Influence of heat transmission mode on heating rates and on the selection of patches for heating in a mediterranean lizard.

PubMed

Belliure, Josabel; Carrascal, Luis M

2002-01-01

Heliothermy (heat gain by radiation) has been given a prominent role in basking lizards. However, thigmothermy (heat gain by conduction) could be relevant for heating in small lizards. To ascertain the importance of the different heat transmission modes to the thermoregulatory processes, we conducted an experimental study where we analyzed the role of heat transmission modes on heating rates and on the selection of sites for heating in the Mediterranean lizard Acanthodactylus erythrurus (Lacertidae). The study was conducted under laboratory conditions, where two situations of different operative temperatures (38 degrees and 50 degrees C) were simulated in a terrarium. In a first experiment, individuals were allowed to heat up during 2 min at both temperatures and under both heat transmission modes. In a second experiment, individuals were allowed to select between patches differing in the main transmission mode, at both temperatures, to heat up. Experiences were conducted with live, nontethered lizards with a starting body temperature of 27 degrees C. Temperature had a significant effect on the heating rate, with heat gain per unit of time being faster at the higher operative temperature (50 degrees C). The effect of the mode of heat transmission on the heating rate was also significant: at 50 degrees C, heating rate was greater when the main heat transmission mode was conduction from the substrate (thigmothermy) than when heating was mainly due to heat gain by radiation (heliothermy); at 38 degrees C, heating rates did not significantly differ between transmission modes. At 38 degrees C, selection of the site for heating was not significantly different from that expected by chance. However, at 50 degrees C, the heating site offering the slowest heating rate (heliothermic patch) was selected. These results show that heating rates vary not only with environmental temperature but also with different predominant heat transmission modes. Lizards are able to identify and exploit this heterogeneity, selecting the source of heat gain (radiation) that minimizes the risk of overheating when temperature is high.

Performance and combustion characteristics of direct-injection stratified-charge rotary engines

NASA Technical Reports Server (NTRS)

Nguyen, Hung Lee

1987-01-01

Computer simulations of the direct-injection stratified-charge (DISC) Wankel engine have been used to calculate heat release rates and performance and efficiency characteristics of the 1007R engine. Engine pressure data have been used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine performance data are compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the Wankel engine with faster combustion, reduced leakage, higher compression ratio, and turbocharging is presented.

Analyzing Systems Integration Best Practices and Assessment in DoD Space Systems Acquisition

DTIC Science & Technology

2009-12-01

satellite  Insufficient stress relief and insulation caused abrasion of wiring harness. C Product–Product: stress relief and insulation – wiring...delaminated during firing . This problem escaped qualification since slow heating rates (0.1–deg F/sec) used in the lab test provided time for the gas...to escape. Faster rates would have revealed the issue. E Product–Process: material – replace, firing ; rate – test B Process–Process: replace

Prostaglandins are important in thermoregulation of a reptile (Pogona vitticeps).

PubMed Central

Seebacher, Frank; Franklin, Craig E

2003-01-01

The effectiveness of behavioural thermoregulation in reptiles is amplified by cardiovascular responses, particularly by differential rates of heart beat in response to heating and cooling (heart-rate hysteresis). Heart-rate hysteresis is ecologically important in most lineages of ectothermic reptile, and we demonstrate that heart-rate hysteresis in the lizard Pogona vitticeps is mediated by prostaglandins. In a control treatment (administration of saline), heart rates during heating were significantly faster than during cooling at any given body temperature. When cyclooxygenase 1 and 2 enzymes were inhibited, heart rates during heating were not significantly different from those during cooling. Administration of agonists showed that thromboxane B(2) did not have a significant effect on heart rate, but prostacyclin and prostaglandin F(2alpha) caused a significant increase (3.5 and 13.6 beats min(-1), respectively) in heart rate compared with control treatments. We speculate that heart-rate hysteresis evolved as a thermoregulatory mechanism that may ultimately be controlled by neurally induced stimulation of nitric oxide production, or maybe via photolytically induced production of vitamin D. PMID:12952634

Prostaglandins are important in thermoregulation of a reptile (Pogona vitticeps).

PubMed

Seebacher, Frank; Franklin, Craig E

2003-08-07

The effectiveness of behavioural thermoregulation in reptiles is amplified by cardiovascular responses, particularly by differential rates of heart beat in response to heating and cooling (heart-rate hysteresis). Heart-rate hysteresis is ecologically important in most lineages of ectothermic reptile, and we demonstrate that heart-rate hysteresis in the lizard Pogona vitticeps is mediated by prostaglandins. In a control treatment (administration of saline), heart rates during heating were significantly faster than during cooling at any given body temperature. When cyclooxygenase 1 and 2 enzymes were inhibited, heart rates during heating were not significantly different from those during cooling. Administration of agonists showed that thromboxane B(2) did not have a significant effect on heart rate, but prostacyclin and prostaglandin F(2alpha) caused a significant increase (3.5 and 13.6 beats min(-1), respectively) in heart rate compared with control treatments. We speculate that heart-rate hysteresis evolved as a thermoregulatory mechanism that may ultimately be controlled by neurally induced stimulation of nitric oxide production, or maybe via photolytically induced production of vitamin D.

Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution.

PubMed

Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A

2007-09-04

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

Time variability in Cenozoic reconstructions of mantle heat flow: Plate tectonic cycles and implications for Earth's thermal evolution

PubMed Central

Loyd, S. J.; Becker, T. W.; Conrad, C. P.; Lithgow-Bertelloni, C.; Corsetti, F. A.

2007-01-01

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by ∼0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past. PMID:17720806

Does the Chemothermal Instability Have Any Role in the Fragmentation of Primordial Gas

NASA Astrophysics Data System (ADS)

Dutta, Jayanta

2015-10-01

The collapse of the primordial gas in the density regime ˜108-1010 cm-3 is controlled by the three-body H2 formation process, in which the gas can cool faster than free-fall time—a condition proposed as the chemothermal instability. We investigate how the heating and cooling rates are affected during the rapid transformation of atomic to molecular hydrogen. With a detailed study of the heating and cooling balance in a 3D simulation of Pop III collapse, we follow the chemical and thermal evolution of the primordial gas in two dark matter minihalos. The inclusion of sink particles in modified Gadget-2 smoothed particle hydrodynamics code allows us to investigate the long-term evolution of the disk that fragments into several clumps. We find that the sum of all the cooling rates is less than the total heating rate after including the contribution from the compressional heating (pdV). The increasing cooling rate during the rapid increase of the molecular fraction is offset by the unavoidable heating due to gas contraction. We conclude that fragmentation occurs because H2 cooling, the heating due to H2 formation and compressional heating together set a density and temperature structure in the disk that favors fragmentation, not the chemothermal instability.

Structural, morphological and optical studies of ripple-structured ZnO thin films

NASA Astrophysics Data System (ADS)

Navin, Kumar; Kurchania, Rajnish

2015-11-01

Ripple-structured ZnO thin films were prepared on Si (100) substrate by sol-gel spin-coating method with different heating rates during preheating process and finally sintered at 500 °C for 2 h in ambient condition. The structural, morphological and photoluminescence (PL) properties of the nanostructured films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and PL spectroscopy. XRD analysis revealed that films have hexagonal wurtzite structure and texture coefficient increases along (002) plane with preheating rate. The faster heating rate produced higher crystallization and larger average crystallite size. The AFM and SEM images indicate that all the films have uniformly distributed ripple structure with skeletal branches. The number of ripples increases, while the rms roughness, amplitude and correlation length of the ripple structure decrease with preheating rates. The PL spectra show the presence of different defects in the structure. The ultraviolet emission improved with the heating rate which indicates its better crystallinity.

Changes in heart rate variability during the induction and decay of heat acclimation.

PubMed

Flouris, Andreas D; Poirier, Martin P; Bravi, Andrea; Wright-Beatty, Heather E; Herry, Christophe; Seely, Andrew J; Kenny, Glen P

2014-10-01

We evaluated the changes in core temperature, heart rate, and heart rate variability (HRV) during the induction and decay of heat acclimation. Ten males (23 ± 3 years; 79.5 ± 3.5 kg; 15.2 ± 4.5 percent body fat; 51.13 ± 4.61 mLO(2)∙kg(-1)∙min(-1) peak oxygen uptake) underwent a 14-day heat acclimation protocol comprising of 90-min cycling at ~50 % peak oxygen uptake at 40 °C and ~20 % relative humidity. Core temperature, heart rate, and 102 HRV measures were recorded during a heat tolerance test conducted at baseline (day 0) and at the end of the induction (day 14) and decay (day 28) phases. Heat acclimation resulted in significantly reduced core temperature [rectal (χ (2) = 1298.14, p < 0.001); esophageal (χ (2) = 1069.88, p < 0.001)] and heart rate (χ (2) = 1230.17, p < 0.001). Following the decay phase, 26, 40, and 60 % of the heat acclimation-induced reductions in rectal temperature, esophageal temperature, and heart rate, respectively, were lost. Heat acclimation was accompanied by profound and broad changes in HRV: at the end of the induction phase, 75 of the 102 variability measures computed were significantly different (p < 0.001), compared to only 47 of the 102 at the end of the decay phase. Heat acclimation is accompanied by reduced core temperature, significant bradycardia, and marked alterations in HRV, which we interpret as being related to vagal dominance. The observed changes in core temperature persist for at least 2 weeks of non-exposure to heat, while the changes in heart rate and HRV decay faster and are only partly evident after 2 weeks of non-exposure to heat.

The effect of heat transfer mode on heart rate responses and hysteresis during heating and cooling in the estuarine crocodile Crocodylus porosus.

PubMed

Franklin, Craig E; Seebacher, Frank

2003-04-01

The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions; (2) heated via radiant energy while half-submerged in flowing water at 23 degrees C and (3) heated via convective transfer by increasing water temperature from 23 degrees C to 35 degrees C. Cooling was achieved in all treatments by removing the heat source and with C. porosus half-submerged in flowing water at 23 degrees C. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate ('rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature (<0.5 degrees C) resulted in Q(10) values greater than 4000, calling into question the usefulness of this measure on heart rate during the initial stages of heating and cooling. In the later phases of heating and cooling, heart rate changed with body temperature, with Q(10) values of 2-3. The magnitude of the heart rate response differed between treatments, with radiant heating during submergence eliciting the smallest response. The heart rate of C. porosus outside of the 'rapid response' periods was found to be a function of the heat load experienced at the animal surface, as well as on the mode of heat transfer. Heart rate increased or decreased rapidly when C. porosus experienced large positive (above 25 W) or negative (below -15 W) heat loads, respectively, in all treatments. For heat loads between -15 W and 20 W, the increase in heart rate was smaller for the 'unnatural' heating by convection in water compared with either treatment using radiant heating. Our data indicate that changes in heart rate constitute a thermoregulatory mechanism that is modulated in response to the thermal environment occupied by the animal, but that heart rate during heating and cooling is, in part, controlled independently of body temperature.

Effects of Cloud-Microphysics on Tropical Atmospheric Hydrologic Processes in the GEOS GCM

NASA Technical Reports Server (NTRS)

Lau, K. M.; Wu, H. T.; Sud, Y. C.; Walker, G. K.

2004-01-01

The sensitivity of tropical atmospheric hydrologic processes to cloud-microphysics is investigated using the NASA GEOS GCM. Results show that a faster autoconversion - rate produces more warm rain and less clouds at all levels. Fewer clouds enhances longwave cooling and reduces shortwave heating in the upper troposphere, while more warm rain produces increased condensation heating in the lower troposphere. This vertical heating differential destablizes the tropical atmosphere, producing a positive feedback resulting in more rain over the tropics. The feedback is maintained via a two-cell secondary circulation. The lower cell is capped by horizontal divergence and maximum cloud detrainment near the melting/freezing, with rising motion in the warm rain region connected to descending motion in the cold rain region. The upper cell is found above the freezing/melting level, with longwave-induced subsidence in the warm rain and dry regions, coupled to forced ascent in the deep convection region. The tropical large scale circulation is found to be very sensitive to the radiative-dynamic effects induced by changes in autoconversion rate. Reduced cloud-radiation processes feedback due to a faster autoconversion rate results in intermittent but more energetic eastward propagating Madden and Julian Oscillations (MJO). Conversely,-a slower autconversion rate, with increased cloud radiation produces MJO's with more realistic westward propagating transients, resembling a supercloud cluster structure. Results suggests that warm rain and associated low and mid level clouds, i.e., cumulus congestus, may play a critical role in regulating the time-intervals of deep convections and hence the fundamental time scales of the MJO.

Regional blood flow in sea turtles: implications for heat exchange in an aquatic ectotherm.

PubMed

Hochscheid, Sandra; Bentivegna, Flegra; Speakman, John R

2002-01-01

Despite substantial knowledge on thermoregulation in reptiles, the mechanisms involved in heat exchange of sea turtles have not been investigated in detail. We studied blood flow in the front flippers of two green turtles, Chelonia mydas, and four loggerhead turtles, Caretta caretta, using Doppler ultrasound to assess the importance of regional blood flow in temperature regulation. Mean blood flow velocity and heart rate were determined for the water temperature at which the turtles were acclimated (19.3 degrees-22.5 degrees C) and for several experimental water temperatures (17 degrees-32 degrees C) to which the turtles were exposed for a short time. Flipper circulation increased with increasing water temperature, whereas during cooling, flipper circulation was greatly reduced. Heart rate was also positively correlated with water temperature; however, there were large variations between individual heart rate responses. Body temperatures, which were additionally determined for the two green turtles and six loggerhead turtles, increased faster during heating than during cooling. Heating rates were positively correlated with the difference between acclimation and experimental temperature and negatively correlated with body mass. Our data suggest that by varying circulation of the front flippers, turtles are capable of either transporting heat quickly into the body or retaining heat inside the body, depending on the prevailing thermal demands.

The effects of moderately high temperature on zeaxanthin accumulation and decay.

PubMed

Zhang, Ru; Kramer, David M; Cruz, Jeffrey A; Struck, Kimberly R; Sharkey, Thomas D

2011-09-01

Moderately high temperature reduces photosynthetic capacities of leaves with large effects on thylakoid reactions of photosynthesis, including xanthophyll conversion in the lipid phase of the thylakoid membrane. In previous studies, we have found that leaf temperature of 40°C increased zeaxanthin accumulation in dark-adapted, intact tobacco leaves following a brief illumination, but did not change the amount of zeaxanthin in light-adatped leaves. To investigate heat effects on zeaxanthin accumulation and decay, zeaxanthin level was monitored optically in dark-adapted, intact tobacco and Arabidopsis thaliana leaves at either 23 or 40°C under 45-min illumination. Heated leaves had more zeaxanthin following 3-min light but had less or comparable amounts of zeaxanthin by the end of 45 min of illumination. Zeaxanthin accumulated faster at light initiation and decayed faster upon darkening in leaves at 40°C than leaves at 23°C, indicating that heat increased the activities of both violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZE). In addition, our optical measurement demonstrated in vivo that weak light enhances zeaxanthin decay relative to darkness in intact leaves of tobacco and Arabidopsis, confirming previous observations in isolated spinach chloroplasts. However, the maximum rate of decay is similar for weak light and darkness, and we used the maximum rate of decay following darkness as a measure of the rate of ZE during steady-state light. A simulation indicated that high temperature should cause a large shift in the pH dependence of the amount of zeaxanthin in leaves because of differential effects on VDE and ZE. This allows for the reduction in ΔpH caused by heat to be offset by increased VDE activity relative to ZE.

Accelerated lamellar disintegration in eutectoid steel

NASA Astrophysics Data System (ADS)

Mishra, Shakti; Mishra, Alok; Show, Bijay Kumar; Maity, Joydeep

2017-04-01

The fastest kinetics of lamellar disintegration (predicted duration of 44 min) in AISI 1080 steel is obtained with a novel approach of incomplete austenitisation-based cyclic heat treatment involving forced air cooling with an air flow rate of 8.7 m3 h-1. A physical model for process kinetics is proposed that involves lamellar fragmentation, lamellar thickening, divorced eutectoid growth and generation of new lamellar faults in remaining cementite lamellae in each cycle. Lamellar fragmentation is accentuated with faster rate of cooling through generation of more intense lamellar faults; but divorced eutectoid growth is ceased. Accordingly, as compared to still air cooling, much faster kinetics of lamellar disintegration is obtained by forced air cooling together with the generation of much smaller submicroscopic cementite particles (containing more proportion of plate-shaped non-spheroids) in divorced eutectoid region.

Rapid charging of thermal energy storage materials through plasmonic heating.

PubMed

Wang, Zhongyong; Tao, Peng; Liu, Yang; Xu, Hao; Ye, Qinxian; Hu, Hang; Song, Chengyi; Chen, Zhaoping; Shang, Wen; Deng, Tao

2014-09-01

Direct collection, conversion and storage of solar radiation as thermal energy are crucial to the efficient utilization of renewable solar energy and the reduction of global carbon footprint. This work reports a facile approach for rapid and efficient charging of thermal energy storage materials by the instant and intense photothermal effect of uniformly distributed plasmonic nanoparticles. Upon illumination with both green laser light and sunlight, the prepared plasmonic nanocomposites with volumetric ppm level of filler concentration demonstrated a faster heating rate, a higher heating temperature and a larger heating area than the conventional thermal diffusion based approach. With controlled dispersion, we further demonstrated that the light-to-heat conversion and thermal storage properties of the plasmonic nanocomposites can be fine-tuned by engineering the composition of the nanocomposites.

Rapid Charging of Thermal Energy Storage Materials through Plasmonic Heating

PubMed Central

Wang, Zhongyong; Tao, Peng; Liu, Yang; Xu, Hao; Ye, Qinxian; Hu, Hang; Song, Chengyi; Chen, Zhaoping; Shang, Wen; Deng, Tao

2014-01-01

Direct collection, conversion and storage of solar radiation as thermal energy are crucial to the efficient utilization of renewable solar energy and the reduction of global carbon footprint. This work reports a facile approach for rapid and efficient charging of thermal energy storage materials by the instant and intense photothermal effect of uniformly distributed plasmonic nanoparticles. Upon illumination with both green laser light and sunlight, the prepared plasmonic nanocomposites with volumetric ppm level of filler concentration demonstrated a faster heating rate, a higher heating temperature and a larger heating area than the conventional thermal diffusion based approach. With controlled dispersion, we further demonstrated that the light-to-heat conversion and thermal storage properties of the plasmonic nanocomposites can be fine-tuned by engineering the composition of the nanocomposites. PMID:25175717

White LED performance

NASA Astrophysics Data System (ADS)

Gu, Yimin; Narendran, Nadarajah; Freyssinier, Jean Paul

2004-10-01

Two life tests were conducted to compare the effects of drive current and ambient temperature on the degradation rate of 5 mm and high-flux white LEDs. Tests of 5 mm white LED arrays showed that junction temperature increases produced by drive current had a greater effect on the rate of light output degradation than junction temperature increases from ambient heat. A preliminary test of high-flux white LEDs showed the opposite effect, with junction temperature increases from ambient heat leading to a faster depreciation. However, a second life test is necessary to verify this finding. The dissimilarity in temperature effect among 5 mm and high-flux LEDs is likely caused by packaging differences between the two device types.

Incubation behavior of silicon nanowire growth investigated by laser-assisted rapid heating

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

Ryu, Sang-gil; Kim, Eunpa; Grigoropoulos, Costas P., E-mail: cgrigoro@berkeley.edu

2016-08-15

We investigate the early stage of silicon nanowire growth by the vapor-liquid-solid mechanism using laser-localized heating combined with ex-situ chemical mapping analysis by energy-filtered transmission electron microscopy. By achieving fast heating and cooling times, we can precisely determine the nucleation times for nanowire growth. We find that the silicon nanowire nucleation process occurs on a time scale of ∼10 ms, i.e., orders of magnitude faster than the times reported in investigations using furnace processes. The rate-limiting step for silicon nanowire growth at temperatures in the vicinity of the eutectic temperature is found to be the gas reaction and/or the silicon crystalmore » growth process, whereas at higher temperatures it is the rate of silicon diffusion through the molten catalyst that dictates the nucleation kinetics.« less

NASA/ORNL/AFRL Project Work on EBM LSHR: Additive Manufacturing of High-Temperature Gamma-Prime Strengthened Ni-Based Superalloys

NASA Technical Reports Server (NTRS)

Sudbrack, Chantal K.; Kirka, Michael M.; Dehoff, Ryan R.; Carter, Robert W.; Semiatin, Sheldon L.; Gabb, Timothy P.

2016-01-01

Powder-bed fabrication of aerospace alloys may revolutionize production by eliminating the need for extensive machining and expensive tooling. Heated-bed electron-beam melting (EBM) offers advantages over non-heated laser additive manufacturing (AM) methods, including lower residual stress, reduced risk of contamination, slower cooling rates, and faster build times. NASA Glenn Research Center has joint project work with Oak Ridge National Lab and the Air Force Research Laboratory to explore the feasibility of fabricating advanced Ni-based gamma-prime superalloys with EBM AM.

Ultrafast electronic relaxation in superheated bismuth

NASA Astrophysics Data System (ADS)

Gamaly, E. G.; Rode, A. V.

2013-01-01

Interaction of moving electrons with vibrating ions in the lattice forms the basis for many physical properties from electrical resistivity and electronic heat capacity to superconductivity. In ultrafast laser interaction with matter the electrons are heated much faster than the electron-ion energy equilibration, leading to a two-temperature state with electron temperature far above that of the lattice. The rate of temperature equilibration is governed by the strength of electron-phonon energy coupling, which is conventionally described by a coupling constant, neglecting the dependence on the electron and lattice temperature. The application of this constant to the observations of fast relaxation rate led to a controversial notion of ‘ultra-fast non-thermal melting’ under extreme electronic excitation. Here we provide theoretical grounds for a strong dependence of the electron-phonon relaxation time on the lattice temperature. We show, by taking proper account of temperature dependence, that the heating and restructuring of the lattice occurs much faster than were predicted on the assumption of a constant, temperature independent energy coupling. We applied the temperature-dependent momentum and energy transfer time to experiments on fs-laser excited bismuth to demonstrate that all the observed ultra-fast transformations of the transient state of bismuth are purely thermal in nature. The developed theory, when applied to ultrafast experiments on bismuth, provides interpretation of the whole variety of transient phase relaxation without the non-thermal melting conjecture.

Flow-dependent vascular heat transfer during microwave thermal ablation.

PubMed

Chiang, Jason; Hynes, Kieran; Brace, Christopher L

2012-01-01

Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

Growth medium sterilization using decomposition of peracetic acid for more cost-efficient production of omega-3 fatty acids by Aurantiochytrium.

PubMed

Cho, Chang-Ho; Shin, Won-Sub; Woo, Do-Wook; Kwon, Jong-Hee

2018-06-01

Aurantiochytrium can produce significant amounts of omega-3 fatty acids, specifically docosahexaenoic acid and docosapentaenoic acid. Use of a glucose-based medium for heterotrophic growth is needed to achieve a high growth rate and production of abundant lipids. However, heat sterilization for reliable cultivation is not appropriate to heat-sensitive materials and causes a conversion of glucose via browning (Maillard) reactions. Thus, the present study investigated the use of a direct degradation of Peracetic acid (PAA) for omega-3 production by Aurantiochytrium. Polymer-based bioreactor and glucose-containing media were chemically co-sterilized by 0.04% PAA and neutralized through a reaction with ferric ion (III) in HEPES buffer. Mono-cultivation was achieved without the need for washing steps and filtration, thereby avoiding the heat-induced degradation and dehydration of glucose. Use of chemically sterilized and neutralized medium, rather than heat-sterilized medium, led to a twofold faster growth rate and greater productivity of omega-3 fatty acids.

Curing system for high voltage cross linked cables

DOEpatents

Bahder, George; Katz, Carlos; Bopp, Louis A.

1978-01-01

This invention makes extruded, vulcanized, high voltage cables insulated with thermosetting compounds at much higher rates of production and with superior insulation of reduced thickness and with reduced cavities or voids in the insulation. As the cable comes from an extruder, it passes into a curing chamber with a heat booster that quickly raises the insulation to a temperature at which it is cured much more quickly than with steam heating of the prior art. A high temperature liquid in contact with the insulation maintains the high temperature; and because of the greater curing heat, the cable can travel through the curing chamber at a faster rate and into a cooling tube where it contacts with a cooling liquid under high pressure. The insulation compound is treated to reduce the size of cavities; and the high pressure maintained by the curing and cooling mediums prevent expansion of cavities before the insulation is set.

The induction and decay of heat acclimatisation in trained athletes.

PubMed

Armstrong, L E; Maresh, C M

1991-11-01

Heat acclimatisation/acclimation involves a complex of adaptations which includes decreased heart rate, rectal temperature, perceived exertion as well as increased plasma volume and sweat rate. These adaptations serve to reduce physiological strain, improve an athlete's ability to exercise in a hot environment, and reduce the incidence of some forms of heat illness. Few differences exist in the ability of men and women to acclimatise to heat. Typically, older runners do not perform in the heat as well as younger runners, but physical training can negate differences between these groups. Hormonal adaptations (e.g. aldosterone, vasopressin) during heat acclimatisation encourage fluid-electrolyte retention and cardiovascular stability. Athletes with high maximal aerobic power (VO2max) acclimatise to heat faster (and lose adaptations slower when they are inactive in a cool environment) than athletes with low VO2max values. Physical training in a cool environment improves physiological responses to exercise at high ambient temperatures. In attempting to optimise heat acclimatisation, athletes should maintain fluid-electrolyte balance, exercise at intensities greater than 50% VO2max for 10 to 14 days, and avoid factors (e.g. sleep loss, infectious disease) which are known to reduce heat tolerance. Once acclimatisation has been achieved, inactivity results in a decay of favourable adaptations, after only a few days or weeks.

Investigations on the heat transport capability of a cryogenic oscillating heat pipe and its application in achieving ultra-fast cooling rates for cell vitrification cryopreservation☆

PubMed Central

Han, Xu; Ma, Hongbin; Jiao, Anjun; Critser, John K.

2010-01-01

Theoretically, direct vitrification of cell suspensions with relatively low concentrations (~1 M) of permeating cryoprotective agents (CPA) is suitable for cryopreservation of almost all cell types and can be accomplished by ultra-fast cooling rates that are on the order of 106–7 K/min. However, the methods and devices currently available for cell cryopreservation cannot achieve such high cooling rates. In this study, we constructed a novel cryogenic oscillating heat pipe (COHP) using liquid nitrogen as its working fluid and investigated its heat transport capability to assess its application for achieving ultra-fast cooling rates for cell cryopreservation. The experimental results showed that the apparent heat transfer coefficient of the COHP can reach 2 × 105 W/m2·K, which is two orders of the magnitude higher than traditional heat pipes. Theoretical analyzes showed that the average local heat transfer coefficient in the thin film evaporation region of the COHP can reach 1.2 × 106 W/m2·K, which is approximately 103 times higher than that achievable with standard pool-boiling approaches. Based on these results, a novel device design applying the COHP and microfabrication techniques is proposed and its efficiency for cell vitrification is demonstrated through numerical simulation. The estimated average cooling rates achieved through this approach is 106–7 K/min, which is much faster than the currently available methods and sufficient for achieving vitrification with relatively low concentrations of CPA. PMID:18430413

Investigations on the heat transport capability of a cryogenic oscillating heat pipe and its application in achieving ultra-fast cooling rates for cell vitrification cryopreservation.

PubMed

Han, Xu; Ma, Hongbin; Jiao, Anjun; Critser, John K

2008-06-01

Theoretically, direct vitrification of cell suspensions with relatively low concentrations ( approximately 1 M) of permeating cryoprotective agents (CPA) is suitable for cryopreservation of almost all cell types and can be accomplished by ultra-fast cooling rates that are on the order of 10(6-7) K/min. However, the methods and devices currently available for cell cryopreservation cannot achieve such high cooling rates. In this study, we constructed a novel cryogenic oscillating heat pipe (COHP) using liquid nitrogen as its working fluid and investigated its heat transport capability to assess its application for achieving ultra-fast cooling rates for cell cryopreservation. The experimental results showed that the apparent heat transfer coefficient of the COHP can reach 2 x 10(5) W/m(2).K, which is two orders of the magnitude higher than traditional heat pipes. Theoretical analyzes showed that the average local heat transfer coefficient in the thin film evaporation region of the COHP can reach 1.2 x 10(6) W/m(2).K, which is approximately 10(3) times higher than that achievable with standard pool-boiling approaches. Based on these results, a novel device design applying the COHP and microfabrication techniques is proposed and its efficiency for cell vitrification is demonstrated through numerical simulation. The estimated average cooling rates achieved through this approach is 10(6-7)K/min, which is much faster than the currently available methods and sufficient for achieving vitrification with relatively low concentrations of CPA.

Redistribution of blood within the body is important for thermoregulation in an ectothermic vertebrate (Crocodylus porosus).

PubMed

Seebacher, Frank; Franklin, Craig E

2007-11-01

Changes in blood flow are a principal mechanism of thermoregulation in vertebrates. Changes in heart rate will alter blood flow, although multiple demands for limited cardiac output may compromise effective thermoregulation. We tested the hypothesis that regional differences in blood flow during heating and cooling can occur independently from changes in heart rate. We measured heart rate and blood pressure concurrently with blood flow in the crocodile, Crocodylus porosus. We measured changes in blood flow by laser Doppler flowmetry, and by injecting coloured microspheres. All measurements were made under different heat loads, with and without blocking cholinergic and beta-adrenergic receptors (autonomic blockade). Heart rates were significantly faster during heating than cooling in the control animals, but not when autonomic receptors were blocked. There were no significant differences in blood flow distribution between the control and autonomic blockade treatments. In both treatments, blood flow was directed to the dorsal skin and muscle and away from the tail and duodenum during heating. When the heat source was switched off, there was a redistribution of blood from the dorsal surface to the duodenum. Blood flow to the leg skin and muscle, and to the liver did not change significantly with thermal state. Blood pressure was significantly higher during the autonomic blockade than during the control. Thermal time constants of heating and cooling were unaffected by the blockade of autonomic receptors. We concluded that animals partially compensated for a lack of differential heart rates during heating and cooling by redistributing blood within the body, and by increasing blood pressure to increase flow. Hence, measures of heart rate alone are insufficient to assess physiological thermoregulation in reptiles.

The role of heat transfer in strip casting

NASA Astrophysics Data System (ADS)

Misra, Paretosh

The last few years have witnessed rapid developments in the area of strip casting of steel. It involves smaller capital and operating cost, lower greenhouse gas emissions, and an opportunity to create newer products due to a faster solidification rate that leads to a different solidification structure. Thus, ample reasons for interest in the technology exist. At the same time, it needs to be determined if the properties of a strip cast product can match those of a conventional product and if it is possible to produce steel strip at high production rates. The first objective of this work was to characterize the quality, structure, and properties of strip cast material of different chemistries and cast at different machines, to identify the critical operating conditions that would result in the best properties. Determination of the possible range of properties was also aimed, given that the structure of the material is different from the traditional material. The second objective was to investigate ways to increase the rate of heat transfer in strip casting, as that will also enhance the productivity of a strip caster. It was also envisaged to see what effect a high rate of heat transfer will have on the properties of the strip cast material. Results from the strip cast material characterization that was carried out to achieve the first objective indicated that an effective control of heat transfer is very important to get the best properties. Samples that showed best properties had a uniform solidification structure consisting of columnar grains running from the edge of a strip to the centerline, indicating a good control of heat transfer, and their dendrite spacings pointed towards a relatively faster rate of cooling between the rolls. These findings indicated that heat transfer is a core issue in strip casting. The mechanism of increase in the rate of heat transfer in strip casting due to the presence of liquid oxide films at the metal-mold interface was examined. It was discovered that these films originate from the metal itself. A high degree of interdendritic supersaturation can lead to the formation of low melting point oxide phases by the deoxidizing agents in the steel. As the temperature lowers further the film may get ejected out of the metal due to the non-wetting of the metal by the oxide phase. If enough oxide film can be generated then this can result in an almost two-fold increase in the rate of heat transfer during initial solidification---the first 20 milliseconds. The results indicate that if a proper control of these films is ensured then it provides an attractive alternative to increasing the roll diameter as a mechanism of increasing the rate of production of a strip caster. This mechanism will work even with smaller diameter rolls, in fact, perhaps better in that case due to a smaller interface area over which uniformity of heat transfer has to be ensured, thus leveraging its full advantages. If successfully implemented at a plant, this technique can help the strip casting machines to increase their productivity and emerge as a competitive technology to produce steel strip.

Coarsening Kinetics and Morphological Evolution in a Two-Phase Titanium Alloy During Heat Treatment

NASA Astrophysics Data System (ADS)

Xu, Jianwei; Zeng, Weidong; Jia, Zhiqiang; Sun, Xin; Zhao, Yawei

2016-03-01

The effects of alpha/beta heat treatment on microstructure evolution of Ti-17 alloy with a lamellar colony structure are established. Heat treatment experiments are conducted at 1103 or 1063 K for times ranging from 10 min to 8 h. The main features of microstructure evolution during heat treatment comprise static globularization and coarsening of primary alpha phase. Such behaviors can be accelerated by higher heat treatment temperature. Furthermore, globularization and coarsening behaviors show a faster rate at higher prestrain. In order to better understand the microstructure evolution of Ti-17 alloy during alpha/beta heat treatment, static globularization and coarsening behaviors are modeled in the theoretical frame of the Johnson-Mehl-Avarmi-Kolmogorov (JMAK) and Lifshitz-Slyozov-Wagner (LSW) theories, respectively. The JMAK and LSW kinetics parameters are derived under different experimental conditions. Agreements between measurements and predictions are found, indicating that the JMAK and LSW theories can be used to predict and trace static globularization and coarsening processes of Ti-17 alloy during alpha/beta heat treatment.

[Effects of cropping patterns on photosynthesis characteristics of summer maize and its utilization of solar and heat resources].

PubMed

Zhu, Yuan-Gang; Dong, Shu-Ting; Zhang, Ji-Wang; Liu, Peng; Yang, Jin-Sheng; Jia, Chun-Lan; Liu, Jing-Guo; Li, Deng-Hai

2010-06-01

In order to investigate the effects of interplanting and direct seeding on the photosynthesis characteristics of summer maize and its utilization of solar and heat resources, two summer maize cultivars (Zhengdan 958 and Denghai 661) were planted in the farmlands of Denghai Seed Co. Ltd in Laizhou City of Shandong Province, with 67500 plants x hm(-2) and three sowing dates. The above-ground biomass, plant growth rate, leaf area index, and net photosynthetic rate per ear leaf were measured to reveal the photosynthesis characteristics of test cultivars. In the meantime, the characters of grain-filling were simulated by Richards' model, and the solar resource utilization efficiency of the cultivars was calculated, in combining with meteorological data. Comparing with interplanting, direct seeding increased the grain yield by 1.17%-3.33%, but decreased the thousand-grain weight significantly. Growth stages were extended under earlier sowing. The leaf area index and net photosynthetic rate from flowering to 30 d after anthesis were significantly higher under direct seeding than under interplanting, but after then, they decreased faster. Direct seeding induced a higher accumulation of dry matter and a faster plant growth rate before and after flowering. Under direct seeding, the maximum grain-filling rate reached earlier, the starting potential was higher, but the grain-filling period, active grain-filling period, and W(max) were lower, compared with those under interplanting. Also under direct seeding, the total accumulative temperature and solar radiation during growth period decreased by 150-350 degrees C x d and 200-400 MJ x m(-2), respectively, but the solar resource utilization efficiency of grain increased by 10.5%-24.7%. All the results suggested that direct seeding was superior to interplanting for the summer maize production under field condition. In order to enhance solar and heat utilization efficiency and excavate yield potential, it would be essential to improve the leaf photosynthesis efficiency and postpone leaf aging.

Intermittent electron density and temperature fluctuations and associated fluxes in the Alcator C-Mod scrape-off layer

NASA Astrophysics Data System (ADS)

Kube, R.; Garcia, O. E.; Theodorsen, A.; Brunner, D.; Kuang, A. Q.; LaBombard, B.; Terry, J. L.

2018-06-01

The Alcator C-Mod mirror Langmuir probe system has been used to sample data time series of fluctuating plasma parameters in the outboard mid-plane far scrape-off layer. We present a statistical analysis of one second long time series of electron density, temperature, radial electric drift velocity and the corresponding particle and electron heat fluxes. These are sampled during stationary plasma conditions in an ohmically heated, lower single null diverted discharge. The electron density and temperature are strongly correlated and feature fluctuation statistics similar to the ion saturation current. Both electron density and temperature time series are dominated by intermittent, large-amplitude burst with an exponential distribution of both burst amplitudes and waiting times between them. The characteristic time scale of the large-amplitude bursts is approximately 15 μ {{s}}. Large-amplitude velocity fluctuations feature a slightly faster characteristic time scale and appear at a faster rate than electron density and temperature fluctuations. Describing these time series as a superposition of uncorrelated exponential pulses, we find that probability distribution functions, power spectral densities as well as auto-correlation functions of the data time series agree well with predictions from the stochastic model. The electron particle and heat fluxes present large-amplitude fluctuations. For this low-density plasma, the radial electron heat flux is dominated by convection, that is, correlations of fluctuations in the electron density and radial velocity. Hot and dense blobs contribute only a minute fraction of the total fluctuation driven heat flux.

Accelerated Activation of SOCE Current in Myotubes from Two Mouse Models of Anesthetic- and Heat-Induced Sudden Death

PubMed Central

Yarotskyy, Viktor; Protasi, Feliciano; Dirksen, Robert T.

2013-01-01

Store-operated calcium entry (SOCE) channels play an important role in Ca2+ signaling. Recently, excessive SOCE was proposed to play a central role in the pathogenesis of malignant hyperthermia (MH), a pharmacogenic disorder of skeletal muscle. We tested this hypothesis by characterizing SOCE current (ISkCRAC) magnitude, voltage dependence, and rate of activation in myotubes derived from two mouse models of anesthetic- and heat-induced sudden death: 1) type 1 ryanodine receptor (RyR1) knock-in mice (Y524S/+) and 2) calsequestrin 1 and 2 double knock-out (dCasq-null) mice. ISkCRAC voltage dependence and magnitude at -80 mV were not significantly different in myotubes derived from wild type (WT), Y524S/+ and dCasq-null mice. However, the rate of ISkCRAC activation upon repetitive depolarization was significantly faster at room temperature in myotubes from Y524S/+ and dCasq-null mice. In addition, the maximum rate of ISkCRAC activation in dCasq-null myotubes was also faster than WT at more physiological temperatures (35-37°C). Azumolene (50 µM), a more water-soluble analog of dantrolene that is used to reverse MH crises, failed to alter ISkCRAC density or rate of activation. Together, these results indicate that while an increased rate of ISkCRAC activation is a common characteristic of myotubes derived from Y524S/+ and dCasq-null mice and that the protective effects of azumolene are not due to a direct inhibition of SOCE channels. PMID:24143248

Carbon dioxide makes heat therapy work

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

Sherman, H.

1987-01-01

Scientists can now propagate healthy blueberry and raspberry plants from virus-infected stock by treating it with heat and carbon dioxide. Plants are grown at 100/sup 0/F, which makes them develop faster than the virus can spread. Then cuttings are taken of the new growth - less than an inch long - and grown into full-sized, virus-free plants. But in this race to outdistance the virus, some plant species are not able to take the heat. Some even die. Chemical reactions double for every 14/sup 0/F rise in temperature. So, if you try to grow a plant at 100/sup 0/F thatmore » was originally growing at 86/sup 0/F, it will double its respiration rate. Adding carbon dioxide increases the rate of photosynthesis in plants, which increases the plant's food reserves. What carbon dioxide does to allow some plants to grow at temperatures at which they would otherwise not survive and it allows other plants to grow for longer periods at 100/sup 0/F. One problem with the process, says Converse, is that the longer plants are exposed to heat the greater the mutation rate. So, resulting clones should be closely examined for trueness to horticultural type.« less

On the sensitivities of idealized moist baroclinic waves to environmental temperature and moist convection

NASA Astrophysics Data System (ADS)

Kirshbaum, Daniel; Merlis, Timothy; Gyakum, John; McTaggart-Cowan, Ron

2017-04-01

The impact of cloud diabatic heating on baroclinic life cycles has been studied for decades, with the nearly universal finding that this heating enhances the system growth rate. However, few if any studies have systematically addressed the sensitivity of baroclinic waves to environmental temperature. For a given relative humidity, warmer atmospheres contain more moisture than colder atmospheres. They also are more prone to the development of deep moist convection, which is itself a major source of diabatic heating. Thus, it is reasonable to expect faster baroclinic wave growth in warmer systems. To address this question, this study performs idealized simulations of moist baroclinic waves in a periodic channel, using initial environments with identical relative humidities, dry stabilities, and dry available potential energies but varying environmental temperatures and moist instabilities. While the dry versions of these simulations exhibit virtually identical wave growth, the moist versions exhibit major differences in life cycle. Counter-intuitively, despite slightly faster initial wave growth, the warmer and moister waves ultimately develop into weaker baroclinic systems with an earlier onset of the decay phase. An energetics analysis reveals that the reduced wave amplitude in the warmer cases stems from a reduced transfer of available potential energy into eddy potential energy. This reduced energy transfer is associated with an unfavorable phasing of mid-to-upper-level thermal and vorticity anomalies, which limits the meridional heat flux.

Individual variation of sap-flow rate in large pine and spruce trees and stand transpiration: a pilot study at the central NOPEX site

NASA Astrophysics Data System (ADS)

Čermák, J.; Cienciala, E.; Kučera, J.; Lindroth, A.; Bednářová, E.

1995-06-01

Transpiration in a mixed old stand of sub-boreal forest in the Norunda region (central Sweden) was estimated on the basis of direct measurement of sap flow rate in 24 large Scots pine and Norway spruce trees in July and August 1993. Sap flow rate was measured using the trunk tissue heat balance method based on internal (electric) heating and sensing of temperature. Transpiration was only 0.7 mm day -1 in a relatively dry period in July (i.e. about 20% of potential evaporation) and substantially higher after a rainy period in August. The error of the estimates of transpiration was higher during a dry period (about 13% and 22% in pine and spruce, respectively) and significantly lower (about 9% in both species) during a period of sufficient water supply. Shallow-rooted spruce trees responded much faster to precipitation than deeply rooted pines.

Experimental study of cassava sun drying

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

Njie, D.N.; Rumsey, T.R.

1997-03-01

Sun drying experiments were performed to compare drying of cassava chips in sheet-metal trays with drying on mesh wire trays. In the sheet-metal trays, there was air flow across the top of the bed chips, while the mesh wire trays permitted air to flow through the bed. Drying rate was faster and more uniform in the trays with through-flow air circulation. Higher temperatures were reached by chips in the sheet-metal trays than those in the mesh trays because of contact heating, but the drying rate was lower because of the reduced air flow.

Carbon dioxide absorber and regeneration assemblies useful for power plant flue gas

DOEpatents

Vimalchand, Pannalal; Liu, Guohai; Peng, Wan Wang

2012-11-06

Disclosed are apparatus and method to treat large amounts of flue gas from a pulverized coal combustion power plant. The flue gas is contacted with solid sorbents to selectively absorb CO.sub.2, which is then released as a nearly pure CO.sub.2 gas stream upon regeneration at higher temperature. The method is capable of handling the necessary sorbent circulation rates of tens of millions of lbs/hr to separate CO.sub.2 from a power plant's flue gas stream. Because pressurizing large amounts of flue gas is cost prohibitive, the method of this invention minimizes the overall pressure drop in the absorption section to less than 25 inches of water column. The internal circulation of sorbent within the absorber assembly in the proposed method not only minimizes temperature increases in the absorber to less than 25.degree. F., but also increases the CO.sub.2 concentration in the sorbent to near saturation levels. Saturating the sorbent with CO.sub.2 in the absorber section minimizes the heat energy needed for sorbent regeneration. The commercial embodiments of the proposed method can be optimized for sorbents with slower or faster absorption kinetics, low or high heat release rates, low or high saturation capacities and slower or faster regeneration kinetics.

