[Evaluation of the influence of humidity and temperature on the drug stability by initial average rate experiment].

PubMed

He, Ning; Sun, Hechun; Dai, Miaomiao

2014-05-01

To evaluate the influence of temperature and humidity on the drug stability by initial average rate experiment, and to obtained the kinetic parameters. The effect of concentration error, drug degradation extent, humidity and temperature numbers, humidity and temperature range, and average humidity and temperature on the accuracy and precision of kinetic parameters in the initial average rate experiment was explored. The stability of vitamin C, as a solid state model, was investigated by an initial average rate experiment. Under the same experimental conditions, the kinetic parameters obtained from this proposed method were comparable to those from classical isothermal experiment at constant humidity. The estimates were more accurate and precise by controlling the extent of drug degradation, changing humidity and temperature range, or by setting the average temperature closer to room temperature. Compared with isothermal experiments at constant humidity, our proposed method saves time, labor, and materials.

Performance of Surface-Mount Ceramic and Solid Tantalum Capacitors for Cryogenic Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; MacDonald, Thomas L.; Hammoud, Ahmad; Gerber, Scott

1998-01-01

Low temperature electronics are of great interest for space exploration programs. These include missions to the outer planets, earth-orbiting and deep-space probes, remote-sensing and communication satellites. Terrestrial applications would also benefit from the availability of low temperature electronics. Power components capable of low temperature operation would, thus, enhance the technologies needed for the development of advanced power systems suitable for use in harsh environments. In this work, ceramic and solid tantalum capacitors were evaluated in terms of their dielectric properties as a function of temperature and at various frequencies. The surface-mount devices were characterized in terms of their capacitance stability and dissipation factor in the frequency range of 50 Hz to 100 kHz at temperatures ranging from room temperature (20 deg. C) to about liquid nitrogen temperature (-190 deg. C). The results are discussed and conclusions made concerning the suitability of the capacitors investigated for low temperature applications.

Performance of the Micropower Voltage Reference ADR3430 Under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2011-01-01

Electronic systems designed for use in space exploration systems are expected to be exposed to harsh temperatures. For example, operation at cryogenic temperatures is anticipated in space missions such as polar craters of the moon (-223 C), James Webb Space Telescope (-236 C), Mars (-140 C), Europa (-223 C), Titan (-178 C), and other deep space probes away from the sun. Similarly, rovers and landers on the lunar surface, and deep space probes intended for the exploration of Venus are expected to encounter high temperature extremes. Electronics capable of operation under extreme temperatures would not only meet the requirements of future spacebased systems, but would also contribute to enhancing efficiency and improving reliability of these systems through the elimination of the thermal control elements that present electronics need for proper operation under the harsh environment of space. In this work, the performance of a micropower, high accuracy voltage reference was evaluated over a wide temperature range. The Analog Devices ADR3430 chip uses a patented voltage reference architecture to achieve high accuracy, low temperature coefficient, and low noise in a CMOS process [1]. The device combines two voltages of opposite temperature coefficients to create an output voltage that is almost independent of ambient temperature. It is rated for the industrial temperature range of -40 C to +125 C, and is ideal for use in low power precision data acquisition systems and in battery-powered devices. Table 1 shows some of the manufacturer s device specifications.

Modeling Control Strategies and Range Impacts for Electric Vehicle Integrated Thermal Management Systems with MATLAB/Simulink

DOE Office of Scientific and Technical Information (OSTI.GOV)

Titov, Gene; Lustbader, Jason Aaron

The National Renewable Energy Laboratory's (NREL's) CoolSim MATLAB/Simulink modeling framework was used to explore control strategies for an electric vehicle combined loop system. Three system variants of increased complexity and efficiency were explored: a glycol-based positive temperature coefficient heater (PTC), PTC with power electronics and electric motor (PEEM) waste heat recovery, and PTC with PEEM waste heat recovery plus heat pump versions. Additionally, the benefit of electric motor preheating was considered. A two-level control strategy was developed where the mode selection and component control were treated separately. Only the parameters typically available by vehicle sensors were used to control themore » system. The control approach included a mode selection algorithm and controllers for the compressor speed, cabin blower flow rate, coolant flow rate, and the front-end heat exchanger coolant bypass rate. The electric motor was bypassed by the cooling circuit until its temperature exceeded the coolant inlet temperature. The impact of these thermal systems on electric vehicle range during warmup was simulated for the Urban Dynamometer Driving Schedule (UDDS) and Highway Fuel Economy Test (HWFET2X) drive cycles weighted 45%/55% respectively. A range of ambient temperatures from -20 degrees C to +20 degrees C was considered. NREL's Future Automotive Systems Technology Simulator (FASTSim) vehicle modeling tool showed up to a 10.9% improvement in range for the full system over the baseline during warmup from cold soak. The full system with preheat showed up to 17% improvement in range.« less

Performance of High-Speed PWM Control Chips at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard; Overton, Eric

2001-01-01

The operation of power electronic systems at cryogenic temperatures is anticipated in many NASA space missions such as planetary exploration and deep space probes. In addition to surviving the space hostile environment, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. As part of the NASA Glenn Low Temperature Electronics Program, several commercial high-speed Pulse Width Modulation (PWM) chips have been characterized in terms of their performance as a function of temperature in the range of 25 to -196 C (liquid nitrogen). These chips ranged in their electrical characteristics, modes of control, packaging options, and applications. The experimental procedures along with the experimental data obtained on the investigated chips are presented and discussed.

Dissipative Dynamics of Enzymes

NASA Astrophysics Data System (ADS)

Ariyaratne, Amila; Wu, Chenhao; Tseng, Chiao-Yu; Zocchi, Giovanni

2014-11-01

We explore enzyme conformational dynamics at sub-Å resolution, specifically, temperature effects. The ensemble-averaged mechanical response of the folded enzyme is viscoelastic in the whole temperature range between the warm and cold denaturation transitions. The dissipation parameter γ of the viscoelastic description decreases by a factor of 2 as the temperature is raised from 10 to 45 °C ; the elastic parameter K shows a similar decrease. Thus, when probed dynamically, the enzyme softens for increasing temperature. Equilibrium mechanical experiments with the DNA spring (and a different enzyme) also show, qualitatively, a small softening for increasing temperature.

Dissipative Dynamics of Enzymes

NASA Astrophysics Data System (ADS)

Ariyaratne, Amila; Wu, Chenhao; Tseng, Chiao-Yu; Zocchi, Giovanni; Zocchi LabMolecular Biophysics Team

2015-03-01

We explore enzyme conformational dynamics at sub - Å resolution, specifically temperature effects. The ensemble averaged mechanical response of the folded enzyme is viscoelastic in the whole temperature range between the warm and cold denaturation transitions. The dissipation parameter γ of the viscoelastic description decreases by a factor 2 as the temperature is raised from 10 C to 45 C; the elastic parameter K shows a similar decrease. Thus when probed dynamically, the enzyme softens for increasing temperature. Equilibrium mechanical experiments with the DNA spring (and a different enzyme) also show, qualitatively, a small softening for increasing temperature.

Dissipative dynamics of enzymes.

PubMed

Ariyaratne, Amila; Wu, Chenhao; Tseng, Chiao-Yu; Zocchi, Giovanni

2014-11-07

We explore enzyme conformational dynamics at sub-Å resolution, specifically, temperature effects. The ensemble-averaged mechanical response of the folded enzyme is viscoelastic in the whole temperature range between the warm and cold denaturation transitions. The dissipation parameter γ of the viscoelastic description decreases by a factor of 2 as the temperature is raised from 10 to 45 °C; the elastic parameter K shows a similar decrease. Thus, when probed dynamically, the enzyme softens for increasing temperature. Equilibrium mechanical experiments with the DNA spring (and a different enzyme) also show, qualitatively, a small softening for increasing temperature.

Wide-Range Temperature Sensors with High-Level Pulse Train Output

NASA Technical Reports Server (NTRS)

Hammoud, Ahmad; Patterson, Richard L.

2009-01-01

Two types of temperature sensors have been developed for wide-range temperature applications. The two sensors measure temperature in the range of -190 to +200 C and utilize a thin-film platinum RTD (resistance temperature detector) as the temperature-sensing element. Other parts used in the fabrication of these sensors include NPO (negative-positive- zero) type ceramic capacitors for timing, thermally-stable film or wirewound resistors, and high-temperature circuit boards and solder. The first type of temperature sensor is a relaxation oscillator circuit using an SOI (silicon-on-insulator) operational amplifier as a comparator. The output is a pulse train with a period that is roughly proportional to the temperature being measured. The voltage level of the pulse train is high-level, for example 10 V. The high-level output makes the sensor less sensitive to noise or electromagnetic interference. The output can be read by a frequency or period meter and then converted into a temperature reading. The second type of temperature sensor is made up of various types of multivibrator circuits using an SOI type 555 timer and the passive components mentioned above. Three configurations have been developed that were based on the technique of charging and discharging a capacitor through a resistive element to create a train of pulses governed by the capacitor-resistor time constant. Both types of sensors, which operated successfully over the wide temperature range, have potential use in extreme temperature environments including jet engines and space exploration missions.

Exploration of the Structure of the High Temperature Phase of the Hexagonal RMnO3 System

NASA Astrophysics Data System (ADS)

Wu, T.; Tyson, T. A.; Zhang, H.; Yu, T.; Page, K.; Ghose, S.

Temperature dependent structural studies of the high temperature phase of hexagonal RMnO3 systems have been conducted. Both long range and local structural probes have been utilized. Discussions of the appropriate space groups and local distortions relevant to length scale will be given. Ab initio MD simulations are used to interpret the observations. This work is supported by DOE Grant DE-FG02-07ER46402.

When do Indians feel hot? Internet searches indicate seasonality suppresses adaptation to heat

NASA Astrophysics Data System (ADS)

Singh, Tanya; Siderius, Christian; Van der Velde, Ype

2018-05-01

In a warming world an increasing number of people are being exposed to heat, making a comfortable thermal environment an important need. This study explores the potential of using Regional Internet Search Frequencies (RISF) for air conditioning devices as an indicator for thermal discomfort (i.e. dissatisfaction with the thermal environment) with the aim to quantify the adaptation potential of individuals living across different climate zones and at the high end of the temperature range, in India, where access to health data is limited. We related RISF for the years 2011–2015 to daily daytime outdoor temperature in 17 states and determined at which temperature RISF for air conditioning starts to peak, i.e. crosses a ‘heat threshold’, in each state. Using the spatial variation in heat thresholds, we explored whether people continuously exposed to higher temperatures show a lower response to heat extremes through adaptation (e.g. physiological, behavioural or psychological). State-level heat thresholds ranged from 25.9 °C in Madhya Pradesh to 31.0 °C in Orissa. Local adaptation was found to occur at state level: the higher the average temperature in a state, the higher the heat threshold; and the higher the intra-annual temperature range (warmest minus coldest month) the lower the heat threshold. These results indicate there is potential within India to adapt to warmer temperatures, but that a large intra-annual temperature variability attenuates this potential to adapt to extreme heat. This winter ‘reset’ mechanism should be taken into account when assessing the impact of global warming, with changes in minimum temperatures being an important factor in addition to the change in maximum temperatures itself. Our findings contribute to a better understanding of local heat thresholds and people’s adaptive capacity, which can support the design of local thermal comfort standards and early heat warning systems.

Asymmetry of projected increases in extreme temperature distributions

PubMed Central

Kodra, Evan; Ganguly, Auroop R.

2014-01-01

A statistical analysis reveals projections of consistently larger increases in the highest percentiles of summer and winter temperature maxima and minima versus the respective lowest percentiles, resulting in a wider range of temperature extremes in the future. These asymmetric changes in tail distributions of temperature appear robust when explored through 14 CMIP5 climate models and three reanalysis datasets. Asymmetry of projected increases in temperature extremes generalizes widely. Magnitude of the projected asymmetry depends significantly on region, season, land-ocean contrast, and climate model variability as well as whether the extremes of consideration are seasonal minima or maxima events. An assessment of potential physical mechanisms provides support for asymmetric tail increases and hence wider temperature extremes ranges, especially for northern winter extremes. These results offer statistically grounded perspectives on projected changes in the IPCC-recommended extremes indices relevant for impacts and adaptation studies. PMID:25073751

Extreme Temperature Performance of Automotive-Grade Small Signal Bipolar Junction Transistors

NASA Technical Reports Server (NTRS)

Boomer, Kristen; Damron, Benny; Gray, Josh; Hammoud, Ahmad

2018-01-01

Electronics designed for space exploration missions must display efficient and reliable operation under extreme temperature conditions. For example, lunar outposts, Mars rovers and landers, James Webb Space Telescope, Europa orbiter, and deep space probes represent examples of missions where extreme temperatures and thermal cycling are encountered. Switching transistors, small signal as well as power level devices, are widely used in electronic controllers, data instrumentation, and power management and distribution systems. Little is known, however, about their performance in extreme temperature environments beyond their specified operating range; in particular under cryogenic conditions. This report summarizes preliminary results obtained on the evaluation of commercial-off-the-shelf (COTS) automotive-grade NPN small signal transistors over a wide temperature range and thermal cycling. The investigations were carried out to establish a baseline on functionality of these transistors and to determine suitability for use outside their recommended temperature limits.

Task-Specific Ionic Liquids for Mars Exploration (Green Chemistry for a Red Planet)

NASA Technical Reports Server (NTRS)

Karr, L. J.; Curreri, P. A.; Paley, M. S.; Kaukler, W. F.; Marone, M. J.

2012-01-01

Ionic Liquids (ILs) are organic salts with low melting points that are liquid at or near room temperature. The combinations of available ions and task-specific molecular designability make them suitable for a huge variety of tasks. Because of their low flammability, low vapor pressure, and stability in harsh environments (extreme temperatures, hard vacuum) they are generally much safer and "greener" than conventional chemicals and are thus suitable for a wide range of applications that support NASA exploration goals. This presentation describes several of the ongoing applications that are being developed at MSFC.

Phenological shifts conserve thermal niches in North American birds and reshape expectations for climate-driven range shifts.

PubMed

Socolar, Jacob B; Epanchin, Peter N; Beissinger, Steven R; Tingley, Morgan W

2017-12-05

Species respond to climate change in two dominant ways: range shifts in latitude or elevation and phenological shifts of life-history events. Range shifts are widely viewed as the principal mechanism for thermal niche tracking, and phenological shifts in birds and other consumers are widely understood as the principal mechanism for tracking temporal peaks in biotic resources. However, phenological and range shifts each present simultaneous opportunities for temperature and resource tracking, although the possible role for phenological shifts in thermal niche tracking has been widely overlooked. Using a canonical dataset of Californian bird surveys and a detectability-based approach for quantifying phenological signal, we show that Californian bird communities advanced their breeding phenology by 5-12 d over the last century. This phenological shift might track shifting resource peaks, but it also reduces average temperatures during nesting by over 1 °C, approximately the same magnitude that average temperatures have warmed over the same period. We further show that early-summer temperature anomalies are correlated with nest success in a continental-scale database of bird nests, suggesting avian thermal niches might be broadly limited by temperatures during nesting. These findings outline an adaptation surface where geographic range and breeding phenology respond jointly to constraints imposed by temperature and resource phenology. By stabilizing temperatures during nesting, phenological shifts might mitigate the need for range shifts. Global change ecology will benefit from further exploring phenological adjustment as a potential mechanism for thermal niche tracking and vice versa.

Stability of a Crystal Oscillator, Type Si530, Inside and Beyond its Specified Operating Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2011-01-01

Data acquisition and control systems depend on timing signals for proper operation and required accuracy. These clocked signals are typically provided by some form of an oscillator set to produce a repetitive, defined signal at a given frequency. Crystal oscillators are commonly used because they are less expensive, smaller, and more reliable than other types of oscillators. Because of the inherent characteristics of the crystal, the oscillators exhibit excellent frequency stability within the specified range of operational temperature. In some cases, however, some compensation techniques are adopted to further improve the thermal stability of a crystal oscillator. Very limited data exist on the performance and reliability of commercial-off-the-shelf (COTS) crystal oscillators at temperatures beyond the manufacturer's specified operating temperature range. This information is very crucial if any of these parts were to be used in circuits designed for use in space exploration missions where extreme temperature swings and thermal cycling are encountered. This report presents the results of the work obtained on the operation of Silicon Laboratories crystal oscillator, type Si530, under specified and extreme ambient temperatures.

Estimated effects of temperature on secondary organic aerosol concentrations.

PubMed

Sheehan, P E; Bowman, F M

2001-06-01

The temperature-dependence of secondary organic aerosol (SOA) concentrations is explored using an absorptive-partitioning model under a variety of simplified atmospheric conditions. Experimentally determined partitioning parameters for high yield aromatics are used. Variation of vapor pressures with temperature is assumed to be the main source of temperature effects. Known semivolatile products are used to define a modeling range of vaporization enthalpy of 10-25 kcal/mol-1. The effect of diurnal temperature variations on model predictions for various assumed vaporization enthalpies, precursor emission rates, and primary organic concentrations is explored. Results show that temperature is likely to have a significant influence on SOA partitioning and resulting SOA concentrations. A 10 degrees C decrease in temperature is estimated to increase SOA yields by 20-150%, depending on the assumed vaporization enthalpy. In model simulations, high daytime temperatures tend to reduce SOA concentrations by 16-24%, while cooler nighttime temperatures lead to a 22-34% increase, compared to constant temperature conditions. Results suggest that currently available constant temperature partitioning coefficients do not adequately represent atmospheric SOA partitioning behavior. Air quality models neglecting the temperature dependence of partitioning are expected to underpredict peak SOA concentrations as well as mistime their occurrence.

Estimating extreme stream temperatures by the standard deviate method

NASA Astrophysics Data System (ADS)

Bogan, Travis; Othmer, Jonathan; Mohseni, Omid; Stefan, Heinz

2006-02-01

It is now widely accepted that global climate warming is taking place on the earth. Among many other effects, a rise in air temperatures is expected to increase stream temperatures indefinitely. However, due to evaporative cooling, stream temperatures do not increase linearly with increasing air temperatures indefinitely. Within the anticipated bounds of climate warming, extreme stream temperatures may therefore not rise substantially. With this concept in mind, past extreme temperatures measured at 720 USGS stream gauging stations were analyzed by the standard deviate method. In this method the highest stream temperatures are expressed as the mean temperature of a measured partial maximum stream temperature series plus its standard deviation multiplied by a factor KE (standard deviate). Various KE-values were explored; values of KE larger than 8 were found physically unreasonable. It is concluded that the value of KE should be in the range from 7 to 8. A unit error in estimating KE translates into a typical stream temperature error of about 0.5 °C. Using a logistic model for the stream temperature/air temperature relationship, a one degree error in air temperature gives a typical error of 0.16 °C in stream temperature. With a projected error in the enveloping standard deviate dKE=1.0 (range 0.5-1.5) and an error in projected high air temperature d Ta=2 °C (range 0-4 °C), the total projected stream temperature error is estimated as d Ts=0.8 °C.

Improved Wide Operating Temperature Range of Li-Ion Cells

NASA Technical Reports Server (NTRS)

Smart, Marshall C.; Bugga, Ratnakumar V.

2013-01-01

Future NASA missions aimed at exploring the Moon, Mars, and the outer planets require rechargeable batteries that can operate over a wide temperature range (-60 to +60 C) to satisfy the requirements of various applications including landers, rovers, penetrators, CEV, CLV, etc. This work addresses the need for robust rechargeable batteries that can operate well over a wide temperature range. The Department of Energy (DoE) has identified a number of technical barriers associated with the development of Liion rechargeable batteries for PHEVs. For this reason, DoE has interest in the development of advanced electrolytes that will improve performance over a wide range of temperatures, and lead to long life characteristics (5,000 cycles over a 10-year life span). There is also interest in improving the high-voltage stability of these candidate electrolyte systems to enable the operation of up to 5 V with high specific energy cathode materials. Currently, the state-of-the-art lithium-ion system has been demonstrated to operate over a wide range of temperatures (-40 to +40 C); however, the rate capability at the lower temperatures is very poor. In addition, the low-temperature performance typically deteriorates rapidly upon being exposed to high temperatures. A number of electrolyte formulations were developed that incorporate the use of electrolyte additives to improve the high-temperature resilience, low-temperature power capability, and life characteristics of methyl propionate (MP)-based electrolyte solutions. These electrolyte additives include mono-fluoroethylene carbonate (FEC), lithium oxalate, vinylene carbonate (VC), and lithium bis(oxalate borate) (LiBOB), which have previously been shown to result in improved high-temperature resilience of all carbonate-based electrolytes. These MP-based electrolytes with additives have been shown to have improved performance in experiments with MCMB-LiNiCoAlO2 cells.

Exploring the fine structure at the limb in coronal holes

NASA Technical Reports Server (NTRS)

Karovska, Magarita; Blundell, Solon F.; Habbal, Shadia Rifai

1994-01-01

The fine structure of the solar limb in coronal holes is explored at temperatures ranging from 10(exp 4) to 10(exp 6) K. An image enhancement algorithm orignally developed for solar eclipse observations is applied to a number of simultaneous multiwavelength observations made with the Harvard Extreme Ultraviolet Spectrometer experiment on Skylab. The enhanced images reveal the presence of filamentary structures above the limb with a characteristic separation of approximately 10 to 15 sec . Some of the structures extend from the solar limb into the corona to at least 4 min above the solar limb. The brightness of these structures changes as a function of height above the limb. The brightest emission is associated with spiculelike structures in the proximity of the limb. The emission characteristic of high-temperature plasma is not cospatial with the emission at lower temperatures, indicating the presence of different temperature plasmas in the field of view.

Extreme High and Low Temperature Operation of the Silicon-On-Insulator Type CHT-OPA Operational Amplifier

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad; Elbuluk, Malik

2008-01-01

A new operational amplifier chip based on silicon-on-insulator technology was evaluated for potential use in extreme temperature environments. The CHT-OPA device is a low power, precision operational amplifier with rail-to-rail output swing capability, and it is rated for operation between -55 C and +225 C. A unity gain inverting circuit was constructed utilizing the CHT-OPA chip and a few passive components. The circuit was evaluated in the temperature range from -190 C to +200 C in terms of signal gain and phase shift, and supply current. The investigations were carried out to determine suitability of this device for use in space exploration missions and aeronautic applications under wide temperature incursion. Re-restart capability at extreme temperatures, i.e. power switched on while the device was soaked at extreme temperatures, was also investigated. In addition, the effects of thermal cycling under a wide temperature range on the operation of this high performance amplifier were determined. The results from this work indicate that this silicon-on-insulator amplifier chip maintained very good operation between +200 C and -190 C. The limited thermal cycling had no effect on the performance of the amplifier, and it was able to re-start at both -190 C and +200 C. In addition, no physical degradation or packaging damage was introduced due to either extreme temperature exposure or thermal cycling. The good performance demonstrated by this silicon-on-insulator operational amplifier renders it a potential candidate for use in space exploration missions or other environments under extreme temperatures. Additional and more comprehensive characterization is, however, required to establish the reliability and suitability of such devices for long term use in extreme temperature applications.

Lithium Batteries and Supercapacitors Capable of Operating at Low Temperatures for Planetary Exploration

NASA Technical Reports Server (NTRS)

Smart, M. C.; Ratnakumar, B. V.; West, W. C.; Brandon, E. J.

2012-01-01

Demonstrated improved performance with wide operating temperature electrolytes containing ester co - solvents (i.e., methyl propionate and ethyl butyrate) in a number of prototype cells: center dot Successfully scaled up low temperature technology to 12 Ah size prismatic Li - ion cells (Quallion, LCC), and demonstrated good performance down to - 60 o C. center dot Demonstrated wide operating temperature range performance ( - 60 o to +60 o C) in A123 Systems LiFePO 4 - based lithium - ion cells containing methyl butyrate - based low temperature electrolytes. These systems were also demonstrated to have excellent cycle life performance at ambient temperatures, as well as the ability to be cycled up to high temperatures.

Temperature range and degree of acidity growth of isolate of indigenous bacteria on fermented feed “fermege”

NASA Astrophysics Data System (ADS)

Isnawati; Trimulyono, G.

2018-01-01

Fermege is a fermented feed of ruminants, especially goats made from water hyacinth (Eichhornia crassipes). Temperature range and pH need to know in making starter formula for acceleration of fermentation process at making ruminant feed made from this materials. The starter formula expired period can be extended by adjusting starter storage temperature and pH of the starter. This research was aimed to find the temperature and pH range for the growth of isolate of indigenous bacteria “fermege.” This research is an explorative research conducted by growing bacteria isolate indigenous fermege in liquid medium with various pH and incubation in various temperature. Bacterial population was calculated based on turbidity of bacterial suspension with turbidometer. The stages of this research were to isolate the bacteria present in the fermege, purify the isolates found, and then grow the isolates in a liquid medium with various pH values. The isolated bacterials were incubated at different temperature variations. The cell population density of the isolates was calculated after incubation for 24 hours. The results showed there were eight indigenous bacterial isolates. All isolates can grow in the pH range 6 and 7. Two isolates (Bacillus subtilis and B. pumilus) can grow at 4°C. All isolates obtained can grow at a temperature of 30°C. Isolates Bacillus badius, B. subtilis, B. cereus, Pseudomonas stutzeri and P. diminuta can grow at 50°C. Based on research indicates that indigenous fermege bacterial isolates have the ability to grow in the neutral pH range and temperature range between 4°C and 50°C.

Rainfall and temperatures changes have confounding impacts on Phytophthora cinnamomi occurrence risk in the southwestern USA under climate change scenarios.

PubMed

Thompson, Sally E; Levin, Simon; Rodriguez-Iturbe, Ignacio

2014-04-01

Global change will simultaneously impact many aspects of climate, with the potential to exacerbate the risks posed by plant pathogens to agriculture and the natural environment; yet, most studies that explore climate impacts on plant pathogen ranges consider individual climatic factors separately. In this study, we adopt a stochastic modeling approach to address multiple pathways by which climate can constrain the range of the generalist plant pathogen Phytophthora cinnamomi (Pc): through changing winter soil temperatures affecting pathogen survival; spring soil temperatures and thus pathogen metabolic rates; and changing spring soil moisture conditions and thus pathogen growth rates through host root systems. We apply this model to the southwestern USA for contemporary and plausible future climate scenarios and evaluate the changes in the potential range of Pc. The results indicate that the plausible range of this pathogen in the southwestern USA extends over approximately 200,000 km(2) under contemporary conditions. While warming temperatures as projected by the IPCC A2 and B1 emissions scenarios greatly expand the range over which the pathogen can survive winter, projected reductions in spring rainfall reduce its feasible habitat, leading to spatially complex patterns of changing risk. The study demonstrates that temperature and rainfall changes associated with possible climate futures in the southwestern USA have confounding impacts on the range of Pc, suggesting that projections of future pathogen dynamics and ranges should account for multiple pathways of climate-pathogen interaction. © 2014 John Wiley & Sons Ltd.

Exploring the limits of identifying sub-pixel thermal features using ASTER TIR data

USGS Publications Warehouse

Vaughan, R.G.; Keszthelyi, L.P.; Davies, A.G.; Schneider, D.J.; Jaworowski, C.; Heasler, H.

2010-01-01

Understanding the characteristics of volcanic thermal emissions and how they change with time is important for forecasting and monitoring volcanic activity and potential hazards. Satellite instruments view volcanic thermal features across the globe at various temporal and spatial resolutions. Thermal features that may be a precursor to a major eruption, or indicative of important changes in an on-going eruption can be subtle, making them challenging to reliably identify with satellite instruments. The goal of this study was to explore the limits of the types and magnitudes of thermal anomalies that could be detected using satellite thermal infrared (TIR) data. Specifically, the characterization of sub-pixel thermal features with a wide range of temperatures is considered using ASTER multispectral TIR data. First, theoretical calculations were made to define a "thermal mixing detection threshold" for ASTER, which quantifies the limits of ASTER's ability to resolve sub-pixel thermal mixing over a range of hot target temperatures and % pixel areas. Then, ASTER TIR data were used to model sub-pixel thermal features at the Yellowstone National Park geothermal area (hot spring pools with temperatures from 40 to 90 ??C) and at Mount Erebus Volcano, Antarctica (an active lava lake with temperatures from 200 to 800 ??C). Finally, various sources of uncertainty in sub-pixel thermal calculations were quantified for these empirical measurements, including pixel resampling, atmospheric correction, and background temperature and emissivity assumptions.

Wide-Temperature-Range Integrated Operational Amplifier

NASA Technical Reports Server (NTRS)

Mojarradi, Mohammad; Levanas, Greg; Chen, Yuan; Kolawa, Elizabeth; Cozy, Raymond; Blalock, Benjamin; Greenwell, Robert; Terry, Stephen

2007-01-01

A document discusses a silicon-on-insulator (SOI) complementary metal oxide/semiconductor (CMOS) integrated- circuit operational amplifier to be replicated and incorporated into sensor and actuator systems of Mars-explorer robots. This amplifier is designed to function at a supply potential less than or equal to 5.5 V, at any temperature from -180 to +120 C. The design is implemented on a commercial radiation-hard SOI CMOS process rated for a supply potential of less than or equal to 3.6 V and temperatures from -55 to +110 C. The design incorporates several innovations to achieve this, the main ones being the following: NMOS transistor channel lengths below 1 m are generally not used because research showed that this change could reduce the adverse effect of hot carrier injection on the lifetimes of transistors at low temperatures. To enable the amplifier to withstand the 5.5-V supply potential, a circuit topology including cascade devices, clamping devices, and dynamic voltage biasing was adopted so that no individual transistor would be exposed to more than 3.6 V. To minimize undesired variations in performance over the temperature range, the transistors in the amplifier are biased by circuitry that maintains a constant inversion coefficient over the temperature range.

Magnetic, structural and magnetocaloric properties of Ni-Si and Ni-Al thermoseeds for self-controlled hyperthermia.

PubMed

Pandey, Sudip; Quetz, Abdiel; Aryal, Anil; Dubenko, Igor; Mazumdar, Dipanjan; Stadler, Shane; Ali, Naushad

2017-11-01

Self-controlled hyperthermia is a non-invasive technique used to kill or destroy cancer cells while preserving normal surrounding tissues. We have explored bulk magnetic Ni-Si and Ni-Al alloys as a potential thermoseeds. The structural, magnetic and magnetocaloric properties of the samples were investigated, including saturation magnetisation, Curie temperature (T C ), and magnetic and thermal hysteresis, using room temperature X-ray diffraction and magnetometry. The annealing time, temperature and the effects of homogenising the thermoseeds were studied to determine the functional hyperthermia applications. The bulk Ni-Si and Ni-Al binary alloys have Curie temperatures in the desired range, 316 K-319 K (43 °C-46 °C), which is suitable for magnetic hyperthermia applications. We have found that T C strictly follows a linear trend with doping concentration over a wide range of temperature. The magnetic ordering temperature and the magnetic properties can be controlled through substitution in these binary alloys.

Effects of Temperature on the Performance and Stability of Recent COTS Silicon Oscillators

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2010-01-01

Silicon oscillators have lately emerged to serve as potential replacement for crystal and ceramic resonators to provide timing and clock signals in electronic systems. These semiconductor-based devices, including those that are based on MEMS technology, are reported to be resistant to vibration and shock (an important criteria for systems to be deployed in space), immune to EMI, consume very low current, require few or no external components, and cover a wide range of frequency for analog and digital circuits. In this work, the performance of five recently-developed COTS silicon oscillator chips from different manufacturers was determined within a temperature range that extended beyond the individual specified range of operation. In addition, restart capability at extreme temperatures, i.e. power switched on while the device was soaking at extreme (hot or cold) temperature, and the effects of thermal cycling under a wide temperature range on the operation of these silicon oscillators were also investigated. Performance characterization of each oscillator was obtained in terms of its output frequency, duty cycle, rise and fall times, and supply current at specific test temperatures. The five different oscillators tested operated beyond their specified temperature region, with some displaying excellent stability throughout the whole test temperature range. Others experienced some instability at certain temperature test points as evidenced by fluctuation in the output frequency. Recovery from temperature-induced changes took place when excessive temperatures were removed. It should also be pointed out that all oscillators were able to restart at the extreme test temperatures and to withstand the limited thermal cycling without undergoing any significant changes in their characteristics. In addition, no physical damage was observed in the packaging material of any of these silicon oscillators due to extreme temperature exposure and thermal cycling. It is recommended that additional and more comprehensive testing under long term cycling be carried out to fully establish the reliability of these devices and to determine their suitability for use in space exploration missions under extreme temperature conditions.

Preliminary estimation of the realistic optimum temperature for vegetation growth in China.

PubMed

Cui, Yaoping

2013-07-01

The estimation of optimum temperature of vegetation growth is very useful for a wide range of applications such as agriculture and climate change studies. Thermal conditions substantially affect vegetation growth. In this study, the normalized difference vegetation index (NDVI) and daily temperature data set from 1982 to 2006 for China were used to examine optimum temperature of vegetation growth. Based on a simple analysis of ecological amplitude and Shelford's law of tolerance, a scientific framework for calculating the optimum temperature was constructed. The optimum temperature range and referenced optimum temperature (ROT) of terrestrial vegetation were obtained and explored over different eco-geographical regions of China. The results showed that the relationship between NDVI and air temperature was significant over almost all of China, indicating that terrestrial vegetation growth was closely related to thermal conditions. ROTs were different in various regions. The lowest ROT, about 7.0 °C, occurred in the Qinghai-Tibet Plateau, while the highest ROT, more than 22.0 °C, occurred in the middle and lower reaches of the Yangtze River and the Southern China region.

Preliminary Estimation of the Realistic Optimum Temperature for Vegetation Growth in China

NASA Astrophysics Data System (ADS)

Cui, Yaoping

2013-07-01

The estimation of optimum temperature of vegetation growth is very useful for a wide range of applications such as agriculture and climate change studies. Thermal conditions substantially affect vegetation growth. In this study, the normalized difference vegetation index (NDVI) and daily temperature data set from 1982 to 2006 for China were used to examine optimum temperature of vegetation growth. Based on a simple analysis of ecological amplitude and Shelford's law of tolerance, a scientific framework for calculating the optimum temperature was constructed. The optimum temperature range and referenced optimum temperature (ROT) of terrestrial vegetation were obtained and explored over different eco-geographical regions of China. The results showed that the relationship between NDVI and air temperature was significant over almost all of China, indicating that terrestrial vegetation growth was closely related to thermal conditions. ROTs were different in various regions. The lowest ROT, about 7.0 °C, occurred in the Qinghai-Tibet Plateau, while the highest ROT, more than 22.0 °C, occurred in the middle and lower reaches of the Yangtze River and the Southern China region.

Evolution of basin and range structure in the Ruby Mountains and vicinity, Nevada

NASA Technical Reports Server (NTRS)

Blackwell, D. D.; Reese, N. M.; Kelley, S. A.

1985-01-01

Results from various age dating techniques, seismic reflection profiling hydrocarbon maturation studies, and structural analysis were used to evaluate the Cenozoic deformation in the Ruby Mountains and adjoining ranges (pinyon Range and Cortez Range) in Elko and Eureka Counties, Nevada. Age dating techniques used include potassium-argon ages of biotites from granites published by Kistler et al. (1981) and fission track ages from apatite and zircon. Fission track ages from apatite reflect a closing temperature of 100 plus or minus 20 deg C. Zircon fission track ages reflect a closing temperature of 175 plus or minus 25 deg C and potassium-argon ages from brotite reflect a closing temperature of 250 plus or minus 30 deg C. Thus these results allow a reasonably precise tracking of the evolution of the ranges during the Cenozoic. Seismic reflection data are available from Huntington Valley. Access to seismic reflection data directly to the west of the Harrison Pass Pluton in the central Ruby Mountains was obtained. In addition results are available from several deep exploration holes in Huntington Valley.

Winter Precipitation Efficiency of Mountain Ranges in the Colorado Rockies Under Climate Change

NASA Astrophysics Data System (ADS)

Eidhammer, Trude; Grubišić, Vanda; Rasmussen, Roy; Ikdea, Kyoko

2018-03-01

Orographic precipitation depends on the environmental conditions and the barrier shape. In this study we examine the sensitivity of the precipitation efficiency (i.e., drying ratio (DR)), defined as the ratio of precipitation to incoming water flux, to mountain shape, temperature, stability, and horizontal velocity of the incoming air mass. Furthermore, we explore how the DR of Colorado mountain ranges might change under warmer and moister conditions in the future. For given environmental conditions, we find the DR to be primarily dependent on the upwind slope for mountain ranges wider than about 70 km and on both the slope and width for narrower ranges. Temperature is found to exert an influence on the DR for all Colorado mountain ranges, with DR decreasing with increasing temperature, under both the current and future climate conditions. The decrease of DR with temperature under warmer climate was found to be stronger for wider mountains than the narrower ones. We attribute this asymmetry to the sensitivity of DR to reduced horizontal velocity under warmer conditions. Specifically, while DR for wider mountains shows no sensitivity to changes in horizontal velocity, the DR for narrow ranges increases as the horizontal velocity decreases and more time is provided for precipitation to form. Thus, for narrower ranges, the horizontal velocity appears to offset the temperature effect slightly. The percentagewise decrease of DR for all examined mountain ranges is about 4%K-1. In comparison, the increase in precipitation is about 6%K-1 while the vapor flux increase is about 9%K-1.

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

DOE PAGES

Lapa, Pavel N.; Ding, Junjia; Phatak, Charudatta; ...

2017-08-28

The topological nature of magnetic-vortex state gives rise to peculiar magnetization reversal observed in magnetic microdisks. Interestingly, magnetostatic and exchange energies which drive this reversal can be effectively controlled in artificial ferrimagnet heterostructures composed of rare-earth and transition metals. [Py(t)/Gd(t)] 25 (t=1 or 2 nm) superlattices demonstrate a pronounced change of the magnetization and exchange stiffness in a 10–300 K temperature range as well as very small magnetic anisotropy. Due to these properties, the magnetization of cylindrical microdisks composed of these artificial ferrimagnets can be transformed from the vortex to uniformly-magnetized states in a permanent magnetic field by changing themore » temperature. We explored the behavior of magnetization in 1.5-µm [Py(t)/Gd(t)] 25 (t=1 or 2 nm) disks at different temperatures and magnetic fields and observed that due to the energy barrier separating vortex and uniformly-magnetized states, the vortex nucleation and annihilation occur at different temperatures. This causes the temperature dependences of the Py/Gd disks magnetization to demonstrate unique hysteretic behavior in a narrow temperature range. It was discovered that for the [Py(2 nm)/Gd(2 nm)] 25 microdisks the vortex can be metastable at a certain temperature range.« less

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lapa, Pavel N.; Ding, Junjia; Phatak, Charudatta

The topological nature of magnetic-vortex state gives rise to peculiar magnetization reversal observed in magnetic microdisks. Interestingly, magnetostatic and exchange energies which drive this reversal can be effectively controlled in artificial ferrimagnet heterostructures composed of rare-earth and transition metals. [Py(t)/Gd(t)] 25 (t=1 or 2 nm) superlattices demonstrate a pronounced change of the magnetization and exchange stiffness in a 10–300 K temperature range as well as very small magnetic anisotropy. Due to these properties, the magnetization of cylindrical microdisks composed of these artificial ferrimagnets can be transformed from the vortex to uniformly-magnetized states in a permanent magnetic field by changing themore » temperature. We explored the behavior of magnetization in 1.5-µm [Py(t)/Gd(t)] 25 (t=1 or 2 nm) disks at different temperatures and magnetic fields and observed that due to the energy barrier separating vortex and uniformly-magnetized states, the vortex nucleation and annihilation occur at different temperatures. This causes the temperature dependences of the Py/Gd disks magnetization to demonstrate unique hysteretic behavior in a narrow temperature range. It was discovered that for the [Py(2 nm)/Gd(2 nm)] 25 microdisks the vortex can be metastable at a certain temperature range.« less

Body Temperature Measurements for Metabolic Phenotyping in Mice

PubMed Central

Meyer, Carola W.; Ootsuka, Youichirou; Romanovsky, Andrej A.

2017-01-01

Endothermic organisms rely on tightly balanced energy budgets to maintain a regulated body temperature and body mass. Metabolic phenotyping of mice, therefore, often includes the recording of body temperature. Thermometry in mice is conducted at various sites, using various devices and measurement practices, ranging from single-time probing to continuous temperature imaging. Whilst there is broad agreement that body temperature data is of value, procedural considerations of body temperature measurements in the context of metabolic phenotyping are missing. Here, we provide an overview of the various methods currently available for gathering body temperature data from mice. We explore the scope and limitations of thermometry in mice, with the hope of assisting researchers in the selection of appropriate approaches, and conditions, for comprehensive mouse phenotypic analyses. PMID:28824441

Temperature and pH effect on glucose production from pretreated bagasse by a novel species of Citrobacter and other bacteria.

PubMed

Jones, Jamila A D; Kerr, R G; Haltli, B A; Tinto, Winston F

2018-06-01

Cellulolytic bacteria that produce cellulases, which are active over a range of pH and temperatures, can be used to catalyze hydrolysis of pretreated lignocellulosic material. This is important in the production of second generation biofuels among other biotechnological applications. In this investigation, bacteria isolated from sugarcane bagasse were identified as strains of Enterobacter xiangfangensis , Serratia rubidaea , Klebsiella pneumoniae and a novel species of Citrobacter designated Citrobacter sp. UWIBGS10. The glucose production potential of these strains was studied on thermally and solvent pretreated sugarcane bagasse. This was performed at 24-hour intervals up to 168 hours in the range of pH 5-9 and temperature range 25-40 °C. Maximal concentrations of glucose for Citrobacter sp. UWIBGS10 occurred at pH 6 and 25 °C. For E. xiangfangensis , S. rubidaea , K. pneumoniae glucose concentrations were consistent across the pH and temperature ranges examined. From these results it could be concluded that the bacteria demonstrated ability for lignocellulolytic hydrolysis for the production of glucose and could be further explored for the characterization of commercial cellulolytic enzymes.

Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

NASA Astrophysics Data System (ADS)

Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

2016-06-01

Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature ( T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

Post-Shock Sampling of Shock-Heated Hydrocarbon Fuels

DTIC Science & Technology

2016-07-07

on the ability to measure key hydrocarbon fragments (e.g. ethylene , methane, and acetylene) over a wide range of temperatures and pressures. The...series of experiments was conducted to validate the sampling system results and explore the thermal decomposition of ethylene and methane. Initially, a...1% ethylene /0.1% methane/balance argon fuel mixture was shock-heated to ~960 K – a temperature low enough that no reaction would occur. GC analysis

Climate warming and water primroses: germination responses of populations from two invaded ranges

USDA-ARS?s Scientific Manuscript database

Seed germination is a crucial step of plant reproduction, widely influenced by environmental conditions, including temperature. The aim of this study was to explore the germination capacity of the invasive species Ludwigia hexapetala and Ludwigia peploides subsp. montevidensis including populations ...

The impact of seasonality on niche breadth, distribution range and species richness: a theoretical exploration of Janzen's hypothesis.

PubMed

Hua, Xia

2016-07-27

Being invoked as one of the candidate mechanisms for the latitudinal patterns in biodiversity, Janzen's hypothesis states that the limited seasonal temperature variation in the tropics generates greater temperature stratification across elevations, which makes tropical species adapted to narrower ranges of temperatures and have lower effective dispersal across elevations than species in temperate regions. Numerous empirical studies have documented latitudinal patterns in species elevational ranges and thermal niche breadths that are consistent with the hypothesis, but the theoretical underpinnings remain unclear. This study presents the first mathematical model to examine the evolutionary processes that could back up Janzen's hypothesis and assess the effectiveness of limited seasonal temperature variation to promote speciation along elevation in the tropics. Results suggest that trade-offs in thermal tolerances provide a mechanism for Janzen's hypothesis. Limited seasonal temperature variation promotes gradient speciation not due to the reduction in gene flow that is associated with narrow thermal niche, but due to the pleiotropic effects of more stable divergent selection of thermal tolerance on the evolution of reproductive incompatibility. The proposed modelling approach also provides a potential way to test a speciation model against genetic data. © 2016 The Author(s).

Thermostatic Valves Containing Silicone-Oil Actuators

NASA Technical Reports Server (NTRS)

Bhandari, Pradeep; Birur, Gajanana C.; Bame, David P.; Karlmann, Paul B.; Prina, Mauro; Young, William; Fisher, Richard

2009-01-01

Flow-splitting and flow-mixing thermally actuated spool valves have been developed for controlling flows of a heat-transfer fluid in a temperature-regulation system aboard the Mars Science Laboratory (MSL) rover. Valves like these could also be useful in terrestrial temperature-regulation systems, including automobile air-conditioning systems and general refrigeration systems. These valves are required to provide smoother actuation over a wider temperature range than the flow-splitting, thermally actuated spool valves used in the Mars Explorer Rover (MER). Also, whereas the MER valves are unstable (tending to oscillate) in certain transition temperature ranges, these valves are required not to oscillate. The MER valves are actuated by thermal expansion of a wax against spring-loaded piston rods (as in common automotive thermostats). The MSL valves contain similar actuators that utilize thermal expansion of a silicone oil, because silicone-oil actuators were found to afford greater and more nearly linear displacements, needed for smoother actuation, over the required wider temperature range. The MSL valves also feature improved spool designs that reflect greater understanding of fluid dynamics, consideration of pressure drops in valves, and a requirement for balancing of pressures in different flow branches.

Quantifying the effects of temperature on mosquito and parasite traits that determine the transmission potential of human malaria.

PubMed

Shapiro, Lillian L M; Whitehead, Shelley A; Thomas, Matthew B

2017-10-01

Malaria transmission is known to be strongly impacted by temperature. The current understanding of how temperature affects mosquito and parasite life history traits derives from a limited number of empirical studies. These studies, some dating back to the early part of last century, are often poorly controlled, have limited replication, explore a narrow range of temperatures, and use a mixture of parasite and mosquito species. Here, we use a single pairing of the Asian mosquito vector, An. stephensi and the human malaria parasite, P. falciparum to conduct a comprehensive evaluation of the thermal performance curves of a range of mosquito and parasite traits relevant to transmission. We show that biting rate, adult mortality rate, parasite development rate, and vector competence are temperature sensitive. Importantly, we find qualitative and quantitative differences to the assumed temperature-dependent relationships. To explore the overall implications of temperature for transmission, we first use a standard model of relative vectorial capacity. This approach suggests a temperature optimum for transmission of 29°C, with minimum and maximum temperatures of 12°C and 38°C, respectively. However, the robustness of the vectorial capacity approach is challenged by the fact that the empirical data violate several of the model's simplifying assumptions. Accordingly, we present an alternative model of relative force of infection that better captures the observed biology of the vector-parasite interaction. This model suggests a temperature optimum for transmission of 26°C, with a minimum and maximum of 17°C and 35°C, respectively. The differences between the models lead to potentially divergent predictions for the potential impacts of current and future climate change on malaria transmission. The study provides a framework for more detailed, system-specific studies that are essential to develop an improved understanding on the effects of temperature on malaria transmission.

Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emuna, M.; Mayo, M.; Makov, G.

2014-03-07

Structural rearrangement of liquid Bi in the vicinity of the melting point has been proposed due to the unique temperature invariant sound velocity observed above the melting temperature, the low symmetry of Bi in the solid phase and the necessity of overheating to achieve supercooling. The existence of this structural rearrangement is examined by measurements on supercooled Bi. The sound velocity of liquid Bi was measured into the supercooled region to high accuracy and it was found to be invariant over a temperature range of ∼60°, from 35° above the melting point to ∼25° into the supercooled region. The structuralmore » origin of this phenomenon was explored by neutron diffraction structural measurements in the supercooled temperature range. These measurements indicate a continuous modification of the short range order in the melt. The structure of the liquid is analyzed within a quasi-crystalline model and is found to evolve continuously, similar to other known liquid pnictide systems. The results are discussed in the context of two competing hypotheses proposed to explain properties of liquid Bi near the melting: (i) liquid bismuth undergoes a structural rearrangement slightly above melting and (ii) liquid Bi exhibits a broad maximum in the sound velocity located incidentally at the melting temperature.« less

Adaptation to climate change--exploring the potential of locally adapted breeds.

PubMed

Hoffmann, Irene

2013-06-01

The livestock sector and agriculture as a whole face unprecedented challenges to increase production while improving the environment. On the basis of a literature review, the paper first discusses challenges related to climate change, food security and other drivers of change in livestock production. On the basis of a recent discourse in ecology, a framework for assessing livestock species' and breeds' vulnerability to climate change is presented. The second part of the paper draws on an analysis of data on breed qualities obtained from the Food and Agriculture Organization's Domestic Animal Diversity Information System (DAD-IS) to explore the range of adaptation traits present in today's breed diversity. The analysis produced a first mapping of a range of ascribed adaptation traits of national breed populations. It allowed to explore what National Coordinators understand by 'locally adapted' and other terms that describe general adaptation, to better understand the habitat, fodder and temperature range of each species and to shed light on the environments in which targeted search for adaptation traits could focus.

Effect and control on temperature measurement accuracy of the fiber- optic colorimeter by emissivity of different temperatures

NASA Astrophysics Data System (ADS)

Liu, Yu-fang; Han, Xin; Shi, De-heng

2008-03-01

Based on the Kirchhoff's Law, a practical dual-wavelength fiber-optic colorimeter, with the optimal work wavelength centered at 2.1 μm and 2.3 μm is presented. The effect of the emissivity on the precision of the measured temperature has been explored under various circumstances (i.e. temperature, wavelength) and for different materials. In addition, by fitting several typical material emissivity-temperature dependencies curves, the influence of the irradiation (radiant flux originating from the surroundings) and the surface reflected radiation on the temperature accuracy is studied. The results show that the calibration of the measured temperature for reflected radiant energy is necessary especially in low target temperature or low target emissivity, and the temperature accuracy is suitable for requirements in the range of 400-1200K.

The anthropogenic influence on heat and humidity in the US Midwest

NASA Astrophysics Data System (ADS)

Inda Diaz, H. A.; O'Brien, T. A.; Stone, D. A.

2016-12-01

Heatwaves, and extreme temperatures in general, have a wide range of negative impacts on society, and particularly on human health. In addition to temperature, humidity plays a key role in regulating human body temperature, with higher humidities tending to reduce the effectiveness of perspiration. There is recent theoretical and observational evidence that co-occurring extreme heat and humidity can potentially have a much more dramatic impact on human health than either extreme in isolation. There is an abundance of observational evidence indicating that anthropogenic increases in greenhouse gas (GHG) forcing have contributed to an increase in the intensity and frequency of temperature extremes on a global scale. However, aside from purely thermodynamically-driven increases in near-surface humidity, there is a paucity of similar evidence for anthropogenic impacts on humidity. Thermodynamic scaling would suggest that air masses originating from the ocean would be associated with higher specific humidity in a warmer world, and transpiration from irrigated crops could further increase humidity in warm air masses. In order to explore the role of anthropogenic GHG forcing on the co-occurrence of temperature and humidity extremes in the Midwestern United States (US), we evaluate a large ensemble of global climate model simulations with and without anthropogenic GHG forcing. In particular, we examine differences between the probability distributions of near-surface temperature, humidity, wet-bulb temperature, and the joint distribution of temperature and humidity in this ensemble. Finally, we explore augmenting this experimental framework with additional simulations to explore the role of anthropogenic changes in the land surface, and in particular irrigated crops, on co-occurring extreme heat and humidity.

A Temperature Sensor using a Silicon-on-Insulator (SOI) Timer for Very Wide Temperature Measurement

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad; Elbuluk, Malik; Culley, Dennis E.

2008-01-01

A temperature sensor based on a commercial-off-the-shelf (COTS) Silicon-on-Insulator (SOI) Timer was designed for extreme temperature applications. The sensor can operate under a wide temperature range from hot jet engine compartments to cryogenic space exploration missions. For example, in Jet Engine Distributed Control Architecture, the sensor must be able to operate at temperatures exceeding 150 C. For space missions, extremely low cryogenic temperatures need to be measured. The output of the sensor, which consisted of a stream of digitized pulses whose period was proportional to the sensed temperature, can be interfaced with a controller or a computer. The data acquisition system would then give a direct readout of the temperature through the use of a look-up table, a built-in algorithm, or a mathematical model. Because of the wide range of temperature measurement and because the sensor is made of carefully selected COTS parts, this work is directly applicable to the NASA Fundamental Aeronautics/Subsonic Fixed Wing Program--Jet Engine Distributed Engine Control Task and to the NASA Electronic Parts and Packaging (NEPP) Program. In the past, a temperature sensor was designed and built using an SOI operational amplifier, and a report was issued. This work used an SOI 555 timer as its core and is completely new work.

Scaled-Up Nonequilibrium Air Plasmas Generated by DC and Pulsed Discharges

DTIC Science & Technology

2010-09-08

discharges at atmospheric pressure, the rotational temperature balances with the temperature of the surrounding gas. So if we put a needle electrode ...ohmic heater to 300–973 K with an axial flow with velocity from 2 to 10 m/s. The distance between the stainless steel needle electrodes in point- to...explored 300-1000 K range. TS was operated between stainless steel pointed needle and another stainless needle electrode positioned horizontally in an

Molten Salt Thermal Energy Storage Systems

NASA Technical Reports Server (NTRS)

Maru, H. C.; Dullea, J. F.; Kardas, A.; Paul, L.; Marianowski, L. G.; Ong, E.; Sampath, V.; Huang, V. M.; Wolak, J. C.

1978-01-01

The feasibility of storing thermal energy at temperatures of 450 C to 535 C in the form of latent heat of fusion was examined for over 30 inorganic salts and salt mixtures. Alkali carbonate mixtures were chosen as phase-change storage materials in this temperature range because of their relatively high storage capacity and thermal conductivity, moderate cost, low volumetric expansion upon melting, low corrosivity, and good chemical stability. Means of improving heat conduction through the solid salt were explored.

Mixture optimization for mixed gas Joule-Thomson cycle

NASA Astrophysics Data System (ADS)

Detlor, J.; Pfotenhauer, J.; Nellis, G.

2017-12-01

An appropriate gas mixture can provide lower temperatures and higher cooling power when used in a Joule-Thomson (JT) cycle than is possible with a pure fluid. However, selecting gas mixtures to meet specific cooling loads and cycle parameters is a challenging design problem. This study focuses on the development of a computational tool to optimize gas mixture compositions for specific operating parameters. This study expands on prior research by exploring higher heat rejection temperatures and lower pressure ratios. A mixture optimization model has been developed which determines an optimal three-component mixture based on the analysis of the maximum value of the minimum value of isothermal enthalpy change, ΔhT , that occurs over the temperature range. This allows optimal mixture compositions to be determined for a mixed gas JT system with load temperatures down to 110 K and supply temperatures above room temperature for pressure ratios as small as 3:1. The mixture optimization model has been paired with a separate evaluation of the percent of the heat exchanger that exists in a two-phase range in order to begin the process of selecting a mixture for experimental investigation.

Warming reduces metabolic rate in marine snails: adaptation to fluctuating high temperatures challenges the metabolic theory of ecology.

PubMed

Marshall, David J; McQuaid, Christopher D

2011-01-22

The universal temperature-dependence model (UTD) of the metabolic theory of ecology (MTE) proposes that temperature controls mass-scaled, whole-animal resting metabolic rate according to the first principles of physics (Boltzmann kinetics). Controversy surrounds the model's implication of a mechanistic basis for metabolism that excludes the effects of adaptive regulation, and it is unclear how this would apply to organisms that live in fringe environments and typically show considerable metabolic adaptation. We explored thermal scaling of metabolism in a rocky-shore eulittoral-fringe snail (Echinolittorina malaccana) that experiences constrained energy gain and fluctuating high temperatures (between 25°C and approximately 50°C) during prolonged emersion (weeks). In contrast to the prediction of the UTD model, metabolic rate was often negatively related to temperature over a benign range (30-40°C), the relationship depending on (i) the temperature range, (ii) the degree of metabolic depression (related to the quiescent period), and (iii) whether snails were isolated within their shells. Apparent activation energies (E) varied between 0.05 and -0.43 eV, deviating excessively from the UTD's predicted range of between 0.6 and 0.7 eV. The lowering of metabolism when heated should improve energy conservation in a high-temperature environment and challenges both the theory's generality and its mechanistic basis.

Characterizing microclimate in urban malaria transmission settings: a case study from Chennai, India.

PubMed

Cator, Lauren J; Thomas, Shalu; Paaijmans, Krijn P; Ravishankaran, Sangamithra; Justin, Johnson A; Mathai, Manu T; Read, Andrew F; Thomas, Matthew B; Eapen, Alex

2013-03-02

Environmental temperature is an important driver of malaria transmission dynamics. Both the parasite and vector are sensitive to mean ambient temperatures and daily temperature variation. To understand transmission ecology, therefore, it is important to determine the range of microclimatic temperatures experienced by malaria vectors in the field. A pilot study was conducted in the Indian city of Chennai to determine the temperature variation in urban microclimates and characterize the thermal ecology of the local transmission setting. Temperatures were measured in a range of probable indoor and outdoor resting habitats of Anopheles stephensi in two urban slum malaria sites. Mean temperatures and daily temperature fluctuations in local transmission sites were compared with standard temperature measures from the local weather station. The biological implications of the different temperatures were explored using temperature-dependent parasite development models to provide estimates of the extrinsic incubation period (EIP) of Plasmodium vivax and Plasmodium falciparum. Mean daily temperatures within the urban transmission sites were generally warmer than those recorded at the local weather station. The main reason was that night-time temperatures were higher (and hence diurnal temperature ranges smaller) in the urban settings. Mean temperatures and temperature variation also differed between specific resting sites within the transmission environments. Most differences were of the order of 1-3°C but were sufficient to lead to important variation in predicted EIPs and hence, variation in estimates of transmission intensity. Standard estimates of environmental temperature derived from local weather stations do not necessarily provide realistic measures of temperatures within actual transmission environments. Even the small differences in mean temperatures or diurnal temperature ranges reported in this study can lead to large variations in key mosquito and/or parasite life history traits that determine transmission intensity. Greater effort should be directed at quantifying adult mosquito resting behaviour and determining the temperatures actually experienced by mosquitoes and parasites in local transmission environments. In the absence of such highly resolved data, the approach used in the current study provides a framework for improved thermal characterization of transmission settings.

Characterizing microclimate in urban malaria transmission settings: a case study from Chennai, India

PubMed Central

2013-01-01

Background Environmental temperature is an important driver of malaria transmission dynamics. Both the parasite and vector are sensitive to mean ambient temperatures and daily temperature variation. To understand transmission ecology, therefore, it is important to determine the range of microclimatic temperatures experienced by malaria vectors in the field. Methods A pilot study was conducted in the Indian city of Chennai to determine the temperature variation in urban microclimates and characterize the thermal ecology of the local transmission setting. Temperatures were measured in a range of probable indoor and outdoor resting habitats of Anopheles stephensi in two urban slum malaria sites. Mean temperatures and daily temperature fluctuations in local transmission sites were compared with standard temperature measures from the local weather station. The biological implications of the different temperatures were explored using temperature-dependent parasite development models to provide estimates of the extrinsic incubation period (EIP) of Plasmodium vivax and Plasmodium falciparum. Results Mean daily temperatures within the urban transmission sites were generally warmer than those recorded at the local weather station. The main reason was that night-time temperatures were higher (and hence diurnal temperature ranges smaller) in the urban settings. Mean temperatures and temperature variation also differed between specific resting sites within the transmission environments. Most differences were of the order of 1-3°C but were sufficient to lead to important variation in predicted EIPs and hence, variation in estimates of transmission intensity. Conclusions Standard estimates of environmental temperature derived from local weather stations do not necessarily provide realistic measures of temperatures within actual transmission environments. Even the small differences in mean temperatures or diurnal temperature ranges reported in this study can lead to large variations in key mosquito and/or parasite life history traits that determine transmission intensity. Greater effort should be directed at quantifying adult mosquito resting behaviour and determining the temperatures actually experienced by mosquitoes and parasites in local transmission environments. In the absence of such highly resolved data, the approach used in the current study provides a framework for improved thermal characterization of transmission settings. PMID:23452620

Evaluation of catalytic combustion of actual coal-derived gas

NASA Technical Reports Server (NTRS)

Blanton, J. C.; Shisler, R. A.

1982-01-01

The combustion characteristics of a Pt-Pl catalytic reactor burning coal-derived, low-Btu gas were investigated. A large matrix of test conditions was explored involving variations in fuel/air inlet temperature and velocity, reactor pressure, and combustor exit temperature. Other data recorded included fuel gas composition, reactor temperatures, and exhaust emissions. Operating experience with the reactor was satisfactory. Combustion efficiencies were quite high (over 95 percent) over most of the operating range. Emissions of NOx were quite high (up to 500 ppm V and greater), owing to the high ammonia content of the fuel gas.

How Warm is Mars?

NASA Technical Reports Server (NTRS)

2004-01-01

This graph shows the predicted daily change in the atmospheric temperature one meter above the surface of Mars at Gusev Crater, the Mars Exploration Rover Spirit's landing site. The blue curve denotes predicted values for sol 1 (the first day of Spirit's mission) and the yellow for sol 100 (100 days into the mission). The light blue symbols represent temperatures for a total atmospheric dust abundance of 0.7 visible optical depth units, and the darker blue symbols for a total atmospheric dust abundance of 1.0 visible optical depth units. Scientists use this data to ensure that Spirit stays within the right temperature range.

Magnetic field-temperature phase diagram of multiferroic [(CH3)2NH2] Mn (HCOO) 3

NASA Astrophysics Data System (ADS)

Clune, A. J.; Hughey, K. D.; Lee, C.; Abhyankar, N.; Ding, X.; Dalal, N. S.; Whangbo, M.-H.; Singleton, J.; Musfeldt, J. L.

2017-09-01

We combined pulsed field magnetization and first-principles spin-density calculations to reveal the magnetic field-temperature phase diagram and spin state character in multiferroic [(CH3)2NH2] Mn (HCOO) 3 . Despite similarities with the rare earth manganites, the phase diagram is analogous to other Mn-based quantum magnets with a 0.31 T spin flop, a 15.3 T transition to the fully polarized state, and short-range correlations that persist above the ordering temperature. The experimentally accessible saturation field opens the door to exploration of the high-field phase.

Whitebark pine (Pinus albicaulis) assisted migration trial

Treesearch

Sierra C. McLane; Sally N. Aitken

2011-01-01

Assisted migration - the translocation of a species into a climatically-suitable location outside of its current range - has been proposed as a means of saving vulnerable species from extinction as temperatures rise due to climate change. We explore this controversial technique using the keystone wildlife symbiote and ecosystem engineer, whitebark pine (Pinus...

Characterisation of temperature dependent parameters of multi-quantum well (MQW) Ti/Au/n-AlGaAs/n-GaAs/n-AlGaAs Schottky diodes

NASA Astrophysics Data System (ADS)

Filali, Walid; Sengouga, Nouredine; Oussalah, Slimane; Mari, Riaz H.; Jameel, Dler; Al Saqri, Noor Alhuda; Aziz, Mohsin; Taylor, David; Henini, Mohamed

2017-11-01

Forward and reverse current-voltage (Isbnd V) of Ti/Au/n-Al0.33Ga0.67As/n-GaAs/n-Al0.33Ga0.67As multi-quantum well (MQW) Schottky diodes were measured over a range of temperatures from 20 to 400 K by a step of 20 K. The Schottky diodes parameters were then extracted from these characteristics. The Cheung method is used for this purpose, assuming a thermionic conduction mechanism. The extracted ideality factor decrease with increasing temperatures. But their values at low temperatures were found to be unrealistic. In order to explain this uncertainty, three assumptions were explored. Firstly an assumed inhomogeneous barrier height gave better parameters especially the Richardson constant but the ideality factor is still unrealistic at low temperatures. Secondly, by using numerical simulation, it was demonstrated that defects including interface states are not responsible for the apparent unrealistic Schottky diode parameters. The third assumption is the tunnelling mechanism through the barrier in the low temperature range. At these lower temperatures, the tunnelling mechanism was more suitable to explain the extracted parameters values.

The temperature of unheated bodies in a high-speed gas stream

NASA Technical Reports Server (NTRS)

Eckert, E; Weise, W

1941-01-01

The present report deals with temperature measurements on cylinders of 0.2 to 3 millimeters diameter in longitudinal and transverse air flow at speeds of 100 to 300 meters per second. Within the explored test range, that is, the probable laminar boundary layer region, the temperature of the cylinders in axial flow is practically independent of the speed and in good agreement with Pohlhausen's theoretical values; Whereas, in transverse flow, cylinders of certain diameter manifest a close relationship with speed, the ratio of the temperature above the air of the body to the adiabatic stagnation temperature decreases with rising speed and then rises again from a Mach number of 0.6. The importance of this "specific temperature" of the body for heat-transfer studies at high speed is discussed.

The Mechanical Properties of Wood of Different Moisture Content Within -200 Degrees to +200 Degrees C Temperature Range

NASA Technical Reports Server (NTRS)

Kollmann, Franz

1941-01-01

Systematic experiments were undertaken with special reference to the effect of gross specific weight (specific weight inclusive of pores) and the moisture content of wood. It was found that the modules of elasticity of wood at room temperature and frozen at -8 degrees is practically the same. The effect of moisture on the compression strength of frozen wood was explored as well as the flexural and impact strength of frozen wood and frozen laminated wood.

Validation of Temperature Measurements from the Airborne Raman Ozone Temperature and Aerosol Lidar During SOLVE

NASA Technical Reports Server (NTRS)

Burris, John; McGee, Thomas; Hoegy, Walter; Lait, Leslie; Twigg, Laurence; Sumnicht, Grant; Heaps, William; Hostetler, Chris; Bui, T. Paul; Neuber, Roland;

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene

PubMed Central

Pawlak, Ryszard; Lebioda, Marcin; Rymaszewski, Jacek; Szymanski, Witold; Kolodziejczyk, Lukasz; Kula, Piotr

2016-01-01

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common −65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications—superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor). PMID:28036036

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene.

PubMed

Pawlak, Ryszard; Lebioda, Marcin; Rymaszewski, Jacek; Szymanski, Witold; Kolodziejczyk, Lukasz; Kula, Piotr

2016-12-28

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common -65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications-superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor).

Colossal dielectric permittivity in (Al + Nb) co-doped rutile SnO2 ceramics with low loss at room temperature

NASA Astrophysics Data System (ADS)

Song, Yongli; Wang, Xianjie; Zhang, Xingquan; Qi, Xudong; Liu, Zhiguo; Zhang, Lingli; Zhang, Yu; Wang, Yang; Sui, Yu; Song, Bo

2016-10-01

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Al + Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 103) and low dielectric losses (0.015 < tan δ < 0.1) in a wide range of frequencies and at temperatures from 140 to 400 K. Al doping can effectively modulate the dielectric behavior by increasing the grain and grain boundary resistances. The large differences in the resistance and conductive activation energy of the grains and grain boundaries suggest that the CP in co-doped SnO2 ceramics can be attributed to the internal barrier layer capacitor effect.

Distinct aggregation patterns and fluid porous phase in a 2D model for colloids with competitive interactions

NASA Astrophysics Data System (ADS)

Bordin, José Rafael

2018-04-01

In this paper we explore the self-assembly patterns in a two dimensional colloidal system using extensive Langevin Dynamics simulations. The pair potential proposed to model the competitive interaction have a short range length scale between first neighbors and a second characteristic length scale between third neighbors. We investigate how the temperature and colloidal density will affect the assembled morphologies. The potential shows aggregate patterns similar to observed in previous works, as clusters, stripes and porous phase. Nevertheless, we observe at high densities and temperatures a porous mesophase with a high mobility, which we name fluid porous phase, while at lower temperatures the porous structure is rigid. triangular packing was observed for the colloids and pores in both solid and fluid porous phases. Our results show that the porous structure is well defined for a large range of temperature and density, and that the fluid porous phase is a consequence of the competitive interaction and the random forces from the Langevin Dynamics.

Revisiting nucleosynthesis in globular clusters. The case of NGC 2808 and the role of He and K

NASA Astrophysics Data System (ADS)

Prantzos, N.; Charbonnel, C.; Iliadis, C.

2017-12-01

Context. Motivated by recent reports concerning the observation of limited enrichment in He but excess K in stars of globular clusters, we revisit the H-burning conditions that lead to the chemical properties of multiple stellar populations in these systems. Aims: In particular, we are interested in correlations of He and K with other elements, such as O, Na, Al, Mg and Si, reported in stars of NGC 2808. Methods: We performed calculations of nucleosynthesis at constant temperature and density, exploring the temperature range of 25 to 200 × 106 K (25 to 200 MK), using a detailed nuclear reaction network and the most up-to-date nuclear reaction rates. Results: We find that Mg is the most sensitive "thermometer" of hydrostatic H-burning conditions, pointing to a temperature range of 70-80 MK for NGC 2808, while He is a lesser - but not negligible - constraint. Potassium can be produced at the levels reported for NGC 2808 at temperatures >180 MK and Si at T > 80 MK. However, in the former temperature range Al and Na are totally destroyed and no correlation can be obtained, in contrast to the reported observations. None of the putative polluter sources proposed so far seem to satisfy the ensemble of nucleosynthesis constraints.

Traveling interface modulations and anisotropic front propagation in ammonia oxidation over Rh(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rafti, Matías; Institut für Physikalische Chemie und Elektrochemie, Leibniz-Universität Hannover, Callinstr. 3-3a, D-30167 Hannover; Borkenhagen, Benjamin

The bistable NH{sub 3} + O{sub 2} reaction over a Rh(110) surface was explored in the pressure range 10{sup −6}–10{sup −3} mbar and in the temperature range 300–900 K using photoemission electron microscopy and low energy electron microscopy as spatially resolving methods. We observed a history dependent anisotropy in front propagation, traveling interface modulations, transitions with secondary reaction fronts, and stationary island structures.

Atomization of Impinging Droplets on Superheated Superhydrophobic Surfaces

NASA Astrophysics Data System (ADS)

Emerson, Preston; Crockett, Julie; Maynes, Daniel

2017-11-01

Water droplets impinging smooth superheated surfaces may be characterized by dynamic vapor bubbles rising to the surface, popping, and causing a spray of tiny droplets to erupt from the droplet. This spray is called secondary atomization. Here, atomization is quantified experimentally for water droplets impinging superheated superhydrophobic surfaces. Smooth hydrophobic and superhydrophobic surfaces with varying rib and post microstructuring were explored. Each surface was placed on an aluminum heating block, and impingement events were captured with a high speed camera at 3000 fps. For consistency among tests, all events were normalized by the maximum atomization found over a range of temperatures on a smooth hydrophobic surface. An estimate of the level of atomization during an impingement event was created by quantifying the volume of fluid present in the atomization spray. Droplet diameter and Weber number were held constant, and atomization was found for a range of temperatures through the lifetime of the impinging droplet. The Leidenfrost temperature was also determined and defined to be the lowest temperature at which atomization ceases to occur. Both atomization and Leidenfrost temperature increase with decreasing pitch (distance between microstructures).

Kinetics of silicide formation over a wide range of heating rates spanning six orders of magnitude

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molina-Ruiz, Manel; Lopeandía, Aitor F.; Gonzalez-Silveira, Marta

Kinetic processes involving intermediate phase formation are often assumed to follow an Arrhenius temperature dependence. This behavior is usually inferred from limited data over narrow temperature intervals, where the exponential dependence is generally fully satisfied. However, direct evidence over wide temperature intervals is experimentally challenging and data are scarce. Here, we report a study of silicide formation between a 12 nm film of palladium and 15 nm of amorphous silicon in a wide range of heating rates, spanning six orders of magnitude, from 0.1 to 10{sup 5 }K/s, or equivalently more than 300 K of variation in reaction temperature. The calorimetric traces exhibit severalmore » distinct exothermic events related to interdiffusion, nucleation of Pd{sub 2}Si, crystallization of amorphous silicon, and vertical growth of Pd{sub 2}Si. Interestingly, the thickness of the initial nucleation layer depends on the heating rate revealing enhanced mass diffusion at the fastest heating rates during the initial stages of the reaction. In spite of this, the formation of the silicide strictly follows an Arrhenius temperature dependence over the whole temperature interval explored. A kinetic model is used to fit the calorimetric data over the complete heating rate range. Calorimetry is complemented by structural analysis through transmission electron microscopy and both standard and in-situ synchrotron X-ray diffraction.« less

Li-Ion Cells Employing Electrolytes With Methyl Propionate and Ethyl Butyrate Co-Solvents

NASA Technical Reports Server (NTRS)

Smart, Marshall C.; Bugga, Ratnakumar V.

2011-01-01

Future NASA missions aimed at exploring Mars and the outer planets require rechargeable batteries that can operate at low temperatures to satisfy the requirements of such applications as landers, rovers, and penetrators. A number of terrestrial applications, such as hybrid electric vehicles (HEVs) and electric vehicles (EVs) also require energy storage devices that can operate over a wide temperature range (i.e., -40 to +70 C), while still providing high power capability and long life. Currently, the state-of-the-art lithium-ion system has been demonstrated to operate over a wide range of temperatures (-30 to +40 C); however, the rate capability at the lower temperatures is very poor. These limitations at very low temperatures are due to poor electrolyte conductivity, poor lithium intercalation kinetics over the electrode surface layers, and poor ionic diffusion in the electrode bulk. Two wide-operating-temperature-range electrolytes have been developed based on advances involving lithium hexafluorophosphate-based solutions in carbonate and carbonate + ester solvent blends, which have been further optimized in the context of the technology and targeted applications. The approaches employed include further optimization of electrolytes containing methyl propionate (MP) and ethyl butyrate (EB), which are effective co-solvents, to widen the operating temperature range beyond the baseline systems. Attention was focused on further optimizing ester-based electrolyte formulations that have exhibited the best performance at temperatures ranging from -60 to +60 C, with an emphasis upon improving the rate capability at -20 to -40 C. This was accomplished by increasing electrolyte salt concentration to 1.20M and increasing the ester content to 60 percent by volume to increase the ionic conductivity at low temperatures. Two JPL-developed electrolytes 1.20M LiPF6 in EC+EMC+MP (20:20:60 v/v %) and 1.20M LiPF6 in EC+EMC+EB (20:20:60 v/v %) operate effectively over a wide temperature range in MCMB-LiNiCoAlO2 and Li4Ti5O12-LiNi-CoAlO2 prototype cells. These electrolytes have enabled high rate performance at low temperature (i.e., up to 2.0C rates at -50 C and 5.0C rates at -40 C), and good cycling performance over a wide temperature range (i.e., from -40 to +70 C). Current efforts are focused upon improving the high temperature resilience of the methyl propionatebased system through the use of electrolyte additives, which are envisioned to improve the nature of the solid electrolyte interphase (SEI) layers.

