Browsing by Subject "Temperature"

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Austin climate data
(2009-10) Ward, Natalie
An overview of the climate conditions that impact on the energy efficiency of construction projects in Austin, Texas. Data is presented on various factors, including temperature, precipitation, daylight, and wind.
Effect of temperature, dissolved inorganic carbon and light intensity on the growth rates of two microalgae species in monocultures and co-cultures
(2014-05) Almada-Calvo, Fernando; Kinney, Kerry A.; Katz, Lynn E.
The enormous biodiversity of microalgae as well as their high photosynthetic rates can be exploited for a wide variety of applications including the production of high value chemicals, nutraceuticals, aquaculture feed, and most recently, biofuels. Regardless of the application, the productivity of the microalgae culture must be optimized in order to make the systems economically feasible. One environmental factor that greatly affects the productivity of mass cultivation systems is temperature since it can be prohibitively expensive to control in outdoor systems. Temperature affects microalgae growth rates both directly by its effect on metabolic rates, and indirectly, by changing the bioavailability of the inorganic carbon present in solution. In the first part of this research, the effects of dissolved inorganic carbon (DIC) concentration (varied by sparging CO₂-enriched air) and temperature on the growth of a model microalga species (Nannochloris sp., UTEX LB1999) were investigated in a turbidostat bioreactor. The results indicate that increasing DIC concentration yields higher microalgae growth rates up to an optimum value (around 3 mM for Nannochloris sp.) but higher concentrations actually inhibited growth. Since increasing the temperature decreases the DIC concentration for a given gas pCO₂, it is necessary to adjust the pCO₂ to maintain the target DIC concentration in the optimal range for growth. In the next phase of the research, the effect of average light intensity (Gav) and temperature on the growth rate of two microalgae species (Nannochloris sp., UTEX1999. and Phaeodactylum tricornutum, UTEX646) was investigated. Growth rates were measured over a range of average light intensities and temperatures using a turbidostat bioreactor. A multiplicative model was developed to describe growth as a function of both average light intensity and temperature. In the third phase of this research, both microalgae species were grown together to explore the effects of temperature fluctuations on the population dynamics of the co-culture. It was observed that Nannochloris was inhibited by the presence of P. tricornutum in the medium, probably due to the excretion of secondary metabolites into the medium that affected Nannochloris growth (allelopathic effects). The temperature and average light intensity model developed under monoculture conditions was modified to incorporate the allelopathic effects observed. The resulting model provided a reasonable fit to the dynamic behavior of a Nannochloris/P. tricornutum co-culture subjected to temperature variations in chemostat experiments.
Effects of auditory and thermal stimuli on 3,4- methylenedioxymethamphetamine (MDMA)-induced neurochemical and behavioral responses
(2009-12) Feduccia, Allison Anne; Duvauchelle, Christine L.
The amphetamine derivative, 3,4-methylenedioxymethamphetamine (MDMA), is a popular drug often taken by young adults at dance clubs or rave parties. Laser light shows, fast-paced electronic music, and hot crowded dance floors are characteristic of these events, and Ecstasy users report that the acute effects of the drug are potentiated by these stimulatory conditions. However, it remains largely unknown how environmental stimuli impact the neurochemical and physiological effects of MDMA. The aim of the first study presented in this dissertation was to investigate how auditory stimuli (music, white noise, and no additional sound) influence MDMA conditioned place preference (CPP), self-administration, and nucleus accumbens (NAcc) dopamine (DA) and serotonin (5-HT) responses. Findings revealed a significant CPP for animals exposed to white noise during MDMA conditioning trials. After self-administration of MDMA (1.5 mg/kg), NAcc DA and 5-HT were highest in rats exposed to music during the test session. The second study aimed to investigate the effects of ambient temperature (23°or 32°C) on long-term MDMA self-administration and neurochemical responses. Results indicated no difference in self-administration or locomotor activity rates for the high versus room temperature groups across sessions. However, MDMA (3.0 mg/kg) administered in high ambient temperature resulted in significantly greater NAcc serotonin release compared to when taken at room temperature, but no differences in dopamine response was determined between the two conditions. Overall, these results indicate that auditory and thermal stimuli can effect MDMA-induced behavioral and neurochemical responses. The last aim tested a novel apparatus and method for use in animal models of drug reinforcement. By combining traditional CPP and self-administration procedures, this approach provided more informative data and circumvented some inherent drawbacks of each method alone. In addition to confirming the ability to produce drug conditioned place preferences after short- and long-term experiments, the long-term version of the procedure revealed a significant positive relationship between lever response rate and CPP magnitude. Therefore, this experimental design can be used to identify subgroups of rats that may vary in sensitivity to drug motivational effects. Further study of these populations may be useful in the development of behavioral and pharmacological therapies for drug addiction.