Sucrose modulation of radiofrequency-induced heating rates and cell death.

PubMed

Pulikkathara, Merlyn; Mark, Colette; Kumar, Natasha; Zaske, Ana Maria; Serda, Rita E

2017-09-01

Applied radiofrequency (RF) energy induces hyperthermia in tissues, facilitating vascular perfusion This study explores the impact of RF radiation on the integrity of the luminal endothelium, and then predominately explores the impact of altering the conductivity of biologically-relevant solutions on RF-induced heating rates and cell death. The ability of cells to survive high sucrose (i.e. hyperosmotic conditions) to achieve lower conductivity as a mechanism for directing hyperthermia is evaluated. RF radiation was generated using a capacitively-coupled radiofrequency system operating at 13.56 MHz. Temperatures were recorded using a FLIR SC 6000 infrared camera. RF radiation reduced cell-to-cell connections among endothelial cells and altered cell morphology towards a more rounded appearance at temperatures reported to cause in vivo vessel deformation. Isotonic solutions containing high sucrose and low levels of NaCl displayed low conductivity and faster heating rates compared to high salt solutions. Heating rates were positively correlated with cell death. Addition of sucrose to serum similarly reduced conductivity and increased heating rates in a dose-dependent manner. Cellular proliferation was normal for cells grown in media supplemented with 125 mM sucrose for 24 hours or for cells grown in 750 mM sucrose for 10 minutes followed by a 24 h recovery period. Sucrose is known to form weak hydrogen bonds in fluids as opposed to ions, freeing water molecules to rotate in an oscillating field of electromagnetic radiation and contributing to heat induction. The ability of cells to survive temporal exposures to hyperosmotic (i.e. elevated sucrose) conditions creates an opportunity to use sucrose or other saccharides to selectively elevate heating in specific tissues upon exposure to a radiofrequency field.

Reduction of Iron-Oxide-Carbon Composites: Part II. Rates of Reduction of Composite Pellets in a Rotary Hearth Furnace Simulator

NASA Astrophysics Data System (ADS)

Halder, S.; Fruehan, R. J.

2008-12-01

A new ironmaking concept is being proposed that involves the combination of a rotary hearth furnace (RHF) with an iron-bath smelter. The RHF makes use of iron-oxide-carbon composite pellets as the charge material and the final product is direct-reduced iron (DRI) in the solid or molten state. This part of the research includes the development of a reactor that simulated the heat transfer in an RHF. The external heat-transport and high heating rates were simulated by means of infrared (IR) emitting lamps. The reaction rates were measured by analyzing the off-gas and computing both the amount of CO and CO2 generated and the degree of reduction. The reduction times were found to be comparable to the residence times observed in industrial RHFs. Both artificial ferric oxide (PAH) and naturally occurring hematite and taconite ores were used as the sources of iron oxide. Coal char and devolatilized wood charcoal were the reductants. Wood charcoal appeared to be a faster reductant than coal char. However, in the PAH-containing pellets, the reverse was found to be true because of heat-transfer limitations. For the same type of reductant, hematite-containing pellets were observed to reduce faster than taconite-containing pellets because of the development of internal porosity due to cracking and fissure formation during the Fe2O3-to-Fe3O4 transition. This is, however, absent during the reduction of taconite, which is primarily Fe3O4. The PAH-wood-charcoal pellets were found to undergo a significant amount of swelling at low-temperature conditions, which impeded the external heat transport to the lower layers. If the average degree of reduction targeted in an RHF is reduced from 95 to approximately 70 pct by coupling the RHF with a bath smelter, the productivity of the RHF can be enhanced 1.5 to 2 times. The use of a two- or three-layer bed was found to be superior to that of a single layer, for higher productivities.

A kinetic study of pyrolysis and combustion of microalgae Chlorella vulgaris using thermo-gravimetric analysis.

PubMed

Agrawal, Ankit; Chakraborty, Saikat

2013-01-01

This work uses thermo-gravimetric, differential thermo-gravimetric and differential thermal analyses to evaluate the kinetics of pyrolysis (in inert/N(2) atmosphere) and (oxidative) combustion of microalgae Chlorella vulgaris by heating from 50 to 800 °C at heating rates of 5-40 °C/min. This study shows that combustion produces higher biomass conversion than pyrolysis, and that three stages of decomposition occur in both cases, of which, the second one--consisting of two temperature zones--is the main stage of devolatization. Proteins and carbohydrates are decomposed in the first of the two zones at activation energies of 51 and 45 kJ/mol for pyrolysis and combustion, respectively, while lipids are decomposed in its second zone at higher activation energies of 64 and 63 kJ/mol, respectively. The kinetic expressions of the reaction rates in the two zones for pyrolysis and combustion have been obtained and it has been shown that increased heating rates result in faster and higher conversion. Copyright © 2012 Elsevier Ltd. All rights reserved.

Mathematical Modeling of Dual Layer Shell Type Recuperation System for Biogas Dehumidification

NASA Astrophysics Data System (ADS)

Gendelis, S.; Timuhins, A.; Laizans, A.; Bandeniece, L.

2015-12-01

The main aim of the current paper is to create a mathematical model for dual layer shell type recuperation system, which allows reducing the heat losses from the biomass digester and water amount in the biogas without any additional mechanical or chemical components. The idea of this system is to reduce the temperature of the outflowing gas by creating two-layered counter-flow heat exchanger around the walls of biogas digester, thus increasing a thermal resistance and the gas temperature, resulting in a condensation on a colder surface. Complex mathematical model, including surface condensation, is developed for this type of biogas dehumidifier and the parameter study is carried out for a wide range of parameters. The model is reduced to 1D case to make numerical calculations faster. It is shown that latent heat of condensation is very important for the total heat balance and the condensation rate is highly dependent on insulation between layers and outside temperature. Modelling results allow finding optimal geometrical parameters for the known gas flow and predicting the condensation rate for different system setups and seasons.

Induction hardening: Differences to a conventional heat treatment process and optimization of its parameters

NASA Astrophysics Data System (ADS)

Vieweg, A.; Ressel, G.; Prevedel, P.; Raninger, P.; Panzenböck, M.; Marsoner, S.; Ebner, R.

2016-03-01

The possibility of obtaining similar mechanical properties with faster heating processes than the conventional ones has been of interest for several years. In the present study, investigations were performed in terms of the influences of such fast heat-treatments on the microstructure and mechanical properties of the material. This investigation compares an inductive with a conventional furnace heat treating process of a 50CrMo4 steel, however only the austenitizing treatment was changed and subsequent quenching and tempering was done in the same way. To this end experiments with a middle frequency generator, using different heating rates and austenitizing temperatures, were conducted and followed by oil quenching of the workpieces. The resulting structures were characterized regarding their microstructures and mechanical properties in order to gather a better understanding of the differences between the inductive and the conventional heat treating process. As a main result it was found, that the fast austenitized samples exhibited worse ductility than the conventional treated material.

Surface-acoustic-wave (SAW) flow sensor

NASA Astrophysics Data System (ADS)

Joshi, Shrinivas G.

1991-03-01

The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 deg rotated Y-cut lithium niobate substrate and heated to 55 C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cu cm/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

Surface-acoustic-wave (SAW) flow sensor.

PubMed

Joshi, S G

1991-01-01

The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 degrees rotated Y-cut lithium niobate substrate and heated to 55 degrees C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cm(3)/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves, propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

Repeat ridge jumps associated with plume-ridge interaction, melt transport, and ridge migration

NASA Astrophysics Data System (ADS)

Mittelstaedt, Eric; Ito, Garrett; van Hunen, Jeroen

2011-01-01

Repeated shifts, or jumps, of mid-ocean ridge segments toward nearby hot spots can produce large, long-term changes to the geometry and location of the tectonic plate boundaries. Ridge jumps associated with hot spot-ridge interaction are likely caused by several processes including shear on the base of the plate due to expanding plume material as well as reheating of lithosphere as magma passes through it to feed off-axis volcanism. To study how these processes influence ridge jumps, we use numerical models to simulate 2-D (in cross section) viscous flow of the mantle, viscoplastic deformation of the lithosphere, and melt migration upward from the asthenospheric melting zone, laterally along the base of the lithosphere, and vertically through the lithosphere. The locations and rates that magma penetrates and heats the lithosphere are controlled by the time-varying accumulation of melt beneath the plate and the depth-averaged lithospheric porosity. We examine the effect of four key parameters: magmatic heating rate of the lithosphere, plate spreading rate, age of the seafloor overlying the plume, and the plume-ridge migration rate. Results indicate that the minimum value of the magmatic heating rate needed to initiate a ridge jump increases with plate age and spreading rate. The time required to complete a ridge jump decreases with larger values of magmatic heating rate, younger plate age, and faster spreading rate. For cases with migrating ridges, models predict a range of behaviors including repeating ridge jumps, much like those exhibited on Earth. Repeating ridge jumps occur at moderate magmatic heating rates and are the result of changes in the hot spot magma flux in response to magma migration along the base of an evolving lithosphere. The tendency of slow spreading to promote ridge jumps could help explain the observed clustering of hot spots near the Mid-Atlantic Ridge. Model results also suggest that magmatic heating may significantly thin the lithosphere, as has been suggested at Hawaii and other hot spots.

Pure rotational CARS thermometry studies of low-temperature oxidation kinetics in air and ethene-air nanosecond pulse discharge plasmas

NASA Astrophysics Data System (ADS)

Zuzeek, Yvette; Choi, Inchul; Uddi, Mruthunjaya; Adamovich, Igor V.; Lempert, Walter R.

2010-03-01

Pure rotational CARS thermometry is used to study low-temperature plasma assisted fuel oxidation kinetics in a repetitive nanosecond pulse discharge in ethene-air at stoichiometric and fuel lean conditions at 40 Torr pressure. Air and fuel-air mixtures are excited by a burst of high-voltage nanosecond pulses (peak voltage, 20 kV; pulse duration, ~ 25 ns) at a 40 kHz pulse repetition rate and a burst repetition rate of 10 Hz. The number of pulses in the burst is varied from a few pulses to a few hundred pulses. The results are compared with the previously developed hydrocarbon-air plasma chemistry model, modified to incorporate non-empirical scaling of the nanosecond discharge pulse energy coupled to the plasma with number density, as well as one-dimensional conduction heat transfer. Experimental time-resolved temperature, determined as a function of the number of pulses in the burst, is found to agree well with the model predictions. The results demonstrate that the heating rate in fuel-air plasmas is much faster compared with air plasmas, primarily due to energy release in exothermic reactions of fuel with O atoms generated by the plasma. It is found that the initial heating rate in fuel-air plasmas is controlled by the rate of radical (primarily O atoms) generation and is nearly independent of the equivalence ratio. At long burst durations, the heating rate in lean fuel air-mixtures is significantly reduced when all fuel is oxidized.

Beetle Exoskeleton May Facilitate Body Heat Acting Differentially across the Electromagnetic Spectrum.

PubMed

Carrascal, Luis M; Ruiz, Yolanda Jiménez; Lobo, Jorge M

Exoskeletons of beetles and their associated morphological characteristics can serve many different functions, including thermoregulation. We study the thermal role of the exoskeleton in 13 Geotrupidae dung beetle species using heating experiments under controlled conditions. The main purpose was to measure the influence of heating sources (solar radiance vs. infrared), animal position (dorsal exposure vs. ventral exposure), species identity, and phylogenetic relationships on internal asymptotic temperatures and heating rates. The thermal response was significantly influenced by phylogenetic relatedness, although it was not affected by the apterous condition. The asymptotic internal temperature of specimens was not affected by the thoracic volume but was significantly higher under simulated sunlight conditions than under infrared radiation and when exposed dorsally as opposed to ventrally. There was thus a significant interaction between heating source and body position. Heating rate was negatively and significantly influenced by thoracic volume, and, although insignificantly slower under simulated sunlight, it was significantly affected by body position, being faster under dorsal exposure. The results constitute the first evidence supporting the hypothesis that the beetle exoskeleton acts differentially across the electromagnetic spectrum determining internal body temperatures. This interesting finding suggests the existence of a kind of passive physiology imposed by the exoskeleton and body size, where interspecific relationships play a minor role.

Numerical analysis of fluid flow and heat transfer during melting inside a cylindrical container for thermal energy storage system

NASA Astrophysics Data System (ADS)

Bellan, Selvan; Cheok, Cho Hyun; Gokon, Nobuyuki; Matsubara, Koji; Kodama, Tatsuya

2017-06-01

This paper presents a numerical analysis of unconstrained melting of high temperature(>1000K) phase change material (PCM) inside a cylindrical container. Sodium chloride and Silicon carbide have been used as phase change material and shell of the capsule respectively. The control volume discretization approach has been used to solve the conservation equations of mass, momentum and energy. The enthalpy-porosity method has been used to track the solid-liquid interface of the PCM during melting process. Transient numerical simulations have been performed in order to study the influence of radius of the capsule and the Stefan number on the heat transfer rate. The simulation results show that the counter-clockwise Buoyancy driven convection over the top part of the solid PCM enhances the melting rate quite faster than the bottom part.

The role and importance of porosity in the deflagration rates of HMX-based materials

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

Glascoe, E A; Hsu, P C; Springer, H K

The deflagration behavior of thermally damaged HMX-based materials will be discussed. Strands of material were burned at pressures ranging from 10-300 MPa using the LLNL high pressure strand burner. Strands were heated in-situ and burned while still hot; temperatures range from 90-200 C and were chosen in order to allow for thermal damage of the material without significant decomposition of the HMX. The results indicate that multiple variables affect the burn rate but the most important are the polymorph of HMX and the nature and thermal stability of the non-HE portion of the material. Characterization of the strands indicate thatmore » the thermal soak produces significant porosity and permeability in the sample allowing for significantly faster burning due to the increased surface area and new pathways for flame spread into the material. Specifically, the deflagration rates of heated PBXN-9, LX-10, and PBX-9501 will be discussed and compared.« less

Preferential Heating and Acceleration of Heavy Ions in Impulsive Solar Flares

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

Kumar, Rahul; Gaspari, Massimo; Spitkovsky, Anatoly

2017-02-01

We simulate decaying turbulence in a homogeneous pair plasma using a three-dimensional electromagnetic particle-in-cell method. A uniform background magnetic field permeates the plasma such that the magnetic pressure is three times larger than the thermal pressure and the turbulence is generated by counter-propagating shear Alfvén waves. The energy predominately cascades transverse to the background magnetic field, rendering the turbulence anisotropic at smaller scales. We simultaneously move several ion species of varying charge to mass ratios in our simulation and show that the particles of smaller charge to mass ratios are heated and accelerated to non-thermal energies at a faster rate.more » This is in accordance with the enhancement of heavy ions and a non-thermal tail in their energy spectrum observed in the impulsive solar flares. We further show that the heavy ions are energized mostly in the direction perpendicular to the background magnetic field, with a rate consistent with our analytical estimate of the rate of heating due to cyclotron resonance with the Alfvén waves, of which a large fraction is due to obliquely propagating waves.« less

Thermal-hydraulic behaviors of vapor-liquid interface due to arrival of a pressure wave

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

Inoue, Akira; Fujii, Yoshifumi; Matsuzaki, Mitsuo

In the vapor explosion, a pressure wave (shock wave) plays a fundamental role for triggering, propagation and enhancement of the explosion. Energy of the explosion is related to the magnitude of heat transfer rate from hot liquid to cold volatile one. This is related to an increasing rate of interface area and to an amount of transient heat flux between the liquids. In this study, the characteristics of transient heat transfer and behaviors of vapor film both on the platinum tube and on the hot melt tin drop, under same boundary conditions have been investigated. It is considered that theremore » exists a fundamental mechanism of the explosion in the initial expansion process of the hot liquid drop immediately after arrival of pressure wave. The growth rate of the vapor film is much faster on the hot liquid than that on the solid surface. Two kinds of roughness were observed, one due to the Taylor instability, by rapid growth of the explosion bubble, and another, nucleation sites were observed at the vapor-liquid interface. Based on detailed observation of early stage interface behaviors after arrival of a pressure wave, the thermal fragmentation mechanism is proposed.« less

Experiment and ANSYS simulation analysis for metal aluminum solid and fluid conversion

NASA Astrophysics Data System (ADS)

Wang, Y.-Y.; Guo, P.; Wu, Y.; Zhang, Z.-L.; Jiang, S.-M.

2017-11-01

In this paper, study on metal aluminum solid and fluid conversion was carried out by using crucible resistance furnace, and observing the phenomenon of metal aluminum solid and fluid conversion. In the experiment, the same shape aluminum block was kept under the same heating rate and heated by the resistance furnace. The experimental results show that the melting point of metal aluminum is between 650°C and 660°C, and after the melting point, the metal aluminum began to melt when it maintained for a long period of time, however, when the temperature is higher than the melting point, the aluminum will melt very quickly. In addition, in ANSYS simulation, the solid aluminum melted completely at 670°C in 5430 seconds, much longer than the actual experiment, it due to the heating rate was faster, not in an ideal experimental environment and there is heat exchange with the outside world and convection, at the same time, the aluminum block may contain impurities, so the actual melting time could be shorter than the simulation. In this paper, it was explored for the liquid and solid conversion in depth, and had a certain actual value.

Perceived Cooling Using Asymmetrically-Applied Hot and Cold Stimuli.

PubMed

Manasrah, Ahmad; Crane, Nathan; Guldiken, Rasim; Reed, Kyle B

2017-01-01

Temperature perception is a highly nonlinear phenomenon with faster rates of change being perceived at much lower thresholds than slower rates. This paper presents a method that takes advantage of this nonlinear characteristic to generate a perception of continuous cooling even though the average temperature is not changing. The method uses multiple thermal actuators so that a few are cooling quickly while the rest of the actuators are heating slowly. The slowly-heating actuators are below the perceptual threshold temperature change and hence are not perceived, while the quickly-cooling actuators are above the perceptual temperature change, hence are perceived. As a result, a feeling of decreasing temperature was elicited, when in fact, there was no net change in the temperature of the skin. Three sets of judiciously designed experiments were conducted in this study, investigating the effects of actuator sizes, forearm measurement locations, patterns of actuator layout, and various heating/cooling time cycles. Our results showed that 19 out 21 participants perceived the continuous cooling effect as hypothesized. Our research indicates that the measurement location, heating/cooling cycle times, and arrangement of the actuators affect the perception of continuous cooling.

Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite.

PubMed

Mardoukhi, Ahmad; Mardoukhi, Yousof; Hokka, Mikko; Kuokkala, Veli-Tapani

2017-01-28

This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

Female pheromones modulate flight muscle activation patterns during preflight warm-up.

PubMed

Crespo, José G; Vickers, Neil J; Goller, Franz

2013-08-01

At low ambient temperature Helicoverpa zea male moths engage in warm-up behavior prior to taking flight in response to an attractive female pheromone blend. Male H. zea warm up at a faster rate when sensing the attractive pheromone blend compared with unattractive blends or blank controls (Crespo et al. 2012), but the mechanisms involved in this olfactory modulation of the heating rate during preflight warm-up are unknown. Here, we test three possible mechanisms for increasing heat production: 1) increased rate of muscle contraction; 2) reduction in mechanical movement by increased overlap in activation of the antagonistic flight muscles; and 3) increased activation of motor units. To test which mechanisms play a role, we simultaneously recorded electrical activation patterns of the main flight muscles (dorsolongitudinal and dorsoventral muscles), wing movement, and thoracic temperature in moths exposed to both the attractive pheromone blend and a blank control. Results indicate that the main mechanism responsible for the observed increase in thoracic heating rate with pheromone stimulation is the differential activation of motor units during each muscle contraction cycle in both antagonistic flight muscles. This additional activation lengthens the contracted state within each cycle and thus accounts for the greater heat production. Interestingly, the rate of activation (frequency of contraction cycles) of motor units, which is temperature dependent, did not vary between treatments. This result suggests that the activation rate is determined by a temperature-dependent oscillator, which is not affected by the olfactory stimulus, but activation of motor units is modulated during each cycle.

Female pheromones modulate flight muscle activation patterns during preflight warm-up

PubMed Central

Vickers, Neil J.; Goller, Franz

2013-01-01

At low ambient temperature Helicoverpa zea male moths engage in warm-up behavior prior to taking flight in response to an attractive female pheromone blend. Male H. zea warm up at a faster rate when sensing the attractive pheromone blend compared with unattractive blends or blank controls (Crespo et al. 2012), but the mechanisms involved in this olfactory modulation of the heating rate during preflight warm-up are unknown. Here, we test three possible mechanisms for increasing heat production: 1) increased rate of muscle contraction; 2) reduction in mechanical movement by increased overlap in activation of the antagonistic flight muscles; and 3) increased activation of motor units. To test which mechanisms play a role, we simultaneously recorded electrical activation patterns of the main flight muscles (dorsolongitudinal and dorsoventral muscles), wing movement, and thoracic temperature in moths exposed to both the attractive pheromone blend and a blank control. Results indicate that the main mechanism responsible for the observed increase in thoracic heating rate with pheromone stimulation is the differential activation of motor units during each muscle contraction cycle in both antagonistic flight muscles. This additional activation lengthens the contracted state within each cycle and thus accounts for the greater heat production. Interestingly, the rate of activation (frequency of contraction cycles) of motor units, which is temperature dependent, did not vary between treatments. This result suggests that the activation rate is determined by a temperature-dependent oscillator, which is not affected by the olfactory stimulus, but activation of motor units is modulated during each cycle. PMID:23699056

Solar Radiation during Rewarming from Torpor in Elephant Shrews: Supplementation or Substitution of Endogenous Heat Production?

PubMed Central

Thompson, Michelle L.; Mzilikazi, Nomakwezi; Bennett, Nigel C.; McKechnie, Andrew E.

2015-01-01

Many small mammals bask in the sun during rewarming from heterothermy, but the implications of this behaviour for their energy balance remain little understood. Specifically, it remains unclear whether solar radiation supplements endogenous metabolic thermogenesis (i.e., rewarming occurs through the additive effects of internally-produced and external heat), or whether solar radiation reduces the energy required to rewarm by substituting (i.e, replacing) metabolic heat production. To address this question, we examined patterns of torpor and rewarming rates in eastern rock elephant shrews (Elephantulus myurus) housed in outdoor cages with access to either natural levels of solar radiation or levels that were experimentally reduced by means of shade cloth. We also tested whether acclimation to solar radiation availability was manifested via phenotypic flexibility in basal metabolic rate (BMR), non-shivering thermogenesis (NST) capacity and/or summit metabolism (Msum). Rewarming rates varied significantly among treatments, with elephant shrews experiencing natural solar radiation levels rewarming faster than conspecifics experiencing solar radiation levels equivalent to approximately 20% or 40% of natural levels. BMR differed significantly between individuals experiencing natural levels of solar radiation and conspecifics experiencing approximately 20% of natural levels, but no between-treatment difference was evident for NST capacity or Msum. The positive relationship between solar radiation availability and rewarming rate, together with the absence of acclimation in maximum non-shivering and total heat production capacities, suggests that under the conditions of this study solar radiation supplemented rather than substituted metabolic thermogenesis as a source of heat during rewarming from heterothermy. PMID:25853244

Solar radiation during rewarming from torpor in elephant shrews: supplementation or substitution of endogenous heat production?

PubMed

Thompson, Michelle L; Mzilikazi, Nomakwezi; Bennett, Nigel C; McKechnie, Andrew E

2015-01-01

Many small mammals bask in the sun during rewarming from heterothermy, but the implications of this behaviour for their energy balance remain little understood. Specifically, it remains unclear whether solar radiation supplements endogenous metabolic thermogenesis (i.e., rewarming occurs through the additive effects of internally-produced and external heat), or whether solar radiation reduces the energy required to rewarm by substituting (i.e, replacing) metabolic heat production. To address this question, we examined patterns of torpor and rewarming rates in eastern rock elephant shrews (Elephantulus myurus) housed in outdoor cages with access to either natural levels of solar radiation or levels that were experimentally reduced by means of shade cloth. We also tested whether acclimation to solar radiation availability was manifested via phenotypic flexibility in basal metabolic rate (BMR), non-shivering thermogenesis (NST) capacity and/or summit metabolism (Msum). Rewarming rates varied significantly among treatments, with elephant shrews experiencing natural solar radiation levels rewarming faster than conspecifics experiencing solar radiation levels equivalent to approximately 20% or 40% of natural levels. BMR differed significantly between individuals experiencing natural levels of solar radiation and conspecifics experiencing approximately 20% of natural levels, but no between-treatment difference was evident for NST capacity or Msum. The positive relationship between solar radiation availability and rewarming rate, together with the absence of acclimation in maximum non-shivering and total heat production capacities, suggests that under the conditions of this study solar radiation supplemented rather than substituted metabolic thermogenesis as a source of heat during rewarming from heterothermy.

Impact of local hydrothermal treatment during bread baking on soluble amylose, firmness, amylopectin retrogradation and water mobility during bread staling.

PubMed

Besbes, Emna; Le Bail, Alain; Seetharaman, Koushik

2016-01-01

The impact of hydrothermal processing undergone by bread dough during baking on the degree of starch granule disruption, on leaching of soluble amylose, on water mobility, on firmness and on amylopectin retrogradation during staling has been investigated. Two heating rates during baking have been considered (4.67 and 6.31 °C/min) corresponding respectively to baking temperature of 220 and 240 °C. An increase in firmness and in the amount of retrogradated amylopectin accompanied by a decrease in freezable water has been observed during staling. Although a lower heating rate yielded in larger amount of retrogradated amylopectin retrogradation, it resulted in a lower firmness. Additionally, the amount of soluble amylose and the relaxation times of water measured by Nuclear Magnetic Resonance NMR (T20, T21 and T22) decreased during staling. It was demonstrated that the amount of soluble amylose was higher for bread crumb baked at lower heating rate, indicating that an increasing amount of amylose is leached outside the starch granules. This was corresponding to a greater amount of retrograded amylopectin during staling. Moreover, it was found that the degree of gelatinization differs locally in a same bread slice between the top, the centre and the bottom locations in the crumb. This was attributed to the differences in kinetics of heating, the availability of water during baking and the degree of starch granule disruption during baking. Based on first order kinetic model, it was found that staling kinetics were faster for samples baked at higher heating rate.

The Feasibility of Conformal Thermal Therapy with Transurethral Ultrasound Heating Applicators and MR Temperature Feedback

NASA Astrophysics Data System (ADS)

Choy, Vanessa; Tang, Kee; Wachsmuth, Jeff; Chopra, Rajiv; Bronskill, Michael

2006-05-01

Transurethral thermal therapy offers a minimally invasive alternative for the treatment of prostate diseases including benign prostate hyperplasia (BPH) and prostate cancer. Accurate heating of a targeted region of the gland can be achieved through the use of a rotating directional heating source incorporating planar ultrasound transducers, and the implementation of active temperature feedback along the beam direction during heating provided by magnetic resonance (MR) thermometry. The performance of this control method with practical spatial, temporal, and temperature resolution (such as angular alignment, spatial resolution, update rate for temperature feedback (imaging time), and the presence of noise) for thermal feedback using a clinical 1.5 T MR scanner was investigated in simulations. As expected, the control algorithm was most sensitive to the presence of noise, with noticeable degradation in its performance above ±2°C of temperature uncertainty. With respect to temporal resolution, acceptable performance was achieved at update rates of 5s or faster. The control algorithm was relatively insensitive to reduced spatial resolution due to the broad nature of the heating pattern produced by the heating applicator, this provides an opportunity to improve signal-to-noise ratio (SNR). The overall simulation results confirm that existing clinical 1.5T MR imagers are capable of providing adequate temperature feedback for transurethral thermal therapy without special pulse sequences or enhanced imaging hardware.

Reactive Shear Layer Mixing and Growth Rate Effects on Afterburning Properties for Axisymetric Rocket Engine Plumes

DTIC Science & Technology

2006-09-01

water, carbon monoxide and carbon dioxide . The ratio of specific heats is reduced as the number of atoms in the molecule increases and as the...The flow of the jet is faster than the surrounding air, and since gas turbine engines run fuel lean, the exhaust products have generally fully reacted...previous types by several characteristics. The core of the rocket exhaust flowfield is fuel rich, and unlike gas turbine engines, which burn fuel

Comparison of blood pressure and thermal responses in rats exposed to millimeter wave energy or environmental heat.

PubMed

Millenbaugh, Nancy J; Kiel, Johnathan L; Ryan, Kathy L; Blystone, Robert V; Kalns, John E; Brott, Becky J; Cerna, Cesario Z; Lawrence, William S; Soza, Laura L; Mason, Patrick A

2006-06-01

Electromagnetic fields at millimeter wave lengths are being developed for commercial and military use at power levels that can cause temperature increases in the skin. Previous work suggests that sustained exposure to millimeter waves causes greater heating of skin, leading to faster induction of circulatory failure than exposure to environmental heat (EH). We tested this hypothesis in three separate experiments by comparing temperature changes in skin, subcutis, and colon, and the time to reach circulatory collapse (mean arterial blood pressure, 20 mmHg) in male Sprague-Dawley rats exposed to the following conditions that produced similar rates of body core heating within each experiment: (1) EH at 42 degrees C, 35 GHz at 75 mW/cm, or 94 GHz at 75 mW/cm under ketamine and xylazine anesthesia; (2) EH at 43 degrees C, 35 GHz at 90 mW/cm, or 94 GHz at 90 mW/cm under ketamine and xylazine anesthesia; and (3) EH at 42 degrees C, 35 GHz at 90 mW/cm, or 94 GHz at 75 mW/cm under isoflurane anesthesia. In all three experiments, the rate and amount of temperature increase at the subcutis and skin surface differed significantly in the rank order of 94 GHz more than 35 GHz more than EH. The time to reach circulatory collapse was significantly less only for rats exposed to 94 GHz at 90 mW/cm, the group with the greatest rate of skin and subcutis heating of all groups in this study, compared with both the 35 GHz at 90 mW/cm and the EH at 43 degrees C groups. These data indicate that body core heating is the major determinant of induction of hemodynamic collapse, and the influence of heating of the skin and subcutis becomes significant only when a certain threshold rate of heating of these tissues is exceeded.

Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite

PubMed Central

Kuokkala, Veli-Tapani

2017-01-01

This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’. PMID:27956513

From first galaxies to QSOs - feeding the baby monsters

NASA Astrophysics Data System (ADS)

Danese, L.; Shankar, F.; Granato, G. L.; Silva, L.; Bressan, A.; de Zotti, G.; Salucci, P.; Cirasuolo, M.

We present a physical model for the coevolution of massive spheroidal galaxies and active nuclei at their centers. Supernova heating is increasingly effective in slowing down the star formation and in driving gas outflows in smaller and smaller dark matter halos. Thus the more massive protogalaxies virializing at early times are the sites of faster star formation. The correspondingly higher radiation drag causes a faster angular momentum loss by the gas and induces a larger accretion rate onto the central black hole. In turn, the kinetic energy of the outflows powered by the active nuclei can unbind the residual gas in a time shorter for larger halos. The model accounts for a broad variety of dynamical, photometric and metallicity properties of early-type galaxies, for the MBH-σ relation and for the local supermassive black-hole mass function.

Energy cost of the Trondheim firefighter test for experienced firefighters.

PubMed

von Heimburg, Erna; Medbø, Jon Ingulf

2013-01-01

The aim of this study was to measure aerobic demands of fire fighting activities including exercise in the heat. Twenty-two experienced firefighters performed the Trondheim test simulating fire fighting tasks including work in the heat. Maximal oxygen uptake (VO2 max), heart rate (HR) and ventilation were recorded continuously. Data were compared with results obtained during a treadmill test during which the participants were dressed as smoke divers. The participants completed physical parts of the Trondheim test in ˜12 min (range: 7.5-17.4). Time to complete the test was closely related to the participant's VO2 max. HR of ˜170 beats/min and pulmonary ventilation of ˜100 L/min were higher than at lactate threshold (LT) during laboratory tests. VO2 averaged over the test's physical part was 35 ± 7 ml/min/kg, which was at the same or below the level corresponding to the participants' LT. Physically fit participants completed the test faster than less fit participants. Slower and physically less fit participants consumed more air and used more oxygen than faster and physically more fit participants. The Trondheim test is physically demanding; it distinguishes physically fit and less fit participants.

Experimental study on flowing burning behaviors of a pool fire with dripping of melted thermoplastics.

PubMed

Xie, Qiyuan; Tu, Ran; Wang, Nan; Ma, Xin; Jiang, Xi

2014-02-28

The objective of this work is to quantitatively investigate the dripping-burning and flowing fire of thermoplastics. A new experimental setup is developed with a heating vessel and a T-trough. Hot thermoplastic liquids are generated in the vessel by electric heating. N2 gas is continuously injected into the vessel to avoid a sudden ignition of fuel in it. The detailed flowing burning behaviors of pool fire in the T-trough are analyzed through the measurements of the mass, heat flux and temperatures etc. The experimental results suggest that a continuous dripping of melted thermoplastic liquids in a nearly constant mass rate can be successfully made in the new setup. It also shows that the mass dripping rate of melted PS liquid is smaller than PP and PE since its large viscosity. In addition, the flame spread velocities of hot liquids of PS in the T-trough are also smaller than that of PP and PE because of its large viscosity. The mass burning rate of the PP and PE pool fire in T-trough are smaller than PS. Finally, considering the heating, melting, dripping and flowing burning behaviors of these polymers, it is suggested that the fire hazard of PE and PP are obviously higher than PS for their faster flowing burning. Copyright © 2013 Elsevier B.V. All rights reserved.

Association of High Cardiovascular Fitness and the Rate of Adaptation to Heat Stress

PubMed Central

Nowak-Zaleska, Alicja; Chruściński, Grzegorz; Zaleski, Ryszard; Tymański, Roman; Kochanowicz, Andrzej

2018-01-01

This study aimed to compare changes in genes expression associated with inflammation and apoptosis in response to heat stress caused by sauna between people with varying cardiorespiratory fitness levels. We hypothesis that high cardiorespiratory level caused higher positive changes after four weeks of sauna bathing. Blood samples were taken at rest before and after the first and last sauna sessions and 48 hours after the last sauna session and used to assay HSP70 (HSPA1A), HSP27 (HSPB1), interleukin 6 (IL6), and interleukin 10 (IL10) genes expression in blood with quantitative real-time qRT-PCR. Overall, small decreases in rest values of HSPA1A and IL6 mRNA, increase in HSPB1 mRNA, and a significant increase in IL10 mRNA were observed after four weeks of exposure to heat stress. Our findings suggest that an adaptive response to heat stress (an anti-inflammatory response) occurs faster in people with higher cardiorespiratory fitness. PMID:29682518

Human-like collagen protein-coated magnetic nanoparticles with high magnetic hyperthermia performance and improved biocompatibility

NASA Astrophysics Data System (ADS)

Liu, Xiaoli; Zhang, Huan; Chang, Le; Yu, Baozhi; Liu, Qiuying; Wu, Jianpeng; Miao, Yuqing; Ma, Pei; Fan, Daidi; Fan, Haiming

2015-01-01

Human-like collagen (HLC)-coated monodispersed superparamagnetic Fe3O4 nanoparticles have been successfully prepared to investigate its effect on heat induction property and cell toxicity. After coating of HLC, the sample shows a faster rate of temperature increase under an alternating magnetic field although it has a reduced saturation magnetization. This is most probably a result of the effective heat conduction and good colloid stability due to the high charge of HLC on the surface. In addition, compared with Fe3O4 nanoparticles before coating with HLC, HLC-coated Fe3O4 nanoparticles do not induce notable cytotoxic effect at higher concentration which indicates that HLC-coated Fe3O4 nanoparticles has improved biocompatibility. Our results clearly show that Fe3O4 nanoparticles after coating with HLC not only possess effective heat induction for cancer treatment but also have improved biocompatibility for biomedicine applications.

Sensitivity of geomagnetic reversal rate on core evolution from numerical dynamos

NASA Astrophysics Data System (ADS)

Driscoll, P. E.; Davies, C. J.

2017-12-01

The paleomagnetic record indicates the geodynamo has evolved from frequently reversing to non-reversing (superchron) magnetic states several times over the Phanerozoic. Previous theoretical studies demonstrated a positive correlation between magnetic reversal rate and core-mantle boundary heat flux. However, attempts to identify such a correlation between reversal rates and proxies for internal cooling rate, such as plume events, superchron cycles, and subduction rates, have been inconclusive. Here we revisit the magnetic reversal occurrence rate in numerical dynamos at low Ekman numbers (faster rotation) and high magnetic Prandtl numbers (ratio of viscous and magnetic diffusivities). We focus on how the correlation between reversal rate and convective power depends on the core evolution rate and on other factors, such as Ek, Pm, and thermal boundary conditions. We apply our results to the seafloor reversal record in an attempt to infer the energetic evolution of the lower mantle and core over that period.

Skin temperature and heart rate can be used to estimate physiological strain during exercise in the heat in a cohort of fit and unfit males.

PubMed

Cuddy, John S; Buller, Mark; Hailes, Walter S; Ruby, Brent C

2013-07-01

To evaluate the previously developed physiological strain index (PSI) model using heart rate and skin temperature to provide further insight into the detection and estimation of thermal and physiological heat strain indices. A secondary aim was to characterize individuals who excel in their performance in the heat. 56 male participants completed 2 walking trials (3.5 miles per hour, 5% grade) in controlled environments of 43.3 °C and 15.5 °C (40% humidity). Core and skin temperature, along with heart rate and PSI, were continually monitored during exercise. Participants completed a physical fitness test. The logistic regression model exhibited 4 false positives and 1 false negative at the 40% decision boundary. The "Not at Risk" group (N = 33) had higher body weight (84 ± 13 vs. 77 ± 10 kg, respectively) compared to the "At Risk" (N = 23) group, p < 0.05. The "Not at Risk" group had a faster 3-mile run time compared to the "At Risk" group (21:53 ± 3:13 vs. 25:16 ± 2:37, respectively), p < 0.05. During the Heat Trial, the "At Risk" group had a higher rating of perceived exertion at 60 and 90 minutes compared to the "Not at Risk" group (13.5 ± 2.8 vs. 11.5 ± 1.8 and 14.8 ± 3.2 vs. 12.2 ± 2.0 for "At Risk" vs. "Not at Risk" at 60 and 90 minutes, respectively), p < 0.05. The previously developed model relating heart rate and skin temperature to PSI is highly accurate at assessing heat risk status. Participants classified as "At Risk" had lower physical performance scores and different body weights compared to the "Not at Risk" group and perceived themselves as working harder during exercise in the heat. Reprint & Copyright © 2013 Association of Military Surgeons of the U.S.

Temperature controller for crystal resonators

NASA Technical Reports Server (NTRS)

Turlington, T. R.

1980-01-01

Controller operates on less than 5W prime power and heats crystal from -10 C to 75 C in less than 45s. Unit is faster and more accurate (to within 0.7 C) than other inexpensive controllers and faster and less expensive than very precise controllers in vacuum flasks.

Analysis of a self-propelling sheet with heat transfer through non-isothermal fluid in an inclined human cervical canal.

PubMed

Walait, Ahsan; Siddiqui, A M; Rana, M A

2018-02-13

The present theoretical analysis deals with biomechanics of the self-propulsion of a swimming sheet with heat transfer through non-isothermal fluid filling an inclined human cervical canal. Partial differential equations arising from the mathematical modeling of the proposed model are solved analytically. Flow variables like pressure gradient, propulsive velocity, fluid velocity, time mean flow rate, fluid temperature, and heat-transfer coefficients are analyzed for the pertinent parameters. Striking features of the pumping characteristics are explored. Propulsive velocity of the swimming sheet becomes faster for lower Froude number, higher Reynolds number, and for a vertical channel. Temperature and peak value of the heat-transfer coefficients below the swimming sheet showed an increase by the increment of Brinkmann number, inclination, pressure difference over wavelength, and Reynolds number whereas these quantities decrease with increasing Froude number. Aforesaid parameters have shown opposite effects on the peak value of the heat-transfer coefficients below and above the swimming sheet. Relevance of the current results to the spermatozoa transport with heat transfer through non-isothermal cervical mucus filling an inclined human cervical canal is also explored.

Factors affecting energy deposition and expansion in single wire low current experiments

NASA Astrophysics Data System (ADS)

Duselis, Peter U.; Vaughan, Jeffrey A.; Kusse, Bruce R.

2004-08-01

Single wire experiments were performed on a low current pulse generator at Cornell University. A 220 nF capacitor charged to 15-25 kV was used to drive single wire experiments. The capacitor and wire holder were connected in series through an external variable inductor to control the current rise rate. This external series inductance was adjustable from 0.2 to 2 μH. When coupled with the range of charging voltages this results in current rise rates from 5 to 50 A/ns. The current heated the wire through liquid and vapor phases until plasma formed around the wire. Energy deposition and expansion rates were measured as functions of the current rise rate. These results indicated better energy deposition and higher expansion rates with faster current rise rates. Effects of the wire-electrode connection method and wire polarity were also studied.

Opposed-flow Flame Spread Over Solid Fuels in Microgravity: the Effect of Confined Spaces

NASA Astrophysics Data System (ADS)

Wang, Shuangfeng; Hu, Jun; Xiao, Yuan; Ren, Tan; Zhu, Feng

2015-09-01

Effects of confined spaces on flame spread over thin solid fuels in a low-speed opposing flow is investigated by combined use of microgravity experiments and computations. The flame behaviors are observed to depend strongly on the height of the flow tunnel. In particular, a non-monotonic trend of flame spread rate versus tunnel height is found, with the fastest flame occurring in the 3 cm high tunnel. The flame length and the total heat release rate from the flame also change with tunnel height, and a faster flame has a larger length and a higher heat release rate. The computation analyses indicate that a confined space modifies the flow around the spreading flame. The confinement restricts the thermal expansion and accelerates the flow in the streamwise direction. Above the flame, the flow deflects back from the tunnel wall. This inward flow pushes the flame towards the fuel surface, and increases oxygen transport into the flame. Such a flow modification explains the variations of flame spread rate and flame length with tunnel height. The present results suggest that the confinement effects on flame behavior in microgravity should be accounted to assess accurately the spacecraft fire hazard.

Accelerated uplift and magmatic intrusion of the Yellowstone caldera, 2004 to 2006

USGS Publications Warehouse

Chang, Wu-Lung; Smith, Robert B.; Wicks, Charles; Farrell, J.M.; Puskas, C.M.

2007-01-01

The Yellowstone caldera began a rapid episode of ground uplift in mid-2004, revealed by Global Positioning System and interferometric synthetic aperture radar measurements, at rates up to 7 centimeters per year, which is over three times faster than previously observed inflation rates. Source modeling of the deformation data suggests an expanding volcanic sill of ???1200 square kilometers at a 10-kilometer depth beneath the caldera, coincident with the top of a seismically imaged crustal magma chamber. The modeled rate of source volume increase is 0.1 cubic kilometer per year, similar to the amount of magma intrusion required to supply the observed high heat flow of the caldera. This evidence suggests magma recharge as the main mechanism for the accelerated uplift, although pressurization of magmatic fluids cannot be ruled out.

Maximum heat of mass concrete - phase 2 [summary].

DOT National Transportation Integrated Search

2016-12-01

Concrete hardens through a chemical reaction that produces heat and expansion, followed by contraction as the concrete cools. Concrete near the edge of a pour cools faster and shrinks earlier than concrete further from the edge. Most concrete pours a...

Water nucleation in helium, methane, and argon: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Dumitrescu, Lucia R.; Huinink, Henk; Smeulders, David M. J.; Dam, Jacques A. M.; Gaastra-Nedea, Silvia V.