Bill size variation in northern cardinals associated with anthropogenic drivers across North America.

PubMed

Miller, Colleen R; Latimer, Christopher E; Zuckerberg, Benjamin

2018-05-01

Allen's rule predicts that homeotherms inhabiting cooler climates will have smaller appendages, while those inhabiting warmer climates will have larger appendages relative to body size. Birds' bills tend to be larger at lower latitudes, but few studies have tested whether modern climate change and urbanization affect bill size. Our study explored whether bill size in a wide-ranging bird would be larger in warmer, drier regions and increase with rising temperatures. Furthermore, we predicted that bill size would be larger in densely populated areas, due to urban heat island effects and the higher concentration of supplementary foods. Using measurements from 605 museum specimens, we explored the effects of climate and housing density on northern cardinal bill size over an 85-year period across the Linnaean subspecies' range. We quantified the geographic relationships between bill surface area, housing density, and minimum temperature using linear mixed effect models and geographically weighted regression. We then tested whether bill surface area changed due to housing density and temperature in three subregions (Chicago, IL., Washington, D.C., and Ithaca, NY). Across North America, cardinals occupying drier regions had larger bills, a pattern strongest in males. This relationship was mediated by temperature such that birds in warm, dry areas had larger bills than those in cool, dry areas. Over time, female cardinals' bill size increased with warming temperatures in Washington, D.C., and Ithaca. Bill size was smaller in developed areas of Chicago, but larger in Washington, D.C., while there was no pattern in Ithaca, NY. We found that climate and urbanization were strongly associated with bill size for a wide-ranging bird. These biogeographic relationships were characterized by sex-specific differences, varying relationships with housing density, and geographic variability. It is likely that anthropogenic pressures will continue to influence species, potentially promoting microevolutionary changes over space and time.

The interrelationship between dengue incidence and diurnal ranges of temperature and humidity in a Sri Lankan city and its potential applications

PubMed Central

Ehelepola, N. D. B.; Ariyaratne, Kusalika

2015-01-01

Background Temperature, humidity, and other weather variables influence dengue transmission. Published studies show how the diurnal fluctuations of temperature around different mean temperatures influence dengue transmission. There are no published studies about the correlation between diurnal range of humidity and dengue transmission. Objective The goals of this study were to determine the correlation between dengue incidence and diurnal fluctuations of temperature and humidity in the Sri Lankan city of Kandy and to explore the possibilities of using that information for better control of dengue. Design We calculated the weekly dengue incidence in Kandy during the period 2003–2012, after collecting data on all of the reported dengue patients and estimated midyear populations. Data on daily maximum and minimum temperatures and night-time and daytime humidity were obtained from two weather stations, averaged, and converted into weekly data. The number of days per week with a diurnal temperature range (DTR) of >10°C and <10°C and the number of days per week with a diurnal humidity range (DHR) of >20 and <15% were calculated. Wavelet time series analysis was performed to determine the correlation between dengue incidence and diurnal ranges of temperature and humidity. Results There were negative correlations between dengue incidence and a DTR >10°C and a DHR >20% with 3.3-week and 4-week lag periods, respectively. Additionally, positive correlations between dengue incidence and a DTR <10°C and a DHR <15% with 3- and 4-week lag periods, respectively, were discovered. Conclusions These findings are consistent with the results of previous entomological studies and theoretical models of DTR and dengue transmission correlation. It is important to conduct similar studies on diurnal fluctuations of humidity in the future. We suggest ways and means to use this information for local dengue control and to mitigate the potential effects of the ongoing global reduction of DTR on dengue incidence. PMID:26632645

Polar Lunar Regions: Exploiting Natural and Augmented Thermal Environments

NASA Technical Reports Server (NTRS)

Ryan, Robert E.; McKellip, Rodney; Brannon, David P.; Underwood, Lauren; Russell, Kristen J.

2007-01-01

In polar regions of the Moon, some areas within craters are permanently shadowed from solar illumination and can reach temperatures of 100 K or less. These regions could serve as cold traps, capturing ice and other volatile compounds. These potential ice stores have many applications for lunar exploration. Within double-shaded craters, even colder regions exist, with temperatures never exceeding 50 K in many cases. Observed temperatures suggest that these regions could enable equivalent liquid nitrogen cryogenic functions. These permanently shaded polar craters also offer unprecedented high-vacuum cryogenic environments, which in their current state could support cryogenic applications. Besides ice stores, the unique conditions at the lunar poles harbor an environment that provides an opportunity to reduce the power, weight, and total mass that needs to be carried from the Earth to the Moon for lunar exploration and research. Reducing the heat flux of geothermal, black body radiation can have significant impacts on the achievable temperature. With a few manmade augmentations, permanently shaded craters located near the lunar poles achieve temperatures even lower than those that naturally exist. Our analysis reveals that lightweight thermal shielding within shaded craters could create an environment several Kelvin above absolute zero. The temperature ranges of both naturally shaded and thermally augmented craters could enable the long-term storage of most gases, low-temperature superconductors for large magnetic fields, devices and advanced high-speed computing instruments. Augmenting thermal conditions in these craters could then be used as a basis for the development of an advanced thermal management architecture that would support a wide variety of cryogenically based applications. Lunar exploration and habitation capabilities would significantly benefit if permanently shaded craters, augmented with thermal shielding, were used to facilitate the operation of near absolute zero instruments, including a wide variety of cryogenically based propulsion, energy, communication, sensing, and computing devices. The required burden of carrying massive life-supporting components from the Earth to the Moon for lunar exploration and research potentially could be reduced.

Projecting potential adoption of genetically engineered freeze-tolerant Eucalyptus in the United States

Treesearch

David N. Wear; Ernest Dixon IV; Robert C. Abt; Navinder Singh

2015-01-01

Development of commercial Eucalyptus plantations has been limited in the United States because of the species’ sensitivity to freezing temperatures. Recently developed genetically engineered clones of a Eucalyptus hybrid, which confer freeze tolerance, could expand the range of commercial plantations. This study explores how...

Portable Cathode-Air Vapor-Feed Electrochemical Medical Oxygen Concentrator (OC)

NASA Technical Reports Server (NTRS)

Balasubramanian, Ashwin

2015-01-01

Missions on the International Space Station and future space exploration will present significant challenges to crew health care capabilities, particularly in the efficient utilization of onboard oxygen resources. Exploration vehicles will require lightweight, compact, and portable oxygen concentrators that can provide medical-grade oxygen from the ambient cabin air. Current pressure-swing adsorption OCs are heavy and bulky, require significant start-up periods, operate in narrow temperature ranges, and require a liquid water feed. Lynntech, Inc., has developed an electrochemical OC that operates with a cathode-air vapor feed, eliminating the need for a bulky onboard water supply. Lynntech's OC is smaller and lighter than conventional pressure-swing OCs, is capable of instant start-up, and operates over a temperature range of 5-80 C. Accomplished through a unique nanocomposite proton exchange membrane and catalyst technology, the unit delivers 4 standard liters per minute of humidified oxygen at 60 percent concentration. The technology enables both ambient-pressure operating devices for portable applications and pressurized (up to 3,600 psi) OC devices for stationary applications.

Adaptive phenotypic plasticity and local adaptation for temperature tolerance in freshwater zooplankton

PubMed Central

Yampolsky, Lev Y.; Schaer, Tobias M. M.; Ebert, Dieter

2014-01-01

Many organisms have geographical distributions extending from the tropics to near polar regions or can experience up to 30°C temperature variation within the lifespan of an individual. Two forms of evolutionary adaptation to such wide ranges in ambient temperatures are frequently discussed: local adaptation and phenotypic plasticity. The freshwater planktonic crustacean Daphnia magna, whose range extends from South Africa to near arctic sites, shows strong phenotypic and genotypic variation in response to temperature. In this study, we use D. magna clones from 22 populations (one clone per population) ranging from latitude 0° (Kenya) to 66° North (White Sea) to explore the contributions of phenotypic plasticity and local adaptation to high temperature tolerance. Temperature tolerance was studied as knockout time (time until immobilization, Timm) at 37°C in clones acclimatized to either 20°C or 28°C. Acclimatization to 28°C strongly increased Timm, testifying to adaptive phenotypic plasticity. At the same time, Timm significantly correlated with average high temperature at the clones’ sites of origin, suggesting local adaptation. As earlier studies have found that haemoglobin expression contributes to temperature tolerance, we also quantified haemoglobin concentration in experimental animals and found that both acclimatization temperature (AccT) and temperature at the site of origin are positively correlated with haemoglobin concentration. Furthermore, Daphnia from warmer climates upregulate haemoglobin much more strongly in response to AccT, suggesting local adaptation for plasticity in haemoglobin expression. Our results show that both local adaptation and phenotypic plasticity contribute to temperature tolerance, and elucidate a possible role of haemoglobin in mediating these effects that differs along a cold–warm gradient. PMID:24352948

Nonlinear dynamics of the CAM circadian rhythm in response to environmental forcing.

PubMed

Hartzell, Samantha; Bartlett, Mark S; Virgin, Lawrence; Porporato, Amilcare

2015-03-07

Crassulacean acid metabolism (CAM) photosynthesis functions as an endogenous circadian rhythm coupled to external environmental forcings of energy and water availability. This paper explores the nonlinear dynamics of a new CAM photosynthesis model (Bartlett et al., 2014) and investigates the responses of CAM plant carbon assimilation to different combinations of environmental conditions. The CAM model (Bartlett et al., 2014) consists of a Calvin cycle typical of C3 plants coupled to an oscillator of the type employed in the Van der Pol and FitzHugh-Nagumo systems. This coupled system is a function of environmental variables including leaf temperature, leaf moisture potential, and irradiance. Here, we explore the qualitative response of the system and the expected carbon assimilation under constant and periodically forced environmental conditions. The model results show how the diurnal evolution of these variables entrains the CAM cycle with prevailing environmental conditions. While constant environmental conditions generate either steady-state or periodically oscillating responses in malic acid uptake and release, forcing the CAM system with periodic daily fluctuations in light exposure and leaf temperature results in quasi-periodicity and possible chaos for certain ranges of these variables. This analysis is a first step in quantifying changes in CAM plant productivity with variables such as the mean temperature, daily temperature range, irradiance, and leaf moisture potential. Results may also be used to inform model parametrization based on the observed fluctuating regime. Copyright © 2014 Elsevier Ltd. All rights reserved.

Magnetic exploration of a low-temperature ultramafic-hosted hydrothermal site (Lost City, 30°N, MAR)

NASA Astrophysics Data System (ADS)

Szitkar, Florent; Tivey, Maurice A.; Kelley, Deborah S.; Karson, Jeffrey A.; Früh-Green, Gretchen L.; Denny, Alden R.

2017-03-01

A 2003 high-resolution magnetic survey conducted by the Autonomous Underwater Vehicle ABE over the low-temperature, ultramafic-hosted hydrothermal field Lost City reveals a weak positive magnetic anomaly. This observation is in direct contrast to recent observations of strong positive magnetic anomalies documented over the high-temperature ultramafic-hosted hydrothermal vents fields Rainbow and Ashadze, which indicates that temperature may control the production of magnetization at these sites. The Lost City survey provides a unique opportunity to study a field that is, to date, one of a kind, and is an end member of ultramafic-hosted hydrothermal systems. Our results highlight the key contribution of temperature on magnetite production resulting from serpentinization reactions. Whereas high temperature promotes significant production and partitioning of iron into magnetite, low temperature favors iron partitioning into various alteration phases, resulting in a magnetite-poor rock. Moreover, the distribution of magnetic anomalies confirms results of a previous geological survey indicating the progressive migration of hydrothermal activity upslope. These discoveries contribute to the results of 25 yrs of magnetic exploration of a wide range of hydrothermal sites, from low- to high-temperature and from basalt- to ultramafic-hosted, and thereby validate using high-resolution magnetics as a crucial parameter for locating and characterizing hydrothermal sites hosting unique chemosynthetic-based ecosystems and potentially mineral-rich deposits.

Cryogenic Refractive Indices of S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14 Glasses

NASA Technical Reports Server (NTRS)

Miller, Kevin H.; Quijada, Manuel A.; Leviton, Doug

2015-01-01

The Transiting Exoplanet Survey Satellite (TESS) is an explorer-class planet finder, whose principal goal is to detect small planets with bright host starts in the solar neighborhood. The TESS payload consists of four identical cameras with seven optical elements each that include various types of Ohara glass substrates. The successful implementation both panchromatic and thermal lens assembly designs for these cameras requires a fairly accurate (up to 1E-6) knowledge of the temperature and wavelength dependence of the refractive index in the wavelength and temperature range of operation. Hence, this paper is devoted to report on measurements of the refractive index over the wavelength range of 0.42-1.15 um and temperature range of 110-310 K for the following Ohara glasses: S-LAH55, S-LAH55V, SLAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14. The measurements were performed utilizing the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at NASA's Goddard Space Flight Center. A dense coverage of the absolute refractive index for the title substrates in the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dn/dT) and dispersion relation (dn/d lambda) as a function of wavelength and temperature. A comparison of the measured indices with literature values, specifically the temperature-dependent refractive indices of S-PHM52 and S-TIH14, will be presented.

Elevated surface temperature depresses survival of banner-tailed kangaroo rats: will climate change cook a desert icon?

PubMed

Moses, Martin R; Frey, Jennifer K; Roemer, Gary W

2012-01-01

Modest increases in global temperature have been implicated in causing population extirpations and range shifts in taxa inhabiting colder environs and in ectotherms whose thermoregulation is more closely tied to environmental conditions. Many arid-adapted endotherms already experience conditions at their physiological limits, so it is conceivable that they could be similarly affected by warming temperatures. We explored how climatic variables might influence the apparent survival of the banner-tailed kangaroo rat (Dipodomys spectabilis), a rodent endemic to the Chihuahuan Desert of North America and renowned for its behavioral and physiological adaptations to arid environments. Relative variable weight, strength of variable relationships, and other criteria indicated that summer, diurnal land surface temperature (SD_LST) was the primary environmental driver of apparent survival in these arid-adapted rodents. Higher temperatures had a negative effect on apparent survival, which ranged from 0.15 (SE = 0.04) for subadults to 0.50 (SE = 0.07) for adults. Elevated SD_LST may negatively influence survival through multiple pathways, including increased water loss and energy expenditure that could lead to chronic stress and/or hyperthermia that could cause direct mortality. Land surface temperatures are predicted to increase by as much 6.5°C by 2099, reducing apparent survival of adults to ~0.15 in some regions of the species' range, possibly causing a shift in their distribution. The relationship between SD_LST and survival suggests a mechanism whereby physiological tolerances are exceeded resulting in a reduction to individual fitness that may ultimately cause a shift in the species' range over time.

High Throughput Differential Scanning Fluorimetry (DSF) Formulation Screening with Complementary Dyes to Assess Protein Unfolding and Aggregation in Presence of Surfactants.

PubMed

McClure, Sean M; Ahl, Patrick L; Blue, Jeffrey T

2018-03-05

The purpose was to evaluate DSF for high throughput screening of protein thermal stability (unfolding/ aggregation) across a wide range of formulations. Particular focus was exploring PROTEOSTAT® - a commercially available fluorescent rotor dye - for detection of aggregation in surfactant containing formulations. Commonly used hydrophobic dyes (e.g. SYPRO™ Orange) interact with surfactants, complicating DSF measurements. CRM197 formulations were prepared and analyzed in standard 96-well plate rT-PCR system, using SYPRO™ Orange and PROTEOSTAT® dyes. Orthogonal techniques (DLS and IPF) are employed to confirm unfolding/aggregation in selected formulations. Selected formulations are subjected to non-thermal stresses (stirring and shaking) in plate based format to characterize aggregation with PROTEOSTAT®. Agreement is observed between SYPRO™ Orange (unfolding) and PROTEOSTAT® (aggregation) DSF melt temperatures across wide range of non-surfactant formulations. PROTEOSTAT® can clearly detect temperature induced aggregation in low concentration (0.2 mg/mL) CRM197 formulations containing surfactant. PROTEOSTAT® can be used to explore aggregation due to non-thermal stresses in plate based format amenable to high throughput screening. DSF measurements with complementary extrinsic dyes (PROTEOSTAT®, SYPRO™ Orange) are suitable for high throughput screening of antigen thermal stability, across a wide range of relevant formulation conditions - including surfactants -with standard, plate based rT-PCR instrumentation.

Performance of High Temperature Operational Amplifier, Type LM2904WH, under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad; Elbuluk, Malik

2008-01-01

Operation of electronic parts and circuits under extreme temperatures is anticipated in NASA space exploration missions as well as terrestrial applications. Exposure of electronics to extreme temperatures and wide-range thermal swings greatly affects their performance via induced changes in the semiconductor material properties, packaging and interconnects, or due to incompatibility issues between interfaces that result from thermal expansion/contraction mismatch. Electronics that are designed to withstand operation and perform efficiently in extreme temperatures would mitigate risks for failure due to thermal stresses and, therefore, improve system reliability. In addition, they contribute to reducing system size and weight, simplifying its design, and reducing development cost through the elimination of otherwise required thermal control elements for proper ambient operation. A large DC voltage gain (100 dB) operational amplifier with a maximum junction temperature of 150 C was recently introduced by STMicroelectronics [1]. This LM2904WH chip comes in a plastic package and is designed specifically for automotive and industrial control systems. It operates from a single power supply over a wide range of voltages, and it consists of two independent, high gain, internally frequency compensated operational amplifiers. Table I shows some of the device manufacturer s specifications.

Comprehensive Evaluation of Power Supplies at Cryogenic Temperatures for Deep Space Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Gerber, Scott; Hammoud, Ahmad; Elbuluk, Malik E.; Lyons, Valerie (Technical Monitor)

2002-01-01

The operation of power electronic systems at cryogenic temperatures is anticipated in many future space missions such as planetary exploration and deep space probes. In addition to surviving the space hostile environments, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. DC/DC converters are widely used in space power systems in the areas of power management, conditioning, and control. As part of the on-going Low Temperature Electronics Program at NASA, several commercial-off-the-shelf (COTS) DC/DC converters, with specifications that might fit the requirements of specific future space missions have been selected for investigation at cryogenic temperatures. The converters have been characterized in terms of their performance as a function of temperature in the range of 20 C to - 180 C. These converters ranged in electrical power from 8 W to 13 W, input voltage from 9 V to 72 V and an output voltage of 3.3 V. The experimental set-up and procedures along with the results obtained on the converters' steady state and dynamic characteristics are presented and discussed.

An Information-theoretic Approach to Optimize JWST Observations and Retrievals of Transiting Exoplanet Atmospheres

NASA Astrophysics Data System (ADS)

Howe, Alex R.; Burrows, Adam; Deming, Drake

2017-01-01

We provide an example of an analysis to explore the optimization of observations of transiting hot Jupiters with the James Webb Space Telescope (JWST) to characterize their atmospheres based on a simple three-parameter forward model. We construct expansive forward model sets for 11 hot Jupiters, 10 of which are relatively well characterized, exploring a range of parameters such as equilibrium temperature and metallicity, as well as considering host stars over a wide range in brightness. We compute posterior distributions of our model parameters for each planet with all of the available JWST spectroscopic modes and several programs of combined observations and compute their effectiveness using the metric of estimated mutual information per degree of freedom. From these simulations, clear trends emerge that provide guidelines for designing a JWST observing program. We demonstrate that these guidelines apply over a wide range of planet parameters and target brightnesses for our simple forward model.

Winter range expansion of a hummingbird is associated with urbanization and supplementary feeding

PubMed Central

Wood, Eric M.

2017-01-01

Anthropogenic changes to the landscape and climate cause novel ecological and evolutionary pressures, leading to potentially dramatic changes in the distribution of biodiversity. Warm winter temperatures can shift species' distributions to regions that were previously uninhabitable. Further, urbanization and supplementary feeding may facilitate range expansions and potentially reduce migration tendency. Here we explore how these factors interact to cause non-uniform effects across a species's range. Using 17 years of data from the citizen science programme Project FeederWatch, we examined the relationships between urbanization, winter temperatures and the availability of supplementary food (i.e. artificial nectar) on the winter range expansion (more than 700 km northward in the past two decades) of Anna's hummingbirds (Calypte anna). We found that Anna's hummingbirds have colonized colder locations over time, were more likely to colonize sites with higher housing density and were more likely to visit feeders in the expanded range compared to the historical range. Additionally, their range expansion mirrored a corresponding increase over time in the tendency of people to provide nectar feeders in the expanded range. This work illustrates how humans may alter the distribution and potentially the migratory behaviour of species through landscape and resource modification. PMID:28381617

Limits to global and Australian temperature change this century based on expert judgment of climate sensitivity

NASA Astrophysics Data System (ADS)

Grose, Michael R.; Colman, Robert; Bhend, Jonas; Moise, Aurel F.

2017-05-01

The projected warming of surface air temperature at the global and regional scale by the end of the century is directly related to emissions and Earth's climate sensitivity. Projections are typically produced using an ensemble of climate models such as CMIP5, however the range of climate sensitivity in models doesn't cover the entire range considered plausible by expert judgment. Of particular interest from a risk-management perspective is the lower impact outcome associated with low climate sensitivity and the low-probability, high-impact outcomes associated with the top of the range. Here we scale climate model output to the limits of expert judgment of climate sensitivity to explore these limits. This scaling indicates an expanded range of projected change for each emissions pathway, including a much higher upper bound for both the globe and Australia. We find the possibility of exceeding a warming of 2 °C since pre-industrial is projected under high emissions for every model even scaled to the lowest estimate of sensitivity, and is possible under low emissions under most estimates of sensitivity. Although these are not quantitative projections, the results may be useful to inform thinking about the limits to change until the sensitivity can be more reliably constrained, or this expanded range of possibilities can be explored in a more formal way. When viewing climate projections, accounting for these low-probability but high-impact outcomes in a risk management approach can complement the focus on the likely range of projections. They can also highlight the scale of the potential reduction in range of projections, should tight constraints on climate sensitivity be established by future research.

Report on Lithium Ion Battery Trade Studies to Support the Exploration Technology Development Program (ETDP) Energy Storage Project

NASA Technical Reports Server (NTRS)

Green, Robert D.; Kissock, Barbara I.; Bennett, William R.

2010-01-01

This report documents the results of two system related analyses to support the Exploration Technology Development Program (ETDP) Energy Storage Project. The first study documents a trade study to determine the optimum Li-ion battery cell capacity for the ascent stage battery for the Altair lunar lander being developed under the Constellation Systems program. The battery cell capacity for the Ultra High Energy (UHE) Li-ion battery initially chosen as the target for development was 35 A-hr; this study concludes that a 19.4 A-hr cell capacity would be more optimum from a minimum battery mass perspective. The second study in this report is an assessment of available low temperature Li-ion battery cell performance data to determine whether lowering the operating temperature range of the Li-ion battery, in a rover application, could save overall system mass by eliminating thermal control system mass normally needed to maintain battery temperature within a tighter temperature limit than electronics or other less temperature sensitive components. The preliminary assessment for this second study indicates that the reduction in the thermal control system mass is negated by an increase in battery mass to compensate for the loss in battery capacity due to lower temperature operating conditions.

Operation of a New COTS Crystal Oscillator - CXOMHT over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2011-01-01

Crystal oscillators are extensively used in electronic circuits to provide timing or clocking signals in data acquisition, communications links, and control systems, to name a few. They are affordable, small in size, and reliable. Because of the inherent characteristics of the crystal, the oscillator usually exhibits extreme accuracy in its output frequency within the intrinsic crystal stability. Stability of the frequency could be affected under varying load levels or other operational conditions. Temperature is one of those important factors that influence the frequency stability of an oscillator; as it does to the functionality of other electronic components. Electronics designed for use in NASA deep space and planetary exploration missions are expected to be exposed to extreme temperatures and thermal cycling over a wide range. Thus, it is important to design and develop circuits that are able to operate efficiently and reliably under in these harsh temperature environments. Most of the commercial-off-the-shelf (COTS) devices are very limited in terms of their specified operational temperature while very few custom-made commercial and military-grade parts have the ability to operate in a slightly wider range of temperature than those of the COTS parts. These parts are usually designed for operation under one temperature extreme, i.e. hot or cold, and do not address the wide swing in the operational temperature, which is typical of the space environment. For safe and successful space missions, electronic systems must therefore be designed not only to withstand the extreme temperature exposure but also to operate efficiently and reliably. This report presents the results obtained on the evaluation of a new COTS crystal oscillator under extreme temperatures.

Quantum tunneling of oxygen atoms on very cold surfaces.

PubMed

Minissale, M; Congiu, E; Baouche, S; Chaabouni, H; Moudens, A; Dulieu, F; Accolla, M; Cazaux, S; Manicó, G; Pirronello, V

2013-08-02

Any evolving system can change state via thermal mechanisms (hopping a barrier) or via quantum tunneling. Most of the time, efficient classical mechanisms dominate at high temperatures. This is why an increase of the temperature can initiate the chemistry. We present here an experimental investigation of O-atom diffusion and reactivity on water ice. We explore the 6-25 K temperature range at submonolayer surface coverages. We derive the diffusion temperature law and observe the transition from quantum to classical diffusion. Despite the high mass of O, quantum tunneling is efficient even at 6 K. As a consequence, the solid-state astrochemistry of cold regions should be reconsidered and should include the possibility of forming larger organic molecules than previously expected.

A nonlinear high temperature fracture mechanics basis for strainrange partitioning

NASA Technical Reports Server (NTRS)

Kitamura, Takayuki; Halford, Gary R.

1989-01-01

A direct link was established between Strainrange Partitioning (SRP) and high temperature fracture mechanics by deriving the general SRP inelastic strain range versus cyclic life relationships from high temperature, nonlinear, fracture mechanics considerations. The derived SRP life relationships are in reasonable agreement based on the experience of the SRP behavior of many high temperature alloys. In addition, fracture mechanics has served as a basis for derivation of the Ductility-Normalized SRP life equations, as well as for examination of SRP relations that are applicable to thermal fatigue life prediction. Areas of additional links between nonlinear fracture mechanics and SRP were identified for future exploration. These include effects of multiaxiality as well as low strain, nominally elastic, long life creep fatigue interaction.

Temperature Measurements in the Solar Transition Region Using N III Line Intensity Ratios

NASA Technical Reports Server (NTRS)

Doron, R.; Doschek, G. A.; Laming, J. M.; Feldman, U.; Bhatia, A. K.

2003-01-01

UV emission from B-like N and O ions a rather rare opportunity for recording spectral lines in a narrow wavelength range that can potentially be used to derive temperatures relevant to the solar transition region. In these ions, the line intensity ratios of the type (2s2p(sup 2) - 2p(sup 3)) / (2s(sup 2)2p - 2s2p(sup 2)) are very sensitive to the electron temperature. Additionally, the lines involving the ratios fall within a range of only - 12 A; in N III the lines fall in the 980 - 992 A range and in O IV in the 780 - 791 A range. In this work, we explore the use of these atomic systems, primarily in N III, for temperature diagnostics of the transition region by analyzing UV spectra obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO). The N III temperature-sensitive line ratios are measured in more than 60 observations. Most of the measured ratios correspond to temperatures in the range 5.7x10(exp 4) - 6.7x10(exp 4) K. This range is considerably lower than the calculated temperature of maximum abundance of N III, which is approx. 7.6x10(exp 4) K. Detailed analysis of the spectra further indicates that the measured ratios are probably somewhat overestimated due to resonant scattering effects in the 2s(sup 2)2p - 2s2p(sup 2) lines and small blends in the 2s2p(sup 2) - 2p3 lines. Actual lower ratios would only increase the disagreement between the ionization balance calculations and present temperature measurements based on a collisional excitation model. In the case of the O IV spectra, we determined that due to the close proximity in wavelength of the weak line (2s2p(sup 2)-2p3 transitions) to a strong Ne VIII line, sufficiently accurate ratio measurements cannot be obtained. Subject headings: atomic data --- atomic processes --- Sun: transition region --- Sun: U V radiation --- techniques: spectroscopic

The role of latitudinal, genetic and temperature variation in the induction of diapause of Papilio glaucus (Lepidoptera: Papilionidae).

PubMed

Ryan, Sean F; Valella, Patti; Thivierge, Gabrielle; Aardema, Matthew L; Scriber, J Mark

2018-04-01

A key adaptation in insects for dealing with variable environmental conditions is the ability to diapause. The tiger swallowtail butterflies, Papilio glaucus and P. canadensis are ideal species to explore the genetic causes and population genetic consequences of diapause because divergence in this trait is believed to be a salient factor in maintaining a hybrid zone between these species. Yet little is known about the factors that influence diapause induction in this system. Here we explored how spatial (latitudinal), environmental (temperature) and genetic (hybridization) factors affect diapause induction in this system. Specifically, a series of growth chamber experiments using wild caught individuals from across the eastern United States were performed to: (1) evaluate how critical photoperiod varies with latitude, (2) isolate the stage in which induction occurs, (3) test whether changes in temperature affected rates of diapause induction, and (4) explore how the incidence of diapause is affected in hybrid offspring. We find that induction occurs in the larval stage, is not sensitive to a relatively broad range of temperatures, appears to have a complex genetic basis (i.e., is not simply a dominant trait following a Mendelian inheritance pattern) and that the critical photoperiod increases by 0.4 h with each increasing degree in latitude. This work deepens our understanding of how spatial, environmental and genetic variation influences a key seasonal adaptation (diapause induction) in a well-developed ecological model system and will make possible future studies that explore how climatic variation affects the population dynamics and genetics of this system. © 2016 Institute of Zoology, Chinese Academy of Sciences.

Triton's surface-atmosphere energy balance

USGS Publications Warehouse

Stansberry, J.A.; Yelle, R.V.; Lunine, J.I.; McEwen, A.S.

1992-01-01

We explore the energetics of Triton's surface-atmosphere system using a model that includes the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport. The model relies on a 1?? by 1?? resolution hemispheric bolometric albedo map of Triton for determining the atmospheric temperature, the N2 frost emissivity, and the temperatures of unfrosted portions of the surface consistent with a frost temperature of ???38 K. For a physically plausible range of heat transfer coefficients, we find that the atmospheric temperature roughly 1 km above the surface is approximately 1 to 3 K hotter than the surface. Atmospheric temperatures of 48 K suggested by early analysis of radio occultation data cannot be obtained for plausible values of the heat transfer coefficients. Our calculations indicate that Triton's N2 frosts must have an emissivity well below unity in order to have a temperature of ???38 K, consistent with previous results. We also find that convection over small hot spots does not significantly cool them off, so they may be able to act as continous sources of buoyancy for convective plumes, but have not explored whether the convection is vigorous enough to entrain particulate matter thereby forming a dust devil. Our elevated atmospheric temperatures make geyser driven plumes with initial upward velocities ???10 m s-1 stagnate in the lower atmosphere. These "wimpy" plumes provide a possible explanation for Triton's "wind streaks.". ?? 1992.

The Effect of Composition on Diffusion of Au in Fe and Fe-Ni Alloys

NASA Astrophysics Data System (ADS)

Johanesen, K. E.; Watson, H. C.; Fei, Y.

2005-12-01

Understanding siderophile element diffusion in Fe-Ni alloys will lead to tighter constraints on processes such as meteoritic body cooling rates, and inner core-outer core communication. Recent studies have determined the effect of temperature and pressure on diffusion in this system, but the effect of composition has not yet been explored adequately. The effect of Ni content on Au diffusion in an Fe-Ni system was explored for Fe-Ni alloys with concentrations of 0, 20, and 30 wt. % Ni. Diffusion couple experiments were conducted using a piston cylinder press at 1 GPa and temperatures ranging from 1150°C to 1400°C. Concentration profiles were measured by electron microprobe and were fitted to the linear diffusion solution for an semi-infinite diffusion couple to extract diffusion coefficients (D) using a non-linear least squares fit routine. As predicted, D increases with Ni content and also with temperature. The diffusivities ranged from 2.06×10-9 at 1150°C to 5.76×10-8 at 1350°C for 0 wt. % Ni; 5.17×10-9 at 1150° C to 1.93×10-7 at 1400°C for 20 wt. % Ni; and 2.41×10-8 at 1150°C to 2.13×10-7 at 1400°C for 30 wt. % Ni. As temperature increases, the effect of Ni on diffusion rates increases, implying a possible change in diffusion mechanism between 1250°C and 1300°C. Ni appears to have a negligible effect at lower temperatures, which would indicate that Ni may not need to be considered when modeling siderophile trace element diffusion rates in iron meteorites.

Cardiac function in an endothermic fish: cellular mechanisms for overcoming acute thermal challenges during diving

PubMed Central

Shiels, H. A.; Galli, G. L. J.; Block, B. A.

2015-01-01

Understanding the physiology of vertebrate thermal tolerance is critical for predicting how animals respond to climate change. Pacific bluefin tuna experience a wide range of ambient sea temperatures and occupy the largest geographical niche of all tunas. Their capacity to endure thermal challenge is due in part to enhanced expression and activity of key proteins involved in cardiac excitation–contraction coupling, which improve cardiomyocyte function and whole animal performance during temperature change. To define the cellular mechanisms that enable bluefin tuna hearts to function during acute temperature change, we investigated the performance of freshly isolated ventricular myocytes using confocal microscopy and electrophysiology. We demonstrate that acute cooling and warming (between 8 and 28°C) modulates the excitability of the cardiomyocyte by altering the action potential (AP) duration and the amplitude and kinetics of the cellular Ca2+ transient. We then explored the interactions between temperature, adrenergic stimulation and contraction frequency, and show that when these stressors are combined in a physiologically relevant way, they alter AP characteristics to stabilize excitation–contraction coupling across an acute 20°C temperature range. This allows the tuna heart to maintain consistent contraction and relaxation cycles during acute thermal challenges. We hypothesize that this cardiac capacity plays a key role in the bluefin tunas' niche expansion across a broad thermal and geographical range. PMID:25540278

Apatite (U-Th)/He thermochronometry as an innovative geothermal exploration tool: A case study from the southern Wassuk Range, Nevada

NASA Astrophysics Data System (ADS)

Gorynski, Kyle E.; Walker, J. Douglas; Stockli, Daniel F.; Sabin, Andrew

2014-01-01

Extensional-type geothermal systems are complicated by the interrelation between footwall advection during exhumation, and the subsequent redistribution of heat by migrating hydrothermal fluids in the hanging wall. The southern Wassuk Range (WR) hanging wall hosts a moderate-temperature, extensional-type geothermal system and is ideal for studying this duality by analyzing a suite of apatite (AHe) and zircon (ZHe) helium samples from the footwall and hanging wall of the southern WR. Young (~ 3-4 Ma) AHe ages along the WR front are concentrated along the SE corners of segmented footwall blocks, marking the location of focused Mio-Pliocene transtension, fracture dilation, and advection. Hydrothermally reset AHe ages along the footwall range front suggest that the Hawthorne geothermal system (85°-135° C) is long lived and has resided at a prominent structural boundary in the WR footwall marked by localized advection and range-front deformation. In contrast, the presence of both hydrothermally reset and non-reset AHe ages from a ~ 1.4 km deep borehole in the hanging-wall basin probably indicate that the geothermal plumbing system and current manifestation as a thermal anomaly (~ 113 °C) are juvenile and are controlled by the generation of newly formed faults in the hanging wall. AHe ages have been shown here to greatly enhance the focusing of regional-scale geothermal exploration efforts, and for the first time have been used to identify and estimate the temperature of unseen hydrothermal fluids.

Slowing down of alpha particles in ICF DT plasmas

NASA Astrophysics Data System (ADS)

He, Bin; Wang, Zhi-Gang; Wang, Jian-Guo

2018-01-01

With the effects of the projectile recoil and plasma polarization considered, the slowing down of 3.54 MeV alpha particles is studied in inertial confinement fusion DT plasmas within the plasma density range from 1024 to 1026 cm-3 and the temperature range from 100 eV to 200 keV. It includes the rate of the energy change and range of the projectile, and the partition fraction of its energy deposition to the deuteron and triton. The comparison with other models is made and the reason for their difference is explored. It is found that the plasmas will not be heated by the alpha particle in its slowing down the process once the projectile energy becomes close to or less than the temperature of the electron or the deuteron and triton in the plasmas. This leads to less energy deposition to the deuteron and triton than that if the recoil of the projectile is neglected when the temperature is close to or higher than 100 keV. Our model is found to be able to provide relevant, reliable data in the large range of the density and temperature mentioned above, even if the density is around 1026 cm-3 while the deuteron and triton temperature is below 500 eV. Meanwhile, the two important models [Phys. Rev. 126, 1 (1962) and Phys. Rev. E 86, 016406 (2012)] are found not to work in this case. Some unreliable data are found in the last model, which include the range of alpha particles and the electron-ion energy partition fraction when the electron is much hotter than the deuteron and triton in the plasmas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Jingli; Chen, Cun; Wang, Gang

This study explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10 –2 s –1; the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at themore » intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10 –2 s –1.« less

Dynamic Temperature and Pressure Measurements in the Core of a Propulsion Engine

NASA Technical Reports Server (NTRS)

Schuster, Bill; Gordon, Grant; Hultgren, Lennart S.

2015-01-01

Dynamic temperature and pressure measurements were made in the core of a TECH977 propulsion engine as part of a NASA funded investigation into indirect combustion noise. Dynamic temperature measurements were made in the combustor, the inter-turbine duct, and the mixer using ten two-wire thermocouple probes. Internal dynamic pressure measurements were made at the same locations using piezoresistive transducers installed in semi-infinite coils. Measurements were acquired at four steady state operating conditions covering the range of aircraft approach power settings. Fluctuating gas temperature spectra were computed from the thermocouple probe voltage measurements using a compensation procedure that was developed under previous NASA test programs. A database of simultaneously acquired dynamic temperature and dynamic pressure measurements was produced. Spectral and cross-spectral analyses were conducted to explore the characteristics of the temperature and pressure fluctuations inside the engine, with a particular focus on attempting to identify the presence of indirect combustion noise.

Evaluation of Capacitors at Cryogenic Temperatures for Space Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad; Gerber, Scott S.

1998-01-01

Advanced electronic systems designed for use in planetary exploration missions must operate efficiently and reliably under the extreme cold temperatures of deep space environment. In addition, spacecraft power electronics capable of cold temperature operation will greatly simplify the thermal management system by eliminating the need for heating units and associated equipment and thereby reduce the size and weight of the overall power system. In this study, film, mica, solid tantalum and electric double layer capacitors were evaluated as a function of temperature from room to liquid nitrogen in terms of their dielectric properties. These properties included capacitance stability and dielectric loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed on the capacitors. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors investigated for low temperature applications.

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Hernández-Gómez, P.; Muñoz, J. M.; Valente, M. A.; Torres, C.; de Francisco, C.

2013-01-01

Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer's formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

Crump Geyser Exploration and Drilling Project. High Precision Geophysics and Detailed Structural Exploration and Slim Well Drilling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fairbank, Brian D.; Smith, Nicole

The Crump Geyser Exploration and Drilling Project – High Precision Geophysics and Detailed Structural Exploration and Slim Well Drilling ran from January 29, 2010 to September 30, 2013. During Phase 1 of the project, collection of all geophysical surveys was completed as outlined in the Statement of Project Objectives. In addition, a 5000-foot full sized exploration well was drilled by Ormat, and preexisting drilling data was discovered for multiple temperature gradient wells within the project area. Three dimensional modeling and interpretation of results from the geophysical surveys and drilling data gave confidence to move to the project into Phase 2more » drilling. Geological and geophysical survey interpretations combined with existing downhole temperature data provided an ideal target for the first slim-hole drilled as the first task in Phase 2. Slim-hole 35-34 was drilled in September 2011 and tested temperature, lithology, and permeability along the primary range-bounding fault zone near its intersection with buried northwest-trending faults that have been identified using geophysical methods. Following analysis of the results of the first slim-hole 35-34, the second slim hole was not drilled and subsequent project tasks, including flowing differential self-potential (FDSP) surveys that were designed to detail the affect of production and injection on water flow in the shallow aquifer, were not completed. NGP sold the Crump project to Ormat in August 2014, afterwards, there was insufficient time and interest from Ormat available to complete the project objectives. NGP was unable to continue managing the award for a project they did not own due to liability issues and Novation of the award was not a viable option due to federal award timelines. NGP submitted a request to mutually terminate the award on February 18, 2015. The results of all of the technical surveys and drilling are included in this report. Fault interpretations from surface geology, aeromag, seismic, and gravity data sets are in good agreement, illustrating two or more major range-bounding faults and buried northwest trending faults. The intersections of these fault systems provide the primary targets for drilling.« less

Cryogenic Refractive Indices of S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14 Glasses

NASA Technical Reports Server (NTRS)

Miller, Kevin H.; Quijada, Manuel A.; Leviton, Douglas B.

2015-01-01

The Transiting Exoplanet Survey Satellite (TESS) is an explorer-class planet finder, whose principal goal is to detect small planets with bright host starts in the solar neighborhood. The TESS payload consists of four identical cameras and a Data Handling Unit (DHU) fitted with CCD detectors and associated electronics. Each camera consist of a lens assembly with seven optical elements that include various types of Ohara glass substrates. The successful implementation of a panchromatic and a thermal lens assembly design for these cameras requires a fairly accurate (up to 0.000001 (1e-6)) knowledge of the temperature- and wavelength-dependent of the refractive index in the wavelength and temperature range of operation. Hence, this paper is devoted to report on measurements of the refractive index over the wavelength range of 0.42-1.15 micrometers and temperature range of 110-300 K for the following Ohara glasses: S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14. The measurements were performed utilizing the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at NASA's Goddard Space Flight Center. A dense coverage of the absolute refractive index for all these substrates in the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dndT) and dispersion relation (dnd) as a function of wavelength and temperature. A comparison of the measured indices with literature values, specifically the temperature-dependent refractive indices of S-PHM52 and S-TIH14 reported by Yamamuro et al. [Yamamuro et al., Opt. Eng. 45(8), 083401 (2006)], will be presented.

Organismal climatology: analyzing environmental variability at scales relevant to physiological stress.

PubMed

Helmuth, Brian; Broitman, Bernardo R; Yamane, Lauren; Gilman, Sarah E; Mach, Katharine; Mislan, K A S; Denny, Mark W

2010-03-15

Predicting when, where and with what magnitude climate change is likely to affect the fitness, abundance and distribution of organisms and the functioning of ecosystems has emerged as a high priority for scientists and resource managers. However, even in cases where we have detailed knowledge of current species' range boundaries, we often do not understand what, if any, aspects of weather and climate act to set these limits. This shortcoming significantly curtails our capacity to predict potential future range shifts in response to climate change, especially since the factors that set range boundaries under those novel conditions may be different from those that set limits today. We quantitatively examine a nine-year time series of temperature records relevant to the body temperatures of intertidal mussels as measured using biomimetic sensors. Specifically, we explore how a 'climatology' of body temperatures, as opposed to long-term records of habitat-level parameters such as air and water temperatures, can be used to extrapolate meaningful spatial and temporal patterns of physiological stress. Using different metrics that correspond to various aspects of physiological stress (seasonal means, cumulative temperature and the return time of extremes) we show that these potential environmental stressors do not always occur in synchrony with one another. Our analysis also shows that patterns of animal temperature are not well correlated with simple, commonly used metrics such as air temperature. Detailed physiological studies can provide guidance to predicting the effects of global climate change on natural ecosystems but only if we concomitantly record, archive and model environmental signals at appropriate scales.

The Development of Silicon Carbide Based Hydrogen and Hydrocarbon Sensors

NASA Technical Reports Server (NTRS)

Liu, Chung-Chiun

1994-01-01

Silicon carbide is a high temperature electronic material. Its potential for development of chemical sensors in a high temperature environment has not been explored. The objective of this study is to use silicon carbide as the substrate material for the construction of chemical sensors for high temperature applications. Sensors for the detection of hydrogen and hydrocarbon are developed in this program under the auspices of Lewis Research Center, NASA. Metal-semiconductor or metal-insulator-semiconductor structures are used in this development. Specifically, using palladium-silicon carbide Schottky diodes as gas sensors in the temperature range of 100 to 400 C are designed, fabricated and assessed. The effect of heat treatment on the Pd-SiC Schottky diode is examined. Operation of the sensors at 400 C demonstrate sensitivity of the sensor to hydrogen and hydrocarbons. Substantial progress has been made in this study and we believe that the Pd-SiC Schottky diode has potential as a hydrogen and hydrocarbon sensor over a wide range of temperatures. However, the long term stability and operational life of the sensor need to be assessed. This aspect is an important part of our future continuing investigation.

Antibody-producing cells correlated to body weight in juvenile chinook salmon (Oncorhynchus tshawytscha) acclimated to optimal and elevated temperatures

USGS Publications Warehouse

Harrahy, L.N.M.; Schreck, C.B.; Maule, A.G.

2001-01-01

The immune response of juvenile chinook salmon (Oncorhynchus tshawytscha) ranging in weight from approximately 10 to 55 g was compared when the fish were acclimated to either 13 or 21?? C. A haemolytic plaque assay was conducted to determine differences in the number of antibody-producing cells (APC) among fish of a similar age but different body weights. Regression analyses revealed significant increases in the number of APC with increasing body weight when fish were acclimated to either water temperature. These results emphasise the importance of standardising fish weight in immunological studies of salmonids before exploring the possible effects of acclimation temperatures. ?? 2001 Academic Press.

Antibody-producting cells correlated with body weight in juvenile Chinook salmon Oncorhynchus tshawytscha acclimated to optimal and elevated temperatures

USGS Publications Warehouse

Harrahy, L.N.M.; Schreck, Carl B.; Maule, Alec G.

2001-01-01

The immune response of juvenile chinook salmon (Oncorhynchus tshawytscha) ranging in weight from approximately 10 to 55 g was compared when the fish were acclimated to either 13 or 21° C. A haemolytic plaque assay was conducted to determine differences in the number of antibody-producing cells (APC) among fish of a similar age but different body weights. Regression analyses revealed significant increases in the number of APC with increasing body weight when fish were acclimated to either water temperature. These results emphasise the importance of standardising fish weight in immunological studies of salmonids before exploring the possible effects of acclimation temperatures.

High Resolution Thermometry for EXACT

NASA Technical Reports Server (NTRS)

Panek, J. S.; Nash, A. E.; Larson, M.; Mulders, N.

2000-01-01

High Resolution Thermometers (HRTs) based on SQUID detection of the magnetization of a paramagnetic salt or a metal alloy has been commonly used for sub-nano Kelvin temperature resolution in low temperature physics experiments. The main applications to date have been for temperature ranges near the lambda point of He-4 (2.177 K). These thermometers made use of materials such as Cu(NH4)2Br4 *2H2O, GdCl3, or PdFe. None of these materials are suitable for EXACT, which will explore the region of the He-3/He-4 tricritical point at 0.87 K. The experiment requirements and properties of several candidate paramagnetic materials will be presented, as well as preliminary test results.

A luminescent Lanthanide-free MOF nanohybrid for highly sensitive ratiometric temperature sensing in physiological range.

PubMed

Zhou, You; Zhang, Denan; Zeng, Jin; Gan, Ning; Cuan, Jing

2018-05-01

Luminescent MOF materials with tunable emissions and energy/charge transfer processes have been extensively explored as ratiometric temperature sensors. However, most of the ratiometric MOF thermometers reported thus far are based on the MOFs containing photoactive lanthanides, which are potentially facing cost issue and serious supply shortage. Here, we present a ratiometric luminescent thermometer based on a dual-emitting lanthanide-free MOF hybrid, which is developed by encapsulation of a fluorescent dye into a robust nanocrystalline zirconium-based MOF through a one-pot synthesis approach. The structure and morphology of the hybrid product was characterized by Powder X-ray diffraction (PXRD), N 2 adsorption-desorption measurement and Scanning electron microscopy (SEM). The pore confinement effect well isolates the guest dye molecules and therefore suppresses the nonradiative energy transfer process between dye molecules. The incorporated dye emission is mainly sensitized by the organic linkers within MOF through fluorescence resonance energy transfer. The ratiometric luminescence of the MOF hybrid shows a significant response to temperature due to the thermal-related back energy transfer process from dye molecules and organic linkers, thus can be exploited for self-calibrated temperature sensing. The maximum thermometric sensitivity is 1.19% °C -1 in the physiological temperature range, which is among the highest for the ratiomtric MOF thermometers that operating in 25-45°C. The temperature resolution is better than 0.1°C over the entire operative range (20-60°C). By integrating the advantages of excellent stability, nanoscale nature, and high sensitivity and precision in the physiological temperature range, this dye@MOF hybrid might have potential application in biomedical diagnosis. What' more, this work has expanded the possibility of non-lanthanide luminescent MOF materials for the development of ratiometric temperature sensors. Copyright © 2018 Elsevier B.V. All rights reserved.

Temperature dependence of the plastic scintillator detector for DAMPE

NASA Astrophysics Data System (ADS)

Wang, Zhao-Min; Yu, Yu-Hong; Sun, Zhi-Yu; Yue, Ke; Yan, Duo; Zhang, Yong-Jie; Zhou, Yong; Fang, Fang; Huang, Wen-Xue; Chen, Jun-Ling

2017-01-01

The Plastic Scintillator Detector (PSD) is one of the main sub-detectors in the DArk Matter Particle Explorer (DAMPE) project. It will be operated over a large temperature range from -10 to 30 °C, so the temperature effect of the whole detection system should be studied in detail. The temperature dependence of the PSD system is mainly contributed by the three parts: the plastic scintillator bar, the photomultiplier tube (PMT), and the Front End Electronics (FEE). These three parts have been studied in detail and the contribution of each part has been obtained and discussed. The temperature coefficient of the PMT is -0.320(±0.033)%/°C, and the coefficient of the plastic scintillator bar is -0.036(±0.038)%/°C. This result means that after subtracting the FEE pedestal, the variation of the signal amplitude of the PMT-scintillator system due to temperature mainly comes from the PMT, and the plastic scintillator bar is not sensitive to temperature over the operating range. Since the temperature effect cannot be ignored, the temperature dependence of the whole PSD has been also studied and a correction has been made to minimize this effect. The correction result shows that the effect of temperature on the signal amplitude of the PSD system can be suppressed. Supported by Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences (XDA04040202-3) and Youth Innovation Promotion Association, CAS

Improved microstructure and thermoelectric properties of iodine doped indium selenide as a function of sintering temperature

NASA Astrophysics Data System (ADS)

Dhama, Pallavi; Kumar, Aparabal; Banerji, P.

2018-04-01

In this paper, we explored the effect of sintering temperature on the microstructure, thermal and electrical properties of iodine doped indium selenide in the temperature range 300 - 700 K. Samples were prepared by a collaborative process of vacuum melting, ball milling and spark plasma sintering at 570 K, 630 K and 690 K. Single phase samples were obtained at higher sintering temperature as InSe is stable only at lower temperature. With increasing sintering temperature, densities of the samples were found to improve with larger grain size formation. Negative values of Seebeck coefficient were observed which indicates n-type carrier transport. Seebeck coefficient increases with sintering temperature and found to be the highest for the sample sintered at 690 K. Thermal conductivity found to be lower in the samples sintered at lower temperatures. The maximum thermoelectric figure of merit found to be ˜ 1 at 700 K due to the enhanced power factor as a result of improved microstructure.

Chemical transitions of Areca semen during the thermal processing revealed by temperature-resolved ATR-FTIR spectroscopy and two-dimensional correlation analysis

NASA Astrophysics Data System (ADS)

Wang, Zhibiao; Wang, Xu; Pei, Wenxuan; Li, Sen; Sun, Suqin; Zhou, Qun; Chen, Jianbo

2018-03-01

Areca semen is a common herb used in traditional Chinese medicine, but alkaloids in this herb are categorized as Group I carcinogens by IARC. It has been proven that the stir-baking process can reduce alkaloids in Areca semen while keep the activity for promoting digestion. However, the changes of compositions other than alkaloids during the thermal processing are unclear. Understanding the thermal chemical transitions of Areca semen is necessary to explore the processing mechanisms and optimize the procedures. In this research, FTIR spectroscopy with a temperature-controlled ATR accessory is employed to study the heating process of Areca semen. Principal component analysis and two-dimensional correlation spectroscopy are used to interpret the spectra to reveal the chemical transitions of Areca semen in different temperature ranges. The loss of a few volatile compounds in the testa and sperm happens below 105 °C, while some esters in the sperm decreases above 105 °C. As the heating temperature is close to 210 °C, Areca semen begins to be scorched and the decomposition of many compounds can be observed. This research shows the potential of the temperature-resolved ATR-FTIR spectroscopy in exploring the chemical transitions of the thermal processing of herbal materials.

Exploring the potential of clumped isotope thermometry on coccolith-rich sediments as a sea surface temperature proxy

NASA Astrophysics Data System (ADS)

Drury, Anna Joy; John, Cédric M.

2016-10-01

Understanding past changes in sea surface temperatures (SSTs) is crucial; however, existing proxies for reconstructing past SSTs are hindered by unknown ancient seawater composition (foraminiferal Mg/Ca and δ18O) or reflect subsurface temperatures (TEX86) or have a limited applicable temperature range (U37k'). We examine clumped isotope (Δ47) thermometry to fossil coccolith-rich material as an SST proxy, as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant. The Δ47-derived temperatures from <63, <20, <10, and 2-5 μm size fractions of two equatorial Pacific late Miocene-early Pliocene sediment samples (c1; c2) range between ˜18 and 29°C, with c1 temperatures consistently above c2. Removing the >63 μm fraction removes most nonmixed layer components; however, the Δ47-derived temperatures display an unexpected slight decreasing trend with decreasing size fraction. This unexpected trend could partly arise because larger coccoliths (5-12 μm) are removed during the size fraction separation process. The c1 and <63 μm c2 Δ47-derived temperatures are comparable to concurrent U37k' SSTs. The <20, <10, and 2-5 μm c2 Δ47-derived temperatures are consistently cooler than expected. The Δ47-U37k' temperature offset is probably caused by abiotic/diagenetic calcite present in the c2 2-5 μm fraction (˜53% by area), which potentially precipitated at bottom water temperatures of ˜6°C. Our results indicate that clumped isotopes on coccolith-rich sediment fractions have potential as an SST proxy, particularly in tropical regions, providing that careful investigation of the appropriate size fraction for the region and time scale is undertaken.

Performance Evaluation of an Automotive-Grade, High Speed Gate Driver for SiC FETs, Type UCC27531, Over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Boomer, Kristen; Hammoud, Ahmad

2015-01-01

Silicon carbide (SiC) devices are becoming widely used in electronic power circuits as replacement for conventional silicon parts due to their attractive properties that include low on-state resistance, high temperature tolerance, and high frequency operation. These attributes have a significant impact by reducing system weight, saving board space, and conserving power. In this work, the performance of an automotive-grade high speed gate driver with potential use in controlling SiC FETs (field-Effect Transistors) in converters or motor control applications was evaluated under extreme temperatures and thermal cycling. The investigations were carried out to assess performance and to determine suitability of this device for use in space exploration missions under extreme temperature conditions.

Optical temperature sensing properties of Sm3+ doped SrWO4 phosphor

NASA Astrophysics Data System (ADS)

Song, Huiling; Han, Qun; Wang, Chao; Tang, Xiaoyun; Yan, Wenchuan; Chen, Yaofei; Zhao, Xueru; Jiang, Junfeng; Liu, Tiegen

2018-04-01

Sm3+ doped SrWO4 was synthesized by the high temperature solid-state reaction method to explore its possible application in optical thermometry. Under a 404 nm excitation, the fluorescence intensity ratios (FIRs) between the down conversion emissions of the Sm3+:4G5/2 → 6H5/2 (564 nm) to the Sm3+:4G5/2 → 6H7/2 (600 nm) and Sm3+:4G5/2 → 6H9/2 (647 nm), respectively, were measured as a function of temperature in the range of 300-573 K. A maximum temperature sensitivity of 0.016 K-1 at 300 K is achieved. The results indicate that the SrWO4:Sm3+ is a promising candidate for optical thermometry.

Synthesis and thermal conductivity of type II silicon clathrates

NASA Astrophysics Data System (ADS)

Beekman, M.; Nolas, G. S.

2006-08-01

We have synthesized and characterized polycrystalline Na 1Si 136 and Na 8Si 136, compounds possessing the type II clathrate hydrate crystal structure. Resistivity measurements from 10 to 300 K indicate very large resistivities in this temperature range, with activated temperature dependences indicative of relatively large band gap semiconductors. The thermal conductivity is very low; two orders-of-magnitude lower than that of diamond-structure silicon at room temperature. The thermal conductivity of Na 8Si 136 displays a temperature dependence that is atypical of crystalline solids and more indicative of amorphous materials. This work is part of a continuing effort to explore the many different compositions and structure types of clathrates, a class of materials that continues to be of interest for scientific and technological applications.

Superficial Velocity Effects on HZ-PAN and AgZ-PAN for Kr/Xe Capture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welty, Amy Keil; Garn, Troy Gerry; Greenhalgh, Mitchell Randy

2016-04-01

Nearly all previous testing of HZ-PAN and AgZ-PAN was conducted at the same flow rate in order to maintain consistency among tests. This testing was sufficient for sorbent capacity determinations, but did not ensure that sorbents were capable of functioning under a range of flow regimes. Tests were conducted on both HZ-PAN and AgZ-PAN at superficial velocities between 20 and 700 cm/min. For HZ-PAN, Kr capacity increased from 60 mmol/kg to 110 mmol/kg as superficial velocity increased from 21 to 679 cm/min. Results for AgZ-PAN were similar, with capacity ranging from 72 to 124 mmol/kg over the same range ofmore » superficial. These results are promising for scaling up to process flows, demonstrating flexibility to operate in a broad range of superficial velocities while maintaining sorbent capacity. While preparing for superficial velocity testing it was also discovered that AgZ-PAN Xe capacity, previously observed to diminish over time, could be recovered with increased desorption temperature. Further, a substantial Xe capacity increase was observed. Previous room temperature capacities in the range of 22-25 mmol Xe/kg AgZ-PAN were increased to over 60 mmol Xe/kg AgZ-PAN. While this finding has not yet been fully explored to optimize activation and desorption temperatures, it is encouraging.« less

SOI N-Channel Field Effect Transistors, CHT-NMOS80, for Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Almad

2009-01-01

Extreme temperatures, both hot and cold, are anticipated in many of NASA space exploration missions as well as in terrestrial applications. One can seldom find electronics that are capable of operation under both regimes. Even for operation under one (hot or cold) temperature extreme, some thermal controls need to be introduced to provide appropriate ambient temperatures so that spacecraft on-board or field on-site electronic systems work properly. The inclusion of these controls, which comprise of heating elements and radiators along with their associated structures, adds to the complexity in the design of the system, increases cost and weight, and affects overall reliability. Thus, it would be highly desirable and very beneficial to eliminate these thermal measures in order to simplify system's design, improve efficiency, reduce development and launch costs, and improve reliability. These requirements can only be met through the development of electronic parts that are designed for proper and efficient operation under extreme temperature conditions. Silicon-on-insulator (SOI) based devices are finding more use in harsh environments due to the benefits that their inherent design offers in terms of reduced leakage currents, less power consumption, faster switching speeds, good radiation tolerance, and extreme temperature operability. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. The objective of this work was to evaluate the performance of a new commercial-off-the-shelf (COTS) SOI parts over an extended temperature range and to determine the effects of thermal cycling on their performance. The results will establish a baseline on the suitability of such devices for use in space exploration missions under extreme temperatures, and will aid mission planners and circuit designers in the proper selection of electronic parts and circuits. The electronic part investigated in this work comprised of a CHT-NMOS80 high temperature N-channel MOSFET (metal-oxide semiconductor field-effect transistor) device that was manufactured by CISSOID. This high voltage, medium-power transistor is fabricated using SOI processes and is designed for extreme wide temperature applications such as geothermal well logging, aerospace and avionics, and automotive industry. It has a high DC current capability and is specified for operation in the temperature range of -55 C to +225 C

Properties of AGN coronae in the NuSTAR era - II. Hybrid plasma

NASA Astrophysics Data System (ADS)

Fabian, A. C.; Lohfink, A.; Belmont, R.; Malzac, J.; Coppi, P.

2017-05-01

The corona, a hot cloud of electrons close to the centre of the accretion disc, produces the hard X-ray power-law continuum commonly seen in luminous active galactic nuclei. The continuum has a high-energy turnover, typically in the range of one to several 100 keV and is suggestive of Comptonization by thermal electrons. We are studying hard X-ray spectra of AGN obtained with NuSTAR after correction for X-ray reflection and under the assumption that coronae are compact, being only a few gravitational radii in size as indicated by reflection and reverberation modelling. Compact coronae raise the possibility that the temperature is limited and indeed controlled by electron-positron pair production, as explored earlier (Paper I). Here, we examine hybrid plasmas in which a mixture of thermal and non-thermal particles is present. Pair production from the non-thermal component reduces the temperature leading to a wider temperature range more consistent with observations.

Observation of antiferromagnetic order collapse in the pressurized insulator LaMnPO

NASA Astrophysics Data System (ADS)

Guo, Jing; Simonson, Jack; Sun, Liling; Wu, Qi; Guo, Peiwen; Zhang, Chao; Gu, Dachun; Kotliar, Gabriel; Aronson, Meigan; Zhao, Zhongxian

2014-03-01

The emergence of superconductivity in the iron pnictide or cuprate high temperature superconductors usually accompanies the suppression of a long-ranged antiferromagnetic (AFM) order state in a corresponding parent compound by doping or pressurizing. A great deal of effort by doping has been made to find superconductivity in Mn-based compounds, which are thought to bridge the gap between the two families of high temperature superconductors, but the AFM order was not successfully suppressed. Here we report the first observations of the pressure-induced elimination of long-ranged AFM order at ~ 34 GPa and a crossover from an AFM insulating to an AFM metallic state at ~ 20 GPa in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor by in-situ high pressure resistance and ac susceptibility measurements. These findings are of importance to explore potential superconductivity in Mn-based compounds and to shed new light on the underlying mechanism of high temperature superconductivity.

Observation of antiferromagnetic order collapse in the pressurized insulator LaMnPO

NASA Astrophysics Data System (ADS)

Guo, Jing; Simonson, J. W.; Sun, Liling; Wu, Qi; Gao, Peiwen; Zhang, Chao; Gu, Dachun; Kotliar, Gabriel; Aronson, Meigan; Zhao, Zhongxian

2013-08-01

The emergence of superconductivity in the iron pnictide or cuprate high temperature superconductors usually accompanies the suppression of a long-ranged antiferromagnetic (AFM) order state in a corresponding parent compound by doping or pressurizing. A great deal of effort by doping has been made to find superconductivity in Mn-based compounds, which are thought to bridge the gap between the two families of high temperature superconductors, but the AFM order was not successfully suppressed. Here we report the first observations of the pressure-induced elimination of long-ranged AFM order at ~ 34 GPa and a crossover from an AFM insulating to an AFM metallic state at ~ 20 GPa in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor by in-situ high pressure resistance and ac susceptibility measurements. These findings are of importance to explore potential superconductivity in Mn-based compounds and to shed new light on the underlying mechanism of high temperature superconductivity.

A System Level Mass and Energy Calculation for a Temperature Swing Adsorption Pump used for In-Situ Resource Utilization (ISRU) on Mars

NASA Technical Reports Server (NTRS)

Hasseeb, Hashmatullah; Iannetti, Anthony

2017-01-01

A major component of a Martian In-Situ Resource Utilization (ISRU) system is the CO2 acquisition subsystem. This subsystem must be able to extract and separate CO2 at ambient Martian pressures and then output the gas at high pressures for the chemical reactors to generate fuel and oxygen. The Temperature Swing Adsorption (TSA) Pump is a competitive design that can perform this task using heating and cooling cycles in an enclosed volume. The design of this system is explored and analyzed for an output pressure range of 50 kPa to 500 kPa and an adsorption temperature range of -50 C to 40 C while meeting notional requirements for two mission scenarios. Mass and energy consumption results are presented for 2-stage, 3-stage, and 4-stage systems using the following adsorbents: Grace 544 13X, BASF 13X, Grace 522 5A and VSA 10 LiX.

Observation of antiferromagnetic order collapse in the pressurized insulator LaMnPO.

PubMed

Guo, Jing; Simonson, J W; Sun, Liling; Wu, Qi; Gao, Peiwen; Zhang, Chao; Gu, Dachun; Kotliar, Gabriel; Aronson, Meigan; Zhao, Zhongxian

2013-01-01

The emergence of superconductivity in the iron pnictide or cuprate high temperature superconductors usually accompanies the suppression of a long-ranged antiferromagnetic (AFM) order state in a corresponding parent compound by doping or pressurizing. A great deal of effort by doping has been made to find superconductivity in Mn-based compounds, which are thought to bridge the gap between the two families of high temperature superconductors, but the AFM order was not successfully suppressed. Here we report the first observations of the pressure-induced elimination of long-ranged AFM order at ~ 34 GPa and a crossover from an AFM insulating to an AFM metallic state at ~ 20 GPa in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor by in-situ high pressure resistance and ac susceptibility measurements. These findings are of importance to explore potential superconductivity in Mn-based compounds and to shed new light on the underlying mechanism of high temperature superconductivity.

Silicates Do Nucleate in Oxygen-rich Circumstellar Outflows: New Vapor Pressure Data for SiO

NASA Astrophysics Data System (ADS)

Nuth, Joseph A., III; Ferguson, Frank T.

2006-10-01

We have measured the vapor pressure of solid SiO as a function of temperature over the range from 1325 up to 1785 K in vacuo using a modified Thermo-Cahn thermogravimetric system. Although an extrapolation of the current vapor pressure data to 2200 K is close to that predicted from the work of Schick under reducing conditions, the vapor pressures measured at successively lower temperatures diverge significantly from such predictions and are several orders of magnitude lower than predicted at 1200 K. This new vapor pressure data has been inserted into a simple model for the gas expanding from a late-stage star. Using the new vapor pressure curve makes a significant difference in the temperature and stellar radius at which SiO gas becomes supersaturated, although SiO still becomes supersaturated at temperatures that are too low to be consistent with observations. We have therefore also explored the effects of vibrational disequilibrium (as explored by Nuth & Donn) of SiO in the expanding shell on the conditions under which nucleation occurs. These calculations are much more interesting in that supersaturation now occurs at much higher kinetic temperatures. We note, however, that both vibrational disequilibrium and the new vapor pressure curve are required to induce SiO supersaturation in stellar outflows at temperatures above 1000 K.

Cybersonics: Tapping into Technology

NASA Technical Reports Server (NTRS)

2001-01-01

With the assistance of Small Business Innovation Research (SBIR) funding from NASA's Jet Propulsion Laboratory, Cybersonics, Inc., developed an ultrasonic drill with applications ranging from the medical industry to space exploration. The drill, which has the ability to take a core sample of the hardest granite or perform the most delicate diagnostic medical procedure, is a lightweight, ultrasonic device made to fit in the palm of the hand. Piezoelectric actuators, which have only two moving parts and no gears or motors, drive the components of the device, enabling it to operate in a wide range of temperatures. The most remarkable aspect of the drill is its ability to penetrate even the hardest rock with minimal force application. The ultrasonic device requires 20 to 30 times less force than standard rotating drills, allowing it to be safely guided by hand during operation. Also, the drill is operable at a level as low as three watts of power, where conventional drills require more than three times this level. Potential future applications for the ultrasonic drill include rock and soil sampling, medical procedures that involve core sampling or probing, landmine detection, building and construction, and space exploration. Cybersonics, Inc. developed an ultrasonic drill with applications ranging from the medical industry to space exploration.

Polar Lunar Regions: Exploiting Natural and Augmented Thermal Environments

NASA Astrophysics Data System (ADS)

Ryan, R. E.; McKellip, R. C.; Brannon, D. P.; Underwood, L. W.; Russell, K. J.

2007-12-01

In polar regions of the Moon, there are areas within craters that are permanently shadowed from solar illumination, which can reach temperatures of 100K or less. These regions could serve as cold traps, capturing ice and other volatile compounds. These potential ice stores have many applications for lunar exploration. Within double-shaded craters, even colder regions exist, with temperatures never exceeding 50K in many cases. Temperatures observed in theses regions suggest that they could enable equivalent liquid nitrogen cryogenic functions. These permanently shaded polar craters also offer unprecedented high vacuum cryogenic environments, which in their current state could support cryogenic applications. The unique conditions at the lunar poles, besides ice stores, harbor an environment that provides an opportunity to reduce the power, weight and total mass that needs to be carried from the Earth to the moon for lunar exploration and research. Reducing the heat flux of geothermal, black body radiation can have significant impacts on the achievable temperature. With a few man-made augmentations, permanently shaded craters located near the lunar poles achieve temperatures even lower than those that naturally exist there. Our analysis reveals that lightweight thermal shielding, within shaded craters, could create an environment several Kelvin above absolute zero. The temperature ranges of naturally shaded craters and thermally augmented ones could enable the long-term storage of most gases, low temperature superconductors for large magnetic fields, devices and advanced high speed computing instruments. Augmenting thermal conditions in these craters could then be used as a basis for the development of an advanced thermal management architecture that would support a wide variety of cryogenically based applications. Lunar exploration and habitation capabilities would significantly benefit if permanently shaded craters, augmented with thermal shielding, were to be used to facilitate the operation of near absolute zero instruments, including wide variety of cryogenically based propulsion, energy, communication, sensing and computing devices. Potentially, the required burden of carrying massive life-supporting components from the Earth to the moon for lunar exploration and research could be reduced.

Cr-rich rutile: A powerful tool for diamond exploration

NASA Astrophysics Data System (ADS)

Malkovets, V. G.; Rezvukhin, D. I.; Belousova, E. A.; Griffin, W. L.; Sharygin, I. S.; Tretiakova, I. G.; Gibsher, A. A.; O'Reilly, S. Y.; Kuzmin, D. V.; Litasov, K. D.; Logvinova, A. M.; Pokhilenko, N. P.; Sobolev, N. V.

2016-11-01

Mineralogical studies and U-Pb dating have been carried out on rutile included in peridotitic and eclogitic garnets from the Internatsionalnaya pipe, Mirny field, Siberian craton. We also describe a unique peridotitic paragenesis (rutile + forsterite + enstatite + Cr-diopside + Cr-pyrope) preserved in diamond from the Mir pipe, Mirny field. Compositions of rutile from the heavy mineral concentrates of the Internatsionalnaya pipe and rutile inclusions in crustal almandine-rich garnets from the Mayskaya pipe (Nakyn field), as well as from a range of different lithologies, are presented for comparison. Rutile from cratonic mantle peridotites shows characteristic enrichment in Cr, in contrast to lower-Cr rutile from crustal rocks and off-craton mantle. Rutile with Cr2O3 > 1.7 wt% is commonly derived from cratonic mantle, while rutiles with lower Cr2O3 may be both of cratonic and off-cratonic origin. New analytical developments and availability of standards have made rutile accessible to in situ U-Pb dating by laser ablation ICP-MS. A U-Pb age of 369 ± 10 Ma for 9 rutile grains in 6 garnets from the Internatsionalnaya pipe is consistent with the accepted eruption age of the pipe (360 Ma). The equilibrium temperatures of pyropes with rutile inclusions calculated using Ni-in-Gar thermometer range between 725 and 1030 °C, corresponding to a depth range of ca 100-165 km. At the time of entrainment in the kimberlite, garnets with Cr-rich rutile inclusions resided at temperatures well above the closure temperature for Pb in rutile, and thus U-Pb ages on mantle-derived rutile most likely record the emplacement age of the kimberlites. The synthesis of distinctive rutile compositions and U-Pb dating opens new perspectives for using rutile in diamond exploration in cratonic areas.

Cryogenic Behavior of the High Temperature Crystal Oscillator PX-570

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad; Scherer, Steven

2011-01-01

Microprocessors, data-acquisition systems, and electronic controllers usually require timing signals for proper and accurate operation. These signals are, in most cases, provided by circuits that utilize crystal oscillators due to availability, cost, ease of operation, and accuracy. Stability of these oscillators, i.e. crystal characteristics, is usually governed, amongst other things, by the ambient temperature. Operation of these devices under extreme temperatures requires, therefore, the implementation of some temperature-compensation mechanism either through the manufacturing process of the oscillator part or in the design of the circuit to maintain stability as well as accuracy. NASA future missions into deep space and planetary exploration necessitate operation of electronic instruments and systems in environments where extreme temperatures along with wide-range thermal swings are countered. Most of the commercial devices are very limited in terms of their specified operational temperature while very few custom-made and military-grade parts have the ability to operate in a slightly wider range of temperature. Thus, it is becomes mandatory to design and develop circuits that are capable of operation efficiently and reliably under the space harsh conditions. This report presents the results obtained on the evaluation of a new (COTS) commercial-off-the-shelf crystal oscillator under extreme temperatures. The device selected for evaluation comprised of a 10 MHz, PX-570-series crystal oscillator. This type of device was recently introduced by Vectron International and is designed as high temperature oscillator [1]. These parts are fabricated using proprietary manufacturing processes designed specifically for high temperature and harsh environment applications [1]. The oscillators have a wide continuous operating temperature range; making them ideal for use in military and aerospace industry, industrial process control, geophysical fields, avionics, and engine control. They exhibit low jitter and phase noise, consume little power, and are suited for high shock and vibration applications. The unique package design of these crystal oscillators offers a small ceramic package footprint, as well as providing both through-hole mounting and surface mount options.