Effects of elevated temperature on the physical aging and gas transport of sub-micron polybenzimidazole gas separation membranes
(2020-07-16) Merrick, Melanie Mae; Freeman, B. D. (Benny D.); Paul, Donald R; Sanchez, Isaac C; Riffle, Judy S; Lynd, Nathaniel A
The promising potential of polybenzimidazole (PBI) membranes for high temperature (~200 °C), hydrogen-selective gas separations has been reported for many membrane geometries (e.g., bulk, composite, and hollow fiber), but never for sub-micron, spin-cast membranes. Numerous studies have shown that the performance of spin-cast membranes, which simulate commercially relevant thicknesses, declines more quickly with time than that of thick membranes due to accelerated physical aging. However, because most existing membranes are used near ambient temperature, the physical aging of sub-micron, spin-cast membranes has never been studied at temperatures above 55 °C. Because physical aging is dependent on both thickness and temperature, emerging high temperature membrane applications make it both intellectually and practically imperative to characterize spin-cast membranes in this new temperature regime. For the first time, physical aging studies of spin-cast, sub-micron membranes have been extended to elevated temperatures. PBI membranes, cast from commercial-grade Celazole®, were aged in a high-temperature permeation system while the gas permeabilities were periodically measured over more than 1500 hours. When aging at 190 °C, membrane gas permeabilities decreased rapidly then plateaued after 300 hours of aging. The observation of a plateau (i.e., equilibration) had never before been seen for a membrane, nor, to our knowledge, for any polymer ~250 °C below its glass transition temperature. Decreases in membrane permeability were accompanied by increases in selectivity for H₂, which are traditionally represented by Robeson upper bound plots. These shifts were consistent with previous membrane physical aging studies and indicate membrane size-sieving ability improves with aging. Celazole®’s permeability reductions at lower aging temperatures (e.g., 175 °C) were qualitatively similar to those at 190 °C, but occurred over a longer time period. When graphed vs. the logarithm of aging time, the permeability reductions at various temperatures could be superimposed via time-temperature superposition, which is a hallmark of physical aging. A thorough review of physical aging studies in the polymer physics literature is presented to give context for this unexpectedly short equilibration time far below the glass transition. Comparisons are then made between the current study and previous aging studies in the polymer physics field. Overall, the observation of a plateau at short aging times for a polymer deep in the glassy state casts doubt on our understanding of physical aging’s temperature-dependence and our ability to predict membranes’ long-term stability in elevated temperature applications.
Improved accelerated life testing for cathodic delamination
(2012-03) Liechti, K. M.
The overall objective of this work is to establish the feasibility of modeling the cathodic delamination problem in polymer coated submarine components with a view to developing a more accurate testing standard for Accelerated Life Testing (ALT) and to determining the effectiveness of new approaches for combating cathodic delamination in a quantitative manner ... An approach has ... been taken to characterize cathodically delaminating rubber/metal interfaces and forms the basis for the current attempt to model cathodic delamination between polyurethane and titanium. Once this model is established it will allow for an accelerated life protocol to be developed where stress and temperature will be used to accelerate crack growth in laboratory specimens while retaining the same crack growth mechanisms that are seen in service. The elements of the approach are threefold: 1. Determining the mechanical behavior of the polyurethane and titanium. The former is more challenging due to its nonlinearly elastic behavior. 2. Conducting a stress analysis of the specimen to be used in the cathodic delamination experiment in order to design it to provide the anticipated range of energy release rate values. 3. Conducting the cathodic delamination experiments and determining the crack velocity profiles for the polyurethane/titanium interface as a function of energy release rate and temperature.
The influence of temperature on the fate and transport of phthlates in indoor environments
(2014-05) Bi, Chenyang; Xu, Ying (Assistant professor)
Phthalate esters are extensively used as plasticizers in building materials and consumer products, but are associated with serious health concerns. They are ubiquitous indoors, redistributing from their original source to all interior surfaces, including airborne particles, dust, and skin. The main objective of the research is to investigate the influence of temperature on the fate and transport of phthalates in indoor environments. In this study, the concentrations of benzyl butyl phthalate (BBzP) and di-2-ethylhexyl phthalate (DEHP) in indoor air, settled dust, and on different interior surfaces including mirror, glass, plate, cloth and wood were measured periodically in a test house. The measurements were conducted at temperatures of 21°C and 30°C, respectively. In addition, sorption kinetics was also monitored at the temperature of 21°C. The air concentrations of BBzP and DEHP at 21°C range from 141 ng/m₃ to 210 ng/m₃ and 66 ng/ m₃ to 100 ng/ m₃, respectively. For impervious surfaces such as dish plates, the surface concentrations reached steady-state concentrations in less than 24 hours, to the level between 2 and 8 [mu]g/m₂ for both BBzP and DEHP. In contrast, the time to reach steady state was much longer for porous surfaces such as hardwood (>1 week) and dust (> months). With the temperature increase to 30°C, the gas phase concentrations of BBzP and DEHP increased by about five times, and the surface concentrations on various surfaces also increased correspondingly. This investigation suggests that temperature has an important influence on the fate and transport of phthalates in indoor environments.