2018-05-01

Nucleation of highly supersaturated water vapor in helium, methane, and argon carrier gases at 350 K was investigated using molecular dynamics simulations. Nucleation rates obtained from the mean first passage time (MFPT) method are typically one order of magnitude lower than those from the Yasuoka and Matsumoto method, which can be attributed to the overestimation of the critical cluster size in the MFPT method. It was found that faster nucleation will occur in carrier gases that have better thermalization properties such that latent heat is removed more efficiently. These thermalization properties are shown to be strongly dependent on the molecular mass and Lennard-Jones (LJ) parameters. By varying the molecular mass, for unaltered LJ parameters, it was found that a heavier carrier gas removes less heat although it has a higher collision rate with water than a lighter carrier. Thus, it was shown that a clear distinction between water vapor-carrier gas collisions and water cluster-carrier gas collisions is indispensable for understanding the effect of collision rates on thermalization. It was also found that higher concentration of carrier gas leads to higher nucleation rate. The nucleation rates increased by a factor of 1.3 for a doubled concentration and by almost a factor of two for a tripled concentration.

Effect of homogenization and heat treatment on the behavior of protein and fat globules during gastric digestion of milk.

PubMed

Ye, Aiqian; Cui, Jian; Dalgleish, Douglas; Singh, Harjinder

2017-01-01

The effects of homogenization and heat treatment on the formation and the breakdown of clots during gastric digestion of whole milk were investigated using a human gastric simulator. Homogenization and heat treatment led to formation of coagula with fragmented and crumbled structures compared with the coagulum formed from raw whole milk, but a larger fraction of the protein and more fat globules were incorporated into the coagula induced by action of the milk-clotting enzyme pepsin. The fat globules in the whole milk appeared to be embedded in the clots as they formed. After formation of the clot, the greater numbers of pores in the structures of the clots formed with homogenized milk and heated whole milk led to greater rates of protein hydrolysis by pepsin, which resulted in faster release of fat globules from the clots into the digesta. Coalescence of fat globules occurred both in the digesta and within the protein clots no matter whether they were in homogenized or heated milk samples. The formation of clots with different structures and hence the changes in the rates of protein hydrolysis and the release of milk fat into the digesta in the stomach provide important information for understanding the gastric emptying of milk and the potential to use this knowledge to manipulate the bioavailability of fat and other fat-soluble nutrients in dairy products. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Temperature dependence of blood viscosity in frogs and turtles: effect on heat exchange with environment.

PubMed

Langille, B L; Crisp, B

1980-09-01

The temperature dependence of the viscosity of blood from frogs and turtles has been assessed for temperatures between 5 and 40 degrees C. Viscosity of turtles' blood was, on average, reduced from 3.50 +/- 0.16 to 2.13 +/- 0.10 cP between 10 and 30 degrees C, a decline of 39%. Even larger changes in viscosity were observed for frogs' blood with viscosity falling from 4.55 +/- 0.32 to 2.55 +/- 0.25 cP over the same temperature range, a change of 44%. Blood viscosity was highly correlated with hematocrit in both species at all temperatures. Viscosity of blood from both frogs and turtles showed a large standard deviation at all temperatures and this was attributed to large individual-to-individual variations in hematocrit. Turtles heat faster than they cool, regardless of whether tests are performed at temperatures above or below the range of thermal preference. The effect of temperature dependence of blood viscosity on heating and cooling rates is demonstrated.

Importance of Plasmonic Heating on Visible Light Driven Photocatalysis of Gold Nanoparticle Decorated Zinc Oxide Nanorods

PubMed Central

Bora, Tanujjal; Zoepfl, David; Dutta, Joydeep

2016-01-01

Herein we explore the role of localized plasmonic heat generated by resonantly excited gold (Au) NPs on visible light driven photocatalysis process. Au NPs are deposited on the surface of vertically aligned zinc oxide nanorods (ZnO NRs). The localized heat generated by Au NPs under 532 nm continuous laser excitation (SPR excitation) was experimentally probed using Raman spectroscopy by following the phonon modes of ZnO. Under the resonant excitation the temperature at the surface of the Au-ZnO NRs reaches up to about 300 °C, resulting in almost 6 times higher apparent quantum yield (AQY) for photocatalytic degradation of methylene blue (MB) compared to the bare ZnO NRs. Under solar light irradiation the Au-ZnO NRs demonstrated visible light photocatalytic activity twice that of what was achieved with bare ZnO NRs, while significantly reduced the activation energy required for the photocatalytic reactions allowing the reactions to occur at a faster rate. PMID:27242172

Velocity and temperature field characteristics of water and air during natural convection heating in cans.

PubMed

Erdogdu, Ferruh; Tutar, Mustafa

2011-01-01

Presence of headspace during canning is required since an adequate amount allows forming vacuum during the process. Sealing technology may not totally eliminate all entrapped gases, and headspace might affect heat transfer. Not much attention has been given to solve this problem in computational studies, and cans, for example, were mostly assumed to be fully filled with product. Therefore, the objective of this study was to determine velocity and temperature evolution of water and air in cans during heating to evaluate the relevance of headspace in the transport mechanism. For this purpose, canned water samples with a certain headspace were used, and required governing continuity, energy, and momentum equations were solved using a finite volume approach coupled with a volume of fluid element model. Simulation results correlated well with experimental results validating faster heating effects of headspace rather than insulation effects as reported in the literature. The organized velocity motions along the air-water interface were also shown. Practical Application: Canning is a universal and economic method for processing of food products, and presence of adequate headspace is required to form vacuum during sealing of the cans. Since sealing technology may not totally eliminate the entrapped gases, mainly air, headspace might affect heating rates in cans. This study demonstrated the increased heating rates in the presence of headspace in contrast with some studies in the literature. By applying the effect of headspace, required processing time for thermally processed foods can be reduced leading to more rapid processes and lower energy consumptions.

Aquatic training in MS: neurotherapeutic impact upon quality of life

PubMed Central

Frohman, Ashley N; Okuda, Darin T; Beh, Shin; Treadaway, Katherine; Mooi, Caroline; Davis, Scott L; Shah, Anjali; Frohman, Teresa C; Frohman, Elliot M

2015-01-01

Three fundamental principals associated with aquatic therapy differentiate it with respect to exercise on land, and in air. These are buoyancy (reduction in weight of the body within the buoyant medium of water), viscosity (a “drag force” is generated when moving within water, when compared with the same movement in air), and the thermodynamic aspect of water exercise, during which the heat capacity of water is about 1000 times greater than that of an equivalent amount of air; equating to a heat transfer from the body into water at a rate 25 times faster than that of air. Aquatic conditioning, can improve neurologic functioning, with dividends favorably impacting activities of daily living, health maintenance, safety, and ultimately quality of life. Here, we review the application of aquatic exercise training in MS patients. PMID:26339680

Computational studies of the glass-forming ability of model bulk metallic glasses

NASA Astrophysics Data System (ADS)

Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

2013-09-01

Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate Rc below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing Rc, and thus good glass-formers possess small values of Rc. We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change Rc significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ˜1011 K/s, which is several orders of magnitude higher than Rc for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

Relationship between dynamic infrared thermal images and blood perfusion rate of the tongue in anaemia patients

NASA Astrophysics Data System (ADS)

Xie, Haiwei; Zhang, Yan

2018-03-01

The relationship between dynamic infrared (IR) thermal images and blood perfusion rate of the tongues of anaemia patients was investigated. Blood perfusion rates at multiple locations on the tongues of 62 anaemia patients and 70 control subjects were measured. For both groups of subjects, dynamic IR thermal images were also recorded within 16 s after the mouth opened. The results showed that the blood perfusion rates at different sites (apex, middle, left side and right side) on the tongues in anaemia patients (3.49, 3.71, 3.85 and 3.77 kg/s m-3) were significantly lower than those at the corresponding sites in control subjects (4.45, 4.66, 4.81 and 4.70 kg/s m-3). After the mouth opened, the tongue temperature decreased more rapidly in anaemia patients than in control subjects. To analyse the heat transfer mechanism, a transient heat transfer model of the tongue was developed. The tongue temperatures in anaemia patients and control subjects were calculated using this model and compared to the tongue temperatures measured by the IR thermal imager. The relationship between the tongue surface temperature and the tongue blood perfusion rate was analysed. The simulation results indicated that the low blood perfusion rate and the correlated changes in anaemia patients can cause faster temperature decreases of the tongue surface.

Cold basal conditions during surges control flow of fringing Arctic ice caps in Greenland

NASA Astrophysics Data System (ADS)

Cook, Samuel; Christoffersen, Poul; Todd, Joe; Palmer, Steven

2017-04-01

Fringing ice caps separated from larger ice sheets are rarely studied, yet they are an important part of earth's cryosphere, which has become the largest source of global sea-level rise. Understanding marginal ice caps is crucial for being able to predict sea-level change as they are responsible for up to 20% of Greenland's mass loss for 2003-2008. Studies of fringing ice caps can furthermore provide useful insights into processes operating on glaciers that surge. Surging has been the focus of much recent glaciological work, especially with reference to thermal evolution of polythermal glaciers in High Mountain Asia and the High Arctic. This has shown that the classic divide between hydrologically-controlled surges ('hard-bed') in Alaska and thermally-regulated ('soft-bed') surges elsewhere is less stark than previously assumed. Studying marginal ice caps can therefore be valuable in several ways. The largest fringing ice cap in Greenland is Flade Isblink. Previous work has established that this ice cap is showing a range of dynamic behaviour, including subglacial lake drainage and varied patterns of mass-balance change. In particular, a substantial surge, assumed to be caused by a version of the thermally-regulated mechanism, occurred between 1996 and 2000, making the ice cap a useful case study for investigating this process. Here we investigate the surge on Flade Isblink using the open-source, Full-Stokes model Elmer/Ice to invert for basal conditions and englacial temperatures using the adjoint method. We specifically study steady-state conditions representative of the active surge phase in 2000, and the subsequent quiescent phase, using patterns of surface velocity observed in 2000, 2005, 2008 and 2015. Under constant geometry, temperature and geothermal heat, it is shown that surging increases basal freezing rates by over 60% across an area that is twice as large as the area over which the bed freezes in the quiescent phase. The process responsible for this is the conductive heat loss, which increases faster than frictional heat is produced. When the bed becomes weaker, basal conditions become colder despite faster basal sliding, resulting in steep basal ice temperature gradients, which transfer heat effectively from the bed into the ice. In contrast, we find the increase in frictional heat to be insufficient, because weaker basal conditions offset the effect of faster basal sliding. Hence, frictional heat cannot provide enough extra melting to maintain surge conditions. We hypothesise that this heat transfer mechanism terminates surges on Flade Isblink, irrespective of any thinning that would also occur. The latter is not included in our model, but is required in the classic soft-bed surge model. In the quiescent phase, lower temperature gradients reduce the conductive heat loss, while a stronger bed produces more frictional heat, favouring basal melting and a warm bed, which ultimately create the weak basal conditions that result in yet another surge, regardless of any change in ice thickness. Our results indicate that soft-bed surges may occur even if the surge-related change in glacier geometry is modest, making surging glaciers of this type similar to ice streams that stagnate and reactivate periodically.

Tear-Film Evaporation Rate from Simultaneous Ocular-Surface Temperature and Tear-Breakup Area.

PubMed

Dursch, Thomas J; Li, Wing; Taraz, Baseem; Lin, Meng C; Radke, Clayton J

2018-01-01

A corneal heat-transfer model is presented to quantify simultaneous measurements of fluorescein tear-breakup area (TBA) and ocular-surface temperature (OST). By accounting for disruption of the tear-film lipid layer (TFLL), we report evaporation rates through lipid-covered tear. The modified heat-transfer model provides new insights into evaporative dry eye. A quantitative analysis is presented to assess human aqueous tear evaporation rate (TER) through intact TFLLs from simultaneous in vivo measurement of time-dependent infrared OST and fluorescein TBA. We interpret simultaneous OST and TBA measurements using an extended heat-transfer model. We hypothesize that TBAs are ineffectively insulated by the TFLL and therefore exhibit higher TER than does that for a well-insulting TFLL-covered tear. As time proceeds, TBAs increase in number and size, thereby increasing the cornea area-averaged TER and decreasing OST. Tear-breakup areas were assessed from image analysis of fluorescein tear-film-breakup video recordings and are included in the heat-transfer description of OST. Model-predicted OSTs agree well with clinical experiments. Percent reductions in TER of lipid-covered tear range from 50 to 95% of that for pure water, in good agreement with literature. The physical picture of noninsulating or ruptured TFLL spots followed by enhanced evaporation from underlying cooler tear-film ruptures is consistent with the evaporative-driven mechanism for local tear rupture. A quantitative analysis is presented of in vivo TER from simultaneous clinical measurement of transient OST and TBA. The new heat-transfer model accounts for increased TER through expanding TBAs. Tear evaporation rate varies strongly across the cornea because lipid is effectively missing over tear-rupture troughs. The result is local faster evaporation compared with nonruptured, thick lipid-covered tear. Evaporative-driven tear-film ruptures deepen to a thickness where fluorescein quenching commences and local salinity rises to uncomfortable levels. Mitigation of tear-film rupture may therefore reduce dry eye-related symptoms.

Effect of pasteurization on the protein composition and oxidative stability of beer during storage.

PubMed

Lund, Marianne N; Hoff, Signe; Berner, Torben S; Lametsch, René; Andersen, Mogens L

2012-12-19

The impacts of pasteurization of a lager beer on protein composition and the oxidative stability were studied during storage at 22 °C for 426 days in the dark. Pasteurization clearly improved the oxidative stability of beer determined by ESR spectroscopy, whereas it had a minor negative effect on the volatile profile by increasing volatile compounds that is generally associated with heat treatment and a loss of fruity ester aroma. A faster rate of radical formation in unpasteurized beer was consistent with a faster consumption of sulfite. Beer proteins in the unpasteurized beer were more degraded, most likely due to proteolytic enzyme activity of yeast remnants and more precipitation of proteins was also observed. The differences in soluble protein content and composition are suggested to result in differences in the contents of prooxidative metals as a consequence of the proteins ability to bind metals. This also contributes to the differences in oxidative stabilities of the beers.

Factors controlling crystallization of miserite glass-ceramic.

PubMed

Muhammed, Fenik K; Moorehead, Robert; van Noort, Richard; Pollington, Sarah

2015-12-01

The purpose of this study was to investigate a range of variables affecting the synthesis of a miserite glass-ceramic (GC). Miserite glass was synthesized by the melt quench technique. The crystallization kinetics of the glass were determined using Differential Thermal Analysis (DTA). The glasses were ground with dry ball-milling and then sieved to different particle sizes prior to sintering. These particle sizes were submitted to heat treatment regimes in a high temperature furnace to form the GC. The crystal phases of the GC were analyzed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to examine the microstructure of the cerammed glass. XRD analysis confirmed that the predominant crystalline phase of the GC was miserite along with a minor crystalline phase of cristobalite only when the particle size is <20 μm and the heat treatment at 1000°C was carried out for 4h and slowly cooled at the furnace rate. For larger particle sizes and faster cooling rates, a pseudowollastonite crystalline phase was produced. Short sintering times produced either a pseudowollastonite or xonotolite crystalline phase. The current study has shown that particle size and heat treatment schedules are major factors in controlling the synthesis of miserite GC. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Hydrogen-bond memory and water-skin supersolidity resolving the Mpemba paradox.

PubMed

Zhang, Xi; Huang, Yongli; Ma, Zengsheng; Zhou, Yichun; Zhou, Ji; Zheng, Weitao; Jiang, Qing; Sun, Chang Q

2014-11-14

The Mpemba paradox, that is, hotter water freezes faster than colder water, has baffled thinkers like Francis Bacon, René Descartes, and Aristotle since B.C. 350. However, a commonly accepted understanding or theoretical reproduction of this effect remains challenging. Numerical reproduction of observations, shown herewith, confirms that water skin supersolidity [Zhang et al., Phys. Chem. Chem. Phys., DOI: ] enhances the local thermal diffusivity favoring heat flowing outwardly in the liquid path. Analysis of experimental database reveals that the hydrogen bond (O:H-O) possesses memory to emit energy at a rate depending on its initial storage. Unlike other usual materials that lengthen and soften all bonds when they absorb thermal energy, water performs abnormally under heating to lengthen the O:H nonbond and shorten the H-O covalent bond through inter-oxygen Coulomb coupling [Sun et al., J. Phys. Chem. Lett., 2013, 4, 3238]. Cooling does the opposite to release energy, like releasing a coupled pair of bungees, at a rate of history dependence. Being sensitive to the source volume, skin radiation, and the drain temperature, the Mpemba effect proceeds only in the strictly non-adiabatic 'source-path-drain' cycling system for the heat "emission-conduction-dissipation" dynamics with a relaxation time that drops exponentially with the rise of the initial temperature of the liquid source.

Dynamic Infrared Thermography Study of Blood Flow Relative to Lower Limp Position

NASA Astrophysics Data System (ADS)

Stathopoulos, I.; Skouroliakou, K.; Michail, C.; Valais, I.

2015-09-01

Thermography is an established method for studying skin temperature distribution. Temperature distribution on body surface is influenced by a variety of physiological mechanisms and has been proven a reliable indicator of various physiological disorders. Blood flow is an important factor that influences body heat diffusion and skin temperature. In an attempt to validate and further elucidate thermal models characterizing the human skin, dynamic thermography of the lower limp in horizontal and vertical position was performed, using a FLIR T460 thermographic camera. Temporal variation of temperature was recorded on five distinct points of the limp. Specific points were initially cooled by the means of an ice cube and measurements of the skin temperature were obtained every 30 seconds as the skin temperature was locally reduced and afterwards restored at its initial value. The return to thermal balance followed roughly the same pattern for all points of measurement, although the heating rate was faster when the foot was in horizontal position. Thermal balance was achieved faster at the spots that were positioned on a vein passage. Our results confirm the influence of blood flow on the thermal regulation of the skin. Spots located over veins exhibit different thermal behaviour due to thermal convection through blood flow. Changing the position of the foot from vertical to horizontal, effectively affects blood perfusion as in the vertical position blood circulation is opposed by gravity.

Role of Rayleigh numbers on characteristics of double diffusive salt fingers

NASA Astrophysics Data System (ADS)

Rehman, F.; Singh, O. P.

2018-05-01

Double diffusion convection, driven by two constituents of the fluid with different molecular diffusivity, is widely applied in oceanography and large number of other fields like astrophysics, geology, chemistry and metallurgy. In case of ocean, heat (T) and salinity (S) are the two components with varying diffusivity, where heat diffuses hundred times faster than salt. Component (T) stabilizes the system whereas components (S) destabilizes the system with overall density remains stable and forms the rising and sinking fingers known as salt fingers. Recent observations suggest that salt finger characteristics such as growth rates, wavenumber, and fluxes are strongly depending on the Rayleigh numbers as major driving force. In this paper, we corroborate this observation with the help of experiments, numerical simulations and linear theory. An eigenvalue expression for growth rate is derived from the linearized governing equations with explicit dependence on Rayleigh numbers, density stability ratio, Prandtl number and diffusivity ratio. Expressions for fastest growing fingers are also derived as a function various non-dimensional parameter. The predicted results corroborate well with the data reported from the field measurements, experiments and numerical simulations.

Recovery benefits of using a heat and moisture exchange mask during sprint exercise in cold temperatures.

PubMed

Seifert, John G; Frost, Jeremy; St Cyr, John A

2017-01-01

Breathing cold air can lead to bronchoconstriction and peripheral vasoconstriction, both of which could impact muscular performance by affecting metabolic demands during exercise. Successful solutions dealing with these physiological changes during exercise in the cold has been lacking; therefore, we investigated the influence of a heat and moisture exchange mask during exercise in the cold. There were three trial arms within this study: wearing the heat and moisture exchange mask during the rest periods in the cold, no-mask application during the rest periods in the cold, and a trial at room temperature (22°C). Eight subjects cycled in four 35 kJ sprint sessions with each session separated by 20 min rest period. Workload was 4% of body mass. Mean sprint times were faster with heat and moisture exchange mask and room temperature trial than cold, no-mask trial (133.8 ± 8.6, 134.9 ± 8.8, and 138.0 ± 8.4 s (p = 0.001)). Systolic blood pressure and mean arterial pressure were greater during the cold trial with no mask (15% and 13%, respectively), and heart rate was 10 bpm less during the third rest or recovery period during cold, no mask compared to the heat and moisture exchange mask and room temperature trials. Subjects demonstrated significant decreases in vital capacity and peak expiratory flow rate during the cold with no mask applied during the rest periods. These negative responses to cold exposure were alleviated by the use of a heat and moisture exchange mask worn during the rest intervals by minimizing cold-induced temperature stress on the respiratory system with subsequent maintenance of cardiovascular function.

Toward transient finite element simulation of thermal deformation of machine tools in real-time

NASA Astrophysics Data System (ADS)

Naumann, Andreas; Ruprecht, Daniel; Wensch, Joerg

2018-01-01

Finite element models without simplifying assumptions can accurately describe the spatial and temporal distribution of heat in machine tools as well as the resulting deformation. In principle, this allows to correct for displacements of the Tool Centre Point and enables high precision manufacturing. However, the computational cost of FE models and restriction to generic algorithms in commercial tools like ANSYS prevents their operational use since simulations have to run faster than real-time. For the case where heat diffusion is slow compared to machine movement, we introduce a tailored implicit-explicit multi-rate time stepping method of higher order based on spectral deferred corrections. Using the open-source FEM library DUNE, we show that fully coupled simulations of the temperature field are possible in real-time for a machine consisting of a stock sliding up and down on rails attached to a stand.

Collective effects and dynamics of non-adiabatic flame balls

NASA Astrophysics Data System (ADS)

D'Angelo, Yves; Joulin, Guy

2001-03-01

The dynamics of a homogeneous, polydisperse collection of non-adiabatic flame balls (FBs) is investigated by analytical/numerical means. A strongly temperature-dependent Arrhenius reaction rate is assumed, along with a light enough reactant characterized by a markedly less than unity Lewis number (Le). Combining activation-energy asymptotics with a mean-field type of treatment, the analysis yields a nonlinear integro-differential evolution equation (EE) for the FB population. The EE accounts for heat losses inside each FB and unsteadiness around it, as well as for its interactions with the entire FB population, namely mutual heating and faster (Le<1) consumption of the reactant pool. The initial FB number density and size distribution enter the EE explicitly. The latter is studied analytically at early times, then for small total FB number densities; it is subsequently solved numerically, yielding the whole population evolution and its lifetime. Generalizations and open questions relating to `spotty' turbulent combustion are finally evoked.

Development of high performance hybrid rocket fuels

NASA Astrophysics Data System (ADS)

Zaseck, Christopher R.

In this document I discuss paraffin fuel combustion and investigate the effects of additives on paraffin entrainment and regression. In general, hybrid rockets offer an economical and safe alternative to standard liquid and solid rockets. However, slow polymeric fuel regression and low combustion efficiency have limited the commercial use of hybrid rockets. Paraffin is a fast burning fuel that has received significant attention in the 2000's and 2010's as a replacement for standard fuels. Paraffin regresses three to four times faster than polymeric fuels due to the entrainment of a surface melt layer. However, further regression rate enhancement over the base paraffin fuel is necessary for widespread hybrid rocket adoption. I use a small scale opposed flow burner to investigate the effect of additives on the combustion of paraffin. Standard additives such as aluminum combust above the flame zone where sufficient oxidizer levels are present. As a result no heat is generated below the flame itself. In small scale opposed burner experiments the effect of limited heat feedback is apparent. Aluminum in particular does not improve the regression of paraffin in the opposed burner. The lack of heat feedback from additive combustion limits the applicability of the opposed burner. In turn, the results obtained in the opposed burner with metal additive loaded hybrid fuels do not match results from hybrid rocket experiments. In addition, nano-scale aluminum increases melt layer viscosity and greatly slows the regression of paraffin in the opposed flow burner. However, the reactive additives improve the regression rate of paraffin in the opposed burner where standard metals do not. At 5 wt.% mechanically activated titanium and carbon (Ti-C) improves the regression rate of paraffin by 47% in the opposed burner. The mechanically activated Ti C likely reacts in or near the melt layer and provides heat feedback below the flame region that results in faster opposed burner regression. In order to examine paraffin/additive combustion in a motor environment, I conducted experiments on well characterized aluminum based additives. In particular, I investigate the influence of aluminum, unpassivated aluminum, milled aluminum/polytetrafluoroethylene (PTFE), and aluminum hydride on the performance of paraffin fuels for hybrid rocket propulsion. I use an optically accessible combustor to examine the performance of the fuel mixtures in terms of characteristic velocity efficiency and regression rate. Each combustor test consumes a 12.7 cm long, 1.9 cm diameter fuel strand under 160 kg/m 2s of oxygen at up to 1.4 MPa. The experimental results indicate that the addition of 5 wt.% 30 mum or 80 nm aluminum to paraffin increases the regression rate by approximately 15% compared to neat paraffin grains. At higher aluminum concentrations and nano-scale particles sizes, the increased melt layer viscosity causes slower regression. Alane and Al/PTFE at 12.5 wt.% increase the regression of paraffin by 21% and 32% respectively. Finally, an aging study indicates that paraffin can protect air and moisture sensitive particles from oxidation. The opposed burner and aluminum/paraffin hybrid rocket experiments show that additives can alter bulk fuel properties, such as viscosity, that regulate entrainment. The general effect of melt layer properties on the entrainment and regression rate of paraffin is not well understood. Improved understanding of how solid additives affect the properties and regression of paraffin is essential to maximize performance. In this document I investigate the effect of melt layer properties on paraffin regression using inert additives. Tests are performed in the optical cylindrical combustor at ˜1 MPa under a gaseous oxygen mass flux of ˜160 kg/m2s. The experiments indicate that the regression rate is proportional to mu0.08rho 0.38kappa0.82. In addition, I explore how to predict fuel viscosity, thermal conductivity, and density prior to testing. Mechanically activated Ti-C and Al/PTFE are examined in the optical combustor. I examine the effect of the reactivity by altering the mill time for the Ti-C and Al/PTFE particles. Mechanical activation of both Ti-C and Al/PTFE improve the regression rate of paraffin more than the unmilled additives. At 12.5 wt.% Al/PTFE milled for 40 minutes regresses 12% faster than the unmilled fuel. Similarly, at 12.5 wt.% 7.5 minute milled Ti C regresses 7% faster than unmilled Ti-C. The reactive particles increase heat transfer to the fuel surface and improve regression. The composition of the combustion products are examined using a particle catcher system in conjunction with visible light and electron microscopy. The exhaust products indicate that the mechanical activation of the Al/PTFE particles cause microexplosions that reduce exhaust particle size. However, the composition of the mechanically activated Al/PTFE products do not indicate more complete combustion. In addition, the mechanically activated and unmilled Ti-C showed no difference in exhaust products.

Baroclinic instability in the interiors of the giant planets: A cooling history of Uranus?

NASA Technical Reports Server (NTRS)

Holme, Richard; Ingersoll, Andrew P.

1994-01-01

We propose a quasigeostrophic, baroclinic model for heat transport within the interior of a stably stratified Jovian planet, based on motion in thin cylindrical annuli. Density decreases from the center outward and is zero at the surface of the planet. In the homogeneous case (no core), we find instability for the poles hotter than the equator, but not for the reverse. If the motion is bounded by an impenetrable core, instability occurs for both cases. Much of the behavior can be explained by analogy to conventional baroclinic instability theory. Motivated by our results, we explore a possible connection between the highly inclined rotation axis of Uranus and its anomalously low surface heat flux. We assume that the planets formed hot. Our conjecture is that heat was efficiently convected outwards by baroclinic instability in Uranus (with the poles hotter than the equator), but not in the other three Jovian planets. The surface temperature was higher for the stably stratified case (Uranus), leading to a higher rate of infrared emission and faster cooling. Therefore, we propose that Uranus lost its internal heat sooner than Neptune because baroclinic motions, permitted by its inclination to the sun, were able to extract its internal heat while the surface was still warm.

A comparison of microwave versus direct solar heating for lunar brick production

NASA Technical Reports Server (NTRS)

Yankee, S. J.; Strenski, D. G.; Pletka, B. J.; Patil, D. S.; Mutsuddy, B. C.

1990-01-01

Two processing techniques considered suitable for producing bricks from lunar regolith are examined: direct solar heating and microwave heating. An analysis was performed to compare the two processes in terms of the amount of power and time required to fabricate bricks of various sizes. Microwave heating was shown to be significantly faster than solar heating for rapid production of realistic-size bricks. However, the relative simplicity of the solar collector(s) used for the solar furnace compared to the equipment necessary for microwave generation may present an economic tradeoff.

High methane natural gas/air explosion characteristics in confined vessel.

PubMed

Tang, Chenglong; Zhang, Shuang; Si, Zhanbo; Huang, Zuohua; Zhang, Kongming; Jin, Zebing

2014-08-15

The explosion characteristics of high methane fraction natural gas were investigated in a constant volume combustion vessel at different initial conditions. Results show that with the increase of initial pressure, the peak explosion pressure, the maximum rate of pressure rise increase due to a higher amount (mass) of flammable mixture, which delivers an increased amount of heat. The increased total flame duration and flame development time result as a consequence of the higher amount of flammable mixture. With the increase of the initial temperature, the peak explosion pressures decrease, but the pressure increase during combustion is accelerated, which indicates a faster flame speed and heat release rate. The maximum value of the explosion pressure, the maximum rate of pressure rise, the minimum total combustion duration and the minimum flame development time is observed when the equivalence ratio of the mixture is 1.1. Additionally, for higher methane fraction natural gas, the explosion pressure and the maximum rate of pressure rise are slightly decreased, while the combustion duration is postponed. The combustion phasing is empirically correlated with the experimental parameters with good fitting performance. Furthermore, the addition of dilute gas significantly reduces the explosion pressure, the maximum rate of pressure rise and postpones the flame development and this flame retarding effect of carbon dioxide is stronger than that of nitrogen. Copyright © 2014 Elsevier B.V. All rights reserved.

Influence of heat and shear induced protein aggregation on the in vitro digestion rate of whey proteins.

PubMed

Singh, Tanoj K; Øiseth, Sofia K; Lundin, Leif; Day, Li

2014-11-01

Protein intake is essential for growth and repair of body cells, the normal functioning of muscles, and health related immune functions. Most food proteins are consumed after undergoing various degrees of processing. Changes in protein structure and assembly as a result of processing impact the digestibility of proteins. Research in understanding to what extent the protein structure impacts the rate of proteolysis under human physiological conditions has gained considerable interest. In this work, four whey protein gels were prepared using heat processing at two different pH values, 6.8 and 4.6, with and without applied shear. The gels showed different protein network microstructures due to heat induced unfolding (at pH 6.8) or lack of unfolding, thus resulting in fine stranded protein networks. When shear was applied during heating, particulate protein networks were formed. The differences in the gel microstructures resulted in considerable differences in their rheological properties. An in vitro gastric and intestinal model was used to investigate the resulting effects of these different gel structures on whey protein digestion. In addition, the rate of digestion was monitored by taking samples at various time points throughout the in vitro digestion process. The peptides in the digesta were profiled using SDS-polyacrylamide gel electrophoresis, reversed-phase-HPLC and LC-MS. Under simulated gastric conditions, whey proteins in structured gels were hydrolysed faster than native proteins in solution. The rate of peptides released during in vitro digestion differed depending on the structure of the gels and extent of protein aggregation. The outcomes of this work highlighted that changes in the network structure of the protein can influence the rate and pattern of its proteolysis under gastrointestinal conditions. Such knowledge could assist the food industry in designing novel food formulations to control the digestion kinetics and the release of biologically active peptides for desired health outcome.

Study on heat transfer coefficients during cooling of PET bottles for food beverages

NASA Astrophysics Data System (ADS)

Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco

2016-08-01

The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.

Methane hydrate synthesis from ice: Influence of pressurization and ethanol on optimizing formation rates and hydrate yield

USGS Publications Warehouse

Chen, Po-Chun.; Huang, Wuu-Liang; Stern, Laura A.

2010-01-01

Polycrystalline methane gas hydrate (MGH) was synthesized using an ice-seeding method to investigate the influence of pressurization and ethanol on the hydrate formation rate and gas yield of the resulting samples. When the reactor is pressurized with CH4 gas without external heating, methane hydrate can be formed from ice grains with yields up to 25% under otherwise static conditions. The rapid temperature rise caused by pressurization partially melts the granular ice, which reacts with methane to form hydrate rinds around the ice grains. The heat generated by the exothermic reaction of methane hydrate formation buffers the sample temperature near the melting point of ice for enough time to allow for continuous hydrate growth at high rates. Surprisingly, faster rates and higher yields of methane hydrate were found in runs with lower initial temperatures, slower rates of pressurization, higher porosity of the granular ice samples, or mixtures with sediments. The addition of ethanol also dramatically enhanced the formation of polycrystalline MGH. This study demonstrates that polycrystalline MGH with varied physical properties suitable for different laboratory tests can be manufactured by controlling synthesis procedures or parameters. Subsequent dissociation experiments using a gas collection apparatus and flowmeter confirmed high methane saturation (CH 4·2O, with n = 5.82 ± 0.03) in the MGH. Dissociation rates of the various samples synthesized at diverse conditions may be fitted to different rate laws, including zero and first order.

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

Takahashi, Masayuki, E-mail: m.takahashi@al.t.u-tokyo.ac.jp; Ohnishi, Naofumi

A filamentary plasma is reproduced based on a fully kinetic model of electron and ion transports coupled with electromagnetic wave propagation. The discharge plasma transits from discrete to diffusive patterns at a 110-GHz breakdown, with decrease in the ambient pressure, because of the rapid electron diffusion that occurs during an increase in the propagation speed of the ionization front. A discrete plasma is obtained at low pressures when a low-frequency microwave is irradiated because the ionization process becomes more dominant than the electron diffusion, when the electrons are effectively heated by the low-frequency microwave. The propagation speed of the plasmamore » increases with decrease in the incident microwave frequency because of the higher ionization frequency and faster plasma diffusion resulting from the increase in the energy-absorption rate. An external magnetic field is applied to the breakdown volume, which induces plasma filamentation at lower pressures because the electron diffusion is suppressed by the magnetic field. The thrust performance of a microwave rocket is improved by the magnetic fields corresponding to the electron cyclotron resonance (ECR) and its higher-harmonic heating, because slower propagation of the ionization front and larger energy-absorption rates are obtained at lower pressures. It would be advantageous if the fundamental mode of ECR heating is coupled with a lower frequency microwave instead of combining the higher-harmonic ECR heating with the higher frequency microwave. This can improve the thrust performance with smaller magnetic fields even if the propagation speed increases because of the decrease in the incident microwave frequency.« less

Observations of elevated Atlantic water heat fluxes at the boundary of the Arctic Basin.

NASA Astrophysics Data System (ADS)

Lincoln, Benjamin; Rippeth, Tom; Lenn, Yueng; Bacon, Sheldon

2014-05-01

The well documented decline in Arctic Sea Ice cover over the past 30 years has outpaced global models as warming in Polar Regions occurs faster than the global mean. The thermohaline circulation brings warm water from the Atlantic Ocean into the Arctic basin. This Atlantic water circulates at depth and contains sufficient heat to melt the sea ice cover several times over. Recent studies have shown that this Atlantic water has warmed and shoaled over recent decades (Polyakov et al, 2010). The stability of the upper Arctic Ocean has also changed, with stratification reduced in the Eurasian basin but increased in the Canada basin. Along with an increased availability of heat the reduction in sea ice cover allows greater potential for wind to input energy to the ocean to vertically mix heat to the surface and further melt sea ice. Direct measurements of vertical mixing rates across the Arctic are essential to understanding the changes in this supply of heat from below, but are scarce due to the challenges of making such measurements in the harsh Arctic environment. We present measurements of turbulent kinetic energy dissipation (ɛ) within the top 500 m of the water column using microstructure measurements made both in open water and under ice during 4 different years. Mean rates of dissipation in the Atlantic water thermocline are calculated and compared for data collected in the European, Siberian and Canadian Arctic, including measurements from 2007 and 2012 when record minimum sea ice extents were recorded. Diapycnal heat fluxes from the mean Atlantic water dissipation rates were calculated from these mean dissipation rates and show significant variation across the Arctic Basin. Profiles in the deep basin generally revealed very low rates of dissipation were low ɛ<10-9Wkg-1 and as such heat fluxes of AW were correspondingly low Fh=0.1-0.5Wm-2. However double diffusive staircases were present in all such casts and so vertical transfer of heat may be increased by diffusive fluxes. Dissipation rates were enhanced by up to 3 orders of magnitude at the boundaries of the Arctic basin with the highest rates North of Svalbard and decreasing ɛ anticlockwise around the basin with low ɛ in the Canada basin. Enhanced heat fluxes at the boundaries ranged from 10-100 Wm-2 north of Svalbard decreasing to 2-5 Wm-2 along the Laptev shelf slope and less than 0.5 Wm-2 along the East Siberian slope and Lomonosov ridge. In the Canada basin heat fluxes at the boundary were less than 0.2 Wm-2. --- Arctic Ocean Warming Contributes to Reduced Polar Ice Cap Igor V. Polyakov, Leonid A. Timokhov, Vladimir A. Alexeev, Sheldon Bacon, Igor A. Dmitrenko, Louis Fortier, et al. in Journal of Physical Oceanography (2010)

Improved Method for Determining the Heat Capacity of Metals

ERIC Educational Resources Information Center

Barth, Roger; Moran, Michael J.

2014-01-01

An improved procedure for laboratory determination of the heat capacities of metals is described. The temperature of cold water is continuously recorded with a computer-interfaced temperature probe and the room temperature metal is added. The method is more accurate and faster than previous methods. It allows students to get accurate measurements…

Steam generator design for solar towers using solar salt as heat transfer fluid

NASA Astrophysics Data System (ADS)

González-Gómez, Pedro Ángel; Petrakopoulou, Fontina; Briongos, Javier Villa; Santana, Domingo

2017-06-01

Since the operation of a concentrating solar power plant depends on the intermittent character of solar energy, the steam generator is subject to daily start-ups, stops and load variations. Faster start-up and load changes increase the plant flexibility and the daily energy production. However, it involves high thermal stresses on thick-walled components. Continuous operational conditions may eventually lead to a material failure. For these reasons, it is important to evaluate the transient behavior of the proposed designs in order to assure the reliability. The aim of this work is to analyze different steam generator designs for solar power tower plants using molten salt as heat transfer fluid. A conceptual steam generator design is proposed and associated heat transfer areas and steam drum size are calculated. Then, dynamic models for the main parts of the steam generator are developed to represent its transient performance. A temperature change rate that ensures safe hot start-up conditions is studied for the molten salt. The thermal stress evolution on the steam drum is calculated as key component of the steam generator.

Effect of Heat Input on the Tensile Damage Evolution in Pulsed Laser Welded Ti6Al4V Titanium Sheets

NASA Astrophysics Data System (ADS)

Liu, Jing; Gao, Xiaolong; Zhang, Jianxun

2016-11-01

The present paper is focused on studying the effect of heat input on the tensile damage evolution of pulsed Nd:YAG laser welding of Ti6Al4V alloy under monotonic loading. To analyze the reasons that the tensile fracture site of the pulsed-laser-welded Ti6Al4V sheet joints changes with the heat input under monotonic loading, the microstructure of the sample with different nominal strain values was investigated by in situ observation. Experiment results show that the tensile ductility and fatigue life of welded joints with low heat input are higher than that of welded joints with high heat input. Under tensile loads, the critical engineering strain for crack initiation is much lower in the welded joint with high heat input than in the welded joints with low and medium heat input. And the microstructural damage accumulation is much faster in the fusion zone than in the base metal for the welded joints with high input, whereas the microstructural damage accumulation is much faster in the base metal than in the fusion zone for the welded joints with low input. Consequently, the welded joints fractured in the fusion zone for the welds with high heat input, whereas the welded joints ruptured in the base metal for the welds with low heat input. It is proved that the fine grain microstructure produced by low heat input can improve the critical nominal strain for crack initiation and the resistance ability of microstructural damage.

Different Temperature and Cooling Patterns at the Blunt and Sharp Egg Poles Reflect the Arrangement of Eggs in an Avian Clutch

PubMed Central

Šálek, Miroslav E.; Zárybnická, Markéta

2015-01-01

Incubation is an energetically demanding process during which birds apply heat to their eggs to ensure embryonic development. Parent behaviours such as egg turning and exchanging the outer and central eggs in the nest cup affect the amount of heat lost to the environment from individual eggs. Little is known, however, about whether and how egg surface temperature and cooling rates vary among the different areas of an egg and how the arrangement of eggs within the clutch influences heat loss. We performed laboratory (using Japanese quail eggs) and field (with northern lapwing eggs) experiments using infrared imaging to assess the temperature and cooling patterns of heated eggs and clutches. We found that (i) the sharp poles of individual quail eggs warmed to a higher egg surface temperature than did the blunt poles, resulting in faster cooling at the sharp poles compared to the blunt poles; (ii) both quail and lapwing clutches with the sharp poles oriented towards the clutch centre (arranged clutches) maintained higher temperatures over the central part of the clutch than occurred in those clutches where most of the sharp egg poles were oriented towards the exterior (scattered clutches); and (iii) the arranged clutches of both quail and lapwing showed slower cooling rates at both the inner and outer clutch positions than did the respective parts of scattered clutches. Our results demonstrate that egg surface temperature and cooling rates differ between the sharp and blunt poles of the egg and that the orientation of individual eggs within the nest cup can significantly affect cooling of the clutch as a whole. We suggest that birds can arrange their eggs within the nest cup to optimise thermoregulation of the clutch. PMID:25658846

Different temperature and cooling patterns at the blunt and sharp egg poles reflect the arrangement of eggs in an avian clutch.

PubMed

Šálek, Miroslav E; Zárybnická, Markéta

2015-01-01

Incubation is an energetically demanding process during which birds apply heat to their eggs to ensure embryonic development. Parent behaviours such as egg turning and exchanging the outer and central eggs in the nest cup affect the amount of heat lost to the environment from individual eggs. Little is known, however, about whether and how egg surface temperature and cooling rates vary among the different areas of an egg and how the arrangement of eggs within the clutch influences heat loss. We performed laboratory (using Japanese quail eggs) and field (with northern lapwing eggs) experiments using infrared imaging to assess the temperature and cooling patterns of heated eggs and clutches. We found that (i) the sharp poles of individual quail eggs warmed to a higher egg surface temperature than did the blunt poles, resulting in faster cooling at the sharp poles compared to the blunt poles; (ii) both quail and lapwing clutches with the sharp poles oriented towards the clutch centre (arranged clutches) maintained higher temperatures over the central part of the clutch than occurred in those clutches where most of the sharp egg poles were oriented towards the exterior (scattered clutches); and (iii) the arranged clutches of both quail and lapwing showed slower cooling rates at both the inner and outer clutch positions than did the respective parts of scattered clutches. Our results demonstrate that egg surface temperature and cooling rates differ between the sharp and blunt poles of the egg and that the orientation of individual eggs within the nest cup can significantly affect cooling of the clutch as a whole. We suggest that birds can arrange their eggs within the nest cup to optimise thermoregulation of the clutch.

Atomic-level study of a thickness-dependent phase change in gold thin films heated by an ultrafast laser.

PubMed

Gan, Yong; Shi, Jixiang; Jiang, Shan

2012-08-20

An ultrafast laser-induced phase change in gold thin films with different thicknesses has been simulated by the method of coupling the two-temperature model and the molecular dynamics, including transient optical properties. Numerical results show that the decrease of film thickness leads to faster melting in the early nonequilibrium time and a larger melting depth. Moreover, earlier occurrence and a higher rate of resolidification are observed for the thicker film. Further analysis reveals that the mechanism for the thickness-dependent phase change in the films is the fast electron thermal conduction in the nonequilibrium state.