Titanium carbide nanocube core induced interfacial growth of crystalline polypyrrole/polyvinyl alcohol lamellar shell for wide-temperature range supercapacitors

NASA Astrophysics Data System (ADS)

Weng, Yu-Ting; Pan, Hsiao-An; Wu, Nae-Lih; Chen, Geroge Zheng

2015-01-01

This is the first investigation on electrically conducting polymers-based supercapacitor electrodes over a wide temperature range, from -18 °C to 60 °C. A high-performance supercapacitor electrode material consisting of TiC nanocube core and conformal crystalline polypyrrole (PPy)/poly-vinyl-alcohol (PVA) lamellar shell has been synthesized by heterogeneous nucleation-induced interfacial crystallization. PPy is induced to crystallize on the negatively charged TiC nanocube surfaces via strong interfacial interactions. In this organic-inorganic hybrid nanocomposite, the long chain PVA enables enhanced cycle life due to improved mechanical properties, and the TiC nanocube not only contributes to electron conduction, but also dictates the PPy morphology/crystallinity for maximizing the charging-discharging performance. The crystalline PPy/PAV layer on the TiC nanocube offers unprecedented high capacity (>350 F g-1-PPy at 300 mV s-1 with ΔV = 1.6 V) and cycling stability in a temperature range from -18 °C to 60 °C. The presented hybrid-filler and interfacial crystallization strategies can be applied to the exploration of new-generation high-power conducting polymer-based supercapacitor materials.

The impact of temperature on the bionomics of Aedes (Stegomyia) aegypti, with special reference to the cool geographic range margins.

PubMed

Eisen, Lars; Monaghan, Andrew J; Lozano-Fuentes, Saul; Steinhoff, Daniel F; Hayden, Mary H; Bieringer, Paul E

2014-05-01

The mosquito Aedes (Stegomyia) aegypti (L.), which occurs widely in the subtropics and tropics, is the primary urban vector of dengue and yellow fever viruses, and an important vector of chikungunya virus. There is substantial interest in how climate change may impact the bionomics and pathogen transmission potential of this mosquito. This Forum article focuses specifically on the effects of temperature on the bionomics of Ae. aegypti, with special emphasis on the cool geographic range margins where future rising temperatures could facilitate population growth. Key aims are to: 1) broadly define intra-annual (seasonal) patterns of occurrence and abundance of Ae. aegypti, and their relation to climate conditions; 2) synthesize the existing quantitative knowledge of how temperature impacts the bionomics of different life stages of Ae. aegypti; 3) better define the temperature ranges for which existing population dynamics models for Ae. aegypti are likely to produce robust predictions; 4) explore potential impacts of climate warming on human risk for exposure to Ae. aegypti at its cool range margins; and 5) identify knowledge or data gaps that hinder our ability to predict risk of human exposure to Ae. aegypti at the cool margins of its geographic range now and in the future. We first outline basic scenarios for intra-annual occurrence and abundance patterns for Ae. aegypti, and then show that these scenarios segregate with regard to climate conditions in selected cities where they occur. We then review how near-constant and intentionally fluctuating temperatures impact development times and survival of eggs and immatures. A subset of data, generated in controlled experimental studies, from the published literature is used to plot development rates and survival of eggs, larvae, and pupae in relation to water temperature. The general shape of the relationship between water temperature and development rate is similar for eggs, larvae, and pupae. Once the lower developmental zero temperature (10-14 degrees C) is exceeded, there is a near-linear relationship up to 30 degrees C. Above this temperature, the development rate is relatively stable or even decreases slightly before falling dramatically near the upper developmental zero temperature, which occurs at -38-42 degrees C. Based on life stage-specific linear relationships between water temperature and development rate in the 15-28 degrees C range, the lower developmental zero temperature is estimated to be 14.0 degrees C for eggs, 11.8 degrees C for larvae, and 10.3 degrees C for pupae. We further conclude that available population dynamics models for Ae. aegypti, such as CIMSiM and Skeeter Buster, likely produce robust predictions based on water temperatures in the 16-35 degrees C range, which includes the geographic areas where Ae. aegypti and its associated pathogens present the greatest threat to human health, but that they may be less reliable in cool range margins where water temperatures regularly fall below 15 degrees C. Finally, we identify knowledge or data gaps that hinder our ability to predict risk of human exposure to Ae. aegypti at the cool margins of its range, now and in the future, based on impacts on mosquito population dynamics of temperature and other important factors, such as water nutrient content, larval density, presence of biological competitors, and human behavior.

Exploring unimolecular dissociation kinetics of ethyl dibromide through electronic structure calculations

NASA Astrophysics Data System (ADS)

Gulvi, Nitin R.; Patel, Priyanka; Badani, Purav M.

2018-04-01

Pathway for dissociation of multihalogenated alkyls is observed to be competitive between molecular and atomic elimination products. Factors such as molecular structure, temperature and pressure are known to influence the same. Hence present work is focussed to explore mechanism and kinetics of atomic (Br) and molecular (HBr and Br2) elimination upon pyrolysis of 1,1- and 1,2-ethyl dibromide (EDB). For this purpose, electronic structure calculations were performed at DFT and CCSD(T) level of theory. In addition to concerted mechanism, an alternate energetically efficient isomerisation pathway has been exploited for molecular elimination. Energy calculations are further complimented by detailed kinetic investigation, over wide range of temperature and pressure, using suitable models like Canonical Transition State Theory, Statistical Adiabatic Channel Model and Troe's formalism. Our calculations suggest high branching ratio for dehydrohalogentation reaction, from both isomers of EDB. Fall off curve depicts good agreement between theoretically estimated and experimentally reported values.

Phase transitions and dynamics of bulk and interfacial water.

PubMed

Franzese, G; Hernando-Martínez, A; Kumar, P; Mazza, M G; Stokely, K; Strekalova, E G; de los Santos, F; Stanley, H E

2010-07-21

New experiments on water at the surface of proteins at very low temperature display intriguing dynamic behaviors. The extreme conditions of these experiments make it difficult to explore the wide range of thermodynamic state points needed to offer a suitable interpretation. Detailed simulations suffer from the same problem, where equilibration times at low temperature become extremely long. We show how Monte Carlo simulations and mean field calculations using a tractable model of water help interpret the experimental results. Here we summarize the results for bulk water and investigate the thermodynamic and dynamic properties of supercooled water at an interface.

AN INFORMATION-THEORETIC APPROACH TO OPTIMIZE JWST OBSERVATIONS AND RETRIEVALS OF TRANSITING EXOPLANET ATMOSPHERES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howe, Alex R.; Burrows, Adam; Deming, Drake, E-mail: arhowe@umich.edu, E-mail: burrows@astro.princeton.edu, E-mail: ddeming@astro.umd.edu

We provide an example of an analysis to explore the optimization of observations of transiting hot Jupiters with the James Webb Space Telescope ( JWST ) to characterize their atmospheres based on a simple three-parameter forward model. We construct expansive forward model sets for 11 hot Jupiters, 10 of which are relatively well characterized, exploring a range of parameters such as equilibrium temperature and metallicity, as well as considering host stars over a wide range in brightness. We compute posterior distributions of our model parameters for each planet with all of the available JWST spectroscopic modes and several programs ofmore » combined observations and compute their effectiveness using the metric of estimated mutual information per degree of freedom. From these simulations, clear trends emerge that provide guidelines for designing a JWST observing program. We demonstrate that these guidelines apply over a wide range of planet parameters and target brightnesses for our simple forward model.« less

The pseudogap and the unusual excitations in the optical conductivity of Bi2Sr2CaCu2O8+δ material

NASA Astrophysics Data System (ADS)

Bhuiyan, E. H.; Azzouz, M.

2017-12-01

We studied the optical conductivity of Bi2Sr2CaCu2O8+δ material as a function of temperature and doping within the Rotating Antiferromagnetism Theory (RAFT). The optical conductivity of the material is studied from underdoped to overdoped regime for a wide range of temperatures. We mainly focused on the pseudogap state and unusual excitations in the optical conductivity. The former is realized in the underdoped to optimally doped regimes below a characteristic temperature T*, a temperature that can appreciably exceed the superconducting transition temperature TC. The latter is appeared in the optical conductivity spectra below the TC and we studied it by varying temperature. The pseudogap response is explored by changing the doping level and by varying the temperature from above to below T*. The results obtained from theories are compared with available experimental data and found a good agreement with those experimental results.

Disturbance Impacts on Thermal Hot Spots and Hot Moments at the Peatland-Atmosphere Interface

NASA Astrophysics Data System (ADS)

Leonard, R. M.; Kettridge, N.; Devito, K. J.; Petrone, R. M.; Mendoza, C. A.; Waddington, J. M.; Krause, S.

2018-01-01

Soil-surface temperature acts as a master variable driving nonlinear terrestrial ecohydrological, biogeochemical, and micrometeorological processes, inducing short-lived or spatially isolated extremes across heterogeneous landscape surfaces. However, subcanopy soil-surface temperatures have been, to date, characterized through isolated, spatially discrete measurements. Using spatially complex forested northern peatlands as an exemplar ecosystem, we explore the high-resolution spatiotemporal thermal behavior of this critical interface and its response to disturbances by using Fiber-Optic Distributed Temperature Sensing. Soil-surface thermal patterning was identified from 1.9 million temperature measurements under undisturbed, trees removed and vascular subcanopy removed conditions. Removing layers of the structurally diverse vegetation canopy not only increased mean temperatures but it shifted the spatial and temporal distribution, range, and longevity of thermal hot spots and hot moments. We argue that linking hot spots and/or hot moments with spatially variable ecosystem processes and feedbacks is key for predicting ecosystem function and resilience.

Regional geothermal exploration in Egypt

NASA Technical Reports Server (NTRS)

Morgan, P.; Boulos, F. K.; Swanberg, C. A.

1983-01-01

A study is presented of the evaluation of the potential geothermal resources of Egypt using a thermal gradient/heat flow technique and a groundwater temperature/chemistry technique. Existing oil well bottom-hole temperature data, as well as subsurface temperature measurements in existing boreholes, were employed for the thermal gradient/heat flow investigation before special thermal gradient holes were drilled. The geographic range of the direct subsurface thermal measurements was extended by employing groundwater temperature and chemistry data. Results show the presence of a regional thermal high along the eastern margin of Egypt with a local thermal anomaly in this zone. It is suggested that the sandstones of the Nubian Formation may be a suitable reservoir for geothermal fluids. These findings indicate that temperatures of 150 C or higher may be found in this reservoir in the Gulf of Suez and Red Sea coastal zones where it lies at a depth of 4 km and deeper.

Molten salts and energy related materials.

PubMed

Fray, Derek

2016-08-15

Molten salts have been known for centuries and have been used for the extraction of aluminium for over one hundred years and as high temperature fluxes in metal processing. This and other molten salt routes have gradually become more energy efficient and less polluting, but there have been few major breakthroughs. This paper will explore some recent innovations that could lead to substantial reductions in the energy consumed in metal production and in carbon dioxide production. Another way that molten salts can contribute to an energy efficient world is by creating better high temperature fuel cells and novel high temperature batteries, or by acting as the medium that can create novel materials that can find applications in high energy batteries and other energy saving devices, such as capacitors. Carbonate melts can be used to absorb carbon dioxide, which can be converted into C, CO and carbon nanoparticles. Molten salts can also be used to create black silicon that can absorb more sunlight over a wider range of wavelengths. Overall, there are many opportunities to explore for molten salts to play in an efficient, low carbon world.

An overview of thixoforming process

NASA Astrophysics Data System (ADS)

Husain, N. H.; Ahmad, A. H.; Rashidi, M. M.

2017-10-01

Thixoforming is a forming process which exploits metal rheological behaviour during solidus and liquidus range temperature. Many research works in thixoforming are currently focusing on the raw material used to produce superior mechanical properties and excellent formability components, especially in automotive industries. Furthermore, the thixoforming process also produced less casting defect component such as macrosegration, shrinkage and porosity. These advantages are sufficient to attract more exploration works of thixoforming operation. However, the weakness of this process such as high production cost due to leftover billet which cannot be recycled, encourage researcher works to overcome thixoforming limitations by using various methods. The thixoforming methods that widely used are thixocasting, thixoforging, thixorolling, thixoextrusion and thixomoulding. Each method provides varieties of final product characteristics; hence offer the extensive possibility of component invention. On the other hand, new thixoforming method leads to exploration research such as microstructure evolution, heating and pouring temperature, die temperature, mechanical properties, viscosity and final product quality. This review paper presents findings in the rheological material behaviour of thixoforming, advantages and disadvantanges of thixoforming, parameters affecting the thixoforming operation, morphology of thixoforming and various methods which have been used in this research area.

Scenario and modelling uncertainty in global mean temperature change derived from emission driven Global Climate Models

NASA Astrophysics Data System (ADS)

Booth, B. B. B.; Bernie, D.; McNeall, D.; Hawkins, E.; Caesar, J.; Boulton, C.; Friedlingstein, P.; Sexton, D.

2012-09-01

We compare future changes in global mean temperature in response to different future scenarios which, for the first time, arise from emission driven rather than concentration driven perturbed parameter ensemble of a Global Climate Model (GCM). These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle, ocean physics and aerosol sulphur cycle processes. We find broader ranges of projected temperature responses arising when considering emission rather than concentration driven simulations (with 10-90 percentile ranges of 1.7 K for the aggressive mitigation scenario up to 3.9 K for the high end business as usual scenario). A small minority of simulations resulting from combinations of strong atmospheric feedbacks and carbon cycle responses show temperature increases in excess of 9 degrees (RCP8.5) and even under aggressive mitigation (RCP2.6) temperatures in excess of 4 K. While the simulations point to much larger temperature ranges for emission driven experiments, they do not change existing expectations (based on previous concentration driven experiments) on the timescale that different sources of uncertainty are important. The new simulations sample a range of future atmospheric concentrations for each emission scenario. Both in case of SRES A1B and the Representative Concentration Pathways (RCPs), the concentration pathways used to drive GCM ensembles lies towards the lower end of our simulated distribution. This design decision (a legecy of previous assessments) is likely to lead concentration driven experiments to under-sample strong feedback responses in concentration driven projections. Our ensemble of emission driven simulations span the global temperature response of other multi-model frameworks except at the low end, where combinations of low climate sensitivity and low carbon cycle feedbacks lead to responses outside our ensemble range. The ensemble simulates a number of high end responses which lie above the CMIP5 carbon cycle range. These high end simulations can be linked to sampling a number of stronger carbon cycle feedbacks and to sampling climate sensitivities above 4.5 K. This latter aspect highlights the priority in identifying real world climate sensitivity constraints which, if achieved, would lead to reductions on the uppper bound of projected global mean temperature change. The ensembles of simulations presented here provides a framework to explore relationships between present day observables and future changes while the large spread of future projected changes, highlights the ongoing need for such work.

Mimicking Mars: a vacuum simulation chamber for testing environmental instrumentation for Mars exploration.

PubMed

Sobrado, J M; Martín-Soler, J; Martín-Gago, J A

2014-03-01

We have built a Mars environmental simulation chamber, designed to test new electromechanical devices and instruments that could be used in space missions. We have developed this environmental system aiming at validating the meteorological station Rover Environment Monitoring Station of NASA's Mars Science Laboratory mission currently installed on Curiosity rover. The vacuum chamber has been built following a modular configuration and operates at pressures ranging from 1000 to 10(-6) mbars, and it is possible to control the gas composition (the atmosphere) within this pressure range. The device (or sample) under study can be irradiated by an ultraviolet source and its temperature can be controlled in the range from 108 to 423 K. As an important improvement with respect to other simulation chambers, the atmospheric gas into the experimental chamber is cooled at the walls by the use of liquid-nitrogen heat exchangers. This chamber incorporates a dust generation mechanism designed to study Martian-dust deposition while modifying the conditions of temperature, and UV irradiated.

Study of aluminum particle combustion in solid propellant plumes using digital in-line holography and imaging pyrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yi; Guildenbecher, Daniel R.; Hoffmeister, Kathryn N. G.

The combustion of molten metals is an important area of study with applications ranging from solid aluminized rocket propellants to fireworks displays. Our work uses digital in-line holography (DIH) to experimentally quantify the three-dimensional position, size, and velocity of aluminum particles during combustion of ammonium perchlorate (AP) based solid-rocket propellants. Additionally, spatially resolved particle temperatures are simultaneously measured using two-color imaging pyrometry. To allow for fast characterization of the properties of tens of thousands of particles, automated data processing routines are proposed. In using these methods, statistics from aluminum particles with diameters ranging from 15 to 900 µm are collectedmore » at an ambient pressure of 83 kPa. In the first set of DIH experiments, increasing initial propellant temperature is shown to enhance the agglomeration of nascent aluminum at the burning surface, resulting in ejection of large molten aluminum particles into the exhaust plume. The resulting particle number and volume distributions are quantified. In the second set of simultaneous DIH and pyrometry experiments, particle size and velocity relationships as well as temperature statistics are explored. The average measured temperatures are found to be 2640 ± 282 K, which compares well with previous estimates of the range of particle and gas-phase temperatures. The novel methods proposed here represent new capabilities for simultaneous quantification of the joint size, velocity, and temperature statistics during the combustion of molten metal particles. The proposed techniques are expected to be useful for detailed performance assessment of metalized solid-rocket propellants.« less

Study of aluminum particle combustion in solid propellant plumes using digital in-line holography and imaging pyrometry

DOE PAGES

Chen, Yi; Guildenbecher, Daniel R.; Hoffmeister, Kathryn N. G.; ...

2017-05-05

The combustion of molten metals is an important area of study with applications ranging from solid aluminized rocket propellants to fireworks displays. Our work uses digital in-line holography (DIH) to experimentally quantify the three-dimensional position, size, and velocity of aluminum particles during combustion of ammonium perchlorate (AP) based solid-rocket propellants. Additionally, spatially resolved particle temperatures are simultaneously measured using two-color imaging pyrometry. To allow for fast characterization of the properties of tens of thousands of particles, automated data processing routines are proposed. In using these methods, statistics from aluminum particles with diameters ranging from 15 to 900 µm are collectedmore » at an ambient pressure of 83 kPa. In the first set of DIH experiments, increasing initial propellant temperature is shown to enhance the agglomeration of nascent aluminum at the burning surface, resulting in ejection of large molten aluminum particles into the exhaust plume. The resulting particle number and volume distributions are quantified. In the second set of simultaneous DIH and pyrometry experiments, particle size and velocity relationships as well as temperature statistics are explored. The average measured temperatures are found to be 2640 ± 282 K, which compares well with previous estimates of the range of particle and gas-phase temperatures. The novel methods proposed here represent new capabilities for simultaneous quantification of the joint size, velocity, and temperature statistics during the combustion of molten metal particles. The proposed techniques are expected to be useful for detailed performance assessment of metalized solid-rocket propellants.« less

Searching for the Haplorrhine Heterotherm: Field and Laboratory Data of Free-Ranging Tarsiers

PubMed Central

Welman, Shaun; Tuen, Andrew A.; Lovegrove, Barry G.

2017-01-01

The observation of heterothermy in a single suborder (Strepsirrhini) only within the primates is puzzling. Given that the placental-mammal ancestor was likely a heterotherm, we explored the potential for heterothermy in a primate closely related to the Strepsirrhini. Based upon phylogeny, body size and habitat stability since the Late Eocene, we selected western tarsiers (Cephalopachus bancanus) from the island of Borneo. Being the sister clade to Strepsirrhini and basal in Haplorrhini (monkeys and apes), we hypothesized that C. bancanus might have retained the heterothermic capacity observed in several small strepsirrhines. We measured resting metabolic rate, subcutaneous temperature, evaporative water loss and the percentage of heat dissipated through evaporation, at ambient temperatures between 22 and 35°C in fresh-caught wild animals (126.1 ± 2.4 g). We also measured core body temperatures in free-ranging animals. The thermoneutral zone was 25–30°C and the basal metabolic rate was 3.52 ± 0.06 W.kg−1 (0.65 ± 0.01 ml O2.g−1.h−1). There was no evidence of adaptive heterothermy in either the laboratory data or the free-ranging data. Instead, animals appeared to be cold sensitive (Tb ~ 31°C) at the lowest temperatures. We discuss possible reasons for the apparent lack of heterothermy in tarsiers, and identify putative heterotherms within Platyrrhini. We also document our concern for the vulnerability of C. bancanus to future temperature increases associated with global warming. PMID:29018365

The Impact of Cycling Temperature on the Transmission of West Nile Virus.

PubMed

Danforth, Mary E; Reisen, William K; Barker, Christopher M

2016-05-01

West Nile virus (WNV) is an important cause of disease in humans and animals. Risk of WNV infection varies seasonally, with the greatest risk during the warmest parts of the year due in part to the accelerated extrinsic incubation rate of the virus in mosquitoes. Rates of extrinsic incubation have been shown in constant-temperature studies to increase as an approximately linear function of temperature, but for other vector-borne pathogens, such as malaria or dengue virus, nonlinear relationships have been demonstrated under cycling temperatures near the thermal limits of pathogen replication. Using typical daily air temperature profiles from three key periods of WNV amplification in a hyperendemic area of WNV activity in California's Central Valley, as well as a fourth temperature profile based on exposures that would result from daily mosquito host-seeking and resting behavior, we explored the impacts of cycling temperatures on WNV transmission by Culex tarsalis Coquillett, one of the principal vectors in the western United States. The daily cycling temperature ranges studied were representative of those that occur across much of California, but they did not significantly alter the extrinsic incubation period of WNV compared with estimates from mean temperatures alone. This suggests that within the relatively broad range we studied, WNV incubation rates are a simple function of mean temperature. Realistic daily temperature patterns that reflected mosquitoes' avoidance of daytime high temperatures during summer reduced transmission over time compared with air temperatures, indicating that adjustment for mosquito exposure temperatures would be prudent for calculating risk. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Inelastic effects of Josephson junctions

NASA Astrophysics Data System (ADS)

Ranjan, Samir

We have investigated the effects of the inelastic interaction of electrons with phonons in the barrier region of S-I-S and S-N-S Josephson junctions. We find that under suitable conditions this mechanism can cause substantial modifications of the temperature dependence of the critical current jsb{c} as the inevitable loss of coherence can be more than compensated by the enhancement of the tunneling probability resulting from the phonon absorption. The effect depends strongly on the ratio qsb{TF}a of the junction width a to the screening length in the barrier region. For a S-I-S junction, a monotonic decrease in the critical current with temperature is found for qsb{TF}a ≫ 1 whereas for qsb{TF}a ≪ 1, the appearance of a peak in jsb{c}(T) near Tsb{c} is predicted. This new interesting effect is the consequence of the competition between the decrease of the superconducting gap function and the increase in the number of phonons with temperature. A wide range of parameter values has been explored and contact with relevant experimental results has been made. For an S-N-S junction, there is a large increase in the coherence length in the non-superconducting region leading to a substantial enhancement of the critical current over a wide range of temperature. It turns out that the entire temperature range can be divided broadly into two regimes. At low temperatures, the electron predominantly exchanges energy with just one phonon and it is this process that mainly determines the critical current. At higher temperatures the critical current is determined by processes in which the electrons exchange energy with many phonons during their under barrier motion.

Cloacal evaporative cooling: a previously undescribed means of increasing evaporative water loss at higher temperatures in a desert ectotherm, the Gila monster Heloderma suspectum.

PubMed

DeNardo, Dale F; Zubal, Tricia E; Hoffman, Ty C M

2004-02-01

The Gila monster Heloderma suspectum is an active forager in an environment that, at times, can be extremely hot and arid. Thus, Gila monsters face extreme thermostatic and hydrostatic demands. For a desert ectotherm routinely risking dehydration, evaporative water loss (EWL) is typically viewed as detrimental. Yet evaporation simultaneously dehydrates and cools an animal. We explored EWL in Gila monsters by measuring cutaneous, ventilatory and cloacal EWL at five ambient temperatures between 20.5 degrees C and 40 degrees C. Our results show that Gila monsters have high EWL rates relative to body mass. Cutaneous EWL underwent a consistent, temperature-dependent increase over the entire range of test temperatures (Q(10)=1.61, with EWL ranging from 0.378 to 0.954 mg g(-1) h(-1)). Ventilatory EWL did not show a significant temperature-dependent response, but ranged from 0.304 to 0.663 mg g(-1) h(-1). Cloacal EWL was extremely low and relatively constant between 20.5 degrees C and 35 degrees C, but rose dramatically above 35 degrees C (Q(10) >8.3 x 10(7), from 0.0008 at 35 degrees C to 7.30 mg g(-1) h(-1) at 40 degrees C). This steep rise in cloacal EWL coincided with an increasing suppression of body temperature relative to ambient temperature. Dehydration to 80% of initial body mass led to a delay in the onset and an attenuation of the dramatic increase in cloacal EWL. These results emphasize the potential value of EWL for thermoregulation in ectotherms and demonstrate for the first time the role of the cloaca in this process.

Optimal integration strategies for a syngas fuelled SOFC and gas turbine hybrid

NASA Astrophysics Data System (ADS)

Zhao, Yingru; Sadhukhan, Jhuma; Lanzini, Andrea; Brandon, Nigel; Shah, Nilay

This article aims to develop a thermodynamic modelling and optimization framework for a thorough understanding of the optimal integration of fuel cell, gas turbine and other components in an ambient pressure SOFC-GT hybrid power plant. This method is based on the coupling of a syngas-fed SOFC model and an associated irreversible GT model, with an optimization algorithm developed using MATLAB to efficiently explore the range of possible operating conditions. Energy and entropy balance analysis has been carried out for the entire system to observe the irreversibility distribution within the plant and the contribution of different components. Based on the methodology developed, a comprehensive parametric analysis has been performed to explore the optimum system behavior, and predict the sensitivity of system performance to the variations in major design and operating parameters. The current density, operating temperature, fuel utilization and temperature gradient of the fuel cell, as well as the isentropic efficiencies and temperature ratio of the gas turbine cycle, together with three parameters related to the heat transfer between subsystems are all set to be controllable variables. Other factors affecting the hybrid efficiency have been further simulated and analysed. The model developed is able to predict the performance characteristics of a wide range of hybrid systems potentially sizing from 2000 to 2500 W m -2 with efficiencies varying between 50% and 60%. The analysis enables us to identify the system design tradeoffs, and therefore to determine better integration strategies for advanced SOFC-GT systems.

A study of the phase transition behaviour of [(NH4)0.63Li0.37]2TeBr6

NASA Astrophysics Data System (ADS)

Karray, R.; Linda, D.; Van Der Lee, A.; Ben Salah, A.; Kabadou, A.

2012-02-01

The mixed hexabromotellurate [(NH4)0.63Li0.37]2TeBr6, presenting at room temperature a K2PtCl6-type structure with space group Fm bar 3 m, exhibits three anomalies at 195, 395 and 498 K in the differential scanning calorimetry diagram. Different techniques: dielectric investigation, High-temperature X-ray powder diffraction and infrared spectroscopic study, in the range temperature (300-470) K are applied to explore the phase transition around 395 K. Combining XRD, dielectric and differential scanning calorimetry (DSC) results, no phase transition leading to a super-ionic conductivity phase is found. At high temperature, [(NH4)0.63Li0.37]2TeBr6 is characterized by a medium conductivity σ453≈ 10-4 Ω-1m-1.

In-situ neutron diffraction characterization of temperature dependence deformation in α-uranium

NASA Astrophysics Data System (ADS)

Calhoun, C. A.; Garlea, E.; Sisneros, T. A.; Agnew, S. R.

2018-04-01

In-situ strain neutron diffraction measurements were conducted at temperature on specimens coming from a clock-rolled α-uranium plate, and Elasto-Plastic Self-Consistent (EPSC) modeling was employed to interpret the findings. The modeling revealed that the active slip systems exhibit a thermally activated response, while deformation twinning remains athermal over the temperature ranges explored (25-150 °C). The modeling also allowed assessment of the effects of thermal residual stresses on the mechanical response during compression. These results are consistent with those from a prior study of room-temperature deformation, indicating that the thermal residual stresses strongly influence the internal strain evolution of grain families, as monitored with neutron diffraction, even though accounting for these residual stresses has little effect on the macroscopic flow curve, except in the elasto-plastic transition.

Exploring the protein folding free energy landscape: coupling replica exchange method with P3ME/RESPA algorithm.

PubMed

Zhou, Ruhong

2004-05-01

A highly parallel replica exchange method (REM) that couples with a newly developed molecular dynamics algorithm particle-particle particle-mesh Ewald (P3ME)/RESPA has been proposed for efficient sampling of protein folding free energy landscape. The algorithm is then applied to two separate protein systems, beta-hairpin and a designed protein Trp-cage. The all-atom OPLSAA force field with an explicit solvent model is used for both protein folding simulations. Up to 64 replicas of solvated protein systems are simulated in parallel over a wide range of temperatures. The combined trajectories in temperature and configurational space allow a replica to overcome free energy barriers present at low temperatures. These large scale simulations reveal detailed results on folding mechanisms, intermediate state structures, thermodynamic properties and the temperature dependences for both protein systems.

Hemoglobin Dynamics in Red Blood Cells: Correlation to Body Temperature

PubMed Central

Stadler, A. M.; Digel, I.; Artmann, G. M.; Embs, J. P.; Zaccai, G.; Büldt, G.

2008-01-01

A transition in hemoglobin behavior at close to body temperature has been discovered recently by micropipette aspiration experiments on single red blood cells (RBCs) and circular dichroism spectroscopy on hemoglobin solutions. The transition temperature was directly correlated to the body temperatures of a variety of species. In an exploration of the molecular basis for the transition, we present neutron scattering measurements of the temperature dependence of hemoglobin dynamics in whole human RBCs in vivo. The data reveal a change in the geometry of internal protein motions at 36.9°C, at human body temperature. Above that temperature, amino acid side-chain motions occupy larger volumes than expected from normal temperature dependence, indicating partial unfolding of the protein. Global protein diffusion in RBCs was also measured and the findings compared favorably with theoretical predictions for short-time self-diffusion of noncharged hard-sphere colloids. The results demonstrated that changes in molecular dynamics in the picosecond time range and angstrom length scale might well be connected to a macroscopic effect on whole RBCs that occurs at body temperature. PMID:18708462

Hemoglobin dynamics in red blood cells: correlation to body temperature.

PubMed

Stadler, A M; Digel, I; Artmann, G M; Embs, J P; Zaccai, G; Büldt, G

2008-12-01

A transition in hemoglobin behavior at close to body temperature has been discovered recently by micropipette aspiration experiments on single red blood cells (RBCs) and circular dichroism spectroscopy on hemoglobin solutions. The transition temperature was directly correlated to the body temperatures of a variety of species. In an exploration of the molecular basis for the transition, we present neutron scattering measurements of the temperature dependence of hemoglobin dynamics in whole human RBCs in vivo. The data reveal a change in the geometry of internal protein motions at 36.9 degrees C, at human body temperature. Above that temperature, amino acid side-chain motions occupy larger volumes than expected from normal temperature dependence, indicating partial unfolding of the protein. Global protein diffusion in RBCs was also measured and the findings compared favorably with theoretical predictions for short-time self-diffusion of noncharged hard-sphere colloids. The results demonstrated that changes in molecular dynamics in the picosecond time range and angstrom length scale might well be connected to a macroscopic effect on whole RBCs that occurs at body temperature.

Adaptive capacity at the northern front: sockeye salmon behaviourally thermoregulate during novel exposure to warm temperatures

PubMed Central

Armstrong, Jonathan B.; Ward, Eric J.; Schindler, Daniel E.; Lisi, Peter J.

2016-01-01

As climate change increases maximal water temperatures, behavioural thermoregulation may be crucial for the persistence of coldwater fishes, such as salmonids. Although myriad studies have documented behavioural thermoregulation in southern populations of salmonids, few if any have explored this phenomenon in northern populations, which are less likely to have an evolutionary history of heat stress, yet are predicted to experience substantial warming. Here, we treated a rare heat wave as a natural experiment to test whether wild sockeye salmon (Oncorhynchus nerka) at the northern extent of their primary range (60° latitude) can thermoregulate in response to abnormally high thermal conditions. We tagged adult sockeye salmon with temperature loggers as they staged in a lake epilimnion prior to spawning in small cold streams (n = 40 recovered loggers). As lake surface temperatures warmed to physiologically suboptimal levels (15–20°C), sockeye salmon thermoregulated by moving to tributary plumes or the lake metalimnion. A regression of fish body temperature against lake surface temperature indicated that fish moved to cooler waters when the epilimnion temperature exceeded ~12°C. A bioenergetics model suggested that the observed behaviour reduced daily metabolic costs by as much as ~50% during the warmest conditions (18–20°C). These results provide rare evidence of cool-seeking thermoregulation at the poleward extent of a species range, emphasizing the potential ubiquity of maximal temperature constraints and the functional significance of thermal heterogeneity for buffering poikilotherms from climate change. PMID:27729980

Paris and its long-term temperature goal: First steps on a long road

NASA Astrophysics Data System (ADS)

Rogelj, J.

2017-12-01

As a means to achieve its long-term temperature goal, the Paris Agreement put in place a system of regularly updated country pledges alternating with global stocktaking exercises that assess progress towards achieving the Paris goals. By now, the vast majority of countries have submitted their intended actions (also known as Nationally Determined Contributions - NDCs). This begs the question what these amount to and whether they are in line with the agreement`s long-term temperature goal. A structured sensitivity analysis of the emissions implications of the Paris pledges has been carried out, showing that the ambiguity and imprecision of the NDCs leaves open a wide range of possible outcomes by 2030. This range has important implications for the feasibility and cost of pathways that attempt to limit warming to the temperature goals of the Agreement. We identify salient steps to reduce the overall uncertainty, and explore the minimum requirements that have to be met for integrated energy-economy-land models to still find options to stay within the temperature limits of the Paris Agreement. These requirements come under the form of near-term emissions reductions, and assumptions about the deployment of carbon-dioxide removal technologies in the second half of the century.

Performance of MEMS Silicon Oscillator, ASFLM1, under Wide Operating Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2008-01-01

Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to be offered as commercial-off-the-shelf (COTS) parts by a few companies [1-2]. These quartz-free, miniature silicon devices could compete with the traditional crystal oscillators in providing the timing (clock function) for many digital and analog electronic circuits. They provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [1-2]. In addition, they are encapsulated in compact lead-free packages, cover a wide frequency range (1 MHz to 125 MHz), and are specified, depending on the grade, for extended temperature operation from -40 C to +85 C. The small size of the MEMS oscillators along with their reliability and thermal stability make them candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an ABRACON Corporation MEMS silicon oscillator chip, type ASFLM1, under extreme temperatures.

Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavrentiev, M. Yu., E-mail: Mikhail.Lavrentiev@ukaea.uk; Nguyen-Manh, D.; Dudarev, S. L.

A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rathermore » than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.« less

Thermal conductivity of high purity synthetic single crystal diamonds

NASA Astrophysics Data System (ADS)

Inyushkin, A. V.; Taldenkov, A. N.; Ralchenko, V. G.; Bolshakov, A. P.; Koliadin, A. V.; Katrusha, A. N.

2018-04-01

Thermal conductivity of three high purity synthetic single crystalline diamonds has been measured with high accuracy at temperatures from 6 to 410 K. The crystals grown by chemical vapor deposition and by high-pressure high-temperature technique demonstrate almost identical temperature dependencies κ (T ) and high values of thermal conductivity, up to 24 W cm-1K-1 at room temperature. At conductivity maximum near 63 K, the magnitude of thermal conductivity reaches 285 W cm-1K-1 , the highest value ever measured for diamonds with the natural carbon isotope composition. Experimental data were fitted with the classical Callaway model for the lattice thermal conductivity. A set of expressions for the anharmonic phonon scattering processes (normal and umklapp) has been proposed which gives an excellent fit to the experimental κ (T ) data over almost the whole temperature range explored. The model provides the strong isotope effect, nearly 45%, and the high thermal conductivity (>24 W cm-1K-1 ) for the defect-free diamond with the natural isotopic abundance at room temperature.

Laser-induced fluorescence measurement of the oil film thickness in an internal combustion engine

NASA Astrophysics Data System (ADS)

Ostroski, Greg M.; Ghandhi, Jaal B.

1997-11-01

The use of a fluorescent dopant molecule to enhance the natural fluorescence of motor oils, and allow quantitative determination of temperature and film thickens in internal combustion engines has been investigated. Measurement of the fluorescence as a function of temperature were made with neat Mobil 1, and solutions of the dopant BTBP in mineral oil and Mobil 1. The fluorescence yield of neat Mobil 1 was found to vary by 30 percent over the temperature range explored, but the spectral characteristics, as measured with bandpass filters, were unaffected by temperature. The BTBP fluorescence was found to increase significantly with temperature, and it was found the narrower regions in the spectrum increased proportionally more than the fluorescence collected over the entire spectrum, allowing a determination of temperature to be made which can then be used to correct for the change in fluorescence yield. Solutions in Mobil 1 showed a smaller increase than that observed in mineral oil.

Transition of temporal scaling behavior in percolation assisted shear-branching structure during plastic deformation

DOE PAGES

Ren, Jingli; Chen, Cun; Wang, Gang; ...

2017-03-22

This study explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10 –2 s –1; the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at themore » intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10 –2 s –1.« less

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

NASA Technical Reports Server (NTRS)

Antolovich, Stephen D.; Saxena, Ashok; Cullers, Cheryl

1992-01-01

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though, probing the deformation mechanisms operating in fatigue will lead to a better understanding of NiAl's unique characteristics. Low cycle fatigue properties have been reported on binary NiAl in the past year, yet those studies were limited to two temperature ranges: room temperature and near 1000 K. Eventually, fatigue property data will be needed for a wide range of temperatures and compositions. The intermediate temperature range near the brittle-to-ductile transition was chosen for this study to ascertain whether the sharp change occurring in monotonic behavior also occurs under cyclic conditions. An effort was made to characterize the dislocation structures which evolved during fatigue testing and comment on their role in the deformation process.

Exploration of Venus with the Venera-15 IR Fourier spectrometer and the Venus Express planetary Fourier spectrometer

NASA Astrophysics Data System (ADS)

Zasova, L. V.; Moroz, V. I.; Formisano, V.; Ignatiev, N. I.; Khatuntsev, I. V.

2006-07-01

The infrared spectrometry of Venus in the range 6-45 μm allows one to sound the middle atmosphere of Venus in the altitude range 55-100 km and its cloud layer. This experiment was carried out onboard the Soviet automatic interplanetary Venera-15 station, where the Fourier spectrometer for this spectral range was installed. The measurements have shown that the main component of the cloud layer at all measured latitudes in the northern hemisphere is concentrated sulfuric acid (75-85%). The vertical profiles of temperature and aerosol were reconstructed in a self-consistent manner: the three-dimensional fields of temperature and zonal wind in the altitude range 55-100 km and aerosol at altitudes 55-70 km have been obtained, as well as vertical SO2 profiles and H2O concentration in the upper cloud layer. The solar-related waves at isobaric levels in the fields of temperature, zonal wind, and aerosol were investigated. This experiment has shown the efficiency of the method for investigation of the Venusian atmosphere. The Planetary Fourier Spectrometer has the spectral interval 0.9-45 μm and a spectral resolution of 1.8 cm-1. It will allow one to sound the middle atmosphere (55-100 km) of Venus and its cloud layer on the dayside, as well as the lower atmosphere and the planetary surface on the night side.

Poster 2:Ab initio calculations of low temperature hydrocarbon spectra for astrophysics: application to the modeling of methane absorption in the Titan atmosphere in a wide IR range

NASA Astrophysics Data System (ADS)

Rey, Michael; Nikitin, Andrei; Bezard, Bruno; Rannou, Pascal; Coustenis, Athena; Tyuterev, Vladimir

2016-06-01

Knowledge of intensities of spectral transitions in various temperature ranges including very low-T conditions is essential for the modeling of optical properties of planetary atmospheres and for other astrophysical applications. The temperature dependence of spectral features is crucial, but quantified experimental information in a wide spectral range is generally missing. A significant progress has been recently achieved in first principles quantum mechanical predictions (ab initio electronic structure + variational nuclear motion calculations) of rotationally resolved spectra for hydrocarbon molecules such as methane , ethylene and their isotopic species [1,2] . We have recently reported the TheoReTS information system (theorets.univ-reims.fr, theorets.tsu.ru) for theoretical spectra based on variational predictions from molecular potential energy and dipole moment surfaces [3] that permits online simulation of radiative properties including low-T conditions of cold planets. In this work, we apply ab initio predictions of the spectra of methane isotopologues down to T=80 K for the modeling of the transmittance in the atmosphere of Titan, Saturn's largest satellite explored by the Cassini-Huygens space mission. A very good agreement over the whole infrared range from 6,000 to 11,000 cm-1 compared with observations obtained by the Descent Imager / Spectral Radiometer (DISR) on the Huygens probe [4,5] at various altitudes will be reported.

Climate and land cover effects on the temperature of Puget Sound streams: Assessment of Climate and Land Use Impacts on Stream Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Qian; Sun, Ning; Yearsley, John

We apply an integrated hydrology-stream temperature modeling system, DHSVM-RBM, to examine the response of the temperature of the major streams draining to Puget Sound to land cover and climate change. We first show that the model construct is able to reconstruct observed historic streamflow and stream temperature variations at a range of time scales. We then explore the relative effect of projected future climate and land cover change, including riparian vegetation, on streamflow and stream temperature. Streamflow in summer is likely to decrease as the climate warms especially in snowmelt-dominated and transient river basins despite increased streamflow in their lowermore » reaches associated with urbanization. Changes in streamflow also result from changes in land cover, and changes in stream shading result from changes in riparian vegetation, both of which influence stream temperature. However, we find that the effect of riparian vegetation changes on stream temperature is much greater than land cover change over the entire basin especially during summer low flow periods. Furthermore, while future projected precipitation change will have relatively modest effects on stream temperature, projected future air temperature increases will result in substantial increases in stream temperature especially in summer. These summer stream temperature increases will be associated both with increasing air temperature, and projected decreases in low flows. We find that restoration of riparian vegetation could mitigate much of the projected summer stream temperature increases. We also explore the contribution of riverine thermal loadings to the heat balance of Puget Sound, and find that the riverine contribution is greatest in winter, when streams account for up to 1/8 of total thermal inputs (averaged from December through February), with larger effects in some sub-basins. We project that the riverine impact on thermal inputs to Puget Sound will become greater with both urbanization and climate change in winter but become smaller in summer due to climate change.« less

Thermally activated TRP channels: molecular sensors for temperature detection.

PubMed

Castillo, Karen; Diaz-Franulic, Ignacio; Canan, Jonathan; Gonzalez-Nilo, Fernando; Latorre, Ramon

2018-01-24

Temperature sensing is one of the oldest capabilities of living organisms, and is essential for sustaining life, because failure to avoid extreme noxious temperatures can result in tissue damage or death. A subset of members of the transient receptor potential (TRP) ion channel family is finely tuned to detect temperatures ranging from extreme cold to noxious heat, giving rise to thermoTRP channels. Structural and functional experiments have shown that thermoTRP channels are allosteric proteins, containing different domains that sense changes in temperature, among other stimuli, triggering pore opening. Although temperature-dependence is well characterized in thermoTRP channels, the molecular nature of temperature-sensing elements remains unknown. Importantly, thermoTRP channels are involved in pain sensation, related to pathological conditions. Here, we provide an overview of thermoTRP channel activation. We also discuss the structural and functional evidence supporting the existence of an intrinsic temperature sensor in this class of channels, and we explore the basic thermodynamic principles for channel activation. Finally, we give a view of their role in painful pathophysiological conditions.

Investigation of the turbulent wind field below 500 feet altitude at the Eastern Test Range, Florida

NASA Technical Reports Server (NTRS)

Blackadar, A. K.; Panofsky, H. A.; Fiedler, F.

1974-01-01

A detailed analysis of wind profiles and turbulence at the 150 m Cape Kennedy Meteorological Tower is presented. Various methods are explored for the estimation of wind profiles, wind variances, high-frequency spectra, and coherences between various levels, given roughness length and either low-level wind and temperature data, or geostrophic wind and insolation. The relationship between planetary Richardson number, insolation, and geostrophic wind is explored empirically. Techniques were devised which resulted in surface stresses reasonably well correlated with the surface stresses obtained from low-level data. Finally, practical methods are suggested for the estimation of wind profiles and wind statistics.

Evaluation of a Programmable Voltage-Controlled MEMS Oscillator, Type SiT3701, Over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Semiconductor chips based on MEMS (Micro-Electro-Mechanical Systems) technology, such as sensors, transducers, and actuators, are becoming widely used in today s electronics due to their high performance, low power consumption, tolerance to shock and vibration, and immunity to electro-static discharge. In addition, the MEMS fabrication process allows for the miniaturization of individual chips as well as the integration of various electronic circuits into one module, such as system-on-a-chip. These measures would simplify overall system design, reduce parts count and interface, improve reliability, and reduce cost; and they would meet requirements of systems destined for use in space exploration missions. In this work, the performance of a recently-developed MEMS voltage-controlled oscillator was evaluated under a wide temperature range. Operation of this new commercial-off-the-shelf (COTS) device was also assessed under thermal cycling to address some operational conditions of the space environment

Crop-climate relationships of cereals in Greece and the impacts of recent climate trends

NASA Astrophysics Data System (ADS)

Mavromatis, Theodoros

2015-05-01

Notwithstanding technological developments, agricultural production is still affected by uncontrollable factors, such weather and climate. Within this context, the present study aims at exploring the relative influence of growing season climate on the yields of major cereals (hard and soft wheat, maize, and barley) on a regional scale in Greece. To this end, crop-climate relationships and the impacts of climate trends over the period 1978-2005 were explored using linear regression and change point analysis (CPA). Climate data used include maximum (Tx) and minimum temperature (Tn), diurnal temperature range (Tr), precipitation (Prec), and solar radiation (Rad). Temperature effects were the most substantial. Yields reduced by 1.8-7.1 %/°C with increasing Tx and by 1.4-6.1 %/°C with decreasing Tr. The warming trends of Tn caused bilateral yield effects (from -3.7 to 8.4 %/°C). The fewer significantly increasing Rad and decreasing Prec anomalies were associated with larger yield decreases (within the range of 2.2 % MJ/m2/day (for maize) to 4.9 % MJ/m2/day (for hard wheat)) and smaller yield increases (from 0.04 to 1.4 %/mm per decade), respectively. Wheat and barley—the most vulnerable cereals—were most affected by the trends of extreme temperatures and least by Tr. On the contrary, solar radiation has proven to be the least affecting climate variable on all cereals. Despite the similarity in the direction of crop responses with both analyses, yield changes were much more substantial in the case of CPA analysis. In conclusion, regional climate change has affected Greek cereal productivity, in a few, but important for cereal production, regions. The results of this study are expected to be valuable in anticipating the effects of weather/climate on other warm regions worldwide, where the upper temperature limit for some cereals and further changes in climate may push them past suitability for their cultivation.

Predicting species richness and distribution ranges of centipedes at the northern edge of Europe

NASA Astrophysics Data System (ADS)

Georgopoulou, Elisavet; Djursvoll, Per; Simaiakis, Stylianos M.

2016-07-01

In recent decades, interest in understanding species distributions and exploring processes that shape species diversity has increased, leading to the development of advanced methods for the exploitation of occurrence data for analytical and ecological purposes. Here, with the use of georeferenced centipede data, we explore the importance and contribution of bioclimatic variables and land cover, and predict distribution ranges and potential hotspots in Norway. We used a maximum entropy analysis (Maxent) to model species' distributions, aiming at exploring centres of distribution, latitudinal spans and northern range boundaries of centipedes in Norway. The performance of all Maxent models was better than random with average test area under the curve (AUC) values above 0.893 and True Skill Statistic (TSS) values above 0.593. Our results showed a highly significant latitudinal gradient of increased species richness in southern grid-cells. Mean temperatures of warmest and coldest quarters explained much of the potential distribution of species. Predictive modelling analyses revealed that south-eastern Norway and the Atlantic coast in the west (inclusive of the major fjord system of Sognefjord), are local biodiversity hotspots with regard to high predictive species co-occurrence. We conclude that our predicted northward shifts of centipedes' distributions in Norway are likely a result of post-glacial recolonization patterns, species' ecological requirements and dispersal abilities.

The terrestrial plasma source - A new perspective in solar-terrestrial processes from Dynamics Explorer

NASA Technical Reports Server (NTRS)

Chappell, Charles R.

1988-01-01

The geospace environment has been viewed as a mixing bowl for plasmas of both solar and terrestrial origin. The present perspective on the nature of the supply mechanisms has undergone a radical evolution over the past decade, particularly during the five years of the Dynamics Explorer mission. During this period, the terrestrial source has increased in importance in both magnitude and character of ionospheric outflow. These outflows include the classical polar wind, the cleft ion fountain, the auroral ion fountain, and the polar cap. The earth can be envisioned as a multifaceted fountain which ejects particles from different spatial locations spread around the globe. These particles exhibit a range of masses from 1 to 32 amu and a range of energies from 1 eV to 10 keV. The total flux of this ionospheric outflow is very large: adequate to supply the entire magnetospheric particle population. And the implications of the outflow are significant across a broad spectrum of solar-terrestrial processes ranging from sources of magnetospheric plasmas, to influences on ionospheric density and temperature structure, to energy transfer in phenomena such as stable auroral red arcs. The Dynamics Explorer mission has made a major contribution in the characterization of the terrestrial plasma source.

Apparatus for dynamic and static measurements of mechanical properties of solids and of flux-lattice in type-II superconductors at low frequency (10 - 5-10 Hz) and temperature (4.7-500 K)

NASA Astrophysics Data System (ADS)

D'Anna, G.; Benoit, W.

1990-12-01

A forced torsional pendulum which permits us to examine anelastic mechanical properties of solids as well as for flux-lattice in type-II superconductors, has been built to explore the low frequency and low temperature range. It works on the principle of dynamic frequency response function measurement and appears to be a powerful instrument for studying structural defect motions as well as flux line dynamics. As an additional quantity, the magnetization or the plastic strain can be statically measured by the same apparatus.

Exploration on anion ordering, optical properties and electronic structure in K3WO3F3 elpasolite

NASA Astrophysics Data System (ADS)

Atuchin, V. V.; Isaenko, L. I.; Kesler, V. G.; Lin, Z. S.; Molokeev, M. S.; Yelisseyev, A. P.; Zhurkov, S. A.

2012-03-01

Room-temperature modification of potassium oxyfluorotungstate, G2-K3WO3F3, has been prepared by low-temperature chemical route and single crystal growth. Wide optical transparency range of 0.3-9.4 μm and forbidden band gap Eg=4.32 eV have been obtained for G2-K3WO3F3 crystal. Meanwhile, its electronic structure has been calculated with the first-principles calculations. The good agreement between the theorectical and experimental results have been achieved. Furthermore, G2-K3WO3F3 is predicted to possess the relatively large nonlinear optical coefficients.

Resonances at very low temperature for the reaction D2 + H

NASA Astrophysics Data System (ADS)

Simbotin, I.; Côté, R.

2017-05-01

We present numerical results for rate coefficients of reaction and vibrational quenching in the collision of H with {{{D}}}2(v,j) at cold and ultracold temperatures. We explore both ortho-D{}2(j=0) and para-D{}2(j=1) for several initial vibrational states (v≤slant 5), and find resonant structures in the energy range 0.01-10 K, which are sensitive to the initial rovibrational state (v, j). We compare the reaction rates for D2 + H with our previously obtained results for the isotopologue reaction H2 + D, and discuss the implications of our detailed study of this benchmark system for ultracold chemistry.

Leakage conduction behavior in electron-beam-cured nanoporous silicate films

NASA Astrophysics Data System (ADS)

Liu, Po-Tsun; Tsai, T. M.; Chang, T. C.

2005-05-01

This letter explores the application of electron-beam curing on nanoporous silicate films. The electrical conduction mechanism for the nanoporous silicate film cured by electron-beam radiation has been studied with metal-insulator-semiconductor capacitors. Electrical analyses over a varying temperature range from room temperature to 150°C provide evidence for space-charge-limited conduction in the electron-beam-cured thin film, while Schottky-emission-type leaky behavior is seen in the counterpart typically cured by a thermal furnace. A physical model consistent with electrical analyses is also proposed to deduce the origin of conduction behavior in the nanoporous silicate thin film.

Climatic niche and flowering and fruiting phenology of an epiphytic plant

PubMed Central

Barve, Narayani; Martin, Craig E.; Peterson, A. Townsend

2015-01-01

Species have geographic distributions constrained by combinations of abiotic factors, biotic factors and dispersal-related factors. Abiotic requirements vary across the life stages for a species; for plant species, a particularly important life stage is when the plant flowers and develops seeds. A previous year-long experiment showed that ambient temperature of 5–35 °C, relative humidity of >50 % and ≤15 consecutive rainless days are crucial abiotic conditions for Spanish moss (Tillandsia usneoides L.). Here, we explore whether these optimal physiological intervals relate to the timing of the flowering and fruiting periods of Spanish moss across its range. As Spanish moss has a broad geographic range, we examined herbarium specimens to detect and characterize flowering/fruiting periods for the species across the Americas; we used high-temporal-resolution climatic data to assess the availability of optimal conditions for Spanish moss populations during each population's flowering period. We explored how long populations experience suboptimal conditions and found that most populations experience suboptimal conditions in at least one environmental dimension. Flowering and fruiting periods of Spanish moss populations are either being optimized for one or a few parameters or may be adjusted such that all parameters are suboptimal. Spanish moss populations appear to be constrained most closely by minimum temperature during this period. PMID:26359490

Are the Antarctic dipteran, Eretmoptera murphyi, and Arctic collembolan, Megaphorura arctica, vulnerable to rising temperatures?

PubMed

Everatt, M J; Convey, P; Worland, M R; Bale, J S; Hayward, S A L

2014-08-01

Polar terrestrial invertebrates are suggested as being vulnerable to temperature change relative to lower latitude species, and hence possibly also to climate warming. Previous studies have shown Antarctic and Arctic Collembola and Acari to possess good heat tolerance and survive temperature exposures above 30 °C. To test this feature further, the heat tolerance and physiological plasticity of heat stress were explored in the Arctic collembolan, Megaphorura arctica, from Svalbard and the Antarctic midge, Eretmoptera murphyi, from Signy Island. The data obtained demonstrate considerable heat tolerance in both species, with upper lethal temperatures ≥35 °C (1 h exposures), and tolerance of exposure to 10 and 15 °C exceeding 56 days. This tolerance is far beyond that required in their current environment. Average microhabitat temperatures in August 2011 ranged between 5.1 and 8.1 °C, and rarely rose above 10 °C, in Ny-Ålesund, Svalbard. Summer soil microhabitat temperatures on Signy Island have previously been shown to range between 0 and 10 °C. There was also evidence to suggest that E. murphyi can recover from high-temperature exposure and that M. arctica is capable of rapid heat hardening. M. arctica and E. murphyi therefore have the physiological capacity to tolerate current environmental conditions, as well as future warming. If the features they express are characteristically more general, such polar terrestrial invertebrates will likely fare well under climate warming scenarios.

Thermal fluctuations of haemoglobin from different species: adaptation to temperature via conformational dynamics

PubMed Central

Stadler, A. M.; Garvey, C. J.; Bocahut, A.; Sacquin-Mora, S.; Digel, I.; Schneider, G. J.; Natali, F.; Artmann, G. M.; Zaccai, G.

2012-01-01

Thermodynamic stability, configurational motions and internal forces of haemoglobin (Hb) of three endotherms (platypus, Ornithorhynchus anatinus; domestic chicken, Gallus gallus domesticus and human, Homo sapiens) and an ectotherm (salt water crocodile, Crocodylus porosus) were investigated using circular dichroism, incoherent elastic neutron scattering and coarse-grained Brownian dynamics simulations. The experimental results from Hb solutions revealed a direct correlation between protein resilience, melting temperature and average body temperature of the different species on the 0.1 ns time scale. Molecular forces appeared to be adapted to permit conformational fluctuations with a root mean square displacement close to 1.2 Å at the corresponding average body temperature of the endotherms. Strong forces within crocodile Hb maintain the amplitudes of motion within a narrow limit over the entire temperature range in which the animal lives. In fully hydrated powder samples of human and chicken, Hb mean square displacements and effective force constants on the 1 ns time scale showed no differences over the whole temperature range from 10 to 300 K, in contrast to the solution case. A complementary result of the study, therefore, is that one hydration layer is not sufficient to activate all conformational fluctuations of Hb in the pico- to nanosecond time scale which might be relevant for biological function. Coarse-grained Brownian dynamics simulations permitted to explore residue-specific effects. They indicated that temperature sensing of human and chicken Hb occurs mainly at residues lining internal cavities in the β-subunits. PMID:22696485

Thermal fluctuations of haemoglobin from different species: adaptation to temperature via conformational dynamics.

PubMed

Stadler, A M; Garvey, C J; Bocahut, A; Sacquin-Mora, S; Digel, I; Schneider, G J; Natali, F; Artmann, G M; Zaccai, G

2012-11-07

Thermodynamic stability, configurational motions and internal forces of haemoglobin (Hb) of three endotherms (platypus, Ornithorhynchus anatinus; domestic chicken, Gallus gallus domesticus and human, Homo sapiens) and an ectotherm (salt water crocodile, Crocodylus porosus) were investigated using circular dichroism, incoherent elastic neutron scattering and coarse-grained Brownian dynamics simulations. The experimental results from Hb solutions revealed a direct correlation between protein resilience, melting temperature and average body temperature of the different species on the 0.1 ns time scale. Molecular forces appeared to be adapted to permit conformational fluctuations with a root mean square displacement close to 1.2 Å at the corresponding average body temperature of the endotherms. Strong forces within crocodile Hb maintain the amplitudes of motion within a narrow limit over the entire temperature range in which the animal lives. In fully hydrated powder samples of human and chicken, Hb mean square displacements and effective force constants on the 1 ns time scale showed no differences over the whole temperature range from 10 to 300 K, in contrast to the solution case. A complementary result of the study, therefore, is that one hydration layer is not sufficient to activate all conformational fluctuations of Hb in the pico- to nanosecond time scale which might be relevant for biological function. Coarse-grained Brownian dynamics simulations permitted to explore residue-specific effects. They indicated that temperature sensing of human and chicken Hb occurs mainly at residues lining internal cavities in the β-subunits.

Operation of a New Half-Bridge Gate Driver for Enhancement - Mode GaN FETs, Type LM5113, Over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2011-01-01

A new commercial-off-the-shelf (COTS) gate driver designed to drive both the high-side and the low-side enhancement-mode GaN FETs, National Semiconductor's type LM5113, was evaluated for operation at temperatures beyond its recommended specified limits of -40 C to +125 C. The effects of limited thermal cycling under the extended test temperature, which ranged from -194 C to +150 C, on the operation of this chip as well as restart capability at the extreme cryogenic and hot temperatures were also investigated. The driver circuit was able to maintain good operation throughout the entire test regime between -194 C and +150 C without undergoing any major changes in its outputs signals and characteristics. The limited thermal cycling performed on the device also had no effect on its performance, and the driver chip was able to successfully restart at each of the extreme temperatures of -194 C and +150 C. The plastic packaging of this device was also not affected by either the short extreme temperature exposure or the limited thermal cycling. These preliminary results indicate that this new commercial-off-the-shelf (COTS) halfbridge eGaN FET driver integrated circuit has the potential for use in space exploration missions under extreme temperature environments. Further testing is planned under long-term cycling to assess the reliability of these parts and to determine their suitability for extended use in the harsh environments of space.

Surface tensions of inorganic multicomponent aqueous electrolyte solutions and melts.

PubMed

Dutcher, Cari S; Wexler, Anthony S; Clegg, Simon L

2010-11-25

A semiempirical model is presented that predicts surface tensions (σ) of aqueous electrolyte solutions and their mixtures, for concentrations ranging from infinitely dilute solution to molten salt. The model requires, at most, only two temperature-dependent terms to represent surface tensions of either pure aqueous solutions, or aqueous or molten mixtures, over the entire composition range. A relationship was found for the coefficients of the equation σ = c(1) + c(2)T (where T (K) is temperature) for molten salts in terms of ion valency and radius, melting temperature, and salt molar volume. Hypothetical liquid surface tensions can thus be estimated for electrolytes for which there are no data, or which do not exist in molten form. Surface tensions of molten (single) salts, when extrapolated to normal temperatures, were found to be consistent with data for aqueous solutions. This allowed surface tensions of very concentrated, supersaturated, aqueous solutions to be estimated. The model has been applied to the following single electrolytes over the entire concentration range, using data for aqueous solutions over the temperature range 233-523 K, and extrapolated surface tensions of molten salts and pure liquid electrolytes: HCl, HNO(3), H(2)SO(4), NaCl, NaNO(3), Na(2)SO(4), NaHSO(4), Na(2)CO(3), NaHCO(3), NaOH, NH(4)Cl, NH(4)NO(3), (NH(4))(2)SO(4), NH(4)HCO(3), NH(4)OH, KCl, KNO(3), K(2)SO(4), K(2)CO(3), KHCO(3), KOH, CaCl(2), Ca(NO(3))(2), MgCl(2), Mg(NO(3))(2), and MgSO(4). The average absolute percentage error between calculated and experimental surface tensions is 0.80% (for 2389 data points). The model extrapolates smoothly to temperatures as low as 150 K. Also, the model successfully predicts surface tensions of ternary aqueous mixtures; the effect of salt-salt interactions in these calculations was explored.

Transient boiling in two-phase helium natural circulation loops

NASA Astrophysics Data System (ADS)

Furci, H.; Baudouy, B.; Four, A.; Meuris, C.

2014-01-01

Two-phase helium natural circulation loops are used for cooling large superconducting magnets, as CMS for LHC. During normal operation or in the case of incidents, transients are exerted on the cooling system. Here a cooling system of this type is studied experimentally. Sudden power changes are operated on a vertical-heated-section natural convection loop, simulating a fast increase of heat deposition on magnet cooling pipes. Mass flow rate, heated section wall temperature and pressure drop variations are measured as a function of time, to assess the time behavior concerning the boiling regime according to the values of power injected on the heated section. The boiling curves and critical heat flux (CHF) values have been obtained in steady state. Temperature evolution has been observed in order to explore the operating ranges where heat transfer is deteriorated. Premature film boiling has been observed during transients on the heated section in some power ranges, even at appreciably lower values than the CHF. A way of attenuating these undesired temperature excursions has been identified through the application of high enough initial heating power.

CdO-based nanostructures as novel CO2 gas sensors

NASA Astrophysics Data System (ADS)

Krishnakumar, T.; Jayaprakash, R.; Prakash, T.; Sathyaraj, D.; Donato, N.; Licoccia, S.; Latino, M.; Stassi, A.; Neri, G.

2011-08-01

Crystalline Cd(OH)2/CdCO3 nanowires, having lengths in the range from 0.3 up to several microns and 5-30 nm in diameter, were synthesized by a microwave-assisted wet chemical route and used as a precursor to obtain CdO nanostructures after a suitable thermal treatment in air. The morphology and microstructure of the as-synthesized and annealed materials have been investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and thermogravimetry-differential scanning calorimetry. The change in morphology and electrical properties with temperature has revealed a wire-to-rod transformation along with a decreases of electrical resistance. Annealed samples were printed on a ceramic substrate with interdigitated contacts to fabricate resistive solid state sensors. Gas sensing properties were explored by monitoring CO2 in synthetic air in the concentration range 0.2-5 v/v% (2000-50 000 ppm). The effect of annealing temperature, working temperature and CO2 concentration on sensing properties (sensitivity, response/recovery time and stability) were investigated. The results obtained demonstrate that CdO-based thick films have good potential as novel CO2 sensors for practical applications.

Structure and dynamics of GeoCyp: a thermophilic cyclophilin with a novel substrate binding mechanism that functions efficiently at low temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holliday, Michael; Camilloni, Carlo; Armstrong, Geoffrey S.

2015-05-26

Thermophilic proteins have found extensive use in research and industrial applications due to their high stability and functionality at elevated temperatures while simultaneously providing valuable insight into our understanding of protein folding, stability, dynamics, and function. Cyclophilins, a ubiquitously expressed family of peptidyl-prolyl isomerases with a range of biological functions and disease associations, have been utilized both for conferring stress tolerances and in exploring the link between conformational dynamics and enzymatic function. To date, however, no active thermophilic cyclophilin has been fully biophysically characterized. Here, we determine the structure of a thermophilic cyclophilin (GeoCyp) from Geobacillus kaustophilus, characterize its dynamicmore » motions over several timescales using an array of methodologies that include chemical shift-based methods and relaxation experiments over a range of temperatures, and measure catalytic activity over a range of temperatures in order to compare structure, dynamics, and function to a mesophilic counterpart, human Cyclophilin A (CypA). Unlike most thermophile/mesophile pairs, GeoCyp catalysis is not substantially impaired at low temperatures as compared to CypA, retaining ~70% of the activity of its mesophilic counterpart. Examination of substrate-bound ensembles reveals a mechanism by which the two cyclophilins may have adapted to their environments through altering dynamic loop motions and a critical residue that acts as a clamp to regulate substrate binding differentially in CypA and GeoCyp. Despite subtle differences in conformational movements, dynamics over fast (ps-ns) and slow (μs) timescales are largely conserved between the two proteins.« less

Thermal Design of the Instrument for the Transiting Exoplanet Survey Satellite

NASA Technical Reports Server (NTRS)

Allen, Gregory D.

2016-01-01

TESS observatory is a two year NASA Explorer mission which will use a set of four cameras to discover exoplanets. It will be placed in a high-earth orbit with a period of 13.7 days and will be unaffected by temperature disturbances caused by environmental heating from the Earth. The cameras use their stray-light baffles to passively cool the cameras and in turn the CCD's in order to maintain operational temperatures. The design has been well thought out and analyzed to maximize temperature stability. The analysis shows that the design keeps the cameras and their components within their temperature ranges which will help make it a successful mission. It will also meet its survival requirement of sustaining exposure to a five hour eclipse. Official validation and verification planning is underway and will be performed as the system is built up. It is slated for launch in 2017.

Hard permanent magnet development trends and their application to A.C. machines

NASA Technical Reports Server (NTRS)

Mildrum, H. F.

1981-01-01

The physical and magnetic properties of Mn-Al-C, Fe-Cr-Co, and RE-TM (rare earth-transition metal intermetallics) in polymer and soft metal bonded or sintered form are considered for ac circuit machine usage. The manufacturing processes for the magnetic materials are reviewed, and the mechanical and electrical properties of the magnetic materials are compared, with consideration given to the reference Alnico magnet. The Mn-Al-C magnets have the same magnetic properties and costs as Alnico units, operate well at low temperatures, but have poor high temperature performance. Fe-Cr-Co magnets also have comparable cost to Alnico magnets, and operate at high or low temperature, but are brittle, expensive, and contain Co. RE-Co magnets possess a high energy density, operate well in a wide temperature range, and are expensive. Recommendation for exploring the rare-earth alternatives are offered.

Optical phonon behavior of columbite MgNb2O6 single crystals

NASA Astrophysics Data System (ADS)

Xu, Dapeng; Liu, Wenqiang; Zhou, Qiang; Cui, Tian; Yuan, Hongming; Wang, Wenquan; Liu, Ying; Shi, Zhan; Li, Liang

2014-08-01

To explore potential applications, MgNb2O6 single crystal grown previously by optical floating zone method was used as a prototype for optical phonon behavior investigation. Polarized Raman spectra obtained in adequate parallel and crossed polarization were presented. All the obtained Raman modes were identified for the MgNb2O6, in good agreement with previous theory analysis. The selection rules of Raman for the columbite group were validated. Additionally, in-site temperature-dependent Raman spectra of MgNb2O6 were also investigated in the range from 83 to 803 K. The strong four Ag phonon modes all exhibits red shift with the temperature increasing. But thermal expansion of spectra is sectional linear with inflection points at about 373 K. And the absolute value of dω/dT at high temperature is higher than the one at lower temperature.

Local vertical motions and kinetic temperature from AE-C as evidence for aurora-induced gravity waves

NASA Technical Reports Server (NTRS)

Spencer, N. W.; Theis, R. F.; Wharton, L. E.; Carignan, G. R.

1976-01-01

In situ measurements of local vertical neutral particle motions have been made using the Neutral Atmosphere Temperature Instrument (NATE) on Atmosphere Explorer-C from observations of the direction of flow of neutral particles into the antechamber of the sensor (mass spectrometer). Values ranging from a few to more than 80 meters per second have been observed. The data show vertical motions greater than a few meters per second to be present most of the time, the magnitude being a function of many factors including magnetic activity, location, and magnetic storm history. In a specific case, it is concluded that the observed vertical motions and kinetic temperature are evidence of a travelling disturbance originating as a gravity wave in the auroral zone.

Study of the longitudinal space charge compensation and longitudinal instability of the ferrite inductive inserts in the Los Alamos Proton Storage Ring

NASA Astrophysics Data System (ADS)

Beltran, Chris

Future high intensity synchrotrons will have a large space charge effect. It has been demonstrated in the Proton Storage Ring (PSR) at the Los Alamos National Laboratory (LANL) that ferrite inductive inserts can be used to compensate for the longitudinal space charge effect. However, simply installing ferrite inductors in the PSR led to longitudinal instabilities that were not tolerable. It was proposed that heating the ferrite would change the material properties in such a way as to reduce the instability. This proposal was tested in the PSR, and found to be true. This dissertation investigates and describes the complex permeability of the ferrite at room temperature and at an elevated temperature. The derived complex permeability is then used to obtain an impedance at the two temperatures. The impedance is used to determine the amount of space charge compensation supplied by the inductors and predict the growth time and frequency range of the longitudinal instability. The impedance is verified by comparing the experimental growth time and frequency range of the longitudinal instability to theoretical and computer simulated growth times and frequency ranges of the longitudinal instability. Lastly, an approach to mitigating the longitudinal instability that does not involve heating the ferrite is explored.

Exploration Method Development for hydrothermal plume hunting by XCTD

NASA Astrophysics Data System (ADS)

Kitagawa, Y.; Ikeda, M.; Kadoshima, K.; Koizumi, Y.; Nakano, J.; Asakawa, E.; Sumi, T.

2017-12-01

J-MARES (Research and Development Partnership for Next Generation Technology of Marine Resources Survey, JAPAN) has been designing a low-cost and high-efficiency exploration system for seafloor hydrothermal massive sulfide deposits in "Cross-ministerial Strategic Innovation Promotion Program (SIP)" granted by the Cabinet Office, Government of Japan since 2014. We proposed hydrothermal plume hunting by XCTD (eXpendables Conductivity, Temperature and Depth). We applied this method to an area of interest more than 100km x 100km over Okinawa Trough, including some known seafloor massive sulfide deposits. Generally, hydrothermal plume exploration has been by ship mounted with MBES (Multi Beam Echo Sounder) or AUV with sound anomaly observation. However, these methods have to charter the sophisticated ship costly. On the other hand, throw-in type water quality meters (eg. XCTD and XBT) can be low-cost and easily operable. Moreover, that can make a quick look at seawater temperature and conductivity even in rough waters.Firstly, we confirmed XCTD probes position on the seafloor by ROV mounted deep-sea high vision camera. As a result of the test, probes swept downstream about 40 m in horizontal distance from throwing positions with about 1,600m in water depth. Following the previous test results, we had performed to the next test that confirmed detection range of hydrothermal plume at the chimney of North Mound in Izena Cauldron, so we had caught anomaly of seawater temperature and conductivity successfully which could be possibly derived from hydrothermal activities. Although averaged seawater temperature at a depth of 1500 m or more was about 3.95 degrees C, near the chimney was about 4.93 degrees C. The temperature anomalies originated from the hydrothermal plumes could be distributed at most 30m in horizontal distance and became smaller away from the chimney. Moreover, temperature anomaly mass of sea water tended to move upward in depth with distance away from the chimney.

[Spatial-temporal distribution of bigeye tuna Thunnus obesus in the tropical Atlantic Ocean based on Argo data].

PubMed

Yang, Sheng-long; Jin, Shao-fei; Hua, Cheng-jun; Dai, Yang

2015-02-01

In order to analyze the correlation between spatial-temporal distribution of the bigeye tuna ( Thunnus obesus) and subsurface factors, the study explored the isothermal distribution of subsurface temperatures in the bigeye tuna fishing grounds in the tropical Atlantic Ocean, and built up the spatial overlay chart of the isothermal lines of 9, 12, 13 and 15 °C and monthly CPUE (catch per unit effort) from bigeye tuna long-lines. The results showed that the bigeye tuna mainly distributed in the water layer (150-450 m) below the lower boundary depth of thermocline. At the isothermal line of 12 °C, the bigeye tuna mainly lived in the water layer of 190-260 m, while few individuals were found at water depth more than 400 m. As to the 13 °C isothermal line, high CPUE often appeared at water depth less than 250 m, mainly between 150-230 m, while no CPUE appeared at water depth more than 300 m. The optimum range of subsurface factors calculated by frequency analysis and empirical cumulative distribution function (ECDF) exhibited that the optimum depth range of 12 °C isothermal depth was 190-260 m and the 13 °C isothermal depth was 160-240 m, while the optimum depth difference range of 12 °C isothermal depth was -10 to 100 m and the 13 °C isothermal depth was -40 to 60 m. The study explored the optimum range of subsurface factors (water temperature and depth) that drive horizontal and vertical distribution of bigeye tuna. The preliminary result would help to discover the central fishing ground, instruct fishing depth, and provide theoretical and practical references for the longline production and resource management of bigeye tuna in the Atlantic Ocean.

Exploring the influence of texture and composition on the thermal transport properties of mudstones

NASA Astrophysics Data System (ADS)

Kenderes, S. M.; Hofmeister, A. M.; Merriman, J. D.; Whittington, A. G.