Intra-meander groundwater-surface water interactions in a losing experimental stream
(2010-08) Nowinski, John David; Cardenas, Meinhard Bayani, 1977-; Sharp, John M.; Bennett, Philip C.
Groundwater-surface water interactions between streams and shallow alluvial aquifers can significantly affect their thermal and chemical regimes and thus are critical for effective management of water resources and riparian ecosystems. Of particular significance is the hyporheic zone, an area delineated by subsurface flow paths that begin and end in surface water bodies. Although detailed work has examined hyporheic flow in the vertical dimension, some studies have suggested that the drop in a stream’s elevation as it flows downstream can laterally extend the hyporheic zone. This study examines intra-meander hyporheic flow using extensive field measurements in a full-scale experimental stream-aquifer system. Synoptic head measurements from 2008 and 2009 and a lithium tracer test were conducted to determine the extent and nature of hyporheic flow within the meander. Permeability was measured and sediment cores were analyzed from 2008 to 2009 to assess aquifer properties. Finally, transient head and temperature measurements were collected during flooding events to assess the sensitivity of intra-meander hyporheic flow and temperature to stream discharge. Results verify that hyporheic flow through meanders occurs, but show that it is sensitive to whether a stream is gaining or losing water to the subsurface overall. In addition, permeability and core grain size results indicate moderate heterogeneity in permeability can occur in aquifers composed of relatively uniform sediment. Results also demonstrate that permeability in alluvial aquifers can evolve through time. Such evolution may be driven by groundwater flow, which transports fine particles from areas where porosity and permeability are relatively high and deposits them where they are relatively low, thus creating a positive feedback loop. Finally, measurements during flooding indicate that steady-state hyporheic flow and the thermal regime within the aquifer are largely insensitive to stream discharge. Together, these results expand upon previous field studies of intra-meander hyporheic flow and verify previous modeling work, although they demonstrate a level of complexity within these systems that should be considered in future work.
Nitrate removal efficiency in hyporheic zones : the effect of temperature and bedform dynamics
(2017-08) Zheng, Lizhi; Cardenas, Meinhard Bayani; Bennett, Philip C; Mohrig, David; Werth, Charles J.; Moffett, Kevan B.
Fundamental understanding of bedform-induced hyporheic flow and how it controls the nitrate dynamics in the hyporheic zone (HZ) is critical for environmental and ecological problems, such as eutrophication, deterioration of water quality, and loss of biodiversity. The HZ is regarded as a biogeochemical hotspot for removing nitrate from the river system. Although hyporheic flux has been extensively studied in the HZ in the last decade, the cycle of nitrate dynamics in the HZ is still poorly understood. To better characterize and predict nitrate cycling in the HZ, I have investigated the role of HZ in removing nitrate in response to temperature variations and bedform migration through numerical experiments. I have designed and generated all bedform shapes for this dissertation. All numerical experiments followed the same sequential procedures: (1) Solving Reynolds-averaged Navier-Stokes equations to obtain pressure distribution along the sediment-water interface; (2) The bedform-induced pressure along sediment-water interface drives water entering into and out of HZ by solving the Darcy’s equation; (3) Meanwhile, the transport equations were implemented for solving reactive species and/or temperature distributions, depending on whether temperature was assumed to be spatially heterogeneous or homogeneous. The reactive species were either consumed or produced that was closely related to the reaction chains for the nitrate transformations in the HZ. Here, we only considered aerobic respiration, denitrification, and nitrification for nitrate cycling in the HZ. My dissertation started with the simplest cases assuming uniform temperature in the HZ. I found that nitrate transformations in the HZ are temperature-dependent since the chemical reaction rates increase with enlarging temperature. The functionality of HZ acting as nitrate source or sink depends strongly on the stream water quality. When the HZ serves as nitrate sink, the nitrate removal efficiency increases with temperature. Moreover, since temperature changes diurnally following a sinusoidal function, a persistent biogeochemical hotspot for removing nitrate is present regardless of the occurrence of dynamic and complex hyporheic temperature patterns. The daily-averaged nitrate removal efficiency with instantaneously changing temperature is fairly identical to the counterpart by using uniform temperature in the HZ. Last but not least, I generated more realistic moving ripple bedforms. The migration rate of ripples causes different hyporheic flux and thus reactive transport processes in the HZ. I found that the nitrate removal efficiency increases asymptotically with Damkohler number, and the immobile ripples overestimate the nitrate removal efficiency compared to that for mobile ripples. All above-mentioned research results can be readily extended for large scales.
