groups. URI: http://handle.tamu.edu/1969.1/86504 Files in this item: 1
Bartek Thesis Final Copy.pdf (1.518Mb) -
Crannell, Zachary (July 11, 2006)[more][less]
Abstract: The process of viral infection has been shown to be a tightly structured process that exerts precise control over the nucleus. By quantitatively documenting the dynamic nuclear changes in response to nuclear infection of cells suspended in a three-dimensional collagen matrix, an understanding of nuclear reorganization can be elucidated from the tissue. Tissues were cultured in vitro in three dimensional collagen matrices which act as scaffolding that mimics the native environment. The cells were then infected with cytomegalo virus (CMV) which was labeled with green fluorescent protein to allow identification of the virus. During viral infection, nonlinear optical microscopy (NLOM) was employed to nondestructively image the nuclear volume over time. Comparing changes in the nuclear volume with control values, we expected to identify several stages of nuclear reorganization that have previously been identified during infection of 2D tissue cultures. Once it has been demonstrated that NLOM can be successfully used to track dynamics of infection, multiple mutant fluorescent proteins can be used to track host, virus and immune response to viral infection. URI: http://handle.tamu.edu/1969.1/3666 Files in this item: 1
crannell0503.pdf (350.6Kb) -
Bustamante, Nirma Dora (July 11, 2006)[more][less]
Abstract: Methylmercury (MeHg) remains to be a major public health concern because of the presence of widespread contamination of our environment and the severe neuropathological changes that can occur with exposure to the developing central nervous system (CNS). The blood-brain barrier (BBB) represents an important target for MeHg. However, before the BBB is fully formed or if the BBB is compromised once it is formed, it can not effectively isolate the brain from circulating toxins and foreign compounds. The current project examines the hypothesis that there is a correlation between childhood vaccination and the neurotoxic effects of mercury in the form of MeHg in the pathogenesis of autism. The effects from exposure to MeHg and activation of the immune system can affect neuronal survival and development and could result in the faulty wiring that appears to occur in the CNS of autistic children. Mice were exposed to low dose (0.03 µg/kg of body weight of the pregnant mouse) MeHg during prenatal development. Lipopolysaccharide (LPS) was administered during early iv postnatal development as an immunostimulant. In order to determine the optimal time in which the injection of LPS would be the most effective, mice were injected with LPS then euthanized and injected with Evans Blue dye at 4, 6, 22, and 48 hours. The brain was separated into forebrain, cerebellum, and brainstem. Using a fluorescence micro plate reader, the quantity of Evans Blue leaking into the brain through the BBB was calculated. It was determined the mice should be euthanized 6 hours after administration of LPS. LPS or the control solution, phosphate buffered saline (PBS), was administered at postnatal day 18 into mouse pups that received MeHg prenatally and then the integrity of the BBB was checked 6 hours later. No difference was observed between mice given LPS compared to the mice given PBS most likely due to too much variability. There may be an effect of LPS but it is masked by the variability that occurs when using this assay in such young mice. A radioactive assay using 14C-labeled sucrose is going to be used in order to acquire better results. URI: http://handle.tamu.edu/1969.1/3652 Files in this item: 1
THESIS-FINAL.pdf (57.56Kb) -
Samarajeeewa, Sandani (August 19, 2008)[more][less]
Abstract: Baeyer-Villiger (BV) oxidations are used to convert ketones and aldehydes to esters and phenols. These ester and phenols are useful building blocks in designing more complex organic materials in pharmaceutical chemistry. By using catalysts in the BV oxidations, high selectivity and conversion can be obtained while the waste production can be minimized. We have synthesized a new family of layered Sn(IV) phosphonate materials which are efficient catalysts in the BV oxidation of aromatic aldehydes. The most attractive feature of these catalysts is that the reaction can be carried out under solvent-free conditions using aqueous H2O2 (30 %) as the oxidant. Various Sn(IV) phosphonates have been synthesized using phosphonic acid in different solvent systems following a hydrothermal procedure. These catalysts have been characterized using X-Ray Powder Diffraction, Thermo Gravimetric Analysis and Surface Area and Pore Size Analysis. Following their synthesis, the catalytic ability of each of the samples was tested toward the BV oxidation of para substituted aromatic aldehydes to phenols. The products were identified using Mass Spectroscopy and the percent conversion and selectivity of the reaction were measured using Gas Chromatography. A noticeable trend was found between percent conversion and high external surface area. URI: http://handle.tamu.edu/1969.1/85735 Files in this item: 1