2017-12-01

The thermal history of sedimentary basins depends strongly on the thermal transport properties of the rocks within the basin. Mudstones are compositionally diverse, varying both chemically and with modal mineralogy, which are known to affect the thermal transport properties of earth materials. To explore the influence of composition and texture on the thermal transport properties of mudstones, we have measured the thermal diffusivity (D) and isobaric heat capacity (CP) of 12 mudstones using the contact-free laser flash analysis (LFA) and differential scanning calorimetry (DSC). At 20°C, D values of the shales range from 0.318 to 1.214 mm2·s-1 and CP values range from 799 to 918 J·kg-1·°C-1 and at 300°C, D values range from 0.227 to 0.582 mm2·s-1 and CP values range from 1095 to 1344 J·kg-1·°C-1. The mudstones with the highest D values, and lowest CP values are green micaceous or calcareous siltstones respectively, whereas the mudstones with the lowest D values, and highest CP values are black, claystones with 9% organic carbon. This suggests that organic carbon content and, to a lesser extent, the grainsize influence the thermal transport properties of these rocks. The lower D values and higher CP values cause organic rich claystones to absorb and transmit heat differently than other types of mudstones. This is especially true at lower temperatures, where the difference in D values is much greater than at higher temperatures. Additionally, when compared to other sedimentary rocks, shales generally have lower D values and higher CP values. These results also highlight the necessity of using rock type specific values in heat transport numerical models.

Extraordinary range expansion in a common bat: the potential roles of climate change and urbanisation.

PubMed

Ancillotto, L; Santini, L; Ranc, N; Maiorano, L; Russo, D

2016-04-01

Urbanisation and climate change are two global change processes that affect animal distributions, posing critical threats to biodiversity. Due to its versatile ecology and synurbic habits, Kuhl's pipistrelle (Pipistrellus kuhlii) offers a unique opportunity to explore the relative effects of climate change and urbanisation on species distributions. In a climate change scenario, this typically Mediterranean species is expected to expand its range in response to increasing temperatures. We collected 25,132 high-resolution occurrence records from P. kuhlii European range between 1980 and 2013 and modelled the species' distribution with a multi-temporal approach, using three bioclimatic variables and one proxy of urbanisation. Temperature in the coldest quarter of the year was the most important factor predicting the presence of P. kuhlii and showed an increasing trend in the study period; mean annual precipitation and precipitation seasonality were also relevant, but to a lower extent. Although urbanisation increased in recently colonised areas, it had little effect on the species' presence predictability. P. kuhlii expanded its geographical range by about 394 % in the last four decades, a process that can be interpreted as a response to climate change.

Extraordinary range expansion in a common bat: the potential roles of climate change and urbanisation

NASA Astrophysics Data System (ADS)

Ancillotto, L.; Santini, L.; Ranc, N.; Maiorano, L.; Russo, D.

2016-04-01

Urbanisation and climate change are two global change processes that affect animal distributions, posing critical threats to biodiversity. Due to its versatile ecology and synurbic habits, Kuhl's pipistrelle ( Pipistrellus kuhlii) offers a unique opportunity to explore the relative effects of climate change and urbanisation on species distributions. In a climate change scenario, this typically Mediterranean species is expected to expand its range in response to increasing temperatures. We collected 25,132 high-resolution occurrence records from P. kuhlii European range between 1980 and 2013 and modelled the species' distribution with a multi-temporal approach, using three bioclimatic variables and one proxy of urbanisation. Temperature in the coldest quarter of the year was the most important factor predicting the presence of P. kuhlii and showed an increasing trend in the study period; mean annual precipitation and precipitation seasonality were also relevant, but to a lower extent. Although urbanisation increased in recently colonised areas, it had little effect on the species' presence predictability. P. kuhlii expanded its geographical range by about 394 % in the last four decades, a process that can be interpreted as a response to climate change.

Scenario and modelling uncertainty in global mean temperature change derived from emission-driven global climate models

NASA Astrophysics Data System (ADS)

Booth, B. B. B.; Bernie, D.; McNeall, D.; Hawkins, E.; Caesar, J.; Boulton, C.; Friedlingstein, P.; Sexton, D. M. H.

2013-04-01

We compare future changes in global mean temperature in response to different future scenarios which, for the first time, arise from emission-driven rather than concentration-driven perturbed parameter ensemble of a global climate model (GCM). These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle, ocean physics and aerosol sulphur cycle processes. We find broader ranges of projected temperature responses arising when considering emission rather than concentration-driven simulations (with 10-90th percentile ranges of 1.7 K for the aggressive mitigation scenario, up to 3.9 K for the high-end, business as usual scenario). A small minority of simulations resulting from combinations of strong atmospheric feedbacks and carbon cycle responses show temperature increases in excess of 9 K (RCP8.5) and even under aggressive mitigation (RCP2.6) temperatures in excess of 4 K. While the simulations point to much larger temperature ranges for emission-driven experiments, they do not change existing expectations (based on previous concentration-driven experiments) on the timescales over which different sources of uncertainty are important. The new simulations sample a range of future atmospheric concentrations for each emission scenario. Both in the case of SRES A1B and the Representative Concentration Pathways (RCPs), the concentration scenarios used to drive GCM ensembles, lies towards the lower end of our simulated distribution. This design decision (a legacy of previous assessments) is likely to lead concentration-driven experiments to under-sample strong feedback responses in future projections. Our ensemble of emission-driven simulations span the global temperature response of the CMIP5 emission-driven simulations, except at the low end. Combinations of low climate sensitivity and low carbon cycle feedbacks lead to a number of CMIP5 responses to lie below our ensemble range. The ensemble simulates a number of high-end responses which lie above the CMIP5 carbon cycle range. These high-end simulations can be linked to sampling a number of stronger carbon cycle feedbacks and to sampling climate sensitivities above 4.5 K. This latter aspect highlights the priority in identifying real-world climate-sensitivity constraints which, if achieved, would lead to reductions on the upper bound of projected global mean temperature change. The ensembles of simulations presented here provides a framework to explore relationships between present-day observables and future changes, while the large spread of future-projected changes highlights the ongoing need for such work.

Boron nitride nanotubes for spintronics.

PubMed

Dhungana, Kamal B; Pati, Ranjit

2014-09-22

With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics.

Boron Nitride Nanotubes for Spintronics

PubMed Central

Dhungana, Kamal B.; Pati, Ranjit

2014-01-01

With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics. PMID:25248070

Mars Exploration Rover Entry, Descent, and Landing: A Thermal Perspective

NASA Technical Reports Server (NTRS)

Tsuyuki, Glenn T.; Sunada, Eric T.; Novak, Keith S.; Kinsella, Gary M.; Phillip, Charles J.

2005-01-01

Perhaps the most challenging mission phase for the Mars Exploration Rovers was the Entry, Descent, and Landing (EDL). During this phase, the entry vehicle attached to its cruise stage was transformed into a stowed tetrahedral Lander that was surrounded by inflated airbags through a series of complex events. There was only one opportunity to successfully execute an automated command sequence without any possible ground intervention. The success of EDL was reliant upon the system thermal design: 1) to thermally condition EDL hardware from cruise storage temperatures to operating temperature ranges; 2) to maintain the Rover electronics within operating temperature ranges without the benefit of the cruise single phase cooling loop, which had been evacuated in preparation for EDL; and 3) to maintain the cruise stage propulsion components for the critical turn to entry attitude. Since the EDL architecture was inherited from Mars Pathfinder (MPF), the initial EDL thermal design would be inherited from MPF. However, hardware and implementation differences from MPF ultimately changed the MPF inheritance approach for the EDL thermal design. With the lack of full inheritance, the verification and validation of the EDL thermal design took on increased significance. This paper will summarize the verification and validation approach for the EDL thermal design along with applicable system level thermal testing results as well as appropriate thermal analyses. In addition, the lessons learned during the system-level testing will be discussed. Finally, the in-flight EDL experiences of both MER-A and -B missions (Spirit and Opportunity, respectively) will be presented, demonstrated how lessons learned from Spirit were applied to Opportunity.

The coexistence temperature of hydrogen clathrates: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Luis, D. P.; Romero-Ramirez, I. E.; González-Calderón, A.; López-Lemus, J.

2018-03-01

Extensive molecular dynamics simulations in the equilibrium isobaric-isothermal (NPT) ensemble were developed to determine the coexistence temperatures of the water hydrogen mixture using the direct coexistence method. The water molecules were modeled using the four-site TIP4P/Ice analytical potential, and the hydrogen molecules were described using a three-site potential. The simulations were performed at different pressures (p = 900, 1500, 3000, and 4000 bars). At each pressure, a series of simulations were developed at different temperatures (from 230 to 270 K). Our results followed a line parallel to the experimental coexistence temperatures and underestimated these temperatures by approximately 25 K in the investigated range. The final configurations could or could not contain a fluid phase depending on the pressure, in accordance with the phase diagram. In addition, we explored the dynamics of the H2 molecules through clathrate hydrate cages and observed different behaviors of the H2 molecules in the small cages and the large cages of the sII structure.

Climate matching as a tool for predicting potential North American spread of Brown Treesnakes

USGS Publications Warehouse

Rodda, Gordon H.; Reed, Robert N.; Jarnevich, Catherine S.; Witmer, G.W.; Pitt, W. C.; Fagerstone, K.A.

2007-01-01

Climate matching identifies extralimital destinations that could be colonized by a potential invasive species on the basis of similarity to climates found in the species’ native range. Climate is a proxy for the factors that determine whether a population will reproduce enough to offset mortality. Previous climate matching models (e.g., Genetic Algorithm for Rule-set Prediction [GARP]) for brown treesnakes (Boiga irregularis) were unsatisfactory, perhaps because the models failed to allow different combinations of climate attributes to influence a species’ range limits in different parts of the range. Therefore, we explored the climate space described by bivariate parameters of native range temperature and rainfall, allowing up to two months of aestivation in the warmer portions of the range, or four months of hibernation in temperate climes. We found colonization area to be minimally sensitive to assumptions regarding hibernation temperature thresholds. Although brown treesnakes appear to be limited by dry weather in the interior of Australia, aridity rarely limits potential distribution in most of the world. Potential colonization area in North America is limited primarily by cold. Climatically suitable portions of the United States (US) mainland include the Central Valley of California, mesic patches in the Southwest, and the southeastern coastal plain from Texas to Virginia.

Intrinsic Two-Dimensional Ferroelectricity with Dipole Locking

NASA Astrophysics Data System (ADS)

Xiao, Jun; Zhu, Hanyu; Wang, Ying; Feng, Wei; Hu, Yunxia; Dasgupta, Arvind; Han, Yimo; Wang, Yuan; Muller, David A.; Martin, Lane W.; Hu, PingAn; Zhang, Xiang

2018-06-01

Out-of-plane ferroelectricity with a high transition temperature in ultrathin films is important for the exploration of new domain physics and scaling down of memory devices. However, depolarizing electrostatic fields and interfacial chemical bonds can destroy this long-range polar order at two-dimensional (2D) limit. Here we report the experimental discovery of the locking between out-of-plane dipoles and in-plane lattice asymmetry in atomically thin In2Se3 crystals, a new stabilization mechanism leading to our observation of intrinsic 2D out-of-plane ferroelectricity. Through second harmonic generation spectroscopy and piezoresponse force microscopy, we found switching of out-of-plane electric polarization requires a flip of nonlinear optical polarization that corresponds to the inversion of in-plane lattice orientation. The polar order shows a very high transition temperature (˜700 K ) without the assistance of extrinsic screening. This finding of intrinsic 2D ferroelectricity resulting from dipole locking opens up possibilities to explore 2D multiferroic physics and develop ultrahigh density memory devices.

The geothermal gradient map of Central Tunisia: Comparison with structural, gravimetric and petroleum data

NASA Astrophysics Data System (ADS)

Dhia, Hamed Ben

1987-10-01

Five hundred and fifty temperature values, initially measured as either bottom-hole temperatures (BHT) or drill-stem tests (DST), from 98 selected petroleum exploration wells form the basis of a geothermal gradient map of central Tunisia. A "global-statistical" method was employed to correct the BHT measurements, using the DST as references. The geothermal gradient ranges from 23° to 49°C/km. Comparison of the geothermal gradient with structural, gravimetric and petroleum data indicates that: (1) the general trend of the geothermal gradient curves reflects the main structural directions of the region, (2) zones of low and high geothermal gradient are correlated with zones of negative and positive Bouguer anomalies and (3) the five most important oil fields of central Tunisia are located near the geothermal gradient curve of 40° C/km. Such associations could have practical importance in petroleum exploration, but their significance must first be established through further investigation and additional data.

Mimicking Mars: A vacuum simulation chamber for testing environmental instrumentation for Mars exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobrado, J. M., E-mail: sobradovj@inta.es; Martín-Soler, J.; Martín-Gago, J. A.

We have built a Mars environmental simulation chamber, designed to test new electromechanical devices and instruments that could be used in space missions. We have developed this environmental system aiming at validating the meteorological station Rover Environment Monitoring Station of NASA's Mars Science Laboratory mission currently installed on Curiosity rover. The vacuum chamber has been built following a modular configuration and operates at pressures ranging from 1000 to 10{sup −6} mbars, and it is possible to control the gas composition (the atmosphere) within this pressure range. The device (or sample) under study can be irradiated by an ultraviolet source andmore » its temperature can be controlled in the range from 108 to 423 K. As an important improvement with respect to other simulation chambers, the atmospheric gas into the experimental chamber is cooled at the walls by the use of liquid-nitrogen heat exchangers. This chamber incorporates a dust generation mechanism designed to study Martian-dust deposition while modifying the conditions of temperature, and UV irradiated.« less

Molecular hydrogen interacts more strongly when rotationally excited at low temperatures leading to faster reactions.

PubMed

Shagam, Yuval; Klein, Ayelet; Skomorowski, Wojciech; Yun, Renjie; Averbukh, Vitali; Koch, Christiane P; Narevicius, Edvardas

2015-11-01

The role of internal molecular degrees of freedom, such as rotation, has scarcely been explored experimentally in low-energy collisions despite their significance to cold and ultracold chemistry. Particularly important to astrochemistry is the case of the most abundant molecule in interstellar space, hydrogen, for which two spin isomers have been detected, one of which exists in its rotational ground state whereas the other is rotationally excited. Here we demonstrate that quantization of molecular rotation plays a key role in cold reaction dynamics, where rotationally excited ortho-hydrogen reacts faster due to a stronger long-range attraction. We observe rotational state-dependent non-Arrhenius universal scaling laws in chemi-ionization reactions of para-H2 and ortho-H2 by He(2(3)P2), spanning three orders of magnitude in temperature. Different scaling laws serve as a sensitive gauge that enables us to directly determine the exact nature of the long-range intermolecular interactions. Our results show that the quantum state of the molecular rotor determines whether or not anisotropic long-range interactions dominate cold collisions.

Trajectory and Aeroheating Environment Development and Sensitivity Analysis for Capsule-shaped Vehicles

NASA Technical Reports Server (NTRS)

Robinson, Jeffrey S.; Wurster, Kathryn E.

2006-01-01

Recently, NASA's Exploration Systems Research and Technology Project funded several tasks that endeavored to develop and evaluate various thermal protection systems and high temperature material concepts for potential use on the crew exploration vehicle. In support of these tasks, NASA Langley's Vehicle Analysis Branch generated trajectory information and associated aeroheating environments for more than 60 unique entry cases. Using the Apollo Command Module as the baseline entry system because of its relevance to the favored crew exploration vehicle design, trajectories for a range of lunar and Mars return, direct and aerocapture Earth-entry scenarios were developed. For direct entry, a matrix of cases was created that reflects reasonably expected minimum and maximum values of vehicle ballistic coefficient, inertial velocity at entry interface, and inertial flight path angle at entry interface. For aerocapture, trajectories were generated for a range of values of initial velocity and ballistic coefficient that, when combined with proper initial flight path angles, resulted in achieving a low Earth orbit either by employing a full lift vector up or full lift vector down attitude. For each trajectory generated, aeroheating environments were generated which were intended to bound the thermal protection system requirements for likely crew exploration vehicle concepts. The trades examined clearly pointed to a range of missions / concepts that will require ablative systems as well as a range for which reusable systems may be feasible. In addition, the results clearly indicated those entry conditions and modes suitable for manned flight, considering vehicle deceleration levels experienced during entry. This paper presents an overview of the analysis performed, including the assumptions, methods, and general approach used, as well as a summary of the trajectory and aerothermal environment information that was generated.

The implications of rebasing global mean temperature timeseries for GCM based climate projections

NASA Astrophysics Data System (ADS)

Stainforth, David; Chapman, Sandra; Watkins, Nicholas

2017-04-01

Global climate and earth system models are assessed by comparison with observations through a number of metrics. The InterGovernmental Panel on Climate Change (IPCC) highlights in particular their ability to reproduce "general features of the global and annual mean surface temperature changes over the historical period" [1,2] and to simulate "a trend in global-mean surface temperature from 1951 to 2012 that agrees with the observed trend" [3]. This focus on annual mean global mean temperature (hereafter GMT) change is presented as an important element in demonstrating the relevance of these models for climate projections. Any new model or new model version whose historic simulations fail to reproduce the "general features " and 20th century trends is likely therefore to undergo further tuning. Thus this focus could have implications for model development. Here we consider a formal interpretation of "general features" and discuss the implications of this approach to model assessment and intercomparison, for the interpretation of GCM projections. Following the IPCC, we interpret a major element of "general features" as being the slow timescale response to external forcings. (Shorter timescale behaviour such as the response to volcanic eruptions are also elements of "general features" but are not considered here.) Also following the IPCC, we consider only GMT anomalies i.e. changes with respect to some period. Since the models have absolute temperatures which range over about 3K (roughly observed GMT +/- 1.5K) this means their timeseries (and the observations) are rebased. We present timeseries of the slow timescale response of the CMIP5 models rebased to late-20th century temperatures and to mid-19th century temperatures. We provide a mathematical interpretation of this approach to model assessment and discuss two consequences. First is a separation of scales which limits the degree to which sub-global behaviour can feedback on the global response. Second, is an implication of linearity in the GMT response (to the extent that the slow-timescale response of the historic simulations is consistent with observations, and given their uncertainties). For each individual model these consequences only apply over the range of absolute temperatures simulated by the model in historic simulations. Taken together, however, they imply consequences over a much wider range of GMTs. The analysis suggests that this aspect of model evaluation risks providing a model development pressure which acts against a wide exploration of physically plausible responses; in particular against an exploration of potentially globally significant nonlinear responses and feedbacks. [1] IPCC, Fifth Assessment Report, Working Group 1, Technical Summary: Stocker et al. 2013. [2] IPCC, Fifth Assessment Report, Working Group 1, Chapter 9 - "Evaluation of Climate Models": Flato et al. 2013. [3] IPCC, Fifth Assessment Report, Working Group 1, Summary for Policy Makers: IPCC, 2013.

A Geodynamic model for melt generation and evolution of the Mid-Continental Rift

NASA Astrophysics Data System (ADS)

Gunawardana, P. M.; Moucha, R.; Rooney, T. O.; Stein, S.; Stein, C. A.; Hansen, M.

2017-12-01

The Mid-Continent Rift System (MCRS) is a 3000-km long failed rift system which formed within the Precambrian continent of Laurentia and nearly split North America apart about 1.1 billion years ago. The MCRS can also be classified as a Large Igneous Province (LIP) made up of two distinct magmatic phases (Stein et al., 2015). The first large scale magmatism is characterized by a large volume of flood basalt that filled a fault controlled basin. The second post-rift phase consists of volcanics and sediment that were deposited in a thermally subsiding basin after faulting ended. This flood basalt filled rift geometry is a special characteristic of the MCRS which is not observed in other presently active or ancient rifts. Hence the MCRS's unusual nature likely reflects the combined effects of rifting and a mantle plume. We investigate this hypothesis with a geodynamic model by fully exploring the parameter space for a range of mantle potential and plume excess temperatures as well as different extension scenarios and lithospheric/plume structure. We quantify the rate and amount of melt generated and compare these with inferred volume and history of magmatic activity. Our model suggests that for an initially thin 100 km continental lithosphere and high mantle potential temperatures above 1453 oC, a plume is not required to generate the inferred volume of flood basalt as long as the lithosphere is thinned rapidly (> 3cm/yr). We note that in this scenario, majority of the melt generation continues for a few million years after the rifting ends. However, for present-day mantle potential temperatures ( 1343 oC) a mantle plume is required with an excess of temperature > 100 oC to generate the required volume of flood basalt. Furthermore, if the initial continental lithosphere thickness is greater than 100 km, the required plume excess temperature to generate enough melt, must be > 200 oC for the range of mantle potential temperatures we explored. References Stein, C.A., Kley, J., Stein, S., Hindle, D., and Keller, G.R., 2015, North America's Midcontinent Rift: When rift met LIP: Geosphere, v. 11, no. 5, p. 1607-1616, doi:10.1130/GES01183.1.

Unveiling the relationships among the viscosity equations of glass liquids and colloidal suspensions for obtaining universal equations with the generic free volume concept.

PubMed

Hao, Tian

2015-09-14

The underlying relationships among viscosity equations of glass liquids and colloidal suspensions are explored with the aid of free volume concept. Viscosity equations of glass liquids available in literature are focused and found to have a same physical basis but different mathematical expressions for the free volume. The glass transitions induced by temperatures in glass liquids and the percolation transition induced by particle volume fractions in colloidal suspensions essentially are a second order phase transition: both those two transitions could induce the free volume changes, which in turn determines how the viscosities are going to change with temperatures and/or particle volume fractions. Unified correlations of the free volume to both temperatures and particle volume fractions are thus proposed. The resulted viscosity equations are reducible to many popular viscosity equations currently widely used in literature; those equations should be able to cover many different types of materials over a wide temperature range. For demonstration purpose, one of the simplified versions of those newly developed equations is compared with popular viscosity equations and the experimental data: it can well fit the experimental data over a wide temperature range. The current work reveals common physical grounds among various viscosity equations, deepening our understanding on viscosity and unifying the free volume theory across many different systems.

Phosphor Thermometry at ORNL

NASA Astrophysics Data System (ADS)

Allison, S. W.; Gates, M. R.; Beshears, D. L.; Gillies, G. T.

2003-09-01

Phosphor materials are, by design, capable of efficiently converting excitation energy into fluorescence. The temperature-dependent characteristics of this fluorescence provide the basis for noncontact thermometry. In the past decade this approach has been applied to turbine engine diagnostics, liquid temperature measurements for heat pump research, combustion engine intake valve and piston measurements, galvanneal steel processing, transient thermometry of particle beam targets, and microcantilevers used in MEMS devices. The temperatures involved range from ambient to in excess of 1200 °C. Some of these applications have involved fiber optics for light delivery and/or fluorescence signal collection. In addition to fielding these applications, there has been considerable work in the laboratory aimed at exploring further improvements and adding to the database of temperature-characterized phosphors. The activities involve investigation of short-decay time phosphors for use on imaging surfaces moving at high speeds, measuring and modeling pressure as well as temperature dependence, developing phosphor adhesion methods, developing phase-based data acquisition approaches. A significant advance is that light-emitting diodes can now be used to provide adequate stimulation of fluorescence in some applications. Recently nanophosphors have become available. The spectral properties and, by implication, thermal dependence of these properties change with particle size. This has ramifications that need to be explored. The ways in which such materials can be exploited for micro- and nano-technology are just now being addressed. These applications and developments mentioned above will be surveyed and discussed as well as envisioned future improvements and new uses for this thermometry technique.

Note: Enhancement of the extreme ultraviolet emission from a potassium plasma by dual laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higashiguchi, Takeshi, E-mail: higashi@cc.utsunomiya-u.ac.jp; Yamaguchi, Mami; Otsuka, Takamitsu

2014-09-15

Emission spectra from multiply charged potassium ions ranging from K{sup 3+} to K{sup 5+} have been obtained in the extreme ultraviolet (EUV) spectral region. A strong emission feature peaking around 38 nm, corresponding to a photon energy of 32.6 eV, is the dominant spectral feature at time-averaged electron temperatures in the range of 8−12 eV. The variation of this emission with laser intensity and the effects of pre-pulses on the relative conversion efficiency (CE) have been explored experimentally and indicate that an enhancement of about 30% in EUV CE is readily attainable.

Using measured octanol-air partition coefficients to explain environmental partitioning of organochlorine pesticides.

PubMed

Shoeib, Mahiba; Harner, Tom

2002-05-01

Octanol-air partition coefficients (Koa) were measured directly for 19 organochlorine (OC) pesticides over the temperature range of 5 to 35 degrees C. Values of log Koa at 25 degrees C ranged over three orders of magnitude, from 7.4 for hexachlorobenzene to 10.1 for 1,1-dichloro-2,2-bis(p-chlorophenyl) ethane. Measured values were compared to values calculated as KowRT/H (where R is the ideal gas constant [8.314 J mol(-1) K(-1)], T is absolute temperature, and H is Henry's law constant) were, in general, larger. Discrepancies of up to three orders of magnitude were observed, highlighting the need for direct measurements of Koa. Plots of Koa versus inverse absolute temperature exhibited a log-linear correlation. Enthalpies of phase transition between octanol and air (deltaHoa) were determined from the temperature slopes and were in the range of 56 to 105 kJ mol(-1) K(-1). Activity coefficients in octanol (gamma(o)) were determined from Koa and reported supercooled liquid vapor pressures (pL(o)), and these were in the range of 0.3 to 12, indicating near-ideal solution behavior. Differences in Koa values for structural isomers of hexachlorocyclohexane were also explored. A Koa-based model was described for predicting the partitioning of OC pesticides to aerosols and used to calculate particulate fractions at 25 and -10 degrees C. The model also agreed well with experimental results for several OC pesticides that were equilibrated with urban aerosols in the laboratory. A log-log regression of the particle-gas partition coefficient versus Koa had a slope near unity, indicating that octanol is a good surrogate for the aerosol organic matter.

Results from EDGES High-band. I. Constraints on Phenomenological Models for the Global 21 cm Signal

NASA Astrophysics Data System (ADS)

Monsalve, Raul A.; Rogers, Alan E. E.; Bowman, Judd D.; Mozdzen, Thomas J.

2017-09-01

We report constraints on the global 21 cm signal due to neutral hydrogen at redshifts 14.8≥slant z≥slant 6.5. We derive our constraints from low-foreground observations of the average sky brightness spectrum conducted with the EDGES High-band instrument between 2015 September 7 and October 26. Observations were calibrated by accounting for the effects of antenna beam chromaticity, antenna and ground losses, signal reflections, and receiver parameters. We evaluate the consistency between the spectrum and phenomenological models for the global 21 cm signal. For tanh-based representations of the ionization history during the epoch of reionization, we rule out, at ≥slant 2σ significance, models with duration of up to {{Δ }}z=1 at z≈ 8.5 and higher than {{Δ }}z=0.4 across most of the observed redshift range under the usual assumption that the 21 cm spin temperature is much larger than the temperature of the cosmic microwave background during reionization. We also investigate a “cold” intergalactic medium (IGM) scenario that assumes perfect Lyα coupling of the 21 cm spin temperature to the temperature of the IGM, but that the latter is not heated by early stars or stellar remants. Under this assumption, we reject tanh-based reionization models of duration {{Δ }}z≲ 2 over most of the observed redshift range. Finally, we explore and reject a broad range of Gaussian models for the 21 cm absorption feature expected in the First Light era. As an example, we reject 100 mK Gaussians with duration (full width at half maximum) {{Δ }}z≤slant 4 over the range 14.2≥slant z≥slant 6.5 at ≥slant 2σ significance.

Coarsening of AA6013-T6 Precipitates During Sheet Warm Forming Applications

NASA Astrophysics Data System (ADS)

Di Ciano, M.; DiCecco, S.; Esmaeili, S.; Wells, M. A.; Worswick, M. J.

2018-03-01

The use of warm forming for AA6xxx-T6 sheet is of interest to improve its formability; however, the effect warm forming may have on the coarsening of precipitates and the mechanical strength of these sheets has not been well studied. In this research, the coarsening behavior of AA6013-T6 precipitates has been explored, in the temperature range of 200-300 °C, and time of 30 s up to 50 h. Additionally, the effect of warm deformation on coarsening behavior was explored using: (1) simulated warm forming tests in a Gleeble thermo-mechanical simulator and (2) bi-axial warm deformation tests. Using a strong obstacle model to describe the yield strength (YS) evolution of the AA6013-T6 material, and a Lifshitz, Slyozov, and Wagner (LSW) particle coarsening law to describe the change in precipitate size with time, the coarsening kinetics were modeled for this alloy. The coarsening kinetics in the range of 220-300 °C followed a trend similar to that previously found for AA6111 for the 180-220 °C range. There was strong evidence that coarsening kinetics were not altered due to warm deformation above 220 °C. For warm forming between 200 and 220 °C, the YS of the AA6013-T6 material increased slightly, which could be attributed to strain hardening during warm deformation. Finally, a non-isothermal coarsening model was used to assess the potential reduction in the YS of AA6013-T6 for practical processing conditions related to auto-body manufacturing. The model calculations showed that 90% of the original AA6013-T6 YS could be maintained, for warm forming temperatures up to 280 °C, if the heating schedule used to get the part to the warm forming temperature was limited to 1 min.

Ab initio thermodynamic approach to identify mixed solid sorbents for CO 2 capture technology

DOE PAGES

Duan, Yuhua

2015-10-15

Because the current technologies for capturing CO 2 are still too energy intensive, new materials must be developed that can capture CO 2 reversibly with acceptable energy costs. At a given CO 2 pressure, the turnover temperature (T t) of the reaction of an individual solid that can capture CO 2 is fixed. Such T t may be outside the operating temperature range (ΔT o) for a practical capture technology. To adjust T t to fit the practical ΔT o, in this study, three scenarios of mixing schemes are explored by combining thermodynamic database mining with first principles density functionalmore » theory and phonon lattice dynamics calculations. Our calculated results demonstrate that by mixing different types of solids, it’s possible to shift T t to the range of practical operating temperature conditions. According to the requirements imposed by the pre- and post- combustion technologies and based on our calculated thermodynamic properties for the CO 2 capture reactions by the mixed solids of interest, we were able to identify the mixing ratios of two or more solids to form new sorbent materials for which lower capture energy costs are expected at the desired pressure and temperature conditions.« less

Diffusion bonding of IN 718 to VM 350 grade maraging steel

NASA Technical Reports Server (NTRS)

Crosby, S. R.; Biederman, R. R.; Reynolds, C. C.

1972-01-01

Diffusion bonding studies have been conducted on IN 718, VM 350 and the dissimilar alloy couple, IN 718 to maraging steel. The experimental processing parameters critical to obtaining consistently good diffusion bonds between IN 718 and VM 350 were determined. Interrelationships between temperature, pressure and surface preparation were explored for short bending intervals under vacuum conditions. Successful joining was achieved for a range of bonding cycle temperatures, pressures and surface preparations. The strength of the weaker parent material was used as a criterion for a successful tensile test of the heat treated bond. Studies of VM-350/VM-350 couples in the as-bonded condition showed a greater yielding and failure outside the bond region.

Temperature-driven massless Kane fermions in HgCdTe crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teppe, F.; Marcinkiewicz, M.; Krishtopenko, S. S.

2016-08-30

It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phasemore » transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 106 m s -1 remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe.« less

Clumped isotope thermometry in deeply buried sedimentary carbonates: The effects of C-O bond reordering and recrystallization

NASA Astrophysics Data System (ADS)

Passey, B. H.; Shenton, B.; Grossman, E. L.; Henkes, G. A.; Laya, J. C.; Perez-Huerta, A.

2014-12-01

Constraining the thermal histories of sedimentary basins is fundamental to a range of geologic applications including tectonics, petroleum system analysis, and the genesis of ore deposits. Carbonate rocks can serve as archives of basin thermal histories through solid-state reordering of their 13C-18O, or 'clumped isotope', bonds at elevated burial temperatures. Here we present one of the first applied studies of carbonate clumped isotope reordering to explore the diagenetic and thermal histories of exhumed brachiopods, crinoids, cements, and host rock in the Permian Palmarito Formation, Venezuela and the Carboniferous Bird Spring Formation, Nevada, USA. Carbonate components in the Palmarito Formation, buried to ~4 km depth, yield statistically indistinguishable clumped isotope temperatures (T(Δ47)) ranging from 86 to 122 °C. Clumped isotope temperatures of components in the more deeply buried Bird Spring Formation (>5 km), range from ~100 to 165 °C and differ by component type, with brachiopods and pore-filling cements yielding the highest T(Δ47) (mean = 153 and 141 °C, respectively) and crinoids and host rock yielding significantly cooler T(Δ47) (mean = 103 and 114 °C). New high-resolution thermal histories are coupled with kinetic models to predict the extent of solid-state C-O bond reordering during burial and exhumation for both sites. Application of these models suggests that brachiopods in the Palmarito Formation experienced partial bond reordering without complete equilibration of clumped isotopes at maximum burial temperature. In contrast, clumped isotope bonds of brachiopods from the Bird Spring Formation appear to have completely equilibrated at maximum burial temperature, and now reflect blocking temperatures 'locked-in' during cooling. The 40-50 °C cooler clumped isotope temperatures measured in Bird Spring Formation crinoids and host rock can be explained by both recrystallization and cementation during shallow burial and a greater inherent resistance to solid-state reordering than brachiopods.

Characterization of the temperature and humidity-dependent phase diagram of amorphous nanoscale organic aerosols.

PubMed

Rothfuss, Nicholas E; Petters, Markus D

2017-03-01

Atmospheric aerosols can exist in amorphous semi-solid or glassy phase states. These states are determined by the temperature (T) and relative humidity (RH). New measurements of viscosity for amorphous semi-solid nanometer size sucrose particles as a function of T and RH are reported. Viscosity is measured by inducing coagulation between two particles and probing the thermodynamic states that induce the particle to relax into a sphere. It is shown that the glass transition temperature can be obtained by extrapolation to 10 12 Pa s from the measured temperature-dependent viscosity in the 10 6 to 10 7 Pa s range. The experimental methodology was refined to allow isothermal probing of RH dependence and to increase the range of temperatures over which the dry temperature dependence can be studied. Several experiments where one monomer was sodium dodecyl sulfate (SDS), which remains solid at high RH, are also reported. These sucrose-SDS dimers were observed to relax into a sphere at T and RH similar to those observed in sucrose-sucrose dimers, suggesting that amorphous sucrose will flow over an insoluble particle at a viscosity similar to that characteristic of coalescence between two sucrose particles. Possible physical and analytical implications of this observation are considered. The data reported here suggest that semi-solid viscosity between 10 4 and 10 12 Pa s can be modelled over a wide range of T and RH using an adapted Vogel-Fulcher-Tammann equation and the Gordon-Taylor mixing rule. Sensitivity of modelled viscosity to variations in dry glass transition temperature, Gordon-Taylor constant, and aerosol hygroscopicity are explored, along with implications for atmospheric processes such as ice nucleation of glassy organic aerosols in the upper free troposphere. The reported measurement and modelling framework provides a template for characterizing the phase diagram of other amorphous aerosol systems, including secondary organic aerosols.

Fiber Bragg Grating Sensors for the Oil Industry.

PubMed

Qiao, Xueguang; Shao, Zhihua; Bao, Weijia; Rong, Qiangzhou

2017-02-23

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group's research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors' amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry.

Fiber Bragg Grating Sensors for the Oil Industry

PubMed Central

Qiao, Xueguang; Shao, Zhihua; Bao, Weijia; Rong, Qiangzhou

2017-01-01

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group’s research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors’ amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry. PMID:28241460

Pyrolysis process for the treatment of scrap tyres: preliminary experimental results.

PubMed

Galvagno, S; Casu, S; Casabianca, T; Calabrese, A; Cornacchia, G

2002-01-01

The aim of this work is the evaluation, on a pilot scale, of scrap tyre pyrolysis process performance and the characteristics of the products under different process parameters, such as temperature, residence time, pressure, etc. In this frame, a series of tests were carried out at varying process temperatures between 550 and 680 degrees C, other parameters being equal. Pyrolysis plant process data are collected by an acquisition system; scrap tyre samples used for the treatment, solid and liquid by-products and produced syngas were analysed through both on-line monitoring (for gas) and laboratory analyses. Results show that process temperature, in the explored range, does not seem to seriously influence the volatilisation reaction yield, at least from a quantitative point of view, while it observably influences the distribution of the volatile fraction (liquid and gas) and by-products characteristics.

Ultra-Low-Power Cryogenic SiGe Low-Noise Amplifiers: Theory and Demonstration

NASA Astrophysics Data System (ADS)

Montazeri, Shirin; Wong, Wei-Ting; Coskun, Ahmet H.; Bardin, Joseph C.

2016-01-01

Low-power cryogenic low-noise amplifiers (LNAs) are desired to ease the cooling requirements of ultra-sensitive cryogenically cooled instrumentation. In this paper, the tradeoff between power and noise performance in silicon-germanium LNAs is explored to study the possibility of operating these devices from low supply voltages. A new small-signal heterojunction bipolar transistor noise model applicable to both the forward-active and saturation regimes is developed from first principles. Experimental measurements of a device across a wide range of temperatures are then presented and the dependence of the noise parameters on collector-emitter voltage is described. This paper concludes with the demonstration of a high-gain 1.8-3.6-GHz cryogenic LNA achieving a noise temperature of 3.4-5 K while consuming just 290 μW when operating at 15-K physical temperature.

Bose-Einstein Condensation of Long-Lifetime Polaritons in Thermal Equilibrium.

PubMed

Sun, Yongbao; Wen, Patrick; Yoon, Yoseob; Liu, Gangqiang; Steger, Mark; Pfeiffer, Loren N; West, Ken; Snoke, David W; Nelson, Keith A

2017-01-06

The experimental realization of Bose-Einstein condensation (BEC) with atoms and quasiparticles has triggered wide exploration of macroscopic quantum effects. Microcavity polaritons are of particular interest because quantum phenomena such as BEC and superfluidity can be observed at elevated temperatures. However, polariton lifetimes are typically too short to permit thermal equilibration. This has led to debate about whether polariton condensation is intrinsically a nonequilibrium effect. Here we report the first unambiguous observation of BEC of optically trapped polaritons in thermal equilibrium in a high-Q microcavity, evidenced by equilibrium Bose-Einstein distributions over broad ranges of polariton densities and bath temperatures. With thermal equilibrium established, we verify that polariton condensation is a phase transition with a well-defined density-temperature phase diagram. The measured phase boundary agrees well with the predictions of basic quantum gas theory.

Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

NASA Astrophysics Data System (ADS)

Stolper, Daniel A.; Eiler, John M.; Higgins, John A.

2018-04-01

The measurement of multiply isotopically substituted ('clumped isotope') carbonate groups provides a way to reconstruct past mineral formation temperatures. However, dissolution-reprecipitation (i.e., recrystallization) reactions, which commonly occur during sedimentary burial, can alter a sample's clumped-isotope composition such that it partially or wholly reflects deeper burial temperatures. Here we derive a quantitative model of diagenesis to explore how diagenesis alters carbonate clumped-isotope values. We apply the model to a new dataset from deep-sea sediments taken from Ocean Drilling Project site 807 in the equatorial Pacific. This dataset is used to ground truth the model. We demonstrate that the use of the model with accompanying carbonate clumped-isotope and carbonate δ18O values provides new constraints on both the diagenetic history of deep-sea settings as well as past equatorial sea-surface temperatures. Specifically, the combination of the diagenetic model and data support previous work that indicates equatorial sea-surface temperatures were warmer in the Paleogene as compared to today. We then explore whether the model is applicable to shallow-water settings commonly preserved in the rock record. Using a previously published dataset from the Bahamas, we demonstrate that the model captures the main trends of the data as a function of burial depth and thus appears applicable to a range of depositional settings.

Use of a Frequency Divider to Evaluate an SOI NAND Gate Device, Type CHT-7400, for Wide Temperature Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2010-01-01

Frequency dividers constitute essential elements in designing phase-locked loop circuits and microwave systems. In addition, they are used in providing required clocking signals to microprocessors and can be utilized as digital counters. In some applications, particularly space missions, electronics are often exposed to extreme temperature conditions. Therefore, it is required that circuits designed for such applications incorporate electronic parts and devices that can tolerate and operate efficiently in harsh temperature environments. While present electronic circuits employ COTS (commercial-off- the-shelf) parts that necessitate and are supported with some form of thermal control systems to maintain adequate temperature for proper operation, it is highly desirable and beneficial if the thermal conditioning elements are eliminated. Amongst these benefits are: simpler system design, reduced weight and size, improved reliability, simpler maintenance, and reduced cost. Devices based on silicon-on-insulator (SOI) technology, which utilizes the addition of an insulation layer in the device structure to reduce leakage currents and to minimize parasitic junctions, are well suited for high temperatures due to reduced internal heating as compared to the conventional silicon devices, and less power consumption. In addition, SOI electronic integrated circuits display good tolerance to radiation by virtue of introducing barriers or lengthening the path for penetrating particles and/or providing a region for trapping incident ionization. The benefits of these parts make them suitable for use in deep space and planetary exploration missions where extreme temperatures and radiation are encountered. Although designed for high temperatures, very little data exist on the operation of SOI devices and circuits at cryogenic temperatures. In this work, the performance of a divide-by-two frequency divider circuit built using COTS SOI logic gates was evaluated over a wide temperature range and thermal cycling to determine suitability for use in space exploration missions and terrestrial fields under extreme temperature conditions.

Variability of Diurnal Temperature Range During Winter Over Western Himalaya: Range- and Altitude-Wise Study

NASA Astrophysics Data System (ADS)

Shekhar, M. S.; Devi, Usha; Dash, S. K.; Singh, G. P.; Singh, Amreek

2018-04-01

The current trends in diurnal temperature range, maximum temperature, minimum temperature, mean temperature, and sun shine hours over different ranges and altitudes of Western Himalaya during winter have been studied. Analysis of 25 years of data shows an increasing trend in diurnal temperature range over all the ranges and altitudes of Western Himalaya during winter, thereby confirming regional warming of the region due to present climate change and global warming. Statistical studies show significant increasing trend in maximum temperature over all the ranges and altitudes of Western Himalaya. Minimum temperature shows significant decreasing trend over Pir Panjal and Shamshawari range and significant increasing trend over higher altitude of Western Himalaya. Similarly, sunshine hours show significant decreasing trend over Karakoram range. There exists strong positive correlation between diurnal temperature range and maximum temperature for all the ranges and altitudes of Western Himalaya. Strong negative correlation exists between diurnal temperature range and minimum temperature over Shamshawari and Great Himalaya range and lower altitude of Western Himalaya. Sunshine hours show strong positive correlation with diurnal temperature range over Pir Panjal and Great Himalaya range and lower and higher altitudes.

Exploring the Limits of Cell Adhesion under Shear Stress within Physiological Conditions and beyond on a Chip.

PubMed

Stamp, Melanie E M; Jötten, Anna M; Kudella, Patrick W; Breyer, Dominik; Strobl, Florian G; Geislinger, Thomas M; Wixforth, Achim; Westerhausen, Christoph

2016-10-21

Cell adhesion processes are of ubiquitous importance for biomedical applications such as optimization of implant materials. Here, not only physiological conditions such as temperature or pH, but also topographical structures play crucial roles, as inflammatory reactions after surgery can diminish osseointegration. In this study, we systematically investigate cell adhesion under static, dynamic and physiologically relevant conditions employing a lab-on-a-chip system. We screen adhesion of the bone osteosarcoma cell line SaOs-2 on a titanium implant material for pH and temperature values in the physiological range and beyond, to explore the limits of cell adhesion, e.g., for feverish and acidic conditions. A detailed study of different surface roughness R q gives insight into the correlation between the cells' abilities to adhere and withstand shear flow and the topography of the substrates, finding a local optimum at R q = 22 nm. We use shear stress induced by acoustic streaming to determine a measure for the ability of cell adhesion under an external force for various conditions. We find an optimum of cell adhesion for T = 37 °C and pH = 7.4 with decreasing cell adhesion outside the physiological range, especially for high T and low pH. We find constant detachment rates in the physiological regime, but this behavior tends to collapse at the limits of 41 °C and pH 4.

Climatic niche and flowering and fruiting phenology of an epiphytic plant.

PubMed

Barve, Narayani; Martin, Craig E; Peterson, A Townsend

2015-09-10

Species have geographic distributions constrained by combinations of abiotic factors, biotic factors and dispersal-related factors. Abiotic requirements vary across the life stages for a species; for plant species, a particularly important life stage is when the plant flowers and develops seeds. A previous year-long experiment showed that ambient temperature of 5-35 °C, relative humidity of >50 % and ≤15 consecutive rainless days are crucial abiotic conditions for Spanish moss (Tillandsia usneoides L.). Here, we explore whether these optimal physiological intervals relate to the timing of the flowering and fruiting periods of Spanish moss across its range. As Spanish moss has a broad geographic range, we examined herbarium specimens to detect and characterize flowering/fruiting periods for the species across the Americas; we used high-temporal-resolution climatic data to assess the availability of optimal conditions for Spanish moss populations during each population's flowering period. We explored how long populations experience suboptimal conditions and found that most populations experience suboptimal conditions in at least one environmental dimension. Flowering and fruiting periods of Spanish moss populations are either being optimized for one or a few parameters or may be adjusted such that all parameters are suboptimal. Spanish moss populations appear to be constrained most closely by minimum temperature during this period. Published by Oxford University Press on behalf of the Annals of Botany Company.

Submillimeter Planetary Atmospheric Chemistry Exploration Sounder

NASA Technical Reports Server (NTRS)

Schlecht, Erich T.; Allen, Mark A.; Gill, John J.; Choonsup, Lee; Lin, Robert H.; Sin, Seth; Mehdi, Imran; Siegel, Peter H.; Maestrini, Alain

2013-01-01

Planetary Atmospheric Chemistry Exploration Sounder (SPACES), a high-sensitivity laboratory breadboard for a spectrometer targeted at orbital planetary atmospheric analysis. The frequency range is 520 to 590 GHz, with a target noise temperature sensitivity of 2,500 K for detecting water, sulfur compounds, carbon compounds, and other atmospheric constituents. SPACES is a prototype for a powerful tool for the exploration of the chemistry and dynamics of any planetary atmosphere. It is fundamentally a single-pixel receiver for spectral signals emitted by the relevant constituents, intended to be fed by a fixed or movable telescope/antenna. Its front-end sensor translates the received signal down to the 100-MHz range where it can be digitized and the data transferred to a spectrum analyzer for processing, spectrum generation, and accumulation. The individual microwave and submillimeter wave components (mixers, LO high-powered amplifiers, and multipliers) of SPACES were developed in cooperation with other programs, although with this type of instrument in mind. Compared to previous planetary and Earth science instruments, its broad bandwidth (approx. =.13%) and rapid tunability (approx. =.10 ms) are new developments only made possible recently by the advancement in submillimeter circuit design and processing at JPL.

Body Temperature Measurements for Metabolic Phenotyping in Mice.

PubMed

Meyer, Carola W; Ootsuka, Youichirou; Romanovsky, Andrej A

2017-01-01

Key Points Rectal probing is subject to procedural bias. This method is suitable for first-line phenotyping, provided probe depth and measurement duration are standardized. It is also useful for detecting individuals with out-of-range body temperatures (during hypothermia, torpor).The colonic temperature attained by inserting the probe >2 cm deep is a measure of deep (core) body temperature.IR imaging of the skin is useful for detecting heat leaks and autonomous thermoregulatory alterations, but it does not measure body temperature.Temperature of the hairy or shaved skin covering the inter-scapular brown adipose tissue can be used as a measure of BAT thermogenesis. However, obtaining such measurements of sufficient quality is very difficult, and interpreting them can be tricky. Temperature differences between the inter-scapular and lumbar areas can be a better measure of the thermogenic activity of inter-scapular brown adipose tissue.Implanted probes for precise determination of BAT temperature (changes) should be fixed close to the Sulzer's vein. For measurement of BAT thermogenesis, core body temperature and BAT temperature should be recorded simultaneously.Tail temperature is suitable to compare the presence or absence of vasoconstriction or vasodilation.Continuous, longitudinal monitoring of core body temperature is preferred over single probing, as the readings are taken in a non-invasive, physiological context.Combining core body temperature measurements with metabolic rate measurements yields insights into the interplay between heat production and heat loss (thermal conductance), potentially revealing novel thermoregulatory phenotypes. Endothermic organisms rely on tightly balanced energy budgets to maintain a regulated body temperature and body mass. Metabolic phenotyping of mice, therefore, often includes the recording of body temperature. Thermometry in mice is conducted at various sites, using various devices and measurement practices, ranging from single-time probing to continuous temperature imaging. Whilst there is broad agreement that body temperature data is of value, procedural considerations of body temperature measurements in the context of metabolic phenotyping are missing. Here, we provide an overview of the various methods currently available for gathering body temperature data from mice. We explore the scope and limitations of thermometry in mice, with the hope of assisting researchers in the selection of appropriate approaches, and conditions, for comprehensive mouse phenotypic analyses.

Heat flow, deep formation temperature and thermal structure of the Tarim Basin, northwest China

NASA Astrophysics Data System (ADS)

Liu, Shaowen; Lei, Xiao; Feng, Changge; Li, Xianglan

2016-04-01

Geothermal regime of a sedimentary basin not only provides constraint on understanding the basin formation and evolution, but also offers fundamental parameters for hydrocarbon resources assessment. As one of three Precambrian blocks in China, the Tarim craton is also a current hydrocarbon exploration target where the largest sedimentary basin (Tarim Basin) develops with great potential. Although considerable advancement of geothermal regime of this basin has been made during the past decades, nearly all the temperature data in previous studies are from the exploration borehole formation testing temperatures. Recently, we have conducted the steady-state temperature logging in the Tarim basin, and measured abundant rock thermal properties, enabling us to re-visit the thermal regime of this area with more confidence. Our results show that the present-day geothermal gradients for the Tarim Basin vary from 23 K/km to 27 K/km, with a mean of 22 K/km; the values of heat flow range from 40 mW/m2 to 49 mW/m2, with a mean of 43 mW/m2. These new data confirmed that the Tarim Basin has relatively low heat flow and shares similar geothermal regime with other Precambrian cratons in the world. In addition, the new temperatures from the steady-state logs are larger than the bottom hole temperatures (BHT) as 22 degree Celsius, indicating the thermal non-equilibrium for the BHTs used in previous studies. Spatial distribution of the estimated formation temperatures-at-depth of 1~5km within the basin is similar and mainly controlled by crystalline basement pattern. Generally, the temperatures at the depth of 1km range from 29 to 41 degree Celsius, with a mean of 35 degree Celsius; while the temperatures at 3km vary from 63 to 100 degree Celsius, and the mean is 82 degree Celsius; at 5km below the surface, the temperatures fall into a range between 90 and 160 degree Celsius, with a mean of 129 degree Celsius. We further proposed the long-term low geothermal background and large burial depth are the favorable conditions for hydrocarbon generation and preservation. As far as heat budget of the Tarim Basin is concerned, the radiogenic heat from the sedimentary cover accounts only for 20 percent of the surface heat flow (~9 mW/m2), while the mantle heat flow is estimated to be low as 6~15 mW/m2; this indicates the dominant contribution of crustal radiogenic heat to the observed heat flow. Any variations in surface heat flow for the Tarim Basin can be due only to changes in crustal heat production. Thermal contrast between the Tarim Basin and Tibet Plateau, represented by a difference in surface heat flow and deep crustal temperature, is remarkable. This inherited thermal contrast can be traced as far as before the India-Asia collision. Moreover, the lithosphere beneath the Tarim Basin is sufficiently strong to resist the gravitational potential energy difference and tectonic forces from Tibet. The observed thermal and rheological contrast accounts for the differential Cenozoic deformation in the Tarim Basin and adjacent areas.

Experimental optimum design and luminescence properties of NaY(Gd)(MoO4)2:Er3+ phosphors

NASA Astrophysics Data System (ADS)

Jia-Shi, Sun; Sai, Xu; Shu-Wei, Li; Lin-Lin, Shi; Zi-Hui, Zhai; Bao-Jiu, Chen

2016-06-01

Three-factor orthogonal design (OD) of Er3+/Gd3+/T (calcination temperature) is used to optimize the luminescent intensity of NaY(Gd)(MoO4)2:Er3+ phosphor. Firstly, the uniform design (UD) is introduced to explore the doping concentration range of Er3+/Gd3+. Then OD and range analysis are performed based on the results of UD to obtain the primary and secondary sequence and the best combination of Er3+, Gd3+, and T within the experimental range. The optimum sample is prepared by the high temperature solid state method. Photoluminescence excitation and emission spectra of the optimum sample are detected. The intense green emissions (530 nm and 550 nm) are observed which originate from Er3+ 2H11/2→ 4I15/2 and 4S3/2→4I15/2, respectively. Thermal effect is investigated in the optimum NaY(Gd3+)(MoO4)2:Er3+ phosphors, and the green emission intensity decreases as temperature increases. Project supported by Education Reform Fund of Dalian Maritime University, China (Grant No. 2015Y37), the Natural Science Foundation of Liaoning Province, China (Grant Nos. 2015020190 and 2014025010), the Open Fund of the State Key Laboratory on Integrated Optoelectronics, China (Grant No. IOSKL2015KF27), and the Fundamental Research Funds for the Central Universities, China (Grant No. 3132016121).

A stochastic, evolutionary model for range shifts and richness on tropical elevational gradients under Quaternary glacial cycles

PubMed Central

Colwell, Robert K.; Rangel, Thiago F.

2010-01-01

Quaternary glacial–interglacial cycles repeatedly forced thermal zones up and down the slopes of mountains, at all latitudes. Although no one doubts that these temperature cycles have left their signature on contemporary patterns of geography and phylogeny, the relative roles of ecology and evolution are not well understood, especially for the tropics. To explore key mechanisms and their interactions in the context of chance events, we constructed a geographical range-based, stochastic simulation model that incorporates speciation, anagenetic evolution, niche conservatism, range shifts and extinctions under late Quaternary temperature cycles along tropical elevational gradients. In the model, elevational patterns of species richness arise from the differential survival of founder lineages, consolidated by speciation and the inheritance of thermal niche characteristics. The model yields a surprisingly rich variety of realistic patterns of phylogeny and biogeography, including close matches to a variety of contemporary elevational richness profiles from an elevational transect in Costa Rica. Mountaintop extinctions during interglacials and lowland extinctions at glacial maxima favour mid-elevation lineages, especially under the constraints of niche conservatism. Asymmetry in temperature (greater duration of glacial than of interglacial episodes) and in lateral area (greater land area at low than at high elevations) have opposing effects on lowland extinctions and the elevational pattern of species richness in the model—and perhaps in nature, as well. PMID:20980317

Ab initio calculation of electron–phonon coupling in monoclinic β-Ga{sub 2}O{sub 3} crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Krishnendu, E-mail: kghosh3@buffalo.edu; Singisetti, Uttam, E-mail: uttamsin@buffalo.edu

2016-08-15

The interaction between electrons and vibrational modes in monoclinic β-Ga{sub 2}O{sub 3} is theoretically investigated using ab-initio calculations. The large primitive cell of β-Ga{sub 2}O{sub 3} gives rise to 30 phonon modes all of which are taken into account in transport calculation. The electron-phonon interaction is calculated under density functional perturbation theory and then interpolated using Wannier–Fourier interpolation. The long-range interaction elements between electrons and polar optical phonon (POP) modes are calculated separately using the Born effective charge tensor. The direction dependence of the long-range POP coupling in a monoclinic crystal is explored and is included in the transport calculations.more » Scattering rate calculations are done using the Fermi golden rule followed by solving the Boltzmann transport equation using the Rode's method to estimate low field mobility. A room temperature mobility of 115 cm{sup 2}/V s is observed. Comparison with recent experimentally reported mobility is done for a wide range of temperatures (30 K–650 K). It is also found that the POP interaction dominates the electron mobility under low electric field conditions. The relative contribution of the different POP modes is analyzed and the mode 21 meV POP is found to have the highest impact on low field electron mobility at room temperature.« less

Operation of SOI P-Channel Field Effect Transistors, CHT-PMOS30, under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Electronic systems are required to operate under extreme temperatures in NASA planetary exploration and deep space missions. Electronics on-board spacecraft must also tolerate thermal cycling between extreme temperatures. Thermal management means are usually included in today s spacecraft systems to provide adequate temperature for proper operation of the electronics. These measures, which may include heating elements, heat pipes, radiators, etc., however add to the complexity in the design of the system, increases its cost and weight, and affects its performance and reliability. Electronic parts and circuits capable of withstanding and operating under extreme temperatures would reflect in improvement in system s efficiency, reducing cost, and improving overall reliability. Semiconductor chips based on silicon-on-insulator (SOI) technology are designed mainly for high temperature applications and find extensive use in terrestrial well-logging fields. Their inherent design offers advantages over silicon devices in terms of reduced leakage currents, less power consumption, faster switching speeds, and good radiation tolerance. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. Experimental investigation on the operation of SOI, N-channel field effect transistors under wide temperature range was reported earlier [1]. This work examines the performance of P-channel devices of these SOI transistors. The electronic part investigated in this work comprised of a Cissoid s CHT-PMOS30, high temperature P-channel MOSFET (metal-oxide semiconductor field-effect transistor) device [2]. This high voltage, medium-power transistor is designed for geothermal well logging applications, aerospace and avionics, and automotive industry, and is specified for operation in the temperature range of -55 C to +225 C. Table I shows some specifications of this transistor [2]. The CHT-PMOS30 device was characterized at various temperatures over the range of -190 C to +225 C in terms of its voltage/current characteristic curves. The test temperatures included +22, -50, -100, -150, -175, -190, +50, +100, +150, +175, +200, and +225 C. Limited thermal cycling testing was also performed on the device. These tests consisted of subjecting the transistor to a total of twelve thermal cycles between -190 C and +225 C. A temperature rate of change of 10 C/min and a soak time at the test temperature of 10 minutes were used throughout this work. Post-cycling measurements were also performed at selected temperatures. In addition, re-start capability at extreme temperatures, i.e. power switched on while the device was soaking for a period of 20 minutes at the test temperatures of -190 C and +225 C, was investigated.

Thermal ecology of the Australian agamid Pogona barbata.

PubMed

Schäuble, Chloe S; Grigg, Gordon C

1998-05-01

This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994-1995) and autumn (1995). Seasonal patterns of body temperature (T b ) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those estimated for a thermoconforming lizard. The study lizards' field T b s varied seasonally (summer: grand daily mean (GDM) 34.6 ± 0.6°C, autumn: GDM 27.5 ± 0.3°C) as did maximum and minimum available operative temperatures (summer: GDM T max 42.1 ± 1.7°C, T min 32.2 ± 1.0°C, autumn: GDM T max 31.7 ± 1.2°C, T min 26.4 ± 0.5°C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field T b s from their selected ranges being only 2.1 ± 0.5°C in summer, compared to 4.4 ± 0.5°C in autumn. This seasonal difference was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative temperatures rarely precluded lizards from attaining field T b s within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior appear to have had an important influence on seasonal levels of thermoregulatory effort.

An experimental approach to manufacturing technology of historical glass (XIII-XV centuries). Comparison with current glassmaking technology.

NASA Astrophysics Data System (ADS)

Tarrago, Mariona; Gimeno, Domingo; Bazzocchi, Flavia; Garcia-Valles, Maite; Martinez, Salvador

2015-04-01

One of the major and less explored issues in the characterization of historical glasses is the determination of their viscosity as a function of temperature in order to constrain technological aspects of glass production. Until now, assumptions on temperatures have been based on mathematical models based on chemical compositions. Hence, the topic of this work is to explore the technology of stained glass production related to the workability and melting process of the glass by experimental laboratory measurements. This work presents the analysis of viscosity of glasses from different historical sites and chemical compositions: four from Santes Creus (Tarragona, XIII century), two of classical medieval stained glass window from Santa Maria de Pedralbes (Barcelona, mid XIV century), and three of evolved late-medieval type from Santa Maria del Mar (Barcelona first half of XV century), and one sample of soda-lime industrial glass by means of Hot-Stage Microscopy and glass transformation temperature Tg by dilatometry. These data are then compared to the predictions on theoretical viscosity obtained from mathematical models based on chemical composition. These samples are classified according to their major modifier in: Na-rich (12-17% of Na2O, between 65-77% of SiO2 and less than 3 % of K2O); Ca-rich (29% of CaO, 54% of SiO2, 4% of K2O, and 4% of Na2O); K-Ca-rich (17 to 21% of K2O, more than 14% of CaO, 49-55% of SiO2and less than 2% of Na2O); Na-Ca-rich (12-14% of Na2O, 9-15% of CaO, 57-71% of SiO2 and < 6% of K2O). Glass transition temperature (Tg) is correlated to chemical composition: 464-492 °C for Na-rich, 645 °C for Ca-rich, 582-586 °C for K-Ca-rich and 497-542 °C for Na-Ca-rich glasses. Experimental viscosity-temperature curves are traced using Tg and fixed viscosity points measured by Hot-Stage microscopy (according to German standard 51730) in order to provide more accurate insight into the phases of glass production process (melting, working, conditioning and annealing ranges). These results are also compared to mathematical models of glass viscosity based on chemical composition. The annealing range (viscosity between 1013.5 and 1012 Pa-s) is reached at temperatures between 484-633°C (strain point) and 509-664°C (upper limit). The working point (viscosity of 103 Pa-s) has temperature values in the range between 958 and 1097°C.

Lithium-Ion Electrolytes Containing Phosphorous-Based, Flame-Retardant Additives

NASA Technical Reports Server (NTRS)

Smart, Marshall C.; Smith, Kiah A.; Bugga, Ratnakumar V.; Prakash, G. K. Surya

2010-01-01

Future NASA missions aimed at exploring Mars, the Moon, and the outer planets require rechargeable batteries that can operate over a wide temperature range (-60 to +60 C) to satisfy the requirements of various applications. In addition, many of these applications will require improved safety, due to their use by humans. Currently, the state-of-the-art lithium-ion (Li-ion) system has been demonstrated to operate over a wide range of temperatures (-40 to +40 C); however, abuse conditions can often lead to cell rupture and fire. The nature of the electrolyte can greatly affect the propensity of the cell/battery to catch fire, given the flammability of the organic solvents used within. Li-ion electrolytes have been developed that contain a flame-retardant additive in conjunction with fluorinated co-solvents to provide a safe system with a wide operating temperature range. Previous work incorporated fluorinated esters into multi-component electrolyte formulations, which were demonstrated to cover a temperature range from 60 to +60 C. This work was described in Fluoroester Co-Solvents for Low-Temperature Li+ Cells (NPO-44626), NASA Tech Briefs, Vol. 33, No. 9 (September 2009), p. 37; and Optimized Li-Ion Electrolytes Con tain ing Fluorinated Ester Co-Solvents (NPO-45824), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 48. Other previous work improved the safety characteristics of the electrolytes by adding flame-retardant additives such as triphenyl phosphate (TPhPh), tri-butyl phosphate (TBuPh), triethyl phosphate (TEtPh), and bis(2,2,2-trifluoroethyl) methyl phosphonate (TFMPo). The current work involves further investigation of other types of flame-retardant additives, including tris(2,2,2-trifluoroethyl) phosphate, tris(2,2,2-trifluoroethyl) phosphite, triphenylphosphite, diethyl ethylphosphonate, and diethyl phenylphosphonate added to an electrolyte composition intended for wide operating temperatures. In general, many of the formulations investigated in this study displayed good performance over a wide temperature range, good cycle life characteristics, and are expected to have improved safety characteristics, such as low flammability. Of the electrolytes studied, 1.0 M LiPF6 in EC+EMC+DEP (20:75:5 v/v %) and 1.0 M LiPF6 in EC+EMC+DPP (20:75:5 v/v %) displayed the best operation at low temperatures, whereas the electrolyte containing triphenylphosphite displayed the best cycle life performance compared to the baseline solution. It is anticipated that further improvements can be made to the life characteristics with the incorporation of a SET promoters (such as VC, vinylene carbonate), which will likely inhibit the decomposition of the flame-retardant additives.

Molecular Mobility in Phase Segregated Bottlebrush Block Copolymer Melts

NASA Astrophysics Data System (ADS)

Yavitt, Benjamin; Gai, Yue; Song, Dongpo; Winter, H. Henning; Watkins, James

We investigate the linear viscoelastic behavior of poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) brush block copolymer (BBCP) materials over a range of vol. fractions and with side chain lengths below the entanglement molecular weights. The high chain mobility of the brush architecture results in rapid micro-phase segregation of the brush copolymer segments, which occurs during thermal annealing at mild temperatures. Master curves of the dynamic moduli were obtained by time-temperature superposition. The reduced degree of chain entanglements leads to a unique liquid-like rheology similar to that of bottlebrush homopolymers, even in the phase segregated state. We also explore the alignment of phase segregated domains at exceptionally low strain amplitudes (γ = 0.01) and mild processing temperatures using small angle X-ray scattering (SAXS). Domain orientation occurred readily at strains within the linear viscoelastic regime without noticeable effect on the moduli. This interplay of high molecular mobility and rapid phase segregation that are exhibited simultaneously in BBCPs is in contrast to the behavior of conventional linear block copolymer (LBCP) analogs and opens up new possibilities for processing BBCP materials for a wide range of nanotechnology applications. NSF Center for Hierarchical Manufacturing at the University of Massachusetts, Amherst (CMMI-1025020).

Climate change and health: Indoor heat exposure in vulnerable populations☆

PubMed Central

White-Newsome, Jalonne L.; Sánchez, Brisa N.; Jolliet, Olivier; Zhang, Zhenzhen; Parker, Edith A.; Dvonch, J. Timothy; O'Neill, Marie S.

2015-01-01

Introduction Climate change is increasing the frequency of heat waves and hot weather in many urban environments. Older people are more vulnerable to heat exposure but spend most of their time indoors. Few published studies have addressed indoor heat exposure in residences occupied by an elderly population. The purpose of this study is to explore the relationship between outdoor and indoor temperatures in homes occupied by the elderly and determine other predictors of indoor temperature. Materials and methods We collected hourly indoor temperature measurements of 30 different homes; outdoor temperature, dewpoint temperature, and solar radiation data during summer 2009 in Detroit, MI. We used mixed linear regression to model indoor temperatures’ responsiveness to weather, housing and environmental characteristics, and evaluated our ability to predict indoor heat exposures based on outdoor conditions. Results Average maximum indoor temperature for all locations was 34.85 °C, 13.8 °C higher than average maximum outdoor temperature. Indoor temperatures of single family homes constructed of vinyl paneling or wood siding were more sensitive than brick homes to outdoor temperature changes and internal heat gains. Outdoor temperature, solar radiation, and dewpoint temperature predicted 38% of the variability of indoor temperatures. Conclusions Indoor exposures to heat in Detroit exceed the comfort range among elderly occupants, and can be predicted using outdoor temperatures, characteristics of the housing stock and surroundings PMID:22071034

Numerical simulation of base flow of a long range flight vehicle

NASA Astrophysics Data System (ADS)

Saha, S.; Rathod, S.; Chandra Murty, M. S. R.; Sinha, P. K.; Chakraborty, Debasis

2012-05-01

Numerical exploration of base flow of a long range flight vehicle is presented for different flight conditions. Three dimensional Navier-Stokes equations are solved along with k-ɛ turbulence model using commercial CFD software. Simulation captured all essential flow features including flow separation at base shoulder, shear layer formation at the jet boundary, recirculation at the base region etc. With the increase in altitude, the plume of the rocket exhaust is seen to bulge more and more and caused more intense free stream and rocket plume interaction leading to higher gas temperature in the base cavity. The flow field in the base cavity is investigated in more detail, which is found to be fairly uniform at different instant of time. Presence of the heat shield is seen to reduce the hot gas entry to the cavity region due to different recirculation pattern in the base region. Computed temperature history obtained from conjugate heat transfer analysis is found to compare very well with flight measured data.

Communication: Polymer entanglement dynamics: Role of attractive interactions

DOE PAGES

Grest, Gary S.

2016-10-10

The coupled dynamics of entangled polymers, which span broad time and length scales, govern their unique viscoelastic properties. To follow chain mobility by numerical simulations from the intermediate Rouse and reptation regimes to the late time diffusive regime, highly coarse grained models with purely repulsive interactions between monomers are widely used since they are computationally the most efficient. In this paper, using large scale molecular dynamics simulations, the effect of including the attractive interaction between monomers on the dynamics of entangled polymer melts is explored for the first time over a wide temperature range. Attractive interactions have little effect onmore » the local packing for all temperatures T and on the chain mobility for T higher than about twice the glass transition T g. Finally, these results, across a broad range of molecular weight, show that to study the dynamics of entangled polymer melts, the interactions can be treated as pure repulsive, confirming a posteriori the validity of previous studies and opening the way to new large scale numerical simulations.« less

The 3.5-m all-SiC telescope for SPICA

NASA Astrophysics Data System (ADS)

Toulemont, Yves; Breysse, Jacques; Pierot, Dominique; Sein, Emmanuel; Nakagawa, Takao; Kaneda, Hidehiro; Onaka, Takashi; Hirabayashi, Masayuki; Narasaki, Katsuhiro; Sakuta, Hironobu; Miura, Shinji

2004-10-01

Placed on the L2 Lagrangian point, the Space Infrared Telescope for Cosmology and Astrophysics (SPICA) will operate in the 5 to 200 μm wavelength range, at 4.5K. The large aperture telescope (3.5m diameter in a single piece) requires a strong manufacturing mastering, associated with high technical performances. The background acquired by EADS-Astrium (France) on the 3.5m Silicone Carbide Herschel Telescope is a key for the success of the SPICA development. EADS-Astrium has been awarded by the Japan Aerospace Exploration Agency (JAXA) and Sumitomo Heavy Industries to assess the feasibility of the 3.5m all SiC telescope through a design phase contract. The Telescope driving requirements are the large diameter of 3.5m especially critical for the manufacturing aspects, and the Wave Front Error which has to be kept below 350nm rms over a large temperature range from ambient to the operational temperature of 4.5K which requires a strong mastering of the distortions.

Molecular dynamics simulation of UO2 nanocrystals melting under isolated and periodic boundary conditions

NASA Astrophysics Data System (ADS)

Boyarchenkov, A. S.; Potashnikov, S. I.; Nekrasov, K. A.; Kupryazhkin, A. Ya.

2012-08-01

Melting of uranium dioxide (UO2) nanocrystals has been studied by molecular dynamics (MD) simulation. Ten recent and widely used sets of pair potentials were assessed in the rigid ion approximation. Both isolated (in vacuum) and periodic boundary conditions (PBC) were explored. Using barostat under PBC the pressure dependences of melting point were obtained. These curves intersected zero near -20 GPa, saturated near 25 GPa and increased nonlinearly in between. Using simulation of surface under isolated boundary conditions (IBC) recommended melting temperature and density jump were successfully reproduced. However, the heat of fusion is still underestimated. These melting characteristics were calculated for nanocrystals of cubic shape in the range of 768-49 152 particles (volume range of 10-1000 nm3). The obtained reciprocal size dependences decreased nonlinearly. Linear and parabolic extrapolations to macroscopic values are considered. The parabolic one is found to be better suited for analysis of the data on temperature and heat of melting.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lingenfelter, A. C., LLNL

Materials for gas turbine engines are required to meet a wide range of temperature and stress application requirements. These alloys exhibit a combination of creep resistance, creep rupture strength, yield and tensile strength over a wide temperature range, resistance to environmental attack (including oxidation, nitridation, sulphidation and carburization), fatigue and thermal fatigue resistance, metallurgical stability and useful thermal expansion characteristics. These properties are exhibited by a series of solid-solution-strengthened and precipitation-hardened nickel, iron and cobalt alloys. The properties needed to meet the turbine engine requirements have been achieved by specific alloy additions, by heat treatment and by thermal mechanical processing.more » A thorough understanding of the metallurgy and metallurgical processing of these materials is imperative in order to successfully fusion weld them. This same basic understanding is required for repair of a component with the added dimension of the potential effects of thermal cycling and environmental exposure the component will have endured in service. This article will explore the potential problems in joining and repair welding these materials.« less

Time Dependent Solution for the He I Line Ratio Electron Temperature and Density Diagnostic in TEXTOR and DIII-D

NASA Astrophysics Data System (ADS)

Munoz Burgos, J. M.; Schmitz, O.; Unterberg, E. A.; Loch, S. D.; Balance, C. P.

2010-11-01

We developed a time dependent solution for the He I line ratio diagnostic. Stationary solution is applied for L-mode at TEXTOR. The radial range is typically limited to a region near the separatrix due to metastable effects, and the atomic data used. We overcome this problem by applying a time dependent solution and thus avoid unphysical results. We use a new R-Matrix with Pseudostates and Convergence Cross-Coupling electron impact excitation and ionization atomic data set into the Collisional Radiative Model (CRM). We include contributions from higher Rydberg states into the CRM by means of the projection matrix. By applying this solution (to the region near the wall) and the stationary solution (near the separatrix), we triple the radial range of the current diagnostic. We explore the possibility of extending this approach to H-mode plasmas in DIII-D by estimating line emission profiles from electron temperature and density Thomson scattering data.

Application of the Taguchi Method for Optimizing the Process Parameters of Producing Lightweight Aggregates by Incorporating Tile Grinding Sludge with Reservoir Sediments

PubMed Central

Chen, How-Ji; Chang, Sheng-Nan; Tang, Chao-Wei

2017-01-01

This study aimed to apply the Taguchi optimization technique to determine the process conditions for producing synthetic lightweight aggregate (LWA) by incorporating tile grinding sludge powder with reservoir sediments. An orthogonal array L16(45) was adopted, which consisted of five controllable four-level factors (i.e., sludge content, preheat temperature, preheat time, sintering temperature, and sintering time). Moreover, the analysis of variance method was used to explore the effects of the experimental factors on the particle density, water absorption, bloating ratio, and loss on ignition of the produced LWA. Overall, the produced aggregates had particle densities ranging from 0.43 to 2.1 g/cm3 and water absorption ranging from 0.6% to 13.4%. These values are comparable to the requirements for ordinary and high-performance LWAs. The results indicated that it is considerably feasible to produce high-performance LWA by incorporating tile grinding sludge with reservoir sediments. PMID:29125576

Accessing thermoplastic processing windows in metallic glasses using rapid capacitive discharge

PubMed Central

Kaltenboeck, Georg; Harris, Thomas; Sun, Kerry; Tran, Thomas; Chang, Gregory; Schramm, Joseph P.; Demetriou, Marios D.; Johnson, William L.