Novel methods of characterizing phthalate emissions and their fate and transport in residential indoor environments
(2014-12) Liang, Yirui; Xu, Ying (Assistant professor)
Phthalates have been used pervasively as plasticizers in consumer products and building materials. These semi-volatile organic compounds (SVOCs) are ubiquitous in indoor environments, redistributing from their original sources to indoor air, and subsequently to all interior surfaces. Because they partition strongly to surfaces, most phthalates persist for years after the source is removed. Biomonitoring data based on blood and urine testing provide direct evidence of the universal and significant human exposure to phthalates, which may result in serious adverse health effects. However, effective strategies to limit exposures to phthalates remain hamstrung by our poor understanding of their sources and fate and transport in indoor environments. The goal of this research is to explicitly elucidate the fundamental mechanisms governing emission, transport, and human exposure associated with phthalates in indoor environments. The specific research objectives are to 1) develop a novel, rapid, small-chamber method to determine the key parameters that control phthalate emissions and characterize the emissions; 2) investigate the influences of temperature, air flow rate, and surface sorption on phthalate emissions via a series of controlled tests in small and large chambers; 3) develop and validate a new indoor fate and transport model for phthalates with consideration of particle dynamics and its effects on emission and sorption. This research, which connects emission measurements to chemical transport and exposure assessment, will explicitly elucidate the fundamental mechanisms governing emission, transport, and human exposure associated with phthalates in indoor environments.
Optical characterization of emerging electronic and ferroelectric materials and structures
(2019-04-05) Cho, Yujin; Downer, Michael Coffin; Demkov, Alexander A.; Lai, Keji; Zhou, Jianshi; Sitz, Greg O.
My Ph. D. work is on altering material properties to improve or apply in device applications and probing the manipulated properties through linear/ nonlinear optical methods. I focused my study on three types of structural modifications. First, in Chapter 2, I applied strain on a 3D integrated silicon circuit structure and BaTiO₃ thin film. Silicon, well-understood bulk material and most popular semiconductor platform, acquires new electronic and optical properties under strain. In addition, one can significantly control the ferroelectric and electro-optic properties of BaTiO₃ thin film, a traditional perovskite ferroelectric, by applying strain via a piezoelectric substrate, as shown in Chapter 5. Second, I engineered well-characterized bulk materials into thin films, as thin as 1 nm. In Chapter 4, I measured retention time of ferroelectric polarization on BaTiO₃ film thicknesses in the range of 10-20 nm. In addition, the thickness of the layers of a 2D material, e.g. In₂Se₃, introduces variations in bandgaps, dielectric functions, and/or absorption, which will be shown in Chapter 6. Lastly, I characterized the displacive and disorder-to-order transitions in ferroelectric materials. For example, in Chapter 3, we discovered order-disorder ferroelectric mechanism in double perovskites synthesized by Spark-plasma-sintering method and studied their Curie temperatures. Through these projects, I discovered new ways of controlling material properties and studied their underlying origins of the emerging phenomena using optical methods
Power-aware processor system design
(2020-05) Kalyanam, Vijay Kiran; Abraham, Jacob A.; Orshansky , Michael; Pan, David; Touba, Nur; Tupuri, Raghuram
With everyday advances in technology and low-cost economics, processor systems are moving towards split grid shared power delivery networks (PDNs) while providing increased functionality and higher performance capabilities resulting in increased power consumption. Split grid refers to dividing up the power grid resources among various homogeneous and heterogeneous functional modules and processors. When the PDN is shared and common across multiple processors and function blocks, it is called a Shared PDN. In order to keep the power in control on a split-grid shared PDN, the processor system is required to operate when various hardware modules interact with each other while the supply voltage (V [subscript DD]) and clock frequency (F [subscript CLK]) are scaled. Software or hardware assisted power-collapse and low-power retention modes can be automatically engaged in the processor system. The processor system should also operate at maximum performance under power constraints while consuming the full thermal design power (TDP). The processor system should neither violate board and card current limits nor the power management integrated circuit (PMIC) limits or its slew rate requirements for current draw on the shared PDN. It is expected to operate within thermal limits below an operating temperature. The processor system is also required to detect and mitigate current violations within microseconds and temperature violations in milliseconds. The processor system is expected to be robust and should be able to tolerate voltage droops. Its importance is highlighted with the processor system being on shared PDN. Because of the sharing of the PDN, the voltage droop mitigation scheme is expected to be quick and must suppress V [subscript DD] droop propagation at the source while only introducing negligible performance penalties during this mitigation. Without a solution for V [subscript DD] droop in place, the entire V [subscript DD] of shared PDN is forced to be at a higher voltage, increasing overall system power. This can potentially affect the days of use (DoU) of battery-operated systems, and reliability and cooling of wired systems. A multi-threaded processor system is expected to monitor the current, power and voltage violations and react quickly without affecting the performance of its hardware threads while maintaining quality of service (QoS). Early high-level power estimates are a necessity to project how much power will be consumed by a future processor system. These power projections are used to plan for software use cases and to reassign power-domains of processors and function blocks belonging to the shared PDN. Additionally, it helps to re-design boards and power-cards, re-implement the PDN, change PMIC and plan for additional power, current, voltage and temperature violation related mitigation schemes if the existing solutions are insufficient. The split grid shared PDN that is implemented in a system-on-chip (SoC) is driven by low cost electronics and forces multiple voltage rails for a better energy efficiency. To support this, there is a need for incorporation of voltage levels