A comparison of direct heating during radiofrequency and microwave ablation in ex vivo liver

PubMed Central

Andreano, Anita; Brace, Christopher L

2012-01-01

Purpose To determine the magnitude and spatial distribution of temperature elevations when using 480 kHz RF and 2.45 GHz microwave energy in ex vivo liver models. Materials and Methods A total of sixty heating cycles (20 s at 90 W) were performed in normal, RF ablated and microwave ablated liver tissues (n=10 RF and n=10 microwave in each tissue type). Heating cycles were performed using a 480 kHz generator and 3 cm cooled-tip electrode (RF) or a 2.45 GHz generator and 14-gauge monopole (microwave) and designed to isolate direct heating from each energy type. Tissue temperatures were measured using fiberoptic thermosensors 5, 10 and 15 mm radially from the ablation applicator at the depth of maximal heating. Power delivered, sensor location, heating rates and maximal temperatures were compared using mixed effects regression models. Results No significant differences were noted in mean power delivered or thermosensor locations between RF and microwave heating groups (P>0.05). Microwaves produced significantly more rapid heating than RF at 5, 10 and 15mm in normal tissue (3.0 vs. 0.73, 0.85 vs. 0.21 and 0.17 vs. 0.09 °C/s; P<.05); and at 5 and 10mm in ablated tissues (2.3 ± 1.4 vs. 0.7 ± 0.3, 0.5 ± 0.3 vs. 0.2 ± 0.0 C/s, P<.05). The radial depth of heating was approximately 5mm greater for microwaves than RF. Conclusions Direct heating obtained with 2.45 GHz microwave energy using a single needle-like applicator is faster and covers a larger volume of tissue than 480 kHz RF energy. Keywords: microwave ablation, direct heating, thermal ablation PMID:22572764

Effect of additional heat treatment of 2024-T3 on the growth of fatigue crack in air and in vacuum

NASA Technical Reports Server (NTRS)

Louwaard, E. P.

1986-01-01

In order to determine the influence of ductility on the fatigue crack growth rate of aluminum alloys, fatigue tests were carried out on central notched specimens of 2024-T3 and 2024-T8 sheet material. The 2024-T8 material was obtained by an additional heat treatment applied on 2024-T3 (18 hours at 192 C), which increased the static yield strength from 43.6 to 48.9 kgf/sq mm. A change in the ultimate strength was not observed. Fatigue tests were carried out on both materials in humid air and in high vacuum. According to a new crack propagation model, crack extension is supported to be caused by a slip-related process and debonding triggered by the environment. This model predicts an effect of the ductility on the crack growth rate which should be smaller in vacuum than in humid air; however, this was not confirmed. In humid air the crack-growth rate in 2024-T8 was about 2 times faster than in 2024-T3, while in vacuum the ratio was about 2.5. Crack closure measurements gave no indications that crack closure played a significant role in both materials. Some speculative explanations are briefly discussed.

The importance of microclimate variation in determining size, growth and survival of avian offspring: experimental evidence from a cavity nesting passerine.

PubMed

Dawson, Russell D; Lawrie, Cheyenne C; O'Brien, Erin L

2005-07-01

Organisms are expected to balance energy allocation in such a way that fitness is maximized. While much research has focussed on allocation strategies of reproducing parents, in particular birds, relatively little attention has been paid to how nestlings allocate energy while in the nest. Nestling birds are faced with a trade-off between devoting energy to growth or to thermoregulation, and in altricial species it is likely that the thermal environment of the nest site influences the nature of this trade-off. Here, we experimentally investigate how altering the microclimate of nests affects the growth, size and survival, as well as cell-mediated immune (CMI) response, of nestling tree swallows (Tachycineta bicolor) in a temperate environment. We place air-activated heating pads in nests of swallows when young were between 4 days and 16 days of age, and compared performance of offspring to control nests. Our manipulation raised temperatures of heated nests by approximately 5 degrees C compared to control nests. Offspring in heated nests had enhanced survival while in the nest, and we also found that they were heavier and had longer ninth primary feathers at 16 days of age. In addition, heating nest boxes resulted in significantly faster growth of primaries, and there was a trend for growth rates of mass to also be higher in heated nests. There were no significant differences between heated and control nests in growth rate or size of tarsus at age 16 days, and we speculate that this lack of response to elevated nest temperatures may be due to growth of skeletal structures being limited by other factors such as calcium availability. We also found no difference between heated and control nests in CMI response. Nonetheless, our results show overall that increasing temperatures of nests has significant benefits that enhance the fitness of offspring. As provisioning rates to offspring did not differ between heated and control nests, we suspect that the beneficial effects of heating were not the consequence of changes in parental behaviour. Our results provide insight into factors, other than food supply, that have important consequences in determining reproductive success of birds breeding in temperate environments.

Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion

PubMed Central

Lee, Sabrina S. M.; de Boef Miara, Maria; Arnold, Allison S.; Biewener, Andrew A.; Wakeling, James M.

2013-01-01

SUMMARY Animals modulate the power output needed for different locomotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate motor units must be recruited. Faster motor units have faster activation–deactivation rates than slower motor units, and they contract at higher strain rates; therefore, recruitment of faster motor units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified motor unit recruitment patterns in the gastrocnemii muscles of goats and examined whether faster motor units are recruited when locomotor speed is increased. The study also examined whether locomotor tasks that elicit faster (or slower) motor units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster motor units were recruited as goats increased their locomotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that recruitment of the different motor unit types depended, in part, on characteristics of the task. For the locomotor tasks and muscles analyzed here, recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks. PMID:22972893

Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion.

PubMed

Lee, Sabrina S M; de Boef Miara, Maria; Arnold, Allison S; Biewener, Andrew A; Wakeling, James M

2013-01-15

Animals modulate the power output needed for different locomotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate motor units must be recruited. Faster motor units have faster activation-deactivation rates than slower motor units, and they contract at higher strain rates; therefore, recruitment of faster motor units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified motor unit recruitment patterns in the gastrocnemii muscles of goats and examined whether faster motor units are recruited when locomotor speed is increased. The study also examined whether locomotor tasks that elicit faster (or slower) motor units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster motor units were recruited as goats increased their locomotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that recruitment of the different motor unit types depended, in part, on characteristics of the task. For the locomotor tasks and muscles analyzed here, recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks.

Mass and heat transfer in crushed oil shale

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

Carley, J.F.; Ott, L.L.; Swecker, J.L.

1995-03-01

Studies of heat and mass transfer in packed beds, which disagree substantially in their findings, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse irregular shapes and sizes. The authors, in 349 runs, measured mass-transfer rates front naphthalene particles buried in packed beds by passing through air at room temperature. An exact catalog between convection of heat and mass makes it possible to infer heat-transfer coefficients from measured mass-transfer coefficients and fluid properties. Some beds consisted of spheres, naphthalene and inert, of the same, contrasting or distributed sizes. Inmore » some runs, naphthalene spheres were buried in beds of crushed shale, some in narrow screen ranges and others with a wide size range. In others, naphthalene lozenges of different shapes were buried in beds of crushed shale in various bed axis orientations. This technique permits calculation of the mass-transfer coefficient for each active particle in the bed rather than, as in most past studies, for the bed as a whole. The data are analyzed by the traditional correlation of Colburn j{sub D} vs. Reynolds number and by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: local Reynolds number should be based on the active-particle size, not the average for the whole bed; differences between shallow and deep beds are not appreciable; mass transfer is 26% faster for spheres and lozenges buried in shale than in all-sphere beds; orientation of lozenges in shale beds has little or no effect on mass-transfer rate; and for mass or heat transfer in shale beds, log(j{center_dot}{epsilon}) = {minus}0.0747 - 0.6344 log N{sub Re} + 0. 0592 log {sup 2} N{sub Re}.« less

Supercritical methanol for polyethylene terephthalate depolymerization: Observation using simulator

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

Genta, Minoru; Iwaya, Tomoko; Sasaki, Mitsuru

2007-07-01

To apply PET depolymerization in supercritical methanol to commercial recycling, the benefits of supercritical methanol usage in PET depolymerization was investigated from the viewpoint of the reaction rate and energy demands. PET was depolymerized in a batch reactor at 573 K in supercritical methanol under 14.7 MPa and in vapor methanol under 0.98 MPa in our previous work. The main products of both reactions were the PET monomers of dimethyl terephthalate (DMT) and ethylene glycol (EG). The rate of PET depolymerization in supercritical methanol was faster than that of PET depolymerization in vapor methanol. This indicates supercritical fluid is beneficialmore » in reducing reaction time without the use of a catalyst. We depicted the simple process flow of PET depolymerization in supercritical methanol and in vapor methanol, and by simulation evaluated the total heat demand of each process. In this simulation, bis-hydroxyethyl terephthalate (BHET) was used as a model component of PET. The total heat demand of PET depolymerization in supercritical methanol was 2.35 x 10{sup 6} kJ/kmol Produced-DMT. That of PET depolymerization in vapor methanol was 2.84 x 10{sup 6} kJ/kmol Produced-DMT. The smaller total heat demand of PET depolymerization in supercritical methanol clearly reveals the advantage of using supercritical fluid in terms of energy savings.« less

A Comparison of Mixed-Method Cooling Interventions on Preloaded Running Performance in the Heat.

PubMed

Stevens, Christopher J; Bennett, Kyle J M; Sculley, Dean V; Callister, Robin; Taylor, Lee; Dascombe, Ben J

2017-03-01

Stevens, CJ, Bennett, KJM, Sculley, DV, Callister, R, Taylor, L, and Dascombe, BJ. A comparison of mixed-method cooling interventions on preloaded running performance in the heat. J Strength Cond Res 31(3): 620-629, 2017-The purpose of this investigation was to assess the effect of combining practical methods to cool the body on endurance running performance and physiology in the heat. Eleven trained male runners completed 4 randomized, preloaded running time trials (20 minutes at 70% V[Combining Dot Above]O2max and a 3 km time trial) on a nonmotorized treadmill in the heat (33° C). Trials consisted of precooling by combined cold-water immersion and ice slurry ingestion (PRE), midcooling by combined facial water spray and menthol mouth rinse (MID), a combination of all methods (ALL), and control (CON). Performance time was significantly faster in MID (13.7 ± 1.2 minutes; p < 0.01) and ALL (13.7 ± 1.4 minutes; p = 0.04) but not PRE (13.9 ± 1.4 minutes; p = 0.24) when compared with CON (14.2 ± 1.2 minutes). Precooling significantly reduced rectal temperature (initially by 0.5 ± 0.2° C), mean skin temperature, heart rate and sweat rate, and increased iEMG activity, whereas midcooling significantly increased expired air volume and respiratory exchange ratio compared with control. Significant decreases in forehead temperature, thermal sensation, and postexercise blood prolactin concentration were observed in all conditions compared with control. Performance was improved with midcooling, whereas precooling had little or no influence. Midcooling may have improved performance through an attenuated inhibitory psychophysiological and endocrine response to the heat.

Improvement of water transport mechanisms during potato drying by applying ultrasound.

PubMed

Ozuna, César; Cárcel, Juan A; García-Pérez, José V; Mulet, Antonio

2011-11-01

The drying rate of vegetables is limited by internal moisture diffusion and convective transport mechanisms. The increase of drying air temperature leads to faster water mobility; however, it provokes quality loss in the product and presents a higher energy demand. Therefore, the search for new strategies to improve water mobility during convective drying constitutes a topic of relevant research. The aim of this work was to evaluate the use of power ultrasound to improve convective drying of potato and quantify the influence of the applied power in the water transport mechanisms. Drying kinetics of potato cubes were increased by the ultrasonic application. The influence of power ultrasound was dependent on the ultrasonic power (from 0 to 37 kW m(-3) ), the higher the applied power, the faster the drying kinetic. The diffusion model considering external resistance to mass transfer provided a good fit of drying kinetics. From modelling, it was observed a proportional and significant (P < 0.05) influence of the applied ultrasonic power on the identified kinetic parameters: effective moisture diffusivity and mass transfer coefficient. The ultrasonic application during drying represents an interesting alternative to traditional convective drying by shortening drying time, which may involve an energy saving concerning industrial applications. In addition, the ultrasonic effect in the water transport is based on mechanical phenomena with a low heating capacity, which is highly relevant for drying heat sensitive materials and also for obtaining high-quality dry products. Copyright © 2011 Society of Chemical Industry.

Mass and heat transfer in crushed oil shale

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

Carley, J.F.; Straub, J.S.; Ott, L.L.

1984-04-01

Heat and mass transfer between gases and oil-shale particles are both important for all proposed retorting processes. Past studies of transfer in packed beds, which have disagreed substantially in their results, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse shapes and widely ranging sizes. To resolve these questions, we have made 349 runs in which we measured mass-transfer rates from naphthalene particles of diverse shapes buried in packed beds through which air was passed at room temperature. This technique permits calculation of the mass-transfer coefficient for each activemore » particle in the bed rather than, as in most past studies, for the bed as a whole. The data were analyzed in two ways: (1) by the traditional correlation of Colburn j/sub D/ vs Reynolds number and (2) by multiple regression of the mass-transfer coefficient on air rate, traditional correlation of Colburn j/sub D/ vs Reynolds number and (3) by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: (1) local Reynolds number should be based on active particle size rather than average size for the bed; (2) no appreciable differences were seen between shallow beds and deep ones; (3) mass transfer was 26% faster for spheres and lozenges buried in shale than for all-sphere beds; (4) orientation of lozenges in shale beds has little effect on mass-transfer rate; (5) a useful summarizing equation for either mass or heat transfer in shale beds is log j.epsilon = -.0747 - .6344 log Re + .0592 log/sup 2/Re where j = either j/sub D/ or j/sub H/, the Chilton-Colburn j-factors for mass and heat transfer, Re = the Reynolds number defined for packed beds, and epsilon = the void fraction in the bed. 12 references, 15 figures.« less

Heart rate variability during exertional heat stress: effects of heat production and treatment.

PubMed

Flouris, Andreas D; Bravi, Andrea; Wright-Beatty, Heather E; Green, Geoffrey; Seely, Andrew J; Kenny, Glen P

2014-04-01

We assessed the efficacy of different treatments (i.e., treatment with ice water immersion vs. natural recovery) and the effect of exercise intensities (i.e., low vs. high) for restoring heart rate variability (HRV) indices during recovery from exertional heat stress (EHS). Nine healthy adults (26 ± 3 years, 174.2 ± 3.8 cm, 74.6 ± 4.3 kg, 17.9 ± 2.8 % body fat, 57 ± 2 mL·kg·(-1) min(-1) peak oxygen uptake) completed four EHS sessions incorporating either walking (4.0-4.5 km·h(-1), 2 % incline) or jogging (~7.0 km·h(-1), 2 % incline) on a treadmill in a hot-dry environment (40 °C, 20-30 % relative humidity) while wearing a non-permeable rain poncho for a slow or fast rate of rectal temperature (T re) increase, respectively. Upon reaching a T re of 39.5 °C, participants recovered until T re returned to 38 °C either passively or with whole-body immersion in 2 °C water. A comprehensive panel of 93 HRV measures were computed from the time, frequency, time-frequency, scale-invariant, entropy and non-linear domains. Exertional heat stress significantly affected 60/93 HRV measures analysed. Analyses during recovery demonstrated that there were no significant differences between HRV measures that had been influenced by EHS at the end of passive recovery vs. whole-body cooling treatment (p > 0.05). Nevertheless, the cooling treatment required statistically significantly less time to reduce T re (p < 0.001). While EHS has a marked effect on autonomic nervous system modulation and whole-body immersion in 2 °C water results in faster cooling, there were no observed differences in restoration of autonomic heart rate modulation as measured by HRV indices with whole-body cold-water immersion compared to passive recovery in thermoneutral conditions.

Our Roads, A Large Thermoelectric Generator

NASA Astrophysics Data System (ADS)

Weiss, I.

2017-12-01

If asphalt can heat up from the solar radiation shining onto it directly, then it will be able to heat water in pipes within the pavement. The heat from the warm water can then be harvested into usable electrical energy, because heat energy can be transformed into electrical energy using the Seebeck Effect. The Seebeck Effect is when a temperature difference causes electrons to move away from the heat, creating an electrical charge. My experiment showed my research-based hypothesis correct. I hypothesized that if asphalt can heat up from the solar radiation shining onto it directly, then it would be able to warm a water system and usable energy could be harvested, because heat energy can be transformed into electrical energy. Asphalt pavement does not reflect the sunlight and hence heats up faster than a light surface that would reflect the sunlight. This means the asphalt absorbs the sunlight and gives off heat, which is wasted energy. By turning heat energy into electricity, cities can provide a source of clean, green energy and reduce their reliance on fossil fuels. The heat given off by asphalt increases the temperature of the air around, contributing to what is known as the urban heat island effect. This heating contributes to the formation of smog and ozone depletion. With the population still growing this would mean increasing city sizes, greater heat island effect and hence an increase in smog and ozone depletion. By harvesting the heat energy in the pavement through my setup, cities can not only create green energy but also reduce the heat radiated from pavement. Converting my system to a neighborhood street would produce higher output. My street measures 800 feet long by 35 feet wide. That gives us 28,000 square feet. At the rate of 5 volts per minute for a 2 square foot area, my street would be able to produce 70,000 volts per minute.

Study of parameters in precision optical glass molding

NASA Astrophysics Data System (ADS)

Ni, Ying; Wang, Qin-hua; Yu, Jing-chi

2010-10-01

Precision glass compression molding is an attractive approach to manufacture small precision optics in large volume over traditional manufacturing techniques because of its advantages such as lower cost, faster time to market and being environment friendly. In order to study the relationship between the surface figures of molded lenses and molding process parameters such as temperature, pressure, heating rate, cooling rate and so on, we present some glass compression molding experiments using same low Tg (transition temperature) glass material to produce two different kinds of aspheric lenses by different molding process parameters. Based on results from the experiments, we know the major factors influencing surface figure of molded lenses and the changing range of these parameters. From the knowledge we could easily catch proper molding parameters which are suitable for aspheric lenses with diameter from 10mm to 30mm.

Magnetic Reconnection in Strongly Magnetized Regions of the Low Solar Chromosphere

NASA Astrophysics Data System (ADS)

Ni, Lei; Lukin, Vyacheslav S.; Murphy, Nicholas A.; Lin, Jun

2018-01-01

Magnetic reconnection in strongly magnetized regions around the temperature minimum region of the low solar atmosphere is studied by employing MHD-based simulations of a partially ionized plasma within a reactive 2.5D multi-fluid model. It is shown that in the absence of magnetic nulls in a low β plasma, the ionized and neutral fluid flows are well-coupled throughout the reconnection region. However, non-equilibrium ionization–recombination dynamics play a critical role in determining the structure of the reconnection region, leading to much lower temperature increases and a faster magnetic reconnection rate as compared to simulations that assume plasma to be in ionization–recombination equilibrium. The rate of ionization of the neutral component of the plasma is always faster than recombination within the current sheet region even when the initial plasma β is as high as {β }0=1.46. When the reconnecting magnetic field is in excess of a kilogauss and the plasma β is lower than 0.0145, the initially weakly ionized plasmas can become fully ionized within the reconnection region and the current sheet can be strongly heated to above 2.5× {10}4 K, even as most of the collisionally dissipated magnetic energy is radiated away. The Hall effect increases the reconnection rate slightly, but in the absence of magnetic nulls it does not result in significant asymmetries or change the characteristics of the reconnection current sheet down to meter scales.

Effects of caffeine and menthol on cognition and mood during simulated firefighting in the heat.

PubMed

Zhang, Yang; Balilionis, Gytis; Casaru, Catalina; Geary, Colleen; Schumacker, Randall E; Neggers, Yasmin H; Curtner-Smith, Matthew D; Richardson, Mark T; Bishop, Phillip A; Green, James M

2014-05-01

This study examined the separate effects of caffeine and menthol on cognition and mood during simulated firefighting in the heat. Participants (N = 10) performed three trials in a counterbalanced order, either with 400 mg caffeine, menthol lozenges, or placebo. The simulated firefighting consisted of 2 bouts of 20-min treadmill exercise and one bout of 20-min stepping exercise in the heat with two brief 15-min rest periods between each exercise phase. Exercise induced significant dehydration (>3%) and elevated rectal temperature (>38.9 °C), for all three conditions. Neither caffeine nor menthol reduced perceived exertion compared to placebo (p > 0.05). Mood ratings (i.e., alertness, hedonic tone, tension) significantly deteriorated over time (p < 0.05), but there was no difference among the three conditions. Simple reaction time, short-term memory, and retrieval memory did not alter with treatments or repeated evaluations. Reaction accuracy from a math test remained unchanged throughout the experimental period; reaction time from the math test was significantly faster after exposure to the heat (p < 0.05). It is concluded that, exhaustive exercise in the heat severely impacted mood, but minimally impacted cognition. These treatments failed to show ergogenic benefits in a simulated firefighting paradigm in a hot environment. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Compressible Heating in the Condense Phase due to Pore Collapse in HMX

NASA Astrophysics Data System (ADS)

Zhang, Ju; Jackson, Thomas

Axisymmetric pore collapse in HMX is studied numerically by solving multi-phase reactive Euler equations. The generation of hot spots in the condense phase due to compressible heating is examined. The motivation is to improve the understanding of the role of embedded cavities in the initiation of reaction in explosives, and to investigate the effect of hot spots in the condense phase due to compressible heating alone, complementing previous study on hot spots due to the reaction in the gas phase and at the interface. It is found that the shock-cavity interaction results in pressures and thus temperatures that are substantially higher than the post-shock values in the condense phase. However, these hot spots in the condense phase due to compressible heating alone do not seem to be sufficiently hot to lead to ignition at shock pressures of 1-3 GPa. Thus, compressible heating in the condense phase may be excluded as a mechanism for initiation of explosives. It should be pointed out that the ignition threshold for the temperature, the so-called ``switch-on'' temperature, of hot spots depend on chemistry kinetics parameters. Switch-on temperature is lower for faster reaction rate. The current chemistry kinetics parameters are based on previous experimental work. This work was supported in part by the Defense Threat Reduction Agency and by the U.S. Department of Energy.

Rapid cooling rates at an active mid-ocean ridge from zircon thermochronology

USGS Publications Warehouse

Schmitt, Axel K.; Perfit, Michael R.; Rubin, Kenneth H.; Stockli, Daniel F.; Smith, Matthew C.; Cotsonika, Laurie A.; Zellmer, Georg F.; Ridley, W. Ian

2011-01-01

Oceanic spreading ridges are Earth's most productive crust generating environment, but mechanisms and rates of crustal accretion and heat loss are debated. Existing observations on cooling rates are ambiguous regarding the prevalence of conductive vs. convective cooling of lower oceanic crust. Here, we report the discovery and dating of zircon in mid-ocean ridge dacite lavas that constrain magmatic differentiation and cooling rates at an active spreading center. Dacitic lavas erupted on the southern Cleft segment of the Juan de Fuca ridge, an intermediate-rate spreading center, near the intersection with the Blanco transform fault. Their U–Th zircon crystallization ages (29.3-4.6+4.8 ka; 1δ standard error s.e.) overlap with the (U–Th)/He zircon eruption age (32.7 ± 1.6 ka) within uncertainty. Based on similar 238U-230Th disequilibria between southern Cleft dacite glass separates and young mid-ocean ridge basalt (MORB) erupted nearby, differentiation must have occurred rapidly, within ~ 10–20 ka at most. Ti-in-zircon thermometry indicates crystallization at 850–900 °C and pressures > 70–150 MPa are calculated from H2O solubility models. These time-temperature constraints translate into a magma cooling rate of ~ 2 × 10-2 °C/a. This rate is at least one order-of-magnitude faster than those calculated for zircon-bearing plutonic rocks from slow spreading ridges. Such short intervals for differentiation and cooling can only be resolved through uranium-series (238U–230Th) decay in young lavas, and are best explained by dissipating heat convectively at high crustal permeability.

International patent analysis of water source heat pump based on orbit database

NASA Astrophysics Data System (ADS)

Li, Na

2018-02-01

Using orbit database, this paper analysed the international patents of water source heat pump (WSHP) industry with patent analysis methods such as analysis of publication tendency, geographical distribution, technology leaders and top assignees. It is found that the beginning of the 21st century is a period of rapid growth of the patent application of WSHP. Germany and the United States had done researches and development of WSHP in an early time, but now Japan and China have become important countries of patent applications. China has been developing faster and faster in recent years, but the patents are concentrated in universities and urgent to be transferred. Through an objective analysis, this paper aims to provide appropriate decision references for the development of domestic WSHP industry.

Tail loss and thermoregulation in the common lizard Zootoca vivipara

NASA Astrophysics Data System (ADS)

Herczeg, Gábor; Kovács, Tibor; Tóth, Tamás; Török, János; Korsós, Zoltán; Merilä, Juha

2004-10-01

Tail autotomy in lizards is an adaptive strategy that has evolved to reduce the risk of predation. Since tail loss reduces body mass and moving ability—which in turn are expected to influence thermal balance—there is potential for a trade-off between tail autotomy and thermoregulation. To test this hypothesis, we studied a common lizard (Zootoca vivipara) population at high latitude, inhabiting a high-cost thermal environment. Z. vivipara is a small, non-territorial lizard known as a very accurate thermoregulator. We made two predictions: (1) the reduced body weight due to tail loss results in faster heating rate (a benefit), and (2) the reduction in locomotor ability after tail loss induces a shift to the use of thermally poorer microhabitats (a cost), thus decreasing the field body temperatures of active lizards. We did not find any effect of tail loss on heating rate in laboratory experiments conducted under different thermal conditions. Likewise, no significant relationship between tail condition and field body temperatures, or between tail condition and thermal microhabitat use, were detected. Thus, our results suggest that tail autotomy does not influence the accuracy of thermoregulation in small-bodied lizards.

The effect of skin reflectance on thermal traits in a small heliothermic ectotherm.

PubMed

Matthews, Genevieve; Goulet, Celine T; Delhey, Kaspar; Chapple, David G

2016-08-01

Variation in colour patterning is prevalent among and within species. A number of theories have been proposed in explaining its evolution. Because solar radiation interacts with the pigmentation of the integument causing light to either be reflected or absorbed into the body, thermoregulation has been considered to be a primary selective agent, particularly among ectotherms. Accordingly, the colour-mediated thermoregulatory hypothesis states that darker individuals will heat faster and reach higher thermal equilibria while paler individuals will have the opposite traits. It was further predicted that dark colouration would promote slower cooling rates and higher thermal performance temperatures. To test these hypotheses we quantified the reflectance, selected body temperatures, performance optima, as well as heating and cooling rates of an ectothermic vertebrate, Lampropholis delicata. Our results indicated that colour had no influence on thermal physiology, as all thermal traits were uncorrelated with reflectance. We suggest that crypsis may instead be the stronger selective agent as it may have a more direct impact on fitness. Our study has improved our knowledge of the functional differences among individuals with different colour patterns, and the evolutionary significance of morphological variation within species. Copyright © 2016 Elsevier Ltd. All rights reserved.

Tail loss and thermoregulation in the common lizard Zootoca vivipara.

PubMed

Herczeg, Gábor; Kovács, Tibor; Tóth, Tamás; Török, János; Korsós, Zoltán; Merilä, Juha

2004-10-01

Tail autotomy in lizards is an adaptive strategy that has evolved to reduce the risk of predation. Since tail loss reduces body mass and moving ability-which in turn are expected to influence thermal balance-there is potential for a trade-off between tail autotomy and thermoregulation. To test this hypothesis, we studied a common lizard (Zootoca vivipara) population at high latitude, inhabiting a high-cost thermal environment. Z. vivipara is a small, non-territorial lizard known as a very accurate thermoregulator. We made two predictions: (1) the reduced body weight due to tail loss results in faster heating rate (a benefit), and (2) the reduction in locomotor ability after tail loss induces a shift to the use of thermally poorer microhabitats (a cost), thus decreasing the field body temperatures of active lizards. We did not find any effect of tail loss on heating rate in laboratory experiments conducted under different thermal conditions. Likewise, no significant relationship between tail condition and field body temperatures, or between tail condition and thermal microhabitat use, were detected. Thus, our results suggest that tail autotomy does not influence the accuracy of thermoregulation in small-bodied lizards.

Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species

PubMed Central

Epifani, Mauro; Kaciulis, Saulius; Mezzi, Alessio; Altamura, Davide; Giannini, Cinzia; Díaz, Raül; Force, Carmen; Genç, Aziz; Arbiol, Jordi; Siciliano, Pietro; Comini, Elisabetta; Concina, Isabella

2017-01-01

SnO2 nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization techniques, it emerged that the as-prepared materials were constituted by cassiterite SnO2 nanocrystals with a surface modified by isolated V(IV) oxide species. After heat-treatment at 400 °C, the SnO2 nanocrystals were wrapped by layers composed of vanadium oxide (IV-V mixed oxidation state) and carbon residuals. After heating at 500 °C, only SnO2 cassiterite nanocrystals were obtained, with a mean size of 2.8 nm and wrapped by only V2O5-like species. The samples heat-treated at 500 °C were tested as RhB photodegradation catalysts. At 10−7 M concentration, all RhB was degraded within 1 h of reaction, at a much faster rate than all pure SnO2 materials reported until now. PMID:28300185

A study on post impingement effects of urea-water solution spray on the heated wall of automotive SCR systems

NASA Astrophysics Data System (ADS)

Shahariar, G. M. H.; Wardana, M. K. A.; Lim, O. T.

2018-04-01

The post impingement effects of urea-water solution spray on the heated wall of automotive SCR systems was numerically investigated in a constant volume chamber using STAR CCM+ CFD code. The turbulence flow was modelled by realizable k-ε two-layer model together with standard wall function and all y+ treatment was applied along with two-layer approach. The Eulerian-Lagrangian approach was used for the modelling of multi phase flow. Urea water solution (UWS) was injected onto the heated wall for the wall temperature of 338, 413, 473, 503 & 573 K. Spray development after impinging on the heated wall was visualized and measured. Droplet size distribution and droplet evaporation rates were also measured, which are vital parameters for the system performance but still not well researched. Specially developed user defined functions (UDF) are implemented to simulate the desired conditions and parameters. The investigation reveals that wall temperature has a great impact on spray development after impingement, droplet size distribution and evaporation. Increasing the wall temperature leads to longer spray front projection length, smaller droplet size and faster droplet evaporation which are preconditions for urea crystallization reduction. The numerical model and parameters are validated comparing with experimental data.

Subglacial volcanic activity above a lateral dyke path during the 2014-2015 Bárdarbunga-Holuhraun rifting episode, Iceland

NASA Astrophysics Data System (ADS)

Reynolds, Hannah I.; Gudmundsson, Magnús T.; Högnadóttir, Thórdís; Magnússon, Eyjólfur; Pálsson, Finnur

2017-06-01

The rifting episode associated with the Bárdarbunga-Holuhraun eruption in 2014-2015 included the first observations of major dyke propagation under ice. Three shallow ice depressions (ice cauldrons) with volumes ranging from 1 to 18 million m3 formed in Dyngjujökull glacier above the 48-km-long lateral path of the magma, at 4, 7 and 12 km from the northern glacier edge. Aircraft-based radar altimetry profiling was used to map the evolution of the cauldrons and construct a time series of the heat transfer rates. Out of the three scenarios explored: (1) onset or increase of hydrothermal activity, (2) convection within vertical fissures filled with water overlying intruded magma and (3) subglacial eruptions, the last option emerges as the only plausible mechanism to explain the rapid heat transfer observed in a location far from known geothermal areas. The thermal signals at two of the cauldrons are consistent with effusive subglacial eruptions. The formation of the northernmost cauldron was more rapid, indicating faster heat transfer rates. Radio-echo sounding data indicate that in contrast to the other two cauldrons, an intrusion of eruptive products occurred into the glacier, reaching 50-60 m above bedrock with the increased magma-ice contact explaining the more rapid heat transfer. We propose that the 2-m widening associated with graben formation increased the groundwater storage capacity of the bedrock, creating space for the meltwater to be stored, explaining the absence of meltwater pulses draining from Dyngjujökull.

Optical calorimetry in microfluidic droplets.

PubMed

Chamoun, Jacob; Pattekar, Ashish; Afshinmanesh, Farzaneh; Martini, Joerg; Recht, Michael I

2018-05-29

A novel microfluidic calorimeter that measures the enthalpy change of reactions occurring in 100 μm diameter aqueous droplets in fluoropolymer oil has been developed. The aqueous reactants flow into a microfluidic droplet generation chip in separate fluidic channels, limiting contact between the streams until immediately before they form the droplet. The diffusion-driven mixing of reactants is predominantly restricted to within the droplet. The temperature change in droplets due to the heat of reaction is measured optically by recording the reflectance spectra of encapsulated thermochromic liquid crystals (TLC) that are added to one of the reactant streams. As the droplets travel through the channel, the spectral characteristics of the TLC represent the internal temperature, allowing optical measurement with a precision of ≈6 mK. The microfluidic chip and all fluids are temperature controlled, and the reaction heat within droplets raises their temperature until thermal diffusion dissipates the heat into the surrounding oil and chip walls. Position resolved optical temperature measurement of the droplets allows calculation of the heat of reaction by analyzing the droplet temperature profile over time. Channel dimensions, droplet generation rate, droplet size, reactant stream flows and oil flow rate are carefully balanced to provide rapid diffusional mixing of reactants compared to thermal diffusion, while avoiding thermal "quenching" due to contact between the droplets and the chip walls. Compared to conventional microcalorimetry, which has been used in this work to provide reference measurements, this new continuous flow droplet calorimeter has the potential to perform titrations ≈1000-fold faster while using ≈400-fold less reactants per titration.

Mitigating Exertional Heat Illness in Military Personnel: The Science Behind a Rice-Based Electrolyte and Rehydration Drink.

PubMed

Moore, Brenda; O'Hara, Reginald

Exertional heat illness continues to be prevalent among members of active duty personnel, especially those in specific military occupational specialties such as loadmasters, flight crew, flight maintainers, and Special Operations Forces. Therefore, the primary objective of this article was to elucidate the various oral rehydration solutions (ORSs) on the market that are used to mitigate exertional heat illness (EHI) in military personnel, and to focus on the science behind a ricebased electrolyte drink, CeraSport®, currently used by US military personnel in mitigating EHI during sustained training operations in high-heat environments. A search of the literature (through March 2016) was performed using PubMed and ProQuest, in addition to searching bibliographies and text books. We reviewed 63 articles and three texts. Articles were limited to those published in English and to studies that used only carbohydrates (e.g., no amino acids) and drinks reported to be used by the military in field training and deployment. Heat illness is prevalent among military personnel operating in high-heat environments and a variety of ORSs and sports drinks are available to help mitigate this. However, CeraSport, compared with other ORSs and sports drinks, may offer benefits such as faster gastric emptying rates and improved absorption from the gastrointestinal tract, which can provide rapidly available carbohydrate substrates for energy needs, and increased water retention for maintenance of blood plasma volume. 2016.

The effect of cover use on plastic pyrolysis reactor heating process

NASA Astrophysics Data System (ADS)

Armadi, Benny H.; Rangkuti, Chalilullah; Fauzi, M. D.; Permatasari, R.

2017-03-01

Plastic pyrolysis process to produce liquid fuel is an endothermic process that uses heat from the combustion of fuel as heat source. The reactor used is usually a vertical cylindrical in shape, with LPG fuel combustion under the flat bottom of the reactor, and the combustion gases is dispersed into the surrounding environment, so that heat transferred to the plastic inside the reactor is not effective, causing high LPG consumption. In this study, the reactor is made of stainless steel plate, with a vertical cylindrical shape, with a basic cylindrical conical truncated by a pit pass hot flue gas in the middle that serves to deliver flue gas into the chimney. The contact area between the hot combusted LPG gases to the processed plastic inside the reactor becomes bigger and gets better heat transfer, and required less LPG consumption. For more effective heat transfer process, an outer cover of this reactor was made and the relatively hot combustion gases are used to heat the outside of the reactor by directing the flow of the flue gas from the chimney down along the outer wall of the reactor and out the bottom lid. This construction makes the heating process to be faster and the LPG fuel is used more efficiently. From the measurements, it was found to raise 1°C of temperature inside the covered reactor, the LPG consumed is 0.59 gram, and if the reactor cover is removed, the gas demand will rise nearly threefold to 1.43 grams. With this method, in addition to reducing the rate of heat loss will also help reduce LPG consumption significantly.

Effect of a Cooling Kit on Physiology and Performance Following Exercise in the Heat.

PubMed

Smith, Cody R; Butts, Cory L; Adams, J D; Tucker, Matthew A; Moyen, Nicole E; Ganio, Matthew S; McDermott, Brendon P

2017-06-12

Exercising in the heat leads to an increase in body temperature that can increase the risk of heat illness or cause detriments in exercise performance. To examine a phase change heat emergency kit (HEK) on thermoregulatory and perceptual responses, and subsequent exercise performance following exercise in the heat. Two randomized crossover trials which consisted of 30 minutes of exercise, 15 minutes of treatment (T 1 ), performance testing (5-10-5 pro-agility test, 1500 m run), and another 15 minutes of treatment (T 2 ) identical to T 1 . Outdoors in the heat (WBGT 31.5 ± 1.8°C, 59.0 ± 5.6% RH). Twenty-six (13 male, 13 female) individuals (20-27 y). Treatment was performed with HEK or without (CON) modality. Gastrointestinal temperature (T GI ), mean skin temperature (T SK ), thirst sensation, and muscle pain. Maximum T GI following exercise and performance was not different between trials (P > 0.05). Cooling rate was faster during T 1 CON (0.053 ± 0.049 °C/min) compared to HEK (0.043 ± 0.032°C/min; P = 0.01). T SK was lower in HEK during T 1 (P < 0.001) and T 2 (P = 0.050). T 2 thirst was lower in CON (P = 0.021). Muscle pain was lower in HEK in T 2 (P = 0.026). Performance was not altered (P > 0.05). HEK improved perception, but did not enhance cooling or performance following exercise in the heat. HEK is, therefore, not recommended to facilitate recovery, treat hyperthermia or improve performance.

Aluminum runway surface as possible aid to aircraft braking

NASA Technical Reports Server (NTRS)

Miller, C. D.; Pinkel, I. I.

1973-01-01

Several concepts are described for use singly or in combination to improve aircraft braking. All involve a thin layer of aluminum covering all or part of the runway. Advantage would derive from faster heat conduction from the tire-runway interface. Heating of tread surface with consequent softening and loss of friction coefficient should be reduced. Equations are developed indicating that at least 99 percent of friction heat should flow into the aluminum. Preliminary test results indicate a coefficient of sliding friction of 1.4, with predictably slight heating of tread. Elimination of conventional brakes is at least a remote possibility.

Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis

NASA Astrophysics Data System (ADS)

Tanabe, Katsuaki

2016-06-01

We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.

Magnetic nanoparticle hyperthermia as an adjuvant cancer therapy with chemotherapy

NASA Astrophysics Data System (ADS)

Petryk, Alicia Ailie

Magnetic nanoparticle hyperthermia (mNPH) is an emerging cancer therapy which has shown to be most effective when applied in the adjuvant setting with chemotherapy, radiation or surgery. Although mNPH employs heat as a primary therapeutic modality, conventional heat may not be the only cytotoxic effect. As such, my studies have focused on the mechanism and use of mNPH alone and in conjunction with cisplatinum chemotherapy in murine breast cancer cells and a related in vivo model. MNPH was compared to conventional microwave tumor heating, with results suggesting that mNPH (mNP directly injected into the tumor and immediately activated) and 915 MHz microwave hyperthermia, at the same thermal dose, result in similar tumor regrowth delay kinetics. However, mNPH shows significantly less peri-tumor normal tissue damage. MNPH combined with cisplatinum also demonstrated significant improvements in regrowth delay over either modality applied as a monotherapy. Additional studies demonstrated that a relatively short tumor incubation time prior to AMF exposure (less than 10 minutes) as compared to a 4-hour incubation time, resulted in faster heating rates, but similar regrowth delays when treated to the same thermal dose. The reduction of heating rate correlated well with the observed reduction in mNP concentration in the tumor observed with 4 hour incubation. The ability to effectively deliver cytotoxic mNPs to metastatic tumors is the hope and goal of systemic mNP therapy. However, delivering relevant levels of mNP is proving to be a formidable challenge. To address this issue, I assessed the ability of cisplatinum to simultaneously treat a tumor and improve the uptake of systemically delivered mNPs. Following a cisplatinum pretreatment, systemic mNPs uptake was increased by 3.1 X, in implanted murine breast tumors. Additional in vitro studies showed the necessity of a specific mNP/ Fe architecture and spatial relation for heat-based cytotoxicity in cultured cells.

Enceladus: three-act play and current state

NASA Astrophysics Data System (ADS)

Luan, J.; Goldreich, P.

2017-12-01

Eccentricity (e) growth as Enceladus migrates deeper into mean motion resonance with Dione results in increased tidal heating. As the bottom of the ice shell melts, the rate of tidal heating jumps and runaway melting ensues. At the end of run-away melting, the shell's thickness has fallen below the value at which the frequency of free libration equals the orbital mean motion and e has damped to well below its current value. Subsequently, both the shell thickness and e partake in a limit cycle. As e damps toward its minimum value, the shell's thickness asymptotically approaches its resonant value from below. After minimum e, the shell thickens quickly and e grows even faster. This cycle is likely to have been repeated multiple times in the past. Currently, e is much smaller than its equilibrium value corresponding to the shell thickness. Physical libration resonance resolves this mystery, it ensures that the low-e and medium-thickness state is present for most of the time between consecutive limit cycles. It is a robust scenario that avoids fine tuning or extreme parameter choice, and naturally produces episodic stages of high heating, consistent with softening of topographical features on Enceladus.

Three-dimensional Monte Carlo calculation of atmospheric thermal heating rates

NASA Astrophysics Data System (ADS)

Klinger, Carolin; Mayer, Bernhard

2014-09-01

We present a fast Monte Carlo method for thermal heating and cooling rates in three-dimensional atmospheres. These heating/cooling rates are relevant particularly in broken cloud fields. We compare forward and backward photon tracing methods and present new variance reduction methods to speed up the calculations. For this application it turns out that backward tracing is in most cases superior to forward tracing. Since heating rates may be either calculated as the difference between emitted and absorbed power per volume or alternatively from the divergence of the net flux, both approaches have been tested. We found that the absorption/emission method is superior (with respect to computational time for a given uncertainty) if the optical thickness of the grid box under consideration is smaller than about 5 while the net flux divergence may be considerably faster for larger optical thickness. In particular, we describe the following three backward tracing methods: the first and most simple method (EMABS) is based on a random emission of photons in the grid box of interest and a simple backward tracing. Since only those photons which cross the grid box boundaries contribute to the heating rate, this approach behaves poorly for large optical thicknesses which are common in the thermal spectral range. For this reason, the second method (EMABS_OPT) uses a variance reduction technique to improve the distribution of the photons in a way that more photons are started close to the grid box edges and thus contribute to the result which reduces the uncertainty. The third method (DENET) uses the flux divergence approach where - in backward Monte Carlo - all photons contribute to the result, but in particular for small optical thickness the noise becomes large. The three methods have been implemented in MYSTIC (Monte Carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres). All methods are shown to agree within the photon noise with each other and with a discrete ordinate code for a one-dimensional case. Finally a hybrid method is built using a combination of EMABS_OPT and DENET, and application examples are shown. It should be noted that for this application, only little improvement is gained by EMABS_OPT compared to EMABS.

Cybersecurity: The heat is on.

PubMed

Morrissey, John

2015-10-01

Breaches of confidential patient information are proliferating and the culprits are more sophisticated and sinister than ever. Hospitals and health systems are using smarter and faster tactics to stay one step ahead of the bad guys.

Rapid Acclimation Ability Mediated by Transcriptome Changes in Reef-Building Corals.