Samarajeewa_Approved_Thesis.pdf (3.623Mb) -
Mera, Linet (July 11, 2006)[more][less]
Abstract: Phage, although but a fraction of the size of bacteria, can, by lysogenic conversion, transform a harmless bacterium into a ruthless pathogen (3). This paper will discuss two new lysogenic dsDNA tailed phages of Burkholderia. Bcep176 was induced from Burkholderia multivorans ATCC17616, thought to be found in pulmonary infections (9), and Bglu421, from a rice seed isolate of B. glumae BG 10421, known to be the causative agent for rice seed rot (19). The capsid-to-tail proteins and tail assembly cassette of Bcep176 demonstrated significant modular mosaicism to homologs in lambdoid phages phiE125 and phi1026b – phages involved in the study of bacterial bioweapons (13, 26). Bglu421 exhibited modular mosaicism in tail assembly cassette and putative morons to homolog counterparts in a previously unannotated prophage of Burkholderia pseudomallei Pasteur - causative agent of melioidosis in a variety of animals (12). Further analysis of both phages indicates siphophage morphology and lambda-like proteins in Bcep176 and a putative pathogenicity factor in Bglu421. The importance of genomic sequencing and analysis of bacteriophages lies in their role of influencing the pathogenicity of their host (5), and their potential for use as cures of bacterial disease (1). URI: http://handle.tamu.edu/1969.1/3654 Files in this item: 1
Linet-URSThesisFINAL06.pdf (6.741Mb) -
Skinner, Allison C. (September 17, 2007)[more][less]
Abstract: Offatts Bayou is an embayment in the Galveston Bay complex on the upper Texas coast. The bayou is approximately 4.8 km long with a maximum width of 1 km, and an average depth of approximately 5 m. A small created lake (Lake Madeline) is connected to Offatts Bayou by a short, narrow channel. Together, Lake Madeline and Offatts Bayou (LMOB) are an important nursery and habitat for many finfish, shellfish, birds and other fauna and flora. The low mixing environment of LMOB, due to its relatively deep basin and small mouth, make it an ideal study area for understanding the significance of phytoplankton blooms and hypoxia as the causal factors of the near annual fish kills in these systems. Physical, chemical and biological parameters were measured at up to 17 stations distributed across LMOB, twice weekly over the course of two summers. Low winds, little rain and a highly stratified water column isolated a phytoplankton bloom to the upper pycnocline in the late summer of 2005. Phytoplankton concentrations in Lake Madeline (246.89 μg/L) were 4 times higher than those in Offatts Bayou (58.69 μg/L). The dominate phytoplankton species was an as yet, unidentified spherical cyanobacterium. The fish kill in August 2005 was associated with the decay of this bloom. Gulf menhaden (Brevoortia patronus) was the only fish species killed. Higher winds and more rain in the summer of 2006 resulted in a generally well mixed and oxygenated water column. Phytoplankton concentrations were low (13.22 μg/L) throughout the summer and a fish kill was not observed. The findings of this study supported the hypothesis that phytoplankton, either directly through harmful algal blooms/large quantities of biomass, or indirectly through low dissolved oxygen concentrations, are the primary causative factor of the fish kills occurring during the late summer months in LMOB. This study was unique in several respects: (1) two summers of physical, chemical and biological data were collected on fine spatial and temporal scales, (2) the phytoplankton community was identified to genus level revealing the identity of the bloom forming species, and (3) the cause of the fish kill could be clearly defined. URI: http://handle.tamu.edu/1969.1/5730 Files in this item: 1
Skinner_Thesis_Final.pdf (1.926Mb) -
Ragland, R. Blake (June 9, 2009)[more][less]