and power-states into a processor behavioral register transfer level (RTL) model. Low power verification is a must in a split-grid PDN. To facilitate these, the RTL is annotated with voltage supplies and isolation circuits that engage and protect during power collapse scenarios across various voltage domains. The power-aware RTL design is verified, identified and corrected for low power circuit and RTL bugs prior to tape-out. The mandatory features to limit current, power, voltage and temperatures in these high performance and power hungry processor systems introduce a need to provide high level power projections for a processor system accounting for various split-grid PDN supplying V [subscript DD] to the processor, the interface bus, various function blocks, and co-processors. To solve this problem, a power prediction solution is provided that has an average-power error of 8% in prediction and works with reasonable accuracy by tracking instantaneous power for unknown software application traces. The compute time to calculate power using the generated prediction model is 100000X faster and uses 100X less compute memory compared to a commercial electronic design automation (EDA) RTL power tool. This solution is also applied to generate a digital power meter (DPM) in hardware for real-time power estimates while the processor is operational. These high-level power estimates project the potential peak-currents in these processor systems. This resulted in a need for new tests to be created and validated on silicon in order to functionally stress the split-grid shared PDN for extreme voltage droop and sustained high current usage scenarios. For this reason, functional test sequences are created for high power and voltage stress testing of multi-threaded processors. The PDN is a complex system and needs different functional test sequences to generate various kinds of high and low power instruction packets that can stress it. These voltage droop stress tests affect V [subscript MIN] margins in various voltage and frequency modes of operation in a commercial multi-threaded processor. These results underscore a need for voltage mitigation solutions. The processor system operating on a split grid shared PDN can have its V [subscript MIN] increased due to voltage stress tests or a power-virus software application. The shared PDN imposes requirements to mitigate the voltage noise at the source and avoid any possibility of increases to the shared PDN V [subscript DD]. This necessitates implementing a proactive system that can mitigate voltage droop before it occurs while lowering the processor’s minimum voltage of operation (V [subscript MIN]) to help in system power reduction. To mitigate the voltage droops, a proactive clock gating system (PCGS) is implemented with a voltage clock gate (VCG) circuit that uses a digital power meter (DPM) and a model of a PDN to predict the voltage droop before its occurrence. Silicon results show PCGS achieves 10% higher clock frequency (F [subscript CLK]) and 5% lower supply voltage (V [subscript DD]) in a 7nm processor. Questions arise about the effectiveness of PCGS over a reactive voltage droop mitigation scheme in the context of a shared PDN. This results in analysis of PCGS and its comparison against a reactive voltage droop mitigation scheme. This work shows the importance of voltage droop mitigation reaction time for a split grid shared PDN and highlights benefits of PCGS in its ability to provide better V [subscript MIN] of the entire split grid shared PDN. The silicon results from power-stress tests shows the possibility of the high-power processor system exceeding board or power-supply card current capacity and thermal violations. This requires designing a limiting system that can adapt processor performance. This limiting system is expected to meet the stringent system latency of 1 µs for sustained peak-current violations and react in the order of milli-seconds for thermal mitigation. It is also expected of this system to maintain the desired Quality of Service (QoS) of the multi-threaded processor. This results in implementation of a current and temperature limiting response circuit in a 7nm commercial processor. The randomized pulse modulation (RPM) circuit adapts processor performance and reduces current violations in the system within 1 µs and maintains thread fairness with a 0.4% performance resolution across a wide range of operation from 100% to 0.4%. Hard requirements from SoC software and hardware require the processor systems to be within the TDP and power budgets and processors sharing the split gird PDN. Power consumed by the threads (processors) are now exceeded by added functionality of new threads (processors), which could consume much higher power compared to power of previous generation processors. The threads (processors) operate cohesively in a multi-threaded processor system and though there is a large difference in magnitude of power profiles across threads (processors), the overall performance of the multi-threaded processor is not expected to be compromised. This enforces a need for a power limiting system that can specifically slow down the high-power threads (processors) to meet power-budgets and not affect performance of low-power threads. For this reason, a thread specific multi-thread power limiting (MTPL) mechanism is designed that monitors the processor power consumption using the per thread DPM (PTDPM). Implemented in 7nm for a commercial processor, silicon results demonstrate that the thread specific MTPL does not affect the performance of low power threads during power limiting until the current (power) is limited to very low values. For high power threads and during higher current (power) limiting scenarios, the thread specific MTPL shows similar performance to a conventional global limiting mechanism. Thus, the thread specific MTPL enables the multi-threaded processor system to operate at a higher overall performance compared to a conventional global mechanism across most of the power budget range. For the same power budget, the processor performance can be up to 25% higher using the thread specific MPTL compared to using a global power limiting scheme. In summary, in this dissertation design for power concepts are presented for a processor system on a split-grid shared PDN through various solutions that address challenges in high-power processors and help alleviate potential problems. These solutions range from embedding power-intent, to incorporating voltage droop prediction intelligence through power usage estimation, maintaining quality of service within a stringent system latency, to slowing down specific high-power threads of a multi-threaded processor. All these methods can work cohesively to incorporate power-awareness in the processor systems, making the processors energy efficient and operate reliably within the TDP.