PubMed

Bay, Rachael A; Palumbi, Stephen R

2015-05-15

Population response to environmental variation involves adaptation, acclimation, or both. For long-lived organisms, acclimation likely generates a faster response but is only effective if the rates and limits of acclimation match the dynamics of local environmental variation. In coral reef habitats, heat stress from extreme ocean warming can occur over several weeks, resulting in symbiont expulsion and widespread coral death. However, transcriptome regulation during short-term acclimation is not well understood. We examined acclimation during a 11-day experiment in the coral Acropora nana. We acclimated colonies to three regimes: ambient temperature (29 °C), increased stable temperature (31 °C), and variable temperature (29-33 °C), mimicking local heat stress conditions. Within 7-11 days, individuals acclimated to increased temperatures had higher tolerance to acute heat stress. Despite physiological changes, no gene expression changes occurred during acclimation before acute heat stress. However, we found strikingly different transcriptional responses to heat stress between acclimation treatments across 893 contigs. Across these contigs, corals acclimated to higher temperatures (31 °C or 29-33 °C) exhibited a muted stress response--the magnitude of expression change before and after heat stress was less than in 29 °C acclimated corals. Our results show that corals have a rapid phase of acclimation that substantially increases their heat resilience within 7 days and that alters their transcriptional response to heat stress. This is in addition to a previously observed longer term response, distinguishable by its shift in baseline expression, under nonstressful conditions. Such rapid acclimation may provide some protection for this species of coral against slow onset of warming ocean temperatures. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Rapid Acclimation Ability Mediated by Transcriptome Changes in Reef-Building Corals

PubMed Central

Bay, Rachael A.; Palumbi, Stephen R.

2015-01-01

Population response to environmental variation involves adaptation, acclimation, or both. For long-lived organisms, acclimation likely generates a faster response but is only effective if the rates and limits of acclimation match the dynamics of local environmental variation. In coral reef habitats, heat stress from extreme ocean warming can occur over several weeks, resulting in symbiont expulsion and widespread coral death. However, transcriptome regulation during short-term acclimation is not well understood. We examined acclimation during a 11-day experiment in the coral Acropora nana. We acclimated colonies to three regimes: ambient temperature (29 °C), increased stable temperature (31 °C), and variable temperature (29–33 °C), mimicking local heat stress conditions. Within 7–11 days, individuals acclimated to increased temperatures had higher tolerance to acute heat stress. Despite physiological changes, no gene expression changes occurred during acclimation before acute heat stress. However, we found strikingly different transcriptional responses to heat stress between acclimation treatments across 893 contigs. Across these contigs, corals acclimated to higher temperatures (31 °C or 29–33 °C) exhibited a muted stress response—the magnitude of expression change before and after heat stress was less than in 29 °C acclimated corals. Our results show that corals have a rapid phase of acclimation that substantially increases their heat resilience within 7 days and that alters their transcriptional response to heat stress. This is in addition to a previously observed longer term response, distinguishable by its shift in baseline expression, under nonstressful conditions. Such rapid acclimation may provide some protection for this species of coral against slow onset of warming ocean temperatures. PMID:25979751

Combinations of glycerol percent, glycerol equilibration time, and thawing rate upon freezability of bull spermatozoa in plastic straws.

PubMed

Wiggin, H B; Almquist, J O

1975-03-01

Twelve ejaculates were used in a central composite experiment to test 15 combinations of glycerol (7, 9, 11, 13, or 15%), glycerol equilibration times (1, 2, 4, 8, or 16 h) and thawing rates (water at 35 C for 15 s, 50 C for 13 s, 65 C for 11 s, 80 C for 9 s, or 95 C for 7 s). Semen was diluted in heated skim milk-glycerol, packaged in .3-ml. Continental U.S. straws and frozen in liquid nitrogen vapor. Based on post-thaw progressive sperm motility after storage at -196 C for 9 to 11 days, estimated optima from multiple regression were 10.7% for glycerol, 2.0 h for glycerol equilibration time, and 76 C for thawing bath temperature. Only the linear effect for each variable was significant. Much faster thawing rates and shorter glycerol equilibration times than those for freezing bull spermatozoa in glass ampules should be used for maximum post-thaw sperm motility in straws.

Faster-X evolution: Theory and evidence from Drosophila.

PubMed

Charlesworth, Brian; Campos, José L; Jackson, Benjamin C

2018-02-12

A faster rate of adaptive evolution of X-linked genes compared with autosomal genes can be caused by the fixation of recessive or partially recessive advantageous mutations, due to the full expression of X-linked mutations in hemizygous males. Other processes, including recombination rate and mutation rate differences between X chromosomes and autosomes, may also cause faster evolution of X-linked genes. We review population genetics theory concerning the expected relative values of variability and rates of evolution of X-linked and autosomal DNA sequences. The theoretical predictions are compared with data from population genomic studies of several species of Drosophila. We conclude that there is evidence for adaptive faster-X evolution of several classes of functionally significant nucleotides. We also find evidence for potential differences in mutation rates between X-linked and autosomal genes, due to differences in mutational bias towards GC to AT mutations. Many aspects of the data are consistent with the male hemizygosity model, although not all possible confounding factors can be excluded. © 2018 John Wiley & Sons Ltd.

Method and apparatus for duct sealing using a clog-resistant insertable injector

DOEpatents

Wang, Duo; Modera, Mark P.

2007-01-02

A clog-resistant injector spray nozzle allows relatively unobtrusive insertion through a small access aperture into existing ductwork in occupied buildings for atomized particulate sealing of a ductwork. The spray nozzle comprises an easily cleaned and easily replaced straight liquid tube whose liquid contents are principally propelled by a heated propellant gas, such as heated air. Heat transfer is minimized from the heated propellant gas to the liquid tube until they both exit the injector, thereby greatly reducing the likelihood of nozzle clogging. A method of duct sealing using particles driven by heated propellant gas is described, whereby duct-sealing operations become both faster, and commercially practicable in inhabited commercial and residential buildings.

Mathematical Description of Complex Chemical Kinetics and Application to CFD Modeling Codes

NASA Technical Reports Server (NTRS)

Bittker, D. A.

1993-01-01

A major effort in combustion research at the present time is devoted to the theoretical modeling of practical combustion systems. These include turbojet and ramjet air-breathing engines as well as ground-based gas-turbine power generating systems. The ability to use computational modeling extensively in designing these products not only saves time and money, but also helps designers meet the quite rigorous environmental standards that have been imposed on all combustion devices. The goal is to combine the very complex solution of the Navier-Stokes flow equations with realistic turbulence and heat-release models into a single computer code. Such a computational fluid-dynamic (CFD) code simulates the coupling of fluid mechanics with the chemistry of combustion to describe the practical devices. This paper will focus on the task of developing a simplified chemical model which can predict realistic heat-release rates as well as species composition profiles, and is also computationally rapid. We first discuss the mathematical techniques used to describe a complex, multistep fuel oxidation chemical reaction and develop a detailed mechanism for the process. We then show how this mechanism may be reduced and simplified to give an approximate model which adequately predicts heat release rates and a limited number of species composition profiles, but is computationally much faster than the original one. Only such a model can be incorporated into a CFD code without adding significantly to long computation times. Finally, we present some of the recent advances in the development of these simplified chemical mechanisms.

Mathematical description of complex chemical kinetics and application to CFD modeling codes

NASA Technical Reports Server (NTRS)

Bittker, D. A.

1993-01-01

A major effort in combustion research at the present time is devoted to the theoretical modeling of practical combustion systems. These include turbojet and ramjet air-breathing engines as well as ground-based gas-turbine power generating systems. The ability to use computational modeling extensively in designing these products not only saves time and money, but also helps designers meet the quite rigorous environmental standards that have been imposed on all combustion devices. The goal is to combine the very complex solution of the Navier-Stokes flow equations with realistic turbulence and heat-release models into a single computer code. Such a computational fluid-dynamic (CFD) code simulates the coupling of fluid mechanics with the chemistry of combustion to describe the practical devices. This paper will focus on the task of developing a simplified chemical model which can predict realistic heat-release rates as well as species composition profiles, and is also computationally rapid. We first discuss the mathematical techniques used to describe a complex, multistep fuel oxidation chemical reaction and develop a detailed mechanism for the process. We then show how this mechanism may be reduced and simplified to give an approximate model which adequately predicts heat release rates and a limited number of species composition profiles, but is computationally much faster than the original one. Only such a model can be incorporated into a CFD code without adding significantly to long computation times. Finally, we present some of the recent advances in the development of these simplified chemical mechanisms.

Effects of a Circulating-water Garment and Forced-air Warming on Body Heat Content and Core Temperature

PubMed Central

Taguchi, Akiko; Ratnaraj, Jebadurai; Kabon, Barbara; Sharma, Neeru; Lenhardt, Rainer; Sessler, Daniel I.

2005-01-01

Background: Forced-air warming is sometimes unable to maintain perioperative normothermia. We therefore compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods: Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34°C. The volunteers were subsequently warmed for 2.5 hours with either a circulating-water garment or forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and “deep” arm and foot thermometers. Results: Heat production (≈ 60 kcal/h) and loss (≈45 kcal/h) were similar with each treatment before warming. The increase in heat transfer across anterior portions of the skin surface was similar with each warming system (≈65 kcal/h). Forced-air warming had no effect on posterior heat transfer whereas circulating-water transferred 21 ± 9 kcal/h through the posterior skin surface after a half hour of warming. Over 2.5 h, circulating-water thus increased body heat content 56% more than forced air. Core temperatures thus increased faster than with circulating water than forced air, especially during the first hour, with the result that core temperature was 1.1 ± 0.7°C greater after 2.5 h (P < 0.001). Peripheral tissue heat content increased twice as much as core heat content with each device, but the core-to-peripheral tissue temperature gradient remained positive throughout the study. Conclusions: The circulating-water system transferred more heat than forced air, with the difference resulting largely from posterior heating. Circulating water rewarmed patients 0.4°C/h faster than forced air. A substantial peripheral-to-core tissue-temperature gradient with each device indicated that peripheral tissues insulated the core, thus slowing heat transfer. PMID:15114200

Increased Coal Plant Flexibility Can Improve Renewables Integration |

Science.gov Websites

practices that enable lower turndowns, faster starts and stops, and faster ramping between load set-points faster ramp rates and faster and less expensive starts. Flexible Load - Demand Response Resources Demand response (DR) is a load management practice of deliberately reducing or adding load to balance the system

Arctic tundra shrub invasion and soot deposition: Consequences for spring snowmelt and near-surface air temperatures

NASA Astrophysics Data System (ADS)

Strack, John E.

Invasive shrubs and soot pollution both have the potential to alter the surface energy balance and timing of snow melt in the Arctic. Shrubs reduce the amount of snow lost to sublimation on the tundra during the winter leading to a deeper end-of-winter snowpack. The shrubs also enhance the absorption of energy by the snowpack during the melt season, by converting incoming solar radiation to longwave radiation and sensible heat. This results in a faster rate of snow melt, warmer near-surface air temperatures, and a deeper boundary layer. Soot deposition lowers the albedo of the snow allowing it to more effectively absorb incoming solar radiation and thus melt faster. This study uses the Colorado State University Regional Atmospheric Modeling System version 4.4 (CSU-RAMS 4.4), equipped with an enhanced snow model, to investigate the effects of shrub encroachment and soot deposition on the atmosphere and snowpack in the Kuparuk Basin of Alaska during the May-June melt period. The results of the simulations suggest that a complete invasion of the tundra by shrubs leads to a 1.5 degree C warming of 2-m air temperatures, 17 watts per meter square increase in surface sensible heat flux, and a 108 m increase in boundary layer depth during the melt period. The snow free-date also occurred 11 days earlier despite having a larger initial snowpack. The results also show that a decrease in the snow albedo of 0.1, due to soot pollution, caused the snow-free date to occur five days earlier. The soot pollution caused a 0.5 degree C warming of 2-m air temperatures and a 2 watts per meter square increase in surface sensible heat flux. In addition, the boundary layer averaged 25 m deeper in the polluted snow simulation.

Faster eating rates are associated with higher energy intakes during an ad libitum meal, higher BMI and greater adiposity among 4·5-year-old children: results from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) cohort.

PubMed

Fogel, Anna; Goh, Ai Ting; Fries, Lisa R; Sadananthan, Suresh A; Velan, S Sendhil; Michael, Navin; Tint, Mya-Thway; Fortier, Marielle V; Chan, Mei Jun; Toh, Jia Ying; Chong, Yap-Seng; Tan, Kok Hian; Yap, Fabian; Shek, Lynette P; Meaney, Michael J; Broekman, Birit F P; Lee, Yung Seng; Godfrey, Keith M; Chong, Mary F F; Forde, Ciarán G

2017-04-01

Faster eating rates are associated with increased energy intake, but little is known about the relationship between children's eating rate, food intake and adiposity. We examined whether children who eat faster consume more energy and whether this is associated with higher weight status and adiposity. We hypothesised that eating rate mediates the relationship between child weight and ad libitum energy intake. Children (n 386) from the Growing Up in Singapore Towards Healthy Outcomes cohort participated in a video-recorded ad libitum lunch at 4·5 years to measure acute energy intake. Videos were coded for three eating-behaviours (bites, chews and swallows) to derive a measure of eating rate (g/min). BMI and anthropometric indices of adiposity were measured. A subset of children underwent MRI scanning (n 153) to measure abdominal subcutaneous and visceral adiposity. Children above/below the median eating rate were categorised as slower and faster eaters, and compared across body composition measures. There was a strong positive relationship between eating rate and energy intake (r 0·61, P<0·001) and a positive linear relationship between eating rate and children's BMI status. Faster eaters consumed 75 % more energy content than slower eating children (Δ548 kJ (Δ131 kcal); 95 % CI 107·6, 154·4, P<0·001), and had higher whole-body (P<0·05) and subcutaneous abdominal adiposity (Δ118·3 cc; 95 % CI 24·0, 212·7, P=0·014). Mediation analysis showed that eating rate mediates the link between child weight and energy intake during a meal (b 13·59; 95 % CI 7·48, 21·83). Children who ate faster had higher energy intake, and this was associated with increased BMI z-score and adiposity.

Faster eating rates are associated with higher energy intakes during an Ad libitum meal, higher BMI and greater adiposity among 4.5 year old children – Results from the GUSTO cohort

PubMed Central

Fogel, Anna; Goh, Ai Ting; Fries, Lisa R.; Sadananthan, Suresh Anand; Velan, S. Sendhil; Michael, Navin; Tint, Mya Thway; Fortier, Marielle Valerie; Chan, Mei Jun; Toh, Jia Ying; Chong, Yap-Seng; Tan, Kok Hian; Yap, Fabian; Shek, Lynette P.; Meaney, Michael J.; Broekman, Birit F.P.; Lee, Yung Seng; Godfrey, Keith M.; Chong, Mary Foong Fong; Forde, Ciarán Gerard

2017-01-01

Faster eating rates are associated with increased energy intake, but less is known about the relationship between children’s eating rate, food intake and adiposity. We examined whether children who eat faster consume more energy and whether this is associated with higher weight status and adiposity. We hypothesized that eating rate mediates the relationship between child weight and ad libitum energy intake. Children (N=386) from the Growing Up in Singapore towards Healthy Outcomes (GUSTO) cohort participated in a video-recorded ad libitum lunch at 4.5 years to measure acute energy intake. Videos were coded for three eating-behaviours (bites, chews and swallows) to derive a measure of eating rate (g/min). Body mass index (BMI) and anthropometric indices of adiposity were measured. A subset of children underwent MRI scanning (n=153) to measure abdominal subcutaneous and visceral adiposity. Children above/below the median eating rate were categorised as slower and faster eaters, and compared across body composition measures. There was a strong positive relationship between eating rate and energy intake (r=0.61, p<0.001) and a positive linear relationship between eating rate and children’s BMI status. Faster eaters consumed 75% more calories than slower eating children (Δ131 kcal, 95%CI [107.6, 154.4], p<0.001), and had higher whole-body (p<0.05) and subcutaneous abdominal adiposity (Δ118.3 cc; 95%CI [24.0, 212.7], p=0.014). Mediation analysis showed that eating rate mediates the link between child weight and energy intake during a meal (b=13.59, 95% CI [7.48, 21.83]). Children who ate faster had higher energy intake, and this was associated with increased BMIz and adiposity. PMID:28462734

FMRFamide signaling promotes stress-induced sleep in Drosophila

PubMed Central

Lenz, Olivia; Xiong, Jianmei; Nelson, Matthew D.; Raizen, David M.; Williams, Julie A.

2015-01-01

Enhanced sleep in response to cellular stress is a conserved adaptive behavior across multiple species, but the mechanism of this process is poorly understood. Drosophila melanogaster increases sleep following exposure to septic or aseptic injury, and Caenorhabditis elegans displays sleep-like quiescence following exposure to high temperatures that stress cells. We show here that, similar to C. elegans, Drosophila responds to heat stress with an increase in sleep. In contrast to Drosophila infection-induced sleep, heat-induced sleep is not sensitive to the time-of-day of the heat pulse. Moreover, the sleep response to heat stress does not require Relish, the NFκB transcription factor that is necessary for infection-induced sleep, indicating that sleep is induced by multiple mechanisms from different stress modalities. We identify a sleep-regulating role for a signaling pathway involving FMRFamide neuropeptides and their receptor FR. Animals mutant for either FMRFamide or for the FMRFamide receptor (FR) have a reduced recovery sleep in response to heat stress. FR mutants, in addition, show reduced sleep responses following infection with Serratia marcescens, and succumb to infection at a faster rate than wild-type controls. Together, these findings support the hypothesis that FMRFamide and its receptor promote an adaptive increase in sleep following stress. Because an FMRFamide-like neuropeptide plays a similar role in C. elegans, we propose that FRMFamide neuropeptide signaling is an ancient regulator of recovery sleep which occurs in response to cellular stress. PMID:25668617

FMRFamide signaling promotes stress-induced sleep in Drosophila.

PubMed

Lenz, Olivia; Xiong, Jianmei; Nelson, Matthew D; Raizen, David M; Williams, Julie A

2015-07-01

Enhanced sleep in response to cellular stress is a conserved adaptive behavior across multiple species, but the mechanism of this process is poorly understood. Drosophila melanogaster increases sleep following exposure to septic or aseptic injury, and Caenorhabditis elegans displays sleep-like quiescence following exposure to high temperatures that stress cells. We show here that, similar to C. elegans, Drosophila responds to heat stress with an increase in sleep. In contrast to Drosophila infection-induced sleep, heat-induced sleep is not sensitive to the time-of-day of the heat pulse. Moreover, the sleep response to heat stress does not require Relish, the NFκB transcription factor that is necessary for infection-induced sleep, indicating that sleep is induced by multiple mechanisms from different stress modalities. We identify a sleep-regulating role for a signaling pathway involving FMRFamide neuropeptides and their receptor FR. Animals mutant for either FMRFamide or for the FMRFamide receptor (FR) have a reduced recovery sleep in response to heat stress. FR mutants, in addition, show reduced sleep responses following infection with Serratia marcescens, and succumb to infection at a faster rate than wild-type controls. Together, these findings support the hypothesis that FMRFamide and its receptor promote an adaptive increase in sleep following stress. Because an FMRFamide-like neuropeptide plays a similar role in C. elegans, we propose that FRMFamide neuropeptide signaling is an ancient regulator of recovery sleep which occurs in response to cellular stress. Copyright © 2015 Elsevier Inc. All rights reserved.

Endotrophic Calcium, Strontium, and Barium Spores of Bacillus megaterium and Bacillus cereus1

PubMed Central

Foerster, Harold F.; Foster, J. W.

1966-01-01

Foerster, Harold F. (The University of Texas, Austin), and J. W. Foster. Endotrophic calcium, strontium, and barium spores of Bacillus megaterium and Bacillus cereus. J. Bacteriol. 91:1333–1345. 1966.—Spores were produced by washed vegetative cells suspended in deionized water supplemented with CaCl2, SrCl2, or BaCl2. Normal, refractile spores were produced in each case; a portion of the barium spores lost refractility and darkened. Thin-section electron micrographs revealed no apparent anatomical differences among the three types of spores. Analyses revealed that the different spore types were enriched specifically in the metal to which they were exposed during sporogenesis. The calcium content of the strontium and the barium spores was very small. From binary equimolar mixtures of the metal salts, endotrophic spores accumulated both metals to nearly the same extent. Viability of the barium spores was considerably less than that of the other two types. Strontium and barium spores were heat-resistant; however, calcium was essential for maximal heat resistance. Significant differences existed in the rates of germination; calcium spores germinated fastest, strontium spores were slower, and barium spores were slowest. Calcium-barium and calcium-strontium spores germinated readily. Endotrophic calcium and strontium spores germinated without the prior heat activation essential for growth spores. Chemical germination of the different metal-type spores with n-dodecylamine took place at the same relative rates as physiological germination. Heat-induced release of dipicolinic acid occurred much faster with barium and strontium spores than with calcium spores. The washed “coat fraction” from disrupted spores contained little of the spore calcium but most of the spore barium. The metal in this fraction was released by dilute acid. The demineralized coats reabsorbed calcium and barium at neutral pH. Images PMID:4956334

Performance of a convective, infrared and combined infrared- convective heated conveyor-belt dryer.

PubMed

El-Mesery, Hany S; Mwithiga, Gikuru

2015-05-01

A conveyor-belt dryer was developed using a combined infrared and hot air heating system that can be used in the drying of fruits and vegetables. The drying system having two chambers was fitted with infrared radiation heaters and through-flow hot air was provided from a convective heating system. The system was designed to operate under either infrared radiation and cold air (IR-CA) settings of 2000 W/m(2) with forced ambient air at 30 °C and air flow of 0.6 m/s or combined infrared and hot air convection (IR-HA) dryer setting with infrared intensity set at 2000 W/m(2) and hot at 60 °C being blown through the dryer at a velocity of 0.6 m/s or hot air convection (HA) at an air temperature of 60 °C and air flow velocity 0.6 m/s but without infrared heating. Apple slices dried under the different dryer settings were evaluated for quality and energy requirements. It was found that drying of apple (Golden Delicious) slices took place in the falling rate drying period and no constant rate period of drying was observed under any of the test conditions. The IR-HA setting was 57.5 and 39.1 % faster than IR-CA and HA setting, respectively. Specific energy consumption was lower and thermal efficiency was higher for the IR-HA setting when compared to both IR-CA and HA settings. The rehydration ratio, shrinkage and colour properties of apples dried under IR-HA conditions were better than for either IR-CA or HA.

Pressure- and heat-induced inactivation of butyrylcholinesterase: evidence for multiple intermediates and the remnant inactivation process.

PubMed Central

Weingand-Ziade, A; Ribes, F; Renault, F; Masson, P

2001-01-01

The inactivation process of native (N) human butyrylcholinesterase (BuChE) by pressure and/or heat was found to be multi-step. It led to irreversible formation of an active intermediate (I) state and a denatured state. This series-inactivation process was described by expanding the Lumry-Eyring [Lumry, R. and Eyring, H. (1954) J. Phys. Chem. 58, 110-120] model. The intermediate state (I) was found to have a K(m) identical with that of the native state and a turnover rate (k(cat)) twofold higher than that of the native state with butyrylthiocholine as the substrate. The increased catalytic efficiency (k(cat)/K(m)) of I can be explained by a conformational change in the active-site gorge and/or restructuring of the water-molecule network in the active-site pocket, making the catalytic steps faster. However, a pressure/heat-induced covalent modification of native BuChE, affecting the catalytic machinery, cannot be ruled out. The inactivation process of BuChE induced by the combined action of pressure and heat was found to continue after interruption of pressure/temperature treatment. This secondary inactivation process was termed 'remnant inactivation'. We hypothesized that N and I were in equilibrium with populated metastable N' and I' states. The N' and I' states can either return to the active forms, N and I, or develop into inactive forms, N(')(in) and I(')(in). Both active N' and I' intermediate states displayed different rates of remnant inactivation depending on the pressure and temperature pretreatments and on the storage temperature. A first-order deactivation model describing the kinetics of the remnant inactivation of BuChE is proposed. PMID:11368776

Consistency of Eating Rate, Oral Processing Behaviours and Energy Intake across Meals

PubMed Central

McCrickerd, Keri; Forde, Ciaran G.

2017-01-01

Faster eating has been identified as a risk factor for obesity and the current study tested whether eating rate is consistent within an individual and linked to energy intake across multiple meals. Measures of ad libitum intake, eating rate, and oral processing at the same or similar test meal were recorded on four non-consecutive days for 146 participants (117 male, 29 female) recruited across four separate studies. All the meals were video recorded, and oral processing behaviours were derived through behavioural coding. Eating behaviours showed good to excellent consistency across the meals (intra-class correlation coefficients > 0.76, p < 0.001) and participants who ate faster took larger bites (β ≥ 0.39, p < 0.001) and consistently consumed more energy, independent of meal palatability, sex, body composition and reported appetite (β ≥ 0.17, p ≤ 0.025). Importantly, eating faster at one meal predicted faster eating and increased energy intake at subsequent meals (β > 0.20, p < 0.05). Faster eating is relatively consistent within individuals and is predictive of faster eating and increased energy intake at subsequent similar meals consumed in a laboratory context, independent of individual differences in body composition. PMID:28817066

Necessity of Removing American Football Uniforms From Humans With Hyperthermia Before Cold-Water Immersion.

PubMed

Miller, Kevin C; Long, Blaine C; Edwards, Jeffrey

2015-12-01

The National Athletic Trainers' Association and the American College of Sports Medicine have recommended removing American football uniforms from athletes with exertional heat stroke before cold-water immersion (CWI) based on the assumption that the uniform impedes rectal temperature (T(rec)) cooling. Few experimental data exist to verify or disprove this assumption and the recommendations. To compare CWI durations, T(rec) cooling rates, thermal sensation, intensity of environmental symptoms, and onset of shivering when hyperthermic participants wore football uniforms during CWI or removed the uniforms immediately before CWI. Crossover study. Laboratory. Eighteen hydrated, physically active men (age = 22 ± 2 years, height = 182.5 ± 6.1 cm, mass = 85.4 ± 13.4 kg, body fat = 11% ± 5%, body surface area = 2.1 ± 0.2 m(2)) volunteered. On 2 days, participants exercised in the heat (approximately 40°C, approximately 40% relative humidity) while wearing a full American football uniform (shoes; crew socks; undergarments; shorts; game pants; undershirt; shoulder pads; jersey; helmet; and padding over the thighs, knees, hips, and tailbone [PADS]) until T(rec) reached 39.5°C. Next, participants immersed themselves in water that was approximately 10°C while wearing either undergarments, shorts, and crew socks (NOpads) or PADS without shoes until Trec reached 38°C. The CWI duration (minutes) and T(rec) cooling rates (°C/min). Participants had similar exercise times (NOpads = 40.8 ± 4.9 minutes, PADS = 43.2 ± 4.1 minutes; t(17) = 2.0, P = .10), hypohydration levels (NOpads = 1.5% ± 0.3%, PADS = 1.6% ± 0.4%; t(17) = 1.3, P = .22), and thermal-sensation ratings (NOpads = 7.2 ± 0.3, PADS = 7.1 ± 0.5; P > .05) before CWI. The CWI duration (median [interquartile range]; NOpads = 6.0 [5.4] minutes, PADS = 7.3 [9.8] minutes; z = 2.3, P = .01) and T(rec) cooling rates (NOpads = 0.28°C/min ± 0.14°C/min, PADS = 0.21°C/min ± 0.11°C/min; t(17) = 2.2, P = .02) differed between uniform conditions. Whereas participants cooled faster in NOpads, we still considered the PADS cooling rate to be acceptable (ie, >0.16°C/min). Therefore, if clinicians experience difficulty removing PADS or CWI treatment is delayed, they may immerse fully equipped hyperthermic football players in CWI and maintain acceptable T(rec) cooling rates. Otherwise, PADS should be removed preimmersion to ensure faster body core temperature cooling.

Effects of physical and nutritional stress conditions during mycelial growth on conidial germination speed, adhesion to host cuticle, and virulence of Metarhizium anisopliae, an entomopathogenic fungus.

PubMed

Rangel, Drauzio E N; Alston, Diane G; Roberts, Donald W

2008-11-01

Growth under stress may influence pathogen virulence and other phenotypic traits. Conidia of the entomopathogenic fungus Metarhizium anisopliae var. anisopliae (isolate ARSEF 2575) were produced under different stress conditions and then examined for influences on in vitro conidial germination speed, adhesion to the insect cuticle, and virulence to an insect host, Tenebrio molitor. Conidia were produced under non-stress conditions [on potato-dextrose agar plus 1gl(-1) yeast extract (PDAY; control)], or under the following stress conditions: osmotic (PDAY+sodium chloride or potassium chloride, 0.6 or 0.8m); oxidative [(PDAY+hydrogen peroxide, 5mm) or UV-A (irradiation of mycelium on PDAY)]; heat shock (heat treatment of mycelium on PDAY at 45 degrees C, 40min); and nutritive [minimal medium (MM) with no carbon source, or on MM plus 3gl(-1) lactose (MML)]. Conidia were most virulent (based on mortality at 3d) and had the fastest germination rates when produced on MML, followed by MM. In addition, conidial adhesion to host cuticle was greatest when the conidia were produced on MML. Media with high osmolarity (0.8m) produced conidia with slightly elevated virulence and faster germination rates than conidia produced on the control medium (PDAY), but this trend did not hold for media with the lower osmolarity, (0.6m). Conidia produced from mycelium irradiated with UV-A while growing on PDAY had somewhat elevated virulence levels similar to that of conidia produced on MM, but their germination rate was not increased. Hydrogen peroxide and heat shock treatments did not alter virulence. These results demonstrate that the germination, adhesion and virulence of M. anisopliae conidia can be strongly influenced by culture conditions (including stresses) during production of the conidia.

Interplay between Heat Shock Proteins HSP101 and HSA32 Prolongs Heat Acclimation Memory Posttranscriptionally in Arabidopsis1[W][OA

PubMed Central

Wu, Ting-ying; Juan, Yu-ting; Hsu, Yang-hsin; Wu, Sze-hsien; Liao, Hsiu-ting; Fung, Raymond W.M.; Charng, Yee-yung

2013-01-01

Heat acclimation improves the tolerance of organisms to severe heat stress. Our previous work showed that in Arabidopsis (Arabidopsis thaliana), the “memory” of heat acclimation treatment decayed faster in the absence of the heat-stress-associated 32-kD protein HSA32, a heat-induced protein predominantly found in plants. The HSA32 null mutant attains normal short-term acquired thermotolerance but is defective in long-term acquired thermotolerance. To further explore this phenomenon, we isolated Arabidopsis defective in long-term acquired thermotolerance (dlt) mutants using a forward genetic screen. Two recessive missense alleles, dlt1-1 and dlt1-2, encode the molecular chaperone heat shock protein101 (HSP101). Results of immunoblot analyses suggest that HSP101 enhances the translation of HSA32 during recovery after heat treatment, and in turn, HSA32 retards the decay of HSP101. The dlt1-1 mutation has little effect on HSP101 chaperone activity and thermotolerance function but compromises the regulation of HSA32. In contrast, dlt1-2 impairs the chaperone activity and thermotolerance function of HSP101 but not the regulation of HSA32. These results suggest that HSP101 has a dual function, which could be decoupled by the mutations. Pulse-chase analysis showed that HSP101 degraded faster in the absence of HSA32. The autophagic proteolysis inhibitor E-64d, but not the proteasome inhibitor MG132, inhibited the degradation of HSP101. Ectopic expression of HSA32 confirmed its effect on the decay of HSP101 at the posttranscriptional level and showed that HSA32 was not sufficient to confer long-term acquired thermotolerance when the HSP101 level was low. Taken together, we propose that a positive feedback loop between HSP101 and HSA32 at the protein level is a novel mechanism for prolonging the memory of heat acclimation. PMID:23439916

Soil Carbon Response to Soil Warming and Nitrogen Deposition in a Temperate Deciduous Forest

NASA Astrophysics Data System (ADS)

Parton, W. J.; Savage, K. E.; Davidson, E. A.; Trumbore, S.; Frey, S. D.

2011-12-01

While estimates of global soil C stocks vary widely, it is clear that soils store several times more C than is present in the atmosphere as CO2, and a significant fraction of soil C stocks are potentially subject to faster rates of decomposition in a warmer world. We address, through field based studies and modeling efforts, whether manipulations of soil temperature and nitrogen supply affect the magnitude and relative age of soil C substrates that are respired from a temperate deciduous forest located at Harvard Forest, MA. A soil warming and nitrogen addition experiment was initiated at the Harvard Forest in 2006. The experiment consists of six replicates of four treatments, control, heated, nitrogen, and heat+nitrogen addition. Soil temperatures in the heated plots are continuously elevated 5 oC above ambient and for the fertilized plots an aqueous solution of NH4NO3 is applied at a rate of 5 g m-2 yr-1. Soil C efflux from these plots was measured (n=24, 6 per treatment) biweekly throughout the year, while 14CO2 was measured (3 samples per treatment) several times during the summer months from 2006-2010. Following treatment, observed rates of annual C efflux increased under heating and nitrogen additions with heating treatments showing the greatest increase in respired C. The difference between control and treatments was greatest during the initial year following treatment; however this difference decreased in the subsequent 3 years of measurement. The plots designated for heating had a higher 14C signature from CO2 efflux prior to the heating (presumably due to spatial heterogeneity). However, because of the high spatial heterogeneity in measured 14C among treatments, no significant difference among treatments was observed from 2006 through 2010. Long term datasets (1995 through 2010) of soil C stocks, radiocarbon content, and CO2 efflux were used to parameterize the ForCent model for Harvard forest. The model was then run with the same treatment parameters as the field experiment for comparison of soil C efflux and 14C. Model results show increased annual C efflux for heated, nitrogen and nitrogen+heat plots with the largest increase in respired C from heated treatments. However there was little difference in simulated 14C respired from any treatment plots. While heating speeds up decomposition of all soil C pools in the model, the absolute amount of increased decomposition from the older pools (with higher 14C) was not large enough to make a difference in 14C composition of respired C, even as the more labile pool with lower 14C was gradually depleted. These results demonstrate that experiments conducted over several years do not provide great insight into the dynamics of slowly cycling soil C.

PICA Variants with Improved Mechanical Properties

NASA Technical Reports Server (NTRS)

Thornton, Jeremy; Ghandehari, Ehson M.; Fan, Wenhong; Stackpoole, Margaret; Chavez-Garcia, Jose

2011-01-01

Phenolic Impregnated Carbon Ablator (PICA) is a member of the family of Lightweight Ceramic Ablators (LCAs) and was developed at NASA Ames Research Center as a thermal protection system (TPS) material for the Stardust mission probe that entered the Earth s atmosphere faster than any other probe or vehicle to date. PICA, carbon fiberform base and phenolic polymer, shows excellent thermal insulative properties at heating rates from about 250 W/sq cm to 1000 W/sq cm. The density of standard PICA - 0.26 g/cu cm to 0.28 g/cu cm - can be changed by changing the concentration of the phenolic resin. By adding polymers to the phenolic resin before curing it is possible to significantly improve the mechanical properties of PICA without significantly increasing the density.

A Study on Fast Gates for Large-Scale Quantum Simulation with Trapped Ions

PubMed Central

Taylor, Richard L.; Bentley, Christopher D. B.; Pedernales, Julen S.; Lamata, Lucas; Solano, Enrique; Carvalho, André R. R.; Hope, Joseph J.

2017-01-01

Large-scale digital quantum simulations require thousands of fundamental entangling gates to construct the simulated dynamics. Despite success in a variety of small-scale simulations, quantum information processing platforms have hitherto failed to demonstrate the combination of precise control and scalability required to systematically outmatch classical simulators. We analyse how fast gates could enable trapped-ion quantum processors to achieve the requisite scalability to outperform classical computers without error correction. We analyze the performance of a large-scale digital simulator, and find that fidelity of around 70% is realizable for π-pulse infidelities below 10−5 in traps subject to realistic rates of heating and dephasing. This scalability relies on fast gates: entangling gates faster than the trap period. PMID:28401945

A Study on Fast Gates for Large-Scale Quantum Simulation with Trapped Ions.

PubMed

Taylor, Richard L; Bentley, Christopher D B; Pedernales, Julen S; Lamata, Lucas; Solano, Enrique; Carvalho, André R R; Hope, Joseph J

2017-04-12

Large-scale digital quantum simulations require thousands of fundamental entangling gates to construct the simulated dynamics. Despite success in a variety of small-scale simulations, quantum information processing platforms have hitherto failed to demonstrate the combination of precise control and scalability required to systematically outmatch classical simulators. We analyse how fast gates could enable trapped-ion quantum processors to achieve the requisite scalability to outperform classical computers without error correction. We analyze the performance of a large-scale digital simulator, and find that fidelity of around 70% is realizable for π-pulse infidelities below 10 -5 in traps subject to realistic rates of heating and dephasing. This scalability relies on fast gates: entangling gates faster than the trap period.

Three-dimensional numerical simulation during laser processing of CFRP

NASA Astrophysics Data System (ADS)

Ohkubo, Tomomasa; Sato, Yuji; Matsunaga, Ei-ichi; Tsukamoto, Masahiro

2017-09-01

We performed three-dimensional numerical simulation about laser processing of carbon-fiber-reinforced plastic (CFRP) using OpenFOAM as libraries of finite volume method (FVM). Although a little theoretical or numerical studies about heat affected zone (HAZ) formation were performed, there is no research discussing how HAZ is generated considering time development about removal of each material. It is important to understand difference of removal speed of carbon fiber and resin in order to improve quality of cut surface of CFRP. We demonstrated how the carbon fiber and resin are removed by heat of ablation plume by our simulation. We found that carbon fiber is removed faster than resin at first stage because of the difference of thermal conductivity, and after that, the resin is removed faster because of its low combustion temperature. This result suggests the existence of optimal contacting time of the laser ablation and kerf of the target.

High Strain Rate Testing of Welded DOP-26 Iridium

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

Schneibel, J. H.; Miller, R. G.; Carmichael, C. A.

The iridium alloy DOP-26 is used to produce Clad Vent Set cups that protect the radioactive fuel in radioisotope thermoelectric generators (RTGs) which provide electric power for spacecraft and rovers. In a previous study, the tensile properties of DOP-26 were measured over a wide range of strain rates and temperatures and reported in ORNL/TM-2007/81. While that study established the properties of the base material, the fabrication of the heat sources requires welding, and the mechanical properties of welded DOP-26 have not been extensively characterized in the past. Therefore, this study was undertaken to determine the mechanical properties of DOP-26 specimensmore » containing a transverse weld in the center of their gage sections. Tensile tests were performed at room temperature, 750, 900, and 1090°C and engineering strain rates of 1×10 -3 and 10 s -1. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1×10 -4 Torr. The welded specimens had a significantly higher yield stress, by up to a factor of ~2, than the non-welded base material. The yield stress did not depend on the strain rate except at 1090°C, where it was slightly higher for the faster strain rate. The ultimate tensile stress, on the other hand, was significantly higher for the faster strain rate at temperatures of 750°C and above. At 750°C and above, the specimens deformed at 1×10 -3 s -1 showed pronounced necking resulting sometimes in perfect chisel-edge fracture. The specimens deformed at 10 s -1 exhibited this fracture behavior only at the highest test temperature, 1090°C. Fracture occurred usually in the fusion zone of the weld and was, in most cases, primarily intergranular.« less

Pore Pressure Evolution in Shallow Subduction Earthquake Sequences and Effects on Aseismic Slip Transients -- Numerical Modeling With Rate and State Friction

NASA Astrophysics Data System (ADS)

Liu, Y.; Rice, J. R.

2005-12-01

In 3D modeling of long tectonic loading and earthquake sequences on a shallow subduction fault [Liu and Rice, 2005], with depth-variable rate and state friction properties, we found that aseismic transient slip episodes emerge spontaneously with only a simplified representation of effects of metamorphic fluid release. That involved assumption of a constant in time but uniformly low effective normal stress in the downdip region. As suggested by observations in several major subduction zones [Obara, 2002; Rogers and Dragert, 2003; Kodaira et al, 2004], the presence of fluids, possibly released from dehydration reactions beneath the seismogenic zone, and their pressurization within the fault zone may play an important role in causing aseismic transients and associated non-volcanic tremors. To investigate the effects of fluids in the subduction zone, particularly on the generation of aseismic transients and their various features, we develop a more complete physical description of the pore pressure evolution (specifically, pore pressure increase due to supply from dehydration reactions and shear heating, decrease due to transport and dilatancy during slip), and incorporate that into the rate and state based 3D modeling. We first incorporated two important factors, dilatancy and shear heating, following Segall and Rice [1995, 2004] and Taylor [1998]. In the 2D simulations (slip varies with depth only), a dilatancy-stabilizing effect is seen which slows down the seismic rupture front and can prevent rapid slip from extending all the way to the trench, similarly to Taylor [1998]. Shear heating increases the pore pressure, and results in faster coseismic rupture propagation and larger final slips. In the 3D simulations, dilatancy also stabilizes the along-strike rupture propagation of both seismic and aseismic slips. That is, aseismic slip transients migrate along the strike faster with a shorter Tp (the characteristic time for pore pressure in the fault core to re-equilibrate with that of its surroundings). This is consistent with our previous simulations, which show that the aseismic transients migrate along the strike at a higher speed under a lower, constant in time, effective normal stress. As a combination of the two factors, we show the pore pressure evolution with drops (due to dilatancy during slip) and then rises (due to shear heating) on the fault over multiple time scales. We next plan to formulate, and merge with the slip-rupture analysis, fuller fluid release models based on phase equilibria and models of transport in which the average fault-parallel permeability is a decreasing function of the effective normal stress. The thrust fault zone, at seismogenic depths and slightly downdip, is represented in a conceptually similar manner to the well-studied major continental faults, assuming the fault core materials have a lower permeability than the neighboring damaged zone. Heat diffusion in the fault core and damaged zone will also be considered in the modeling. The simulation results may help to improve our understanding of the processes of the aseismic transients observed within a transform plate boundary along the SAF near Cholame, California [Nadeau and Dolenc, 2005].

Consolidation of lunar regolith: Microwave versus direct solar heating

NASA Technical Reports Server (NTRS)

Kunitzer, J.; Strenski, D. G.; Yankee, S. J.; Pletka, B. J.

1991-01-01

The production of construction materials on the lunar surface will require an appropriate fabrication technique. Two processing methods considered as being suitable for producing dense, consolidated products such as bricks are direct solar heating and microwave heating. An analysis was performed to compare the two processes in terms of the amount of power and time required to fabricate bricks of various size. The regolith was considered to be a mare basalt with an overall density of 60 pct. of theoretical. Densification was assumed to take place by vitrification since this process requires moderate amounts of energy and time while still producing dense products. Microwave heating was shown to be significantly faster compared to solar furnace heating for rapid production of realistic-size bricks.

Procedural Pain Heart Rate Responses in Massaged Preterm Infants

PubMed Central

Diego, Miguel A.; Field, Tiffany; Hernandez-Reif, Maria

2009-01-01

Heart rate (HR) responses to the removal of a monitoring lead were assessed in 56 preterm infants who received moderate pressure, light pressure or no massage therapy. The infants who received moderate pressure massage therapy exhibited lower increases in HR suggesting an attenuated pain response. The heart rate of infants who received moderate pressure massage also returned to baseline faster than the heart rate of the other two groups, suggesting a faster recovery rate. PMID:19185352

Treatment of lactating dairy cows with gonadotropin-releasing hormone before first insemination during summer heat stress.