2014-01-01

The ability of the rapid-capacitive discharge approach to access optimal viscosity ranges in metallic glasses for thermoplastic processing is explored. Using high-speed thermal imaging, the heating uniformity and stability against crystallization of Zr35Ti30Cu7.5Be27.5 metallic glass heated deeply into the supercooled region is investigated. The method enables homogeneous volumetric heating of bulk samples throughout the entire supercooled liquid region at high rates (~105 K/s) sufficient to bypass crystallization throughout. The crystallization onsets at temperatures in the vicinity of the “crystallization nose” were identified and a Time-Temperature-Transformation diagram is constructed, revealing a “critical heating rate” for the metallic glass of ~1000 K/s. Thermoplastic process windows in the optimal viscosity range of 100–104 Pa·s are identified, being confined between the glass relaxation and the eutectic crystallization transition. Within this process window, near-net forging of a fine precision metallic glass part is demonstrated. PMID:25269892

Application of the Taguchi Method for Optimizing the Process Parameters of Producing Lightweight Aggregates by Incorporating Tile Grinding Sludge with Reservoir Sediments.

PubMed

Chen, How-Ji; Chang, Sheng-Nan; Tang, Chao-Wei

2017-11-10

This study aimed to apply the Taguchi optimization technique to determine the process conditions for producing synthetic lightweight aggregate (LWA) by incorporating tile grinding sludge powder with reservoir sediments. An orthogonal array L 16 (4⁵) was adopted, which consisted of five controllable four-level factors (i.e., sludge content, preheat temperature, preheat time, sintering temperature, and sintering time). Moreover, the analysis of variance method was used to explore the effects of the experimental factors on the particle density, water absorption, bloating ratio, and loss on ignition of the produced LWA. Overall, the produced aggregates had particle densities ranging from 0.43 to 2.1 g/cm³ and water absorption ranging from 0.6% to 13.4%. These values are comparable to the requirements for ordinary and high-performance LWAs. The results indicated that it is considerably feasible to produce high-performance LWA by incorporating tile grinding sludge with reservoir sediments.

McGee Mountain Shallow (2m) Temperature Survey, Humboldt County, Nevada 2009

DOE Data Explorer

Richard Zehner

2009-01-01

This shapefile contains location and attribute data for a shallow (2 meter) temperature survey conducted by Geothermal Technical Partners, Inc. during late 2008 and early 2009. Temperatures at 2m depth were measured at 192 separate points as outlined by Coolbaugh et al., 2007. The purpose of the survey was to try and detect a shallow thermal anomaly associated with the McGee Mountain geothermal area as discovered by Phillips Petroleum and Earth Power Resources in the late 1970’s. Drilling identified ~120oC temperatures at ~100m depth. This 2-meter survey delineated what was interpreted as a steam-heated fault zone centered along a range front fault in the vicinity of the drilled holes and fumaroles. Coolbaugh, M.F., Sladek, C., Faulds, J.E., Zehner, R.E., and Oppliger, G.L., 2007, Use of rapid temperature measurements at a 2-meter depth to augment deeper temperature gradient drilling: Proceedings, 32nd Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, Jan. 22-24, 2007, p. 109-116. Zehner, R., Tullar, K., and Rutledge, E., 2012, Effectiveness of 2-Meter and geoprobe shallow temperature surveys in early stage geothermal exploration: Geothermal Resources Council Transactions, v. 36, in press.

Plasma sprayed hydroxyapatite coatings on titanium substrates. Part 1: Mechanical properties and residual stress levels.

PubMed

Tsui, Y C; Doyle, C; Clyne, T W

1998-11-01

Hydroxyapatite (HA) coatings have been sprayed on to substrates of Ti-6Al-4V, using a range of input power levels and plasma gas mixtures. Coatings have also been produced on substrates of mild steel and tungsten, in order to explore certain aspects of the mechanical behaviour of HA without the complication of yielding or creep in the substrate. Studies have been made of the phase constitution, porosity, degree of crystallinity, OH ion content, microstructure and surface roughness of the HA coatings. The Young's moduli in tension and in compression were evaluated by the cantilever beam bend test using a tungsten/HA composite beam. The flexural Young's modulus was determined using a free-standing deposit under the same test. Adhesion was characterised using the single-edge notch-bend test; this is considered superior to the tensile bond strength test in common use. Measured interfacial fracture energies were of the order 1-10 J m(-2). Stress levels were investigated using specimen curvature measurements in conjunction with a numerical process model. The quenching stress for HA was measured to be about 10-25 MPa and the residual stress level in HA coatings at room temperature are predicted to lie in the approximate range of 20-40 MPa (tensile). These residual stresses could be reduced in magnitude by maintaining the substrate at a low temperature (possibly below room temperature) during spraying and it may be worthwhile to explore this. Ideally, the HA coating should have low porosity, high cohesive strength, good adhesion to the substrate, a high degree of crystallinity and high chemical purity and phase stability. In practice, such combinations are rather difficult to achieve by just varying the spraying parameters.

Thermal stability of inorganic and organic compounds in atmospheric particulate matter

NASA Astrophysics Data System (ADS)

Perrino, Cinzia; Marconi, Elisabetta; Tofful, Luca; Farao, Carmela; Materazzi, Stefano; Canepari, Silvia

2012-07-01

The thermal behaviour of atmospheric particulate matter (PM) has been investigated by using different analytical approaches to explore the added value offered by these technique in environmental studies. The thermogravimetric analysis (TGA), carried out on both certified material and real PM samples, has shown that several mass losses can be detected starting from 80 °C up to above 500 °C, when pyrolysis occur. Thermo-optical analysis of PM and ion chromatographic analysis of the residual have shown that the mass losses in the temperature range 80-180 °C are not justified by the release of either organic or inorganic compounds; it can be thus attributed to the release of weakly and strongly bound water. Release of water has also been evidenced in the temperature range 225-275 °C. The release of ammonium chloride and nitrate has been detected only above 80 °C. This indicates that the release of nitric acid, hydrochloric acid and ammonia, which is observed downstream of the filters during the sampling of atmospheric PM at ambient temperature, cannot be reproduced off-line, after the end of the sampling. We successfully explored one of the possible explanations, that is the desorption of HNO3, HCl and NH3 adsorbed on collected particles. NH4NO3 and NH4Cl, which can be thermally released by the filter, exhibit a different thermal behaviour from NaNO3 and NaCl, which are thermally stable up to 370 °C. This different behaviour can be used to discriminate between natural and secondary sources of atmospheric inorganic salts, as the interconversion that is observed when heating mixtures of pure salts resulted to be not relevant when heating real PM samples.

Lithium Iron Phosphate Cell Performance Evaluations for Lunar Extravehicular Activities

NASA Technical Reports Server (NTRS)

Reid, Concha

2007-01-01

Lithium-ion battery cells are being evaluated for their ability to provide primary power and energy storage for NASA s future Exploration missions. These missions include the Orion Crew Exploration Vehicle, the Ares Crew Launch Vehicle Upper Stage, Extravehicular Activities (EVA, the advanced space suit), the Lunar Surface Ascent Module (LSAM), and the Lunar Precursor and Robotic Program (LPRP), among others. Each of these missions will have different battery requirements. Some missions may require high specific energy and high energy density, while others may require high specific power, wide operating temperature ranges, or a combination of several of these attributes. EVA is one type of mission that presents particular challenges for today s existing power sources. The Portable Life Support System (PLSS) for the advanced Lunar surface suit will be carried on an astronaut s back during eight hour long sorties, requiring a lightweight power source. Lunar sorties are also expected to occur during varying environmental conditions, requiring a power source that can operate over a wide range of temperatures. Concepts for Lunar EVAs include a primary power source for the PLSS that can recharge rapidly. A power source that can charge quickly could enable a lighter weight system that can be recharged while an astronaut is taking a short break. Preliminary results of Al23 Ml 26650 lithium iron phosphate cell performance evaluations for an advanced Lunar surface space suit application are discussed in this paper. These cells exhibit excellent recharge rate capability, however, their specific energy and energy density is lower than typical lithium-ion cell chemistries. The cells were evaluated for their ability to provide primary power in a lightweight battery system while operating at multiple temperatures.

The second virial coefficient of bounded Mie potentials

NASA Astrophysics Data System (ADS)

Heyes, D. M.; Pereira de Vasconcelos, T.

2017-12-01

The second virial coefficient (SVC) of bounded generalizations of the Mie m:n potential ϕ (r ) =λ [1 /(aq+rq ) m /q-1 /(aq+rq ) n /q ] , where λ, a, q, m, and n are constants (a ≥ 0), is explored. The particle separation distance is r. This potential could be used as an effective interaction between polymeric dispersed colloidal particles of various degrees of interpenetrability. The SVC is negative for all temperatures for a, greater than a critical value, ac, which coincides with the range of a, where the system is thermodynamically unstable. The Boyle temperature and the temperature at which the SVC is a maximum diverge to +∞ as a → ac from below. Various series expansion expressions for the SVC are derived following on from those derived for the Mie potential itself (i.e., a = 0) in the study of Heyes et al. [J. Chem. Phys. 145, 084505 (2016)]. Formulas based on an expansion of the exponential in the Mayer function definition of the SVC are formally convergent, but pose numerical problems for the useful range of a < 1. High temperature expansion (HTE) formulas extending those in the previous publication are derived, which in contrast converge rapidly for the full a range. The HTE formulas derived in this work could be useful in guiding the choice of nucleation and growth experimental conditions for dispersed soft polymeric particles. Inter alia, the SVC of the inverse power special case of the Bounded Mie potential, i .e ., ϕ (r ) =1 /(aq+rq ) m /q, are also derived.

Interactive Sea Level Rise App & Online Viewer Offers Deep Dive Into Climate

NASA Astrophysics Data System (ADS)

Turrin, M.; Porter, D. F.; Ryan, W. B. F.; Pfirman, S. L.

2015-12-01

Climate has captured the attention of the public but its complexity can cause interested individuals to turn to opinion pieces, news articles or blogs for information. These platforms often oversimplify or present heavily interpreted or personalized perspectives. Data interactives are an extremely effective way to explore complex geoscience topics like climate, opening windows of understanding for the user that have previously been closed. Layering data onto maps through programs like GeoMapApp and the Earth Observer App has allowed users to dig directly into science data, but with only limited scaffolding. The interactive 'Polar Explorer: Sea Level Explorer App' provides a richly layered introduction to a range of topics connected to sea level rise. Each map is supported with a pop up and a short audio file of supplementary material, and an information page that includes the data source and links for further reading. This type of learning platform works well for both the formal and informal learning environment. Through science data displayed as map visualizations the user is invited into topics through an introductory question, such as "Why does sea level change?" After clicking on that question the user moves to a second layer of questions exploring the role of the ocean, the atmosphere, the contribution from the world's glaciers, world's ice sheets and other less obvious considerations such as the role of post-glacial rebound, or the mining of groundwater. Each question ends in a data map, or series of maps, that offer opportunities to interact with the topic. Under the role of the ocean 'Internal Ocean Temperature' offers the user a chance to touch to see temperature values spatially over the world's ocean, or to click through a data series starting at the ocean surface and diving to 5000 meters of depth showing how temperature changes with depth. Other sections, like the role of deglaciation of North America, allow the user to click and see change through time as the Laurentide ice sheet retreated, from 18,000 to 5,000 years ago, changing sea level as it melted. Interacting with the range of topics and the different data layers allows the user to see first hand how climate and sea level have changed through time and how it has, and does, vary around the world.

ISO Key Project: Exploring the Full Range of Quasar/AGN Properties

NASA Technical Reports Server (NTRS)

Wilkes, B.

2001-01-01

The origin of the infrared emission in Active Galactic Nuclei (AGN), whose strength is comparable to the optical/ultra-violet (OUV) emission, is generally thought to be a combination of thermal emission from dust and non-thermal, synchrotron emission. Although data are sparse, particularly in the far-infrared, the broad wavelength range of this emission suggests a wide range of temperatures and a combination of AGN and starburst heating mechanisms. The strength of the non-thermal emission is expected to be related to the radio emission. While this scenario is well-established, basic questions, such as the spatial and temperature distribution of the dust, the relative importance of AGN and starburst heating, and the significance of the non-thermal contribution, remain largely undetermined. The wide wavelength range of the Infrared Space Observatory (ISO) combined with its arcmin spatial resolution and increased sensitivity facilitated the observation of a larger subset of the AGN population than previously covered, allowing these questions to be investigated in more detail. This paper will review the spectral energy distributions (SED) of AGN with particular emphasis on the infrared emission and on ISO contributions to our knowledge. Preliminary results from ISO observations of X-ray selected and high-redshift AGN will be described.

Geothermal Resource/Reservoir Investigations Based on Heat Flow and Thermal Gradient Data for the United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. D. Blackwell; K. W. Wisian; M. C. Richards

2000-04-01

Several activities related to geothermal resources in the western United States are described in this report. A database of geothermal site-specific thermal gradient and heat flow results from individual exploration wells in the western US has been assembled. Extensive temperature gradient and heat flow exploration data from the active exploration of the 1970's and 1980's were collected, compiled, and synthesized, emphasizing previously unavailable company data. Examples of the use and applications of the database are described. The database and results are available on the world wide web. In this report numerical models are used to establish basic qualitative relationships betweenmore » structure, heat input, and permeability distribution, and the resulting geothermal system. A series of steady state, two-dimensional numerical models evaluate the effect of permeability and structural variations on an idealized, generic Basin and Range geothermal system and the results are described.« less

Modelling the Evolution of Sea Spray Droplets on a Global Scale

NASA Astrophysics Data System (ADS)

Staniec, A.; Vlahos, P.; Monahan, E. C.

2017-12-01

Sea spray droplets are an important mechanism for the transport of moisture, heat, and organic material between the ocean and the atmosphere. Spume droplets are the largest of the size spectrum and as such have the potential to transport significant amounts of energy and gases despite their generally short residence time in the atmosphere. A model is developed based on the physical parameterizations from Andreas et al. (1995, 2005)and a range of spume generation functions, coupled with a biogeochemical exchange model for gases developed here to examine the equilibrium temperature and gas exchange of spume droplets under representative open ocean conditions. The modelling approach uses micro-physics to simulate the expected changes to the droplet as it equilibrates with the atmospheric temperature and relative humidity. The effect of temperature differentials and relative humidity variations is explored. A global approach is simulated by using average summer and winter values for SST, salinity, and air temperature throughout the various ocean basins.

Complex hydrides as room-temperature solid electrolytes for rechargeable batteries

NASA Astrophysics Data System (ADS)

de Jongh, P. E.; Blanchard, D.; Matsuo, M.; Udovic, T. J.; Orimo, S.

2016-03-01

A central goal in current battery research is to increase the safety and energy density of Li-ion batteries. Electrolytes nowadays typically consist of lithium salts dissolved in organic solvents. Solid electrolytes could facilitate safer batteries with higher capacities, as they are compatible with Li-metal anodes, prevent Li dendrite formation, and eliminate risks associated with flammable organic solvents. Less than 10 years ago, LiBH4 was proposed as a solid-state electrolyte. It showed a high ionic conductivity, but only at elevated temperatures. Since then a range of other complex metal hydrides has been reported to show similar characteristics. Strategies have been developed to extend the high ionic conductivity of LiBH4 down to room temperature by partial anion substitution or nanoconfinement. The present paper reviews the recent developments in complex metal hydrides as solid electrolytes, discussing in detail LiBH4, strategies towards for fast room-temperature ionic conductors, alternative compounds, and first explorations of implementation of these electrolytes in all-solid-state batteries.

Sodium deficiency effect on the transport properties of La0.8Na0.2-x□xMnO3 manganites

NASA Astrophysics Data System (ADS)

Elghoul, N.; Wali, M.; Kraiem, S.; Rahmouni, H.; Dhahri, E.; Khirouni, K.

2015-12-01

Effect of sodium deficiency on the transport properties of La0.8Na0.2-x□xMnO3 manganites is investigated using impedance spectroscopy technique. In the whole explored temperature range (77-700 K), conductivity measurements show the appearance of a metal-semiconductor transition for all investigated samples. Also, a saturation region is observed in σ (T) curves. It is found that conduction mechanism is governed by hopping process. The conductivity of the material decreases with increasing sodium deficiency. The transition temperature and the activation energy values inferred from grain boundary resistance and conductivity analysis are closed to each other. Such result confirms the contribution of grain boundary on the electrical conductivity. The variation of the Average Normalized Change (ANC) and its derivative with temperature gives important information about the available density of trapped charge states. The obtained results explain the observed saturation region in conductivity at high temperature region.

Rheology of water-silicate mixtures at low temperatures

NASA Technical Reports Server (NTRS)

Durham, William B.

1992-01-01

Lab studies of the effects of hard particulates on the rheology of ice have been mainly directed at the evolution of the Galilean satellites, but yield results that may be applicable to the rheology of the Martian polar caps. The experiments have explored the ductile rheology as well as brittle behavior of water + particulate (mainly quartz) mixtures in particulate volume fractions ranging from 0.001 to 0.56, particulate sizes 1 to 150 microns, temperatures 77 to 224 K, and deformation rates 3.5 x 10(exp -7) to 3.5 x 10(exp -4)/s, under confining pressures of 50 to 100 MPa. Particulates act mainly to strengthen the material in the ductile field, although work by others has shown that very close to the melting temperature hard particulates can actually cause softening. So called dispersion hardening by the Orowan mechanism of pinning glide dislocations, often exploited in metallurgy for strengthening materials, appears not to be an issue in ice except at very low temperatures, less than approx. 135 K.

Dissociation of 1P states in hot QCD Medium Using Quasi-Particle Model

NASA Astrophysics Data System (ADS)

Nilima, Indrani; Agotiya, Vineet Kumar

2018-03-01

We extend the analysis of a very recent work [1] to study the dissociation phenomenon of 1P states of the charmonium and bottomonium spectra (χc and χb) in a hot QCD medium using Quasi-Particle Model. This study employed a medium modified heavy quark potential which has quite different form in the sense that it has a lomg range Coulombic tail in addition to the Yukawa term even above the deconfinement temperature. Then we study the flavor dependence of their binding energies and explore the nature of dissociation temperatures by employing the Quasi-Particle debye mass for pure gluonic and full QCD case. Interestingly, the dissociation temperatures obtained by employing EoS1 and EoS2 with the Γ criterion, is closer to the upper bound of the dissociation temperatures which are obtained by the dissolution of a given quarkonia state by the mean thermal energy of the quasi-partons in the hot QCD/QGP medium.

Hot dogs: High ambient temperatures impact reproductive success in a tropical carnivore.

PubMed

Woodroffe, Rosie; Groom, Rosemary; McNutt, J Weldon

2017-10-01

Climate change imposes an urgent need to recognise and conserve the species likely to be worst affected. However, while ecologists have mostly explored indirect effects of rising ambient temperatures on temperate and polar species, physiologists have predicted direct impacts on tropical species. The African wild dog (Lycaon pictus), a tropical species, exhibits few of the traits typically used to predict climate change vulnerability. Nevertheless, we predicted that wild dog populations might be sensitive to weather conditions, because the species shows strongly seasonal reproduction across most of its geographical range. We explored associations between weather conditions, reproductive costs, and reproductive success, drawing on long-term wild dog monitoring data from sites in Botswana (20°S, 24 years), Kenya (0°N, 12 years), and Zimbabwe (20°S, 6 years). High ambient temperatures were associated with reduced foraging time, especially during the energetically costly pup-rearing period. Across all three sites, packs which reared pups at high ambient temperatures produced fewer recruits than did those rearing pups in cooler weather; at the non-seasonal Kenya site such packs also had longer inter-birth intervals. Over time, rising ambient temperatures at the (longest-monitored) Botswana site coincided with falling wild dog recruitment. Our findings suggest a direct impact of high ambient temperatures on African wild dog demography, indicating that this species, which is already globally endangered, may be highly vulnerable to climate change. This vulnerability would have been missed by simplistic trait-based assessments, highlighting the limitations of such assessments. Seasonal reproduction, which is less common at low latitudes than at higher latitudes, might be a useful indicator of climate change vulnerability among tropical species. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

A Study of Variations in Atmospheric Turbulence Kinetic Energy on a Sandy Beach

NASA Astrophysics Data System (ADS)

Koscinski, J. S.; MacMahan, J. H.; Wang, Q.; Thornton, E. B.

2016-12-01

A 6-m high, meteorological tower consisting six evenly spaced ultrasonic anemometers and temperature-relative humidity sensors was deployed at the high tide line on sandy, wave-dissipative, meso-tidal beach in southern Monterey Bay, CA in October 2015. The micro-meteorology study focus is to explore the momentum fluxes and turbulent kinetic energy influenced by the interaction between an intensive wave-breaking surf zone and a sandy beach associated with onshore & cross-shore winds, diurnal heating, and differences in ocean-air temperatures. The tower was deployed for approximately 1-month and experienced diurnal wind variations and synoptic storm events with winds measuring up to 10 m/s and an air temperature range of 5-28 oC. This beach environment was found to be primarily unstable in thermal stratification indicating that the air temperature is colder than underlying surface, either the ocean or the sandy beach. The drag coefficient was found to be dependent upon the atmospheric stability. Direct-estimates of atmospheric stability were obtained with the sonic anemometer. The direct estimates are a ratio of w*/u*, where the w*, vertically scaled buoyancy velocity, is greater than u*, horizontally scaled friction velocity. Hypotheses for the enhanced buoyancy are 1) diurnal heating of the sandy beach, 2) warmer ocean temperatures relative to air temperatures, and 3) the wave breaking within the surf zone. Further exploration into these hypotheses is conducted by using vertical tower sensor pairs for estimating the temporal variability of the mechanical shear production and buoyancy production terms in turbulent kinetic energy budget. These results are part of the Coastal Land Air Sea Interaction (CLASI) experiment.

Conductivity in zeolite-polymer composite membranes for PEMFCs

NASA Astrophysics Data System (ADS)

Sancho, T.; Soler, J.; Pina, M. P.

Structured materials, such as zeolites can be candidates to be used as electrolytes in proton exchange membrane fuel cells (PEMFC) to substitute polymeric membranes, taking advantage of their higher chemical and thermal stability and their specific adsorption properties. The possibility to work at temperatures of nearly 150 °C would make easy the selection of the fuel, decreasing the influence of CO in the catalyst poisoning, and it would also improve the kinetics of the electrochemical reactions involved. In this work, four zeolites and related materials have been studied: mordenite, NaA zeolite, umbite and ETS-10. In special, the influence of relative humidity and temperature have been carefully explored. A conductivity cell was designed and built to measure in cross direction, by using the electrochemical impedance spectroscopy. The experimental system was validated using Nafion ® as a reference material by comparing the results with bibliography data. Samples were prepared by pressing the zeolite powders, with size of 1 μm on average, using polymer PVDF (10 wt.%) as a binder. The results here obtained, in spite of not reaching the absolute values of the Nafion ® ones, show a lower effect of the dehydration phenomenon on the conduction performance in the temperature range studied (from room temperature to 150 °C). This increase of the operation temperature range would give important advantages to the PEMFC. ETS-10 sample shows the best behaviour with respect to conductivity exhibiting an activation energy value comparable with reported for Nafion ® membrane.

AlN grown on Si(1 1 1) by ammonia-molecular beam epitaxy in the 900-1200 °C temperature range

NASA Astrophysics Data System (ADS)

Tamariz, Sebastian; Martin, Denis; Grandjean, Nicolas

2017-10-01

We present a comprehensive study of AlN growth on Si(1 1 1) substrate by gas source molecular beam epitaxy with ammonia as nitrogen precursor in the high temperature range. We first demonstrate that the observation of the silicon 7 × 7 surface reconstruction by reflection high energy electron diffraction can be misleading as this technique is not sensitive to low density surface defects like SiC crystallites. A careful in situ cleaning procedure with annealing cycles at 1100 °C allows getting rid of any surface defects, as shown by atomic force microscopy imaging. Then, we explore the effect of the growth temperature on the surface morphology and structural properties of 100 nm thick AlN epilayers. At 1200 °C, the growth proceeds with the step flow mode regime, which induces spiral-growth around screw-type dislocations and therefore surface roughening. On the other hand, a smooth surface morphology can be achieved by setting the temperature at 1100 °C, which corresponds to the growth mode transition from two-dimensional nucleation to step flow. A further decrease of the growth temperature to 900 °C leads to surface defects ascribed to polarity inversion domains. Similar defects are observed for growths performed at 1100 °C when the NH3 flow is reduced below 100 sccm. This points out the sensitivity of AlN to the surface stoichiometry.

Accounting for habitat when considering climate: has the niche of the Adonis blue butterfly changed in the UK?

PubMed

O'Connor, Rory S; Hails, Rosemary S; Thomas, Jeremy A

2014-04-01

The dramatic recovery of three species of grassland specialist butterfly threatened with extinction at their high latitude range limits in the 1980s has been attributed to two factors: increased grazing on calcareous grassland sites and warmer air temperatures. Both result in the warming of soil surface temperatures, favourable to the larvae of these species. We address the influence of both of these factors on the habitat usage of the butterfly Polyommatus bellargus, undergoing recovery at its northern range edge. We test the hypothesis that the larval niche of P. bellargus has become less constrained in the past three decades, whilst controlling for changes in habitat structure. Once habitat change has been accounted for we find no evidence for a broadening of the larval niche of P. bellargus. Further, we show that coincident with the recovery of P. bellargus there have been drastic reductions in average turf height across UK chalk grasslands, but changes in air temperature have been highly variable. We conclude that changes to soil surface temperatures caused by reducing turf heights will have been a more consistent influence than air temperature increases, and so habitat improvements through increased grazing will have been the major driver of recovery in P. bellargus. We consider the need to account for changes in habitat when exploring the impacts of recent climate change on local habitats in thermophilous species, and emphasise the continued importance of habitat management to support such species under variable local climates.

Retrievability of atmospheric water vapour, temperature and vertical windspeed profiles from proposed sub-millimetre instrument ORTIS.

NASA Astrophysics Data System (ADS)

Hurley, Jane; Irwin, Patrick; Teanby, Nicholas; de Kok, Remco; Calcutt, Simon; Irshad, Ranah; Ellison, Brian

2010-05-01

The sub-millimetre range of the spectrum has been exploited in the field of Earth observation by many instruments over the years and has provided a plethora of information on atmospheric chemistry and dynamics - however, this spectral range has not been fully explored in planetary science. To this end, a sub-millimetre instrument, the Orbiter Terahertz Infrared Spectrometer (ORTIS), is jointly proposed by the University of Oxford and the Rutherford Appleton Laboratory, to meet the requirements of the European Space Agency's Cosmic Visions Europa Jupiter System Mission (EJSM). ORTIS will consist of an infrared and a sub-millimetre component; however in this study only the sub-millimetre component will be explored. The sub-millimetre component of ORTIS is projected to measure a narrow band of frequencies centred at approximately 2.2 THz, with a spectral resolution varying between approximately 1 kHz and 1 MHz, and having an expected noise magnitude of 2 nW/cm2 sr cm-1. In this spectral region, there are strong water and methane emission lines at most altitudes on Jupiter. The sub-millimetre component of ORTIS is designed to measure the abundance of atmospheric water vapour and atmospheric temperature, as well as vertical windspeed profiles from Doppler-shifted emission lines, measured at high spectral resolution. This study will test to see if, in practice, these science objectives may be met from the planned design, as applied to Jupiter. In order to test the retrievability of atmospheric water vapour, temperature and windspeed with the proposed ORTIS design, it is necessary to have a set of "measurements' for which the input parameters (such as species' concentrations, atmospheric temperature, pressure - and windspeed) are known. This is accomplished by generating a set of radiative transfer simulations using radiative transfer model RadTrans in the spectral range sampled by ORTIS, whereby the atmospheric data pertaining to Jupiter have provided by Cassini-CIRS. These simulations are then convolved with the ORTIS field-of-view response function, yielding "measurements' of Jupiter as would be registered by ORTIS about which all atmospheric parameters are known. A standard optimal estimation retrieval code, the Non-Linear Optimal Estimator for Multivariate Spectral Analysis (NEMESIS), shall be used to retrieve atmospheric water vapour and temperature from such nadir "measurements' taken by ORTIS. The vertical windspeed profiles, as determined from Doppler-shifted emission lines taken at extremely high spectral resolution from limb (or near-limb, 80° emission angle) ORTIS "measurements', shall be determined using an implementation of standard optimal estimation theory. Preliminary analysis indicates that ORTIS should be able to retrieve atmospheric water vapour and temperature, as well as Doppler windspeed profiles on Jupiter to a high degree of accuracy over a large range of altitudes using single nadir or limb/near-limb measurements, respectively.

Understanding the Impact of Extreme Temperature on Crop Production in Karnataka in India

NASA Astrophysics Data System (ADS)

Mahato, S.; Murari, K. K.; Jayaraman, T.

2017-12-01

The impact of extreme temperature on crop yield is seldom explored in work around climate change impact on agriculture. Further, these studies are restricted mainly to crops such as wheat and maize. Since different agro-climatic zones bear different crops and cropping patterns, it is important to explore the nature of the impact of changes in climate variables in agricultural systems under differential conditions. The study explores the effects of temperature rise on the major crops paddy, jowar, ragi and tur in the state of Karnataka of southern India. The choice of the unit of study to understand impact of climate variability on crop yields is largely restricted to availability of data for the unit. While, previous studies have dealt with this issue by replacing yield with NDVI at finer resolution, the use of an index in place of yield data has its limitations and may not reflect the true estimates. For this study, the unit considered is taluk, i.e. sub-district level. The crop yield for taluk is obtained between the year the 1995 to 2011 by aggregating point yield data from crop cutting experiments for each year across the taluks. The long term temperature data shows significantly increasing trend that ranges between 0.6 to 0.75 C across Karnataka. Further, the analysis suggests a warming trend in seasonal average temperature for Kharif and Rabi seasons across districts. The study also found that many districts exhibit the tendency of occurrence of extreme temperature days, which is of particular concern in terms of crop yield, since exposure of crops to extreme temperature has negative consequences for crop production and productivity. Using growing degree days GDD, extreme degree days EDD and total season rainfall as predictor variables, the fixed effect model shows that EDD is a more influential parameter as compared to GDD and rainfall. Also it has a statistically significant negative effect in most cases. Further, quantile regression was used to evaluate the robustness of the estimates of EDD in relation to crop yield. This showed the estimates to be robust across quantiles for most of the crops studied. Thus indicating a strong negative influence of exposure to extreme temperature on crop yield in the region.

Microclimate variables of the ambient environment deliver the actual estimates of the extrinsic incubation period of Plasmodium vivax and Plasmodium falciparum: a study from a malaria-endemic urban setting, Chennai in India.

PubMed

Thomas, Shalu; Ravishankaran, Sangamithra; Justin, N A Johnson Amala; Asokan, Aswin; Kalsingh, T Maria Jusler; Mathai, Manu Thomas; Valecha, Neena; Montgomery, Jacqui; Thomas, Matthew B; Eapen, Alex

2018-05-16

Environmental factors such as temperature, relative humidity and their daily variation influence a range of mosquito life history traits and hence, malaria transmission. The standard way of characterizing environmental factors with meteorological station data need not be the actual microclimates experienced by mosquitoes within local transmission settings. A year-long study was conducted in Chennai, India to characterize local temperature and relative humidity (RH). Data loggers (Hobos) were placed in a range of probable indoor and outdoor resting sites of Anopheles stephensi. Recordings were taken hourly to estimate mean temperature and RH, together with daily temperature range (DTR) and daily relative humidity range. The temperature data were used to explore the predicted variation in extrinsic incubation period (EIP) of Plasmodium falciparum and Plasmodium vivax between microhabitats and across the year. Mean daily temperatures within the indoor settings were significantly warmer than those recorded outdoors. DTR in indoor environments was observed to be modest and ranged from 2 to 6 °C. Differences in EIP between microhabitats were most notable during the hottest summer months of April-June, with parasite development predicted to be impaired for tiled houses and overhead tanks. Overall, the prevailing warm and stable conditions suggest rapid parasite development rate regardless of where mosquitoes might rest. Taking account of seasonal and local environmental variation, the predicted EIP of P. falciparum varied from a minimum of 9.1 days to a maximum of 15.3 days, while the EIP of P. vivax varied from 8.0 to 24.3 days. This study provides a detailed picture of the actual microclimates experienced by mosquitoes in an urban slum malaria setting. The data indicate differences between microhabitats that could impact mosquito and parasite life history traits. The predicted effects for EIP are often relatively subtle, but variation between minimum and maximum EIPs can play a role in disease transmission, depending on the time of year and where mosquitoes rest. Appropriate characterization of the local microclimate conditions would be the key to fully understand the effects of environment on local transmission ecology.

Estimation of subsurface formation temperature in the Tarim Basin, northwest China: implications for hydrocarbon generation and preservation

NASA Astrophysics Data System (ADS)

Liu, Shaowen; Lei, Xiao; Feng, Changge; Hao, Chunyan

2016-07-01

Subsurface formation temperature in the Tarim Basin, northwest China, is vital for assessment of hydrocarbon generation and preservation, and of geothermal energy potential. However, it has not previously been well understood, due to poor data coverage and a lack of highly accurate temperature data. Here, we combined recently acquired steady-state temperature logging data with drill stem test temperature data and measured rock thermal properties, to investigate the geothermal regime and estimate the subsurface formation temperature at depth in the range of 1000-5000 m, together with temperatures at the lower boundary of each of four major Lower Paleozoic marine source rocks buried in this basin. Results show that heat flow of the Tarim Basin ranges between 26.2 and 66.1 mW/m2, with a mean of 42.5 ± 7.6 mW/m2; the geothermal gradient at depth of 3000 m varies from 14.9 to 30.2 °C/km, with a mean of 20.7 ± 2.9 °C/km. Formation temperature estimated at the depth of 1000 m is between 29 and 41 °C, with a mean of 35 °C, while 63-100 °C is for the temperature at the depth of 3000 m with a mean of 82 °C. Temperature at 5000 m ranges from 97 to 160 °C, with a mean of 129 °C. Generally spatial patterns of the subsurface formation temperature at depth are basically similar, characterized by higher temperatures in the uplift areas and lower temperatures in the sags, which indicates the influence of basement structure and lateral variations in thermal properties on the geotemperature field. Using temperature to identify the oil window in the source rocks, most of the uplifted areas in the basin are under favorable condition for oil generation and/or preservation, whereas the sags with thick sediments are favorable for gas generation and/or preservation. We conclude that relatively low present-day geothermal regime and large burial depth of the source rocks in the Tarim Basin are favorable for hydrocarbon generation and preservation. In addition, it is found that the oil and gas fields discovered in the Tarim Basin are usually associated with relatively high-temperature anomalies, and the upward migration and accumulation of hot geofluids along faults as conduit from below could explain this coincidence. Accordingly, this thermal anomaly could be indicative of hydrocarbon exploration targets in the basin.

High Temperature Piezoelectric Drill

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

2012-01-01

Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

Systems Modeling for Crew Core Body Temperature Prediction Postlanding

NASA Technical Reports Server (NTRS)

Cross, Cynthia; Ochoa, Dustin

2010-01-01

The Orion Crew Exploration Vehicle, NASA s latest crewed spacecraft project, presents many challenges to its designers including ensuring crew survivability during nominal and off nominal landing conditions. With a nominal water landing planned off the coast of San Clemente, California, off nominal water landings could range from the far North Atlantic Ocean to the middle of the equatorial Pacific Ocean. For all of these conditions, the vehicle must provide sufficient life support resources to ensure that the crew member s core body temperatures are maintained at a safe level prior to crew rescue. This paper will examine the natural environments, environments created inside the cabin and constraints associated with post landing operations that affect the temperature of the crew member. Models of the capsule and the crew members are examined and analysis results are compared to the requirement for safe human exposure. Further, recommendations for updated modeling techniques and operational limits are included.

Growth, Quantitative Growth Analysis, and Applications of Graphene on γ-Al2O3 catalysts

PubMed Central

Park, Jaehyun; Lee, Joohwi; Choi, Jung-Hae; Hwang, Do Kyung; Song, Yong-Won

2015-01-01

The possibilities offered by catalytic γ-Al2O3 substrates are explored, and the mechanism governing graphene formation thereon is elucidated using both numerical simulations and experiments. The growth scheme offers metal-free synthesis at low temperature, grain-size customization, large-area uniformity of electrical properties, single-step preparation of graphene/dielectric structures, and readily detachable graphene. We quantify based on thermodynamic principles the activation energies associated with graphene nucleation/growth on γ-Al2O3, verifying the low physical and chemical barriers. Importantly, we derive a universal equation governing the adsorption-based synthesis of graphene over a wide range of temperatures in both catalytic and spontaneous growth regimes. Experimental results support the equation, highlighting the catalytic function of γ-Al2O3 at low temperatures. The synthesized graphene is manually incorporated as a ‘graphene sticker’ into an ultrafast mode-locked laser. PMID:26137994

Exploring the self-mode-locked dynamics of cryogenic diode-pumped Nd:YLF lasers: switching of orthogonal polarizations

NASA Astrophysics Data System (ADS)

Huang, T. L.; Y Cho, C.; Liang, H. C.; Huang, K. F.; Chen, Y. F.

2017-08-01

The self-mode-locked output for cryogenic Nd:YLF laser at the temperature range of 90 K to 290 K is thoroughly investigated. Linearly polarized self-mode-locked lasing at 1047 nm (1053 nm) with a repetition rate up to 1.59 GHz and a pulse width as short as 52 ps can be realized at temperatures above 155 K (below 135 K). Orthogonally polarized self-mode-locked operation can be observed at temperatures near 145 K. During dual-polarization operation, it is found that the polarized component with higher output power is the fundamental transverse mode, whereas the other component with lower output power becomes the high-order transverse mode. The dominant polarized component can be either π- or σ-polarization, depending on the fine adjustment of the cavity.

Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide.

PubMed

Dankert, André; Pashaei, Parham; Kamalakar, M Venkata; Gaur, Anand P S; Sahoo, Satyaprakash; Rungger, Ivan; Narayan, Awadhesh; Dolui, Kapildeb; Hoque, Md Anamul; Patel, Ram Shanker; de Jong, Michel P; Katiyar, Ram S; Sanvito, Stefano; Dash, Saroj P

2017-06-27

The two-dimensional (2D) semiconductor molybdenum disulfide (MoS 2 ) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS 2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS 2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.

Room-temperature ferroelectricity in CuInP 2S 6 ultrathin flakes

DOE PAGES

Liu, Fucai; You, Lu; Seyler, Kyle L.; ...

2016-08-11

In this study, two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP 2S 6 (CIPS) with a transition temperature of ~320 K. Switchable polarization is observed in thin CIPS of ~4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio ofmore » ~100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.« less

Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes

PubMed Central

Liu, Fucai; You, Lu; Seyler, Kyle L.; Li, Xiaobao; Yu, Peng; Lin, Junhao; Wang, Xuewen; Zhou, Jiadong; Wang, Hong; He, Haiyong; Pantelides, Sokrates T.; Zhou, Wu; Sharma, Pradeep; Xu, Xiaodong; Ajayan, Pulickel M.; Wang, Junling; Liu, Zheng

2016-01-01

Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ∼320 K. Switchable polarization is observed in thin CIPS of ∼4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ∼100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity. PMID:27510418

Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes

NASA Astrophysics Data System (ADS)

Liu, Fucai; You, Lu; Seyler, Kyle L.; Li, Xiaobao; Yu, Peng; Lin, Junhao; Wang, Xuewen; Zhou, Jiadong; Wang, Hong; He, Haiyong; Pantelides, Sokrates T.; Zhou, Wu; Sharma, Pradeep; Xu, Xiaodong; Ajayan, Pulickel M.; Wang, Junling; Liu, Zheng

2016-08-01

Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ~320 K. Switchable polarization is observed in thin CIPS of ~4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ~100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.

Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes.

PubMed

Liu, Fucai; You, Lu; Seyler, Kyle L; Li, Xiaobao; Yu, Peng; Lin, Junhao; Wang, Xuewen; Zhou, Jiadong; Wang, Hong; He, Haiyong; Pantelides, Sokrates T; Zhou, Wu; Sharma, Pradeep; Xu, Xiaodong; Ajayan, Pulickel M; Wang, Junling; Liu, Zheng

2016-08-11

Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ∼320 K. Switchable polarization is observed in thin CIPS of ∼4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ∼100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.

Re-evaluating the northeastern Minnesota moose decline and the role of wolves

USGS Publications Warehouse

Mech, L. David; Fieberg, John

2014-01-01

We re-evaluated findings from Lenarz et al. (2009) that adult moose (Alces alces) survival in northeastern Minnesota was related to high January temperatures and that predation by wolves (Canis lupus) played a minor role. We found significant inverse relationships between annual wolf numbers in part of the moose range and various moose demographics from 2003 to 2013 that suggested a stronger role of wolves than heretofore believed. To re-evaluate the temperature findings, we conducted a simulation study, mimicking the approach taken by Lenarz et al. (2009), to explore the potential for concluding a significant relationship exists between temperature and survival, when no association exists. We found that the high R2s and low probabilities associated with the regression models in Lenarz et al. (2009) should be viewed cautiously in light of the large number of fitted models (m = 45) and few observations (n = 6 for each of 5 response variables).

One Step Combustion Synthesis Of YAG:Ce Phosphor For Solid State Lighting

NASA Astrophysics Data System (ADS)

Yadav, Pooja; Gupta, K. Vijay Kumar; Muley, Aarti; Joshi, C. P.; Moharil, S. V.

2011-10-01

YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500°C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000 C or above becomes necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500 C furnace temperature is reported here. Activation with Ce3+ could be achieved during the synthesis without taking recourse to any post-combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce3+, exhibited properties comparable to those produced from the commercial phosphor.

Holographic superconductivity from higher derivative theory

NASA Astrophysics Data System (ADS)

Wu, Jian-Pin; Liu, Peng

2017-11-01

We construct a 6 derivative holographic superconductor model in the 4-dimensional bulk spacetimes, in which the normal state describes a quantum critical (QC) phase. The phase diagram (γ1 ,Tˆc) and the condensation as the function of temperature are worked out numerically. We observe that with the decrease of the coupling parameter γ1, the critical temperature Tˆc decreases and the formation of charged scalar hair becomes harder. We also calculate the optical conductivity. An appealing characteristic is a wider extension of the superconducting energy gap, comparing with that of 4 derivative theory. It is expected that this phenomena can be observed in the real materials of high temperature superconductor. Also the Homes' law in our present models with 4 and 6 derivative corrections is explored. We find that in certain range of parameters γ and γ1, the experimentally measured value of the universal constant C in Homes' law can be obtained.

Catalytic conversion of Chlorella pyrenoidosa to biofuels in supercritical alcohols over zeolites.

PubMed

Yang, Le; Ma, Rui; Ma, Zewei; Li, Yongdan

2016-06-01

Microalgae have been considered as the feedstock for the third generation biofuels production, given its high lipid content and fast productivity. Herein, a catalytic approach for microalgae liquefaction to biocrude is examined in a temperature range of 250-300°C in methanol and ethanol over zeolites. Higher biocrude yield was achieved in ethanol and at lower temperatures, while better quality biocrude with higher light biocrude ratio and lower average molecular weight (Mw) was favored in methanol and at higher temperatures. Application of zeolites improves the biocrude quality significantly. Among the catalysts, HY shows the strongest acidity and performs the best to produce high quality biocrude. Solid residues have been extensively explored with thermal gravity analysis and elemental analysis. It is reported for the first time that up to 99wt.% of sulfur is deposited in the solid residue at 250°C for both solvents. Copyright © 2016 Elsevier Ltd. All rights reserved.

Changes in the electrical properties of pure and doped polymers under the influence of small doses of X-rays

NASA Astrophysics Data System (ADS)

Mahmoud, S. A.; Madi, N. K.; Kassem, M. E.; El-Khatib, A.

A study has been made of the temperature dependence of the d.c. conductivity of pure and borated low density polyethylene LDPE (4% and 8% borax). The above calculations were carried out before and after X-ray irradiation. The irradiation dose was varied from 0 to 1000 rad. The d.c. electrical conductivity of Polyvinyl chloride (PVC) and perspex was measured as a function of temperature ranging from 20°C to 100°C. These samples were irradiated with X-rays of dose 200 rad. The variation of the d.c. conductivity of the treated samples versus temperature was investigated. The results reveal that the d.c. conductivity of LDPE is highly affected by radiation and/or dopant. In addition, the sensitivity of the explored polymers to X-ray irradiation is strongly dependent on its chemical nature.

Effect of cobalt doping on the structural, magnetic and abnormal thermal expansion properties of NaZn13-type La(Fe1-xCox)11.4Al1.6 compounds.

PubMed

Zhao, Yuqiang; Huang, Rongjin; Li, Shaopeng; Wang, Wei; Jiang, Xingxing; Lin, Zheshuai; Li, Jiangtao; Li, Laifeng

2016-07-27

Cubic NaZn13-type La(Fe1-xCox)11.4Al1.6 compounds were synthesized and extensively explored through crystal structure and magnetization analyses. By optimizing the chemical composition, the isotropic abnormal properties of excellent zero and giant negative thermal expansion in a pure form were both found at different temperature ranges through room temperature. Moreover, the temperature regions with the remarkable abnormal thermal expansion (ATE) properties have been broadened which are controlled by the dM/dT. The present study demonstrates that the ATE behavior mainly depends on special structural and magnetic properties. These diverse properties suggest the high potential of La(Fe1-xCox)11.4Al1.6 for the development of abnormal expansion materials.

Low-Temperature Crystal Structures of the Hard Core Square Shoulder Model.

PubMed

Gabriëlse, Alexander; Löwen, Hartmut; Smallenburg, Frank

2017-11-07

In many cases, the stability of complex structures in colloidal systems is enhanced by a competition between different length scales. Inspired by recent experiments on nanoparticles coated with polymers, we use Monte Carlo simulations to explore the types of crystal structures that can form in a simple hard-core square shoulder model that explicitly incorporates two favored distances between the particles. To this end, we combine Monte Carlo-based crystal structure finding algorithms with free energies obtained using a mean-field cell theory approach, and draw phase diagrams for two different values of the square shoulder width as a function of the density and temperature. Moreover, we map out the zero-temperature phase diagram for a broad range of shoulder widths. Our results show the stability of a rich variety of crystal phases, such as body-centered orthogonal (BCO) lattices not previously considered for the square shoulder model.

Helicon plasma ion temperature measurements and observed ion cyclotron heating in proto-MPEX

NASA Astrophysics Data System (ADS)

Beers, C. J.; Goulding, R. H.; Isler, R. C.; Martin, E. H.; Biewer, T. M.; Caneses, J. F.; Caughman, J. B. O.; Kafle, N.; Rapp, J.

2018-01-01

The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) linear plasma device is a test bed for exploring and developing plasma source concepts to be employed in the future steady-state linear device Material Plasma Exposure eXperiment (MPEX) that will study plasma-material interactions for the nuclear fusion program. The concept foresees using a helicon plasma source supplemented with electron and ion heating systems to reach necessary plasma conditions. In this paper, we discuss ion temperature measurements obtained from Doppler broadening of spectral lines from argon ion test particles. Plasmas produced with helicon heating alone have average ion temperatures downstream of the Helicon antenna in the range of 3 ± 1 eV; ion temperature increases to 10 ± 3 eV are observed with the addition of ion cyclotron heating (ICH). The temperatures are higher at the edge than the center of the plasma either with or without ICH. This type of profile is observed with electrons as well. A one-dimensional RF antenna model is used to show where heating of the plasma is expected.

Sensitivities of seismic velocities to temperature, pressure and composition in the lower mantle

NASA Astrophysics Data System (ADS)

Trampert, Jeannot; Vacher, Pierre; Vlaar, Nico

2001-08-01

We calculated temperature, pressure and compositional sensitivities of seismic velocities in the lower mantle using latest mineral physics data. The compositional variable refers to the volume proportion of perovskite in a simplified perovskite-magnesiowüstite mantle assemblage. The novelty of our approach is the exploration of a reasonable range of input parameters which enter the lower mantle extrapolations. This leads to realistic error bars on the sensitivities. Temperature variations can be inferred throughout the lower mantle within a good degree of precision. Contrary to the uppermost mantle, modest compositional changes in the lower mantle can be detected by seismic tomography, with a larger uncertainty though. A likely trade-off between temperature and composition will be largely determined by uncertainties in tomography itself. Given current sources of uncertainties on recent data, anelastic contributions to the temperature sensitivities (calculated using Karato's approach) appear less significant than previously thought. Recent seismological determinations of the ratio of relative S to P velocity heterogeneity can be entirely explain by thermal effects, although isolated spots beneath Africa and the Central Pacific in the lowermost mantle may ask for a compositional origin.

PREFACE: VI Scientific Technical Conference on "Low-temperature plasma during the deposition of functional coatings"

NASA Astrophysics Data System (ADS)

2014-11-01

The VI Republican Scientific Technical Conference "Low-temperature plasma during the deposition of functional coatings" took place from 4 to 7 November 2014 at the Academy of Sciences of the Republic of Tatarstan and the Kazan Federal University. The conference was chaired by a Member of the Academy of Sciences of the Republic of Tatarstan Nail Kashapov -Professor, Doctor of Technical Sciences- a member of the Scientific and Technical Council of the Ministry of Economy of the Republic of Tatarstan. At the conference, the participants discussed a wide range of issues affecting the theoretical and computational aspects of research problems in the physics and technology of low-temperature plasma. A series of works were devoted to the study of thin films obtained by low-temperature plasma. This year work dedicated to the related field of heat mass transfer in multiphase media and low-temperature plasma was also presented. Of special interest were reports on the exploration of gas discharges with liquid electrolytic electrotrodes and the study of dusty plasmas. Kashapov Nail, D.Sc., Professor (Kazan Federal University)

A new fundamental bioheat equation for muscle tissue--part II: Temperature of SAV vessels.

PubMed

Zhu, Liang; Xu, Lisa X; He, Qinghong; Weinbaum, Sheldon

2002-02-01

In this study, a new theoretical framework was developed to investigate temperature variations along countercurrent SAV blood vessels from 300 to 1000 microm diameter in skeletal muscle. Vessels of this size lie outside the range of validity of the Weinbaum-Jiji bioheat equation and, heretofore, have been treated using discrete numerical methods. A new tissue cylinder surrounding these vessel pairs is defined based on vascular anatomy, Murray's law, and the assumption of uniform perfusion. The thermal interaction between the blood vessel pair and surrounding tissue is investigated for two vascular branching patterns, pure branching and pure perfusion. It is shown that temperature variations along these large vessel pairs strongly depend on the branching pattern and the local blood perfusion rate. The arterial supply temperature in different vessel generations was evaluated to estimate the arterial inlet temperature in the modified perfusion source term for the s vessels in Part I of this study. In addition, results from the current research enable one to explore the relative contribution of the SAV vessels and the s vessels to the overall thermal equilibration between blood and tissue.

PREFACE: VII Conference on Low Temperature Plasma in the Processes of Functional Coating Preparation

NASA Astrophysics Data System (ADS)

Nail, Kashapov

2016-01-01

The VII All-Russian (with international participation) Scientific Technical Conference "Low-temperature plasma during the deposition of functional coatings" took place from 4-7 November 2015 at the Academy of Sciences of the Republic of Tatarstan and the Kazan Federal University. The conference was attended by over 150 people from Russia and abroad. The participants proposed a wide range of issues affecting the theoretical and experimental aspects of the problems of the physics of low-temperature plasma. We heard the reports of experts from leading universities and research organizations in the field of plasma physics: Moscow State University, St. Petersburg State University, MEPhI, Tomsk Polytechnic University, Institute of High Current Electronics SB RAS, etc. A series of works were devoted to the study of thin films obtained by low-temperature plasma. This year, work dedicated to the related field of heat mass transfer in multiphase media and low-temperature plasma was also presented. Of special interest were reports on the exploration of gas discharges with liquid electrolytic electrodes and the study of dusty plasmas. Kashapov Nail, D.Sc., professor (Kazan Federal University)

Materials for Slack Diaphragms

NASA Technical Reports Server (NTRS)

Puschmann, Traute

1940-01-01

This report deals with systematic experiments carried out on five diaphragm materials with different pretreatment, for the purpose of ascertaining the suitability of such materials for slack diaphragms. The relationship of deflection and load, temperature and moisture, was recorded. Of the explored materials, synthetic leather, balloon cloth, goldbeaters skin, Igelit and Buna, synthetic leather treated with castor oil is the most suitable material for the small pressure range required. Balloon cloth is nearly as good, while goldbeaters skin, Igelit and Buna were found to be below the required standards.

Modeling of thermal coupling in VO2-based oscillatory neural networks

NASA Astrophysics Data System (ADS)

Velichko, Andrey; Belyaev, Maksim; Putrolaynen, Vadim; Perminov, Valentin; Pergament, Alexander

2018-01-01

In this study, we have demonstrated the possibility of using the thermal coupling to control the dynamics of operation of coupled VO2 oscillators. Based on the example of a 'switch-microheater' pair, we have explored the synchronization and dissynchronization modes of a single oscillator with respect to an external harmonic heat impact. The features of changes in the spectra are shown, in particular, the effect of the natural frequency attraction to the affecting signal frequency and the self-oscillation noise reduction effects at synchronization. The time constant of the temperature effect for the considered system configuration is in the range 7-140 μs, which allows operation in the oscillation frequency range of up to ∼70 kHz. A model estimate of the minimum temperature sensitivity of the switch is δTswitch ∼ 0.2 K, and the effective action radius RTC of the switch-to-switch thermal coupling is not less than 25 μm. Nevertheless, as the simulation shows, the frequency range can be significantly extended up to the values of 1-30 GHz if using nanometer-scale switches (heaters).

Reconstructing thermal properties of firn at Summit, Greenland from a temperature profile

NASA Astrophysics Data System (ADS)

Giese, A. L.; Hawley, R. L.

2013-12-01

Thermodynamic properties of firn are important factors when considering energy balance and temperature-dependent physical processes in the near-surface of glaciers. Of particular interest is thermal diffusivity, which can take a range of values and which governs both the temperature gradient and its evolution through time. Given that temperature is a well-established driver of firn densification, a better understanding of heat transfer will permit greater accuracy in the compaction models essential for interpreting inter-annual and seasonal ice surface elevation changes detected by airborne and satellite altimetry. Due to its dependence on microstructure, diffusivity can vary significantly by location. Rather than directly measuring diffusivity or one of its proxies (e.g. density, hardness, shear strength), this study inverts the heat equation to reconstruct diffusivity values. This is a less logistically-intensive approach which circumvents many of the challenges associated with imperfect proxies and snow metamorphism during measurement. Hourly records (May 2004 - July 2008) from 8 thermistors placed in the top 10 m at Summit, Greenland provide temperature values for Summit's firn, which is broadly representative of firn across the ice sheet's dry snow zone. In this study, we use both physical analysis and a finite-difference numerical model to determine a diffusivity magnitude and gradient; we find that diffusivity of Summit firn falls in the lower end of the range expected from local density and temperature conditions alone (i.e. 15 - 36 m^2/a for firn at -30C). Further, we assess the utility of our modeling approach, explore the validity of assuming bulk conductive heat transfer when modeling temperature changes in non-homogeneous firn, and investigate the implications of a low-end diffusivity value for surface compaction modeling in Greenland.

Impact of Rice Paddy Areas Decrease on Local Climate over Taiwan

NASA Astrophysics Data System (ADS)

Lo, M. H.; Wen, W. H.; Chen, C. C.

2014-12-01

Agricultural irrigation practice is one of the important anthropogenic processes in the land surface modeling. Irrigation can decrease local surface temperature with alternating surface energy partitioning. Rice paddy is the major food crop in Asian monsoon region and rice is grown under flooded conditions during the growing season; hence, the rice paddy can be considered as an open water body, which has more impacts on the surface energy budget than other cropland does. In this study, we explore how the rice paddy area changes affect Taiwan's regional climate from both observational data and numerical modeling exercise. The Weather Research and Forecasting (WRF) model is utilized to explore impacts of rice paddy area changes on the regional climate, and energy and water budget changes. In addition, temperature datasets from six automatic weather stations in the northern Taiwan and two stations in the southern Taiwan are analyzed in this study to explore how the Daily Temperature Range (DTR) changes with the decreased rice paddy areas. Previous studies show that due to the urban heat island effect, aerosol direct and indirect effects, and global warming, the DTR has decreased in the past 4 decades observed from most of the weather stations around Taiwan. However, the declined rice paddy area may increase the DTR with higher Bowen ratio during the daytime. Preliminary results show that DTR is decreased in weather stations near the urban area, but increased in weather stations near fallow areas in the past 20 years. It shows that different land use changes may have opposite impacts on local and regional climate.

Assessment of Geothermal Resource Potential at a High-Priority Area on the Utah Testing and Training Range–South (UTTR–S)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richard P. Smith, PhD., PG; Robert P. Breckenridge, PhD.; Thomas R. Wood, PhD.

2012-04-01

Field investigations conducted during 2011 support and expand the conclusion of the original Preliminary Report that discovery of a viable geothermal system is possible in the northwestern part of the Utah Testing and Training Range-South (UTTR-S), referred to henceforth as Focus Area 1. The investigations defined the southward extent of the Wendover graben into and near Focus Area 1, enhanced the understanding of subsurface conditions, and focused further geothermal exploration efforts towards the northwestern-most part of Focus Area 1. Specifically, the detailed gravity survey shows that the Wendover graben, first defined by Cook et al. (1964) for areas north ofmore » Interstate Highway 80, extends and deepens southwest-ward to the northwest corner of Focus Area 1. At its deepest point, the intersection with a northwest-trending graben there is favorable for enhanced permeability associated with intersecting faults. Processing and modeling of the gravity data collected during 2011 provide a good understanding of graben depth and distribution of faults bounding the graben and has focused the interest area of the study. Down-hole logging of temperatures in wells made available near the Intrepid, Inc., evaporation ponds, just north of Focus Area 1, provide a good understanding of the variability of thermal gradients in that area and corroborate the more extensive temperature data reported by Turk (1973) for the depth range of 300-500 m. Moderate temperature gradients in the northern part of the Intrepid area increase to much higher gradients and bottom-hole temperatures southeastward, towards graben-bounding faults, suggesting upwelling geothermal waters along those faults. Water sampling, analysis, and temperature measurements of Blue Lakes and Mosquito Willey's springs, on the western boundary of Focus Area 1, also show elevated temperatures along the graben-bounding fault system. In addition, water chemistry suggests origin of those waters in limestone rocks beneath the graben in areas with temperatures as high as 140 C (284 F). In conclusion, all of the field data collected during 2011 and documented in the Appendices of this report indicate that there is reasonable potential for a viable geothermal resource along faults that bound the Wendover graben. Prospects for a system capable of binary electrical generation are especially good, and the possibility of a flash steam system is also within reason. The next steps should focus on securing the necessary funding for detailed geophysical surveys and for drilling a set of temperature gradient wells to further evaluate the resource, and to focus deep exploration efforts in the most promising areas.« less

A newly developed tool for intra-tracheal temperature and humidity assessment in laryngectomized individuals: the Airway Climate Explorer (ACE)

PubMed Central

Zuur, J. K.; Muller, S. H.; de Jongh, F. H. C.; van der Horst, M. J.; Shehata, M.; van Leeuwen, J.; Sinaasappel, M.

2007-01-01

The aim of this study is to develop a postlaryngectomy airway climate explorer (ACE) for assessment of intratracheal temperature and humidity and of influence of heat and moisture exchangers (HMEs). Engineering goals were within-device condensation prevention and fast response time characteristics. The ACE consists of a small diameter, heated air-sampling catheter connected to a heated sensor house, containing a humidity sensor. Air is sucked through the catheter by a controlled-flow pump. Validation was performed in a climate chamber using a calibrated reference sensor and in a two-flow system. Additionally, the analyser was tested in vivo. Over the clinically relevant range of humidity values (5–42 mg H2O/l air) the sensor output highly correlates with the reference sensor readings (R2 > 0.99). The 1–1/e response times are all <0.5 s. A first in vivo pilot measurement was successful. The newly developed, verified, fast-responding ACE is suitable for postlaryngectomy airway climate assessment. PMID:17629761

Probing condensed matter physics with magnetometry based on nitrogen-vacancy centres in diamond

NASA Astrophysics Data System (ADS)

Casola, Francesco; van der Sar, Toeno; Yacoby, Amir

2018-01-01

The magnetic fields generated by spins and currents provide a unique window into the physics of correlated-electron materials and devices. First proposed only a decade ago, magnetometry based on the electron spin of nitrogen-vacancy (NV) defects in diamond is emerging as a platform that is excellently suited for probing condensed matter systems; it can be operated from cryogenic temperatures to above room temperature, has a dynamic range spanning from direct current to gigahertz and allows sensor-sample distances as small as a few nanometres. As such, NV magnetometry provides access to static and dynamic magnetic and electronic phenomena with nanoscale spatial resolution. Pioneering work has focused on proof-of-principle demonstrations of its nanoscale imaging resolution and magnetic field sensitivity. Now, experiments are starting to probe the correlated-electron physics of magnets and superconductors and to explore the current distributions in low-dimensional materials. In this Review, we discuss the application of NV magnetometry to the exploration of condensed matter physics, focusing on its use to study static and dynamic magnetic textures and static and dynamic current distributions.

2006 NASA Seal/Secondary Air System Workshop; Volume 1

NASA Technical Reports Server (NTRS)

Steinetz, Bruce, M. (Editor); Hendricks, Robert C. (Editor); Delgado, Irebert (Editor)

2007-01-01

The 2006 NASA Seal/Secondary Air System workshop covered the following topics: (i) Overview of NASA s new Exploration Initiative program aimed at exploring the Moon, Mars, and beyond; (ii) Overview of NASA s new fundamental aeronautics technology project; (iii) Overview of NASA Glenn Research Center s seal project aimed at developing advanced seals for NASA s turbomachinery, space, and reentry vehicle needs; (iv) Reviews of NASA prime contractor, vendor, and university advanced sealing concepts including tip clearance control, test results, experimental facilities, and numerical predictions; and (v) Reviews of material development programs relevant to advanced seals development. Turbine engine studies have shown that reducing seal leakages as well as high-pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin, and increase range. Several organizations presented development efforts aimed at developing faster clearance control systems and associated technology to meet future engine needs. The workshop also covered several programs NASA is funding to develop technologies for the Exploration Initiative and advanced reusable space vehicle technologies. NASA plans on developing an advanced docking and berthing system that would permit any vehicle to dock to any on-orbit station or vehicle. Seal technical challenges (including space environments, temperature variation, and seal-on-seal operation) as well as plans to develop the necessary "androgynous" seal technologies were reviewed. Researchers also reviewed seal technologies employed by the Apollo command module that serve as an excellent basis for seals for NASA s new Crew Exploration Vehicle (CEV).

Variations in stable hydrogen and oxygen isotopes in atmospheric water vapor in the marine boundary layer across a wide latitude range.

PubMed

Liu, Jingfeng; Xiao, Cunde; Ding, Minghu; Ren, Jiawen

2014-11-01

The newly-developed cavity ring-down laser absorption spectroscopy analyzer with special calibration protocols has enabled the direct measurement of atmospheric vapor isotopes at high spatial and temporal resolution. This paper presents real-time hydrogen and oxygen stable isotope data for atmospheric water vapor above the sea surface, over a wide range of latitudes spanning from 38°N to 69°S. Our results showed relatively higher values of δ(18)O and δ(2)H in the subtropical regions than those in the tropical and high latitude regions, and also a notable decreasing trend in the Antarctic coastal region. By combining the hydrogen and oxygen isotope data with meteoric water line and backward trajectory model analysis, we explored the kinetic fractionation caused by subsiding air masses and related saturated vapor pressure in the subtropics, and the evaporation-driven kinetic fractionation in the Antarctic region. Simultaneous observations of meteorological and marine variables were used to interpret the isotopic composition characteristics and influential factors, indicating that d-excess is negatively correlated with humidity across a wide range of latitudes and weather conditions worldwide. Coincident with previous studies, d-excess is also positively correlated with sea surface temperature and air temperature (Tair), with greater sensitivity to Tair. Thus, atmospheric vapor isotopes measured with high accuracy and good spatial-temporal resolution could act as informative tracers for exploring the water cycle at different regional scales. Such monitoring efforts should be undertaken over a longer time period and in different regions of the world. Copyright © 2014. Published by Elsevier B.V.

Characteristics of Trailer Thermal Environment during Commercial Swine Transport Managed under U.S. Industry Guidelines

PubMed Central

Xiong, Yijie; Green, Angela; Gates, Richard S.

2015-01-01

Simple Summary Temperature and thermal conditions of the interior of a swine trailer during transport were monitored over a broad range of outdoor conditions (34 trips total) managed according to industry best practice (Transport Quality Assurance (TQA) guidelines (NPB, 2008)). For the outdoor temperature range of 5 °C (40 °F) to 27 °C (80 °F), generally acceptable trailer thermal conditions were observed according to the TQA. Beyond this outdoor temperature range, undesirable conditions within the trailer were prevalent. Areas for potential improvement in transport management were identified. Stops resulted in rapid increases in temperature, which could be beneficial during cooler outdoor temperatures, but detrimental for warmer outdoor temperatures. Abstract Transport is a critical factor in modern pork production and can seriously affect swine welfare. While previous research has explored thermal conditions during transport, the impact of extreme weather conditions on the trailer thermal environment under industry practices has not been well documented; and the critical factors impacting microclimate are not well understood. To assess the trailer microclimate during transport events, an instrumentation system was designed and installed at the central ceiling level, pig level and floor-level in each of six zones inside a commercial swine trailer. Transport environmental data from 34 monitoring trips (approximately 1–4 h in duration each) were collected from May, 2012, to February, 2013, with trailer management corresponding to the National Pork Board Transport Quality Assurance (TQA) guidelines in 31 of these trips. According to the TQA guidelines, for outdoor temperature ranging from 5 °C (40 °F) to 27 °C (80 °F), acceptable thermal conditions were observed based on the criteria that no more than 10% of the trip duration was above 35 °C (95 °F) or below 0 °C (32 °F). Recommended bedding, boarding and water application were sufficient in this range. Measurements support relaxing boarding guidelines for moderate outdoor conditions, as this did not result in less desirable conditions. Pigs experienced extended undesirable thermal conditions for outdoor temperatures above 27 °C (80 °F) or below 5 °C (40 °F), meriting a recommendation for further assessment of bedding, boarding and water application guidelines for extreme outdoor temperatures. An Emergency Livestock Weather Safety Index (LWSI) condition was observed inside the trailer when outdoor temperature exceeded 10 °C (50 °F); although the validity of LWSI to indicate heat stress for pigs during transport is not well established. Extreme pig surface temperatures in the rear and middle zones of the trailer were more frequently experienced than in the front zones, and the few observations of pigs dead or down upon arrival were noted in these zones. Observations indicate that arranging boarding placement may alter the ventilation patterns inside the trailer. PMID:26479232

Incubation temperature influences trade-off between structural size and energy reserves in mallard hatchlings.

PubMed

Koláčková, Martina; Prokůpková, Ludmila; Albrecht, Tomáš; Hořák, David

2015-01-01

The reproductive success of precocial birds depends on investments in clutch formation and incubation. Egg quality strongly affects the phenotypic traits correlated with survival of the hatchling, but parental ability to maintain incubation temperature can also influence hatchling outcomes. The effect of incubation temperature on hatchling phenotype has been widely studied in reptiles but not in birds. The aim of this study was to explore the effects of egg mass and incubation temperature on the incubation period, hatchability, and hatchling phenotype of the mallard (Anas platyrhynchos). Mallard eggs were incubated under six constant incubation temperatures (ranging from 35.0° to 39.0°C). Hatchlings were weighed, and their structural size was measured. Some hatchlings were used for an examination of residual yolk sac mass and basic chemical composition of the yolk-free body. All investigated phenotypic traits except for chemical composition were positively correlated with egg mass. Incubation temperature did not affect hatchling body mass, but increased temperatures led to a decreased yolk-free body mass and structural size of hatchlings and to increased yolk sac mass. Our results suggest that there is a trade-off between the yolk-free body size and energetic reserves in the form of the yolk sac and that this trade-off is modulated by incubation temperature.

Temperature-dependent electrical characteristics and carrier transport mechanism of p-Cu2ZnSnS4/n-GaN heterojunctions

NASA Astrophysics Data System (ADS)

Niteesh Reddy, Varra; Reddy, M. Siva Pratap; Gunasekhar, K. R.; Lee, Jung-Hee

2018-04-01

This work explores the temperature-dependent electrical characteristics and carrier transport mechanism of Au/p-Cu2ZnSnS4/n-type GaN heterojunction (HJ) diodes with a CZTS interlayer. The electrical characteristics were examined by current-voltage-temperature, turn-on voltage-temperature and series resistance-temperature in the high-temperature range of 300-420 K. It is observed that an exponential decrease in the series resistance ( R S) and increase in the ideality factor ( n) and barrier height ( ϕ b) with increase in temperature. The thermal coefficient ( K j) is determined to be - 1.3 mV K-1 at ≥ 300 K. The effective ϕ b is determined to be 1.21 eV. This obtained barrier height is consistent with the theoretical one. The characteristic temperature ( T 0) resulting from the Cheung's functions [d V/d(ln I) vs. I and H( I) vs. I], is seen that there is good agreement between the T 0 values from both Cheung's functions. The relevant carrier transport mechanisms of Au/p-CZTS/n-type GaN HJ are explained based on the thermally decreased energy band gap of n-type GaN layers, thermally activated deep donors and increased further activated shallow donors.

Temperature-controlled optical stimulation of the rat prostate cavernous nerves

NASA Astrophysics Data System (ADS)

Tozburun, Serhat; Hutchens, Thomas C.; McClain, Michael A.; Lagoda, Gwen A.; Burnett, Arthur L.; Fried, Nathaniel M.

2013-06-01

Optical nerve stimulation (ONS) may be useful as a diagnostic tool for intraoperative identification and preservation of the prostate cavernous nerves (CN), responsible for erectile function, during prostate cancer surgery. Successful ONS requires elevating the nerve temperature to within a narrow range (˜42 to 47°C) for nerve activation without thermal damage to the nerve. This preliminary study explores a prototype temperature-controlled optical nerve stimulation (TC-ONS) system for maintaining a constant (±1°C) nerve temperature during short-term ONS of the rat prostate CNs. A 150-mW, 1455-nm diode laser was operated in continuous-wave mode, with and without temperature control, during stimulation of the rat CNs for 15 to 30 s through a fiber optic probe with a 1-mm-diameter spot. A microcontroller opened and closed an in-line mechanical shutter in response to an infrared sensor, with a predetermined temperature set point. With TC-ONS, higher laser power settings were used to rapidly and safely elevate the CNs to a temperature necessary for a fast intracavernous pressure response, while also preventing excessive temperatures that would otherwise cause thermal damage to the nerve. With further development, TC-ONS may provide a rapid, stable, and safe method for intraoperative identification and preservation of the prostate CNs.

Plasmaspheric H+, He+, O+, He++, and O++ Densities and Temperatures

NASA Technical Reports Server (NTRS)

Gallagher, D. L.; Craven, P. D.; Comfort H.

2013-01-01

Thermal plasmaspheric densities and temperatures for five ion species have recently become available, even though these quantities were derived some time ago from the Retarding Ion Mass Spectrometer onboard the Dynamics Explorer 1 satellite over the years 1981-1984. The quantitative properties will be presented. Densities are found to have one behavior with lessor statistical variation below about L=2 and another with much greater variability above that Lshell. Temperatures also have a behavior difference between low and higher L-values. The density ratio He++/H+ is the best behaved with values of about 0.2% that slightly increase with increasing L. Unlike the He+/H+ density ratio that on average decreases with increasing Lvalue, the O+/H+ and O++/H+ density ratios have decreasing values below about L=2 and increasing average ratios at higher L-values. Hydrogen ion temperatures range from about 0.2 eV to several 10s of eV for a few measurements, although the bulk of the observations are of temperatures below 3 eV, again increasing with L-value. The temperature ratios of He+/H+ are tightly ordered around 1.0 except for the middle plasmasphere between L=3.5 and 4.5 where He+ temperatures can be significantly higher. The temperatures of He++, O+, and O++ are consistently higher than H+.

Plasmaspheric H+, He+, He++, O+, and O++ Densities and Temperatures

NASA Technical Reports Server (NTRS)

Gallagher, G. L.; Craven, P. D.; Comfort, R. H.

2013-01-01

Thermal plasmaspheric densities and temperatures for five ion species have recently become available, even though these quantities were derived some time ago from the Retarding Ion Mass Spectrometer onboard the Dynamics Explorer 1 satellite over the years 1981-1984. The quantitative properties will be presented. Densities are found to have one behavior with lessor statistical variation below about L=2 and another with much greater variability above that Lshell. Temperatures also have a behavior difference between low and higher L-values. The density ratio He++/H+ is the best behaved with values of about 0.2% that slightly increase with increasing L. Unlike the He+/H+ density ratio that on average decreases with increasing Lvalue, the O+/H+ and O++/H+ density ratios have decreasing values below about L=2 and increasing average ratios at higher L-values. Hydrogen ion temperatures range from about 0.2 eV to several 10s of eV for a few measurements, although the bulk of the observations are of temperatures below 3 eV, again increasing with L-value. The temperature ratios of He+/H+ are tightly ordered around 1.0 except for the middle plasmasphere between L=3.5 and 4.5 where He+ temperatures can be significantly higher. The temperatures of He++, O+, and O++ are consistently higher than H+.