Sex determination in southern flounder, Paralichthys lethostigma from the Texas Gulf Coast and implications of climate change
(2010-12) Montalvo, Avier José; Holt, J. (Joan); McClelland, James W.; Walther, Benjamin D.
In marine flatfish of the genus Paralichthys, temperature plays a large role in sex determination. Thus, global climate change could have significant effects on southern flounder (Paralichthys lethostigma), a commercially and recreationally important flatfish whose populations have steadily declined in Texas in the last 25 years. The most susceptible areas to global climate change are shallow water environments, particularly estuaries, which serve as essential nursery habitats for juvenile southern flounder. While in the estuaries, juveniles develop, and sex is determined. Juvenile southern flounder possess genotypic sex determination; however, the sex of females is highly influenced by temperature and can result in sex reversal. The temperature-sensitive enzyme complex responsible for estrogen biosynthesis in vertebrates is aromatase cytochrome P450 (P450arom), a critical component in ovarian differentiation that can be used to measure presumptive males and females exposed to a gradient of temperatures. This research identifies that sex is influenced by temperature between 35 and 65 mm total length (TL) and establishes that increases in temperature from 18 °C during this size range produce increasingly male skewed sex ratios in southern flounder from Texas. The findings presented here are critical for optimizing production of females in culture and for developing stock enhancement programs of southern flounder in Texas.
Spectroscopic measurement of n[subscript e] and T[subscript e] profiles using atomic and kinetic models for Argon in the Texas Helimak
(2013-05) Dodd, Kenneth Carter; Gentle, Kenneth W.
Profiles for electron density and temperature were determined in a self-consistent way using line emission spectroscopy and collisional radiative models for neutral and singly ionized Argon (Ar I and Ar II) in the Texas Helimak. Neutral Argon density profiles were calculated using a kinetic gas model. Electron-impact excitation and Ionization rates were corrected to account for the electron velocity distribution deviating slightly from a true Maxwellian distribution due to inelastic electron-neutral collisions. Results show an electron temperature which roughly agrees with probe diagnostics. This method gives an electron density that is about twice as high, which may be possible from a power balance perspective.
Standards of human comfort: relative and absolute
(2009-10) Fincher, Warren; Boduch, Michael
An examination of the factors that affect the quality of comfort in an architectural environment, including temperature, lighting, humidity, and air quality. The paper also considers the variability of individual and cultural perceptions of comfort in determining how designers might create an optimal living or work space.
Temperature, stress, and strength development of early-age bridge deck concrete
(2011-08) Pesek, Phillip Wayne; Folliard, Kevin J.; Drimalas, Thanos
In bridge deck concrete, early-age cracking can lead to substantial serviceability and structural integrity issues over the lifespan of the bridge. An understanding of the temperature, stress, and strength development of concrete can aid determining the early-age cracking susceptibility. This project, funded by the Texas Department of Transportation, evaluated these properties for various bridge deck materials and mixture proportions. The research presented in this thesis involved a laboratory testing program that used a combination of semi-adiabatic calorimetry, rigid cracking frame, free shrinkage frame, and match cured cylinder testing program that allowed the research team to simulate the performance of common bridge deck mixture designs under hot and cold weather conditions. In this program, the semi-adiabatic calorimetry was used, with previously generated models, to generate the temperature profile of the mixture. The rigid cracking frame and free shrinkage frame were used to evaluate the restrained stress development and the unrestrained volume changes, respectively, under the simulated temperatures. The match-cure cylinder testing program allowed the research team to generate a strength development profile for the concrete mixtures under the various simulated temperature profiles. Results from the laboratory program revealed that in hot weather simulations, ground granulated blast furnace slag mixtures developed the lowest stress / strength ratios, and in cold weather simulations, Class F fly ash mixtures developed the lowest stress / strength ratios. In general, use of SCMs and limestone coarse aggregate results in mixtures that generate less heat and lower stress / strength ratios. Isothermal testing showed that shrinkage reducing admixtures were effective in reducing early-age strains from chemical shrinkage. In addition to the laboratory testing program, a field testing program was completed to measure the temperature development of four bridge decks during the winter and summer months. The recorded concrete temperatures and the effects of the environmental conditions at the time of the pour will aid in the calibration and validation of the temperature prediction component of ConcreteWorks for bridge deck construction. In addition, experience gained through these field pours resulted in an optimized instrumentation procedure that will aid in the successful collection of data in future projects.