PubMed

Voelz, B E; Rocha, L; Scortegagna, F; Stevenson, J S; Mendonça, L G D

2016-09-01

The objectives of the experiments were to compare ovarian responses, pregnancy per artificial insemination, and pattern of insemination of 2 estrus detection-based presynchronization protocols before first artificial insemination (AI) during heat stress. In experiment 1, primiparous lactating dairy cows (n=1,358) from 3 dairies were assigned randomly to 2 treatments at 60±3 (±SD) DIM (study d 0): (1) treatment with 100 µg of GnRH on study d 0 (Gpresynch), or (2) no treatment on study d 0 (control). In experiment 2, multiparous lactating dairy cows (n=1,971) from 3 dairies were assigned randomly to 2 treatments at 49±3 (±SD) DIM (study d 0), similar to experiment 1. In both experiments, PGF2α injections were administered 14 d apart starting on study d 7 for all cows. Cows not inseminated after detection of estrus were submitted to a timed artificial insemination protocol at study d 35. In a subgroup of cows from 2 dairies, concentrations of progesterone were determined from blood samples collected on study d 0 and 7. Furthermore, ovaries were examined by ultrasonography on study d -14, 0, and 7 to determine cyclic status and ovulation in response to GnRH treatment. In experiment 1, progesterone concentration was not different on d 0, but progesterone was increased for Gpresynch compared with control cows on study d 7 (3.6±0.3 vs. 2.7±0.4 ng/mL), respectively. Ovulation risk from study d 0 to 7 was increased for Gpresynch compared with control (50.6 vs. 15.2%). Control cows were inseminated at a faster rate than Gpresynch cows [adjusted hazard ratio (AHR)=0.89, 95% confidence interval=0.80 to 1.00], and the interaction between treatment and dairy affected pregnancy per artificial insemination at 36 and 94 d post-artificial insemination. In experiment 2, concentrations of progesterone did not differ on study d 0 or 7, despite ovulation risk from study d 0 to 7 being greater in Gpresynch than control cows (46.9 vs. 23.8%). The interaction between treatment and dairy affected hazard of insemination with Gpresynch cows from dairy 1 (AHR=1.21; 1.05 to 1.41) being inseminated faster than control cows. Hazard of pregnancy was affected by treatment because Gpresynch cows became pregnant at a faster rate than control cows (AHR=1.25; 1.04 to 1.50). In conclusion, GnRH-based presynchronization protocols initiated before the end of the voluntary waiting period may have benefits in reproductive efficiency of estrus detection-based programs during heat stress. In addition, treatment with GnRH decreased the prevalence of anovular cows at the initiation of PGF2α injections. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Thermal resistance, developmental rate and heat shock proteins in Artemia franciscana, from San Francisco Bay and southern Vietnam.

PubMed

Clegg; Jackson; Van Hoa N; Sorgeloos

2000-09-05

Cysts (encysted gastrula embryos) of Artemia franciscana collected from salterns in San Francisco Bay, California, USA (SF) were inoculated into much warmer growth ponds in the Mekong Delta region of Vietnam (V) in 1996. V adults arising directly from these cysts during 17 April to 15 May produced their own cysts, which were collected, processed and stored until shipped to the USA for study. Adults grown in the laboratory from SF cysts (those used for the inoculation) were less resistant to high temperature than adults cultured from V cysts. V cysts produced heat-resistant adults, even though cultured under the same laboratory conditions as SF animals, at much lower temperatures than they ever experienced in Vietnam. Differences in thermal performance between SF and V adults were retained in the second generation, cultured from cysts produced in the laboratory by first generation adults, suggesting a genetic basis for the better heat resistance of V adults. We propose that the operation of natural selection in the Vietnam growth ponds produced adults with improved thermal tolerance, and that the basis for this tolerance was incorporated into the developmental program of their cysts. Surprisingly, differences in heat resistance of laboratory reared animals were not reflected in constitutive levels of the hsp70 family which were similar in first generation SF and V adults. A conditioning heat shock (HS, 37 degrees C, 30 min) led to the same level of induced thermotolerance in SF and V first generation adults when evaluated 24 h post-HS. Levels of hsp70 were also up-regulated at that time, but to about the same extent in SF and V adults. Developmental rates of SF cysts used for the inoculation were faster than those of cysts produced in Vietnam when both were incubated at 21+/-1 degrees C, suggesting that V cysts have become adapted to develop at higher temperatures.

Articulation rate across dialect, age, and gender

PubMed Central

Jacewicz, Ewa; Fox, Robert A.; O’Neill, Caitlin; Salmons, Joseph

2009-01-01

The understanding of sociolinguistic variation is growing rapidly, but basic gaps still remain. Whether some languages or dialects are spoken faster or slower than others constitutes such a gap. Speech tempo is interconnected with social, physical and psychological markings of speech. This study examines regional variation in articulation rate and its manifestations across speaker age, gender and speaking situations (reading vs. free conversation). The results of an experimental investigation show that articulation rate differs significantly between two regional varieties of American English examined here. A group of Northern speakers (from Wisconsin) spoke significantly faster than a group of Southern speakers (from North Carolina). With regard to age and gender, young adults read faster than older adults in both regions; in free speech, only Northern young adults spoke faster than older adults. Effects of gender were smaller and less consistent; men generally spoke slightly faster than women. As the body of work on the sociophonetics of American English continues to grow in scope and depth, we argue that it is important to include fundamental phonetic information as part of our catalog of regional differences and patterns of change in American English. PMID:20161445

An evaporation model of colloidal suspension droplets

NASA Astrophysics Data System (ADS)

Sartori, Silvana; Li\\ Nán, Amable; Lasheras, Juan C.

2009-11-01

Colloidal suspensions of polymers in water or other solvents are widely used in the pharmaceutical industry to coat tablets with different agents. These allow controlling the rate at which the drug is delivered, taste or physical appearance. The coating is performed by simultaneously spraying and drying the tablets with the colloidal suspension at moderately high temperatures. The spreading of the coating on the pills surface depends on the droplet Webber and Reynolds numbers, angle of impact, but more importantly on the rheological properties of the drop. We present a model for the evaporation of a colloidal suspension droplet in a hot air environment with temperatures substantially lower than the boiling temperature of the carrier fluid. As the liquid vaporizes from the surface, a compacting front advances into the droplet faster than the liquid surface regresses, forming a shell of a porous medium where the particles reach their maximum packing density. While the surface regresses, the evaporation rate is determined by both the rate at which heat is transported to the droplet surface and the rate at which liquid vapor is diffused away from it. This regime continues until the compacting front reaches the center of the droplet, at which point the evaporation rate is drastically reduced.

Performance and efficiency evaluation and heat release study of a direct-injection stratified-charge rotary engine

NASA Technical Reports Server (NTRS)

Nguyen, H. L.; Addy, H. E.; Bond, T. H.; Lee, C. M.; Chun, K. S.

1987-01-01

A computer simulation which models engine performance of the Direct Injection Stratified Charge (DISC) rotary engines was used to study the effect of variations in engine design and operating parameters on engine performance and efficiency of an Outboard Marine Corporation (OMC) experimental rotary combustion engine. Engine pressure data were used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine data were compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the rotary engine using advanced heat engine concepts such as faster combustion, reduced leakage, and turbocharging is also presented.

Synthesis of poly(ethylene furandicarboxylate) polyester using monomers derived from renewable resources: thermal behavior comparison with PET and PEN.

PubMed

Papageorgiou, George Z; Tsanaktsis, Vasilios; Bikiaris, Dimitrios N

2014-05-07

Poly(ethylene-2,5-furandicarboxylate) (PEF) is a new alipharomatic polyester that can be prepared from monomers derived from renewable resources like furfural and hydroxymethylfurfural. For this reason it has gained high interest recently. In the present work it was synthesized from the dimethylester of 2,5-furandicarboxylic acid and ethylene glycol by applying the two-stage melt polycondensation method. The thermal behavior of PEF was studied in comparison to its terephthalate and naphthalate homologues poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN), which were also synthesized following the same procedure. The equilibrium melting point of PEF was found to be 265 °C while the heat of fusion for the pure crystalline PEF was estimated to be about 137 J g(-1). The crystallization kinetics was analyzed using various models. PET showed faster crystallization rates than PEN and this in turn showed faster crystallization than PEF, under both isothermal and non-isothermal conditions. The spherulitic morphology of PEF during isothermal crystallization was investigated by polarized light microscopy (PLM). A large nucleation density and a small spherulite size were observed for PEF even at low supercoolings, in contrast to PET or PEN. Thermogravimetric analysis indicated that PEF is thermally stable up to 325 °C and the temperature for the maximum degradation rate was 438 °C. These values were a little lower than those for PET or PEN.

Single neuropsychological test scores associated with rate of cognitive decline in early Alzheimer disease.

PubMed

Parikh, Mili; Hynan, Linda S; Weiner, Myron F; Lacritz, Laura; Ringe, Wendy; Cullum, C Munro

2014-01-01

Alzheimer disease (AD) characteristically begins with episodic memory impairment followed by other cognitive deficits; however, the course of illness varies, with substantial differences in the rate of cognitive decline. For research and clinical purposes it would be useful to distinguish between persons who will progress slowly from persons who will progress at an average or faster rate. Our objective was to use neurocognitive performance features and disease-specific and health information to determine a predictive model for the rate of cognitive decline in participants with mild AD. We reviewed the records of a series of 96 consecutive participants with mild AD from 1995 to 2011 who had been administered selected neurocognitive tests and clinical measures. Based on Clinical Dementia Rating (CDR) of functional and cognitive decline over 2 years, participants were classified as Faster (n = 45) or Slower (n = 51) Progressors. Stepwise logistic regression analyses using neurocognitive performance features, disease-specific, health, and demographic variables were performed. Neuropsychological scores that distinguished Faster from Slower Progressors included Trail Making Test - A, Digit Symbol, and California Verbal Learning Test (CVLT) Total Learned and Primacy Recall. No disease-specific, health, or demographic variable predicted rate of progression; however, history of heart disease showed a trend. Among the neuropsychological variables, Trail Making Test - A best distinguished Faster from Slower Progressors, with an overall accuracy of 68%. In an omnibus model including neuropsychological, disease-specific, health, and demographic variables, only Trail Making Test - A distinguished between groups. Several neuropsychological performance features were associated with the rate of cognitive decline in mild AD, with baseline Trail Making Test - A performance best separating those who declined at an average or faster rate from those who showed slower progression.

Thermal and impact history of the H chondrite parent asteroid during metamorphism: Constraints from metallic Fe-Ni

NASA Astrophysics Data System (ADS)

Scott, Edward R. D.; Krot, Tatiana V.; Goldstein, Joseph I.; Wakita, Shigeru

2014-07-01

We have studied cloudy taenite, metallographic cooling rates, and shock effects in 30 H3-6 chondrites to elucidate the thermal and early impact history of the H chondrite parent body. We focused on H chondrites with old Ar-Ar ages (>4.4 Gyr) and unshocked and mildly shocked H chondrites, as strongly shocked chondrites with such old ages are very rare. Cooling rates for most H chondrites at 500 °C are 10-50 °C/Myr and do not decrease systematically with increasing petrologic type as predicted by the onion-shell model in which types 3-5 are arranged in concentric layers around a type 6 core. Some type 4 chondrites cooled slower than some type 6 chondrites and type 3 chondrites did not cool faster than other types, contrary to the onion-shell model. Cloudy taenite particle sizes, which range from 40 to 120 nm, are inversely correlated with metallographic cooling rates and show that the latter were not compromised by shock heating. The three H4 chondrites that were used to develop the onion-shell model, Ste. Marguerite, Beaver Creek, and Forest Vale, cooled through 500 °C at ⩾5000 °C/Myr. Our thermal modeling shows that these rates are 50× higher than could be achieved in a body that was heated by 26Al and cooled without disturbance by impact. Published Ar-Ar ages do not decrease systematically with increasing petrologic type but do correlate inversely with cloudy taenite particle size suggesting that impact mixing decreased during metamorphism. Metal and silicate compositions in regolith breccias show that impacts mixed material after metamorphism without causing significant heating. Impacts during metamorphism created Portales Valley and two other H6 chondrites with large metallic veins, excavated the fast-cooled H4 chondrites around 3-4 Myr after accretion, and mixed petrologic types. Metallographic data do not require catastrophic disruption by impact during cooling.

Faster-X Evolution of Gene Expression in Drosophila

PubMed Central

Meisel, Richard P.; Malone, John H.; Clark, Andrew G.

2012-01-01

DNA sequences on X chromosomes often have a faster rate of evolution when compared to similar loci on the autosomes, and well articulated models provide reasons why the X-linked mode of inheritance may be responsible for the faster evolution of X-linked genes. We analyzed microarray and RNA–seq data collected from females and males of six Drosophila species and found that the expression levels of X-linked genes also diverge faster than autosomal gene expression, similar to the “faster-X” effect often observed in DNA sequence evolution. Faster-X evolution of gene expression was recently described in mammals, but it was limited to the evolutionary lineages shortly following the creation of the therian X chromosome. In contrast, we detect a faster-X effect along both deep lineages and those on the tips of the Drosophila phylogeny. In Drosophila males, the dosage compensation complex (DCC) binds the X chromosome, creating a unique chromatin environment that promotes the hyper-expression of X-linked genes. We find that DCC binding, chromatin environment, and breadth of expression are all predictive of the rate of gene expression evolution. In addition, estimates of the intraspecific genetic polymorphism underlying gene expression variation suggest that X-linked expression levels are not under relaxed selective constraints. We therefore hypothesize that the faster-X evolution of gene expression is the result of the adaptive fixation of beneficial mutations at X-linked loci that change expression level in cis. This adaptive faster-X evolution of gene expression is limited to genes that are narrowly expressed in a single tissue, suggesting that relaxed pleiotropic constraints permit a faster response to selection. Finally, we present a conceptional framework to explain faster-X expression evolution, and we use this framework to examine differences in the faster-X effect between Drosophila and mammals. PMID:23071459

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

Showman, Adam P.; Lewis, Nikole K.; Fortney, Jonathan J., E-mail: showman@lpl.arizona.edu

Efforts to characterize extrasolar giant planet (EGP) atmospheres have so far emphasized planets within 0.05 AU of their stars. Despite this focus, known EGPs populate a continuum of orbital separations from canonical hot Jupiter values (0.03–0.05 AU) out to 1 AU and beyond. Unlike typical hot Jupiters, these more distant EGPs will not generally be synchronously rotating. In anticipation of observations of this population, we here present three-dimensional atmospheric circulation models exploring the dynamics that emerge over a broad range of rotation rates and incident stellar fluxes appropriate for warm and hot Jupiters. We find that the circulation resides inmore » one of two basic regimes. On typical hot Jupiters, the strong day–night heating contrast leads to a broad, fast superrotating (eastward) equatorial jet and large day–night temperature differences. At faster rotation rates and lower incident fluxes, however, the day–night heating gradient becomes less important, and baroclinic instabilities emerge as a dominant player, leading to eastward jets in the midlatitudes, minimal temperature variations in longitude, and, often, weak winds at the equator. Our most rapidly rotating and least irradiated models exhibit similarities to Jupiter and Saturn, illuminating the dynamical continuum between hot Jupiters and the weakly irradiated giant planets of our own solar system. We present infrared (IR) light curves and spectra of these models, which depend significantly on incident flux and rotation rate. This provides a way to identify the regime transition in future observations. In some cases, IR light curves can provide constraints on the rotation rate of nonsynchronously rotating planets.« less

Kinetic Monte Carlo modeling of chemical reactions coupled with heat transfer.

PubMed

Castonguay, Thomas C; Wang, Feng

2008-03-28

In this paper, we describe two types of effective events for describing heat transfer in a kinetic Monte Carlo (KMC) simulation that may involve stochastic chemical reactions. Simulations employing these events are referred to as KMC-TBT and KMC-PHE. In KMC-TBT, heat transfer is modeled as the stochastic transfer of "thermal bits" between adjacent grid points. In KMC-PHE, heat transfer is modeled by integrating the Poisson heat equation for a short time. Either approach is capable of capturing the time dependent system behavior exactly. Both KMC-PHE and KMC-TBT are validated by simulating pure heat transfer in a rod and a square and modeling a heated desorption problem where exact numerical results are available. KMC-PHE is much faster than KMC-TBT and is used to study the endothermic desorption of a lattice gas. Interesting findings from this study are reported.

Kinetic Monte Carlo modeling of chemical reactions coupled with heat transfer

NASA Astrophysics Data System (ADS)

Castonguay, Thomas C.; Wang, Feng

2008-03-01

In this paper, we describe two types of effective events for describing heat transfer in a kinetic Monte Carlo (KMC) simulation that may involve stochastic chemical reactions. Simulations employing these events are referred to as KMC-TBT and KMC-PHE. In KMC-TBT, heat transfer is modeled as the stochastic transfer of "thermal bits" between adjacent grid points. In KMC-PHE, heat transfer is modeled by integrating the Poisson heat equation for a short time. Either approach is capable of capturing the time dependent system behavior exactly. Both KMC-PHE and KMC-TBT are validated by simulating pure heat transfer in a rod and a square and modeling a heated desorption problem where exact numerical results are available. KMC-PHE is much faster than KMC-TBT and is used to study the endothermic desorption of a lattice gas. Interesting findings from this study are reported.

Evolutionary stasis and lability in thermal physiology in a group of tropical lizards.

PubMed

Muñoz, Martha M; Stimola, Maureen A; Algar, Adam C; Conover, Asa; Rodriguez, Anthony J; Landestoy, Miguel A; Bakken, George S; Losos, Jonathan B

2014-03-07

Understanding how quickly physiological traits evolve is a topic of great interest, particularly in the context of how organisms can adapt in response to climate warming. Adjustment to novel thermal habitats may occur either through behavioural adjustments, physiological adaptation or both. Here, we test whether rates of evolution differ among physiological traits in the cybotoids, a clade of tropical Anolis lizards distributed in markedly different thermal environments on the Caribbean island of Hispaniola. We find that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances. Specifically, because lizards in very different environments behaviourally thermoregulate during the day to similar body temperatures, divergent selection on body temperature and heat tolerance is precluded, whereas night-time temperatures can only be partially buffered by behaviour, thereby exposing organisms to selection on cold tolerance. We discuss how exposure to selection on physiology influences divergence among tropical organisms and its implications for adaptive evolutionary response to climate warming.

Evolutionary stasis and lability in thermal physiology in a group of tropical lizards

PubMed Central

Muñoz, Martha M.; Stimola, Maureen A.; Algar, Adam C.; Conover, Asa; Rodriguez, Anthony J.; Landestoy, Miguel A.; Bakken, George S.; Losos, Jonathan B.

2014-01-01

Understanding how quickly physiological traits evolve is a topic of great interest, particularly in the context of how organisms can adapt in response to climate warming. Adjustment to novel thermal habitats may occur either through behavioural adjustments, physiological adaptation or both. Here, we test whether rates of evolution differ among physiological traits in the cybotoids, a clade of tropical Anolis lizards distributed in markedly different thermal environments on the Caribbean island of Hispaniola. We find that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances. Specifically, because lizards in very different environments behaviourally thermoregulate during the day to similar body temperatures, divergent selection on body temperature and heat tolerance is precluded, whereas night-time temperatures can only be partially buffered by behaviour, thereby exposing organisms to selection on cold tolerance. We discuss how exposure to selection on physiology influences divergence among tropical organisms and its implications for adaptive evolutionary response to climate warming. PMID:24430845

Numerical Simulations of Thermo-Mechanical Processes during Thermal Spallation Drilling for Geothermal Reservoirs

NASA Astrophysics Data System (ADS)

Vogler, D.; Walsh, S. D. C.; Rudolf von Rohr, P.; Saar, M. O.

2017-12-01

Drilling expenses constitute a significant share of the upfront capital costs and thereby the associated risks of geothermal energy production. This is especially true for deep boreholes, as drilling costs per meter increase significantly with depth. Thermal spallation drilling is a relatively new drilling technique, particularly suited to the hard crystalline (e.g., basement) rocks in which many deep geothermal resources are located. The method uses a hot jet-flame to rapidly heat the rock surface, which leads to large temperature gradients in the rock. These temperature gradients cause localized thermal stresses that, in combination with the in situ stress field, lead to the formation and ejection of spalls. These spalls are then transported out of the borehole with the drilling mud. Thermal spallation not only in principle enables much faster rates of penetration than traditional rotary drilling, but is also contact-less, which significantly reduces the long tripping times associated with conventional rotary head drilling. We present numerical simulations investigating the influence of rock heterogeneities on the thermal spallation process. Special emphasis is put on different mineral compositions, stress regimes, and heat sources.

Tidal Heating in Multilayered Terrestrial Exoplanets

NASA Technical Reports Server (NTRS)

Henning, Wade G.; Hurford, Terry

2014-01-01

The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R(sub E) is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

Microstructure, texture and colour development during crust formation on whole muscle chicken fillets.

PubMed

Barbut, S

2013-01-01

1. The development of crust during a 22-min period was evaluated in an oven, and in previously cooked-in-bag products (no crust) placed in an oven for 10 min. The oven-roasted products started to develop a thin (2-4 μm) crust layer after 4 min. At that point, the colour of the fillets turned white but no browning was observed. As roasting time increased, crust thickness and shear force increased, the product turned brown and eventually black at certain spots. 2. Light microscopy revealed the shrinking of muscle fibres close to the surface, as they also lost water. At a certain point, tears between the different layers started to appear. The inner muscle fibres also progressively shrank and the spaces between them increased. Microscopy of cook-in-bag products revealed no crust formation during heating. Upon moving to the oven, crust started to form but was much faster compared with the other products. 3. Cook-in-the-bag samples showed a higher rate of cook loss during the first 12 min (to internal 70°C) compared with oven heating. This could have been due to the fast heating rate in water and/or no crust formation. 4. White colour was fully formed on water-cooked fillets within 2 min (L* = 83), while it was gradually forming on oven-roasted samples (max L* of 79 after 12 min). 5. Shear force measurements showed an increase in both treatments up to 18 min, with a decrease thereafter (when dry crust started to crack).

Seasonal warming of the Middle Atlantic Bight Cold Pool

NASA Astrophysics Data System (ADS)

Lentz, S. J.

2017-02-01

The Cold Pool is a 20-60 m thick band of cold, near-bottom water that persists from spring to fall over the midshelf and outer shelf of the Middle Atlantic Bight (MAB) and Southern Flank of Georges Bank. The Cold Pool is remnant winter water bounded above by the seasonal thermocline and offshore by warmer slope water. Historical temperature profiles are used to characterize the average annual evolution and spatial structure of the Cold Pool. The Cold Pool gradually warms from spring to summer at a rate of order 1°C month-1. The warming rate is faster in shallower water where the Cold Pool is thinner, consistent with a vertical turbulent heat flux from the thermocline to the Cold Pool. The Cold Pool warming rate also varies along the shelf; it is larger over Georges Bank and smaller in the southern MAB. The mean turbulent diffusivities at the top of the Cold Pool, estimated from the spring to summer mean heat balance, are an order of magnitude larger over Georges Bank than in the southern MAB, consistent with much stronger tidal mixing over Georges Bank than in the southern MAB. The stronger tidal mixing causes the Cold Pool to warm more rapidly over Georges Bank and the eastern New England shelf than in the New York Bight or southern MAB. Consequently, the coldest Cold Pool water is located in the New York Bight from late spring to summer.

Motion sickness increases the risk of accidental hypothermia.

PubMed

Nobel, Gerard; Eiken, Ola; Tribukait, Arne; Kölegård, Roger; Mekjavic, Igor B

2006-09-01

Motion sickness (MS) has been found to increase body-core cooling during immersion in 28 degrees C water, an effect ascribed to attenuation of the cold-induced peripheral vasoconstriction (Mekjavic et al. in J Physiol 535(2):619-623, 2001). The present study tested the hypothesis that a more profound cold stimulus would override the MS effect on peripheral vasoconstriction and hence on the core cooling rate. Eleven healthy subjects underwent two separate head-out immersions in 15 degrees C water. In the control trial (CN), subjects were immersed after baseline measurements. In the MS-trial, subjects were rendered motion sick prior to immersion, by using a rotating chair in combination with a regimen of standardized head movements. During immersion in the MS-trial, subjects were exposed to an optokinetic stimulus (rotating drum). At 5-min intervals subjects rated their temperature perception, thermal comfort and MS discomfort. During immersion mean skin temperature, rectal temperature, the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (DeltaTff), oxygen uptake and heart rate were recorded. In the MS-trial, rectal temperature decreased substantially faster (33%, P < 0.01). Also, the DeltaTff response, an index of peripheral vasomotor tone, as well as the oxygen uptake, indicative of the shivering response, were significantly attenuated (P < 0.01 and P < 0.001, respectively) by MS. Thus, MS may predispose individuals to hypothermia by enhancing heat loss and attenuating heat production. This might have significant implications for survival in maritime accidents.

Modelling of a Convecting, Crystallizing, and Replenished Diopside-Anorthite Axial Magma Chamber beneath Mid Ocean Ridges

NASA Astrophysics Data System (ADS)

Lowell, R. P.; Lata, C.

2016-12-01

The aim of this work is to model heat output from a cooling, convective, crystallizing, and replenished basaltic magma sill, representing an axial magma lens (AML) at mid oceanic ridges. As a simplified version of basaltic melt, we have assumed the melt to be a two-component eutectic system composed of diopside and anorthite. Convective vigor is expressed through the Rayleigh number and heat flux is scaled through a classical relationship between the Rayleigh number and Nusselt number, where the temperature difference driving the convective heat flux is derived from a "viscous" temperature scale reflecting the strong temperature dependent viscosity of the system. Viscosity is modeled as a function of melt composition and temperature using the Tammann-Vogel-Fulcher equation, with parameters fit to the values of observed viscosities along the diopside-anorthite liquidus. It was observed for the un-replenished case, in which crystals fall rapidly to the floor of the AML, model results show that the higher initial concentration of diopside, the more vigorous the convection and the faster the rate of crystallization and decay of heat output. Replenishment of the AML accompanied by modest thickening of the melt layer stabilizes the heat output at values similar to those observed at ridge-axis hydrothermal systems. This study is an important step forward in quantitative understanding of thermal evolution of the axial magma lens at a mid-ocean ridge and the corresponding effect on high-temperature hydrothermal systems. Future work could involve improved replenishment mechanisms, more complex melts, and direct coupling with hydrothermal circulation models.

Auditory perceptual simulation: Simulating speech rates or accents?

PubMed

Zhou, Peiyun; Christianson, Kiel

2016-07-01

When readers engage in Auditory Perceptual Simulation (APS) during silent reading, they mentally simulate characteristics of voices attributed to a particular speaker or a character depicted in the text. Previous research found that auditory perceptual simulation of a faster native English speaker during silent reading led to shorter reading times that auditory perceptual simulation of a slower non-native English speaker. Yet, it was uncertain whether this difference was triggered by the different speech rates of the speakers, or by the difficulty of simulating an unfamiliar accent. The current study investigates this question by comparing faster Indian-English speech and slower American-English speech in the auditory perceptual simulation paradigm. Analyses of reading times of individual words and the full sentence reveal that the auditory perceptual simulation effect again modulated reading rate, and auditory perceptual simulation of the faster Indian-English speech led to faster reading rates compared to auditory perceptual simulation of the slower American-English speech. The comparison between this experiment and the data from Zhou and Christianson (2016) demonstrate further that the "speakers'" speech rates, rather than the difficulty of simulating a non-native accent, is the primary mechanism underlying auditory perceptual simulation effects. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultrafast Formation of ZnO Nanorods via Seed-Mediated Microwave Assisted Hydrolysis Process

NASA Astrophysics Data System (ADS)

Tan, S. T.; Umar, A. A.; Yahaya, M.; Yap, C. C.; Salleh, M. M.

2013-04-01

One dimensional (1D) zinc oxide, ZnO nanostructures have shown promising results for usage in photodiode and optoelectronic device due to their high surface area. Faster and conventional method for synthesis ZnO nanorods has become an attention for researcher today. In this paper, ZnO nanorods have been successfully synthesized via two-step process, namely alcothermal seeding and seed-mediated microwave hydrolysis process. In typical process, the ZnO nanoseeds were grown in the growth solution that contained equimolar (0.04 M) of zinc nitrate hexahydrate, Zn (NO3).6H2O and hexamethylenetetramine, HMT. The growth process was carried inside the inverted microwave within 5- 20 s. The effect of growth parameters (i.e. concentration, microwave power, time reaction) upon the modification of ZnO morphology was studied. ZnO nanostructures were characterized by Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). The densities of nanorods were evaluated by the Image J analysis. It was found that the morphology (e.g. shape and size) of nanostructures has changed drastically with the increment of growth solution concentration. The density of ZnO nanorods was proven to increase with the increasing of reaction time and microwave power. We hypothesize that the microwave power might enhance the rate of nucleation and promote the faster nanostructure growth as compared with the normal heating condition due to the superheating phenomenon. This method might promote a new and faster alternative way in nanostructure growth which can be applied in currently existing application.

Stimulated electronic transition concept for an erasable optical memory

NASA Technical Reports Server (NTRS)

Albin, Sacharia; Satira, James D.; Livingston, David L.; Shull, Thomas A.

1992-01-01

A new concept for an erasable optical memory is demonstrated using stimulated electronic transition (SET). Large bandgap semiconductors are suitable materials for the SET medium. The properties of MgS:Eu,Sm and SrS:Eu,Sm as possible media for the SET process are investigated. Quantum storage is achieved in the form of charges in deep levels in the medium and stimulated radiative recombination is used as the reading process. Unlike magneto-optic (M-O) and phase change (PC) processes, optical writing, reading and erasing are achieved without localized heating. The SET process will have an inherently faster data transfer rate and a higher storage density, and the medium will be more durable than the M-O and PC media. A possible application of the SET process in neural networks is also discussed.

Separation of certain carboxylic acids utilizing cation exchange membranes

DOEpatents

Chum, H.L.; Sopher, D.W.

1983-05-09

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100/sup 0/C and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Separation of certain carboxylic acids utilizing cation exchange membranes

DOEpatents

Chum, Helena L.; Sopher, David W.

1984-01-01

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Effect of Sodium Chloride on α-Dicarbonyl Compound and 5-Hydroxymethyl-2-furfural Formations from Glucose under Caramelization Conditions: A Multiresponse Kinetic Modeling Approach.

PubMed

Kocadağlı, Tolgahan; Gökmen, Vural

2016-08-17

This study aimed to investigate the kinetics of α-dicarbonyl compound formation in glucose and glucose-sodium chloride mixture during heating under caramelization conditions. Changes in the concentrations of glucose, fructose, glucosone, 1-deoxyglucosone, 3-deoxyglucosone, 3,4-dideoxyglucosone, 5-hydroxymethyl-2-furfural (HMF), glyoxal, methylglyoxal, and diacetyl were determined. A comprehensive reaction network was built, and the multiresponse model was compared to the experimentally observed data. Interconversion between glucose and fructose became 2.5 times faster in the presence of NaCl at 180 and 200 °C. The effect of NaCl on the rate constants of α-dicarbonyl compound formation varied across the precursor and the compound itself and temperature. A decrease in rate constants of 3-deoxyglucosone and 1-deoxyglucosone formations by the presence of NaCl was observed. HMF formation was revealed to be mainly via isomerization to fructose and dehydration over cyclic intermediates, and the rate constants increase 4-fold in the presence of NaCl.

Innovative heating of large-size automotive Li-ion cells

NASA Astrophysics Data System (ADS)

Yang, Xiao-Guang; Liu, Teng; Wang, Chao-Yang

2017-02-01

Automotive Li-ion cells are becoming much larger and thicker in order to reduce the cell count and increase battery reliability, posing a new challenge to battery heating from the cold ambient due to poor through-plane heat transfer across a cell's multiple layers of electrodes and separators. In this work, widely used heating methods, including internal heating using the cell's resistance and external heating by resistive heaters, are compared with the recently developed self-heating Li-ion battery (SHLB) with special attention to the heating speed and maximum local temperature critical to battery safety. Both conventional methods are found to be slow due to low heating power required to maintain battery safety. The heating power in the external heating method is limited by the risk of local over-heating, in particular for thick cells. As a result, the external heating method is restricted to ∼20 min slow heating for a 30 °C temperature rise. In contrast, the SHLB is demonstrated to reach a heating speed of 1-2 °C/sec, ∼40 times faster for large-size thick cells, with nearly 100% heating efficiency and spatially uniform heating free from safety concerns.

The effects of sex-biased gene expression and X-linkage on rates of sequence evolution in Drosophila.

PubMed

Campos, José Luis; Johnston, Keira; Charlesworth, Brian

2017-12-08

A faster rate of adaptive evolution of X-linked genes compared with autosomal genes (the faster-X effect) can be caused by the fixation of recessive or partially recessive advantageous mutations. This effect should be largest for advantageous mutations that affect only male fitness, and least for mutations that affect only female fitness. We tested these predictions in Drosophila melanogaster by using coding and functionally significant non-coding sequences of genes with different levels of sex-biased expression. Consistent with theory, nonsynonymous substitutions in most male-biased and unbiased genes show faster adaptive evolution on the X. However, genes with very low recombination rates do not show such an effect, possibly as a consequence of Hill-Robertson interference. Contrary to expectation, there was a substantial faster-X effect for female-biased genes. After correcting for recombination rate differences, however, female-biased genes did not show a faster X-effect. Similar analyses of non-coding UTRs and long introns showed a faster-X effect for all groups of genes, other than introns of female-biased genes. Given the strong evidence that deleterious mutations are mostly recessive or partially recessive, we would expect a slower rate of evolution of X-linked genes for slightly deleterious mutations that become fixed by genetic drift. Surprisingly, we found little evidence for this after correcting for recombination rate, implying that weakly deleterious mutations are mostly close to being semidominant. This is consistent with evidence from polymorphism data, which we use to test how models of selection that assume semidominance with no sex-specific fitness effects may bias estimates of purifying selection. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Gas Hydrate Storage of Natural Gas

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

Rudy Rogers; John Etheridge

2006-03-31

Environmental and economic benefits could accrue from a safe, above-ground, natural-gas storage process allowing electric power plants to utilize natural gas for peak load demands; numerous other applications of a gas storage process exist. A laboratory study conducted in 1999 to determine the feasibility of a gas-hydrates storage process looked promising. The subsequent scale-up of the process was designed to preserve important features of the laboratory apparatus: (1) symmetry of hydrate accumulation, (2) favorable surface area to volume ratio, (3) heat exchanger surfaces serving as hydrate adsorption surfaces, (4) refrigeration system to remove heat liberated from bulk hydrate formation, (5)more » rapid hydrate formation in a non-stirred system, (6) hydrate self-packing, and (7) heat-exchanger/adsorption plates serving dual purposes to add or extract energy for hydrate formation or decomposition. The hydrate formation/storage/decomposition Proof-of-Concept (POC) pressure vessel and supporting equipment were designed, constructed, and tested. This final report details the design of the scaled POC gas-hydrate storage process, some comments on its fabrication and installation, checkout of the equipment, procedures for conducting the experimental tests, and the test results. The design, construction, and installation of the equipment were on budget target, as was the tests that were subsequently conducted. The budget proposed was met. The primary goal of storing 5000-scf of natural gas in the gas hydrates was exceeded in the final test, as 5289-scf of gas storage was achieved in 54.33 hours. After this 54.33-hour period, as pressure in the formation vessel declined, additional gas went into the hydrates until equilibrium pressure/temperature was reached, so that ultimately more than the 5289-scf storage was achieved. The time required to store the 5000-scf (48.1 hours of operating time) was longer than designed. The lower gas hydrate formation rate is attributed to a lower heat transfer rate in the internal heat exchanger than was designed. It is believed that the fins on the heat-exchanger tubes did not make proper contact with the tubes transporting the chilled glycol, and pairs of fins were too close for interior areas of fins to serve as hydrate collection sites. A correction of the fabrication fault in the heat exchanger fin attachments could be easily made to provide faster formation rates. The storage success with the POC process provides valuable information for making the process an economically viable process for safe, aboveground natural-gas storage.« less

Effect of thermal treatments on the wear behaviour of duplex stainless steels

NASA Astrophysics Data System (ADS)

Fargas, G.; Mestra, A.; Anglada, M.; Mateo, A.

2009-09-01

Duplex stainless steel (DSS) is a family of steels characterized by two-phase microstructure with similar percentages of ferrite (α) and austenite (γ).Their attractive combination of mechanical properties and corrosion resistance has increased its use in last decades in the marine and petrochemical industries. Nevertheless, an inappropriate heat treatment can induce the precipitation of secondary phases which affect directly their mechanical properties and corrosion resistance. There are few works dealing with the influence of heat treatments on wear behaviour of these steels in the literature. For instances, this paper aims to determine wear kinetic and sliding wear volume developed as a function of heat treatment conditions. Therefore, the samples were heat treated from 850 °C to 975 °C before sliding wear tests. These wear tests were carried out using ball on disk technique at constant sliding velocity and different sliding distances. Two methodologies were used to calculate the wear volume: weight loss and area measurement using a simplified contact model. Microstructural observations showed the presence of sigma phase for all studied conditions. The formation kinetics of this phase is faster at 875 °C and decrease at higher temperatures. Results related to wear showed that the hardness introduced due to the presence of sigma phase plays an important role on wear behaviour for this steel. It was observed also that wear rates decreased when increasing the percentage of sigma phase on the microstructure.

Modeling of biomass to hydrogen via the supercritical water pyrolysis process

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

Divilio, R.J.

1998-08-01

A heat transfer model has been developed to predict the temperature profile inside the University of Hawaii`s Supercritical Water Reactor. A series of heat transfer tests were conducted on the University of Hawaii`s apparatus to calibrate the model. Results of the model simulations are shown for several of the heat transfer tests. Tests with corn starch and wood pastes indicated that there are substantial differences between the thermal properties of the paste compared to pure water, particularly near the pseudo critical temperature. The assumption of constant thermal diffusivity in the temperature range of 250 to 450 C gave a reasonablemore » prediction of the reactor temperatures when paste is being fed. A literature review is presented for pyrolysis of biomass in water at elevated temperatures up to the supercritical range. Based on this review, a global reaction mechanism is proposed. Equilibrium calculations were performed on the test results from the University of Hawaii`s Supercritical Water Reactor when corn starch and corn starch and wood pastes were being fed. The calculations indicate that the data from the reactor falls both below and above the equilibrium hydrogen concentrations depending on test conditions. The data also indicates that faster heating rates may be beneficial to the hydrogen yield. Equilibrium calculations were also performed to examine the impact of wood concentration on the gas mixtures produced. This calculation showed that increasing wood concentrations favors the formation of methane at the expense of hydrogen.« less

Investigations of plasmoid reconnection in the presence of strong guide fields in CHI plasma start-up on HIST

NASA Astrophysics Data System (ADS)

Nagata, Masayoshi; Fujita, Akihiro; Ibragi, Youhei; Matsui, Takahiro; Kikuchi, Yusuke; Fukumoto, Naoyuki; Kanki, Takashi

2017-10-01

Plasmoid magnetic reconnections have been examined in the Coaxial Helicity Injection (CHI) experiments on HIST. Magnetic reconnections are required for the formation of closed flux surfaces in the transient-CHI start-up plasmas. So far, we have observed formation of plasmoids inside an elongated current layer to create the multiple X-points during the CHI process. According to the MHD simulation by F. Ebrahimi and R. Raman, the reconnection rate based on the plasmoid instability is faster than that by Sweet-Parker (S-P) model. To estimate the Lundquist number S number, we have measured spatial profiles of magnetic field strength, electron density and temperature in the current layer. In this meeting, we will present the effect of the guide (toroidal) magnetic field and mass (H, D and He) on the current layer thickness and reconnection rates of plasmoids. It is found that behavior of plasmoids is synchronized with Ion Doppler temperature, leading to ion heating.

Body cooling in human males by cold-water immersion after vigorous exercise.

PubMed

McDonald, A; Goode, R C; Livingstone, S D; Duffin, J

1984-03-01

Five male subjects were immersed to neck level in a whole-body water calorimeter (water temperature 19 degrees C) on two occasions. One immersion was preceded by 30 min of exercise on a treadmill at 80% of the subjects' maximum heart rate, while the other was preceded by no exercise (control). Ventilation, oxygen consumption, hand-grip strength, and heat loss (measured by calorimetry) results showed no significant differences between resting and exercise trials. Minute ventilation and oxygen consumption increased during the immersion but the magnitude of the increase varied among subjects. There was a significant decrease is isometric hand-grip strength after 30 min of immersion. Rectal temperatures fell faster (0.031 degree C +/- 0.004 degree C/min) for exercised subjects than for controls (0.019 degree C +/- 0.005 degree C/min) between 10 and 45 min of immersion (P less than 0.01). It appears that vigorous preimmersion exercise may shorten survival time in cold water due to an increase in cooling rate.

Can Arctic sea-ice melt be explained by atmospheric meridional transports? (Invited)

NASA Astrophysics Data System (ADS)

Tjernstrom, M. K.; Graversen, R. G.

2010-12-01

The Arctic summer sea ice is melting away at an alarming rate, and it is now expected that an principally sea-ice free Arctic summer will occur much earlier than projected by the IPCC AR4 models. At the same time Arctic near-surface temperatures are rising at a rate much faster than the global average. The processes responsible for these changes are debated and many claim that local feedbacks, such as the surface albedo feedback, are the main culprits while other argue that remote effects, such as atmospheric circulation changes on synoptic and hemispheric scales, are the most important. We will explore the effects of the meridional transport by synoptic and larger scale atmospheric circulation on recent changes, using reanalysis data. It will be illustarated how this transport can contribute significant amounts of sensible heat, but also of atmospheric moisture such that local cloud feedbacks as well as the direct greenhouse effect of the water vapor contributes significantly to the surface energy balance over the Arctic polar cap.

Colder environments did not select for a faster metabolism during experimental evolution of Drosophila melanogaster.

PubMed

Alton, Lesley A; Condon, Catriona; White, Craig R; Angilletta, Michael J

2017-01-01

The effect of temperature on the evolution of metabolism has been the subject of debate for a century; however, no consistent patterns have emerged from comparisons of metabolic rate within and among species living at different temperatures. We used experimental evolution to determine how metabolism evolves in populations of Drosophila melanogaster exposed to one of three selective treatments: a constant 16°C, a constant 25°C, or temporal fluctuations between 16 and 25°C. We tested August Krogh's controversial hypothesis that colder environments select for a faster metabolism. Given that colder environments also experience greater seasonality, we also tested the hypothesis that temporal variation in temperature may be the factor that selects for a faster metabolism. We measured the metabolic rate of flies from each selective treatment at 16, 20.5, and 25°C. Although metabolism was faster at higher temperatures, flies from the selective treatments had similar metabolic rates at each measurement temperature. Based on variation among genotypes within populations, heritable variation in metabolism was likely sufficient for adaptation to occur. We conclude that colder or seasonal environments do not necessarily select for a faster metabolism. Rather, other factors besides temperature likely contribute to patterns of metabolic rate over thermal clines in nature. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Geochemistry of Dissolved Gases in the Hypersaline Orca Basin.

DTIC Science & Technology

1980-12-01

brine (",250%/o) is internally well mixed due to convective overturning, but transfer across the brine-sea water interface is controlled by- molecular ...diffusion. With a molecular diffusivity of l0-cm . sec- , it will take 10 years for all salts to diffuse fro’i-te-basin. Heat diffuses faster than salt...trolled by molecular diffusion. With a molecular diffusivity of 10 cm sec , it will take 10 years for all salts to diffuse from the basin. Heat diffuses

Size and Velocity Characteristics of Droplets Generated by Thin Steel Slab Continuous Casting Secondary Cooling Air-Mist Nozzles

NASA Astrophysics Data System (ADS)

Minchaca M, J. I.; Castillejos E, A. H.; Acosta G, F. A.