Abstract: Capacitive transducers are used to measure mechanical stress in the windings of superconducting magnets. The transducer consists of a bonded laminate of alternating thin foils of stainless steel and high-strength polymer (polyimide). The thin, flat package is ideal for measuring the accumulation of Lorentz stress that develops in the windings when current is passed through the coil to generate magnetic field. All groups who have used these transducers have experienced problems with failure of the gauges during operation. The Texas A&M group is endeavoring to determine the causes of the failures and remedy them so that we can continue to use the transducers in our next model dipole. During the construction of the previous model dipole, called TAMU II, there were transducer failures at very high ramp rates. From the raw measurements many insightful observations can be made including stress magnitudes, distributions, and magnetic field variance as a function of those stresses. My goal is to improve upon current methods of transducer fabrication to yield more consistent response, more robust reliability, and provisions for other possible uses. I will also develop a new method for reducing error in calibration. A key element of my approach will be to develop fixtures for the fabrication that can produce more reliable bonding between the metal and polymer layers within the transducer. After some investigation into the causes of variability of these transducers, it was found that the more rigid construction methods did not alleviate many problems. The main success of the new construction method was a decreased failure rate. Calibration, however, was quite successful. Evidence from the data taken in this project points toward a converging value of weighted capacitance. Though the offsets to capacitance due to a heating cycle may be unpredictable, convergence of weighted capacitance values over several heat cycles can certainly reduce error in model magnet stress measurements. URI: http://handle.tamu.edu/1969.1/86508 Files in this item: 1
Ragland_Approved_Thesis.pdf (620.8Kb) -
Barrett, Gemma (June 9, 2009)[more][less]
Abstract: Wave-scale changes in beach elevation were measured using a cross-shore array of ultrasonic distance sensors on a dissipative beach at Matagorda Peninsula, Texas, in December 2008. The data collected in this study are compared to data collected in a companion study on an intermediate beach in Pensacola, Florida in June 2008. Both beaches are currently in a state of recovery from hurricane activity within the last 5 years, and therefore serve as good comparison sites for bed elevation change models. At both sites, the ultrasonic distance sensors were used to measure the bed elevation changes to 0.08 m which is smaller than the median grain size at both study sites (0.2 mm and 0.3 mm respectively). The dissipative Matagorda site was found to be less affected by swash over the study period and maintained a steady state bed elevation with max change of .01 m. In comparison, the intermediate, Pensacola site was more affected by the swash and varied by 0.14 m in its bed elevation over a tidal cycle. It is argued that iv intermediate beaches are more affected by individual swash, while dissipative beaches are more affected overtime by the migration of bedforms rather than individual swash. URI: http://handle.tamu.edu/1969.1/86495 Files in this item: 1
Barrett_Approved_Thesis.pdf.pdf (1.575Mb) -
Baird, Hilary (September 17, 2007)[more][less]
Abstract: Tuberculosis is the world’s leading cause of death by infectious disease. Antibiotic resistance and HIV co-infection is increasing at an alarming rate. Mycosins-1-5 are subtilisin-like serine proteases within the periplasmic space of the tuberculosis bacterial cell. However, to date, Mycosin-1 is thought to be the most interesting because it is only expressed after TB infection and is thought to be essential to its virulence. The role of Mycosins-2-4 is not yet known. These factors make Mycosin-1 a novel drug target. This study aims to clone and characterize Mycosin-1 for further investigation as a drug target. The mycosin-1 and mycosin-2 genes were successfully cloned for later use in expression studies. Mycosin-2 has been included in the cloning process because of the conservation of the Mycosins’ active sites. The most potent inhibitor will be able to bind all five Mycosins. Several sequence alignments have also been included to help characterize the Mycosin-1 protein. The evidence suggests that Mycosin-1 is a typical subtilisin-like protease, allowing the characterization of the protein. A homology model has been built to gain further insight into the protein and for later use in virtual inhibitor screening. URI: http://handle.tamu.edu/1969.1/5723 Files in this item: 1
Baird Final Thesis.pdf (2.671Mb) -
Lancaster, Denise (September 17, 2007)[more][less]