The environmental influences on the growth and grazing of marine protists
(2020-12-03) Tang, Chi Hung; Buskey, Edward Joseph, 1952-; Erdner, Deana L; Liu, Zhanfei; Stoecker, Diane K
Marine protists are important components at the base of the marine food web. The growth and grazing of protistan organisms in response to the toxicity of petroleum hydrocarbons and elevated seawater temperature at the community and species levels were investigated. In exposure to 10 μL L⁻¹ of chemically dispersed crude oil in the mesocosms, the grazing impacts of microzooplankton (20-200 μm) on phytoplankton were reduced. While the microzooplankton grazing accounted for ~50% of the phytoplankton’ population growth in the control treatment, there was a de-coupling between these two parameters in the oil-loaded treatment. The de-coupling could potentially lead to algal blooms in the natural environment under certain conditions. In contrast, in exposure to chemically dispersed crude oil in the microcosms, the grazing impacts of nanoplankton (2-20 μm) on bacteria did not differ among the treatments of control and low (2 μL L⁻¹) and high (8 μL L⁻¹) concentrations. The tight couplings between the nanoplankton grazing and bacterial population growth in the control and oil-loaded treatments could have kept the abundance of bacterial cells steady. The community compositions of bacteria in the low and high dose crude oil treatments became increasing similar and different from those in the control treatment. It is believed to be related to the availability of carbon and inorganic nutrients. The relatively high abundance of hydrocarbon-degrading bacteria Cycloclasticus and Alcanivorax in the oil-loaded treatments indicated the presence of biodegradation. Exposure experiments were conducted to investigate the responses of marine protistan species to the toxicity of soluble petroleum hydrocarbon and elevated seawater temperature. In exposure to increasing concentrations of the water accommodated fraction (WAF) of crude oil, the heterotrophic dinoflagellates Oxyrrhis marina and Protoperidinium sp. and ciliates Euplotes sp. and Metacylis sp. showed species- specific vulnerabilities to oil toxicity, as reflected by their specific growth rates. When compared to the control treatment, their population grazing impacts and per capita ingestion rates were reduced with exposure to the WAF of crude oil alone and the mixture of crude oil and dispersant at the same concentration. In exposure to elevated seawater temperature, the Florida strain of mixotrophic dinoflagellate Fragilidium subglobosum obtained a specific growth rate of ~0.3 d⁻¹ at both 19°C and 23°C in mono-specific culture but zero or negative growth rates in cultures with added prey dinoflagellate Tripos tripos. F. subglobosum grown at 19°C showed higher maximum photosynthetic efficiency than at 23°C but did not differ in cellular chlorophyll-a content or cell size. This strain of F. subglobosum is believed to be non-mixotrophic and therefore the hypothesis that this dinoflagellate species becomes more heterotrophic at elevated temperature was not proved or disapproved
The study of multiple ion channel gating models and mechanisms
(2023-08) Yeh, Frank R.; Senning, Eric Nicolas, 1978- ; Aldrich, R. W. (Richard W.); Zakon, Harold; Pierce, Jon; Horrigan, Frank; Goldschen-Ohm, Marcel
Recent advancements in protein structural determination, structural predictions, structural modelling, and bioinformatics have significantly improved our understanding of ion channel gating models and mechanisms. Despite these improvements in technology, the transient and sporadic nature of multiple open and closed states in ion channels remains a challenge to study. These states are observable in electrophysiology studies but might be difficult to capture through structural determination techniques such as cryo-electron microscopy (cryo-EM) or may not appear as stable structures in prediction and modeling approaches. Bioinformatics are instrumental in generating hypotheses for further investigation. By examining functional and sequence differences across species or isoforms, these methods yield profound insights into ion channel gating mechanisms. Nevertheless, these hypotheses must be rigorously tested in functional studies. Hence, although ion channel research has seen huge advancements from these recent technological improvements, there is still no technique that can substitute electrophysiology experiments in the degree of functional information provided. To gain a strong understanding of ion channel gating models and mechanisms and the integration of knowledge provided by recent improved technological advances of, I chose to study thermoTRP channels, six-transmembrane voltage-gated or ligand-gated ion channels, as well as BK channels, the voltage- and calcium-gated potassium channels. Particularly, I have developed a theory for temperature-dependent gating in thermoTRP channels, generated hypotheses for voltage-gating mechanisms in six-transmembrane voltage-gated channels from sequence-based bioinformatics integrated with structural knowledge, and investigated BK’s voltage-gating mechanism by performing single-channel electrophysiology studies of BK based on hypotheses generated from the bioinformatics approach.