Time-dependent compressibility of poly (methyl methacrylate) (PMMA) : an experimental and molecular dynamics investigation

NASA Astrophysics Data System (ADS)

Sane, Sandeep Bhalchandra

This thesis contains three chapters, which describe different aspects of an investigation of the bulk response of Poly(Methyl Methacrylate) (PMMA). The first chapter describes the physical measurements by means of a Belcher/McKinney-type apparatus. Used earlier for the measurement of the bulk response of Poly(Vinyl Acetate), it was now adapted for making measurements at higher temperatures commensurate with the glass transition temperature of PMMA. The dynamic bulk compliance of PMMA was measured at atmospheric pressure over a wide range of temperatures and frequencies, from which the master curves for the bulk compliance were generated by means of the time-temperature superposition principle. It was found that the extent of the transition ranges for the bulk and shear response were comparable. Comparison of the shift factors for bulk and shear responses supports the idea that different molecular mechanisms contribute to shear and bulk deformations. The second chapter delineates molecular dynamics computations for the bulk response for a range of pressures and temperatures. The model(s) consisted of 2256 atoms formed into three polymer chains with fifty monomer units per chain per unit cell. The time scales accessed were limited to tens of pico seconds. It was found that, in addition to the typical energy minimization and temperature annealing cycles for establishing equilibrium models, it is advantageous to subject the model samples to a cycle of relatively large pressures (GPa-range) for improving the equilibrium state. On comparing the computations with the experimentally determined "glassy" behavior, one finds that, although the computations were limited to small samples in a physical sense, the primary limitation rests in the very short times (pico seconds). The molecular dynamics computations do not model the physically observed temperature sensitivity of PMMA, even if one employs a hypothetical time-temperature shift to account for the large difference in time scales between experiment and computation. The values computed by the molecular dynamics method do agree with the values measured at the coldest temperature and at the highest frequency of one kiloHertz. The third chapter draws on measurements of uniaxial, shear and Poisson response conducted previously in our laboratory. With the availability of four time or frequency-dependent material functions for the same material, the process of interconversion between different material functions was investigated. Computed material functions were evaluated against the direct experimental measurements and the limitations imposed on successful interconversion due to the experimental errors in the underlying physical data were explored. Differences were observed that are larger than the experimental errors would suggest.

Climate change and health: Indoor heat exposure in vulnerable populations

DOE Office of Scientific and Technical Information (OSTI.GOV)

White-Newsome, Jalonne L., E-mail: jalonne@umich.edu; Sanchez, Brisa N., E-mail: brisa@umich.edu; Jolliet, Olivier, E-mail: ojolliet@umich.edu

2012-01-15

Introduction: Climate change is increasing the frequency of heat waves and hot weather in many urban environments. Older people are more vulnerable to heat exposure but spend most of their time indoors. Few published studies have addressed indoor heat exposure in residences occupied by an elderly population. The purpose of this study is to explore the relationship between outdoor and indoor temperatures in homes occupied by the elderly and determine other predictors of indoor temperature. Materials and methods: We collected hourly indoor temperature measurements of 30 different homes; outdoor temperature, dewpoint temperature, and solar radiation data during summer 2009 inmore » Detroit, MI. We used mixed linear regression to model indoor temperatures' responsiveness to weather, housing and environmental characteristics, and evaluated our ability to predict indoor heat exposures based on outdoor conditions. Results: Average maximum indoor temperature for all locations was 34.85 Degree-Sign C, 13.8 Degree-Sign C higher than average maximum outdoor temperature. Indoor temperatures of single family homes constructed of vinyl paneling or wood siding were more sensitive than brick homes to outdoor temperature changes and internal heat gains. Outdoor temperature, solar radiation, and dewpoint temperature predicted 38% of the variability of indoor temperatures. Conclusions: Indoor exposures to heat in Detroit exceed the comfort range among elderly occupants, and can be predicted using outdoor temperatures, characteristics of the housing stock and surroundings to improve heat exposure assessment for epidemiological investigations. Weatherizing homes and modifying home surroundings could mitigate indoor heat exposure among the elderly.« less

Speed of Sound in Aqueous Solutions at sub-GPa Pressures: a New Experiment to Unveil the Properties of Extra-Terrestrial Oceans

NASA Astrophysics Data System (ADS)

Bollengier, O.; Brown, J. M.; Vance, S.; Shaw, G. H.

2015-12-01

Geophysical data from the Galileo and Cassini-Huygens missions are consistent with the presence of aqueous subsurface oceans in Ganymede, Callisto and Titan, the largest icy satellites of the solar system. To understand the history and present state of these moons, the next generation of evolution models will require an accurate description of the properties of these liquid layers to predict the phase boundaries, heat transports and chemical exchanges within them. Sound speed measurements in pressure and temperature allow for the reconstruction of the Gibbs free energy surface of a phase, which in turn gives access to the desired properties (chemical potential, density, heat capacity...). However, such data are still scarce for aqueous solutions bearing Na+, Mg2+, Cl- and SO42- ions (major ions expected in extra-terrestrial oceans) at the high pressures and low temperatures expected for water inside these moons (up to 1.5 GPa for Ganymede, down to freezing temperatures). For pure water, IAPWS accuracy for sound speeds is given to 0.3% above 0.4 GPa. MgSO4aqueous solutions have been explored to 0.7 GPa with a precision limited to about 0.5%. Most other aqueous solutions bearing any combination of these four ions have not been explored at all above a few hundreds MPa. To acquire new high-precision sound speeds in aqueous solutions of various compositions, we set up a new experimental system working in the 0 - 0.7 GPa pressure range and 240 - 350 K temperature range. The device consists in an oil-pressurized steel vessel enclosing a titanium alloy rod supporting the sample and a sealing bellows. A transducer at the top end of the titanium rod generates ultrasonic waves and collects the series of subsequent reflections. Preliminary tests with pure water illustrate a precision of 0.02% and an accuracy within 0.1% of IAPWS on our whole pressure range. Revision of the properties of pure water and H2O-MgSO4 solutions up to 0.7 GPa along with the first data in the H2O-MgCl2 above 0.1 GPa will be presented, and their implications for the internal structure or large icy moons discussed.

Daytime avoidance of chemosensory alarm cues by adult sea lamprey (Petromyzon marinus)

USGS Publications Warehouse

Di Rocco, Richard; Belanger, Cowan; Imre, István; Brown, Grant; Johnson, Nicholas S.

2014-01-01

Sea lamprey (Petromyzon marinus) avoid damage-released and predator chemosensory cues at night, but their response to these cues during the day is unknown. Here, we explored (i) whether sea lamprey avoid these cues during the day and (ii) the effect of water temperature on the avoidance of chemosensory alarm cues in two diurnal laboratory experiments. We hypothesized that daytime activity would be temperature-dependent and that only sea lamprey vulnerable to predation (i.e., not hiding) would behaviourally respond to chemosensory alarm cues. Ten groups of ten sea lamprey were exposed to one of a variety of potential chemosensory cues. The experiments were conducted over a range of temperatures to quantify the effect of temperature on avoidance behaviour. Consistent with our hypothesis, a higher proportion of animals were active during daytime as water temperature increased. Moving sea lamprey showed an avoidance response to 2-phenylethylamine (a compound found in mammalian urine) and human saliva once water temperatures had risen to mean (±SD) = 13.7 (±1.4) °C. Resting and hiding sea lamprey did not show an avoidance response to any of the experimental stimuli.

Eutrophication exacerbates the impact of climate warming on lake methane emission.

PubMed

Sepulveda-Jauregui, Armando; Hoyos-Santillan, Jorge; Martinez-Cruz, Karla; Walter Anthony, Katey M; Casper, Peter; Belmonte-Izquierdo, Yadira; Thalasso, Frédéric

2018-04-27

Net methane (CH 4 ) emission from lakes depends on two antagonistic processes: CH 4 production (methanogenesis) and CH 4 oxidation (methanotrophy). It is unclear how climate warming will affect the balance between these processes, particularly among lakes of different trophic status. Here we show that methanogenesis is more sensitive to temperature than methanotrophy, and that eutrophication magnifies this temperature sensitivity. Using laboratory incubations of water and sediment from ten tropical, temperate and subarctic lakes with contrasting trophic states, ranging from oligotrophic to hypereutrophic, we explored the temperature sensitivity of methanogenesis and methanotrophy. We found that both processes presented a higher temperature sensitivity in tropical lakes, followed by temperate, and subarctic lakes; but more importantly, we found that eutrophication triggered a higher temperature sensitivity. A model fed by our empirical data revealed that increasing lake water temperature by 2 °C leads to a net increase in CH 4 emissions by 101-183% in hypereutrophic lakes and 47-56% in oligotrophic lakes. We conclude that climate warming will tilt the CH 4 balance towards higher lake emission and that this impact will be exacerbated by the eutrophication of the lakes. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparative study of magnetic ordering in bulk and nanoparticles of Sm0.65Ca0.35MnO3: Magnetization and electron magnetic resonance measurements

NASA Astrophysics Data System (ADS)

Goveas, Lora Rita; Anuradha, K. N.; Bhagyashree, K. S.; Bhat, S. V.

2015-05-01

To explore the effect of size reduction to nanoscale on the hole doped Sm0.65Ca0.35MnO3 compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario.

Pristine carbon nanotubes based resistive temperature sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alam, Md Bayazeed, E-mail: bayazeed786@gmail.com; Jamia Millia Islamia; Saini, Sudhir Kumar, E-mail: sudhirsaini1310@gmail.com

A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible methodmore » to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.« less

Spectral photometry of extreme helium stars: Ultraviolet fluxes and effective temperature

NASA Technical Reports Server (NTRS)

Drilling, J. S.; Schoenberner, D.; Heber, U.; Lynas-Gray, A. E.

1982-01-01

Ultraviolet flux distributions are presented for the extremely helium rich stars BD +10 deg 2179, HD 124448, LSS 3378, BD -9 deg 4395, LSE 78, HD 160641, LSIV -1 deg 2, BD 1 deg 3438, HD 168476, MV Sgr, LS IV-14 deg 109 (CD -35 deg 11760), LSII +33 deg 5 and BD +1 deg 4381 (LSIV +2 deg 13) obtained with the International Ultraviolet Explorer (IUE). Broad band photometry and a newly computed grid of line blanketed model atmospheres were used to determine accurate angular diameters and total stellar fluxes. The resultant effective temperatures are in most cases in satisfactory agreement with those based on broad band photometry and/or high resolution spectroscopy in the visible. For two objects, LSII +33 deg 5 and LSE 78, disagreement was found between the IUE observations and broadband photometry: the colors predict temperatures around 20,000 K, whereas the UV spectra indicate much lower photospheric temperatures of 14,000 to 15,000 K. The new temperature scale for extreme helium stars extends to lower effective temperatures than that of Heber and Schoenberner (1981) and covers the range from 8,500 K to 32,000 K.

Multi-shock experiments on a TATB-based composition

NASA Astrophysics Data System (ADS)

Sorin, Remy

2017-06-01

Temperature based models for condensed explosive need an unreacted equation of state (EOS) that allows a realistic estimation of the temperature for a shock compression driven at detonation velocity. To feed the detonation models, we aim at exploring the high pressure shock Hugoniot of unreacted TATB composition up to 30 GPa with both hydrodynamic and temperature measurements. We performed on the gas gun facility ARES, multi-shock experiments where the first shock is designed to desensitize the explosive and inhibit the reactivity of the composition. The hydrodynamic behavior was measured via the velocity of a TATB/LiF interface with PDV probes. We attempted to measure the temperature of the shocked material via surface emissivity with a pyrometer calibrated to the expected low temperature range. Based on single shock experiments and on ab-initio calculation, we built a complete EOS for the unreacted phase of the TATB explosive. The hydrodynamic data are in good agreement with our unreacted EOS. Despite the record of multi-stage emissivity signals, the temperature measurements were difficult to interpret dur to high-luminisity phenomena pertubation. In collaboration with: Nicolas Desbiens, Vincent Dubois and Fabrice Gillot, CEA DAM DIF.

Ion composition and temperature in the topside ionosphere.

NASA Technical Reports Server (NTRS)

Brace, L. H.; Dunham, G. S.; Mayr, H. G.

1967-01-01

Particle and energy continuity equations derived and solved by computer method ion composition and plasma temperature measured by Explorer XXII PARTICLE and energy continuity equations derived and solved by computer method for ion composition and plasma temperature measured by Explorer XXII

Effects of Dopant on Depoling Temperature in Modified BiScO3 - PbTiO3

NASA Technical Reports Server (NTRS)

Kowalski, Benjamin; Sehirlioglu, Alp

2014-01-01

In recent years there has been a renewed interest for high temperature piezoelectrics for both terrestrial and aerospace applications. These applications are limited in part by the operating temperature, which is usually taken as one half of the Curie temperature (Tc), and is 200C for one of the most widely used commercial piezoelectrics, Pb(Zr,Ti)O3 (PZT). In an effort to increase Tc, subsequent research into high temperature Bi(BB)O3 PbTiO3 piezoelectrics led to the discovery of the morphotropic phase boundary (MPB) in the high-Tc BiScO3 PbTiO3 (BS-PT) system with a Tc of 460C and a d33 of 460 pmV. The Tc marks the ferroelectric to paraelectric phase transformation and while, in general, a phase transformation leads to thermal depoling in piezoelectrics with low or moderate Tcs, for high Tc piezoelectrics thermally assisted dipole rotation can lead to randomization of domains at temperatures below Tc. It becomes necessary to determine the depoling temperature (Td) which dictates the actual working temperature range. By doping for Sc and Ti the Td can be shifted while maintaining similar electromechanical properties as a function of temperature. The effect of this B-site doping on depoling temperature has been explored through the characterization of microstructure and weakhigh field measurements.

The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

USGS Publications Warehouse

Hurwitz, S.; Farrar, C.D.; Williams, C.F.

2010-01-01

Long Valley Caldera in eastern California formed 0.76Ma ago in a cataclysmic eruption that resulted in the deposition of 600km3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~290MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40MWe. The RD in the center of the caldera was uplifted by ~80cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients <50??C/km at their bottom. The maximum temperature in the individual boreholes ranges between 124.7??C and 129.5??C and bottom hole temperatures range between 99.4??C and 129.5??C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate horizontal groundwater velocities in the hydrothermal flow unit under the RD that range from 1.9 to 2.8m/yr, which corresponds to a maximum power flowing through the RD of 3-4MW. The relatively low temperatures and large isothermal segments at the bottom of the temperature profiles are inconsistent with the presence of magma at shallow crustal levels. ?? 2010.

The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

NASA Astrophysics Data System (ADS)

Hurwitz, Shaul; Farrar, Christopher D.; Williams, Colin F.

2010-12-01

Long Valley Caldera in eastern California formed 0.76 Ma ago in a cataclysmic eruption that resulted in the deposition of 600 km 3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~ 290 MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40 MWe. The RD in the center of the caldera was uplifted by ~ 80 cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158 m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients <50 °C/km at their bottom. The maximum temperature in the individual boreholes ranges between 124.7 °C and 129.5 °C and bottom hole temperatures range between 99.4 °C and 129.5 °C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate horizontal groundwater velocities in the hydrothermal flow unit under the RD that range from 1.9 to 2.8 m/yr, which corresponds to a maximum power flowing through the RD of 3-4 MW. The relatively low temperatures and large isothermal segments at the bottom of the temperature profiles are inconsistent with the presence of magma at shallow crustal levels.

Embryonic developmental patterns and energy expenditure are affected by incubation temperature in wood ducks (Aix sponsa).

PubMed

DuRant, S E; Hopkins, W A; Hepp, G R

2011-01-01

Recent research in birds has demonstrated that incubation temperature influences a suite of traits important for hatchling development and survival. We explored a possible mechanism for the effects on hatchling quality by determining whether incubation temperature influences embryonic energy expenditure of wood ducks (Aix sponsa). Because avian embryos are ectothermic, we hypothesized that eggs incubated at higher temperatures would have greater energy expenditure at any given day of incubation. However, because eggs incubated at lower temperatures take longer to hatch than embryos incubated at higher temperatures, we hypothesized that the former would expend more energy during incubation. We incubated eggs at three temperatures (35.0°, 35.9°, and 37.0°C) that fall within the range of temperatures of naturally incubated wood duck nests. We then measured the respiration of embryos every 3 d during incubation, immediately after ducks externally pipped, and immediately after hatching. As predicted, embryos incubated at the highest temperature had the highest metabolic rates on most days of incubation, and they exhibited faster rates of development. Yet, because of greater energy expended during the hatching process, embryos incubated at the lowest temperature expended 20%-37% more energy during incubation than did embryos incubated at the higher temperatures. Slower developmental rates and greater embryonic energy expenditure of embryos incubated at the lowest temperature could contribute to their poor physiological performance as ducklings compared with ducklings that hatch from eggs incubated at higher temperatures.

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

Calling behaviour under climate change: geographical and seasonal variation of calling temperatures in ectotherms.

PubMed

Llusia, Diego; Márquez, Rafael; Beltrán, Juan F; Benítez, Maribel; do Amaral, José P

2013-09-01

Calling behaviour is strongly temperature-dependent and critical for sexual selection and reproduction in a variety of ectothermic taxa, including anuran amphibians, which are the most globally threatened vertebrates. However, few studies have explored how species respond to distinct thermal environments at time of displaying calling behaviour, and thus it is still unknown whether ongoing climate change might compromise the performance of calling activity in ectotherms. Here, we used new audio-trapping techniques (automated sound recording and detection systems) between 2006 and 2009 to examine annual calling temperatures of five temperate anurans and their patterns of geographical and seasonal variation at the thermal extremes of species ranges, providing insights into the thermal breadths of calling activity of species, and the mechanisms that enable ectotherms to adjust to changing thermal environments. All species showed wide thermal breadths during calling behaviour (above 15 °C) and increases in calling temperatures in extremely warm populations and seasons. Thereby, calling temperatures differed both geographically and seasonally, both in terrestrial and aquatic species, and were 8-22 °C below the specific upper critical thermal limits (CTmax ) and strongly associated with the potential temperatures of each thermal environment (operative temperatures during the potential period of breeding). This suggests that calling behaviour in ectotherms may take place at population-specific thermal ranges, diverging when species are subjected to distinct thermal environments, and might imply plasticity of thermal adjustment mechanisms (seasonal and developmental acclimation) that supply species with means of coping with climate change. Furthermore, the thermal thresholds of calling at the onset of the breeding season were dissimilar between conspecific populations, suggesting that other factors besides temperature are needed to trigger the onset of reproduction. Our findings imply that global warming would not directly inhibit calling behaviour in the study species, although might affect other temperature-dependent features of their acoustic communication system. © 2013 John Wiley & Sons Ltd.

Sapphire Whispering Gallery Thermometer

NASA Astrophysics Data System (ADS)

Strouse, G. F.

2007-12-01

An innovative sapphire whispering gallery thermometer (SWGT) is being explored at the National Institute of Standards and Technology (NIST) as a potential replacement for a standard platinum resistance thermometer (SPRT) for industrial applications that require measurement uncertainties of ≤ 10 mK. The NIST SWGT uses a synthetic sapphire monocrystalline disk configured as a uniaxial, dielectric resonator with whispering gallery modes between 14 GHz and 20 GHz and with Q-factors as large as 90,000. The prototype SWGT stability at the ice melting point (0°C) is ≤ 1 mK with a frequency resolution equivalent to 0.05 mK. The prototype SWGT measurement uncertainty ( k= 1) is 10 mK from 0°C to 100°C for all five resonance modes studied. These results for the SWGT approach the capabilities of industrial resistance thermometers. The SWGT promises greatly increased resistance to mechanical shock relative to SPRTs, over the range from -196°C to 500°C while retaining the low uncertainties needed by secondary calibration laboratories. The temperature sensitivity of the SWGT depends upon a well-defined property (the refractive index at microwave frequencies) and the thermal expansion of a pure material. Therefore, it is expected that SWGTs can be calibrated over a wide temperature range using a reference function, along with deviations measured at a few fixed points. This article reports the prototype SWGT stability, resolution, repeatability, and the temperature dependence of five whispering gallery resonance frequencies in the range from 0°C to 100°C.

Annealing dependent evolution of columnar nanostructures in RF magnetron sputtered PTFE films for hydrophobic applications

NASA Astrophysics Data System (ADS)

Tripathi, S.; De, Rajnarayan; Maidul Haque, S.; Divakar Rao, K.; Misal, J. S.; Prathap, C.; Das, S. C.; Patidar, Manju M.; Ganesan, V.; Sahoo, N. K.

2018-01-01

Present communication focuses on a relatively less explored direction of producing rough polytetrafluoroethylene (PTFE) surfaces for possible hydrophobic applications. The experiments were carried out to make rough PTFE films without losing much of the transmission, which is an important factor while designing futuristic solar cell protection covers. After annealing temperature optimization, as grown RF magnetron sputtered PTFE films (prepared at 160 W RF power) were subjected to vacuum annealing at 200 °C for different time durations ranging from 1 to 4 h. The films show morphological evolution exhibiting formation and growth of columnar nanostructures that are responsible for roughening of the films due to annealing induced molecular migration and rearrangement. In agreement with this, qualitative analysis of corresponding x-ray reflectivity data shows modification in film thickness, which may again be attributed to the growth of columns at the expense of the atoms of remaining film molecules. However, the observations reveal that the film annealed at 200 °C for 2 h gives a combination of patterned columnar structures and reasonable transmission of >85% (in 500-1000 nm wavelength range), both of which are deteriorated when the films are annealed either at high temperature beyond 200 °C or for long durations >3 h. In addition, attenuated total reflection-Fourier transform infrared spectroscopy results reveal that the molecular bonds remain intact upon annealing at any temperature within the studied range indicating the stable nature of the films.

Noble gas isotopes as low-budget exploration and monitoring tool for high- and low-temperature geothermal systems in extensional tectonic regimes

NASA Astrophysics Data System (ADS)

Kraml, Michael; Jodocy, Marco; Aeschbach, Werner; Kreuter, Horst

2017-04-01

Since viable geothermal systems in extensional settings are sparse compared to those situated in subduction zone environments, a specifically adapted exploration methodology of the former is currently not fully established. Standardized exploration methods applicable to geothermal systems related to subduction zones do not always deliver reliable or even deliver misleading results (e.g. Ochmann et al. 2010). The identification of promising prospects at the beginning of surface exploration studies is saving time and money of the project developer and investor. Noble gas isotope analyses can provide a low-budget tool for assessing the quality of the prospect in a very early exploration phase. Case studies of high- and low-temperature prospects situated in the East African Rift System and the Upper Rhine Graben, Germany will be presented and compared to other extensional areas like the Basin and Range Province, U.S.A. (Kraml et al. 2016a,b). Noble gas isotopes are also a versatile tool for monitoring of geothermal reservoirs during the production/exploitation phase. References Kraml, M., Jodocy, M., Reinecker, J., Leible, D., Freundt, F., Al Najem, S., Schmidt, G., Aeschbach, W., and Isenbeck-Schroeter, M. (2016a): TRACE: Detection of Permeable Deep-Reaching Fault Zone Sections in the Upper Rhine Graben, Germany, During Low-Budget Isotope-Geochemical Surface Exploration. Proceedings European Geothermal Congress 2016, Strasbourg, France, 19-24 Sept 2016 Kraml, M., Kaudse, T., Aeschbach, W. and Tanzanian Exploration Team (2016b): The search for volcanic heat sources in Tanzania: A helium isotope perspective. Proceedings 6th African Rift Geothermal Conference, Addis Ababa, Ethiopia, 2nd-4th November 2016 Ochmann, N., Kraml, M., Lindenfeld, M., Yakovlev, A., Rümpker, G., Babirye, P. (2010): Microearthquake Survey at the Buranga Geothermal Prospect (Western Uganda). Proceedings World Geothermal Congress, 25-29 April 2010, Bali, Indonesia (paper number 1126)

Isolation and characterization of Lactobacillus helveticus DSM 20075 variants with improved autolytic capacity.

PubMed

Spus, Maciej; Liu, Hua; Wels, Michiel; Abee, Tjakko; Smid, Eddy J

2017-01-16

Lactobacillus helveticus is widely used in dairy fermentations and produces a range of enzymes, which upon cell lysis can be released into the cheese matrix and impact degradation of proteins, peptides and lipids. In our study we set out to explore the potential of Lb. helveticus DSM 20075 for increased autolytic capacity triggered by conditions such as low pH and high salt concentrations encountered in cheese environments. Lb. helveticus DSM 20075 was subjected to varied incubation temperatures (ranging from 37 to 50°C). High-temperature incubation (in the range of 45 to 50°C) allowed us to obtain a collection of six variant strains (V45-V50), which in comparison to the wild-type strain, showed higher growth rates at elevated temperatures (42°C-45°C). Moreover, variant strain V50 showed a 4-fold higher, in comparison to wild type, autolytic capacity in cheese-like conditions. Next, strain V50 was used as an adjunct in lab-scale cheese making trials to measure its impact on aroma formation during ripening. Specifically, in cheeses made with strain V50, the relative abundance of benzaldehyde increased 3-fold compared to cheeses made with the wild-type strain. Analysis of the genome sequence of strain V50 revealed multiple mutations in comparison to the wild-type strain DSM 20075 including a mutation found in a gene coding for a metal ion transporter, which can potentially be linked to intracellular accumulation of Mn 2+ and benzaldehyde formation. The approach of high-temperature incubation can be applied in dairy industry for the selection of (adjunct) cultures targeted at accelerated cheese ripening and aroma formation. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of temperature and precipitation on grassland bird nesting success as mediated by patch size.

PubMed

Zuckerberg, Benjamin; Ribic, Christine A; McCauley, Lisa A

2018-02-06

Grassland birds are declining faster than any other bird guild across North America. Shrinking ranges and population declines are attributed to widespread habitat loss and increasingly fragmented landscapes of agriculture and other land uses that are misaligned with grassland bird conservation. Concurrent with habitat loss and degradation, temperate grasslands have been disproportionally affected by climate change relative to most other terrestrial biomes. Distributions of grassland birds often correlate with gradients in climate, but few researchers have explored the consequences of weather on the demography of grassland birds inhabiting a range of grassland fragments. To do so, we modeled the effects of temperature and precipitation on nesting success rates of 12 grassland bird species inhabiting a range of grassland patches across North America (21,000 nests from 81 individual studies). Higher amounts of precipitation in the preceding year were associated with higher nesting success, but wetter conditions during the active breeding season reduced nesting success. Extremely cold or hot conditions during the early breeding season were associated with lower rates of nesting success. The direct and indirect influence of temperature and precipitation on nesting success was moderated by grassland patch size. The positive effects of precipitation in the preceding year on nesting success were strongest in relatively small grassland patches and had little effect in large patches. Conversely, warm temperatures reduced nesting success in small grassland patches but increased nesting success in large patches. Mechanisms underlying these differences may be patch-size-induced variation in microclimates and predator activity. Although the exact cause is unclear, large grassland patches, the most common metric of grassland conservation, appears to moderate the effects of weather on grassland-bird demography and could be an effective component of climate-change adaptation. © 2018 Society for Conservation Biology.

Long timestep dynamics of peptides by the dynamics driver approach.

PubMed

Derreumaux, P; Schlick, T

1995-04-01

Previous experience with the Langevin/implicit-Euler scheme for dynamics ("LI") on model systems (butane, water) has shown that LI is numerically stable for timesteps in the 5-20 fs range but quenches high-frequency modes. To explore applications to polypeptides, we apply LI to model systems (several dipeptides, a tetrapeptide, and a 13-residue oligoalanine) and also develop a new dynamics driver approach ("DA"). The DA scheme, based on LI, addresses the important issue of proper sampling, which is unlikely to be solved by small-timestep integration methods or implicit methods with intrinsic damping at room temperature, such as LI. Equilibrium averages, time-dependent molecular properties, and sampling trends at room temperature are reported for both LI and DA dynamics simulations, which are then compared to those generated by a standard explicit discretization of the Langevin equation with a 1 fs timestep. We find that LI's quenching effects are severe on both the fast and slow (due to vibrational coupling) frequency modes of all-atom polypeptides and lead to more restricted dynamics at moderate timesteps (40 fs). The DA approach empirically counteracts these damping effects by adding random atomic perturbations to the coordinates at each step (before the minimization of a dynamics function). By restricting the energetic fluctuations and controlling the kinetic energy, we are able with a 60 fs timestep to generate continuous trajectories that sample more of the relevant conformational space and also reproduce reasonably Boltzmann statistics. Although the timescale for transition may be accelerated by the DA approach, the transitional information obtained for the alanine dipeptide and the tetrapeptide is consistent with that obtained by several other theoretical approaches that focus specifically on the determination of pathways. While the trajectory for oligoalanine by the explicit scheme over the nanosecond timeframe remains in the vicinity of the full alpha R-helix starting structure, and a high-temperature (600 degrees K) MD trajectory departs slowly from the alpha helical structure, the DA-generated trajectory for the same CPU time exhibits unfolding and refolding and reveals a range of conformations with an intermediate helix content. Significantly, this range of states is more consistent with spectroscopic experiments on small peptides, as well as the cooperative two-state model for helix-coil transition. The good, near-Boltzmann statistics reported for the smaller systems above, in combination with the interesting oligoalanine results, suggest that DA is a promising tool for efficiently exploring conformational spaces of biomolecules and exploring folding/unfolding processes of polypeptides.

Apatite (U-Th)/He Thermochronometry as an innovative Geothermal Exploration Tool - A case study from the Wassuk Range, Hawthorne, Nevada

NASA Astrophysics Data System (ADS)

Gorynski, K. E.; Stockli, D. F.; Walker, J. D.

2010-12-01

A utility-grade geothermal system requires increased, near-surface temperatures (>120°C), water to transfer heat, and structural or sedimentological fluid conduits. In extensional tectonic settings, geothermal anomalies often occur in areas with recent, high strain accumulation and complex faulting (i.e., cross-faults, accommodation zones) where exhumation and uplift of footwall rocks transfer heat, via advection, to the near-surface which is further carried by water through structural fluid conduits. Apatite helium (AHe) thermochronometric footwall age mapping can be used in conjunction with these genetic occurrence models to further focus regional-scale geothermal exploration efforts to areas of probabilistic increased fracture permeability and most recent, rapid footwall exhumation. Furthermore, partially reset apatites resulting from interaction with hydrothermal fluids (>40°C) will show which areas have been hottest most recently. This case study in the Wassuk Range, Hawthrone, NV confirms the utility of AHe thermochronometry as a geothermal exploration tool. A dense grid of footwall samples were collected adjacent to the Hawthorne geothermal anomaly (>85°C BHT) located in the hanging wall of the Wassuk Range block. Our data show that the location of the present-day geothermal anomaly correlates with the location of 1) the most recent episode of rapid footwall exhumation at 3.5-4 Ma, 2) km scale accommodation zones between differentially tilted Wassuk Range blocks, and 3) an elevated Miocene geothermal gradient. Furthermore, anomalously young AHe ages (<3.5 Ma) mimic the lateral extent of the Hawthorne geothermal anomaly and likely resulted from interaction with a deep-seated geothermal cell or hot hydrothermal fluids.

Analysis of temperature in conventional and ultrasonically-assisted drilling of cortical bone with infrared thermography.

PubMed

Alam, K; Silberschmidt, Vadim V

2014-01-01

Bone drilling is widely used in orthopaedics, dental and neurosurgeries for repair and fixation purposes. One of the major concerns in drilling of bone is thermal necrosis that may seriously affect healing at interfaces with fixtures and implants. Ultrasonically-assisted drilling (UAD) is recently introduced as alternative to conventional drilling (CD) to minimize invasiveness of the procedure. This paper studies temperature rise in bovine cortical bone drilled with CD and UAD techniques and their comparison using infrared thermography. A parametric investigation was carried out to evaluate effects of drilling conditions (drilling speed and feed rate) and parameters of ultrasonic vibration (frequency and amplitude) on the temperature elevation in bone. Higher levels of the drilling speed and feed rate were found responsible for generating temperatures above a thermal threshold level in both types of drilling. UAD with frequency below 20 kHz resulted in lower temperature compared to CD with the same drilling parameters. The temperatures generated in cases with vibration frequency exceeding 20 kHz were significantly higher than those in CD for the range of drilling speeds and feed rates. The amplitude of vibration was found to have no significant effect on bone temperature. UAD may be investigated further to explore its benefits over the existing CD techniques.

Mobility of Supercooled liquid Toluene, Ethylbenzene, and Benzene near their Glass Transition Temperatures Investigated using Inert Gas Permeation

DOE Office of Scientific and Technical Information (OSTI.GOV)

May, Robert A.; Smith, R. Scott; Kay, Bruce D.

We investigate the mobility of supercooled liquid toluene, ethylbenzene, and benzene near their respective glass transition temperatures (Tg). The permeation rate of Ar, Kr, and Xe through the supercooled liquid created when initially amorphous overlayers heated above their glass transition temperature is used to determine the diffusivity. Amorphous benzene crystallizes at temperatures well below its Tg and as a result the inert gas underlayer remains trapped until the onset of benzene desorption. In contrast, for toluene and ethylbenzene the onset of inert gas permeation is observed at temperatues near Tg. The inert gas desorption peak temperature as a function ofmore » the heating rate and overlayer thickness is used to quantify the diffusivity of supercooled liquid toluene and ethylbenzene from 115 K to 135 K. In this temperature range, diffusivities are found to vary across five orders of magnitude (~10-14 to 10-9 cm2/s). These data are compared to viscosity measurements and used to determine the low temperature fractional Stokes-Einstein exponent. Efforts to determine the diffusivity of a mixture of benzene and ethylbenzene are detailed, and the effect of mixing these materials on benzene crystallization is explored using infrared spectroscopy.« less

Cooling effect of rivers on metropolitan Taipei using remote sensing.

PubMed

Chen, Yen-Chang; Tan, Chih-Hung; Wei, Chiang; Su, Zi-Wen

2014-01-23

This study applied remote sensing technology to analyze how rivers in the urban environment affect the surface temperature of their ambient areas. While surface meteorological stations can supply accurate data points in the city, remote sensing can provide such data in a two-dimensional (2-D) manner. The goal of this paper is to apply the remote sensing technique to further our understanding of the relationship between the surface temperature and rivers in urban areas. The 2-D surface temperature data was retrieved from Landsat-7 thermal infrared images, while data collected by Formosat-2 was used to categorize the land uses in the urban area. The land surface temperature distribution is simulated by a sigmoid function with nonlinear regression analysis. Combining the aforementioned data, the range of effect on the surface temperature from rivers can be derived. With the remote sensing data collected for the Taipei Metropolitan area, factors affecting the surface temperature were explored. It indicated that the effect on the developed area was less significant than on the ambient nature zone; moreover, the size of the buffer zone between the river and city, such as the wetlands or flood plain, was found to correlate with the affected distance of the river surface temperature.

Cooling Effect of Rivers on Metropolitan Taipei Using Remote Sensing

PubMed Central

Chen, Yen-Chang; Tan, Chih-Hung; Wei, Chiang; Su, Zi-Wen

2014-01-01

This study applied remote sensing technology to analyze how rivers in the urban environment affect the surface temperature of their ambient areas. While surface meteorological stations can supply accurate data points in the city, remote sensing can provide such data in a two-dimensional (2-D) manner. The goal of this paper is to apply the remote sensing technique to further our understanding of the relationship between the surface temperature and rivers in urban areas. The 2-D surface temperature data was retrieved from Landsat-7 thermal infrared images, while data collected by Formosat-2 was used to categorize the land uses in the urban area. The land surface temperature distribution is simulated by a sigmoid function with nonlinear regression analysis. Combining the aforementioned data, the range of effect on the surface temperature from rivers can be derived. With the remote sensing data collected for the Taipei Metropolitan area, factors affecting the surface temperature were explored. It indicated that the effect on the developed area was less significant than on the ambient nature zone; moreover, the size of the buffer zone between the river and city, such as the wetlands or flood plain, was found to correlate with the affected distance of the river surface temperature. PMID:24464232

Thermal growth potential of Atlantic cod by the end of the 21st century.

PubMed

Butzin, Martin; Pörtner, Hans-Otto

2016-12-01

Ocean warming may lead to smaller body sizes of marine ectotherms, because metabolic rates increase exponentially with temperature while the capacity of the cardiorespiratory system to match enhanced oxygen demands is limited. Here, we explore the impact of rising sea water temperatures on Atlantic cod (Gadus morhua), an economically important fish species. We focus on changes in the temperature-dependent growth potential by a transfer function model combining growth observations with climate model ensemble temperatures. Growth potential is expressed in terms of asymptotic body weight and depends on water temperature. We consider changes between the periods 1985-2004 and 2081-2100, assuming that future sea water temperatures will evolve according to climate projections for IPCC AR5 scenario RCP8.5. Our model projects a response of Atlantic cod to future warming, differentiated according to ocean regions, leading to increases of asymptotic weight in the Barents Sea, while weights are projected to decline at the southern margin of the biogeographic range. Southern spawning areas will disappear due to thermal limitation of spawning stages. These projections match the currently observed biogeographic shifts and the temperature- and oxygen-dependent decline in routine aerobic scope at southern distribution limits. © 2016 John Wiley & Sons Ltd.

Stability and cytotoxicity of crystallin amyloid nanofibrils

NASA Astrophysics Data System (ADS)

Kaur, Manmeet; Healy, Jackie; Vasudevamurthy, Madhusudan; Lassé, Moritz; Puskar, Ljiljana; Tobin, Mark J.; Valery, Celine; Gerrard, Juliet A.; Sasso, Luigi

2014-10-01

Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases. Crystallin nanofibrils were compared to well characterised insulin and whey protein fibrils using Thioflavin T assays and TEM imaging. Cell cytotoxicity assays suggest no adverse impact of both mature and fragmented crystallin fibrils on cell viability of Hec-1a endometrial cells. An IR microspectroscopy study supports long-term structural integrity of crystallin nanofibrils.Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases. Crystallin nanofibrils were compared to well characterised insulin and whey protein fibrils using Thioflavin T assays and TEM imaging. Cell cytotoxicity assays suggest no adverse impact of both mature and fragmented crystallin fibrils on cell viability of Hec-1a endometrial cells. An IR microspectroscopy study supports long-term structural integrity of crystallin nanofibrils. Electronic supplementary information (ESI) available: ThT fluorescence graphs of buffers and solvents used for normalising ThT fluorescence of PNFs in the experiments (Fig. S1 and S2). Representative TEM images of fibrils over a wide range of pH and at variety of temperatures (Fig. S3 and S4). IR spectra of the amide fingerprinting region, including baseline (Fig. S5). See DOI: 10.1039/c4nr04624b

Normal range and lateral symmetry in the skin temperature profile of pregnant women

NASA Astrophysics Data System (ADS)

Pereira, Tânia; Nogueira-Silva, Cristina; Simoes, Ricardo

2016-09-01

Body skin temperature is a useful parameter for diagnosing diseases and infrared thermography can be a powerful tool in providing important information to detect body temperature changes in a noninvasive way. The aim of this work was to study the pattern of skin temperature during pregnancy, to establish skin temperature reference values and to find correlations between these and the pregnant population characteristics. Sixty-one healthy pregnant women (mean age 30.6 ± 5.1 years) in the 8th-40th gestational week with normal pregnancies were examined in 31 regions of interest (ROI). The ROIs were defined all over the body in order to determine the most influenced by factors such as age or body mass index (BMI). The results obtained in this work highlight that in normal pregnant women the skin temperature is symmetrically distributed, with the symmetrical areas differing less than 0.5 °C , with a mean value of 0.25 ± 0.23 °C . This study identified a significant negative correlation between the BMI and temperature. Age has been shown to have great influence on the skin temperature, with a significant increase of temperature observed with age. This work explores a novel medical application of infrared thermography and provides a characterization of thermal skin profile in human pregnancy for a large set of ROIs while also evaluating the effects of age and BMI.

Climate dominated topography in a tectonically active mountain range

NASA Astrophysics Data System (ADS)

Adams, B. A.; Ehlers, T. A.

2015-12-01

Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The broad spatial trend in channel steepness values suggests that the locus of high rock uplift rates is coincident with the rugged range core, in a similar position as high temperature and pressure lithologies, but not in the low lying foothills as has been previously suggested by low-temperature thermochronometry. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns. We demonstrate the same topographic effects are recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on topography makes the argument of mountain range steadiness untenable in significantly glaciated settings. Furthermore, our results suggest that most glaciated Cenozoic ranges are likely still in a mode of readjustment as fluvial systems change topography and erosion rates to equilibrate with rock uplift rates.

Flight experience of solar mesosphere explorer's power system over high temperatures ranges

NASA Technical Reports Server (NTRS)

Faber, Jack; Hurley, Daniel

1987-01-01

The performance of the power system on the Solar Mesosphere Explorer (SME) satellite for the life of the mission and the techniques used to ensure power system health are summarized. Early in the mission high cell imbalances in one of the batteries resulted in a loading scheme which attempted to minimize the cell imbalances without causing an undervoltage condition. A short term model of the power system allowed planners to predict depth of discharge using the latest available data. Due to expected orbital shifts the solar arrays experience extended periods of no eclipse. This has required special conditioning schemes to keep the batteries healthy when the eclipses return. Analysis of the SME data indicates long term health of the SME power system as long as the conditioning scheme is continued.

LADEE Science Results and Implications for Exploration

NASA Technical Reports Server (NTRS)

Elphic, R. C.; M. Horanyi; Colaprete, A.; Benna; Mahaffy, P.; Delory, G. T.; Noble, S. K.; Halekas, J. S.; Hurley, D. M.; Stubbs, T. J.;

A study of power cycles using supercritical carbon dioxide as the working fluid

NASA Astrophysics Data System (ADS)

Schroder, Andrew Urban

A real fluid heat engine power cycle analysis code has been developed for analyzing the zero dimensional performance of a general recuperated, recompression, precompression supercritical carbon dioxide power cycle with reheat and a unique shaft configuration. With the proposed shaft configuration, several smaller compressor-turbine pairs could be placed inside of a pressure vessel in order to avoid high speed, high pressure rotating seals. The small compressor-turbine pairs would share some resemblance with a turbocharger assembly. Variation in fluid properties within the heat exchangers is taken into account by discretizing zero dimensional heat exchangers. The cycle analysis code allows for multiple reheat stages, as well as an option for the main compressor to be powered by a dedicated turbine or an electrical motor. Variation in performance with respect to design heat exchanger pressure drops and minimum temperature differences, precompressor pressure ratio, main compressor pressure ratio, recompression mass fraction, main compressor inlet pressure, and low temperature recuperator mass fraction have been explored throughout a range of each design parameter. Turbomachinery isentropic efficiencies are implemented and the sensitivity of the cycle performance and the optimal design parameters is explored. Sensitivity of the cycle performance and optimal design parameters is studied with respect to the minimum heat rejection temperature and the maximum heat addition temperature. A hybrid stochastic and gradient based optimization technique has been used to optimize critical design parameters for maximum engine thermal efficiency. A parallel design exploration mode was also developed in order to rapidly conduct the parameter sweeps in this design space exploration. A cycle thermal efficiency of 49.6% is predicted with a 320K [47°C] minimum temperature and 923K [650°C] maximum temperature. The real fluid heat engine power cycle analysis code was expanded to study a theoretical recuperated Lenoir cycle using supercritical carbon dioxide as the working fluid. The real fluid cycle analysis code was also enhanced to study a combined cycle engine cascade. Two engine cascade configurations were studied. The first consisted of a traditional open loop gas turbine, coupled with a series of recuperated, recompression, precompression supercritical carbon dioxide power cycles, with a predicted combined cycle thermal efficiency of 65.0% using a peak temperature of 1,890K [1,617°C]. The second configuration consisted of a hybrid natural gas powered solid oxide fuel cell and gas turbine, coupled with a series of recuperated, recompression, precompression supercritical carbon dioxide power cycles, with a predicted combined cycle thermal efficiency of 73.1%. Both configurations had a minimum temperature of 306K [33°C]. The hybrid stochastic and gradient based optimization technique was used to optimize all engine design parameters for each engine in the cascade such that the entire engine cascade achieved the maximum thermal efficiency. The parallel design exploration mode was also utilized in order to understand the impact of different design parameters on the overall engine cascade thermal efficiency. Two dimensional conjugate heat transfer (CHT) numerical simulations of a straight, equal height channel heat exchanger using supercritical carbon dioxide were conducted at various Reynolds numbers and channel lengths.

Adhesive Properties of Polyacrylate Gels

NASA Astrophysics Data System (ADS)

Flanigan, Cynthia; Shull, Kenneth

1998-03-01

Soft, low-modulus gels provide an interesting opportunity to examine small adhesive interactions between two bodies in contact. As shown through dynamic rheological studies, our materials undergo a rapid gelation as they are cooled from a viscous liquid at elevated temperatures to a soft, elastic solid at room temperature. At low temperatures, the gels exhibit a linearly elastic response and display moduli close to 100Pa, thereby forming materials with great potential for quantifying weak adhesive interactions with a variety of bodies ranging from polymer surfaces to biological entities. Our current studies focus on investigating interfacial effects by performing axisymmetric adhesion tests with a model polyacrylate gel formed by diluting the copolymer poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) to a 5-15 percent solution in 2-ethyl hexanol, a selective solvent for the midblock. We have explored two different experimental geometries including a hemispherical rigid indenter of glass pressed into a gel layer of varying thicknesses, and a soft, gel cap in contact with a rigid polymer surface. By simultaneously measuring the applied load, displacement between the two bodies, and contact area during loading cycles, we are able to employ a linearly elastic fracture mechanics analysis to obtain estimates of the gel's modulus over a range of polymer concentrations, and G, the energy release rate.

Doping Li and K into Na2ZrO3 Sorbent to Improve Its CO2 Capture Capability

NASA Astrophysics Data System (ADS)

Duan, Yuhua

Carbon dioxide is one of the major combustion products which once released into the air can contribute to global climate change. Solid sorbents have been reported in several previous studies to be promising candidates for CO2 sorbent applications due to their high CO2 absorption capacities at moderate working temperatures. However, at a given CO2 pressure, the turnover temperature (Tt) of an individual solid capture CO2 reaction is fixed and may be outside the operating temperature range (ΔTo) for a particularly capture technology. In order to shift such Tt for a solid into the range of ΔTo, its corresponding thermodynamic property must be changed by changing its structure by reacting (mixing) with other materials or doping with other elements. As an example, by combining thermodynamic database searching with ab initio thermodynamics calculations, in this work, we explored the Li- and K-doping effects on the Tt shifts of Na2ZrO3 at different doping levels. The obtained results showed that compared to pure Na2ZrO3, the Li- and K-doped mixtures Na2-αMαZrO3 (M =Li, K) have lower Tt and higher CO2 capture capacities.

The effect of reduced gravity on cryogenic nitrogen boiling and pipe chilldown.

PubMed

Darr, Samuel; Dong, Jun; Glikin, Neil; Hartwig, Jason; Majumdar, Alok; Leclair, Andre; Chung, Jacob

2016-01-01

Manned deep space exploration will require cryogenic in-space propulsion. Yet, accurate prediction of cryogenic pipe flow boiling heat transfer is lacking, due to the absence of a cohesive reduced gravity data set covering the expected flow and thermodynamic parameter ranges needed to validate cryogenic two-phase heat transfer models. This work provides a wide range of cryogenic chilldown data aboard an aircraft flying parabolic trajectories to simulate reduced gravity. Liquid nitrogen is used to quench a 1.27 cm diameter tube from room temperature. The pressure, temperature, flow rate, and inlet conditions are reported from 10 tests covering liquid Reynolds number from 2,000 to 80,000 and pressures from 80 to 810 kPa. Corresponding terrestrial gravity tests were performed in upward, downward, and horizontal flow configurations to identify gravity and flow direction effects on chilldown. Film boiling heat transfer was lessened by up to 25% in reduced gravity, resulting in longer time and more liquid to quench the pipe to liquid temperatures. Heat transfer was enhanced by increasing the flow rate, and differences between reduced and terrestrial gravity diminished at high flow rates. The new data set will enable the development of accurate and robust heat transfer models of cryogenic pipe chilldown in reduced gravity.

Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries

DOE PAGES

Meng, Xiangbo; Cao, Yanqiang; Libera, Joseph A.; ...

2017-10-01

This work describes the synthesis of aluminum sulfide (AlS x) thin films by atomic layer deposition (ALD) using tris(dimethylamido)aluminum and hydrogen sulfide. We employed a suite of in situ measurement techniques to explore the ALD AlS x growth mechanism, including quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy. A variety of ex situ characterization techniques were used to determine the growth characteristics, morphology, elemental composition, and crystallinity of the resultant AlS x films. This study revealed that the AlS x growth was self-limiting in the temperature range 100–250 °C, and the growth per cycle decreased linearly withmore » increasing temperature from ~0.45 Å/cycle at 100 °C to ~0.1 Å/cycle at 250 °C. The AlSx films were amorphous in this temperature range. We conducted electrochemical testing to evaluate the ALD AlS x as a potential anode material for lithium-ion batteries (LIBs). Finally, the ALD AlS x exhibited reliable cyclability over 60 discharge–charge cycles with a sustainable discharge capacity of 640 mAh/g at a current density of 100 mA/g in the voltage window of 0.6–3.5 V.« less

The effect of reduced gravity on cryogenic nitrogen boiling and pipe chilldown

PubMed Central

Darr, Samuel; Dong, Jun; Glikin, Neil; Hartwig, Jason; Majumdar, Alok; Leclair, Andre; Chung, Jacob

2016-01-01

Manned deep space exploration will require cryogenic in-space propulsion. Yet, accurate prediction of cryogenic pipe flow boiling heat transfer is lacking, due to the absence of a cohesive reduced gravity data set covering the expected flow and thermodynamic parameter ranges needed to validate cryogenic two-phase heat transfer models. This work provides a wide range of cryogenic chilldown data aboard an aircraft flying parabolic trajectories to simulate reduced gravity. Liquid nitrogen is used to quench a 1.27 cm diameter tube from room temperature. The pressure, temperature, flow rate, and inlet conditions are reported from 10 tests covering liquid Reynolds number from 2,000 to 80,000 and pressures from 80 to 810 kPa. Corresponding terrestrial gravity tests were performed in upward, downward, and horizontal flow configurations to identify gravity and flow direction effects on chilldown. Film boiling heat transfer was lessened by up to 25% in reduced gravity, resulting in longer time and more liquid to quench the pipe to liquid temperatures. Heat transfer was enhanced by increasing the flow rate, and differences between reduced and terrestrial gravity diminished at high flow rates. The new data set will enable the development of accurate and robust heat transfer models of cryogenic pipe chilldown in reduced gravity. PMID:28725740

A Continuous Culture System for Assessing Microbial Activities in the Piezosphere

PubMed Central

Pérez-Rodríguez, Ileana

2015-01-01

Continuous culture under elevated pressures is an important technique for expanding the exploration of microbial growth and survival in extreme environments associated with the deep biosphere. Here we present a benchtop stirred continuous culture bioreactor capable of withstanding temperatures ranging from 25 to 120°C and pressures as high as 69 MPa. The system is configured to allow the employment of media enriched in dissolved gases, under oxic or anoxic conditions, while permitting periodic sampling of the incubated organisms with minimal physical/chemical disturbance inside the reactor. In a pilot experiment, the fermentative growth of the thermopiezophilic bacterium Marinitoga piezophila was investigated continuously for 382 h at 65°C and at pressures ranging from 0.1 to 40 MPa while the medium flow rate was varied from 2 to 0.025 ml/min. The enhanced growth observed at 30 and 40 MPa and 0.025 ml/min supports the pressure preferences of M. piezophila when grown fermentatively. This assay successfully demonstrates the capabilities of the bioreactor for continuous culturing at a variety of dilution rates, pressures, and temperatures. We anticipate that this technology will accelerate our understanding of the physiological and metabolic status of microorganisms under temperature, pressure, and energy regimes resembling those of the Earth's piezosphere. PMID:26209666

Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Xiangbo; Cao, Yanqiang; Libera, Joseph A.

This work describes the synthesis of aluminum sulfide (AlS x) thin films by atomic layer deposition (ALD) using tris(dimethylamido)aluminum and hydrogen sulfide. We employed a suite of in situ measurement techniques to explore the ALD AlS x growth mechanism, including quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy. A variety of ex situ characterization techniques were used to determine the growth characteristics, morphology, elemental composition, and crystallinity of the resultant AlS x films. This study revealed that the AlS x growth was self-limiting in the temperature range 100–250 °C, and the growth per cycle decreased linearly withmore » increasing temperature from ~0.45 Å/cycle at 100 °C to ~0.1 Å/cycle at 250 °C. The AlSx films were amorphous in this temperature range. We conducted electrochemical testing to evaluate the ALD AlS x as a potential anode material for lithium-ion batteries (LIBs). Finally, the ALD AlS x exhibited reliable cyclability over 60 discharge–charge cycles with a sustainable discharge capacity of 640 mAh/g at a current density of 100 mA/g in the voltage window of 0.6–3.5 V.« less

Assessment of Operation of EMK21 MEMS Silicon Oscillator Over Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2009-01-01

Electronic control systems, data-acquisition instrumentation, and microprocessors require accurate timing signals for proper operation. Traditionally, ceramic resonators and crystal oscillators provided this clock function for the majority of these systems. Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to surface as commercial-off-the-shelf (COTS) parts by a few companies. These quartz-free, miniature silicon devices could easily replace the traditional crystal oscillators in providing the timing/clock function for many digital and analog circuits. They are reported to provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [ 1-2]. In addition, they are encapsulated in compact lead-free packages and cover a wide frequency range (1 MHz to 125 MHz). The small size of the MEMS oscillators along with their thermal stability make them ideal candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an Ecliptek Corporation MEMS silicon oscillator chip under extreme temperatures.

Optimal Electrocatalytic Pd/MWNTs Nanocatalysts toward Formic Acid Oxidation

PubMed Central

Wang, Yiran; He, Qingliang; Wei, Huige; Guo, Jiang; Ding, Keqiang; Wang, Qiang; Wang, Zhe; Wei, Suying; Guo, Zhanhu

2017-01-01

The operating conditions such as composition of electrolyte and temperature can greatly influence the formic acid (HCOOH) oxidation reaction (FAOR). Palladium decorated multi-walled carbon nanotubes (Pd/MWNTs) were successfully synthesized and employed as nanocatalysts to explore the effects of formic acid, sulfuric acid (H2SO4) concentration and temperature on FAOR. Both the hydrogen adsorption in low potential range and the oxidation of poisoning species during the high potential range in cyclic voltammetry were demonstrated to contribute to the enhanced electroactivity of Pd/MWNTs. The as-synthesized Pd/MWNTs gave the best performance under a condition with balanced adsorptions of HCOOH and H2SO4 molecules. The dominant dehydrogenation pathway on Pd/MWNTs can be largely depressed by the increased dehydration pathway, leading to an increased charge transfer resistance (Rct). Increasing HCOOH concentration could directly increase the dehydration process proportion and cause the production of COads species. H2SO4 as donor of H+ greatly facilitated the onset oxidation of HCOOH in the beginning process but it largely depressed the HCOOH oxidation with excess amount of H+. Enhanced ion mobility with increasing the temperature was mainly responsible for the increased current densities, improved tolerance stabilities and reduced Rct values, while dehydration process was also increased simultaneously. PMID:29622817

Filled and Unfilled Temperature-Dependent Epoxy Resin Blends for Lossy Transducer Substrates

PubMed Central

Eames, Matthew D.C.; Hossack, John A.

2016-01-01

In the context of our ongoing investigation of low-cost 2-dimensional (2-D) arrays, we studied the temperature-dependent acoustic properties of epoxy blends that could serve as an acoustically lossy backing material in compact 2-D array-based devices. This material should be capable of being machined during array manufacture, while also providing adequate signal attenuation to mitigate backing block reverberation artifacts. The acoustic impedance and attenuation of 5 unfilled epoxy blends and 2 filled epoxy blends—tungsten and fiberglass fillers—were analyzed across a 35°C temperature range in 5°C increments. Unfilled epoxy materials possessed an approximately linear variation of impedance and sigmoidal variation of attenuation properties over the range of temperatures of interest. An intermediate epoxy blend was fitted to a quadratic trend line with R2 values of 0.94 and 0.99 for attenuation and impedance, respectively. It was observed that a fiberglass filler induces a strong quadratic trend in the impedance data with temperature, which results in increased error in the characterization of attenuation and impedance. The tungsten-filled epoxy was not susceptible to such problems because a different method of fabrication was required. At body temperature, the tungsten-filled epoxy could provide a 44 dB attenuation of the round-trip backing block echo in our application, in which the center frequency is 5 MHz and the backing material is 1.1 mm thick. This is an 11 dB increase in attenuation compared with the fiberglass-filled epoxy in the context of our application. This work provides motivation for exploring the use of custom-made tungsten-filled epoxy materials as a substitute PCB-based substrate to provide electrical signal interconnect. PMID:19406716

A Library of ATMO Forward Model Transmission Spectra for Hot Jupiter Exoplanets

NASA Technical Reports Server (NTRS)

Goyal, Jayesh M.; Mayne, Nathan; Sing, David K.; Drummond, Benjamin; Tremblin, Pascal; Amundsen, David S.; Evans, Thomas; Carter, Aarynn L.; Spake, Jessica; Baraffe, Isabelle;

A library of ATMO forward model transmission spectra for hot Jupiter exoplanets

NASA Astrophysics Data System (ADS)

Goyal, Jayesh M.; Mayne, Nathan; Sing, David K.; Drummond, Benjamin; Tremblin, Pascal; Amundsen, David S.; Evans, Thomas; Carter, Aarynn L.; Spake, Jessica; Baraffe, Isabelle; Nikolov, Nikolay; Manners, James; Chabrier, Gilles; Hebrard, Eric

2018-03-01

We present a grid of forward model transmission spectra, adopting an isothermal temperature-pressure profile, alongside corresponding equilibrium chemical abundances for 117 observationally significant hot exoplanets (equilibrium temperatures of 547-2710 K). This model grid has been developed using a 1D radiative-convective-chemical equilibrium model termed ATMO, with up-to-date high-temperature opacities. We present an interpretation of observations of 10 exoplanets, including best-fitting parameters and χ2 maps. In agreement with previous works, we find a continuum from clear to hazy/cloudy atmospheres for this sample of hot Jupiters. The data for all the 10 planets are consistent with subsolar to solar C/O ratio, 0.005 to 10 times solar metallicity and water rather than methane-dominated infrared spectra. We then explore the range of simulated atmospheric spectra for different exoplanets, based on characteristics such as temperature, metallicity, C/O ratio, haziness and cloudiness. We find a transition value for the metallicity between 10 and 50 times solar, which leads to substantial changes in the transmission spectra. We also find a transition value of C/O ratio, from water to carbon species dominated infrared spectra, as found by previous works, revealing a temperature dependence of this transition point ranging from ˜0.56 to ˜1-1.3 for equilibrium temperatures from ˜900 to ˜2600 K. We highlight the potential of the spectral features of HCN and C2H2 to constrain the metallicities and C/O ratios of planets, using James Webb Space Telescope (JWST) observations. Finally, our entire grid (˜460 000 simulations) is publicly available and can be used directly with the JWST simulator PandExo for planning observations.

Coverage-Dependent Anchoring of 4,4'-Biphenyl Dicarboxylic Acid to CoO(111) Thin Films.

PubMed

Mohr, Susanne; Schmitt, Tobias; Döpper, Tibor; Xiang, Feifei; Schwarz, Matthias; Görling, Andreas; Schneider, M Alexander; Libuda, Jörg

2017-05-02

We investigated the adsorption behavior of 4,4'-biphenhyl dicarboxylic acid (BDA) on well-ordered CoO(111) films grown on Ir(100) as a function of coverage and temperature using time-resolved and temperature-programmed infrared reflection absorption spectroscopy (TR-IRAS, TP-IRAS) in combination with density functional theory (DFT) and scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions. To compare the binding behavior of BDA as a function of the oxide film thickness, three different CoO(111) film thicknesses were explored: films of about 20 bilayers (BLs) (approximately 5 nm), 2 BLs, and 1 BL. The two carboxylic acid groups of BDA offer two potential anchoring points to the oxide surface. At 150 K, intact BDA adsorbs on 20 BL thick oxide films in planar geometry with the phenyl rings aligned parallel to the surface. With decreasing oxide film thickness, we observe an increasing tendency for deprotonation and the formation of flat-lying BDA molecules anchored as dicarboxylates. After saturation of the first monolayer, intact BDA multilayers grow with molecules aligned parallel to the surface. The BDA multilayer desorbs at around 360 K. Completely different growth behavior is observed if BDA is deposited above the multilayer desorption temperature. Initially, doubly deprotonated dicarboxylates are formed by adopting a flat-lying orientation. With increasing exposure, however, the adsorbate layer transforms into upright standing monocarboxylates. A sharp OH stretching band (3584 cm -1 ) and a blue-shifted CO stretching band (1759 cm -1 ) indicate weakly interacting apical carboxylic acid groups at the vacuum interface. The anchored monocarboxylate phase slowly desorbs in a temperature range of up to 470 K. At higher temperature, a flat-lying doubly deprotonated BDA is formed, which desorbs and decomposes in a temperature range of up to 600 K.

Conducting processes in simulated chronic inflammatory demyelinating polyneuropathy at 20°C-42°C.

PubMed

Stephanova, D I; Daskalova, M; Mladenov, M

2015-03-01

Decreased conducting processes leading usually to conduction block and increased weakness of limbs during cold (cold paresis) or warmth (heat paresis) have been reported in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). To explore the mechanisms of these symptoms, the effects of temperature (from 20°C to 42°C) on nodal action potentials and their current kinetics in previously simulated case of 70% CIDP are investigated, using our temperature dependent multi-layered model of the myelinated human motor nerve fiber. The results show that potential amplitudes have a bifid form at 20°C. As in the normal case, for the CIDP case, the nodal action potentials are determined mainly by the nodal sodium currents (I Na ) for the temperature range of 20-39°C, as the contribution of nodal fast and slow potassium currents (I Kf and I Ks ) to the total ionic current (Ii) is negligible. Also, the contribution of I Kf and I Ks to the membrane repolarization is enhanced at temperatures higher than 39°C. However, in the temperature range of 20-42°C, all potential parameters in the CIDP case, except for the conduction block during hyperthermia (≥ 40°C) which is again at 45°C, worsen: (i) conduction velocities and potential amplitudes are decreased; (ii) afterpotentials and threshold stimulus currents for the potential generation are increased; (iii) the current kinetics of action potentials is slowed and (iv) the conduction block during hypothermia (≤ 25°C) is at temperatures lower than 20°C. These potential parameters are more altered during hyperthermia and are most altered during hypothermia. The present results suggest that the conducting processes in patients with CIDP are in higher risk during hypothermia than hyperthermia.

Microsystems, Space Qualified Electronics and Mobile Sensor Platforms for Harsh Environment Applications and Planetary Exploration

NASA Technical Reports Server (NTRS)

Hunter, Gary W.; Okojie, Robert S.; Krasowski, Michael J.; Beheim, Glenn M.; Fralick, Gustave C.; Wrbanek, John D.; Greenberg, Paul S.; Xu, Jennifer

2007-01-01

NASA Glenn Research Center is presently developing and applying a range of sensor and electronic technologies that can enable future planetary missions. These include space qualified instruments and electronics, high temperature sensors for Venus missions, mobile sensor platforms, and Microsystems for detection of a range of chemical species and particulates. A discussion of each technology area and its level of maturity is given. It is concluded that there is a strong need for low power devices which can be mobile and provide substantial characterization of the planetary environment where and when needed. While a given mission will require tailoring of the technology for the application, basic tools which can enable new planetary missions are being developed.

Dielectric relaxation spectroscopy of aqueous solutions of diclofenac potassium over the frequency range of 20 Hz to 2 MHz at 303.15 K temperature

NASA Astrophysics Data System (ADS)

Karakthala, J. B.; Vankar, H. P.; Rana, V. A.

2018-05-01

The complex relative dielectric function ɛ*(ω) = ɛ' - jɛ″ of aqueous solutions of diclofenac potassium (DK) in the frequency range 20 Hz to 2 MHz at 303.15 K was measured using a precision LCR meter. The electrical/dielectric properties of the solutions samples were represented in terms of complex relative dielectric function ɛ*(ω) real part σ'(ω) of complex ac conductivity and dc conductivity. These types of studies can be used to explore various mechanism contributed in the absorption, transportation of drug through tissues and membranes of body as well as interactions of drug with body fluid and blood plasma.

Thermal algebraic-decay charge liquid driven by competing short-range Coulomb repulsion

NASA Astrophysics Data System (ADS)

Kaneko, Ryui; Nonomura, Yoshihiko; Kohno, Masanori

2018-05-01

We explore the possibility of a Berezinskii-Kosterlitz-Thouless-like critical phase for the charge degrees of freedom in the intermediate-temperature regime between the charge-ordered and disordered phases in two-dimensional systems with competing short-range Coulomb repulsion. As the simplest example, we investigate the extended Hubbard model with on-site and nearest-neighbor Coulomb interactions on a triangular lattice at half filling in the atomic limit by using a classical Monte Carlo method, and find a critical phase, characterized by algebraic decay of the charge correlation function, belonging to the universality class of the two-dimensional XY model with a Z6 anisotropy. Based on the results, we discuss possible conditions for the critical phase in materials.

Heterogeneous Interactions of Acetaldehyde and Sulfuric Acid

NASA Technical Reports Server (NTRS)

Michelsen, R. R.; Ashbourn, S. F. M.; Iraci, L. T.

2004-01-01

The uptake of acetaldehyde [CH3CHO] by aqueous sulfuric acid has been studied via Knudsen cell experiments over ranges of temperature (210-250 K) and acid concentration (40-80 wt. %) representative of the upper troposphere. The Henry's law constants for acetaldehyde calculated from these data range from 6 x 10(exp 2) M/atm for 40 wt. % H2SO4 at 228 K to 2 x 10(exp 5) M/atm for 80 wt. % H2SO4 at 212 K. In some instances, acetaldehyde uptake exhibits apparent steady-state loss. The possible sources of this behavior, including polymerization, will be explored. Furthermore, the implications for heterogeneous reactions of aldehydes in sulfate aerosols in the upper troposphere will be discussed.

From Parasite Encounter to Infection: Multiple-Scale Drivers of Parasite Richness in a Wild Social Primate Population

NASA Technical Reports Server (NTRS)

Benavides J. A.; Huchard, E.; Pettorelli, N.; King, A. J.; Brown, M. E.; Archer, C. E.; Appleton, C. C.; Raymond, M.; Cowlishaw, G.

2011-01-01

Host parasite diversity plays a fundamental role in ecological and evolutionary processes, yet the factors that drive it are still poorly understood. A variety of processes, operating across a range of spatial scales, are likely to influence both the probability of parasite encounter and subsequent infection. Here, we explored eight possible determinants of parasite richness, comprising rainfall and temperature at the population level, ranging behavior and home range productivity at the group level, and age, sex, body condition, and social rank at the individual level. We used a unique dataset describing gastrointestinal parasites in a terrestrial subtropical vertebrate (chacma baboons, Papio ursinus), comprising 662 faecal samples from 86 individuals representing all age-sex classes across two groups over two dry seasons in a desert population. Three mixed models were used to identify the most important factor at each of the three spatial scales (population, group, individual); these were then standardised and combined in a single, global, mixed model. Individual age had the strongest influence on parasite richness, in a convex relationship. Parasite richness was also higher in females and animals in poor condition, albeit at a lower order of magnitude than age. Finally, with a further halving of effect size, parasite richness was positively correlated to day range and temperature. These findings indicate that a range of factors influence host parasite richness through both encounter and infection probabilities, but that individual-level processes may be more important than those at the group or population level.

DETERMINATION OF THE CREEP–FATIGUE INTERACTION DIAGRAM FOR ALLOY 617

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, J. K.; Carroll, L. J.; Sham, T. -L.

Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor. To evaluate the behavior of this material in the expected service conditions, creep-fatigue testing was performed. Testing has been performed primarily on a single heat of material at 850 and 950°C for total strain ranges of 0.3 to 1% and tensile hold times as long as 240 minutes. At 850°C, increases in the tensile hold duration degraded the creep fatigue resistance, at least to the investigated strain-controlled hold time of up to 60 minutes at the 0.3% strain range and 240 minutesmore » at the 1.0% strain range. At 950°C, the creep-fatigue cycles to failure becomes constant with increasing hold times, indicating saturation occurs at relatively short hold times. The creep and fatigue damage fractions have been calculated and plotted on a creep-fatigue interaction D-diagram. Results from earlier creep-fatigue tests at 800 and 1000°C on an additional heat of Alloy 617 are also plotted on the D-diagram. The methodology for calculating the damage fractions will be presented, and the effects of strain rate, strain range, temperature, hold time, and strain profile (i.e. holds in tension, compression or both) on the creep-fatigue damage will be explored.« less

Exploring the Effect of Media, Salinity and Clay on the Thermoelectric Coupling Coefficient in Self-Potential Data

NASA Astrophysics Data System (ADS)

Meyer, C. D.; Revil, A.

2014-12-01

Self-potential is a non-invasive, passive geophysical technique with applications ranging from imaging oil and gas reservoirs to identifying preferential flow paths in earthen embankments. Several cross-coupled flow phenomena contribute to self-potential data, and there is a need to further quantify these various sources to enable better resolution and quantification of self-potential models. Very little research has been done to constrain thermoelectric source mechanisms that contribute to self-potential signals. A laboratory experiment has been designed to investigate the thermoelectric coupling coefficient (CTE) that relates the voltage change per degree centigrade (V/°C) in porous media. This study focuses on a sand tank experiment using a saturated silica sand. To isolate the temperature gradient dependence of self-potential measurements, no hydraulic gradient is applied to the tank, eliminating the streaming potential component of source current. Self-potential and temperature data are recorded while reservoirs of hot and cold water are established on opposite ends of the tank in order to generate thermoelectric source currents. Various thermal gradients ranging from 0 °C to 80 °C over 20 cm are examined for various salinities (10-3M- 1M NaCl), sand grain sizes and clay content to investigate influences on CTE. A short-duration contact of non-polarizing (Pb/PbCl) electrodes is implemented to minimize temperature drift of electrodes during the experiment. Surface self-potential and temperature measurements are made in 30 minute intervals. Initial measurements have revealed non-linear effects, including a decreased CTE as temperature gradient bounds approach 0 °C.

Epitaxial Growth and Cracking Mechanisms of Thermally Sprayed Ceramic Splats

NASA Astrophysics Data System (ADS)

Chen, Lin; Yang, Guan-jun

2018-02-01

In the present study, the epitaxial growth and cracking mechanisms of thermally sprayed ceramic splats were explored. We report, for the first time, the epitaxial growth of various splat/substrate combinations at low substrate temperatures (100 °C) and large lattice mismatch (- 11.26%). Our results suggest that thermal spray deposition was essentially a liquid-phase epitaxy, readily forming chemical bonding. The interface temperature was also estimated. The results convincingly demonstrated that atoms only need to diffuse and rearrange over a sufficiently short range during extremely rapid solidification. Concurrently, severe cracking occurred in the epitaxial splat/substrate systems, which indicated high tensile stress was produced during splat deposition. The origin of the tensile stress was attributed to the strong constraint of the locally heated substrate by its cold surroundings.

El Chichon and 'mystery cloud' aerosols between 30 and 55 km Global observations from the SME visible spectrometer

NASA Astrophysics Data System (ADS)

Clancy, R. T.

1986-09-01

Visible limb radiances measured by the Solar Mesosphere Explorer (SME) are used to obtain volume scattering ratios for aerosol loading in the 30-55 km altitude range of the stratosphere. Global maps of these ratios are presented for the period January 1982 to August 1984. Significant aerosol scattering from the 'mystery cloud' and El Chichon aerosol layers are found above 30 km. A timescale of approximately 2 months between the appearance of the aerosol at 30.5 km and at 37.5 km is consistent with vertical transport of aerosol or vapor by eddy diffusion above 30 km. An anticorrelation exists between aerosol scattering and stratospheric temperatures. Periods of lower stratospheric temperatures may account for the formation of aerosol between 40 and 55 km altitude.

El Chichon and 'mystery cloud' aerosols between 30 and 55 km Global observations from the SME visible spectrometer

NASA Technical Reports Server (NTRS)

Clancy, R. T.

1986-01-01

Visible limb radiances measured by the Solar Mesosphere Explorer (SME) are used to obtain volume scattering ratios for aerosol loading in the 30-55 km altitude range of the stratosphere. Global maps of these ratios are presented for the period January 1982 to August 1984. Significant aerosol scattering from the 'mystery cloud' and El Chichon aerosol layers are found above 30 km. A timescale of approximately 2 months between the appearance of the aerosol at 30.5 km and at 37.5 km is consistent with vertical transport of aerosol or vapor by eddy diffusion above 30 km. An anticorrelation exists between aerosol scattering and stratospheric temperatures. Periods of lower stratospheric temperatures may account for the formation of aerosol between 40 and 55 km altitude.

Gusev Crater

NASA Image and Video Library

2003-03-13

This mosaic of daytime infrared images of Gusev Crater, taken by NASA Mars Odyssey spacecraft, has been draped over topography data obtained by NASA Mars Global Surveyor. The daytime temperatures range from approximately minus 45 degrees C (black) to minus 5 degrees C (white). The temperature differences in these daytime images are due primarily to lighting effects, where sunlit slopes are warm (bright) and shadowed slopes are cool (dark). Gusev crater is a potential landing site for the Mars Exploration Rovers. The large ancient river channel of Ma'Adim that once flowed into Gusev can be seen at the top of the mosaic. This image mosaic covers an area approximately 180 kilometers (110 miles) on each side centered near 14 degrees S, 175 degrees E, looking toward the south in this simulated view. http://photojournal.jpl.nasa.gov/catalog/PIA04260

Characterizing the Atmosphere of a Young Planet

NASA Technical Reports Server (NTRS)

Marley, Mark

2016-01-01

Since the discovery of the young, directly imaged planet 51 Eri b, its emergent spectrum has proved challenging to interpret. The initial discovery paper (Macintosh et al. 2015) interpreted the spectrum as indicative of a low mass (few Jupiter masses), effective temperature near 700 degrees Kelvin, and partial cloudiness. Subsequent observations in the K band, however, seem to invalidate the early models. In addition, newly improved photochemical data point to the likely presence of exotic haze species in the atmosphere. In my presentation I will explore the photochemistry of the atmosphere and discuss whether disequilibrium chemistry, hazes, clouds, or non-solar abundances of heavy elements may be responsible for the unusual spectrum of this planet. The implications for the interpretation of other young Jupiters in this mass and effective temperature range will also be considered.

Erroneous Arrhenius: Modified Arrhenius model best explains the temperature dependence of ectotherm fitness

PubMed Central

Knies, Jennifer L.; Kingsolver, Joel G.