Abstract: We are interested in determining the effects of subterranean termite soldier ratios on the overall cellulose consumption of Coptotermes formosanus and Reticulitermes flavipes. In nature, Coptotermes formosanus is found in very large colonies and a higher soldier ratio than Reticulitermes flavipes. In this project, each test colony was established at a specific size and soldier ratio. The soldier ratios tested for Coptotermes formosanus were 0:100, 5:100, 10:100, and 15:100, and the ratios tested for Reticulitermes flavipes were 0:100, 3:100, 5:100, and 10:100. These ratios were selected based on the research of other scientists. Since each species is specially adapted to different environments, these studies were carried out within their optimum temperature and humidity conditions. The Reticulitermes flavipes test colonies were kept inside of a plastic container at 27 ± 2 ºC, and relative humidity of 40 – 60%. The Coptotermes formosanus test colonies were kept at 30 ± 2 ºC and 80% relative humidity. The cellulose consumption results of this project are reported as g/h, and within each species and soldier ratio there are no significant differences. Because of this, the cellulose consumption values per species could be combined and compared on the species level. In analyzing the data this way, the C. formosanus test colonies consumed a significantly larger amount of cellulose per hour compared to R. flavipes. URI: http://handle.tamu.edu/1969.1/5724 Files in this item: 1
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Shockley, Ross (July 11, 2006)[more][less]
Abstract: The retinas of birds and other vertebrates undergo morphological and physiological changes throughout the day, which help regulate daily changes in visual sensitivity. One particular change is the contraction and elongation of photoreceptor outer segments, which is regulated by an endogenous circadian clock. Normally, Blackcaps (Sylvia atricapilla) are diurnal, but they migrate at night. In the current experiment, outer segment lengths of migrating and non-migrating Blackcaps were measured throughout the day and analyzed, and they show a trend toward circadian rhythmicity across the day. There also appears to be an advance in the phase of the rhythm in retinomotor movements when birds are migrating. These results indicate that circadian-controlled retinomotor movements could be modifications within the retina to accommodate the nocturnal lifestyle of migratory Blackcaps. We hypothesize that a change in retinal physiology and morphology may allow the formation of a migratory “night-vision” to accommodate the migrating Blackcap’s nocturnal lifestyle. URI: http://handle.tamu.edu/1969.1/3659 Files in this item: 1
ThesisFINALDRAFT.pdf (186.8Kb) -
Mai, Stefan (June 9, 2009)[more][less]
Abstract: As miniaturization of computer components is approaching the limits of physics, researchers in computer architecture are looking for less conventional means to perpetuate Moore's law. Recent trends in hardware ve been adding more cores. Consequently multicore machines are now commodity. To help programmers benefit from Moore's dividend, researchers in programming techniques, tools and languages have been exploring several venues. A dominant theme is the design and implementation of parallel algorithms. Several programming models have been proposed, but none at the moment seem to be substantially better than others. While general parallel programming is a distinctively challenging task, we believe that scientific computation algorithms display algebraic structures, thanks to the rich mathematical objects they manipulate. The present work aims at exploring the extent to which algebraic properties displayed by computer algebra algorithms may be automatically exploited to take advantage of parallelism in the OpenAxiom scientific computation platform. We designed a runtime system that exploits the ubiquitous parallelism of modern CPUs; the system is also scaled to many-system clusters. By taking advantage of the existing InputForm domain in OpenAxiom and connecting of the standard input channel to sockets, we were able to minimize potentially hazardous modifications to the OpenAxiom source while still implementing desired functionality. Additionally, we designed and implemented FFI extensions to the OpenAxiom core to take advantage of SIMD instructions, particularly SSE2 (SIMD Streaming Extensions). The extension allowed us to nearly double the speed of common operations such as multiplying arrays of doubles. We also defined and implemented a foreign function interface for the OpenAxiom system. All of these additions were benchmarked using Berlekamp's algorithm for factorization of polynomials over integers. While much still remains to be done in parallelizing the algebra to work over many calculation nodes, mathematical annotations remain viable in unloading the burden of parallelizing code from the programmer by substituting a simpler activity. URI: http://handle.tamu.edu/1969.1/86499 Files in this item: 1
thesis.pdf (157.7Kb)
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