2011-06-01

Direct spray impingement of high temperature surfaces, 1473 K to 973 K (1200 °C to 700 °C), plays a critical role in the secondary cooling of continuously cast thin steel slabs. It is known that the spray parameters affecting the local heat flux are the water impact flux w as well as the droplet velocity and size. However, few works have been done to characterize the last two parameters in the case of dense mists ( i.e., mists with w in the range of 2 to 90 L/m2s). This makes it difficult to rationalize how the nozzle type and its operating conditions must be selected to control the cooling process. In the present study, particle/droplet image analysis was used to determine the droplet size and velocity distributions simultaneously at various locations along the major axis of the mist cross section at a distance where the steel strand would stand. The measurements were carried out at room temperature for two standard commercial air-assisted nozzles of fan-discharge type operating over a broad range of conditions of practical interest. To achieve statistically meaningful samples, at least 6000 drops were analyzed at each location. Measuring the droplet size revealed that the number and volume frequency distributions were fitted satisfactorily by the respective log-normal and Nukiyama-Tanasawa distributions. The correlation of the parameters of the distribution functions with the water- and air-nozzle pressures allowed for reasonable estimation of the mean values of the size of the droplets generated. The ensemble of measurements across the mist axis showed that the relationship between the droplet velocity and the diameter exhibited a weak positive correlation. Additionally, increasing the water flow rate at constant air pressure caused a decrease in the proportion of the water volume made of finer droplets, whereas the volume proportion of faster droplets augmented until the water flow reached a certain value, after which it decreased. Diminishing the air-to-water flow rates ratio, particularly below 10, resulted in mists of bigger and slower droplets with low impinging Weber numbers. However, increasing the air pressure maintaining a constant water flow rate caused a greater proportion of finer and faster drops with Weber numbers greater than 80, which suggests an increased probability of wet drop contact with a hot surface that would intensify heat extraction.

High latitude artificial periodic irregularity observations with the upgraded EISCAT heating facility

NASA Astrophysics Data System (ADS)

Vierinen, Juha; Kero, Antti; Rietveld, Michael T.

2013-12-01

We present a recently developed ionospheric modification experiment that produces artificial periodic irregularities in the ionosphere and uses them to make observations of the spatiotemporal behaviour of the irregularities. In addition, the method can be used to measure Faraday rotation and vertical velocities. We also introduce a novel experiment that allows monitoring the formation of the irregularities during heating, in addition to observing their decay after heating. The first measurements indicate, contrary to existing theory, that the amplitude of the radar echoes from the periodic irregularities grows faster than they decay. We focus on the API effects in the D- and E-region of the ionosphere.

Ultra-low power operation of self-heated, suspended carbon nanotube gas sensors

NASA Astrophysics Data System (ADS)

Chikkadi, Kiran; Muoth, Matthias; Maiwald, Verena; Roman, Cosmin; Hierold, Christofer

2013-11-01

We present a suspended carbon nanotube gas sensor that senses NO2 at ambient temperature and recovers from gas exposure at an extremely low power of 2.9 μW by exploiting the self-heating effect for accelerated gas desorption. The recovery time of 10 min is two orders of magnitude faster than non-heated recovery at ambient temperature. This overcomes an important bottleneck for the practical application of carbon nanotube gas sensors. Furthermore, the method is easy to implement in sensor systems and requires no additional components, paving the way for ultra-low power, compact, and highly sensitive gas sensors.

Extracting the Electron-Ion Temperature Relaxation Rate from Ion Stopping Experiments

NASA Astrophysics Data System (ADS)

Grabowski, Paul E.; Frenje, Johan A.; Benedict, Lorin X.

2016-10-01

Direct measurement of i-e equilibration rates at ICF-relevant conditions is a big challenge, as it is difficult to differentiate from other sinks and sources of energy, such as heat conduction and pdV work. Another method is to use information from ion stopping experiments. Such experiments at the OMEGA laser have made precision energy loss measurements of fusion products at these conditions. Combined with the multimonochromatic x-ray imager technique, which gives temporally and spatially resolved electron temperature and density, we have a robust stopping experiment. We propose to use such stopping measurements to assess the i-e temperature relaxation rate, since both processes involve energy exchange between electrons and ions. We require that the fusion products are 1) much faster than the thermal ions so that i-i collisions are negligible compared to i-e collisions and 2) slower than the thermal electrons so that the stopping obeys a linear friction law. Then the Coulomb logarithms associated with ion stopping and i-e temperature relaxation rate are identical and a measurement of the former provides the latter. Prepared by LLNL under Contract DE-AC52-07NA27344.

Necessity of Removing American Football Uniforms From Humans With Hyperthermia Before Cold-Water Immersion

PubMed Central

Miller, Kevin C.; Long, Blaine C.; Edwards, Jeffrey

2015-01-01

Context  The National Athletic Trainers' Association and the American College of Sports Medicine have recommended removing American football uniforms from athletes with exertional heat stroke before cold-water immersion (CWI) based on the assumption that the uniform impedes rectal temperature (Trec) cooling. Few experimental data exist to verify or disprove this assumption and the recommendations. Objectives  To compare CWI durations, Trec cooling rates, thermal sensation, intensity of environmental symptoms, and onset of shivering when hyperthermic participants wore football uniforms during CWI or removed the uniforms immediately before CWI. Design  Crossover study. Setting  Laboratory. Patients or Other Participants  Eighteen hydrated, physically active men (age = 22 ± 2 years, height = 182.5 ± 6.1 cm, mass = 85.4 ± 13.4 kg, body fat = 11% ± 5%, body surface area = 2.1 ± 0.2 m2) volunteered. Intervention(s)  On 2 days, participants exercised in the heat (approximately 40°C, approximately 40% relative humidity) while wearing a full American football uniform (shoes; crew socks; undergarments; shorts; game pants; undershirt; shoulder pads; jersey; helmet; and padding over the thighs, knees, hips, and tailbone [PADS]) until Trec reached 39.5°C. Next, participants immersed themselves in water that was approximately 10°C while wearing either undergarments, shorts, and crew socks (NOpads) or PADS without shoes until Trec reached 38°C. Main Outcome Measure(s)  The CWI duration (minutes) and Trec cooling rates (°C/min). Results  Participants had similar exercise times (NOpads = 40.8 ± 4.9 minutes, PADS = 43.2 ± 4.1 minutes; t17 = 2.0, P = .10), hypohydration levels (NOpads = 1.5% ± 0.3%, PADS = 1.6% ± 0.4%; t17 = 1.3, P = .22), and thermal-sensation ratings (NOpads = 7.2 ± 0.3, PADS = 7.1 ± 0.5; P > .05) before CWI. The CWI duration (median [interquartile range]; NOpads = 6.0 [5.4] minutes, PADS = 7.3 [9.8] minutes; z = 2.3, P = .01) and Trec cooling rates (NOpads = 0.28°C/min ± 0.14°C/min, PADS = 0.21°C/min ± 0.11°C/min; t17 = 2.2, P = .02) differed between uniform conditions. Conclusions  Whereas participants cooled faster in NOpads, we still considered the PADS cooling rate to be acceptable (ie, >0.16°C/min). Therefore, if clinicians experience difficulty removing PADS or CWI treatment is delayed, they may immerse fully equipped hyperthermic football players in CWI and maintain acceptable Trec cooling rates. Otherwise, PADS should be removed preimmersion to ensure faster body core temperature cooling. PMID:26678288

Predicting clinical decline in progressive agrammatic aphasia and apraxia of speech.

PubMed

Whitwell, Jennifer L; Weigand, Stephen D; Duffy, Joseph R; Clark, Heather M; Strand, Edythe A; Machulda, Mary M; Spychalla, Anthony J; Senjem, Matthew L; Jack, Clifford R; Josephs, Keith A

2017-11-28

To determine whether baseline clinical and MRI features predict rate of clinical decline in patients with progressive apraxia of speech (AOS). Thirty-four patients with progressive AOS, with AOS either in isolation or in the presence of agrammatic aphasia, were followed up longitudinally for up to 4 visits, with clinical testing and MRI at each visit. Linear mixed-effects regression models including all visits (n = 94) were used to assess baseline clinical and MRI variables that predict rate of worsening of aphasia, motor speech, parkinsonism, and behavior. Clinical predictors included baseline severity and AOS type. MRI predictors included baseline frontal, premotor, motor, and striatal gray matter volumes. More severe parkinsonism at baseline was associated with faster rate of decline in parkinsonism. Patients with predominant sound distortions (AOS type 1) showed faster rates of decline in aphasia and motor speech, while patients with segmented speech (AOS type 2) showed faster rates of decline in parkinsonism. On MRI, we observed trends for fastest rates of decline in aphasia in patients with relatively small left, but preserved right, Broca area and precentral cortex. Bilateral reductions in lateral premotor cortex were associated with faster rates of decline of behavior. No associations were observed between volumes and decline in motor speech or parkinsonism. Rate of decline of each of the 4 clinical features assessed was associated with different baseline clinical and regional MRI predictors. Our findings could help improve prognostic estimates for these patients. © 2017 American Academy of Neurology.

Variation in promiscuity and sexual selection drives avian rate of Faster-Z evolution.

PubMed

Wright, Alison E; Harrison, Peter W; Zimmer, Fabian; Montgomery, Stephen H; Pointer, Marie A; Mank, Judith E

2015-03-01

Higher rates of coding sequence evolution have been observed on the Z chromosome relative to the autosomes across a wide range of species. However, despite a considerable body of theory, we lack empirical evidence explaining variation in the strength of the Faster-Z Effect. To assess the magnitude and drivers of Faster-Z Evolution, we assembled six de novo transcriptomes, spanning 90 million years of avian evolution. Our analysis combines expression, sequence and polymorphism data with measures of sperm competition and promiscuity. In doing so, we present the first empirical evidence demonstrating the positive relationship between Faster-Z Effect and measures of promiscuity, and therefore variance in male mating success. Our results from multiple lines of evidence indicate that selection is less effective on the Z chromosome, particularly in promiscuous species, and that Faster-Z Evolution in birds is due primarily to genetic drift. Our results reveal the power of mating system and sexual selection in shaping broad patterns in genome evolution. © 2015 John Wiley & Sons Ltd.

Drying and color characteristics of coriander foliage using convective thin-layer and microwave drying.

PubMed

Shaw, Mark; Meda, Venkatesh; Tabil, Lope; Opoku, Anthony

2007-01-01

Heat sensitive properties (aromatic, medicinal, color) provide herbs and spices with their high market value. In order to prevent extreme loss of heat sensitive properties when drying herbs, they are normally dried at low temperatures for longer periods of time to preserve these sensory properties. High energy consumption often results from drying herbs over a long period. Coriander (Coriandrum sativum L., Umbelliferae) was dehydrated in two different drying units (thin layer convection and microwave dryers) in order to compare the drying and final product quality (color) characteristics. Microwave drying of the coriander foliage was faster than convective drying. The entire drying process took place in the falling rate period for both microwave and convective dried samples. The drying rate for the microwave dried samples ranged from 42.3 to 48.2% db/min and that of the convective dried samples ranged from 7.1 to 12.5% db/min. The fresh sample color had the lowest L value at 26.83 with higher L values for all dried samples. The results show that convective thin layer dried coriander samples exhibited a significantly greater color change than microwave dried coriander samples. The color change index values for the microwave dried samples ranged from 2.67 to 3.27 and that of the convective dried samples varied from 4.59 to 6.58.

A description of an ‘obesogenic’ eating style that promotes higher energy intake and is associated with greater adiposity in 4.5 year-old children: Results from the GUSTO cohort

PubMed Central

Fogel, Anna; Goh, Ai Ting; Fries, Lisa R.; Sadananthan, Suresh Anand; Velan, S. Sendhil; Michael, Navin; Tint, Mya Thway; Fortier, Marielle Valerie; Chan, Mei Jun; Toh, Jia Ying; Chong, Yap-Seng; Tan, Kok Hian; Yap, Fabian; Shek, Lynette P.; Meaney, Michael J.; Broekman, Birit F. P.; Lee, Yung Seng; Godfrey, Keith M.; Chong, Mary Foong Fong; Forde, Ciarán G.

2017-01-01

Recent findings confirm that faster eating rates support higher energy intakes within a meal and are associated with increased body weight and adiposity in children. The current study sought to identify the eating behaviours that underpin faster eating rates and energy intake in children, and to investigate their variations by weight status and other individual differences. Children (N=386) from the Growing Up in Singapore towards Healthy Outcomes (GUSTO) cohort took part in a video-recorded ad libitum lunch at 4.5 years of age to measure acute energy intake. Videos were coded for three eating behaviours (bites, chews and swallows) to derive a measure of eating rate (g/min) and measures of eating microstructure: eating rate (g/min), total oral exposure (minutes), average bite size (g/bite), chews per gram, oral exposure per bite (seconds), total bites and proportion of active to total mealtime. Children’s BMIs were calculated and a subset of children underwent MRI scanning to establish abdominal adiposity. Children were grouped into faster and slower eaters, and into healthy and overweight groups to compare their eating behaviours. Results demonstrate that faster eating rates were correlated with larger average bite size (r=0.55, p<0.001), fewer chews per gram (r=-0.71, p<0.001) and shorter oral exposure time per bite (r=-0.25, p<0.001), and with higher energy intakes (r=0.61, p<0.001). Children with overweight and higher adiposity had faster eating rates (p<0.01) and higher energy intakes (p<0.01), driven by larger bite sizes (p<0.05). Eating behaviours varied by sex, ethnicity and early feeding regimes, partially attributable to BMI. We propose that these behaviours describe an ‘obesogenic eating style’ that is characterised by faster eating rates, achieved through larger bites, reduced chewing and shorter oral exposure time. This obesogenic eating style supports acute energy intake within a meal and is more prevalent among, though not exclusive to, children with overweight. PMID:28213204

Bottom-up heating method for producing polyethylene lunar concrete in lunar environment

NASA Astrophysics Data System (ADS)

Lee, Jaeho; Ann, Ki Yong; Lee, Tai Sik; Mitikie, Bahiru Bewket

2018-07-01

The Apollo Program launched numerous missions to the Moon, Earth's nearest and only natural satellite. NASA is now planning new Moon missions as a first step toward human exploration of Mars and other planets. However, the Moon has an extreme environment for humans. In-situ resource utilization (ISRU) construction must be used on the Moon to build habitable structures. Previous studies on polymeric lunar concrete investigated top-down heating for stabilizing the surface. This study investigates bottom-up heating with manufacturing temperatures as low as 200 °C in a vacuum chamber that simulates the lunar environment. A maximum compressive strength of 5.7 MPa is attained; this is suitable for constructing habitable structures. Furthermore, the bottom-up heating approach achieves solidification two times faster than does the top-down heating approach.

The Structure of Working Memory Abilities across the Adult Life Span

PubMed Central

Hale, Sandra; Rose, Nathan S.; Myerson, Joel; Strube, Michael J; Sommers, Mitchell; Tye-Murray, Nancy; Spehar, Brent

2010-01-01

The present study addresses three questions regarding age differences in working memory: (1) whether performance on complex span tasks decreases as a function of age at a faster rate than performance on simple span tasks; (2) whether spatial working memory decreases at a faster rate than verbal working memory; and (3) whether the structure of working memory abilities is different for different age groups. Adults, ages 20–89 (n=388), performed three simple and three complex verbal span tasks and three simple and three complex spatial memory tasks. Performance on the spatial tasks decreased at faster rates as a function of age than performance on the verbal tasks, but within each domain, performance on complex and simple span tasks decreased at the same rates. Confirmatory factor analyses revealed that domain-differentiated models yielded better fits than models involving domain-general constructs, providing further evidence of the need to distinguish verbal and spatial working memory abilities. Regardless of which domain-differentiated model was examined, and despite the faster rates of decrease in the spatial domain, age group comparisons revealed that the factor structure of working memory abilities was highly similar in younger and older adults and showed no evidence of age-related dedifferentiation. PMID:21299306

Influence of a Pre-Exercise Glycerol Hydration Beverage on Performance and Physiologic Function During Mountain-Bike Races in the Heat

PubMed Central

Wingo, Jonathan E.; Berger, Erik M.; Dellis, William O.; Knight, J. Chad; McClung, Joseph M.

2004-01-01

Objective: To determine if pre-exercise hydration with and without glycerol differentially affects physiologic and performance responses during mountain-bike races in the heat. Design and Setting: Testing (random, crossover, double-blind design) included the following 3 treatments administered in conjunction with a 30-mile mountain-bike race consisting of three 10-mile (16-km) loops: (1) no water during exercise (NE): water consumed before the race and no water consumed during the race, (2) glycerol (G): mixture of water and glycerol consumed before the race and water via 2 water bottles consumed during the race, and (3) water (W): water consumed before the race and water via 2 water bottles consumed during the race. Subjects stopped for 8 minutes after each 10-mile loop for collection of data. Subjects: Twelve heat-acclimated male mountain bikers with age = 24.5 ± 1.1 years, percentage of body fat = 14.3 ± 1.0%, mass = 76.9 ± 1.9 kg, height = 179 ± 2 cm. Measurements: We measured body weight, percentage of body fat, rectal temperature, blood lactate, blood glucose, urine volume, urine color, urine specific gravity, thirst sensation, thermal sensation, rating of perceived exertion, fluid consumption, heart rate, and sweat rate. Each subject completed the Environmental Symptoms Questionnaire. Results: The G trial was less dehydrated than the NE and W trials postexercise. Pre-exercise urine volume was less in the G trial than in the NE and W trials, and postexercise thirst was less in the G trial than the NE and W trials. Postexercise Environmental Symptoms Questionnaire scores were lower in the G trial than the NE or W trials. It is noteworthy that, although not significant, the G trial performed 5 minutes faster on loop 3 than the NE and W trials. Conclusions: Lower Environmental Symptoms Questionnaire scores and percentage of dehydration may indicate decreased signs and symptoms of heat strain in the G trial. Based on the NE trial performance, adequate pre-exercise hydration, even without glycerol, may limit the detrimental effects of dehydration. PMID:15173869

Role of climate change in reforestation and nursery practices

Treesearch

Mary I. Williams; R. Kasten Dumroese

2014-01-01

Ecosystems have been adjusting to changes in climate over time, but projections are that future global climate will change at rates faster than that previously experienced in geologic time. It is not necessarily the amount of change, but rather this rate of change that is most threatening to plant species - the climate appears to be changing faster than plants can...

Comparing the responses of rumen ciliate protozoa and bacteria to excess carbohydrate.

PubMed

Teixeira, César R V; Lana, Rogério de Paula; Tao, Junyi; Hackmann, Timothy J

2017-06-01

When given excess carbohydrate, certain microbial species respond by storing energy (synthesizing reserve carbohydrate), but other species respond by dissipating the energy as heat (spilling energy). To determine the importance of these responses in the rumen microbial community, this study quantified the responses of mixed ciliate protozoa vs bacteria to glucose. We hypothesized that ciliates would direct more glucose to synthesis of reserve carbohydrate (and less to energy spilling) than would bacteria. Ciliates and bacteria were isolated from rumen fluid using filtration and centrifugation, resuspended in nitrogen-free buffer to limit growth, and dosed with 5 mM glucose. Compared with bacteria, ciliates consumed glucose >3-fold faster and synthesized reserve carbohydrate 4-fold faster. They incorporated 53% of glucose carbon into reserve carbohydrate-nearly double the value (27%) for bacteria. Energy spilling was not detected for ciliates, as all heat production (104%) was accounted by synthesis of reserve carbohydrate and endogenous metabolism. For bacteria, reserve carbohydrate and endogenous metabolism accounted for only 68% of heat production, and spilling was detected within 11 min of dosing glucose. These results suggest that ciliates alter the course of ruminal carbohydrate metabolism by outcompeting bacteria for excess carbohydrate, maximizing reserve carbohydrate synthesis, and minimizing energy spilling. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effect of Manual Brush Cleaning on Biomass and Community Structure of Microfouling Film Formed on Aluminum and Titanium Surfaces Exposed to Rapidly Flowing Seawater

PubMed Central

Nickels, Janet S.; Bobbie, Ronald J.; Lott, Dan F.; Martz, Robert F.; Benson, Peter H.; White, David C.

1981-01-01

Metals exposed to rapidly flowing seawater are fouled by microbes that increase heat transfer resistance. In this study, results of biochemical test methods quantitatively relating the biomass and community structure of the microfouling film on aluminum and titanium to heat transfer resistance across the metal surface during three cycles of free fouling and manual brushing showed that cleaning accelerates the rate of fouling measured as the loss of heat transfer efficiency and as microfouling film biomass. The results also showed that the rate of fouling, measured as an increase in heat transfer resistance, is faster on titanium than on aluminum but that the titanium surface is more readily cleaned. In three cycles of free fouling and cleaning with a stiff-bristle nylon brush, the free-fouling communities re-forming on aluminum became enriched in bacteria containing short-branched fatty acids as the cycling progressed. The free-fouling community on titanium revealed an increasingly diverse morphology under scanning electron microscopy that was enriched in a portion of the microeucaryotes. Brushing removed most of the biomass, but left a residual community that was relatively enriched in a portion of the bacterial assembly containing cyclopropane fatty acids on aluminum and in a more diverse community on the titanium surface. The residual communities left after cleaning of titanium revealed an increase in bacteria with short-branched fatty acids and in microeucaryotes as cleaning continued. No significant changes occurred in the residual microbial community structure left on aluminum with cleaning; it was, again, less diverse than that remaining on titanium. The residual communities secreted a twofold-larger amount of extracellular polymer, measured as the ratio of total organic carbon to lipid phosphate, than did the free-fouling community on both surfaces. Images PMID:16345798

Numerical and experimental study of thermal explosions in LX-10 and PBX 9501: Influence of thermal damage on deflagration processes

NASA Astrophysics Data System (ADS)

Tringe, J. W.; Kercher, J. R.; Springer, H. K.; Glascoe, E. A.; Levie, H. W.; Hsu, P.; Willey, T. M.; Molitoris, J. D.

2013-07-01

We employ in-situ flash x-ray imaging, together with a detailed multiphase convective burn model, to demonstrate how explosives' binder characteristics influence the burning processes in thermal explosions. Our study focuses on the HMX-based explosives LX-10 and PBX 9501. While the HMX (cyclotetramethylene-tetranitramine) crystallite size distributions for these two explosives are nearly identical before heating, our experiments and simulations indicate that after heating, variations result due to differences in binder composition. Post-ignition flash x-ray images reveal that the average density decreases at late times more rapidly in PBX 9501 than LX-10, suggesting a faster conductive burning rate in PBX-9501. Heated permeability measurements in LX-10 and PBX 9501 demonstrate that the binder system characteristics influence the evolution of connected porosity. Once ignited, connected porosity provides pathways for product gas heating ahead of the reaction front and additional surface area for burning, facilitating the transition from conductive to convective burning modes. A multiphase convective burn model implemented in the ALE3D code is used to better understand the influence on burn rates of material properties such as porosity and effective thermally damaged particle size. In this context, particles are defined as gas-impermeable binder-coated crystallites and agglomerations with a set of effective radii reff. Model results demonstrate quantitative agreement with containment wall velocity for confined PBX 9501 and LX-10, and qualitative agreement with density as a function of position in the burning explosive. The model predicts a decrease in post-ignition containment wall velocity with larger radii in reff. These experimental data and model results together provide insight into the initiation and propagation of the reaction wave that defines the convective burn front in HMX-based explosives, a necessary step toward predicting violence under a broad range of conditions.

Effect of acute heat stress and slaughter processing on poultry meat quality and postmortem carbohydrate metabolism.

PubMed

Wang, R H; Liang, R R; Lin, H; Zhu, L X; Zhang, Y M; Mao, Y W; Dong, P C; Niu, L B; Zhang, M H; Luo, X

2017-03-01

This study investigated the effects of acute heat stress and slaughter processing on poultry meat quality and carbohydrate metabolism. Broilers (200) were randomly divided into 2 groups receiving heat stress (HS; 36°C for one h), compared to a non-stressed control (C). At slaughter, each group was further divided into 2 groups for slaughter processing (L = laboratory; F = commercial factory). L group breasts were removed immediately after bleeding without carcass scalding or defeathering, and stored at 4°C. F group broilers were scalded (60°C, 45 s) after bleeding and defeathering. Then the breasts were removed and cooled in ice water until the core temperature was ≤4°C. Rates of Pectoralis core temperature and pH decline were changed by slaughter processing, but only HS affected ultimate pH in group L. HS muscles had higher L* values (P < 0.05) than controls at 24 h postmortem. Laboratory processing "hot-deboning" increased drip loss, which resulted in a lower cooked loss (P < 0.05). Postmortem glycolysis was affected only by HS. The speed of lactic acid accumulation and glycogen degradation was faster in the HS group than controls at 5 min postmortem. During storage the glycolysis rates were not different (P > 0.05). Sarcoplasmic protein solubility was higher in F processed birds (P < 0.05). HS decreased the solubility of myofibrillar and total protein in the L-slaughtered birds. Thus, HS caused a higher frequency of accelerated muscle glycolysis than controls. Factory processing (chilling) could not completely eliminate the effects of accelerated glycolysis caused by pre-slaughter HS. © 2016 Poultry Science Association Inc.

Forming Ganymede's grooves at smaller strain: Toward a self-consistent local and global strain history for Ganymede

NASA Astrophysics Data System (ADS)

Bland, Michael T.; McKinnon, William B.

2015-01-01

The ubiquity of tectonic features formed in extension, and the apparent absence of ones formed in contraction, has led to the hypothesis that Ganymede has undergone global expansion in its past. Determining the magnitude of such expansion is challenging however, and extrapolation of locally or regionally inferred strains to global scales often results in strain estimates that exceed those based on global constraints. Here we use numerical simulations of groove terrain formation to develop a strain history for Ganymede that is generally consistent at local, regional, and global scales. These simulations reproduce groove-like amplitudes, wavelengths, and average slopes at modest regional extensions (10-15%). The modest strains are more consistent with global constraints on Ganymede's expansion. Yet locally, we also find that surface strains can be much larger (30-60%) in the same simulations, consistent with observations of highly-extended impact craters. Thus our simulations satisfy both the smallest-scale and largest-scale inferences of strain on Ganymede. The growth rate of the topography is consistent with (or exceeds) predictions of analytical models, and results from the use of a non-associated plastic rheology that naturally permits localization of brittle failure (plastic strain) into linear fault-like shear zones. These fault-like zones are organized into periodically-spaced graben-like structures with stepped, steeply-dipping faults. As in previous work, groove amplitudes and wavelengths depend on both the imposed heat flux and surface temperature, but because our brittle strength increases with depth, we find (for the parameters explored) that the growth rate of topography is initially faster for lower heat flows. We observe a transition to narrow rifting for higher heat flows and larger strains, which is a potential pathway for breakaway margin or band formation.

Forming Ganymede’s grooves at smaller strain: Toward a self-consistent local and global strain history for Ganymede

USGS Publications Warehouse

Bland, Michael T.; McKinnon, W. B.

2015-01-01

The ubiquity of tectonic features formed in extension, and the apparent absence of ones formed in contraction, has led to the hypothesis that Ganymede has undergone global expansion in its past. Determining the magnitude of such expansion is challenging however, and extrapolation of locally or regionally inferred strains to global scales often results in strain estimates that exceed those based on global constraints. Here we use numerical simulations of groove terrain formation to develop a strain history for Ganymede that is generally consistent at local, regional, and global scales. These simulations reproduce groove-like amplitudes, wavelengths, and average slopes at modest regional extensions (10–15%). The modest strains are more consistent with global constraints on Ganymede’s expansion. Yet locally, we also find that surface strains can be much larger (30–60%) in the same simulations, consistent with observations of highly-extended impact craters. Thus our simulations satisfy both the smallest-scale and largest-scale inferences of strain on Ganymede. The growth rate of the topography is consistent with (or exceeds) predictions of analytical models, and results from the use of a non-associated plastic rheology that naturally permits localization of brittle failure (plastic strain) into linear fault-like shear zones. These fault-like zones are organized into periodically-spaced graben-like structures with stepped, steeply-dipping faults. As in previous work, groove amplitudes and wavelengths depend on both the imposed heat flux and surface temperature, but because our brittle strength increases with depth, we find (for the parameters explored) that the growth rate of topography is initially faster for lower heat flows. We observe a transition to narrow rifting for higher heat flows and larger strains, which is a potential pathway for breakaway margin or band formation.

The Automated Circulation Marketplace: Active and Heating Up.

ERIC Educational Resources Information Center

Matthews, Joseph R.

1982-01-01

Predicts that the growing market for automated circulation systems will expand even faster in the near future, given the availability of a wide variety of systems and computer types, which enables libraries of all sizes to obtain a system to fit their needs. Currently there are 301 systems installed. (RAA)

Energy budgets and a climate space diagram for the turtle, Chrysemys scripta

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

Foley, R. E.

1976-01-01

Heat energy budgets were computed and a steady state climate space was generated for a 1000 g red-eared turtle (Chrysemys scripta). Evaporative water loss (EWL) was measured from C. scripta at three wind speeds (10-400 cm sec/sup -1/) and at four air temperatures (5 to 35/sup 0/C) in a wind tunnel. EWL increased as air temperature and wind speed increased. Smaller turtles dehydrated at a faster rate than large turtles. Heat transfer by convection was measured from aluminum castings of C. scripta at three temperature differences between casting and air (..delta..T 15/sup 0/, 10/sup 0/ and 5/sup 0/C) for threemore » windspeeds (10 to 400 cm sec/sup -1/). Convective heat transfer coefficients increased as wind speed and ..delta..T increased. Wind speed has a large effect on the shape of the climate space. At high wind speeds, heat loss by evaporation and convection are greatly increased. In still air (10 cm sec/sup -1/), a turtle cannot remain exposed to full sunlight when air temperatures exceed 19/sup 0/C. When wind speed increases to 400 cm sec/sup -1/, the turtle can bask for long periods of time at temperatures as high as 32/sup 0/C. Basking patterns of C. scripta probably shift from a unimodal pattern in the spring to a bimodal pattern in summer and return to a unimodal pattern in fall. Terrestrial activity may be extensive in the spring and fall but is limited during the hot summer months to periods of rainfall. Nesting activities cannot occur around solar noon because increased metabolic heat loading and high solar radiation intensity could cause death.« less

Vacuum Processing Technique for Development of Primary Standard Blackbodies

PubMed Central

Navarro, M.; Bruce, S. S.; Johnson, B. Carol; Murthy, A. V.; Saunders, R. D.

1999-01-01

Blackbody sources with nearly unity emittance that are in equilibrium with a pure freezing metal such as gold, silver, or copper are used as primary standard sources in the International Temperature Scale of 1990 (ITS-90). Recently, a facility using radio-frequency induction heating for melting and filling the blackbody crucible with the freeze metal under vacuum conditions was developed at the National Institute of Standards and Technology (NIST). The blackbody development under a vacuum environment eliminated the possibility of contamination of the freeze metal during the process. The induction heating, compared to a resistively heated convection oven, provided faster heating of crucible and resulted in shorter turn-around time of about 7 h to manufacture a blackbody. This paper describes the new facility and its application to the development of fixed-point blackbodies.

Thickness and Fuel Preheating Effects on Material Flammability in Microgravity from the BASS Experiment

NASA Technical Reports Server (NTRS)

Ferkul, Paul V.; Olson, Sandra L.; Takahashi, Fumiaki; Endo, Makoto; Johnson, Michael C.; T'ien, James S.

2013-01-01

The Burning and Suppression of Solids (BASS) experiment was performed on the International Space Station. Microgravity combustion tests burning thin and thick flat samples, acrylic spheres, and candles were conducted. The samples were mounted inside a small wind tunnel which could impose air flow speeds up to 40 cms. The wind tunnel was installed in the Microgravity Science Glovebox which supplied power, imaging, and a level of containment. The effects of air flow speed, fuel thickness, fuel preheating, and nitrogen dilution on flame appearance, flame growth, and spread rates were determined in both the opposed and concurrent flow configuration. In some cases, a jet of nitrogen was introduced to attempt to extinguish the flame. Microgravity flames were found to be especially sensitive to air flow speed in the range 0 to 5 cms. The gas phase response is much faster compared to the solid and so as the flow speed is changed, the flame responds with almost no delay. At the lowest speeds examined (less than 1 cms) all the flames tended to become dim blue and very stable. However, heat loss at these very low convective rates is small so the flames can burn for a long time. At moderate flow speeds (between about 1 and 5 cms) the flame continually heats the solid fuel resulting in an increasing fuel temperature, higher rate of fuel vaporization, and a stronger, more luminous flame as time progresses. Only the smallest flames burning acrylic slabs appeared to be adversely influenced by solid conductive heat loss, but even these burned for over 5 minutes before self-extinguishing. This has implications for spacecraft fire safety since a tiny flame might be undetected for a long time. While the small flame is not particularly hazardous if it remains small, the danger is that it might flare up if the air convection is suddenly increased or if the flame spreads into another fuel source.

Thermoregulatory influence of a cooling vest on hyperthermic athletes.

PubMed

Lopez, Rebecca M; Cleary, Michelle A; Jones, Leon C; Zuri, Ron E

2008-01-01

Athletic trainers must have sound evidence for the best practices in treating and preventing heat-related emergencies and potentially catastrophic events. To examine the effectiveness of a superficial cooling vest on core body temperature (T(c)) and skin temperature (T(sk)) in hypohydrated hyperthermic male participants. A randomized control design with 2 experimental groups. Participants exercised by completing the heat-stress trial in a hot, humid environment (ambient temperature = 33.1 +/- 3.1 degrees C, relative humidity = 55.1 +/- 8.9%, wind speed = 2.1 +/- 1.1 km/hr) until a T(c) of 38.7 +/- 0.3 degrees C and a body mass loss of 3.27 +/- 0.1% were achieved. Ten healthy males (age = 25.6 +/- 1.6 years, mass = 80.3 +/- 13.7 kg). Recovery in a thermoneutral environment wearing a cooling vest or without wearing a cooling vest until T(c) returned to baseline. Rectal T(c), arm T(sk), time to return to baseline T(c), and cooling rate. During the heat-stress trial, T(c) significantly increased (3.6%) and, at 30 minutes of recovery, T(c) had decreased significantly (2.6%) for both groups. Although not significant, the time for return to baseline T(c) was 22.6% faster for the vest group (43.8 +/- 15.1 minutes) than for the no-vest group (56.6 +/- 18.0 minutes), and the cooling rate for the vest group (0.0298 +/- 0.0072 degrees C/min) was not significantly different from the cooling rate for the no-vest group (0.0280 +/- 0.0074 degrees C/min). The T(sk) during recovery was significantly higher (2.1%) in the vest group than in the no-vest group and was significantly lower (7.1%) at 30 minutes than at 0 minutes for both groups. We do not recommend using the cooling vest to rapidly reduce elevated T(c). Ice-water immersion should remain the standard of care for rapidly cooling severely hyperthermic individuals.

Physiologic and Perceptual Responses to Cold-Shower Cooling After Exercise-Induced Hyperthermia.

PubMed

Butts, Cory L; McDermott, Brendon P; Buening, Brian J; Bonacci, Jeffrey A; Ganio, Matthew S; Adams, J D; Tucker, Matthew A; Kavouras, Stavros A

2016-03-01

Exercise conducted in hot, humid environments increases the risk for exertional heat stroke (EHS). The current recommended treatment of EHS is cold-water immersion; however, limitations may require the use of alternative resources such as a cold shower (CS) or dousing with a hose to cool EHS patients. To investigate the cooling effectiveness of a CS after exercise-induced hyperthermia. Randomized, crossover controlled study. Environmental chamber (temperature = 33.4°C ± 2.1°C; relative humidity = 27.1% ± 1.4%). Seventeen participants (10 male, 7 female; height = 1.75 ± 0.07 m, body mass = 70.4 ± 8.7 kg, body surface area = 1.85 ± 0.13 m(2), age range = 19-35 years) volunteered. On 2 occasions, participants completed matched-intensity volitional exercise on an ergometer or treadmill to elevate rectal temperature to ≥39°C or until participant fatigue prevented continuation (reaching at least 38.5°C). They were then either treated with a CS (20.8°C ± 0.80°C) or seated in the chamber (control [CON] condition) for 15 minutes. Rectal temperature, calculated cooling rate, heart rate, and perceptual measures (thermal sensation and perceived muscle pain). The rectal temperature (P = .98), heart rate (P = .85), thermal sensation (P = .69), and muscle pain (P = .31) were not different during exercise for the CS and CON trials (P > .05). Overall, the cooling rate was faster during CS (0.07°C/min ± 0.03°C/min) than during CON (0.04°C/min ± 0.03°C/min; t16 = 2.77, P = .01). Heart-rate changes were greater during CS (45 ± 20 beats per minute) compared with CON (27 ± 10 beats per minute; t16 = 3.32, P = .004). Thermal sensation was reduced to a greater extent with CS than with CON (F3,45 = 41.12, P < .001). Although the CS facilitated cooling rates faster than no treatment, clinicians should continue to advocate for accepted cooling modalities and use CS only if no other validated means of cooling are available.

Simulation of reduction of iron-oxide-carbon composite pellets in a rotary hearth furnace

NASA Astrophysics Data System (ADS)

Halder, Sabuj

The primary motivation of this work is to evaluate a new alternative ironmaking process which involves the combination of a Rotary Hearth Furnace (RHF) with an iron bath smelter. This work is concerned primarily, with the productivity of the RHF. It is known that the reduction in the RHF is controlled by chemical kinetics of the carbon oxidation and wustite reduction reactions as well as by heat transfer to the pellet surface and within the pellet. It is heat transfer to the pellet which limits the number of layers of pellets in the pellet bed in the RHF and thus, the overall productivity. Different types of carbon like graphite, coal-char and wood charcoal were examined. Part of the research was to investigate the chemical kinetics by de-coupling it from the influence of heat and mass transfer. This was accomplished by carrying out reduction experiments using small iron-oxide-carbon powder composite mixtures. The reaction rate constants were determined by fitting the experimental mass loss with a mixed reaction model. This model accounts for the carbon oxidation by CO2 and wustite reduction by CO, which are the primary rate controlling surface-chemical reactions in the composite system. The reaction rate constants have been obtained using wustite-coal-char powder mixtures and wustite-wood-charcoal mixtures. The wustite for these mixtures was obtained from two iron-oxide sources: artificial porous analytical hematite (PAH) and hematite ore tailings. In the next phase of this study, larger scale experiments were conducted in a RHF simulator using spherical composite pellets. Measurement of the reaction rates was accomplished using off-gas analysis. Different combinations of raw materials for the pellets were investigated. These included artificial ferric oxide as well as naturally existing hematite and taconite ores. Graphite, coal-char and wood-charcoal were the reductants. Experiments were conducted using a single layer, a double layer and a triple layer of composite pellets to look into the different aspects associated with multi-layer reduction in the RHF. The reduced pellets were examined for morphology and phase distribution using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analysis. Efforts were made to interpret the differences in the observed rates from one kind of pellet to the other on the grounds of chemical kinetics of the carbon oxidation and wustite reduction reactions and the issues of external and internal heat transport to and within the pellets. It was concluded from the experiments that in the ore containing pellets, wood-charcoal appeared to be a faster reductant than coal-char. However, in the PAH containing pellets, the reverse was found to be true. This is because of the internal heat transport limitations imposed by two factors (a) lower thermal conductivity of wood-charcoal in comparison to coal-char and (b) swelling of the PAH-Wood-Charcoal pellets during the initial heat-up stage. For the same type of reductant, hematite containing pellets were observed to reduce faster than taconite containing pellets. This is in accordance with the higher reducibility of hematite because of development of internal porosity due to cracking and fissure formation during the Fe2O3 to Fe 3O4 transformation stage. This is however, absent during the reduction of taconite, which is primarily Fe3O4. The PAH-Wood-Charcoal pellets were found to undergo significant amounts of swelling under low temperature conditions. This behavior of the PAH-Wood-Charcoal pellets of a certain layer impeded the external heat transport to the lower layer and consequently, resulted in a relatively lower reduction rate for a multi-layer bed. The volume change phenomena associated with the reduction of composites were also studied. Volume changes influence the external heat transport, especially to the lower layers of a multi-layer bed. The volume change of the different kinds of composite pellets was studied as a function of reduction temperature and time. Empirical correlations were developed associating the volume shrinkage to the fractional mass loss of the pellets. The estimation of the change in the amount of external heat transport with varying pellet sizes for a particular layer of a multi-layer bed was obtained by conducting heat transport tests using inert low carbon steel spheres. The experimental temperature data for the spheres of different layers was interpreted using a simple mathematical model. It was found through this exercise, that if the spheres of the top layer of the bed shrink by 30%, the external heat transfer to the second layer increases by almost 6 times. This is because of the decrease in the shielded area of the second layer due to the decreasing size of the top layer spheres. If the average degree of reduction targeted in a RHF is reduced from 95% to about 70% by coupling the RHF with a bath smelter, the productivity of the RHF can be enhanced by 1.5 to 2 times. The use of a 2 or 3 layer bed was found to be far superior to that of a single layer for higher productivities under the current experimental conditions. Sometimes, a 2 layer bed is more advantageous than a 3 layer bed, as was found to be the case with hematite-wood-charcoal pellets. The choice of the optimal number of layers depends upon several factors like pellet size, kind of pellet and shrinking characteristics of the pellet.

Effect of ELMs on deuterium-loaded-tungsten plasma facing components

NASA Astrophysics Data System (ADS)

Umstadter, K. R.; Rudakov, D. L.; Wampler, W.; Watkins, J. G.; Wong, C. P. C.

2011-08-01

Prior heat pulse testing of plasma facing components (PFCs) has been completed in vacuum environments without the presence of background plasma. Edge localized modes (ELMs) will not be this kind of isolated event and one should know the effect of a plasma background during these transients. Heat-pulse experiments have been conducted in the PISCES-A device utilizing laser heating in a divertor-like plasma background. Initial results indicate that the erosion of PFCs is enhanced as compared to heat pulse or plasma only tests. To determine if the enhanced erosion effect is a phenomena only witnessed in the laboratory PISCES device, tungsten and graphite samples were exposed to plasmas in the lower divertor of the DIII-D tokamak using the Divertor Material Evaluation System (DiMES). Mass loss analysis indicates that materials that contain significant deuterium prior to experiencing a transient heating event will erode faster than those that have no or little retained deuterium.

Red palm oil production by microwave irradiation

NASA Astrophysics Data System (ADS)

Sarah, M.; Widyastuti, S.; Ningsih, D.

2018-02-01

Preliminary study of red palm oil (RPO) production from palm fruitlets by microwave irradiation carried out in domestic microwave oven equipped with thermocouple. The various mass of fruitlets (800, 900 and 1000 g) were heated for 10-18 minutes with 2 minutes interval and microwave power of 400, 560 and 800 Watt respectively. Heated fruitlets were pressed by hydraulic presser to obtain RPO. This study observed heating time parameter was more crucial to RPO quality rather than temperature. Prolonged heating degraded carotenoids in the fruitlets during heating process yielded less carotenoids content in the palm oil. The best time and microwave power combination to produce RPO in this study was 14 minutes and 800 Watt respectively which yielded 11.67% RPO with 1.27% FFA content and carotenoids concentration of 1219.37 ppm. Overall, RPO production by microwave irradiation proceeded faster as compared to conventional process.

Simultaneous measurement of bacterial flagellar rotation rate and swimming speed.

PubMed Central

Magariyama, Y; Sugiyama, S; Muramoto, K; Kawagishi, I; Imae, Y; Kudo, S

1995-01-01

Swimming speeds and flagellar rotation rates of individual free-swimming Vibrio alginolyticus cells were measured simultaneously by laser dark-field microscopy at 25, 30, and 35 degrees C. A roughly linear relation between swimming speed and flagellar rotation rate was observed. The ratio of swimming speed to flagellar rotation rate was 0.113 microns, which indicated that a cell progressed by 7% of pitch of flagellar helix during one flagellar rotation. At each temperature, however, swimming speed had a tendency to saturate at high flagellar rotation rate. That is, the cell with a faster-rotating flagellum did not always swim faster. To analyze the bacterial motion, we proposed a model in which the torque characteristics of the flagellar motor were considered. The model could be analytically solved, and it qualitatively explained the experimental results. The discrepancy between the experimental and the calculated ratios of swimming speed to flagellar rotation rate was about 20%. The apparent saturation in swimming speed was considered to be caused by shorter flagella that rotated faster but produced less propelling force. Images FIGURE 1 FIGURE 4 PMID:8580359

Eating on Demand

NASA Technical Reports Server (NTRS)

1998-01-01

Under subcontract to McDonnell-Douglas Corporation, Enersyst Development Center developed air impingement technology through oven designs for NASA's Space Station Freedom. Jets of hot air at the top and bottom of the oven are focused on the food, rather than heating the oven cavity as in a traditional thermal oven. By heating the food directly, foods cook faster and more consistently, retaining flavor and texture. Several companies have licensed this technology, including KRh Thermal Systems, which has introduced a line of Hot Choice vending machines. Enersyst has also licensed the first home application to Thermador.