2013-01-01

The initial rise of fitness that occurs with increasing temperature is attributed to Arrhenius kinetics, in which rates of reaction increase exponentially with increasing temperature. Models based on Arrhenius typically assume single rate-limiting reaction(s) over some physiological temperature range for which all the rate-limiting enzymes are in 100% active conformation. We test this assumption using datasets for microbes that have measurements of fitness (intrinsic rate of population growth) at many temperatures and over a broad temperature range, and for diverse ectotherms that have measurements at fewer temperatures. When measurements are available at many temperatures, strictly Arrhenius kinetics is rejected over the physiological temperature range. However, over a narrower temperature range, we cannot reject strictly Arrhenius kinetics. The temperature range also affects estimates of the temperature dependence of fitness. These results indicate that Arrhenius kinetics only apply over a narrow range of temperatures for ectotherms, complicating attempts to identify general patterns of temperature dependence. PMID:20528477

Erroneous Arrhenius: modified arrhenius model best explains the temperature dependence of ectotherm fitness.

PubMed

Knies, Jennifer L; Kingsolver, Joel G

2010-08-01

The initial rise of fitness that occurs with increasing temperature is attributed to Arrhenius kinetics, in which rates of reaction increase exponentially with increasing temperature. Models based on Arrhenius typically assume single rate-limiting reactions over some physiological temperature range for which all the rate-limiting enzymes are in 100% active conformation. We test this assumption using data sets for microbes that have measurements of fitness (intrinsic rate of population growth) at many temperatures and over a broad temperature range and for diverse ectotherms that have measurements at fewer temperatures. When measurements are available at many temperatures, strictly Arrhenius kinetics are rejected over the physiological temperature range. However, over a narrower temperature range, we cannot reject strictly Arrhenius kinetics. The temperature range also affects estimates of the temperature dependence of fitness. These results indicate that Arrhenius kinetics only apply over a narrow range of temperatures for ectotherms, complicating attempts to identify general patterns of temperature dependence.

Spectroscopy of Exoplanet Atmospheres with the FINESSE Explorer

NASA Technical Reports Server (NTRS)

Deroo, Pieter; Swain, Mark R.; Green, Robert O.

2012-01-01

FINESSE (Fast INfrared Exoplanet Spectroscopic Survey Explorer) will provide uniquely detailed information on the growing number of newly discovered planets by characterizing their atmospheric composition and temperature structure. This NASA Explorer mission, selected for a competitive Phase A study, is unique in its breath and scope thanks to broad instantaneous spectroscopy from the optical to the mid-IR (0.7 - 5 micron), with a survey of exoplanets measured in a consistent, uniform way. For 200 transiting exoplanets ranging from Terrestrial to Jovians, FINESSE will measure the chemical composition and temperature structure of their atmospheres and trace changes over time with exoplanet longitude. The mission will do so by measuring the spectroscopic time series for a primary and secondary eclipse over the exoplanet orbital phase curve. With spectrophotometric precision being a key enabling aspect for combined light exoplanet characterization, FINESSE is designed to produce spectrophotometric precision of better than 100 parts-per-million per spectral channel without the need for decorrelation. The exceptional stability of FINESSE will even allow the mission to characterize non-transiting planets, potentially as part of FINESSE's Participating Scientist Program. In this paper, we discuss the flow down from the target availability to observations and scheduling to the analysis and calibration of the data and how it enables FINESSE to be the mission that will truly expand the new field of comparative exoplanetology.

2005 NASA Seal/Secondary Air System Workshop, Volume 1

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Editor); Hendricks, Robert C. (Editor)

2006-01-01

The 2005 NASA Seal/Secondary Air System workshop covered the following topics: (i) Overview of NASA s new Exploration Initiative program aimed at exploring the Moon, Mars, and beyond; (ii) Overview of the NASA-sponsored Propulsion 21 Project; (iii) Overview of NASA Glenn s seal project aimed at developing advanced seals for NASA s turbomachinery, space, and reentry vehicle needs; (iv) Reviews of NASA prime contractor, vendor, and university advanced sealing concepts including tip clearance control, test results, experimental facilities, and numerical predictions; and (v) Reviews of material development programs relevant to advanced seals development. Turbine engine studies have shown that reducing high-pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin, and increase range. Several organizations presented development efforts aimed at developing faster clearance control systems and associated technology to meet future engine needs. The workshop also covered several programs NASA is funding to develop technologies for the Exploration Initiative and advanced reusable space vehicle technologies. NASA plans on developing an advanced docking and berthing system that would permit any vehicle to dock to any on-orbit station or vehicle. Seal technical challenges (including space environments, temperature variation, and seal-on-seal operation) as well as plans to develop the necessary "androgynous" seal technologies were reviewed. Researchers also reviewed tests completed for the shuttle main landing gear door seals.

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

NASA Astrophysics Data System (ADS)

Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

2018-05-01

Recent X-ray observations of merger shocks in galaxy clusters have shown that the post-shock plasma is two-temperature, with the protons being hotter than the electrons. In this work, the second of a series, we investigate the efficiency of irreversible electron heating in perpendicular low Mach number shocks, by means of two-dimensional particle-in-cell simulations. We consider values of plasma beta (the ratio of thermal and magnetic pressures) in the range 4 ≲ β p0 ≲ 32, and sonic Mach number (the ratio of shock speed to pre-shock sound speed) in the range 2 ≲ M s ≲ 5, as appropriate for galaxy cluster shocks. As shown in Paper I, magnetic field amplification—induced by shock compression of the pre-shock field, or by strong proton cyclotron and mirror modes accompanying the relaxation of proton temperature anisotropy—can drive the electron temperature anisotropy beyond the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance, and allows for efficient entropy production. We find that the post-shock electron temperature T e2 exceeds the adiabatic expectation {T}e2,{ad} by an amount ({T}e2-{T}e2,{ad})/{T}e0≃ 0.044 {M}s({M}s-1) (here, T e0 is the pre-shock temperature), which depends only weakly on the plasma beta over the range 4 ≲ β p0 ≲ 32 that we have explored, as well as on the proton-to-electron mass ratio (the coefficient of ≃0.044 is measured for our fiducial {m}i/{m}e=49, and we estimate that it will decrease to ≃0.03 for the realistic mass ratio). Our results have important implications for current and future observations of galaxy cluster shocks in the radio band (synchrotron emission and Sunyaev–Zel’dovich effect) and at X-ray frequencies.

The structure-property relationships of powder processed Fe-Al-Si alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prichard, Paul D.

1998-02-23

Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) processmore » to obtain a high fraction of metal injection molding (MIM) quality powder (D 84 < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO 3 structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.« less

GeSn growth kinetics in reduced pressure chemical vapor deposition from Ge2H6 and SnCl4

NASA Astrophysics Data System (ADS)

Aubin, J.; Hartmann, J. M.

2018-01-01

We have investigated the low temperature epitaxy of high Sn content GeSn alloys in a 200 mm industrial Reduced Pressure - Chemical Vapor Deposition tool from Applied Materials. Gaseous digermane (Ge2H6) and liquid tin tetrachloride (SnCl4) were used as the Ge and Sn precursors, respectively. The impact of temperature (in the 300-350 °C range), Ge2H6 and SnCl4 mass-flows on the GeSn growth kinetics at 100 Torr has been thoroughly explored. Be it at 300 °C or 325 °C, a linear GeSn growth rate increase together with a sub-linear Sn concentration increase occurred as the SnCl4 mass-flow increased, irrespective of the Ge2H6 mass flow (fixed or varying). The Sn atoms seemed to catalyze H desorption from the surface, resulting in higher GeSn growth rates for high SnCl4 mass-flows (in the 4-21 nm min-1 range). The evolution of the Sn content x with the F (SnCl4) 2 ·/F (Ge2H6) mass-flow ratio was fitted by x2/(1 - x) = n ·F (SnCl4) 2 ·/F (Ge2H6), with n = 0.25 (325 °C) and 0.60 (300 °C). We have otherwise studied the impact of temperature, in the 300-350 °C range, on the GeSn growth kinetics. The GeSn growth rate exponentially increased with the temperature, from 15 up to 32 nm min-1. The associated activation energy was low, i.e. Ea = 10 kcal mol-1. Meanwhile, the Sn content decreased linearly as the growth temperature increased, from 15% at 300 °C down to 6% at 350 °C.

A comparison of temporal artery thermometers with internal blood monitors to measure body temperature during hemodialysis.

PubMed

Lunney, Meaghan; Tonelli, Bronwyn; Lewis, Rachel; Wiebe, Natasha; Thomas, Chandra; MacRae, Jennifer; Tonelli, Marcello

2018-06-14

Thermometers that measure core (internal) body temperature are the gold standard for monitoring temperature. Despite that most modern hemodialysis machines are equipped with an internal blood monitor that measures core body temperature, current practice is to use peripheral thermometers. A better understanding of how peripheral thermometers compare with the dialysis machine thermometer may help guide practice. The study followed a prospective cross-sectional design. Hemodialysis patients were recruited from 2 sites in Calgary, Alberta (April - June 2017). Body temperatures were obtained from peripheral (temporal artery) and dialysis machine thermometers concurrently. Paired t-tests, Bland-Altman plots, and quantile-quantile plots were used to compare measurements from the two devices and to explore potential factors affecting temperature in hemodialysis patients. The mean body temperature of 94 hemodialysis patients measured using the temporal artery thermometer (36.7 °C) was significantly different than the dialysis machine thermometer (36.4 °C); p < 0.001. The mean difference (0.27 °C) appeared to be consistent across average temperature (range: 35.8-37.3 °C). Temperature measured by the temporal artery thermometer was statistically and clinically higher than that measured by the dialysis machine thermometer. Using the dialysis machine to monitor body temperature may result in more accurate readings and is likely to reduce the purchasing and maintenance costs associated with manual temperature readings, as well as easing the workload for dialysis staff.

Exploring the importance of within-canopy spatial temperature variation on transpiration predictions

PubMed Central

Bauerle, William L.; Bowden, Joseph D.; Wang, G. Geoff; Shahba, Mohamed A.

2009-01-01

Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale in climatically contrasting genotypes of Acer rubrum L., cv. October Glory (OG) and Summer Red (SR). The effects of temperature acclimation on intracanopy gradients in transpiration over a range of realistic forest growth temperatures were also assessed by simulation. Physiological parameters were applied, with or without adjustment for temperature acclimation, to account for transpiration responses to growth temperature. Both types of parameterization were scaled up to stand transpiration (expressed per unit leaf area) with an individual tree model (MAESTRA) to assess how transpiration might be affected by spatial and temporal distributions of foliage properties. The MAESTRA model performed well, but its reproducibility was dependent on physiological parameters acclimated to daytime temperature. Concordance correlation coefficients between measured and predicted transpiration were higher (0.95 and 0.98 versus 0.87 and 0.96) when model parameters reflected acclimated growth temperature. In response to temperature increases, the southern genotype (SR) transpiration responded more than the northern (OG). Conditions of elevated long-term temperature acclimation further separate their transpiration differences. Results demonstrate the importance of accounting for leaf-level physiological adjustments that are sensitive to microclimate changes and the use of provenance-, ecotype-, and/or genotype-specific parameter sets, two components likely to improve the accuracy of site-level and ecosystem-level estimates of transpiration flux. PMID:19561047

Local structural aspects of metal-metal transition in IrTe2 from x-ray PDF

NASA Astrophysics Data System (ADS)

Yu, Runze; Abeykoon, Milinda; Zhou, Haidong; Yin, Weiguo; Bozin, Emil S.

Evolution of local atomic structure across the metal-metal transition in IrTe2 is explored by pair distribution function (PDF) analysis of x-ray total scattering data over 80 K

Phase diagram of a reentrant gel of patchy particles

NASA Astrophysics Data System (ADS)

Roldán-Vargas, Sándalo; Smallenburg, Frank; Kob, Walter; Sciortino, Francesco

2013-12-01

We study the phase diagram of a binary mixture of patchy particles which has been designed to form a reversible gel. For this we perform Monte Carlo and molecular dynamics simulations to investigate the thermodynamics of such a system and compare our numerical results with predictions based on the analytical parameter-free Wertheim theory. We explore a wide range of the temperature-density-composition space that defines the three-dimensional phase diagram of the system. As a result, we delimit the region of thermodynamic stability of the fluid. We find that for a large region of the phase diagram the Wertheim theory is able to give a quantitative description of the system. For higher densities, our simulations show that the system is crystallizing into a BCC structure. Finally, we study the relaxation dynamics of the system by means of the density and temperature dependences of the diffusion coefficient. We show that there exists a density range where the system passes reversibly from a gel to a fluid upon both heating and cooling, encountering neither demixing nor phase separation.

Electronic archival tags provide first glimpse of bathythermal habitat use by free-ranging adult lake sturgeon Acipenser fulvescens

USGS Publications Warehouse

Briggs, Andrew S.; Hondorp, Darryl W.; Quinlan, Henry R.; Boase, James C.; Mohr, Lloyd C.

2016-01-01

Information on lake sturgeon (Acipenser fulvescens) depth and thermal habitat use during non-spawning periods is unavailable due to the difficulty of observing lake sturgeon away from shallow water spawning sites. In 2002 and 2003, lake sturgeon captured in commercial trap nets near Sarnia, Ontario were implanted with archival tags and released back into southern Lake Huron. Five of the 40 tagged individuals were recaptured and were at large for 32, 57, 286, 301, and 880 days. Temperatures and depths recorded by archival tags ranged from 0 to 23.5 ºC and 0.1 to 42.4 m, respectively. For the three lake sturgeon that were at large for over 200 days, temperatures occupied emulated seasonal fluctuations. Two of these fish occupied deeper waters during winter than summer while the other occupied similar depths during non-spawning periods. This study provides important insight into depth and thermal habitat use of lake sturgeon throughout the calendar year along with exploring the feasibility of using archival tags to obtain important physical habitat attributes during non-spawning periods.

Enzymatic production of dietary nucleotides from low-soluble purine bases by an efficient, thermostable and alkali-tolerant biocatalyst.

PubMed

Del Arco, J; Cejudo-Sanches, J; Esteban, I; Clemente-Suárez, V J; Hormigo, D; Perona, A; Fernández-Lucas, J

2017-12-15

Traditionally, enzymatic synthesis of nucleoside-5'-monophosphates (5'-NMPs) using low water-soluble purine bases has been described as less efficient due to their low solubility in aqueous media. The use of enzymes from extremophiles, such as thermophiles or alkaliphiles, offers the potential to increase solubilisation of these bases by employing high temperatures or alkaline pH. This study describes the cloning, expression and purification of hypoxanthine-guanine-xanthine phosphoribosyltransferase from Thermus thermophilus (TtHGXPRT). Biochemical characterization indicates TtHGXPRT as a homotetramer with excellent activity and stability across a broad range of temperatures (50-90°C) and ionic strengths (0-500mMNaCl), but it also reveals an unusually high activity and stability under alkaline conditions (pH range 8-11). In order to explore the potential of TtHGXPRT as an industrial biocatalyst, enzymatic production of several dietary 5'-NMPs, such as 5'-GMP and 5'-IMP, was carried out at high concentrations of guanine and hypoxanthine. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measurement of high-dynamic range x-ray Thomson scattering spectra for the characterization of nano-plasmas at LCLS

DOE PAGES

MacDonald, M. J.; Gorkhover, T.; Bachmann, B.; ...

2016-08-08

Atomic clusters can serve as ideal model systems for exploring ultrafast (~100 fs) laser-driven ionization dynamics of dense matter on the nanometer scale. Resonant absorption of optical laser pulses enables heating to temperatures on the order of 1 keV at near solid density conditions. To date, direct probing of transient states of such nano plasmas was limited to coherent x-ray imaging. Here we present the first measurement of spectrally-resolved incoherent x-ray scattering from clusters, enabling measurements of transient temperature, densities and ionization. Single shot x-ray Thomson scatterings signals were recorded at 120 Hz using a crystal spectrometer in combination withmore » a single-photon counting and energy-dispersive pnCCD. A precise pump laser collimation scheme enabled recording near background-free scattering spectra from Ar clusters with an unprecedented dynamic range of more than 3 orders of magnitude. As a result, such measurements are important for understanding collective effects in laser-matter interactions on femtosecond timescales, opening new routes for the development of schemes for their ultrafast control.« less

A Parametric Sizing Model for Molten Regolith Electrolysis Reactors to Produce Oxygen from Lunar Regolith

NASA Technical Reports Server (NTRS)

Schreiner, Samuel S.; Dominguez, Jesus A.; Sibille, Laurent; Hoffman, Jeffrey A.

2015-01-01

We present a parametric sizing model for a Molten Electrolysis Reactor that produces oxygen and molten metals from lunar regolith. The model has a foundation of regolith material properties validated using data from Apollo samples and simulants. A multiphysics simulation of an MRE reactor is developed and leveraged to generate a vast database of reactor performance and design trends. A novel design methodology is created which utilizes this database to parametrically design an MRE reactor that 1) can sustain the required mass of molten regolith, current, and operating temperature to meet the desired oxygen production level, 2) can operate for long durations via joule heated, cold wall operation in which molten regolith does not touch the reactor side walls, 3) can support a range of electrode separations to enable operational flexibility. Mass, power, and performance estimates for an MRE reactor are presented for a range of oxygen production levels. The effects of several design variables are explored, including operating temperature, regolith type/composition, batch time, and the degree of operational flexibility.

Measurement of high-dynamic range x-ray Thomson scattering spectra for the characterization of nano-plasmas at LCLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J., E-mail: macdonm@umich.edu; SLAC National Accelerator Laboratory, Menlo Park, California 94025; Gorkhover, T.

2016-11-15

Atomic clusters can serve as ideal model systems for exploring ultrafast (∼100 fs) laser-driven ionization dynamics of dense matter on the nanometer scale. Resonant absorption of optical laser pulses enables heating to temperatures on the order of 1 keV at near solid density conditions. To date, direct probing of transient states of such nano-plasmas was limited to coherent x-ray imaging. Here we present the first measurement of spectrally resolved incoherent x-ray scattering from clusters, enabling measurements of transient temperature, densities, and ionization. Single shot x-ray Thomson scattering signals were recorded at 120 Hz using a crystal spectrometer in combination withmore » a single-photon counting and energy-dispersive pnCCD. A precise pump laser collimation scheme enabled recording near background-free scattering spectra from Ar clusters with an unprecedented dynamic range of more than 3 orders of magnitude. Such measurements are important for understanding collective effects in laser-matter interactions on femtosecond time scales, opening new routes for the development of schemes for their ultrafast control.« less

High Temperature Extremes - Will They Transform Structure of Avian Assemblages in the Desert Southwest?

NASA Astrophysics Data System (ADS)

Mutiibwa, D.; Albright, T. P.; Wolf, B. O.; Mckechnie, A. E.; Gerson, A. R.; Talbot, W. A.; Sadoti, G.; O'Neill, J.; Smith, E.

2014-12-01

Extreme weather events can alter ecosystem structure and function and have caused mass mortality events in animals. With climate change, high temperature extremes are increasing in frequency and magnitude. To better understand the consequences of climate change, scientists have frequently employed correlative models based on species occurrence records. However, these approaches may be of limited utility in the context of extremes, as these are often outside historical ranges and may involve strong non-linear responses. Here we describe work linking physiological response informed by experimental data to geospatial climate datasets in order to mechanistically model the dynamics of dehydration risk to dessert passerine birds. Specifically, we modeled and mapped the occurrence of current (1980-2013) high temperature extremes and evaporative water loss rates for eight species of passerine birds ranging in size from 6.5-75g in the US Southwest portion of their range. We then explored the implications of a 4° C warming scenario. Evaporative water loss (EWL) across a range of high temperatures was measured in heat-acclimated birds captured in the field. We used the North American Land Data Assimilation System 2 dataset to obtain hourly estimates of EWL with a 14-km spatial grain. Assuming lethal dehydration occurs when water loss reaches 15% of body weight, we then produced maps of total daily EWL and time to lethal dehydration based on both current data and future scenarios. We found that milder events capable of producing dehydration in passerine birds over four or more hours were not uncommon over the Southwest, but rapid dehydration conditions (<3 hours) were rare. Under the warming scenario, the frequency and extent of dehydration events expanded greatly, often affecting areas several times larger than in present-day climate. Dehydration risk was especially high among smaller bodied passerines due to their higher mass-specific rates of water loss. Even after accounting for the moderating effects of microsite and topoclimatic refugia, the increase in occurrence of lethal dehydration risk is cause for concern. In particular, our results suggest that smaller bodied passerines may have difficulty in avoiding extirpation over portions of their current range in the desert southwest.

Lichen biomarkers upon heating: a Raman spectroscopic study with implications for extra-terrestrial exploration

NASA Astrophysics Data System (ADS)

Miralles, I.; Capel Ferrón, C.; Hernández, V.; López-Navarrete, J. T.; Jorge-Villar, S. E.

2017-01-01

Lithopanspermia Theory has suggested that life was transferred among planets by meteorites and other rocky bodies. If the planet had an atmosphere, this transfer of life had to survive drastic temperature changes in a very short time in its entry or exit. Only organisms able to endure such a temperature range could colonize a planet from outer space. Many experiments are being carried out by NASA and European Space Agency to understand which organisms were able to survive and how. Among the suite of instruments designed for extraplanetary exploration, particularly for Mars surface exploration, a Raman spectrometer was selected with the main objective of looking for life signals. Among all attributes, Raman spectroscopy is able to identify organic and inorganic compounds, either pure or in admixture, without requiring sample manipulation. In this study, we used Raman spectroscopy to examine the lichen Squamarina lentigera biomarkers. We analyse spectral signature changes after sample heating under different experimental situations, such as (a) laser, (b) analysis accumulations over the same spot and (c) environmental temperature increase. Our goal is to evaluate the capability of Raman spectroscopy to identify unambiguously life markers even if heating has induced spectral changes, reflecting biomolecular transformations. Usnic acid, chlorophyll, carotene and calcium oxalates were identified by the Raman spectra. From our experiments, we have seen that usnic acid, carotene and calcium oxalates (the last two have been suggested to be good biomarkers) respond in a different way to environmental heating. Our main conclusion is that despite their abundance in nature or their inorganic composition the resistance to heat makes some molecules more suitable than others as biomarkers.

Industrial Waste Heat Recovery - Potential Applications, Available Technologies and Crosscutting R&D Opportunities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thekdi, Arvind; Nimbalkar, Sachin U.

2015-01-01

The purpose of this report was to explore key areas and characteristics of industrial waste heat and its generation, barriers to waste heat recovery and use, and potential research and development (R&D) opportunities. The report also provides an overview of technologies and systems currently available for waste heat recovery and discusses the issues or barriers for each. Also included is information on emerging technologies under development or at various stages of demonstrations, and R&D opportunities cross-walked by various temperature ranges, technology areas, and energy-intensive process industries.

Contagious Yawning and Seasonal Climate Variation

PubMed Central

Gallup, Andrew C.; Eldakar, Omar Tonsi

2011-01-01

Recent evidence suggests that yawning is a thermoregulatory behavior. To explore this possibility further, the frequency of contagious yawning in humans was measured while outdoors in a desert climate in the United States during two distinct temperature ranges and seasons (winter: 22°C; early summer: 37°C). As predicted, the proportion of pedestrians who yawned in response to seeing pictures of people yawning differed significantly between the two conditions (winter: 45%; summer: 24%). Across conditions yawning occurred at lower ambient temperatures, and the tendency to yawn during each season was associated with the length of time spent outside prior to being tested. Participants were more likely to yawn in the milder climate after spending long periods of time outside, while prolonged exposure to ambient temperatures at or above body temperature was associated with reduced yawning. This is the first report to show that the incidence of yawning in humans is associated with seasonal climate variation, further demonstrating that yawn-induced contagion effects can be mediated by factors unrelated to individual social characteristics or cognitive development. PMID:21960970

Homoepitaxial growth of metal halide crystals investigated by reflection high-energy electron diffraction

DOE PAGES

Chen, Pei; Kuttipillai, Padmanaban S.; Wang, Lili; ...

2017-01-10

Here, we report the homoepitaxial growth of a metal halide on single crystals investigated with in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). Epitaxial growth of NaCl on NaCl (001) is explored as a function of temperature and growth rate which provides the first detailed report of RHEED oscillations for metal halide growth. Layer-by-layer growth is observed at room temperature accompanied by clear RHEED oscillations while the growth mode transitions to an island (3D) mode at low temperature. At higher temperatures (>100 °C), RHEED oscillations and AFM data indicate a transition to a step-flowmore » growth mode. To show the importance of such metal halide growth, green organic light-emitting diodes (OLEDs) are demonstrated using a doped NaCl film with a phosphorescent emitter as the emissive layer. This study demonstrates the ability to perform in situ and non-destructive RHEED monitoring even on insulating substrates and could enable doped single crystals and crystalline substrates for a range of optoelectronic applications.« less

Deep geothermal resources in the Yangbajing Field, Tibet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao Ping; Jin Jian; Duo Ji

1997-12-31

Since the first well was bored in July 1997 in the Yangbajing geothermal field, more than 80 wells have been drilled. The total of installed capacity is 25.18MWe for geothermal power plant that has generated about 1.0 x 10{sup 9} kWh electricity in all. Temperatures inside shallow reservoir are in the range from 150{degrees}C to 165{degrees}C. No high-temperature field if found below the shallow reservoir in the southern part. In order to enlarge the installed capacity and solve pressure decline in current productive wells, an exploration project of deep geothermal resources has been carried out in the northern part. Themore » highest temperature of 329{degrees}C was detected in well ZK4002 at 1850m depth in 1994. Well ZK4001 drilled in 1996 flows out high-enthalpy thermal fluid at the wellhead, in which the average temperature is 248{degrees}C in the feeding zones. There is a great potential for power generation in the northern part. The exploitation of deep geothermal resources would effect the production of existing wells.« less

Capability of simultaneous Rayleigh LiDAR and O2 airglow measurements in exploring the short period wave characteristics

NASA Astrophysics Data System (ADS)

Taori, Alok; Raghunath, Karnam; Jayaraman, Achuthan

We use combination of simultaneous measurements made with Rayleigh lidar and O2 airglow monitoring to improve lidar investigation capability to cover a higher altitude range. We feed instantaneous O2 airglow temperatures instead the model values at the top altitude for subsequent integration method of temperature retrieval using Rayleigh lidar back scattered signals. Using this method, errors in the lidar temperature estimates converges at higher altitudes indicating better altitude coverage compared to regular methods where model temperatures are used instead of real-time measurements. This improvement enables the measurements of short period waves at upper mesospheric altitudes (~90 km). With two case studies, we show that above 60 km the few short period wave amplitude drastically increases while, some of the short period wave show either damping or saturation. We claim that by using such combined measurements, a significant and cost effective progress can be made in the understanding of short period wave processes which are important for the coupling across the different atmospheric regions.

Effects of elevated temperature on the viscoplastic modeling of graphite/polymeric composites

NASA Technical Reports Server (NTRS)

Gates, Thomas S.

1991-01-01

To support the development of new materials for the design of next generation supersonic transports, a research program is underway at NASA to assess the long term durability of advanced polymer matrix composites (PMC's). One of main objectives of the program was to explore the effects of elevated temperature (23 to 200 C) on the constitutive model's material parameters. To achieve this goal, test data on the observed nonlinear, stress-strain behavior of IM7/5260 and IM7/8320 composites under tension and compression loading were collected and correlated against temperature. These tests, conducted under isothermal conditions using variable strain rates, included such phenomena as stress relaxation and short term creep. The second major goal was the verification of the model by comparison of analytical predictions and test results for off axis and angle ply laminates. Correlation between test and predicted behavior was performed for specimens of both material systems over a range of temperatures. Results indicated that the model provided reasonable predictions of material behavior in load or strain controlled tests. Periods of loading, unloading, stress relaxation, and creep were accounted for.

6H-SiC Transistor Integrated Circuits Demonstrating Prolonged Operation at 500 C

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Chang, Carl W.; Beheim, Glenn M.; Okojie, Robert S.; Evans, Laura J.; Meredith, Roger; Ferrier, Terry; Krasowski, Michael J.;

Thermalization of Heavy Ions in the Solar Wind

NASA Astrophysics Data System (ADS)

Tracy, Patrick J.; Kasper, Justin C.; Zurbuchen, Thomas H.; Raines, Jim M.; Shearer, Paul; Gilbert, Jason

2015-10-01

Observations of velocity distribution functions from the Advanced Composition Explorer/Solar Wind Ion Composition Spectrometer heavy ion composition instrument are used to calculate ratios of kinetic temperature and Coulomb collisional interactions of an unprecedented 50 ion species in the solar wind. These ions cover a mass per charge range of 1-5.5 amu/e and were collected in the time range of 1998-2011. We report the first calculation of the Coulomb thermalization rate between each of the heavy ion (A > 4 amu) species present in the solar wind along with protons (H+) and alpha particles (He2+). From these rates, we find that protons are the dominant source of Coulomb collisional thermalization for heavy ions in the solar wind and use this fact to calculate a collisional age for those heavy ion populations. The heavy ion thermal properties are well organized by this collisional age, but we find that the temperature of all heavy ions does not simply approach that of protons as Coulomb collisions become more important. We show that He2+ and C6+ follow a monotonic decay toward equal temperatures with protons with increasing collisional age, but O6+ shows a noted deviation from this monotonic decay. Furthermore, we show that the deviation from monotonic decay for O6+ occurs in solar wind of all origins, as determined by its Fe/O ratio. The observed differences in heavy ion temperature behavior point toward a local heating mechanism that favors ions depending on their charge and mass.

Photochemical Haze Formation in the Atmospheres of Super-Earths and Mini-Neptunes

NASA Technical Reports Server (NTRS)

He, Chao; Hoerst, Sarah M.; Lewis, Nikole K.; Yu, Xinting; Moses, Julianne I.; Kempton, Eliza M.- R.; Marley, Mark S.; McGuiggan, Patricia; Morley, Caroline V.; Valenti, Jeff A.;

Investigating factors affecting the body temperature of dogs competing in cross country (canicross) races in the UK.

PubMed

Carter, Anne J; Hall, Emily J

2018-02-01

Increasing numbers of people are running with their dogs, particularly in harness through the sport canicross. Whilst canicross races are typically held in the winter months, some human centred events are encouraging running with dogs in summer months, potentially putting dogs at risk of heat related injuries, including heatstroke. The aim of this project was to investigate the effects of ambient conditions and running speed on post-race temperature of canicross dogs in the UK, and investigate the potential risk of heatstroke to canicross racing dogs. The effects of canine characteristics (e.g. gender, coat colour) were explored in order to identify factors that could increase the risk of exercise-induced hyperthermia (defined as body temperature exceeding the upper normal limit of 38.8°C).108 dogs were recruited from 10 race days, where ambient conditions ranged from - 5 to 11°C measured as universal thermal comfort index (UTCI). 281 post race tympanic membrane temperatures were recorded, ranging from 37.0-42.5°C. There was a weak correlation between speed and post-race temperature (r = 0.269, P < 0.001). Whilst no correlation between any single environmental factor or UTCI and post-race temperature was found, the proportion of dogs developing exercise-induced hyperthermia during the race increased with UTCI (r = 0.688, P = 0.028). Male dogs (χ(1) = 18.286, P < 0.001), and dark coated dogs (χ(2) = 8.234, P = 0.014), were significantly more likely to finish the race with a temperature exceeding 40.6°C. Prolonged elevati°n of body temperature above this temperature is likely to cause heatstroke. At every race dogs exceeded this critical temperature, with 10.7% (n = 30) of the overall study population exceeding this temperature throughout the study period. The results suggest male dogs, dark coloured dogs, and increased speed of running all increase the risk of heatstroke in racing canicross dogs. Further research is required to investigate the impact of environmental conditions on post-race cooling, to better understand safe running conditions for dogs. Copyright © 2017 Elsevier Ltd. All rights reserved.

A cryostatic, fast scanning, wideband NQR spectrometer for the VHF range

NASA Astrophysics Data System (ADS)

Scharfetter, Hermann; Bödenler, Markus; Narnhofer, Dominik

2018-01-01

In the search for a novel MRI contrast agent which relies on T1 shortening due to quadrupolar interaction between Bi nuclei and protons, a fast scanning wideband system for zero-field nuclear quadrupole resonance (NQR) spectroscopy is required. Established NQR probeheads with motor-driven tune/match stages are usually bulky and slow, which can be prohibitive if it comes to Bi compounds with low SNR (excessive averaging) and long quadrupolar T1 times. Moreover many experiments yield better results at low temperatures such as 77 K (liquid nitrogen, LN) thus requiring easy to use cryo-probeheads. In this paper we present electronically tuned wideband probeheads for bands in the frequency range 20-120 MHz which can be immersed in LN and which enable very fast explorative scans over the whole range. To this end we apply an interleaved subspectrum sampling strategy (ISS) which relies on the electronic tuning capability. The superiority of the new concept is demonstrated with an experimental scan of triphenylbismuth from 24 to 116 MHz, both at room temperature and in LN. Especially for the first transition which exhibits extremely long T1 times (64 ms) the and low signal the new approach allows an acceleration factor by more than 100 when compared to classical methods.

EXPLORING BIASES OF ATMOSPHERIC RETRIEVALS IN SIMULATED JWST TRANSMISSION SPECTRA OF HOT JUPITERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rocchetto, M.; Waldmann, I. P.; Tinetti, G.

2016-12-10

With a scheduled launch in 2018 October, the James Webb Space Telescope ( JWST ) is expected to revolutionize the field of atmospheric characterization of exoplanets. The broad wavelength coverage and high sensitivity of its instruments will allow us to extract far more information from exoplanet spectra than what has been possible with current observations. In this paper, we investigate whether current retrieval methods will still be valid in the era of JWST , exploring common approximations used when retrieving transmission spectra of hot Jupiters. To assess biases, we use 1D photochemical models to simulate typical hot Jupiter cloud-free atmospheresmore » and generate synthetic observations for a range of carbon-to-oxygen ratios. Then, we retrieve these spectra using TauREx, a Bayesian retrieval tool, using two methodologies: one assuming an isothermal atmosphere, and one assuming a parameterized temperature profile. Both methods assume constant-with-altitude abundances. We found that the isothermal approximation biases the retrieved parameters considerably, overestimating the abundances by about one order of magnitude. The retrieved abundances using the parameterized profile are usually within 1 σ of the true state, and we found the retrieved uncertainties to be generally larger compared to the isothermal approximation. Interestingly, we found that by using the parameterized temperature profile we could place tight constraints on the temperature structure. This opens the possibility of characterizing the temperature profile of the terminator region of hot Jupiters. Lastly, we found that assuming a constant-with-altitude mixing ratio profile is a good approximation for most of the atmospheres under study.« less

Effects of temperature and salinity on survival, growth and DNA methylation of juvenile Pacific abalone, Haliotis discus hannai Ino

NASA Astrophysics Data System (ADS)

Kong, Ning; Liu, Xiao; Li, Junyuan; Mu, Wendan; Lian, Jianwu; Xue, Yanjie; Li, Qi

2017-09-01

Temperature and salinity are two of the most potent abiotic factors influencing marine mollusks. In this study, we investigated the individual and combined effects of temperature and salinity on the survival and growth of juvenile Pacific abalone, Haliotis discus hannai Ino, and also examined the DNA methylation alteration that may underpin the phenotypic variation of abalone exposed to different rearing conditions. The single-factor data showed that the suitable ranges of temperature and salinity were 16-28°C at a constant salinity of 32, and 24-40 at a constant temperature of 20°C, respectively. The two-factor data indicated that both survival and growth were significantly affected by temperature, salinity and their interaction. The optimal temperature-salinity combination for juveniles was 23-25°C and 30-36. To explore environment-induced DNA methylation alteration, the methylation-sensitive amplified polymorphism (MSAP) technique was used to analyze the genomic methylation profiles of abalone reared in optimal and adverse conditions. Neither temperature nor salinity induced evident changes in the global methylation level, but 67 and 63 differentially methylated loci were identified in temperature and salinity treatments, respectively. The between-group eigen analysis also showed that both temperature and salinity could induce epigenetic differentiation in H. discus hannai Ino. The results of our study provide optimal rearing conditions for juvenile H. discus hannai Ino, and represent the first step toward revealing the epigenetic regulatory mechanism of abalone in response to thermal and salt stresses.

An alternative estimation of the RF-enhanced plasma temperature during SPEAR artificial heating experiments: Early results

NASA Astrophysics Data System (ADS)

Vickers, H.; Baddeley, L.

2011-11-01

RF heating of the F region plasma at high latitudes has long been known to produce electron temperature increases that can vary from tens to hundreds of percent above the background, unperturbed level. In contrast, artificial ionospheric modification experiments conducted using the Space Plasma Exploration by Active Radar (SPEAR) heating facility on Svalbard have often failed to produce obvious enhancements in the electron temperatures when measured using the European Incoherent Scatter Svalbard radar (ESR), colocated with the heater. Contamination of the ESR ion line spectra by the zero-frequency purely growing mode (PGM) feature is known to persist at varying amplitudes throughout SPEAR heating, and such spectral features can lead to significant temperature underestimations when the incoherent scatter spectra are analyzed using conventional methods. In this study, we present the first results of applying a recently developed technique to correct the PGM-contaminated spectra to SPEAR-enhanced ESR spectra and derive an alternative estimate of the SPEAR-heated electron temperature. We discuss how the effectiveness of the spectrum corrections can be affected by the data variance, estimated over the integration period. The subsequent electron temperatures, inferred from corrected spectra, range from a few tens to a few hundred Kelvin above the average background temperature. These temperatures are found to be in reasonable agreement with the theoretical “enhanced” temperature, calculated for the peak of the stationary temperature perturbation profile, when realistic absorption effects are accounted for.

Temperature dependence of the hydrated electron's excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

NASA Astrophysics Data System (ADS)

Farr, Erik P.; Zho, Chen-Chen; Challa, Jagannadha R.; Schwartz, Benjamin J.

2017-08-01

The structure of the hydrated electron, particularly whether it exists primarily within a cavity or encompasses interior water molecules, has been the subject of much recent debate. In Paper I [C.-C. Zho et al., J. Chem. Phys. 147, 074503 (2017)], we found that mixed quantum/classical simulations with cavity and non-cavity pseudopotentials gave different predictions for the temperature dependence of the rate of the photoexcited hydrated electron's relaxation back to the ground state. In this paper, we measure the ultrafast transient absorption spectroscopy of the photoexcited hydrated electron as a function of temperature to confront the predictions of our simulations. The ultrafast spectroscopy clearly shows faster relaxation dynamics at higher temperatures. In particular, the transient absorption data show a clear excess bleach beyond that of the equilibrium hydrated electron's ground-state absorption that can only be explained by stimulated emission. This stimulated emission component, which is consistent with the experimentally known fluorescence spectrum of the hydrated electron, decreases in both amplitude and lifetime as the temperature is increased. We use a kinetic model to globally fit the temperature-dependent transient absorption data at multiple temperatures ranging from 0 to 45 °C. We find the room-temperature lifetime of the excited-state hydrated electron to be 137 ±40 fs, in close agreement with recent time-resolved photoelectron spectroscopy (TRPES) experiments and in strong support of the "non-adiabatic" picture of the hydrated electron's excited-state relaxation. Moreover, we find that the excited-state lifetime is strongly temperature dependent, changing by slightly more than a factor of two over the 45 °C temperature range explored. This temperature dependence of the lifetime, along with a faster rate of ground-state cooling with increasing bulk temperature, should be directly observable by future TRPES experiments. Our data also suggest that the red side of the hydrated electron's fluorescence spectrum should significantly decrease with increasing temperature. Overall, our results are not consistent with the nearly complete lack of temperature dependence predicted by traditional cavity models of the hydrated electron but instead agree qualitatively and nearly quantitatively with the temperature-dependent structural changes predicted by the non-cavity hydrated electron model.

Heat capacity of the site-diluted spin dimer system Ba₃(Mn 1-xV x)₂O₈

DOE PAGES

Samulon, E. C.; Shapiro, M. C.; Fisher, I. R.

2011-08-05

Heat-capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba₃(Mn 1-xV x)₂O₈. The parent compound Ba₃Mn₂O₈ is a spin dimer system based on pairs of antiferromagnetically coupled S=1, 3d² Mn⁵⁺ ions such that the zero-field ground state is a product of singlets. Substitution of nonmagnetic S=0, 3d⁰ V⁵⁺ ions leads to an interacting network of unpaired Mn moments, the low-temperature properties of which are explored in the limit of small concentrations 0≤x≤0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidencemore » for a phase transition. The concentration dependence does not conform to expectations for a spin-glass state. Rather, the data suggest a low-temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.« less

Effect of thermal annealing on the thermoluminescent properties of nano-calcium fluoride and its dose-response characteristics.

PubMed

Mundupuzhakal, J K; Biswas, R H; Chauhan, S; Varma, V; Acharya, Y B; Chakrabarty, B S

2015-12-01

Nano-CaF2, prepared by the co-precipitation method, was annealed under different annealing conditions to improve its thermoluminescence (TL) characteristics. Different annealing parameters, such as temperature (400-700°C), duration (1-4 h) and environment (vacuum and air), were explored. The effect on TL sensitivity, peak position (Tm) and full-width at half-maximum (FWHM) with respect to the different annealing conditions are discussed as they are the measure of crystallinity of the material. Annealing temperature of 500°C with annealing duration of two and a half hours in vacuum provided the highest luminescence response (i.e. maximum sensitivity, minimum peak temperature and FWHM). Wide detectable dose range (5 mGy to 2 kGy), absence of thermal quenching and sufficient activation energy (1.04 eV) of this phosphor make it suitable for dosimetric applications. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effect of cooldown and residual magnetic field on the performance of niobium–copper clad superconducting radio-frequency cavity

DOE PAGES

Dhakal, Pashupati; Ciovati, Gianluigi

2017-11-22

Here, we present the results of rf measurements on a niobium–copper clad superconducting radio-frequency cavity with different cooldown conditions and residual magnetic field in a vertical test Dewar in order to explore the effect of thermal current induced magnetic field and its trapping on the performance of the cavity. The residual resistance, extracted from the Q 0( T) curves in the temperature range 4.3–1.5 K, showed no dependence on a temperature gradient along the cavity during the cooldown across the critical temperature up to ~50 K m –1. The rf losses due to the trapping of residual magnetic field duringmore » the cavity cooldown were found to be ~4.3 nΩ μT –1, comparable to the values measured in bulk niobium cavities. An increase of residual resistance following multiple cavity quenches was observed along with evidence of trapping of magnetic flux generated by thermoelectric currents.« less

Effect of cooldown and residual magnetic field on the performance of niobium–copper clad superconducting radio-frequency cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhakal, Pashupati; Ciovati, Gianluigi

Here, we present the results of rf measurements on a niobium–copper clad superconducting radio-frequency cavity with different cooldown conditions and residual magnetic field in a vertical test Dewar in order to explore the effect of thermal current induced magnetic field and its trapping on the performance of the cavity. The residual resistance, extracted from the Q 0( T) curves in the temperature range 4.3–1.5 K, showed no dependence on a temperature gradient along the cavity during the cooldown across the critical temperature up to ~50 K m –1. The rf losses due to the trapping of residual magnetic field duringmore » the cavity cooldown were found to be ~4.3 nΩ μT –1, comparable to the values measured in bulk niobium cavities. An increase of residual resistance following multiple cavity quenches was observed along with evidence of trapping of magnetic flux generated by thermoelectric currents.« less

Inelastic properties of ice Ih at low temperatures and high pressures

USGS Publications Warehouse

Kirby, S.H.; Durham, W.B.; Beeman, M.L.; Heard, H.C.; Daley, M.A.

1987-01-01

The aim of our research programme is to explore the rheological behavior of H2O ices under conditions appropriate to the interiors of the icy satellites of the outer planets in order to give insight into their deformation. To this end, we have performed over 100 constant-strain-rate compression tests at pressures to 500 MPa and temperatures as low as 77 K. At P > 30 MPa, ice Ih fails by a shear instability producing faults in the maximum shear stress orientation and failure strength typically is independent of pressure. This unusual faulting behavior is thought to be connected with phase transformations localized in the shear zones. The steady-state strength follows rheological laws of the thermally-activated power-law type, with different flow law parameters depending on the range of test temperatures. The flow laws will be discussed with reference to the operating deformation mechanisms as deduced from optical-scale microstructures and comparison with other work.

Molecular electronics--resonant transport through single molecules.

PubMed

Lörtscher, Emanuel; Riel, Heike

2010-01-01

The mechanically controllable break-junction technique (MCBJ) enables us to investigate charge transport through an individually contacted and addressed molecule in ultra-high vacuum (UHV) environment at variable temperature ranging from room temperature down to 4 K. Using a statistical measurement and analysis approach, we acquire current-voltage (I-V) characteristics during the repeated formation, manipulation, and breaking of a molecular junction. At low temperatures, voltages accessing the first molecular orbitals in resonance can be applied, providing spectroscopic information about the junction's energy landscape, in particular about the molecular level alignment in respect to the Fermi energy of the electrodes. Thereby, we can investigate the non-linear transport properties of various types of functional molecules and explore their potential use as functional building blocks for future nano-electronics. An example will be given by the reversible and controllable switching between two distinct conductive states of a single molecule. As a proof-of-principle for functional molecular devices, a single-molecule memory element will be demonstrated.

Giant current fluctuations in an overheated single-electron transistor

NASA Astrophysics Data System (ADS)

Laakso, M. A.; Heikkilä, T. T.; Nazarov, Yuli V.

2010-11-01

Interplay of cotunneling and single-electron tunneling in a thermally isolated single-electron transistor leads to peculiar overheating effects. In particular, there is an interesting crossover interval where the competition between cotunneling and single-electron tunneling changes to the dominance of the latter. In this interval, the current exhibits anomalous sensitivity to the effective electron temperature of the transistor island and its fluctuations. We present a detailed study of the current and temperature fluctuations at this interesting point. The methods implemented allow for a complete characterization of the distribution of the fluctuating quantities, well beyond the Gaussian approximation. We reveal and explore the parameter range where, for sufficiently small transistor islands, the current fluctuations become gigantic. In this regime, the optimal value of the current, its expectation value, and its standard deviation differ from each other by parametrically large factors. This situation is unique for transport in nanostructures and for electron transport in general. The origin of this spectacular effect is the exponential sensitivity of the current to the fluctuating effective temperature.

Self-consistent electro-opto-thermal model of quantum cascade lasers with coupled electron and phonon interactions far from equilibrium

NASA Astrophysics Data System (ADS)

Yousefvand, Hossein Reza

2017-12-01

A self-consistent model of quantum cascade lasers (QCLs) is presented here for the study of the QCL's behavior in the far from equilibrium conditions. The approach is developed by employing a number of physics-based models such as the carrier and photon rate equations, the energy balance equation, the heat transfer equation and a simplified rate equation for the creation and annihilation of nonequilibrium optical phonons. The temperature dependency of the relevant physical effects such as stimulated gain cross section, longitudinal optical (LO) phonons and hot-phonon generation rates are included in the model. Using the presented model, the static and transient device characteristics are calculated and analyzed for a wide range of heat sink temperatures. Besides the output characteristics, this model also provides a way to study the hot-phonon dynamics in the device, and to explore the electron temperature and thermal roll-over in the QCLs.

Role of Temperature and SiCP Parameters in Stability and Quality of Al-Si-Mg/SiC Foams

NASA Astrophysics Data System (ADS)

Ravi Kumar, N. V.; Gokhale, Amol A.

2018-06-01

Composites of Al-Si-Mg (A356) alloy with silicon carbide particles were synthesized in-house and foamed by melt processing using titanium hydride as foaming agent. The effects of the SiCP size and content, and foaming temperature on the stability and quality of the foam were explored. It was observed that the foam stability depended on the foaming temperature alone but not on the particle size or volume percent within the studied ranges. Specifically, foam stability was poor at 670°C. Among the stable foams obtained at 640°C, cell soundness (absence of/low defects, and collapse) was seen to vary depending on the particle size and content; For example, for finer size, lower particle contents were sufficient to obtain sound cell structure. It is possible to determine a foaming process window based on material and process parameters for good expansion, foam stability, and cell structure.

Cu3Mo2O9: An Ultralow-Firing Microwave Dielectric Ceramic with Good Temperature Stability and Chemical Compatibility with Aluminum

NASA Astrophysics Data System (ADS)

Wen, Wangxi; Li, Chunchun; Sun, Yihua; Tang, Ying; Fang, Liang

2018-02-01

An ultralow-firing microwave dielectric ceramic Cu3Mo2O9 with orthorhombic structure has been fabricated via a solid-state reaction method. X-ray diffraction analysis, Rietveld refinement, Raman spectroscopy, energy-dispersive spectrometry, and scanning electron microscopy were employed to explore the phase purity, crystal structure, and microstructure. Pure and dense Cu3Mo2O9 ceramics could be obtained in the sintering temperature range from 580°C to 680°C. The sample sintered at 660°C for 4 h exhibited the highest relative density (˜ 97.2%) and best microwave dielectric properties with ɛ r = 7.2, Q × f = 19,300 GHz, and τ f = - 7.8 ppm/°C. Chemical compatibility with aluminum electrodes was also confirmed. All the results suggest that Cu3Mo2O9 ceramic is a promising candidate for use in ultralow-temperature cofired ceramic applications.

Flexible Dielectric Nanocomposites with Ultrawide Zero-Temperature Coefficient Windows for Electrical Energy Storage and Conversion under Extreme Conditions.

PubMed

Shehzad, Khurram; Xu, Yang; Gao, Chao; Li, Hanying; Dang, Zhi-Min; Hasan, Tawfique; Luo, Jack; Duan, Xiangfeng

2017-03-01

Polymer dielectrics offer key advantages over their ceramic counterparts such as flexibility, scalability, low cost, and high breakdown voltages. However, a major drawback that limits more widespread application of polymer dielectrics is their temperature-dependent dielectric properties. Achieving dielectric constants with low/zero-temperature coefficient (L/0TC) over a broad temperature range is essential for applications in diverse technologies. Here, we report a hybrid filler strategy to produce polymer composites with an ultrawide L/0TC window of dielectric constant, as well as a significantly enhanced dielectric value, maximum energy storage density, thermal conductivity, and stability. By creating a series of percolative polymer composites, we demonstrated hybrid carbon filler based composites can exhibit a zero-temperature coefficient window of 200 °C (from -50 to 150 °C), the widest 0TC window for all polymer composite dielectrics reported to date. We further show the electric and dielectric temperature coefficient of the composites is highly stable against stretching and bending, even under AC electric field with frequency up to 1 MHz. We envision that our method will push the functional limits of polymer dielectrics for flexible electronics in extreme conditions such as in hybrid vehicles, aerospace, power electronics, and oil/gas exploration.

Validating computational predictions of night-time ventilation in Stanford's Y2E2 building

NASA Astrophysics Data System (ADS)

Chen, Chen; Lamberti, Giacomo; Gorle, Catherine

2017-11-01

Natural ventilation can significantly reduce building energy consumption, but robust design is a challenging task. We previously presented predictions of natural ventilation performance in Stanford's Y2E2 building using two models with different levels of fidelity, embedded in an uncertainty quantification framework to identify the dominant uncertain parameters and predict quantified confidence intervals. The results showed a slightly high cooling rate for the volume-averaged temperature, and the initial thermal mass temperature and window discharge coefficients were found to have an important influence on the results. To further investigate the potential role of these parameters on the observed discrepancies, the current study is performing additional measurements in the Y2E2 building. Wall temperatures are recorded throughout the nightflush using thermocouples; flow rates through windows are measured using hotwires; and spatial variability in the air temperature is explored. The measured wall temperatures are found the be within the range of our model assumptions, and the measured velocities agree reasonably well with our CFD predications. Considerable local variations in the indoor air temperature have been recorded, largely explaining the discrepancies in our earlier validation study. Future work will therefore focus on a local validation of the CFD results with the measurements. Center for Integrated Facility Engineering (CIFE).

Schnellverfahren zur flammenlosen AAS-Bestimmung von Spurenelementen in geologischen Proben

NASA Astrophysics Data System (ADS)

Schrön, W.; Bombach, G.; Beuge, P.

This paper reports experience with direct quantitative trace element determinations in powdered geological samples by nameless atomic absorption spectroscopy. Two methods were explored. The first one is based on the production of a sample aerosol by laser radiation in a specifically designed sample chamber and the subsequent transport of the aerosol into a graphite tube, which has been preheated to a stable temperature. This technique is suited for a large range of concentration and is relatively free from matrix interferences. The technique was tested for the elements Ag, As, Bi, Cd, Co, Mn, Ni, Pb, Sb, Se, Sr and Tl. The described sample chamber can be also used in combination with other spcctroscopic techniques. The second method explored permits the quantitative determination of trace elements at very low concentrations. Essentially an accurately weighed amount of sample is placed on a graphite rod and introduced into a graphite furnace by inserting the rod through the sample injection port. Atomization takes place also under stable temperature conditions. Using this technique detection limits were found to be 10 -11 g for Ag, 2 × 10 -11 g for Cd and 10 -10 g for Sb in silicate materials.

Compressibilities and Volume Fluctuations of Archaeal Tetraether Liposomes

PubMed Central

Chong, Parkson Lee-Gau; Sulc, Michael; Winter, Roland

2010-01-01

Bipolar tetraether lipids (BTLs) are abundant in crenarchaeota, which thrive in both thermophilic and nonthermophilic environments, with wide-ranging growth temperatures (4–108°C). BTL liposomes can serve as membrane models to explore the role of BTLs in the thermal stability of the plasma membrane of crenarchaeota. In this study, we focus on the liposomes made of the polar lipid fraction E (PLFE). PLFE is one of the main BTLs isolated from the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. Using molecular acoustics (ultrasound velocimetry and densimetry), pressure perturbation calorimetry, and differential scanning calorimetry, we have determined partial specific adiabatic and isothermal compressibility, their respective compressibility coefficients, partial specific volume, and relative volume fluctuations of PLFE large unilamellar vesicles (LUVs) over a wide range of temperatures (20–85°C). The results are compared with those obtained from liposomes made of dipalmitoyl-L-α-phosphatidylcholine (DPPC), a conventional monopolar diester lipid. We found that, in the entire temperature range examined, compressibilities of PLFE LUVs are low, comparable to those found in gel state of DPPC. Relative volume fluctuations of PLFE LUVs at any given temperature examined are 1.6–2.2 times more damped than those found in DPPC LUVs. Both compressibilities and relative volume fluctuations in PLFE LUVs are much less temperature-sensitive than those in DPPC liposomes. The isothermal compressibility coefficient (βTlipid) of PLFE LUVs changes from 3.59 × 10−10 Pa−1 at 25°C to 4.08 × 10−10 Pa−1 at 78°C. Volume fluctuations of PLFE LUVs change only 0.25% from 30°C to 80°C. The highly damped volume fluctuations and their low temperature sensitivity, echo that PLFE liposomes are rigid and tightly packed. To our knowledge, the data provide a deeper understanding of lipid packing in PLFE liposomes than has been previously reported, as well as a molecular explanation for the low solute permeation and limited membrane lateral motion. The obtained results may help to establish new strategies for rational design of stable BTL-based liposomes for drug/vaccine delivery. PMID:21081080

Non-hydrolytic Sol-gel Synthesis of Tin Sulfides

NASA Astrophysics Data System (ADS)

Kaur, Rajvinder

The non-hydrolytic sol-gel (NHSG) process is an effective low temperature route well known for preparing homogeneous metal oxides. Thermodynamically as well as kinetically favored products, which cannot be prepared with the traditional solid-state routes, can be produced using NHSG. This project is focused on the exploration of NHSG synthesis of binary tin sulfides. In the past few years, metal sulfides have been the subject of significant interest. Much effort has been devoted to understand these materials because of their potential applications in electronic, optical, and superconductor devices.4 Among these materials, tin sulfides are materials of technological importance, which are being explored as semiconductors, anode materials for Li ion batteries, photoconductors, photocatalysts and absorber layer materials in photovoltaic solar cell devices. All of these applications depend upon features like homogeneity, oxidation state, high surface area and purity of the materials. These properties can be difficult to achieve by employing traditional synthetic routes, which require high temperatures due to slow diffusion, limiting the products to thermodynamically stable phases and prohibiting control over properties like particle size and surface area. A variety of low temperature methods are being explored due to the increased demand for such advanced materials. This project is focused on exploring the NHSG approach to synthesize binary tin sulfides, with the main goal of establishing conditions for the targeted synthesis of different tin sulfide polymorphs with controlled particle size. Being non-oxide materials, tin sulfides can be air sensitive, which requires special attention in handling. All reactions were carried out in absence of oxygen. This project explores the reaction of tin halides with thioethers in a dry solvent medium, leading to the formation of tin sulfides. There are a number of synthetic parameters that can be varied for the NHSG approach. A systematic study was carried out to understand the influence of all reaction variables, which include tin halides, thioethers, solvents, time, temperature, stoichiometry and concentration. Fine tuning of all reaction variables was carried out. The crystallization and phase stability of the as-recovered products was further studied by heat treatments of the samples. A detailed investigation of synthetic variables during NHSG reactions resulted in controlled synthesis of two crystalline tin sulfide polymorphs, SnS and SnS2. A third polymorph, Sn2S3, could be obtained after heat treatments in the temperature range of 400 to 500 °C. Conditions for the targeted synthesis of particles with various sizes and morphologies were established. Samples were characterized by powder X-ray diffraction, electron microscopy in combination with EDS, CHNS analysis and thermo gravimetric/differential thermal analysis.

Using Google Earth in Marine Research and Operational Decision Support

NASA Astrophysics Data System (ADS)

Blower, J. D.; Bretherton, D.; Haines, K.; Liu, C.; Rawlings, C.; Santokhee, A.; Smith, I.

2006-12-01

A key advantage of Virtual Globes ("geobrowsers") such as Google Earth is that they can display many different geospatial data types at a huge range of spatial scales. In this demonstration and poster display we shall show how marine data from disparate sources can be brought together in a geobrowser in order to support both scientific research and operational search and rescue activities. We have developed the Godiva2 interactive website for browsing and exploring marine data, mainly output from supercomputer analyses and predictions of ocean circulation. The user chooses a number of parameters (e.g. sea temperature at 100m depth on 1st July 2006) and can load an image of the resulting data in Google Earth. Through the use of an automatically-refreshing NetworkLink the user can explore the whole globe at a very large range of spatial scales: the displayed data will automatically be refreshed to show data at increasingly fine resolution as the user zooms in. This is a valuable research tool for exploring these terabyte- scale datasets. Many coastguard organizations around the world use SARIS, a software application produced by BMT Cordah Ltd., to predict the drift pattern of objects in the sea in order to support search and rescue operations. Different drifting objects have different trajectories depending on factors such as their buoyancy and windage and so a computer model, supported by meteorological and oceanographic data, is needed to help rescuers locate their targets. We shall demonstrate how Google Earth is used to display output from the SARIS model (including the search target location and associated error polygon) alongside meteorological data (wind vectors) and oceanographic data (sea temperature, surface currents) from Godiva2 in order to support decision-making. We shall also discuss the limitations of using Google Earth in this context: these include the difficulties of working with time- dependent data and the need to access data securely. essc.ac.uk:8080/Godiva2

Reentry Thermal Analysis of a Generic Crew Exploration Vehicle Structure

NASA Technical Reports Server (NTRS)

Ko, William L.; Gong, Leslie; Quinn, Robert D.

2007-01-01

Comparative studies were performed on the heat-shielding characteristics of honeycomb-core sandwich panels fabricated with different materials for possible use as wall panels for the proposed crew exploration vehicle. Graphite/epoxy sandwich panel was found to outperform aluminum sandwich panel under the same geometry due to superior heat-shielding qualities and lower material density. Also, representative reentry heat-transfer analysis was performed on the windward wall structures of a generic crew exploration vehicle. The Apollo low Earth orbit reentry trajectory was used to calculate the reentry heating rates. The generic crew exploration vehicle has a graphite/epoxy composite honeycomb sandwich exterior wall and an aluminum honeycomb sandwich interior wall, and is protected with the Apollo thermal protection system ablative material. In the thermal analysis computer program used, the TPS ablation effect was not yet included; however, the results from the nonablation heat-transfer analyses were used to develop a "virtual ablation" method to estimate the ablation heat loads and the thermal protection system recession thicknesses. Depending on the severity of the heating-rate time history, the virtual ablation period was found to last for 87 to 107 seconds and the ablation heat load was estimated to be in the range of 86 to 88 percent of the total heat load for the ablation time period. The thermal protection system recession thickness was estimated to be in the range of 0.08 to 0.11 inches. For the crew exploration vehicle zero-tilt and 18-degree-tilt stagnation points, thermal protection system thicknesses of h = {0.717, 0.733} inches were found to be adequate to keep the substructural composite sandwich temperature below the limit of 300 F.

Improved low temperature performance of lithium ion cells with quaternary carbonate-based electrolytes

NASA Technical Reports Server (NTRS)

Smart, M. C.; Ratnakumar, B. V.; Whitcanack, L. D.; Chin, K. B.; Surampudi, S.; Croft, H.; Tice, D.; Staniewicz, R.

2002-01-01

In order to enable future missions involving the exploration of the surface of Mars with Landers and Rovers, NASA desires long life, high energy density rechargeable batteries which can operate well at very low temperature (down to 40(deg)C). Lithium-ion technology has been identified as being the most promising chemistry, due to high gravimetric and volumetric energy densities, as well as, long life characteristics. However, the state-of-art (SOA) technology is not sufficient to meet the needs of many applications that require excellent low temperature capabilities. To further improve this technology, work at JF'L has been focused upon developing electrolytes that result in lithium-ion cells with wider temperature ranges of operation. These efforts have led to the identification of a number of ternary and quaternary, all carbonate-based electrolytes that have been demonstrated to result in improved low temperature performance in experimental three-electrode MCMB carbon/LiNio.sCoo.zOz cells. A number of electrochemical characterization techniques were performed on these cells (i.e., Tafel polarization measurements, linear polarization measurements, and electrochemical impedance spectroscopy (EIS)) to further enhance our understanding of the performance limitations at low temperature. The most promising electrolyte formulations, namely 1 .O M LiPF6EC+DEC+DMC+EMC (1 : 1: 1 :2 v/v) and 1 .O M LiPF6 EC+DEC+DMC+EMC (1 : 1 : 1 :3 v/v), were incorporated into SAFT prototype DD-size (9 Ahr) lithium- cells for evaluation. A number of electrical tests were performed on these cells, including rate characterization as a function of temperature, cycle life characterization at different temperatures, as well as, many mission specific characterization test to determine their viability to enable future missions to Mars. Excellent performance was observed with the prototype DD-size cells over a wide temperature range (-50 to 4OoC), with high specific energy being delivered at very low temperatures (i.e, over 95 WHrKg being delivered at 40(deg)C using a C/10 discharge rate).

Latitude Variation of the Subsurface Lunar Temperature: Lunar Prospector Thermal Neutrons

NASA Astrophysics Data System (ADS)

Little, R. C.; Feldman, W. C.; Maurice, S.; Genetay, I.; Lawrence, D. J.; Lawson, S. L.; Gasnault, O.; Barraclough, B. L.; Elphic, R. C.; Prettyman, T. H.; Binder, A. B.

2001-05-01

Planetary thermal neutron fluxes provide a sensitive proxy for mafic and feldspathic terranes, and are also necessary for translating measured gamma-ray line strengths to elemental abundances. Both functions require a model for near surface temperatures and a knowledge of the dependence of thermal neutron flux on temperature. We have explored this dependence for a representative sample of lunar soil compositions and surface temperatures using MCNP. For all soil samples, the neutron density is found to be independent of temperature, in accord with neutron moderation theory. The thermal neutron flux, however, does vary with temperature in a way that depends on D, the ratio of macroscopic absorption to energy-loss cross sections of soil compositions. The weakest dependence is for the largest D (which corresponds to the Apollo 17 high Ti basalt in our soil selection), and the largest dependence is for the lowest D (which corresponds to ferroan anorthosite, [FAN] in our selection). For the lunar model simulated, the depth at which the thermal neutron population is most sensitive to temperature is ~30 g/cm**2. These simulations were compared with the flux of thermal neutrons measured using the Lunar Prospector neutron spectrometer over the lunar highlands using a sub-surface temperature profile that varies with latitude, L, as (Cos L)**0.25. The fit is excellent. The best fitting equatorial temperature is determined to be, Teq=224+/-40 K. This temperature range brackets the average temperature measured below the thermal wave at the equator, Tmeas = 252+/-3K [Langseth and Keihm, 1977]. The present result represents the first measurement of subsurface temperature from orbit using neutrons.

Can pair-instability supernova models match the observations of superluminous supernovae?

NASA Astrophysics Data System (ADS)

Kozyreva, Alexandra; Blinnikov, S.

2015-12-01

An increasing number of so-called superluminous supernovae (SLSNe) are discovered. It is believed that at least some of them with slowly fading light curves originate in stellar explosions induced by the pair instability mechanism. Recent stellar evolution models naturally predict pair instability supernovae (PISNe) from very massive stars at wide range of metallicities (up to Z = 0.006, Yusof et al.). In the scope of this study, we analyse whether PISN models can match the observational properties of SLSNe with various light-curve shapes. Specifically, we explore the influence of different degrees of macroscopic chemical mixing in PISN explosive products on the resulting observational properties. We artificially apply mixing to the 250 M⊙ PISN evolutionary model from Kozyreva et al. and explore its supernova evolution with the one-dimensional radiation hydrodynamics code STELLA. The greatest success in matching SLSN observations is achieved in the case of an extreme macroscopic mixing, where all radioactive material is ejected into the hydrogen-helium outer layer. Such an extreme macroscopic redistribution of chemicals produces events with faster light curves with high photospheric temperatures and high photospheric velocities. These properties fit a wider range of SLSNe than non-mixed PISN model. Our mixed models match the light curves, colour temperature, and photospheric velocity evolution of two well-observed SLSNe PTF12dam and LSQ12dlf. However, these models' extreme chemical redistribution may be hard to realize in massive PISNe. Therefore, alternative models such as the magnetar mechanism or wind-interaction may still to be favourable to interpret rapidly rising SLSNe.

Processing Issues for Preliminary Melts of the Intermetallic Compound 60-NITINOL

NASA Technical Reports Server (NTRS)

Stanford, Malcolm K.; Thomas, Fransua; DellaCorte, Christopher

2012-01-01

The effect of various high temperature heat treatments and cooling rates on the hardness of cast 60-NITINOL (60wt%Ni- 40wt%Ti) was studied. The hardness ranged from approximately 33 HRC for annealed specimens to 63 HRC for water quenched specimens. Aging did not have a further effect on the hardness of the heat-treated and quenched material. The issue of material contamination and its possible effect on quench cracking during heat treatment above 1000 C was explored. The Charpy impact energy of the material was found to be relatively low (ranging from 0.4 to 1.0 J) and comparable to that of cast magnesium. Selection of service environments and applications for this material based on these findings should consider the processing route by which it was produced.

A study of the origin of large magnetic field coupled electric polarization in HoAl(BO3)4

NASA Astrophysics Data System (ADS)

Yu, Tian; Zhang, Han; Tyson, Trevor; Chen, Zhiqiang; Abeykoon, Milinda; Nelson, Christie; Bezmaternykh, Leonard

2015-03-01

The multiferroic system RAl(BO3)4 is known to exhibit a strong coupling of magnetic field to the electrical polarization. Recently a giant magnetoelectric effect was found in HoAl3(BO3)4 system. This phenomenon is considered quite interesting because the value discovered is significantly higher than reported values of linear magnetoelectric or even multiferroic compounds. We are conducting detailed structural measurements to understand the coupling. We are exploring the local and long range structure in these systems using x-ray PDF, XAFS and single crystal diffraction measurement between 10 K and 400 K. Structural parameters including lattice parameters and ADPs are being determined over the full temperature range. This work is supported by DOE Grant DE-FG02-07ER46402.

Parameterizing the interstellar dust temperature

NASA Astrophysics Data System (ADS)

Hocuk, S.; Szűcs, L.; Caselli, P.; Cazaux, S.; Spaans, M.; Esplugues, G. B.

2017-08-01

The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction (AV) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths (AV> 20 mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as Td = [ 11 + 5.7 × tanh(0.61 - log 10(AV) ]χuv1/5.9, where χuv is in units of the Draine (1978, ApJS, 36, 595) UV field.

Empirical Temperature Measurement in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Weaver, Erik; Isella, Andrea; Boehler, Yann

2018-02-01

The accurate measurement of temperature in protoplanetary disks is critical to understanding many key features of disk evolution and planet formation, from disk chemistry and dynamics, to planetesimal formation. This paper explores the techniques available to determine temperatures from observations of single, optically thick molecular emission lines. Specific attention is given to issues such as the inclusion of optically thin emission, problems resulting from continuum subtraction, and complications of real observations. Effort is also made to detail the exact nature and morphology of the region emitting a given line. To properly study and quantify these effects, this paper considers a range of disk models, from simple pedagogical models to very detailed models including full radiative transfer. Finally, we show how the use of the wrong methods can lead to potentially severe misinterpretations of data, leading to incorrect measurements of disk temperature profiles. We show that the best way to estimate the temperature of emitting gas is to analyze the line peak emission map without subtracting continuum emission. Continuum subtraction, which is commonly applied to observations of line emission, systematically leads to underestimation of the gas temperature. We further show that once observational effects such as beam dilution and noise are accounted for, the line brightness temperature derived from the peak emission is reliably within 10%–15% of the physical temperature of the emitting region, assuming optically thick emission. The methodology described in this paper will be applied in future works to constrain the temperature, and related physical quantities, in protoplanetary disks observed with ALMA.

Effect of hydrogen limitation and temperature on the fractionation of sulfur isotopes by a deep-sea hydrothermal vent sulfate-reducing bacterium

NASA Astrophysics Data System (ADS)

Hoek, Joost; Reysenbach, Anna-Louise; Habicht, Kirsten S.; Canfield, Donald E.

2006-12-01

The fractionation of sulfur isotopes by the thermophilic chemolithoautotrophic Thermodesulfatator indicus was explored during sulfate reduction under excess and reduced hydrogen supply, and the full temperature range of growth (40-80 °C). Fractionation of sulfur isotopes measured under reduced H 2 conditions in a fed-batch culture revealed high fractionations (24-37‰) compared to fractionations produced under excess H 2 supply (1-6‰). Higher fractionations correlated with lower sulfate reduction rates. Such high fractionations have never been reported for growth on H 2. For temperature-dependant fractionation experiments cell-specific rates of sulfate reduction increased with increasing temperatures to 70 °C after which sulfate-reduction rates rapidly decreased. Fractionations were relatively high at 40 °C and decreased with increasing temperature from 40-60 °C. Above 60 °C, fractionation trends switched and increased again with increasing temperatures. These temperature-dependant fractionation trends have not previously been reported for growth on H 2 and are not predicted by a generally accepted fractionation model for sulfate reduction, where fractionations are controlled as a function of temperature, by the balance of the exchange of sulfate across the cell membrane, and enzymatic reduction rates of sulfate. Our results are reproduced with a model where fractionation is controlled by differences in the temperature response of enzyme reaction rates and the exchange of sulfate in and out of the cell.

On the Wrapping of Polyglycolide, Poly(Ethylene Oxide), and Polyketone Polymer Chains Around Single-Walled Carbon Nanotubes Using Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Rouhi, S.; Alizadeh, Y.; Ansari, R.

2015-02-01

By using molecular dynamics simulations, the interaction between a single-walled carbon nanotube and three different polymers has been studied in this work. The effects of various parameters such as the nanotube geometry and temperature on the interaction energy and radius of gyration of polymers have been explored. By studying the snapshots of polymers along the single-walled carbon nanotube, it has been shown that 50 ps can be considered as a suitable time after which the shape of polymer chains around the nanotube remains almost unchanged. It is revealed that the effect of temperature on the interaction energy and radius of gyration of polymers in the range of 250 to 500 K is not significant Also, it is shown that the interaction energy depends on the nanotube diameter.

Anisotropic stress correlations in two-dimensional liquids

DOE PAGES

Wu, Bin; Iwashita, Takuya; Egami, Takeshi

2015-03-01

In this paper we demonstrate the presence of anisotropic stress correlations in the simulated 2D liquids. Whereas the temporal correlation of macroscopic shear stress is known to contribute to viscosity via the Green-Kubo formula, the general question regarding angular dependence of the spatial correlation among atomic level stresses in liquids without external shear has not been explored. Besides the apparent anisotropicity with well-defined symmetry, we found that the characteristic length of shear stress correlation depends on temperature and follows the power law, suggesting divergence around the glass transition temperature. The anisotropy of the stress correlations can be explained in termsmore » of the inclusion model by Eshelby, based upon which we suggest that the mismatch between the atom and its nearest neighbor cage produces the atomic level stress as well as the long-range stress fields.« less

Weak arrest-like and field-driven first order magnetic phase transitions of itinerant Fe3Ga4 revealed by magnetization and magnetoresistance isotherms

NASA Astrophysics Data System (ADS)

Samatham, S. Shanmukharao; Suresh, K. G.

2017-01-01

The detailed magnetic study of complex 3d-electron based Fe3Ga4 is reported. It undergoes paramagnetic to antiferromagnetic (TN) and antiferromagnetic to ferromagnetic (TC) transitions respectively around 380 and 70 K. The thermal hysteresis of field-cooled cooling (FCC) and field-cooled warming (FCW) hints at first order phase transition below Curie temperature. A weak phase coexistence of ferro and antiferromagnetic phases is suggested by exploring the arrest-like first-order phenomenon. In the intermediate temperature range, field-driven metamagnetic transition from antiferro to ferromagnetic phase is confirmed. Further bringing the system very near to TN, field-induced transitions disappear and above TN predominant paramagnetic contribution is evident. The magnetic H-T phase diagram distinguishing different magnetic phases of Fe3Ga4 is obtained.

Kr-PLIF for scalar imaging in supersonic flows.