Thermal performance in mid/large buildings : in hot, humid climates
(2009-10) Galloway, Ross; Brown, Meredith
This paper presents on overview of several vernacular and passive strategies as an alternative to the standard HVAC system. It examines the performance demands of large buildings in Austin, Texas and addresses several potential methods for cooling and dehumidifying buildings, including: preventing solar heat gain, ventilation strategies, ground cooling, convection cooling, desiccant cooling, evaporative cooling, and use of multiple zones.
Wettability alteration in high temperature and high salinity carbonate reservoirs
(2011-08) Sharma, Gaurav, M.S. in Engineering; Mohanty, Kishore Kumar; Pope, Gary A.
The goal of this work is to change the wettability of a carbonate rock from oil wet-mixed-wet towards water-wet at high temperature and high salinity. Only simple surfactant systems (single surfactant, dual surfactants) in dilute concentration were tried for this purpose. It was thought that the change in wettability would help to recover more oil during secondary surfactant flood as compared to regular waterflood. Three types of surfactants, anionic, non-ionic and cationic surfactants in dilute concentrations (<0.2 wt%) were used. Initial surfactant screening was done on the basis of aqueous stability at these harsh conditions. Contact angle experiments on aged calcite plates were done to narrow down the list of surfactants and spontaneous imbibition experiments were conducted on field cores for promising surfactants. Secondary waterflooding was conducted in cores with and without the wettability altering surfactants. It was observed that barring a few surfactants, most were aqueous unstable by themselves at these harsh conditions. Dual surfactant systems, a mixture of a non-ionic and a cationic surfactant increased the aqueous stability of the non-ionic surfactants. One of the dual surfactant system, a mixture of Tergitol NP-10 and Dodecyl trimethyl ammonium bromide, proved very effective for wettability alteration and could recover 70-80% of OOIP during spontaneous imbibition. Secondary waterflooding with the wettability altering surfactant (without alkali or polymer) increased the oil recovery over the waterflooding without the surfactants (from 29% to 40% OOIP). Surfactant adsorption calculated during the coreflood showed an adsorption of 0.24 mg NP-10/gm of rock and 0.20 mg DTAB/gm of rock. A waterflood done after the surfactant flood revealed change in the relative permeability before and after the surfactant flood suggesting change in wettability towards water-wet.
Zero-stress temperature and Its implications for long-term performance of continuously reinforced concrete pavements
(2011-12) Yeon, Jung Heum, 1983-; Won, Mooncheol; Fowler, David W.; Folliard, Kevin J.; Juenger, Maria G.; Wheat, Harovel G.
Continuously reinforced concrete pavement (CRCP) is a portland cement concrete (PCC) pavement structure with a continuous longitudinal steel layout. CRCP is forming a major portion of PCC roadway systems in the state of Texas due to its low life cycle cost, ease of maintenance, and durable nature. While the overall performance of CRCP is proven to be excellent, some performance problems are still found as a form of distresses such as punchout and spalling. The current pavement design guide states that these distresses are closely related with the early-age behavior characteristics of CRCP, and various measures are underway to develop to improve the long-term performance of CRCP in terms of initial material design and use, structural design, and quality control. Understanding the current issues that pavement engineers and researchers face, the primary objective of this dissertation research focuses on sound understanding of the early-age structural behavior characteristics of CRCP and its effect on the long-term performance to provide reliable design and analysis criteria for CRCP. To achieve this main objective, characterizing the early-age structural response in CRCP was a core task of this study. For this purpose, a zero-stress temperature (ZST), one of the design and construction variables considered to have most significant effects on CRCP behavior and performance, was evaluated. As a beginning point of the entire framework, a series of field experiments were conducted in four new PCC pavement construction projects in the state of Texas to evaluate the actual structural response in early-age CRCP since a laboratory experiment would have a critical limitation in simulating the restraint conditions that exist in actual CRCP. To expand this core task to various parametric categories, a computer-aided parametric simulation was performed using valid numerical models. Based on data sets obtained from the parametric investigation, a statistical model to quantify the early-age structural response of CRCP was proposed to implement in codes of practice and pavement design guides. A secondary task was to identify a correlation between the early-age structural response and the long-term performance of CRCP structures. Since the experimental and analytical investigations tended to provide quite localized information for the time-dependent behavior of CRCP, the overall performance of CRCP could not be properly identified solely based on those results. To overcome this limitation, extensive field condition surveys were performed in seven different old CRCP sections with known material and early-age temperature history to find the implications of early-age behavior characteristics on the long-term performance of CRCP from a macroscopic point of view. It is expected that this research effort will provide pavement engineers and researchers with useful information to understand the actual time-dependent behavior of CRCP and a solid foundation to improve the sustainability of CRCP structures.