PubMed

Narayanaswamy, V; Burns, R; Clemens, N T

2011-11-01

Experiments were performed to explore the use of two-photon planar laser-induced fluorescence (PLIF) of krypton gas for applications of scalar imaging in supersonic flows. Experiments were performed in an underexpanded jet of krypton, which exhibited a wide range of conditions, from subsonic to hypersonic. Excellent signal-to-noise ratios were obtained, showing the technique is suitable for single-shot imaging. The data were used to infer the distribution of gas density and temperature by correcting the fluorescence signal for quenching effects and using isentropic relations. The centerline variation of the density and temperature from the experiments agree very well with those predicted with an empirical correlation and a CFD simulation (FLUENT). Overall, the high signal levels and quantifiable measurements indicate that Kr-PLIF could be an effective scalar marker for use in supersonic and hypersonic flow applications.

Stirling Cooler Designed for Venus Exploration

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.; Mellott, Kenneth D.

2004-01-01

Venus having an average surface temperature of 460 degrees Celsius (about 860 degrees Fahrenheit) and an atmosphere 150 times denser than the Earth's atmosphere, designing a robot to merely survive on the surface to do planetary exploration is an extremely difficult task. This temperature is hundreds of degrees higher than the maximum operating temperature of currently existing microcontrollers, electronic devices, and circuit boards. To meet the challenge of Venus exploration, researchers at the NASA Glenn Research Center studied methods to keep a pressurized electronics package cooled, so that the operating temperature within the electronics enclosure would be cool enough for electronics to run, to allow a mission to operate on the surface of Venus for extended periods.

Identification and future description of warming signatures over Pakistan with special emphasis on evolution of CO2 levels and temperature during the first decade of the twenty-first century.

PubMed

Haider, Khadija; Khokhar, Muhammad Fahim; Chishtie, Farrukh; RazzaqKhan, Waseem; Hakeem, Khalid Rehman

2017-03-01

Like other developing countries, Pakistan is also facing changes in temperature per decade and other climatic abnormalities like droughts and torrential rains. In order to assess and identify the extent of temperature change over Pakistan, the whole Pakistan was divided into five climatic zones ranging from very cold to hot and dry climates. Similarly, seasons in Pakistan are defined on the basis of monsoon variability as winter, pre-monsoon, monsoon, and post-monsoon. This study primarily focuses on the comparison of surface temperature observations from Pakistan Meteorological Department (PMD) network with PRECIS (Providing Regional Climates for Impacts Studies) model simulations. Results indicate that PRECIS underestimates the temperature in Northern Pakistan and during the winter season. However, there exists a fair agreement between PRECIS output and observed datasets in the lower plain and hot areas of the country. An absolute increase of 0.07 °C is observed in the mean temperature over Pakistan during the time period of 1951-2010. Especially, the increase is more significant (0.7 °C) during the last 14 years (1997-2010). Moreover, SCIAMACHY observations were used to explore the evolution of atmospheric CO 2 levels in comparison to temperature over Pakistan. CO 2 levels have shown an increasing trend during the first decade of the twenty-first century.

Photoluminescence studies of a perceived white light emission from a monolithic InGaN/GaN quantum well structure

PubMed Central

Ben Sedrine, N.; Esteves, T. C.; Rodrigues, J.; Rino, L.; Correia, M. R.; Sequeira, M. C.; Neves, A. J.; Alves, E.; Bockowski, M.; Edwards, P. R.; O’Donnell, K. P.; Lorenz, K.; Monteiro, T.

2015-01-01

In this work we demonstrate by photoluminescence studies white light emission from a monolithic InGaN/GaN single quantum well structure grown by metal organic chemical vapour deposition. As-grown and thermally annealed samples at high temperature (1000 °C, 1100 °C and 1200 °C) and high pressure (1.1 GPa) were analysed by spectroscopic techniques, and the annealing effect on the photoluminescence is deeply explored. Under laser excitation of 3.8 eV at room temperature, the as-grown structure exhibits two main emission bands: a yellow band peaked at 2.14 eV and a blue band peaked at 2.8 eV resulting in white light perception. Interestingly, the stability of the white light is preserved after annealing at the lowest temperature (1000 °C), but suppressed for higher temperatures due to a deterioration of the blue quantum well emission. Moreover, the control of the yellow/blue bands intensity ratio, responsible for the white colour coordinate temperatures, could be achieved after annealing at 1000 °C. The room temperature white emission is studied as a function of incident power density, and the correlated colour temperature values are found to be in the warm white range: 3260–4000 K. PMID:26336921

High-Temperature Shape Memory Behavior of Semicrystalline Polyamide Thermosets.

PubMed

Li, Ming; Guan, Qingbao; Dingemans, Theo J

2018-05-21

We have explored semicrystalline poly(decamethylene terephthalamide) (PA 10T) based thermosets as single-component high-temperature (>200 °C) shape memory polymers (SMPs). The PA 10T thermosets were prepared from reactive thermoplastic precursors. Reactive phenylethynyl (PE) functionalities were either attached at the chain termini or placed as side groups along the polymer main chain. The shape fixation and recovery performance of the thermoset films were investigated using a rheometer in torsion mode. By controlling the M n of the reactive oligomers, or the PE concentration of the PE side-group functionalized copolyamides, we were able to design dual-shape memory PA 10T thermosets with a broad recovery temperature range of 227-285 °C. The thermosets based on the 1000 g mol -1 reactive PE precursor and the copolyamide with 15 mol % PE side groups show the highest fixation rate (99%) and recovery rate (≥90%). High temperature triple-shape memory behavior can be achieved as well when we use the melt transition ( T m ≥ 200 °C) and the glass transition ( T g = ∼125 °C) as the two switches. The recovery rate of the two recovery steps are highly dependent on the crystallinity of the thermosets and vary within a wide range of 74%-139% and 40-82% for the two steps, respectively. Reversible shape memory events could also be demonstrated when we perform a forward and backward deformation in a triple shape memory cycle. We also studied the angular recovery velocity as a function of temperature, which provides a thermokinematic picture of the shape recovery process and helps to program for desired shape memory behavior.

Synthesis and Screening of Phase Change Chalcogenide Thin Film Materials for Data Storage.

PubMed

Guerin, Samuel; Hayden, Brian; Hewak, Daniel W; Vian, Chris

2017-07-10

A combinatorial synthetic methodology based on evaporation sources under an ultrahigh vacuum has been used to directly synthesize compositional gradient thin film libraries of the amorphous phases of GeSbTe alloys at room temperature over a wide compositional range. An optical screen is described that allows rapid parallel mapping of the amorphous-to-crystalline phase transition temperature and optical contrast associated with the phase change on such libraries. The results are shown to be consistent with the literature for compositions where published data are available along the Sb 2 Te 3 -GeTe tie line. The results reveal a minimum in the crystallization temperature along the Sb 2 Te 3 -Ge 2 Te 3 tie line, and the method is able to resolve subsequent cubic-to-hexagonal phase transitions in the GST crystalline phase. HT-XRD has been used to map the phases at sequentially higher temperatures, and the results are reconciled with the literature and trends in crystallization temperatures. The results clearly delineate compositions that crystallize to pure GST phases and those that cocrystallize Te. High-throughput measurement of the resistivity of the amorphous and crystalline phases has allowed the compositional and structural correlation of the resistivity contrast associated with the amorphous-to-crystalline transition, which range from 5-to-8 orders of magnitude for the compositions investigated. The results are discussed in terms of the compromises in the selection of these materials for phase change memory applications and the potential for further exploration through more detailed secondary screening of doped GST or similar classes of phase change materials designed for the demands of future memory devices.

High-Temperature Shape Memory Behavior of Semicrystalline Polyamide Thermosets

PubMed Central

2018-01-01

We have explored semicrystalline poly(decamethylene terephthalamide) (PA 10T) based thermosets as single-component high-temperature (>200 °C) shape memory polymers (SMPs). The PA 10T thermosets were prepared from reactive thermoplastic precursors. Reactive phenylethynyl (PE) functionalities were either attached at the chain termini or placed as side groups along the polymer main chain. The shape fixation and recovery performance of the thermoset films were investigated using a rheometer in torsion mode. By controlling the Mn of the reactive oligomers, or the PE concentration of the PE side-group functionalized copolyamides, we were able to design dual-shape memory PA 10T thermosets with a broad recovery temperature range of 227–285 °C. The thermosets based on the 1000 g mol–1 reactive PE precursor and the copolyamide with 15 mol % PE side groups show the highest fixation rate (99%) and recovery rate (≥90%). High temperature triple-shape memory behavior can be achieved as well when we use the melt transition (Tm ≥ 200 °C) and the glass transition (Tg = ∼125 °C) as the two switches. The recovery rate of the two recovery steps are highly dependent on the crystallinity of the thermosets and vary within a wide range of 74%–139% and 40–82% for the two steps, respectively. Reversible shape memory events could also be demonstrated when we perform a forward and backward deformation in a triple shape memory cycle. We also studied the angular recovery velocity as a function of temperature, which provides a thermokinematic picture of the shape recovery process and helps to program for desired shape memory behavior. PMID:29742899

Spectral fingerprints of Earth-like planets around FGK stars.

PubMed

Rugheimer, Sarah; Kaltenegger, Lisa; Zsom, Andras; Segura, Antígona; Sasselov, Dimitar

2013-03-01

We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from Teff=4250 K to Teff=7000 K in 250 K intervals. We have modeled the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1 AU equivalent distance from the VIS to IR (0.4 to 20 μm) to compare detectability of features in different wavelength ranges in accordance with the James Webb Space Telescope and future design concepts to characterize exo-Earths. We have also explored the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere, concentrating on detectable atmospheric features that indicate habitability on Earth, namely, H2O, O3, CH4, N2O, and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O, and CH3Cl, whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase is a lower surface temperature of the planet due to a bigger part of the stellar flux being reflected at short wavelengths, as well as increased photolysis. Earth-like atmosphere models show more O3 and OH but less stratospheric CH4, N2O, CH3Cl, and tropospheric H2O (but more stratospheric H2O) with increasing effective temperature of main sequence stars. The corresponding detectable spectral features, on the other hand, show different detectability depending on the wavelength observed. We concentrate on directly imaged planets here as a framework to interpret future light curves, direct imaging, and secondary eclipse measurements of atmospheres of terrestrial planets in the habitable zone at varying orbital positions.

Thermal sensitivity of cold climate lizards and the importance of distributional ranges.

PubMed

Bonino, Marcelo F; Moreno Azócar, Débora L; Schulte, James A; Abdala, Cristian S; Cruz, Félix B

2015-08-01

One of the fundamental goals in macroecology is to understand the relationship among species' geographic ranges, ecophysiology, and climate; however, the mechanisms underlying the distributional geographic patterns observed remain unknown for most organisms. In the case of ectotherms this is particularly important because the knowledge of these interactions may provide a robust framework for predicting the potential consequences of climate change in these organisms. Here we studied the relationship of thermal sensitivity and thermal tolerance in Patagonian lizards and their geographic ranges, proposing that species with wider distributions have broader plasticity and thermal tolerance. We predicted that lizard thermal physiology is related to the thermal characteristics of the environment. We also explored the presence of trade-offs of some thermal traits and evaluated the potential effects of a predicted scenario of climate change for these species. We examined sixteen species of Liolaemini lizards from Patagonia representing species with different geographic range sizes. We obtained thermal tolerance data and performance curves for each species in laboratory trials. We found evidence supporting the idea that higher physiological plasticity allows species to achieve broader distribution ranges compared to species with restricted distributions. We also found a trade-off between broad levels of plasticity and higher optimum temperatures of performance. Finally, results from contrasting performance curves against the highest environmental temperatures that lizards may face in a future scenario (year 2080) suggest that the activity of species occurring at high latitudes may be unaffected by predicted climatic changes. Copyright © 2015 Elsevier GmbH. All rights reserved.

Sensitivity of New England Stream Temperatures to Air Temperature and Precipitation Under Projected Climate

NASA Astrophysics Data System (ADS)

Huang, T.; Samal, N. R.; Wollheim, W. M.; Stewart, R. J.; Zuidema, S.; Prousevitch, A.; Glidden, S.

2015-12-01

The thermal response of streams and rivers to changing climate will influence aquatic habitat. This study examines the impact that changing climate has on stream temperatures in the Merrimack River, NH/MA USA using the Framework for Aquatic Modeling in the Earth System (FrAMES), a spatially distributed river network model driven by air temperature, air humidity, wind speed, precipitation, and solar radiation. Streamflow and water temperatures are simulated at a 45-second (latitude x longitude) river grid resolution for 135 years under historical and projected climate variability. Contemporary streamflow (Nash-Sutcliffe Coefficient = 0.77) and river temperatures (Nash-Sutcliffe Coefficient = 0.89) matched at downstream USGS gauge data well. A suite of model runs were made in combination with uniformly increased daily summer air temperatures by 2oC, 4 oC and 6 oC as well as adjusted precipitation by -40%, -30%, -20%, -10% and +10% as a sensitivity analysis to explore a broad range of potential future climates. We analyzed the summer stream temperatures and the percent of river length unsuitable for cold to warm water fish habitats. Impacts are greatest in large rivers due to the accumulation of river temperature warming throughout the entire river network. Cold water fish (i.e. brook trout) are most strongly affected while, warm water fish (i.e. largemouth bass) aren't expected to be impacted. The changes in stream temperatures under various potential climate scenarios will provide a better understanding of the specific impact that air temperature and precipitation have on aquatic thermal regimes and habitat.

Exploring high-strength glass-ceramic materials for upcycling of industrial wastes

NASA Astrophysics Data System (ADS)

Back, Gu-Seul; Park, Hyun Seo; Seo, Sung Mo; Jung, Woo-Gwang

2015-11-01

To promote the recycling of industrial waste and to develop value-added products using these resources, the possibility of manufacturing glass-ceramic materials of SiO2-CaO-Al2O3 system has been investigated by various heat treatment processes. Glass-ceramic materials with six different chemical compositions were prepared using steel industry slags and power plant waste by melting, casting and heat treatment. The X-ray diffraction results indicated that diopside and anorthite were the primary phases in the samples. The anorthite phase was formed in SiO2-rich material (at least 43 wt%). In CaO-rich material, the gehlenite phase was formed. By the differential scanning calorimetry analyses, it was found that the glass transition point was in the range of 973-1023 K, and the crystallization temperature was in the range of 1123-1223 K. The crystallization temperature increased as the content of Fe2O3 decreased. By the multi-step heat treatment process, the formation of the anorthite phase was enhanced. Using FactSage, the ratio of various phases was calculated as a function of temperature. The viscosities and the latent heats for the samples with various compositions were also calculated by FactSage. The optimal compositions for glass-ceramics materials were discussed in terms of their compressive strength, and micro-hardness.

High-pressure and high-temperature physical properties of LiF studied by density functional theory calculations and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Sun, Xiao-Wei; Liu, Zi-Jiang; Quan, Wei-Long; Song, Ting; Khenata, Rabah; Bin-Omran, Saad

2018-05-01

Using the revised Perdew-Burke-Ernzerhof generalized gradient approximation based on first-principles plane-wave pseudopotential density functional theory, the high-pressure structural phase transition of LiF is explored. From the analysis of Gibbs free energies, we find that no phase transition occurs for LiF in the presented pressure range from 0 to 1000 GPa, and this result is consistent with the theoretical prediction obtained via ab initio calculations [N.A. Smirnov, Phys. Rev. B 83 (2011) 014109]. Using the classical molecular dynamics technique with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction, the melting phase diagram of LiF is determined. The obtained normalized volumes under pressure are in good agreement with our density functional theory results and the available experimental data. Meanwhile, with the help of the quasi-harmonic Debye model in which the phononic effects are considered, the thermodynamic properties of interest, including the volume thermal expansion coefficient, isothermal bulk modulus and its first and second pressure derivatives, heat capacity at constant volume, entropy, Debye temperature, and Grüneisen parameter of LiF are predicted systematically. All the properties of LiF with the stable NaCl-type structure in the temperature range of 0-4900 K and the pressure up to 1000 GPa are summarized.

Pasta nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

NASA Astrophysics Data System (ADS)

Caplan, M. E.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K.

2015-06-01

Background: Exotic nonspherical nuclear pasta shapes are expected in nuclear matter at just below saturation density because of competition between short-range nuclear attraction and long-range Coulomb repulsion. Purpose: We explore the impact nuclear pasta may have on nucleosynthesis during neutron star mergers when cold dense nuclear matter is ejected and decompressed. Methods: We use a hybrid CPU/GPU molecular dynamics (MD) code to perform decompression simulations of cold dense matter with 51 200 and 409 600 nucleons from 0.080 fm-3 down to 0.00125 fm-3 . Simulations are run for proton fractions YP= 0.05, 0.10, 0.20, 0.30, and 0.40 at temperatures T = 0.5, 0.75, and 1.0 MeV. The final composition of each simulation is obtained using a cluster algorithm and compared to a constant density run. Results: Size of nuclei in the final state of decompression runs are in good agreement with nuclear statistical equilibrium (NSE) models for temperatures of 1 MeV while constant density runs produce nuclei smaller than the ones obtained with NSE. Our MD simulations produces unphysical results with large rod-like nuclei in the final state of T =0.5 MeV runs. Conclusions: Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.

Electrical conductivity of high-purity germanium crystals at low temperature

NASA Astrophysics Data System (ADS)

Yang, Gang; Kooi, Kyler; Wang, Guojian; Mei, Hao; Li, Yangyang; Mei, Dongming

2018-05-01

The temperature dependence of electrical conductivity of single-crystal and polycrystalline high-purity germanium (HPGe) samples has been investigated in the temperature range from 7 to 100 K. The conductivity versus inverse of temperature curves for three single-crystal samples consist of two distinct temperature ranges: a high-temperature range where the conductivity increases to a maximum with decreasing temperature, and a low-temperature range where the conductivity continues decreasing slowly with decreasing temperature. In contrast, the conductivity versus inverse of temperature curves for three polycrystalline samples, in addition to a high- and a low-temperature range where a similar conductive behavior is shown, have a medium-temperature range where the conductivity decreases dramatically with decreasing temperature. The turning point temperature ({Tm}) which corresponds to the maximum values of the conductivity on the conductivity versus inverse of temperature curves are higher for the polycrystalline samples than for the single-crystal samples. Additionally, the net carrier concentrations of all samples have been calculated based on measured conductivity in the whole measurement temperature range. The calculated results show that the ionized carrier concentration increases with increasing temperature due to thermal excitation, but it reaches saturation around 40 K for the single-crystal samples and 70 K for the polycrystalline samples. All these differences between the single-crystal samples and the polycrystalline samples could be attributed to trapping and scattering effects of the grain boundaries on the charge carriers. The relevant physical models have been proposed to explain these differences in the conductive behaviors between two kinds of samples.

Resilience of a High Latitude Red Sea Frining Corals Exposed to Extreme Temperatures

NASA Astrophysics Data System (ADS)

Moustafa, M.; Moustafa, M. S.; Moustafa, S.; Moustafa, Z. D.

2013-05-01

Since 2004, multi-year study set out to establish linkages between fringing coral reefs in the northern Gulf of Suez, Red Sea, and local weather. Insight into local meteorological processes may provide a better understanding of the direct influence weather has on a fringing coral reef. To establish trends, seawater temperature and meteorological record were collected at a small fringing coral reef (Zaki's Reef), located near Ein Sokhna, Egypt (29.5oN & 32.4oE). Monitoring air and water temperature provides evidence of seasonality and interannual variability and may reveal correlations between reef health and climate conditions in this region. Prior to this study, there were no known long-term studies investigating coral reefs in this region. Approximately 35 coral taxa are known to survive the extreme temperature and salinity regime found here, yet only six corals compose 94% of coral cover on Zaki's Reef. Dominant corals include: Acropora humilis, A. microclados, A. hemprichii, Litophyton arboretum, Stylophora pistillata, Porites columna, and P. plantulata. Seawater temperatures were collected at 30 minutes intervals at 5 locations. Seawater temperature data indicate that corals experience 4-6.5oC daily temperature variations and seasonal variations that exceed 29oC. Air temperatures were collected just landward of the reef were compared to Hurghada and Ismailia 400 and 200 km south and north of the study site, respectively. Time series analysis results indicate that air temperature dominant frequencies are half-daily, daily, and yearly cycles, while water temperatures show yearly cycles. A comparison of air temperature with neighboring locations indicates that air temperatures at Ein Sokhna ranged between near 0o C to an excess of 55o C, yet, daily means for Ein Sokhna and Hurghada were very similar (24.2o C and. 25.2o C, respectively). Maximum daily air temperatures at the study site exceeded maximum air temperature at Hurghada (400 km south) by almost 7o C, while minimum daily means at Ein Sokhna were almost equal to those at Ismailia (200 km north). These trends were opposite to what was expected considering each stations geographical locations. The unexpected temperature trends, the daily/half daily dominant frequencies, and the short distance between the mountain range and Zaki's Reef vs. Hurghada (0.5 vs. 35 km), prompted us to hypothesize that a Foehn wind may be responsible for the high air temperatures observed at Ein Sokhna. We applied NOAA's HYSPLIT model to explore local circulation patterns, which suggest that the high mountain range blocks the year-round trade wind and forces it to climb up the western slope, where it loses moisture and reduces its temperature. As this cool, denser air reaches the mountain top, the air parcel starts rolling down the eastern slopes, which causes air temperature to rise and result in an increase in local air temperatures. These warmer than normal air temperatures measured here may aid in securing these northernmost reefs survival. Further scrutiny of the mechanisms by which area reefs are able to thrive extreme environmental conditions continues to be investigated.

The Effect of Temperature and Hydrogen Limited Growth on the Fractionation of Sulfur Isotopes by Thermodesulfatator indicus, a Deep-sea Hydrothermal Vent Sulfate-Reducing Bacterium

NASA Astrophysics Data System (ADS)

Hoek, J.; Reysenbach, A.; Habicht, K.; Canfield, D. E.

2004-12-01

Sulfate-reducing bacteria fractionate sulfur isotopes during dissimilatory sulfate reduction, producing sulfide depleted in 34S. Although isotope fractionation during sulfate reduction of pure cultures has been extensively studied, most of the research to date has focused on mesophilic sulfate reducers, particularly for the species Desulfovibrio desulfuricans. Results from these studies show that: 1) fractionations range from 3-46‰ with an average around 18‰ , 2) when organic electron donors are utilized, the extent of fractionation is dependent on the rate of sulfate reduction, with decreasing fractionations observed with higher specific rates, 3) fractionations are suppressed with low sulfate concentrations, and when hydrogen is used as the electron donor. High specific sulfate-reduction rates are encountered when sulfate-reducing bacteria metabolize at their optimal temperature and under non-limiting substrate conditions. Changes in both temperature and substrate availability could shift fractionations from those expressed under optimal growth conditions. Sulfate reducers may frequently experience substrate limitation and sub-optimal growth temperatures in the environment. Therefore it is important to understand how sulfate-reducing bacteria fractionate sulfur isotopes under conditions that more closely resemble the restrictions imposed by the environment. In this study the fractionation of sulfur isotopes by Thermodesulfatator indicus was explored during sulfate reduction under a wide range of temperatures and with both hydrogen-saturating and hydrogen-limited conditions. T. indicus is a thermophilic (temperature optimum = 70° C) chemolithotrophic sulfate-reducing bacterium, which was recently isolated from a deep-sea hydrothermal vent on the Central Indian Ridge. This bacterium represents the type species of a new genus and to date is the most deeply branching sulfate-reducing bacterium known. T. indicus was grown in carbonate-buffered salt-water medium with H2 as the sole electron donor, and CO2 as primary carbon source. The fractionation of sulfur isotopes was measured in batch cultures and in a thermal gradient block over the full temperature range of growth (40-80° C). For experiments in the gradient block, cell-specific rates of sulfate reduction increased with increasing temperatures to 70° C after which sulfate-reduction rates rapidly decreased. The range of fractionations (1.5-10‰ ) was typical for growth with hydrogen as the electron donor. Fractionations decreased with increasing temperature from 40--60° C, and increased with increasing temperatures from 60-80° C. Growth under H2-limited conditions in a fed-batch culture revealed high fractionations of 24-37‰ . This is the first report of sulfur isotope fractionation under H2 limited growth and indicates that large fractionations are produced when H2 is supplied as a limiting substrate. Our results suggest that fractionation is controlled by the competition of forward and reverse enzymatic reaction rates during sulfate reduction and by sulfate transport into the cell.

MUSE: the Multi-Slit Solar Explorer

NASA Astrophysics Data System (ADS)

Tarbell, Theodore D.; De Pontieu, Bart

2017-08-01

The Multi-Slit Solar Explorer is a proposed Small Explorer mission for studying the dynamics of the corona and transition region using both conventional and novel spectral imaging techniques. The physical processes that heat the multi-million degree solar corona, accelerate the solar wind and drive solar activity (CMEs and flares) remain poorly known. A breakthrough in these areas can only come from radically innovative instrumentation and state-of-the-art numerical modeling and will lead to better understanding of space weather origins. MUSE’s multi-slit coronal spectroscopy will use a 100x improvement in spectral raster cadence to fill a crucial gap in our knowledge of Sun-Earth connections; it will reveal temperatures, velocities and non-thermal processes over a wide temperature range to diagnose physical processes that remain invisible to current or planned instruments. MUSE will contain two instruments: an EUV spectrograph (SG) and EUV context imager (CI). Both have similar spatial resolution and leverage extensive heritage from previous high-resolution instruments such as IRIS and the HiC rocket payload. The MUSE investigation will build on the success of IRIS by combining numerical modeling with a uniquely capable observatory: MUSE will obtain EUV spectra and images with the highest resolution in space (1/3 arcsec) and time (1-4 s) ever achieved for the transition region and corona, along 35 slits and a large context FOV simultaneously. The MUSE consortium includes LMSAL, SAO, Stanford, ARC, HAO, GSFC, MSFC, MSU, ITA Oslo and other institutions.

Accounts from 19th-century Canadian Arctic explorers' logs reflect present climate conditions

NASA Astrophysics Data System (ADS)

Overland, James E.; Wood, Kevin

The widely perceived failure of 19th-century expeditions to find and transit the Northwest Passage in the Canadian Arctic is often attributed to extraordinary cold climatic conditions associated with the “Little Ice Age” evident in proxy records. However, examination of 44 explorers' logs for the western Arctic from 1818 to 1910 reveals that climate indicators such as navigability, the distribution and thickness of annual sea ice, monthly surface air temperature, and the onset of melt and freeze were within the present range of variability.The quest for the Northwest Passage through the Canadian archipelago during the 19th century is frequently seen as a vain and tragic failure. Polar exploration during the Victorian era seems to us today to have been a costly exercise in heroic futility, which in many respects it was. This perspective has been reinforced since the 1970s, when paleoclimate reconstructions based on Arctic ice core stratigraphy appeared to confirm the existence of exceptionally cold conditions consistent with the period glaciologists had termed the “Little Ice Age” (Figure 1a), with temperatures more than one standard deviation colder relative to an early 20th-century mean [Koerner, 1977; Koerner and Fisher, 1990; Overpeck et al., 1998]. In recent years, the view of the Little Ice Age as a synchronous worldwide and prolonged cold epoch that ended with modern warming has been questioned [Bradley and Jones, 1993; Jones and Briffa, 2001 ;Ogilvie, 2001].

Laboratory measurements of ice tensile strength dependence on density and concentration of silicate and polymer impurities at low temperatures

NASA Astrophysics Data System (ADS)

Litwin, K. L.; Beyeler, J. D.; Polito, P. J.; Zygielbaum, B. R.; Sklar, L. S.; Collins, G. C.

2009-12-01

The tensile strength of ice bedrock on Titan should strongly influence the effectiveness of the erosional processes responsible for carving the extensive fluvial drainage networks and other surface features visible in images returned by the Cassini and Huygens probes. Recent measurements of the effect of temperature on the tensile strength of low-porosity, polycrystalline ice, without impurities, suggest that ice bedrock at the Titan surface temperature of 93 K may be as much as five times stronger than ice at terrestrial surface temperatures. However, ice bedrock on Titan and other outer solar system bodies may have significant porosity, and impurities such silicates or polymers are possible in such ices. In this laboratory investigation we are exploring the dependence of tensile strength on the density and concentration of impurities, for polycrystalline ice across a wide range of temperatures. We use the Brazilian tensile splitting test to measure strength, and control temperature with dry ice and liquid nitrogen. The 50 mm diameter ice cores are made from a log-normally distributed seed crystal mixture with a median size of 1.4 mm. To control ice density and porosity we vary the packing density of the seed grains in core molds and vary the degree of saturation of the matrix with added near-freezing distilled water. We also vary ice density by blending in a similarly-sized mixture of angular fragments of two types of impurities, a fine-grained volcanic rock and a polyethylene polymer. Because both types of impurities have greater tensile strength than ice at Earth surface temperatures, we expect higher concentrations of impurities to correlate with increased strength for ice-rock and ice-polymer mixtures. However, at the ultra-cold temperatures of the outer planets, we expect significant divergence in the temperature dependence of ice tensile strength for the various mixtures and resulting densities. These measurements will help constrain the range of possible ice tensile strengths that might occur on Titan and other solar system bodies.

Climatic and topographical correlates of plant palaeo- and neoendemism in a Mediterranean biodiversity hotspot

PubMed Central

Molina-Venegas, Rafael; Aparicio, Abelardo; Lavergne, Sébastien; Arroyo, Juan

2017-01-01

Background and Aims Understanding the evolutionary and ecological forces contributing to the emergence of biodiversity hotspots is of outstanding importance to elucidate how they may withstand current climate changes. Here we explored patterns of phylogenetic and non-phylogenetic plant endemism in a Mediterranean biodiversity hotspot. We hypothesized that areas with wet and equable climatic conditions would be prone to long-term persistence of endemic lineages (palaeoendemism), whilst areas of recent local speciation (neoendemism) would be more related to harsher environmental conditions and to high topographical relief promoting speciation. Methods We focused on the Baetic–Rifan biodiversity hotspot (southern Iberian Peninsula and northern Morocco) in combination with molecular phylogenetic information and relative phylogenetic endemism (RPE), a recent phylogenetic measure of endemism, allowing us to discern centres of palaeo- from those of neoendemism. Using eco-geographical regions as study units, we explored correlations between both RPE and endemic species richness with precipitation- and temperature-related variables and with elevation range. Key Results Centres of neoendemism were concentrated towards the easternmost part of the hotspot, while centres of palaeoendemism were clustered in the vicinity of the Strait of Gibraltar. The RPE index, indicating more palaeoendemism, was positively correlated with total annual precipitation, while endemic species richness showed a poor correlation. In contrast, elevation range and mean annual temperature were poor predictors of RPE, despite elevation range showing a strong correlation with endemic species richness. Conclusions The Baetic–Rifan biodiversity hotspot shows clearly differentiated centres of neo- and palaeoendemism. Topographical relief may have driven evolutionary diversification of newly evolved species, while water availability seems more critical for the long-term persistence of ancient lineages in refuge areas of smoother topography. Given climatic trends towards increasing aridification, conservation planners should pay particular attention to preserve areas retaining older phylogenetic lineages, as these areas act as ‘natural museums’ of biodiversity within the Baetic–Rifan biodiversity hotspot. PMID:27288510

Passive thermal management using phase change materials

NASA Astrophysics Data System (ADS)

Ganatra, Yash Yogesh

The trend of enhanced functionality and reducing thickness of mobile devices has. led to a rapid increase in power density and a potential thermal bottleneck since. thermal limits of components remain unchanged. Active cooling mechanisms are not. feasible due to size, weight and cost constraints. This work explores the feasibility. of a passive cooling system based on Phase Change Materials (PCMs) for thermal. management of mobile devices. PCMs stabilize temperatures due to the latent heat. of phase change thus increasing the operating time of the device before threshold. temperatures are exceeded. The primary contribution of this work is the identification. of key parameters which influence the design of a PCM based thermal management. system from both the experiments and the numerical models. This work first identifies strategies for integrating PCMs in an electronic device. A. detailed review of past research, including experimental techniques and computational. models, yields key material properties and metrics to evaluate the performance of. PCMs. Subsequently, a miniaturized version of a conventional thermal conductivity. measurement technique is developed to characterize thermal resistance of PCMs. Further, latent heat and transition temperatures are also characterized for a wide. range of PCMs. In-situ measurements with PCMs placed on the processor indicate that some. PCMs can extend the operating time of the device by as much as a factor of 2.48. relative to baseline tests (with no PCMs). This increase in operating time is investigated. by computational thermal models that explore various integration locations, both at the package and device level.

Detecting deep sea hydrothermal vents with a split-beam echosounder

NASA Astrophysics Data System (ADS)

Gray, L. M.; Jerram, K.

2016-12-01

In May 2016, the NOAA Office of Exploration and Research exploration vessel, Okeanos Explorer, conducted a remotely operated vehicle (ROV) dive on a series of active `black smoker' hydrothermal vents at 3,300 m depth in the western Pacific Ocean near the Mariana Trench. The ROV system traversed 800 m along the seafloor and detected three distinct vent sites. The vent chimneys ranged in heights from 5 m to 30 m above the seafloor and vent fluid temperatures were measured as high as 337 °C. Immediately following the ROV dive, the Okeanos Explorer mapped the vent field with an 18 kHz split-beam echosounder traditionally used for fishery research and a 30 kHz multibeam echosounder with midwater capability. Six passes were made over the field, transiting at 4-5 knots on various headings. There was a clear and repeatable signal in the split-beam echogram from the venting but less obvious indication in the multibeam data. `Black smokers' have traditionally been detected using repeat conductivity-temperature-depth (CTD) `tow-yo' casts. Our field observations suggest an alternative, and potentially more efficient, method of detecting hydrothermal vent plumes within the beamwidth of the split-beam echosounder to inform ROV dive plans. Methods previously applied for locating marine gas seeps on the seafloor with split-beam echosounders can be applied to estimate the hydrothermal vent positions in this dataset and compared to the recorded ROV positions at each site. Additionally, assuming relatively stable venting and ambient conditions, the ROV position and CTD data recorded from the vehicles can be used to better understand the observed midwater acoustic backscatter signatures of the hydrothermal vent plumes.

Validation of the Explorer® 2.0 test coupled to e-Reader® for the screening of antimicrobials in muscle from different animal species.

PubMed

Mata, Luis; Sanz, David; Razquin, Pedro

2014-01-01

The Explorer(®) 2.0 tube test is a microbial inhibition test for the screening of antimicrobial residues in food samples. The new e-Reader(®) device coupled to Explorer(®) 2.0 operates by incubation at a selected temperature, determination of the endpoint of the assay and interpretation to generate results. This system was validated for muscle samples according to the European Commission Decision 2002/657/EC. Sensitivity towards 25 substances from several groups of antimicrobials was investigated in a first step. Detection capabilities for six substances representing the six major antimicrobial groups were also determined in bovine muscle. The detection capabilities for amoxicillin (10 µg l(-1)), cefalexin (200 µg l(-1)), doxycyclin (100 µg l(-1)), sulfamethazine (100 µg l(-1)), tylosin (100 µg l(-1)) and neomycin (200 µg l(-1)) were in all cases at or below the maximum residue limit (MRL). Specificity and applicability of the test were demonstrated with muscle samples from four animal species (bovine, porcine, ovine and poultry) and results were found to be satisfactory. Ruggedness was evaluated on negative and spiked samples with sulfamethazine as a representative antimicrobial. Neither false-positives nor false-negatives were detected when varying the sample volume, the time of pre-incubation, the temperature of incubation and the batch of the test. These results prove that Explorer(®) 2.0 coupled to e-Reader(®) is a valuable tool for the screening of a broad range of antimicrobials in muscle. This new methodology simplifies the analysis and increases the accuracy of interpretation of the test results since the endpoint of the assay is automatically determined and results are interpreted objectively.

An exploratory study on low-concentration hexavalent chromium adsorption by Fe(III)-cross-linked chitosan beads

PubMed Central

Zhang, Yuanjing; Qian, Jin; Xin, Xu; Hu, Sihai; Zhang, Shuai; Wei, Jianguo

2017-01-01

In this study, Fe(III)-cross-linked chitosan beads (Fe(III)-CBs) were synthesized and employed to explore the characteristics and primary mechanism of their hexavalent chromium (Cr(VI)) adsorption under low concentration Cr(VI) (less than 20.0 mg l−1) and a pH range from 2.0 to 8.0. Batch tests were conducted to determine the Cr(VI) adsorption capacity and kinetics, and the effects of pH and temperature on the adsorption under low concentration Cr(VI) and a pH range from 2.0 to 8.0. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to explore the characteristics of Fe(III)-CBs and their Cr(VI) adsorption mechanisms. The results show that, unlike the adsorption of other absorbents, the Cr(VI) adsorption was efficient in a wide pH range from 2.0 to 6.0, and well described by the pseudo-first-order model and the Langmuir–Freundlich isotherm model. The capacity of Cr(VI) adsorption by Fe(III)-CBs was as high as 166.3 mg g−1 under temperature 25°C and pH 6.0. The desorption test was also carried out by 0.1 mol l−1 NaOH solution for Fe(III)-CBs regeneration. It was found that Fe(III)-CBs could be re-used for five adsorption–desorption cycles without significant decrease in Cr(VI) adsorption capacity. Ion exchange was confirmed between functional groups (i.e. amino group) and Cr(VI) anions (i.e. CrO42−). The amino-like functional groups played a key role in Cr(VI) distribution on the Fe(III)-CBs surface; Cr(VI) adsorbed on Fe(III)-CBs was partially reduced to Cr(III) with alcoholic group served as electron donor, and then formed another rate-limiting factor. So, Fe(III)-CBs has a good prospect in purifying low concentration Cr(VI) water with a pH range from 2.0 to 6.0. PMID:29291084

X-ray absorption spectroscopy and neutron diffraction study of the perovskite-type rare-earth cobaltites

NASA Astrophysics Data System (ADS)

Sikolenko, V.; Efimova, E.; Franz, A.; Ritter, C.; Troyanchuk, I. O.; Karpinsky, D.; Zubavichus, Y.; Veligzhanin, A.; Tiutiunnikov, S. I.; Sazonov, A.; Efimov, V.

2018-05-01

Correlations between local and long-range structure distortions in the perovskite-type RE1-xSrxCoO3-δ (RE = La, Pr, Nd; x = 0.0 and 0.5) compounds have been studied at room temperature by extended X-ray absorption fine structure (EXAFS) at the Co K-edge and high-resolution neutron powder diffraction (NPD). The use of two complementary experimental techniques allowed us to explore the influence of the type of rare-earth element and strontium substitution on unusual behavior of static and dynamic features of both the Co-O bond lengths.

Berezinskii-Kosterlitz-Thouless transition in the time-reversal-symmetric Hofstadter-Hubbard model

NASA Astrophysics Data System (ADS)

Iskin, M.

2018-01-01

Assuming that two-component Fermi gases with opposite artificial magnetic fields on a square optical lattice are well described by the so-called time-reversal-symmetric Hofstadter-Hubbard model, we explore the thermal superfluid properties along with the critical Berezinskii-Kosterlitz-Thouless (BKT) transition temperature in this model over a wide range of its parameters. In particular, since our self-consistent BCS-BKT approach takes the multiband butterfly spectrum explicitly into account, it unveils how dramatically the interband contribution to the phase stiffness dominates the intraband one with an increasing interaction strength for any given magnetic flux.

A high-performance wave guide cryogenic thermal break

NASA Astrophysics Data System (ADS)

Melhuish, S. J.; McCulloch, M. A.; Piccirillo, L.; Stott, C.

2016-10-01

We describe a high-performance wave guide cryogenic thermal break. This has been constructed both for Ka band, using WR28 wave guide, and Q band, using WR22 wave guide. The mechanical structure consists of a hexapod (Stewart platform) made from pultruded carbon fibre tubing. We present a tentative examination of the cryogenic Young's modulus of this material. The thermal conductivity is measured at temperatures above the range explored by Runyan and Jones, resulting in predicted conductive loads through our thermal breaks of 3.7 mW to 3 K and 17 μK to 1 K.

Development and Testing of Mechanism Technology for Space Exploration in Extreme Environments

NASA Technical Reports Server (NTRS)

Tyler, Tony R.; Levanas, Greg; Mojarradi, Mohammad M.; Abel, Phillip B.

2011-01-01

The NASA Jet Propulsion Lab (JPL), Glenn Research Center (GRC), Langley Research Center (LaRC), and Aeroflex, Inc. have partnered to develop and test actuator hardware that will survive the stringent environment of the moon, and which can also be leveraged for other challenging space exploration missions. Prototype actuators have been built and tested in a unique low temperature test bed with motor interface temperatures as low as 14 degrees Kelvin. Several years of work have resulted in specialized electro-mechanical hardware to survive extreme space exploration environments, a test program that verifies and finds limitations of the designs at extreme temperatures, and a growing knowledge base that can be leveraged by future space exploration missions.

Windowpane flounder (Scophthalmus aquosus) and winter flounder (Pseudopleuronectes americanus) responses to cold temperature extremes in a Northwest Atlantic estuary

NASA Astrophysics Data System (ADS)

Wilber, Dara H.; Clarke, Douglas G.; Alcoba, Catherine M.; Gallo, Jenine

2016-01-01

The effect of climate variability on flatfish includes not only the effects of warming on sensitive life history stages, but also impacts from more frequent or unseasonal extreme cold temperatures. Cold weather events can affect the overwintering capabilities of flatfish near their low temperature range limits. We examined the responses of two flatfish species, the thin-bodied windowpane (Scophthalmus aquosus) and cold-tolerant winter flounder (Pseudopleuronectes americanus), to variable winter temperatures in a Northwest Atlantic estuary using abundance and size data collected during a monitoring study, the Aquatic Biological Survey, conducted from 2002 to 2010. Winter and spring abundances of small (50 to 120 mm total length) juvenile windowpane were positively correlated with adult densities (spawning stock) and fall temperatures (thermal conditions experienced during post-settlement development for the fall-spawned cohort) of the previous year. Windowpane abundances in the estuary were significantly reduced and the smallest size class was nearly absent after several consecutive years with cold (minimum temperatures < 1 °C) winters. Interannual variation in winter flounder abundances was unrelated to the severity of winter temperatures. A Paulik diagram illustrates strong positive correlations between annual abundances of sequential winter flounder life history stages (egg, larval, Age-1 juvenile, and adult male) within the estuary, reflecting residency within the estuary through their first year of life. Temperature variables representing conditions during winter flounder larval and post-settlement development were not significant factors in multiple regression models exploring factors that affect juvenile abundances. Likewise, densities of predators known to consume winter flounder eggs and/or post-settlement juveniles were not significantly related to interannual variation in winter flounder juvenile abundances. Colder estuarine temperatures through the first year of life were associated with smaller Age-1 winter flounder body size. For example, Age-1 winter flounder developing under conditions that differed by 1.9 °C in mean daily water temperature, averaged 98.7 mm total length (TL) and 123.1 mm TL, for the relatively cold vs. moderate years, respectively. More frequent cold temperature extremes associated with climate variability may negatively impact the overwintering capabilities of some flatfish near their cold temperature range limits, whereas cold-tolerant species may experience reduced growth, which imparts the ecological challenges associated with smaller body size.

Limited tolerance by insects to high temperatures across tropical elevational gradients and the implications of global warming for extinction.

PubMed

García-Robledo, Carlos; Kuprewicz, Erin K; Staines, Charles L; Erwin, Terry L; Kress, W John

2016-01-19

The critical thermal maximum (CTmax), the temperature at which motor control is lost in animals, has the potential to determine if species will tolerate global warming. For insects, tolerance to high temperatures decreases with latitude, suggesting that similar patterns may exist along elevational gradients as well. This study explored how CTmax varies among species and populations of a group of diverse tropical insect herbivores, the rolled-leaf beetles, across both broad and narrow elevational gradients. Data from 6,948 field observations and 8,700 museum specimens were used to map the elevational distributions of rolled-leaf beetles on two mountains in Costa Rica. CTmax was determined for 1,252 individual beetles representing all populations across the gradients. Initial morphological identifications suggested a total of 26 species with populations at different elevations displaying contrasting upper thermal limits. However, compared with morphological identifications, DNA barcodes (cytochrome oxidase I) revealed significant cryptic species diversity. DNA barcodes identified 42 species and haplotypes across 11 species complexes. These 42 species displayed much narrower elevational distributions and values of CTmax than the 26 morphologically defined species. In general, species found at middle elevations and on mountaintops are less tolerant to high temperatures than species restricted to lowland habitats. Species with broad elevational distributions display high CTmax throughout their ranges. We found no significant phylogenetic signal in CTmax, geography, or elevational range. The narrow variance in CTmax values for most rolled-leaf beetles, especially high-elevation species, suggests that the risk of extinction of insects may be substantial under some projected rates of global warming.

Limited tolerance by insects to high temperatures across tropical elevational gradients and the implications of global warming for extinction

PubMed Central

García-Robledo, Carlos; Kuprewicz, Erin K.; Staines, Charles L.; Erwin, Terry L.; Kress, W. John

2016-01-01

The critical thermal maximum (CTmax), the temperature at which motor control is lost in animals, has the potential to determine if species will tolerate global warming. For insects, tolerance to high temperatures decreases with latitude, suggesting that similar patterns may exist along elevational gradients as well. This study explored how CTmax varies among species and populations of a group of diverse tropical insect herbivores, the rolled-leaf beetles, across both broad and narrow elevational gradients. Data from 6,948 field observations and 8,700 museum specimens were used to map the elevational distributions of rolled-leaf beetles on two mountains in Costa Rica. CTmax was determined for 1,252 individual beetles representing all populations across the gradients. Initial morphological identifications suggested a total of 26 species with populations at different elevations displaying contrasting upper thermal limits. However, compared with morphological identifications, DNA barcodes (cytochrome oxidase I) revealed significant cryptic species diversity. DNA barcodes identified 42 species and haplotypes across 11 species complexes. These 42 species displayed much narrower elevational distributions and values of CTmax than the 26 morphologically defined species. In general, species found at middle elevations and on mountaintops are less tolerant to high temperatures than species restricted to lowland habitats. Species with broad elevational distributions display high CTmax throughout their ranges. We found no significant phylogenetic signal in CTmax, geography, or elevational range. The narrow variance in CTmax values for most rolled-leaf beetles, especially high-elevation species, suggests that the risk of extinction of insects may be substantial under some projected rates of global warming. PMID:26729867

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tracy, Patrick J.; Kasper, Justin C.; Zurbuchen, Thomas H.

Observations of velocity distribution functions from the Advanced Composition Explorer/Solar Wind Ion Composition Spectrometer heavy ion composition instrument are used to calculate ratios of kinetic temperature and Coulomb collisional interactions of an unprecedented 50 ion species in the solar wind. These ions cover a mass per charge range of 1–5.5 amu/e and were collected in the time range of 1998–2011. We report the first calculation of the Coulomb thermalization rate between each of the heavy ion (A > 4 amu) species present in the solar wind along with protons (H{sup +}) and alpha particles (He{sup 2+}). From these rates, wemore » find that protons are the dominant source of Coulomb collisional thermalization for heavy ions in the solar wind and use this fact to calculate a collisional age for those heavy ion populations. The heavy ion thermal properties are well organized by this collisional age, but we find that the temperature of all heavy ions does not simply approach that of protons as Coulomb collisions become more important. We show that He{sup 2+} and C{sup 6+} follow a monotonic decay toward equal temperatures with protons with increasing collisional age, but O{sup 6+} shows a noted deviation from this monotonic decay. Furthermore, we show that the deviation from monotonic decay for O{sup 6+} occurs in solar wind of all origins, as determined by its Fe/O ratio. The observed differences in heavy ion temperature behavior point toward a local heating mechanism that favors ions depending on their charge and mass.« less

Impact of weather factors on influenza hospitalization across different age groups in subtropical Hong Kong

NASA Astrophysics Data System (ADS)

Li, Yapeng; Wang, Xi-Ling; Zheng, Xueying

2018-05-01

Accumulating evidence demonstrates the significant influence of weather factors, especially temperature and humidity, on influenza seasonality. However, it is still unclear whether temperature variation within the same day, that is diurnal temperature range (DTR), is related to influenza seasonality. In addition, the different effects of weather factors on influenza seasonality across age groups have not been well documented in previous studies. Our study aims to explore the effects of DTR and humidity on influenza seasonality, and the differences in the association between weather factors and influenza seasonality among different age groups in Hong Kong, China. Generalized additive models were conducted to flexibly assess the impact of DTR, absolute humidity (vapor pressure, VP), and relative humidity on influenza seasonality in Hong Kong, China, from January 2012 to December 2016. Stratified analyses were performed to determine if the effects of weather factors differ across age groups (< 5, 5-9, 10-64, and > 64 years). The results suggested that DTR, absolute humidity, and relative humidity were significantly related to influenza seasonality in dry period (when VP is less than 20 mb), while no significant association was found in humid period (when VP is greater than 20 mb). The percentage changes of hospitalization rates due to influenza associated with per unit increase of weather factors in the very young children (age 0-4) and the elderly (age 65+) were higher than that in the adults (age 10-64). Diurnal temperature range is significantly associated with influenza seasonality in dry period, and the effects of weather factors differ across age groups in Hong Kong, China.

Thermoreversible Gels Composed of Colloidal Silica Rods with Short-Range Attractions

DOE PAGES

Murphy, Ryan P.; Hong, Kunlun; Wagner, Norman J.

2016-07-28

Dynamic arrest transitions of colloidal suspensions containing non-spherical particles are of interest for the design and processing of various particle technologies. To better understand the effects of particle shape anisotropy and attraction strength on gel and glass formation, we present a colloidal model system of octadecyl-coated silica rods, termed as adhesive hard rods (AHR), which enables control of rod aspect ratio and temperature-dependent interactions. The aspect ratios of silica rods were controlled by varying the initial TEOS concentration following the work of Kuijk et al. (J. Am. Chem. Soc., 2011, 133, 2346–2349) and temperature-dependent attractions were introduced by coating themore » calcined silica rods with an octadecyl-brush and suspending in tetradecane. The rod length and aspect ratio were found to increase with TEOS concentration as expected, while other properties such as the rod diameter, coating coverage, density, and surface roughness were nearly independent of the aspect ratio. Ultra-small angle X-ray scattering measurements revealed temperature-dependent attractions between octadecyl-coated silica rods in tetradecane, as characterized by a low-q upturn in the scattered intensity upon thermal quenching. Lastly, the rheology of a concentrated AHR suspension in tetradecane demonstrated thermoreversible gelation behavior, displaying a nearly 5 orders of magnitude change in the dynamic moduli as the temperature was cycled between 15 and 40 °C. We find the adhesive hard rod model system serves as a tunable platform to explore the combined influence of particle shape anisotropy and attraction strength on the dynamic arrest transitions in colloidal suspensions with thermoreversible, short-range attractions.« less

Hemolymph microbiome of Pacific oysters in response to temperature, temperature stress and infection

PubMed Central

Lokmer, Ana; Mathias Wegner, Karl

2015-01-01

Microbiota provide their hosts with a range of beneficial services, including defense from external pathogens. However, host-associated microbial communities themselves can act as a source of opportunistic pathogens depending on the environment. Marine poikilotherms and their microbiota are strongly influenced by temperature, but experimental studies exploring how temperature affects the interactions between both parties are rare. To assess the effects of temperature, temperature stress and infection on diversity, composition and dynamics of the hemolymph microbiota of Pacific oysters (Crassostrea gigas), we conducted an experiment in a fully-crossed, three-factorial design, in which the temperature acclimated oysters (8 or 22 °C) were exposed to temperature stress and to experimental challenge with a virulent Vibrio sp. strain. We monitored oyster survival and repeatedly collected hemolymph of dead and alive animals to determine the microbiome composition by 16s rRNA gene amplicon pyrosequencing. We found that the microbial dynamics and composition of communities in healthy animals (including infection survivors) were significantly affected by temperature and temperature stress, but not by infection. The response was mediated by changes in the incidence and abundance of operational taxonomic units (OTUs) and accompanied by little change at higher taxonomic levels, indicating dynamic stability of the hemolymph microbiome. Dead and moribund oysters, on the contrary, displayed signs of community structure disruption, characterized by very low diversity and proliferation of few OTUs. We can therefore link short-term responses of host-associated microbial communities to abiotic and biotic factors and assess the potential feedback between microbiota dynamics and host survival during disease. PMID:25180968

Thermal tolerance in bottlenose dolphins (Tursiops truncatus).

PubMed

Yeates, Laura C; Houser, Dorian S

2008-10-01

Water and air temperature are potentially limiting factors to the pole-ward distributions of coastal bottlenose dolphins. This study assessed the lower critical temperature of captive bottlenose dolphins to air temperature (LCT(a)) and water temperature (LCT(w)) through the use of open flow respirometry. Five dolphins, ranging from 14 to 33 years of age and acclimated to the waters of the southern California coast (14.2-22.5 degrees C), were subjected to water temperatures ranging from 0.2 to 18.0 degrees C. Two of the animals were additionally subjected to air temperatures ranging from -2.4 to 17.8 degrees C while maintaining water temperature approximately 3 degrees C above their individual LCT(w). The LCT(w) ranged from 5.5 to 10.6 degrees C and generally decreased with increasing animal mass; for dolphins in excess of 187 kg, the LCT(w) ranged from 5.5 to 5.7 degrees C. No LCT(a) could be determined across the range of air temperatures tested. Core body temperature remained within the limits of normal body temperatures reported for dolphins but demonstrated a direct relationship to water temperature in three subjects and varied across a range of 1.5 degrees C. Air and water temperature had a minimal synergistic effect on dolphin thermoregulation, i.e. water temperature exerted the predominant impact on thermoregulation. For dolphins in excess of 187 kg, water temperature alone would appear to be insufficient to limit the use of habitat north of current bottlenose dolphin ranges along the coastal United States. However, thermal impacts to smaller dolphins, in particular adolescents, neonates and accompanying females, may work in concert with other factors (e.g. prey distribution, predator avoidance, social interactions) to influence coastal residency patterns and population structure.

Thermal transport of carbon nanotubes and graphene under optical and electrical heating measured by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Hsu, I.-Kai

This thesis presents systematic studies of thermal transport in individual single walled carbon nanotubes (SWCNTs) and graphene by optical and electrical approaches using Raman spectroscopy. In the work presented from Chapter 2 to Chapter 6, individual suspended CNTs are preferentially measured in order to explore their intrinsic thermal properties. Moreover, the Raman thermometry is developed to detect the temperature of the carbon nanotube (CNT). A parabolic temperature profile is observed in the suspended region of the CNT while a heating laser scans across it, providing a direct evidence of diffusive thermal transport in an individual suspended CNT. Based on the curvature of the temperature profile, we can solve for the ratio of thermal contact resistance to the thermal resistance of the CNT, which spans the range from 0.02 to 17. The influence of thermal contact resistance on the thermal transport in an individual suspended CNT is also studied. The Raman thermometry is carried out in the center of a CNT, while its contact length is successively shortened by an atomic force microscope (AFM) tip cutting technique. By investigating the dependence of the CNT temperature on its thermal contact length, the temperature of a CNT is found to increase dramatically as the contact length is made shorter. This work reveals the importance of manipulating the CNT thermal contact length when adopting CNT as a thermal management material. In using a focused laser to induce heating in a suspended CNT, one open question that remains unanswered is how many of the incident photons are absorbed by the CNT of interest. To address this question, micro-fabricated platinum thermometers, together with micro-Raman spectroscopy are used to quantify the optical absorption of an individual CNT. The absorbed power in the CNT is equal to the power detected by two thermometers at the end of the CNT. Our result shows that the optical absorption lies in the range between 0.03 to 0.44%. In addition, the temperature gradient from the heating location to both ends of the suspended CNT, together with absorbed power and diameter of the CNT can be used to solve for the thermal conductivity of the CNT, which is found to span the range from 0.51nW/K to 2.28nW/K. We also conduct Raman measurements to explore the effect of gas molecules on thermal transport in electrically- or optically-heated suspended carbon nanotubes. Under the same electric heating power, the temperature increase of the CNT in gaseous environments is found to be considerably less than in vacuum, indicating non-negligible heat dissipation to the surrounding gas molecules. The result shows the approximately 50 to 60% of the heat is taken away by the surrounding gas molecules in a 5 microm long electrically-heated CNT. Following the electrical heating technique, a two-laser, purely optical measurement technique is utilized to observe heat dissipation in an ultra-long suspended CNT. Exponentially decaying temperature profiles with the heat decay lengths shorter than 7 microm are found in all samples measured. These relatively short heat decay lengths are attributed to the strong thermal coupling of carbon nanotubes' surface to air molecules. Moreover, the previously unmeasured heat transfer coefficient between CNT and air molecules is determined to be on the order of 104 W/m2·K.

Spatial and Temporal Variation in the Effects of Climatic Variables on Dugong Calf Production.

PubMed

Fuentes, Mariana M P B; Delean, Steven; Grayson, Jillian; Lavender, Sally; Logan, Murray; Marsh, Helene

2016-01-01

Knowledge of the relationships between environmental forcing and demographic parameters is important for predicting responses from climatic changes and to manage populations effectively. We explore the relationships between the proportion of sea cows (Dugong dugon) classified as calves and four climatic drivers (rainfall anomaly, Southern Oscillation El Niño Index [SOI], NINO 3.4 sea surface temperature index, and number of tropical cyclones) at a range of spatially distinct locations in Queensland, Australia, a region with relatively high dugong density. Dugong and calf data were obtained from standardized aerial surveys conducted along the study region. A range of lagged versions of each of the focal climatic drivers (1 to 4 years) were included in a global model containing the proportion of calves in each population crossed with each of the lagged versions of the climatic drivers to explore relationships. The relative influence of each predictor was estimated via Gibbs variable selection. The relationships between the proportion of dependent calves and the climatic drivers varied spatially and temporally, with climatic drivers influencing calf counts at sub-regional scales. Thus we recommend that the assessment of and management response to indirect climatic threats on dugongs should also occur at sub-regional scales.

Exploring new classification criteria for the earliest type stars: the 3400 Aregion

NASA Astrophysics Data System (ADS)

Morrell, Nidia I.; Walborn, Nolan R.; Arias, Julia I.

2002-02-01

We propose spectroscopic observations of a sample of standard O2-O4 stars in the wavelength region containing the N IV 3479-83-85 Aand O IV 3381-85-3412 Alines, in order to analyze the behavior of these spectral features as a function of the spectral type. We aim to define new classification criteria for the hottest stars, evaluating these N IV and O IV lines near 3400 Aas possible temperature and luminosity discriminators. The former spectral class O3 has just been split into three different classes: O2, O3 and O3.5 (Walborn et al. 2001). The paucity of classification criteria at these types in the traditional wavelength domain (4000 - 4700 Å), makes clear the need to explore other spectral ranges in order to define additional constraints on the determination of spectral types and luminosity classes. The wavelength range around 3400 Ahas been observed in many faint, crowded early O-type stars by HST/FOS, the corresponding data being available from the HST archive. This enhances our interest in observing this spectral range in the classification standards for the early O-type stars in order to make these existing HST observations even more useful, allowing the determination of accurate spectral types for unknown objects from them, once the behavior of the new criteria in the standards has been charted.

IAU Project and Research Activity in Nepal

NASA Astrophysics Data System (ADS)

Gautam, Suman

2015-08-01

The second half of the twentieth century has witnessed a tremendous development in the field of astronomy and space exploration. The large telescope both on the land and in the orbit, using the whole range of the electromagnetic spectra from radio waves to gamma rays are extending their range of exploration, right to the edge of the observable universe, and making astounding discoveries in the process. Many large international telescope facilities and global plans are accessible to all astronomers throughout the world, providing an inexpensive entry to cutting- edge international research for developing countries.Nepal is a mountainous country it has a wide range of climatic and altitude variations which varies from an elevation of 200 meter to ≥ 4000 meter. The average temperature varies from ≥ 25 o C to ≤ 0 to 5oC. Because of these diverse weather and climatic variation there is the potential for the establishment of sophisticated observatory/ data centre and link with each other. So, the future possible opportunity of astronomy in Nepal will be discussed. Besides Education and Research activities conducted in Tribhuvan University, Nepal under the support of International Astronomical Union (IAU) will also be highlighted. The importance brought by those two workshops conducted on data simulation supported by IAU under TF1 will also be discussed which is believed to play a vital role for the promotion and development of astronomy and astrophysics in developing countries.

The radiometric performances of the Planetary Fourier Spectrometer for Mars exploration

NASA Astrophysics Data System (ADS)

Palomba, E.; Colangeli, L.; Formisano, V.; Piccioni, G.; Cafaro, N.; Moroz, V.

1999-04-01

The Planetary Fourier Spectrometer (PFS) is a Fourier transform interferometer, operating in the range 1.2-45 μm. The instrument, previously included in the payload of the failed mission Mars ‧96, is proposed for the future space mission Mars Express, under study by ESA. The present paper is aimed at presenting the radiometric performances of PFS. The two channels (LW and SW) forming PFS were analysed and characterised in terms of sensitivity and noise equivalent brightness. To cover the wide spectral range of PFS, different blackbodies were used for calibration. The built-in blackbodies, needed for the in-flight calibrations, were also characterised. The results show that the LW channel is comparable with IRIS Mariner 9 in terms of noise equivalent brightness. The SW channel performances, while satisfactorily, could be improved by lowering the sensor operative temperature. A simple model of the Mars radiance is used in order to calculate the signal-to-noise ratio on the spectra in typical observation conditions. The computed signal-to-noise ratio for the LW channel varies between 430 and 40, while for the SW channel it ranges from 150 to 30. The radiometric analyses confirm that PFS performances are compliant with the design requirements of the instrument. PFS is fully validated for future remote exploration of the atmosphere and the surface of Mars.

Bedrock composition regulates mountain ecosystems and landscape evolution

PubMed Central

Hahm, W. Jesse; Riebe, Clifford S.; Lukens, Claire E.; Araki, Sayaka

2014-01-01

Earth’s land surface teems with life. Although the distribution of ecosystems is largely explained by temperature and precipitation, vegetation can vary markedly with little variation in climate. Here we explore the role of bedrock in governing the distribution of forest cover across the Sierra Nevada Batholith, California. Our sites span a narrow range of elevations and thus a narrow range in climate. However, land cover varies from Giant Sequoia (Sequoiadendron giganteum), the largest trees on Earth, to vegetation-free swaths that are visible from space. Meanwhile, underlying bedrock spans nearly the entire compositional range of granitic bedrock in the western North American cordillera. We explored connections between lithology and vegetation using measurements of bedrock geochemistry and forest productivity. Tree-canopy cover, a proxy for forest productivity, varies by more than an order of magnitude across our sites, changing abruptly at mapped contacts between plutons and correlating with bedrock concentrations of major and minor elements, including the plant-essential nutrient phosphorus. Nutrient-poor areas that lack vegetation and soil are eroding more than two times slower on average than surrounding, more nutrient-rich, soil-mantled bedrock. This suggests that bedrock geochemistry can influence landscape evolution through an intrinsic limitation on primary productivity. Our results are consistent with widespread bottom-up lithologic control on the distribution and diversity of vegetation in mountainous terrain. PMID:24516144

Balancing Hydronic Systems in Multifamily Buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruch, Russell; Ludwig, Peter; Maurer, Tessa

2014-07-01

In multifamily hydronic systems, temperature imbalance may be caused by undersized piping, improperly adjusted balancing valves, inefficient water temperature and flow levels, and owner/occupant interaction with the boilers, distribution, and controls. The imbalance leads to tenant discomfort, higher energy use intensity, and inefficient building operation. This research, conducted by Building America team Partnership for Advanced Residential Retrofit, explores cost-effective distribution upgrades and balancing measures in multifamily hydronic systems, providing a resource to contractors, auditors, and building owners on best practices to improve tenant comfort and lower operating costs. The team surveyed existing knowledge on cost-effective retrofits for optimizing distribution inmore » typical multifamily hydronic systems, with the aim of identifying common situations and solutions, and then conducted case studies on two Chicago area buildings with known balancing issues in order to quantify the extent of temperature imbalance. At one of these buildings a booster pump was installed on a loop to an underheated wing of the building. This study found that unit temperature in a multifamily hydronic building can vary as much as 61°F, particularly if windows are opened or tenants use intermittent supplemental heating sources like oven ranges. Average temperature spread at the building as a result of this retrofit decreased from 22.1°F to 15.5°F.« less

Peristaltic flow of Powell-Eyring fluid in curved channel with heat transfer: A useful application in biomedicine.

PubMed

Hina, S; Mustafa, M; Hayat, T; Alsaedi, A

2016-10-01

In this work, we explore the heat transfer characteristics in the peristaltic transport of Powell-Eyring fluid inside a curved channel with complaint walls. The study has motivation toward the understanding of blood flow in microcirculatory system. Formulation is developed in the existence of velocity slip and temperature jump conditions. Perturbation approach has been utilized to present series expressions of axial velocity and temperature distributions. Streamlines are prepared to analyze the interesting phenomenon of trapping. Moreover, the plots of heat transfer coefficient for a broad range of embedded parameters are presented and discussed. The results indicate that slip effects substantially influence the velocity and temperature distributions. Axial flow accelerates when slip parameter is incremented. Temperature rises and wall heat flux grows when viscous dissipation effect is strengthened. In contrast to the planar channels, here velocity and temperature functions do not exhibit symmetry with respect to the central line. In addition, bolus size and its shape are different in upper and lower portions of the channel. Heat transfer coefficient enlarges when the curvature effects are reduced. The behaviors of wall tension and wall mass parameters on the profiles are qualitatively similar. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Variation of mobile carbon reserves in trees at the alpine treeline ecotone is under environmental control.

PubMed

Fajardo, Alex; Piper, Frida I; Pfund, Laura; Körner, Christian; Hoch, Günter

2012-09-01

In low temperature-adapted plants, including treeline trees, light-saturated photosynthesis is considerably less sensitive to temperature than growth. As a consequence, all plants tested so far show increased nonstructural carbohydrate (NSC) tissue concentrations when exposed to low temperatures. Reduced carbon supply is thus an unlikely cause for low temperature range limits of plants. For altitudinal treeline trees there is, however, a possibility that high NSC genotypes have been selected. Here, we explored this possibility using afforestations with single-provenance conifers along elevational gradients in the Southern Chilean Andes and the Swiss Alps. Tree growth was measured at each of four approximately equidistant elevations at and below the treeline. Additionally, at the same elevations, needle, branch and stem sapwood tissues were collected to determine NSC concentrations. Overall, growth decreased and NSC concentrations increased with elevation. Along with previous empirical and experimental studies, the findings of this study provide no indication of NSC reduction at the treeline; NSC increased in most species (each represented by one common population) towards their upper climatic limit. The disparity between carbon acquisition and structural carbon investment at low temperature (accumulation of NSC) thus does occur even among genotypes not adapted to treeline environments. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Comparative thermometric properties of bi-functional Er3+-Yb3+ doped rare earth (RE = Y, Gd and La) molybdates

NASA Astrophysics Data System (ADS)

Sinha, Shriya; Mahata, Manoj Kumar; Kumar, Kaushal

2018-02-01

The molybdate compounds as luminescent medium have received great attention of recent research due to their excellent intrinsic optical properties. Therefore, the investigation on the optical thermometry and nanoheating effect in Er3+-Yb3+ doped molybdates of yttrium (EYYMO), gadolinium (EYGMO) and lanthanum (EYLMO) nanophosphors is reported herein. The temperature dependent fluorescence intensity ratio of green (525 and 548 nm) emission bands of Er3+ ions were analyzed within 300-500 K temperature range to determine the thermal behavior. The comparative temperature sensitivity of the materials has been found to depend on the phonon energy of their own. The thermal sensitivity is higher in the materials with low phonon energy. The intensity ratio of the green emission bands has been found to alter with the laser excitation density, which can be used to estimate the induced temperature in the materials. Furthermore, the photothermal conversion efficiency is calculated in the water dispersed samples and the maximum photothermal conversion efficiency of 49.6% is achieved for EYGMO nanophosphor. Comparative experimental results explore unequal thermal sensing and induced optical heating in the three rare earth molybdates. The optical properties of the green emitting molybdates are interesting for temperature sensing and optical heating applications.

Contributions of radiative factors to enhanced dryland warming over East Asia

NASA Astrophysics Data System (ADS)

Zhang, Yanting; Guan, Xiaodan; Yu, Haipeng; Xie, Yongkun; Jin, Hongchun

2017-08-01

Enhanced near-surface atmospheric warming has occurred over East Asia in recent decades, especially in drylands. Although local factors have been confirmed to provide considerable contributions to this warming, such factors have not been sufficiently analyzed. In this study, we extracted the radiatively forced temperature (RFT) associated with the built-up greenhouse gases, aerosol emission, and various other radiative forcing over East Asia and found a close relationship between RFT and CO2. In addition, using climate model experiments, we explored the responses of temperature changes to black carbon (BC), CO2, and SO4 and found that the enhanced dryland warming induced by CO2 had the largest magnitude and was strengthened by the warming effect of BC. Moreover, the sensitivity of daily maximum and minimum temperature changes to BC, CO2, and SO4 was examined. It showed asymmetric responses of daily maximum and minimum temperature to radiative factors, which led to an obvious change of diurnal temperature range (DTR), especially in drylands. The DTR's response to CO2 is the most significant. Therefore, CO2 not only plays a dominant role in enhanced warming but also greatly affects the decrease of DTR in drylands. However, the mechanisms of these radiative factors' effects in the process of DTR change are not clear and require more investigation.

Unravelling Diurnal Asymmetry of Surface Temperature in Different Climate Zones.

PubMed

Vinnarasi, R; Dhanya, C T; Chakravorty, Aniket; AghaKouchak, Amir

2017-08-04

Understanding the evolution of Diurnal Temperature Range (DTR), which has contradicting global and regional trends, is crucial because it influences environmental and human health. Here, we analyse the regional evolution of DTR trend over different climatic zones in India using a non-stationary approach known as the Multidimensional Ensemble Empirical Mode Decomposition (MEEMD) method, to explore the generalized influence of regional climate on DTR, if any. We report a 0.36 °C increase in overall mean of DTR till 1980, however, the rate has declined since then. Further, arid deserts and warm-temperate grasslands exhibit negative DTR trends, while the west coast and sub-tropical forest in the north-east show positive trends. This transition predominantly begins with a 0.5 °C increase from the west coast and spreads with an increase of 0.25 °C per decade. These changes are more pronounced during winter and post-monsoon, especially in the arid desert and warm-temperate grasslands, the DTR decreased up to 2 °C, where the rate of increase in minimum temperature is higher than the maximum temperature. We conclude that both maximum and minimum temperature increase in response to the global climate change, however, their rates of increase are highly local and depend on the underlying climatic zone.

Relating annual increments of the endangered Blanding's turtle plastron growth to climate

PubMed Central

Richard, Monik G; Laroque, Colin P; Herman, Thomas B

2014-01-01

This research is the first published study to report a relationship between climate variables and plastron growth increments of turtles, in this case the endangered Nova Scotia Blanding's turtle (Emydoidea blandingii). We used techniques and software common to the discipline of dendrochronology to successfully cross-date our growth increment data series, to detrend and average our series of 80 immature Blanding's turtles into one common chronology, and to seek correlations between the chronology and environmental temperature and precipitation variables. Our cross-dated chronology had a series intercorrelation of 0.441 (above 99% confidence interval), an average mean sensitivity of 0.293, and an average unfiltered autocorrelation of 0.377. Our master chronology represented increments from 1975 to 2007 (33 years), with index values ranging from a low of 0.688 in 2006 to a high of 1.303 in 1977. Univariate climate response function analysis on mean monthly air temperature and precipitation values revealed a positive correlation with the previous year's May temperature and current year's August temperature; a negative correlation with the previous year's October temperature; and no significant correlation with precipitation. These techniques for determining growth increment response to environmental variables should be applicable to other turtle species and merit further exploration. PMID:24963390

Relating annual increments of the endangered Blanding's turtle plastron growth to climate.

PubMed

Richard, Monik G; Laroque, Colin P; Herman, Thomas B

2014-05-01

This research is the first published study to report a relationship between climate variables and plastron growth increments of turtles, in this case the endangered Nova Scotia Blanding's turtle (Emydoidea blandingii). We used techniques and software common to the discipline of dendrochronology to successfully cross-date our growth increment data series, to detrend and average our series of 80 immature Blanding's turtles into one common chronology, and to seek correlations between the chronology and environmental temperature and precipitation variables. Our cross-dated chronology had a series intercorrelation of 0.441 (above 99% confidence interval), an average mean sensitivity of 0.293, and an average unfiltered autocorrelation of 0.377. Our master chronology represented increments from 1975 to 2007 (33 years), with index values ranging from a low of 0.688 in 2006 to a high of 1.303 in 1977. Univariate climate response function analysis on mean monthly air temperature and precipitation values revealed a positive correlation with the previous year's May temperature and current year's August temperature; a negative correlation with the previous year's October temperature; and no significant correlation with precipitation. These techniques for determining growth increment response to environmental variables should be applicable to other turtle species and merit further exploration.

Microstructural dependence on relevant physical-mechanical properties on SiO2-Na2O-CaO-P2O5 biological glasses.

PubMed

Rajendran, V; Begum, A Nishara; Azooz, M A; el Batal, F H

2002-11-01

Bioactive glasses of the system SiO2-Na2O-CaO-P2O5 have been prepared by the normal melting and annealing technique. The elastic moduli, attenuation, Vickers hardness, fracture toughness and fracture surface energy have been obtained using the known method at room temperature. The temperature dependence of elastic moduli and attenuation measurements have been extended over a wide range of temperature from 150 to 500 K. The SiO2 content dependence of velocities, attenuation, elastic moduli, and other parameters show an interesting observation at 45 wt% of SiO2 by exhibiting an anomalous behaviour. A linear relation is developed for Tg, which explores the influence of Na2O on SiO2-Na2O-CaO-P2O5 bioactive glasses. The measured hardness, fracture toughness and fracture surface energy show a linear relation with Young's modulus. It is also interesting to note that the observed results are functions of polymerisation and the number of non-bridging oxygens (NBO) prevailing in the network with change in SiO2 content. The temperature dependence of velocities, attenuation and elastic moduli show the existence of softening in the glass network structure as temperature increases.