A short response time atomic source for trapped ion experiments

NASA Astrophysics Data System (ADS)

Ballance, T. G.; Goodwin, J. F.; Nichol, B.; Stephenson, L. J.; Ballance, C. J.; Lucas, D. M.

2018-05-01

Ion traps are often loaded from atomic beams produced by resistively heated ovens. We demonstrate an atomic oven which has been designed for fast control of the atomic flux density and reproducible construction. We study the limiting time constants of the system and, in tests with 40Ca, show that we can reach the desired level of flux in 12 s, with no overshoot. Our results indicate that it may be possible to achieve an even faster response by applying an appropriate one-off heat treatment to the oven before it is used.

Pressure and temperature effects on degradation kinetics and storage stability of total anthocyanins in blueberry juice.

PubMed

Buckow, Roman; Kastell, Anja; Terefe, Netsanet Shiferaw; Versteeg, Cornelis

2010-09-22

The degradation kinetics of total anthocyanins in blueberry (Vaccinium myrtillus) juice were studied during thermal processing by treatment at selected temperatures (60-121 °C) and combined high pressure-temperature processing (100-700 MPa, 40-121 °C). Anthocyanin stability was also studied for several of these treatments during storage at 4, 25, and 40 °C. Both pressure and temperature increased d, the degradation rate of total anthocyanins in blueberry juice, meaning that at constant temperature, anthocyanins were more rapidly degraded with increasing pressure. For example, 32% degradation of anthocyanins was observed after 20 min heating at 100 °C and atmospheric pressure, whereas at 100 °C and 600 MPa, approximately 50% of total anthocyanins were lost. Degradation of anthocyanins was significantly accelerated with increasing storage temperatures. Combined pressure-temperature treatment of pasteurized juice led to a slightly faster degradation of total anthocyanins during storage compared to heat treatments at ambient pressure. Degradation of anthocyanins was best described by a 1.4th-order reaction at all conditions investigated. A mathematical model describing the degradation of blueberry anthocyanins in juice as a function of pressure, temperature, and treatment time is presented.

Clast Size, Void Space, and Degree of Contortion in Spatter Piles at Craters of the Moon, ID. Implications for Eruptions Conditions of Lunar Basalts.

NASA Astrophysics Data System (ADS)

Rader, E. L.; Heldmann, J. L.

2016-12-01

Spatter is an explosive volcanic product consisting of partially-molten clasts found predominantly in mafic eruptions. Classification of spatter deposits is currently based on qualitative visual identification, and its presence signifies little more than a near-vent environment. However, the variables that effect spatter morphology (density of clasts, aspect ratio of clasts, rind thickness, etc.) are related to heat transfer from the vent via convection and radiation to the atmosphere and conduction through the spatter pile. Subsequently, the heat flux is proportional to the volume and rate of eruption, as faster and more voluminous eruptions result in a higher degree of welding between clasts. With a quantitative classification scheme, spatter deposits may reveal important eruption conditions such as eruption duration, eruption vigor, and fountain height. These factors are particularly important for non-terrestrial volcanoes whose eruptions have never been observed and whose products will likely be sampled on too small of a scale for more detailed chemical and thermal analysis. This study describes physical aspects of multiple spatter deposits at Craters of the Moon National Monument in Idaho, and suggests different eruptions conditions will produce quantitatively unique spatter deposits.

Test Data Analysis of a Spray Bar Zero-Gravity Liquid Hydrogen Vent System for Upper Stages

NASA Technical Reports Server (NTRS)

Hedayat, A.; Bailey, J. W.; Hastings, L. J.; Flachbart, R. H.

2003-01-01

To support development of a zero-gravity pressure control capability for liquid hydrogen (LH2), a series of thermodynamic venting system (TVS) tests was conducted in 1996 and 1998 using the Marshall Space Flight Center (MSFC) multipurpose hydrogen test bed (MHTB). These tests were performed with ambient heat leaks =20 and 50 W for tank fill levels of 90%, 50%, and 25%. TVS performance testing revealed that the spray bar was highly effective in providing tank pressure control within a 7-kPa band (131-138 Wa), and complete destratification of the liquid and the ullage was achieved with all test conditions. Seven of the MHTB tests were correlated with the TVS performance analytical model. The tests were selected to encompass the range of tank fill levels, ambient heat leaks, operational modes, and ullage pressurants. The TVS model predicted ullage pressure and temperature and bulk liquid saturation pressure and temperature obtained from the TVS model were compared with the test data. During extended self-pressurization periods, following tank lockup, the model predicted faster pressure rise rates than were measured. However, once the system entered the cyclic mixing/venting operational mode, the modeled and measured data were quite similar.

Thermodynamic Limits of Body Dimension of Warm Blooded Animals

NASA Astrophysics Data System (ADS)

Ahlborn, Boye K.

2000-05-01

The metabolic rates Г o = aoM 0.73 [W], a 0 = 3.6, of animals of different body masses M [kg] determines their heat production Q' and their mechanical power output P. The metabolic heat production of small warm blooded animals living in a cold environment sets lower size limits for the body mass of birds and terrestrial mammals of Mt,b ≥ 0.01 kg and Maq ≥ 10 kg for fast aquatic mammals. Birds must travel at the speed υfl = 15M 1/6 [m/s] in order to stay aloft, but their muscles only generate the metabolic velocity υ Г ≤≈ 50M -0.25 [m/s]. These conditions yield an upper body size limit for flying birds: Mb ,max ≤ 15 kg. Walking speeds scale with body mass as υ walk ∝ M 1/6, while propagation speeds for endurance running are nearly independent of body mass. This makes walking faster than endurance running for animals with body masses M ≥ 600 kg.

Modeling thermal dynamics of active layer soils and near-surface permafrost using a fully coupled water and heat transport model

USGS Publications Warehouse

Jiang, Yueyang; Zhuang, Qianlai; O'Donnell, Jonathan A.

2012-01-01

Thawing and freezing processes are key components in permafrost dynamics, and these processes play an important role in regulating the hydrological and carbon cycles in the northern high latitudes. In the present study, we apply a well-developed soil thermal model that fully couples heat and water transport, to simulate the thawing and freezing processes at daily time steps across multiple sites that vary with vegetation cover, disturbance history, and climate. The model performance was evaluated by comparing modeled and measured soil temperatures at different depths. We use the model to explore the influence of climate, fire disturbance, and topography (north- and south-facing slopes) on soil thermal dynamics. Modeled soil temperatures agree well with measured values for both boreal forest and tundra ecosystems at the site level. Combustion of organic-soil horizons during wildfire alters the surface energy balance and increases the downward heat flux through the soil profile, resulting in the warming and thawing of near-surface permafrost. A projection of 21st century permafrost dynamics indicates that as the climate warms, active layer thickness will likely increase to more than 3 meters in the boreal forest site and deeper than one meter in the tundra site. Results from this coupled heat-water modeling approach represent faster thaw rates than previously simulated in other studies. We conclude that the discussed soil thermal model is able to well simulate the permafrost dynamics and could be used as a tool to analyze the influence of climate change and wildfire disturbance on permafrost thawing.

Theoretical analysis for condensation heat transfer of binary refrigerant mixtures with annular flow in horizontal mini-tubes

NASA Astrophysics Data System (ADS)

Zhang, Hui-Yong; Li, Jun-Ming; Sun, Ji-Liang; Wang, Bu-Xuan

2016-01-01

A theoretical model is developed for condensation heat transfer of binary refrigerant mixtures in mini-tubes with diameter about 1.0 mm. Condensation heat transfer of R410A and R32/R134a mixtures at different mass fluxes and saturated temperatures are analyzed, assuming that the phase flow pattern is annular flow. The results indicate that there exists a maximum interface temperature at the beginning of condensation process for azeotropic and zeotropic mixtures and the corresponding vapor quality to the maximum value increases with mass flux. The effects of mass flux, heat flux, surface tension and tube diameter are analyzed. As expected, the condensation heat transfer coefficients increase with mass flux and vapor quality, and increase faster in high vapor quality region. It is found that the effects of heat flux and surface tension are not so obvious as that of tube diameter. The characteristics of condensation heat transfer of zeotropic mixtures are consistent to those of azeotropic refrigerant mixtures. The condensation heat transfer coefficients increase with the concentration of the less volatile component in binary mixtures.

Men's Increase in College Enrollment Breaks Long-Term Trend--Rises Faster than Rate for Women. Fact Book Bulletin

ERIC Educational Resources Information Center

Southern Regional Education Board (SREB), 2012

2012-01-01

From 2005 to 2010, in an historic turnaround, the number of men enrolled in college increased faster than the number of women in the Southern Regional Education Board (SREB) region, the West and the Northeast. The Midwest was the only region where enrollment by women increased faster than for men over this period. In the SREB region, men's…

Association of female sex and heart rate with increased arterial stiffness in patients with type 2 diabetes mellitus

PubMed Central

Kang, Min-Kyung; Yu, Jae Myung; Chun, Kwang Jin; Choi, Jaehuk; Choi, Seonghoon; Lee, Namho; Cho, Jung Rae

2017-01-01

Objective: This study aimed to evaluate the factors associated with increased arterial stiffness (IAS) measured by pulse wave velocity (PWV) and its clinical implications in patients with type 2 diabetes mellitus (DM). Methods: This was an observational, cross-sectional study. The ankle–brachial PWV was used to measure arterial stiffness, and 310 patients (mean age, 49±9 years; 180 men) with type 2 DM were divided into two groups according to the results of PWV: Group 1 (IAS; n=214) and Group 2 (normal arterial stiffness; n=96). Results: Patients in Group 1 were predominantly females (48% vs. 28%, p=0.001) and showed higher blood pressure and faster heart rate (HR). The glomerular filtration rate was lower and the urine microalbumin level was higher in patients with IAS. In multiple regression analysis, female sex and faster HR were independently associated with IAS. In subgroup analysis among female patients, prior stroke was more common in patients with IAS, and faster HR and increased postprandial 2-h C-peptide level were independently associated with IAS. Conclusion: Female sex and faster HR were independently associated with IAS in patients with type 2 DM. In a subgroup analysis among female patients, prior stroke was more common in patients with IAS, and faster HR and elevated postprandial 2-h C-peptide level were found to be independently associated with IAS. PMID:29145217

Effect of Three Factors in Cheese Production (pH, Salt, and Heat) on Mycobacterium avium subsp. paratuberculosis Viability

PubMed Central

Sung, Nackmoon; Collins, Michael T.

2000-01-01

Low pH and salt are two factors contributing to the inactivation of bacterial pathogens during a 60-day curing period for cheese. The kinetics of inactivation for Mycobacterium avium subsp. paratuberculosis strains ATCC 19698 and Dominic were measured at 20°C under different pH and NaCl conditions commonly used in processing cheese. The corresponding D values (decimal reduction times; the time required to kill 1 log10 concentration of bacteria) were measured. Also measured were the D values for heat-treated and nonheated M. avium subsp. paratuberculosis in 50 mM acetate buffer (pH 5.0, 2% [wt/vol] NaCl) and a soft white Hispanic-style cheese (pH 6.0, 2% [wt/vol] NaCl). Samples were removed at various intervals until no viable cells were detected using the radiometric culture method (BACTEC) for enumeration of M. avium subsp. paratuberculosis. NaCl had little or no effect on the inactivation of M. avium subsp. paratuberculosis, and increasing NaCl concentrations were not associated with decreasing D values (faster killing) in the acetate buffer. Lower pHs, however, were significantly correlated with decreasing D values of M. avium subsp. paratuberculosis in the acetate buffer. The D values for heat-treated M. avium subsp. paratuberculosis ATCC 19698 in the cheese were higher than those predicted by studies done in acetate buffer. The heat-treated M. avium subsp. paratuberculosis strains had lower D values than the nonheated cells (faster killing) both in the acetate buffer (pH 5, 2% [wt/vol] NaCl) and in the soft white cheese. The D value for heat-treated M. avium subsp. paratuberculosis ATCC 19698 in the cheese (36.5 days) suggests that heat treatment of raw milk coupled with a 60-day curing period will inactivate about 103 cells of M. avium subsp. paratuberculosis per ml. PMID:10742208

Characteristics of hydrogen produced by partial oxidation and auto-thermal reforming in a small methanol reformer

NASA Astrophysics Data System (ADS)

Horng, Rong-Fang; Chou, Huann-Ming; Lee, Chiou-Hwang; Tsai, Hsien-Te

This paper investigates experimentally, the transient characteristics of a small methanol reformer using partial oxidation (POX) and auto-thermal reforming (ATR) for fuel cell applications. The parameters varied were heating temperature, methanol supply rate, steady mode shifting temperature, O 2/C (O 2/CH 3OH) and S/C (H 2O/CH 3OH) molar ratios with the main aim of promoting a rapid response and a high flow rate of hydrogen. The experiments showed that a high steady mode shifting temperature resulted in a faster temperature rise at the catalyst outlet and vice versa and that a low steady mode shifting temperature resulted in a lower final hydrogen concentration. However, when the mode shifting temperature was too high, the hydrogen production response was not necessarily improved. It was subsequently shown that the optimum steady mode shifting temperature for this experimental set-up was approximately 75 °C. Further, the hydrogen concentration produced by the auto-thermal process was as high as 49.12% and the volume flow rate up to 23.0 L min -1 compared to 40.0% and 20.5 L min -1 produced by partial oxidation.

Rate of loss of simazine, terbuthylazine, isoproturon, and methabenzthiazuron during soil solarization.

PubMed

Navarro, Simón; Bermejo, Salvador; Vela, Nuria; Hernández, Joaquín

2009-07-22

This paper reports the use of solar heating by polyethylene mulching for decontamination of a silty clay-loam soil polluted with herbicides. Soil solarization, a natural and hydrothermal method commonly used for disinfesting soils, was tested during the summer season on a Hipercalcic Calcisol located in Murcia (southeast Spain) for dissipation of s-triazine (simazine and terbuthylazine) and phenylurea (isoproturon and methabenzthiazuron) herbicides using low-density (LD) and high-density (HD) polyethylene (PE) film as a cover. A well-established influence of the film was observed on the dissipation of all herbicides from the soil, although the density (0.92-0.95 g/cm(3)) of the film used (LDPE and HDPE) was not significant in terms of the rate of loss. In all cases, a quick depletion during the first 2 weeks was observed, mainly for terbuthylazine. The first-order model satisfactorily explained the dissipation process, but the Hoerl and biexponential equations were more appropriate, mainly for simazine, isoproturon, and methabenzthiazuron. In all cases, herbicides disappeared at faster rates in solarized soils (DT(50) = 4-29 days) than in nonmulched soils (DT(50) = 11-35 days), especially for terbuthylazine and isoproturon.

Thermal comfort evaluation of three genetic lines of modern pigs using thermal images

USDA-ARS?s Scientific Manuscript database

Previous ARS research found that heat production of growing-finishing swine is 6 – 41% higher than documented in the ASABE and ASHRAE standards. The smallest changes were noted at the lightest weight pigs. This change is most likely due to larger, faster growing genotypes used in modern swine prod...

The variable polarity plasma arc welding process: Characteristics and performance

NASA Technical Reports Server (NTRS)

Hung, R. J.; Zhu, G. J.

1991-01-01

Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. The power distribution was analyzed for an argon plasma gas flow constituting the fluid in the VPPA Welding Process. The major heat loss at the torch nozzle is convective heat transfer; in the space between the outlet of the nozzle and the workpiece; radiative heat transfer; and in the keyhole in the workpiece, convective heat transfer. The power absorbed at the workpiece produces the molten puddle that solidifies into the weld bead. Crown and root widths, and crown and root heights of the weld bead are predicted. The basis is provided for an algorithm for automatic control of VPPA welding machine parameters to obtain desired weld bead dimensions.

Temperature profiles for laser-induced heating of nanocrystals embedded in glass matrices

NASA Astrophysics Data System (ADS)

Bhatnagar, Promod K.; Nagpal, Swati

2001-05-01

Quantum confined nanostructures are very important because of their application towards optoelectronic devices. Commercial colored glass filters, which have large semiconductor particles, are being used to manufacture nanocrystals by suitable heat treatments. The progress in this area has been hampered by high size dispersion of these dots in the glass matrix which leads to reduction in higher order susceptibility thereby reducing non-linearity. In the present paper attempt has been made to theoretically model the temperature profiles of a laser irradiated CdS doped Borosilicate sample. Laser being used has a beam diameter of 1.5 mm and energy for 10 nsec pulse is 10 mJ. Two different particle radii of 5 nm and 10 nm have been considered. It is found that larger particles reach higher temperatures for the same pulse characteristics. This is because smaller particles have larger surface to volume ratio and hence dissipates out heat faster to the surrounding. Hence bigger particles will reach dissolution temperature faster than smaller particle and particle beyond a certain size should dissolve in the glass matrix when a sample is heat treated by laser. This could lead to a reduction in size dispersion of the nanocrystals. Also photodarkening effect found in semiconductor doped glasses is a big handicap for practical application of these materials in fast optical switching and non-linear optical devices. Photodarkening effect has been established to be a photochemical effect and it is important to study the temperature profiles around a particle since it will effect the impurity migration.

Synthesis and characterization of pyrite (FeS{sub 2}) using microwave irradiation

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

Kim, Eun Jung, E-mail: ekim229@uwo.ca; Batchelor, Bill

2009-07-01

A procedure using microwave irradiation was studied to develop a fast and reliable method for synthesizing pyrite. Pyrite was successfully synthesized within a few minutes via reaction of ferric iron and hydrogen sulfide under the influence of irradiation by a conventional microwave oven. The SEM-EDX study revealed that the nucleation and growth of pyrite occurred on the surface of elemental sulfur, where polysulfides are available. Compared to conventional heating, using microwave energy results in rapid (<1 min) formation of smaller particulates of pyrite. Higher levels of microwave power can form pyrite even faster, but faster reaction can lead to themore » formation of pyrite with defects.« less

Multi-element microelectropolishing method

DOEpatents

Lee, Peter J.

1994-01-01

A method is provided for microelectropolishing a transmission electron microscopy nonhomogeneous multi-element compound foil. The foil is electrolyzed at different polishing rates for different elements by rapidly cycling between different current densities. During a first portion of each cycle at a first voltage a first element electrolyzes at a higher current density than a second element such that the material of the first element leaves the anode foil at a faster rate than the second element and creates a solid surface film, and such that the solid surface film is removed at a faster rate than the first element leaves the anode foil. During a second portion of each cycle at a second voltage the second element electrolyzes at a higher current density than the first element, and the material of the second element leaves the anode foil at a faster rate than the first element and creates a solid surface film, and the solid surface film is removed at a slower rate than the second element leaves the foil. The solid surface film is built up during the second portion of the cycle, and removed during the first portion of the cycle.

Warm Rain Processes Over the Tropical Oceans and Implications on Climate Change: Results from TRMM and GOES GCM

NASA Technical Reports Server (NTRS)

Lau, William K. M.; Wu, H. T.

2004-01-01

In this talk, we will first show results from TRMM data regarding the characteristics of warm rains over the tropical oceans, and the dependence of rate of warm rain production on sea surface temperature. Results lead to the hypothesis that warm rain production efficiency, i.e., autoconversion, may be increased in a warm climate. We use the GEOS-II GCM to test this hypothesis. Our modeling results show that in a climate with increased rate of autoconversion, the total rain amount is increased, with warm rain contributing to a larger portion of the increase. The abundant rainout of warm precipitation causes a reduction of low and middle cloud amount due to rainout, and reduced high clouds due to less water vapor available for ice-phase convection. However, clod radiation feedback caused by the increased rainfall efficiency, leads to differential vertical heating/cooling producing a more unstable atmosphere, allowing, more intense, but isolated penetrative convection, with contracted anvils to develop. Results also show that increased autoconversion reduces the convective adjustment time scale, resulting in faster recycling of atmospheric water. Most interestingly, the increased low level heating associated with warm rain leads to more energetic Madden and Julian oscillations in the tropics, with well-defined eastward propagation. While reducing the autoconversion leads to an abundant mix of westward and eastward tropical disturbances on daily to weekly time scales. The crucial link of precipitation microphysical processes to climate change including the effects of aerosols will be discussed.

Warm Rain Processes over the Tropical Oceans and Implications on Climate Change: Results from TRMM and GEOS GCM

NASA Technical Reports Server (NTRS)

Lau, William K. M.; Wu, H. T.

2004-01-01

In this talk, we will first show results from TRMM data regarding the characteristics of warm rains over the tropical oceans, and the dependence of rate of warm rain production on sea surface temperature. Results lead to the hypothesis that warm rain production efficiency, i.e., autoconversion, may be increased in a warm climate. We use the GEOS-II GCM to test this hypothesis. Our modeling results show that in a climate with increased rate of autoconversion, the total rain amount is increased, with warm rain contributing to larger portion of the increase. The abundant rainout of warm precipitation causes a reduction of low and middle cloud amount due to rainout, and reduced high clouds due to less water vapor available for ice-phase convection. However, clod radiation feedback caused by the increased rainfall efficiency, leads to differential vertical heating/cooling producing a more unstable atmosphere, allowing, more intense, but isolated penetrative convection, with contracted anvils to develop. Results also show that increased autoconversion reduces the convective adjustment time scale, resulting in faster recycling of atmospheric water. Most interestingly, the increased low level heating associated with warm rain leads to more energetic Madden and Julian oscillations in the tropics, with well-defined eastward propagation. While reducing the autoconversion leads to an abundant mix of westward and eastward tropical disturbances on daily to weekly time scales. The crucial link of precipitation microphysical processes to climate change including the effects of aerosols will be discussed.

Comparison of subsurface damages on mono-crystalline silicon between traditional nanoscale machining and laser-assisted nanoscale machining via molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Dai, Houfu; Li, Shaobo; Chen, Genyu

2018-01-01

Molecular dynamics is employed to compare nanoscale traditional machining (TM) with laser-assisted machining (LAM). LAM is that the workpiece is locally heated by an intense laser beam prior to material removal. We have a comprehensive comparison between LAM and TM in terms of atomic trajectories, phase transformation, radial distribution function, chips, temperature distribution, number of atoms in different temperature, grinding temperature, grinding force, friction coefficient and atomic potential energy. It can be found that there is a decrease of atoms with five and six nearest neighbors, and LAM generates more chips than that in the TM. It indicates that LAM reduces the subsurface damage of workpiece, gets a better-qualified ground surface and improves the material removal rate. Moreover, laser energy makes the materials fully softened before being removed, the number of atoms with temperature above 500 K is increased, and the average temperature of workpiece higher and faster to reach the equilibrium in LAM. It means that LAM has an absolute advantage in machining materials and greatly reduces the material resistance. Not only the tangential force (Fx) and the normal force (Fy) but also friction coefficients become smaller as laser heating reduces the strength and hardness of the material in LAM. These results show that LAM is a promising technique since it can get a better-qualified workpiece surface with larger material removal rates, less grinding force and lower friction coefficient.

Role of Hydrogen in High-Yield Growth of Boron Nitride Nanotubes at Atmospheric Pressure by Induction Thermal Plasma.

PubMed

Kim, Keun Su; Couillard, Martin; Shin, Homin; Plunkett, Mark; Ruth, Dean; Kingston, Christopher T; Simard, Benoit

2018-01-23

We recently demonstrated scalable manufacturing of boron nitride nanotubes (BNNTs) directly from hexagonal BN (hBN) powder by using induction thermal plasma, with a high-yield rate approaching 20 g/h. The main finding was that the presence of hydrogen is crucial for the high-yield growth of BNNTs. Here we investigate the detailed role of hydrogen by numerical modeling and in situ optical emission spectroscopy (OES) and reveal that both the thermofluidic fields and chemical pathways are significantly altered by hydrogen in favor of rapid growth of BNNTs. The numerical simulation indicated improved particle heating and quenching rates (∼10 5 K/s) due to the high thermal conductivity of hydrogen over the temperature range of 3500-4000 K. These are crucial for the complete vaporization of the hBN feedstock and rapid formation of nanosized B droplets for the subsequent BNNT growth. Hydrogen is also found to extend the active BNNT growth zone toward the reactor downstream, maintaining the gas temperature above the B solidification limit (∼2300 K) by releasing the recombination heat of H atoms, which starts at 3800 K. The OES study revealed that H radicals also stabilize B or N radicals from dissociation of the feedstock as BH and NH radicals while suppressing the formation of N 2 or N 2 + species. Our density functional theory calculations showed that such radicals can provide faster chemical pathways for the formation of BN compared with relatively inert N 2 .

Solid state characterization of E2101, a novel antispastic drug.

PubMed

Kushida, Ikuo; Ashizawa, Kazuhide

2002-10-01

E2101, a novel antispastic drug, was found to exist in at least two polymorphs that were confirmed by X-ray powder diffraction (XRD). These two species are designated forms I and II. The physicochemical and thermodynamic properties of these polymorphs were characterized by variable temperature XRD, thermal analysis, hygroscopicity measurements, and dissolution studies. The transition temperature was also estimated from the solubilities determined at various temperatures. The E2101 polymorphs were anhydrous and adsorbed little moisture under high humidity conditions. The melting onsets and heats of fusion for form I were 148.1 +/- 0.2 degrees C and 38.2 +/- 1.0 kJ/mol, respectively, and for form II were 139.8 +/- 0.4 degrees C and 35.2 +/- 0.5 kJ/mol, respectively. The intrinsic dissolution rate of form II in JP 2 medium was 1.5-fold faster than that of form I, corresponding to the rank order of the aqueous solubility and the enthalpy of fusion. Accordingly, form I was thought to be thermodynamically more stable than form II and thus suitable for further development. According to the thermal analysis and variable temperature XRD results, the recrystallization of form I occurred at approximately 145 degrees C after form II melted, however, no crystal transition behavior was observed below the lower melting point. The DSC thermograms at various heating rates and van't Hoff plots from the solubility studies indicated that the polymorphic pair would be monotropic. Copyright 2002 Wiley-Liss Inc. and the American Pharmaceutical Association

Movement amplitude and tempo change in piano performance

NASA Astrophysics Data System (ADS)

Palmer, Caroline

2004-05-01

Music performance places stringent temporal and cognitive demands on individuals that should yield large speed/accuracy tradeoffs. Skilled piano performance, however, shows consistently high accuracy across a wide variety of rates. Movement amplitude may affect the speed/accuracy tradeoff, so that high accuracy can be obtained even at very fast tempi. The contribution of movement amplitude changes in rate (tempo) is investigated with motion capture. Cameras recorded pianists with passive markers on hands and fingers, who performed on an electronic (MIDI) keyboard. Pianists performed short melodies at faster and faster tempi until they made errors (altering the speed/accuracy function). Variability of finger movements in the three motion planes indicated most change in the plane perpendicular to the keyboard across tempi. Surprisingly, peak amplitudes of motion before striking the keys increased as tempo increased. Increased movement amplitudes at faster rates may reduce or compensate for speed/accuracy tradeoffs. [Work supported by Canada Research Chairs program, HIMH R01 45764.

Growth rate effects on the formation of dislocation loops around deep helium bubbles in Tungsten

DOE PAGES

Sandoval, Luis; Perez, Danny; Uberuaga, Blas P.; ...

2016-11-15

Here, the growth process of spherical helium bubbles located 6 nm below a (100) surface is studied using molecular dynamics and parallel replica dynamics simulations, over growth rates from 10 6 to 10 12 helium atoms per second. Slower growth rates lead to a release of pressure and lower helium content as compared with fast growth cases. In addition, at slower growth rates, helium bubbles are not decorated by multiple dislocation loops, as these tend to merge or emit given sufficient time. At faster rates, dislocation loops nucleate faster than they can emit, leading to a more complicated dislocation structuremore » around the bubble.« less

Condensation Front Migration in a Protoplanetary Nebula

NASA Technical Reports Server (NTRS)

Davis, Sanford S.

2004-01-01

Condensation front dynamics are investigated in the mid-solar nebula region. A quasi-steady model of the evolving nebula is combined with equilibrium vapor pressure curves to determine evolutionary condensation fronts for selected species. These fronts are found to migrate inwards from the far-nebula to final positions during a period of 10(exp 7) years. The physical process governing this movement is a combination of local viscous heating and luminescent heating from the central star. Two luminescent heating models are used and their effects on the ultimate radial position of the condensation front are discussed. At first the fronts move much faster than the nebular accretion velocity, but after a time the accreting gas and dust overtakes the slowing condensation front.

Muscle fibre recruitment can respond to the mechanics of the muscle contraction.

PubMed

Wakeling, James M; Uehli, Katrin; Rozitis, Antra I

2006-08-22

This study investigates the motor unit recruitment patterns between and within muscles of the triceps surae during cycling on a stationary ergometer at a range of pedal speeds and resistances. Muscle activity was measured from the soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) using surface electromyography (EMG) and quantified using wavelet and principal component analysis. Muscle fascicle strain rates were quantified using ultrasonography, and the muscle-tendon unit lengths were calculated from the segmental kinematics. The EMG intensities showed that the body uses the SOL relatively more for the higher-force, lower-velocity contractions than the MG and LG. The EMG spectra showed a shift to higher frequencies at faster muscle fascicle strain rates for MG: these shifts were independent of the level of muscle activity, the locomotor load and the muscle fascicle strain. These results indicated that a selective recruitment of the faster motor units occurred within the MG muscle in response to the increasing muscle fascicle strain rates. This preferential recruitment of the faster fibres for the faster tasks indicates that in some circumstances motor unit recruitment during locomotion can match the contractile properties of the muscle fibres to the mechanical demands of the contraction.

Electron trapping data storage system and applications

NASA Technical Reports Server (NTRS)

Brower, Daniel; Earman, Allen; Chaffin, M. H.

1993-01-01

The advent of digital information storage and retrieval has led to explosive growth in data transmission techniques, data compression alternatives, and the need for high capacity random access data storage. Advances in data storage technologies are limiting the utilization of digitally based systems. New storage technologies will be required which can provide higher data capacities and faster transfer rates in a more compact format. Magnetic disk/tape and current optical data storage technologies do not provide these higher performance requirements for all digital data applications. A new technology developed at the Optex Corporation out-performs all other existing data storage technologies. The Electron Trapping Optical Memory (ETOM) media is capable of storing as much as 14 gigabytes of uncompressed data on a single, double-sided 54 inch disk with a data transfer rate of up to 12 megabits per second. The disk is removable, compact, lightweight, environmentally stable, and robust. Since the Write/Read/Erase (W/R/E) processes are carried out 100 percent photonically, no heating of the recording media is required. Therefore, the storage media suffers no deleterious effects from repeated Write/Read/Erase cycling.

Thermographic Inspections Save Skins and Prevent Blackouts

NASA Technical Reports Server (NTRS)

2003-01-01

Scanning thermography involves heating a component s surface and subsequently measuring the surface temperature, using an infrared camera to identify structural defects such as corrosion and disbonding. It is a completely noninvasive and noncontacting process. Scans can detect defects in conventional metals and plastics, as well as in bonded aluminum composites, plastic- and resinbased composites, and laminated structures. The apparatus used for scanning is highly portable and can cover the surface of a test material up to six times faster than conventional thermography. NASA scientists affirm that the technology is an invaluable asset to the airlines, detecting potential defects that can cause structural failure.In 1996, ThermTech Services, Inc., of Stuart, Florida, approached NASA in an effort to evaluate the technology for application in the power and process industries, where corrosion is of serious concern. ThermTech Services proceeded to develop the application for inspecting boiler waterwall tubing at fossil-fueled electric-generating stations. In 1999, ThermTech purchased the rights to NASA s patented technology and developed the specialized equipment required to apply the inspecting method to power plant components. The ThermTech robotic system using NASA technology has proved to be extremely successful and cost effective in performing detailed inspections of large structures such as boiler waterwalls and aboveground chemical storage tanks. It is capable of inspecting a waterwall, tank-wall, or other large surfaces at a rate of approximately 10 square feet per minute or faster.

Development of a driving method suitable for ultrahigh-speed shooting in a 2M-fps 300k-pixel single-chip color camera

NASA Astrophysics Data System (ADS)

Yonai, J.; Arai, T.; Hayashida, T.; Ohtake, H.; Namiki, J.; Yoshida, T.; Etoh, T. Goji

2012-03-01

We have developed an ultrahigh-speed CCD camera that can capture instantaneous phenomena not visible to the human eye and impossible to capture with a regular video camera. The ultrahigh-speed CCD was specially constructed so that the CCD memory between the photodiode and the vertical transfer path of each pixel can store 144 frames each. For every one-frame shot, the electric charges generated from the photodiodes are transferred in one step to the memory of all the parallel pixels, making ultrahigh-speed shooting possible. Earlier, we experimentally manufactured a 1M-fps ultrahigh-speed camera and tested it for broadcasting applications. Through those tests, we learned that there are cases that require shooting speeds (frame rate) of more than 1M fps; hence we aimed to develop a new ultrahigh-speed camera that will enable much faster shooting speeds than what is currently possible. Since shooting at speeds of more than 200,000 fps results in decreased image quality and abrupt heating of the image sensor and drive circuit board, faster speeds cannot be achieved merely by increasing the drive frequency. We therefore had to improve the image sensor wiring layout and the driving method to develop a new 2M-fps, 300k-pixel ultrahigh-speed single-chip color camera for broadcasting purposes.

High response speed microfluidic ice valves with enhanced thermal conductivity and a movable refrigeration source

PubMed Central

Si, Chaorun; Hu, Songtao; Cao, Xiaobao; Wu, Weichao

2017-01-01

Due to their ease of fabrication, facile use and low cost, ice valves have great potential for use in microfluidic platforms. For this to be possible, a rapid response speed is key and hence there is still much scope for improvement in current ice valve technology. Therefore, in this study, an ice valve with enhanced thermal conductivity and a movable refrigeration source has been developed. An embedded aluminium cylinder is used to dramatically enhance the heat conduction performance of the microfluidic platform and a movable thermoelectric unit eliminates the thermal inertia, resulting in a faster cooling process. The proposed ice valve achieves very short closing times (0.37 s at 10 μL/min) and also operates at high flow rates (1150 μL/min). Furthermore, the response time of the valve decreased by a factor of 8 when compared to current state of the art technology. PMID:28084447

A neural network controller for automated composite manufacturing

NASA Technical Reports Server (NTRS)

Lichtenwalner, Peter F.

1994-01-01

At McDonnell Douglas Aerospace (MDA), an artificial neural network based control system has been developed and implemented to control laser heating for the fiber placement composite manufacturing process. This neurocontroller learns an approximate inverse model of the process on-line to provide performance that improves with experience and exceeds that of conventional feedback control techniques. When untrained, the control system behaves as a proportional plus integral (PI) controller. However after learning from experience, the neural network feedforward control module provides control signals that greatly improve temperature tracking performance. Faster convergence to new temperature set points and reduced temperature deviation due to changing feed rate have been demonstrated on the machine. A Cerebellar Model Articulation Controller (CMAC) network is used for inverse modeling because of its rapid learning performance. This control system is implemented in an IBM compatible 386 PC with an A/D board interface to the machine.

Anomalous current diffusion and improved confinement in the HT-6M tohamak

NASA Astrophysics Data System (ADS)

Gao, X.; Li, J. G.; Wan, Y. X.; Huo, Y. P.; Guo, W. K.; Fan, S. P.; Yu, C. X.; Luo, J. R.; Yin, F. X.; Meng, Y. D.; Zheng, L.; Yin, F.; Lin, B. L.; Zhang, S. Y.; Wang, S. Y.; Lu, H. J.; Liu, S. X.; Tong, X. D.; Ding, L. C.; Wu, Z. Y.; Yin, X. J.; Guo, Q. L.; Gong, X. Z.; Wu, X. C.; Zhao, J. Y.; Xi, J. S.

1994-10-01

Current diffusion was studied during edge ohmic heating (EOH) experiments in the HT-6M tokamak. The EOH power system makes the plasma current linearly ramp up from an initial steady state ( Ip=55kA) to a second steady state ( Ip=60kA) at a fast ramp rate of 12 MA/s. A stable discharge of an improved confinement was observed experimentally in the HT-6M tokamak after the plasma current was ramped to rise rapidly to a second steady state. The plasma current is ramped up much faster than both the classical skin time and neoclassical skin time. Fast current ramp up increases the anomalous current diffusion. The measured values of {β P+l i}/{2} and the soft X-ray sawtooth inversion radius imply the anomalous current penetration. The mechanism of anomalous penetration and improved confinement is discussed.

Pyrolytic and Kinetic Characteristics of the Thermal Decomposition of Perilla frutescens Polysaccharide

PubMed Central

Zhou, Quancheng; Sheng, Guihua

2012-01-01

The thermal decomposition of Perilla frutescens polysaccharide was examined by thermogravimetry, differential thermogravimetry, and differential thermal analysis. The results showed that the mass loss of the substance proceeded in three steps. The first stage can be attributed to the expulsion of the water from ambient temperature to 182°C. The second stage corresponded to devolatilization from 182°C to 439°C. The residue slowly degraded in the third stage. The weight loss in air is faster than that in nitrogen, because the oxygen in air accelerated the pyrolytic reaction speed reaction. The heating rate significantly affected the pyrolysis of the sample. Similar activation energies of the degradation process (210–211 kJ mol−1) were obtained by the FWO, KAS, and Popescu techniques. According to Popescu mechanism functions, the possible kinetic model was estimated to be Avrami–Erofeev 20 g(α) = [−ln(1–α)]4. PMID:23300715

High response speed microfluidic ice valves with enhanced thermal conductivity and a movable refrigeration source

NASA Astrophysics Data System (ADS)

Si, Chaorun; Hu, Songtao; Cao, Xiaobao; Wu, Weichao

2017-01-01

Due to their ease of fabrication, facile use and low cost, ice valves have great potential for use in microfluidic platforms. For this to be possible, a rapid response speed is key and hence there is still much scope for improvement in current ice valve technology. Therefore, in this study, an ice valve with enhanced thermal conductivity and a movable refrigeration source has been developed. An embedded aluminium cylinder is used to dramatically enhance the heat conduction performance of the microfluidic platform and a movable thermoelectric unit eliminates the thermal inertia, resulting in a faster cooling process. The proposed ice valve achieves very short closing times (0.37 s at 10 μL/min) and also operates at high flow rates (1150 μL/min). Furthermore, the response time of the valve decreased by a factor of 8 when compared to current state of the art technology.

Phagocytic and chemiluminescent responses of mouse peritoneal macrophages to living and killed Salmonella typhimurium and other bacteria

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

Tomita, T.; Blumenstock, E.; Kanegasaki, S.

1981-06-01

In the presence of luminol, resident as well as thioglycolate-induced and immunized macrophages emitted chemiluminescence more efficiently when the cells were exposed to living Salmonella typhimurium than when they were exposed to the same bacterium killed by ultraviolet light or heat. This phenomenon was observed whether or not the bacterium was opsonized. The different response to living and killed bacteria was also found with Escherichia coli, Pseudomonas aeruginosa, Proteus morganii, and Enterobacter aerogenes, but not with Shigella sonnei, Klebsiella pneumoniae, and Propionibacterium acnes. The results suggest that macrophages respond better to living, motile bacteria than to nonmotile or killed bacteria.more » The experimental results obtained with motility mutants of S. typhimurium, E. coli, and P. aeruginosa confirm that macrophages exposed to the motile bacteria emit chemiluminescence more efficiently and ingest the motile bacteria at a much faster rate than the nonmotile bacteria.« less

A demonstration of glass bonding using patterned nanocomposite thermites deposited from fluid

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

Rodriguez, Juan Carlos

2015-01-01

Ceramics and other nonmetals are widely used in industrial and research applications. Although these materials provide many advantages, they often pose unique challenges during bonding. This work aims to expand on current processes, which have much narrower applications, to nd a more universal method for nonmetal bonding. We utilize inks comprised of aluminum-based nanoenergetics, (a heat source) and tin (a bonding agent). Requirements for successful bonding are explored and four key criteria are established. Through statistical simulation and thermochemical equilibrium calculations, we conclude that the presence of a diluent in large percentages negatively impacts reaction kinetics. Conversely, we show smallmore » percentages of added tin enhance gas generation and drive faster reaction rates. The bulk bonding material, thermite plus tin, forms a continuous structure during reaction, adhering well to the substrate surface. In some cases, these bonds failed above 1200 kPa.« less

Reordering transitions during annealing of block copolymer cylinder phases

DOE PAGES

Majewski, Pawel W.; Yager, Kevin G.

2015-10-06

While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. In this study, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene- block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the finalmore » horizontal state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.« less

Irreversible Local Markov Chains with Rapid Convergence towards Equilibrium.

PubMed

Kapfer, Sebastian C; Krauth, Werner

2017-12-15

We study the continuous one-dimensional hard-sphere model and present irreversible local Markov chains that mix on faster time scales than the reversible heat bath or Metropolis algorithms. The mixing time scales appear to fall into two distinct universality classes, both faster than for reversible local Markov chains. The event-chain algorithm, the infinitesimal limit of one of these Markov chains, belongs to the class presenting the fastest decay. For the lattice-gas limit of the hard-sphere model, reversible local Markov chains correspond to the symmetric simple exclusion process (SEP) with periodic boundary conditions. The two universality classes for irreversible Markov chains are realized by the totally asymmetric SEP (TASEP), and by a faster variant (lifted TASEP) that we propose here. We discuss how our irreversible hard-sphere Markov chains generalize to arbitrary repulsive pair interactions and carry over to higher dimensions through the concept of lifted Markov chains and the recently introduced factorized Metropolis acceptance rule.

Irreversible Local Markov Chains with Rapid Convergence towards Equilibrium

NASA Astrophysics Data System (ADS)

Kapfer, Sebastian C.; Krauth, Werner

2017-12-01

We study the continuous one-dimensional hard-sphere model and present irreversible local Markov chains that mix on faster time scales than the reversible heat bath or Metropolis algorithms. The mixing time scales appear to fall into two distinct universality classes, both faster than for reversible local Markov chains. The event-chain algorithm, the infinitesimal limit of one of these Markov chains, belongs to the class presenting the fastest decay. For the lattice-gas limit of the hard-sphere model, reversible local Markov chains correspond to the symmetric simple exclusion process (SEP) with periodic boundary conditions. The two universality classes for irreversible Markov chains are realized by the totally asymmetric SEP (TASEP), and by a faster variant (lifted TASEP) that we propose here. We discuss how our irreversible hard-sphere Markov chains generalize to arbitrary repulsive pair interactions and carry over to higher dimensions through the concept of lifted Markov chains and the recently introduced factorized Metropolis acceptance rule.

The Role of Ocean and Atmospheric Heat Transport in the Arctic Amplification

NASA Astrophysics Data System (ADS)

Vargas Martes, R. M.; Kwon, Y. O.; Furey, H. H.

2017-12-01

Observational data and climate model projections have suggested that the Arctic region is warming around twice faster than the rest of the globe, which has been referred as the Arctic Amplification (AA). While the local feedbacks, e.g. sea ice-albedo feedback, are often suggested as the primary driver of AA by previous studies, the role of meridional heat transport by ocean and atmosphere is less clear. This study uses the Community Earth System Model version 1 Large Ensemble simulation (CESM1-LE) to seek deeper understanding of the role meridional oceanic and atmospheric heat transports play in AA. The simulation consists of 40 ensemble members with the same physics and external forcing using a single fully coupled climate model. Each ensemble member spans two time periods; the historical period from 1920 to 2005 using the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical forcing and the future period from 2006 to 2100 using the CMIP5 Representative Concentration Pathways 8.5 (RCP8.5) scenario. Each of the ensemble members are initialized with slightly different air temperatures. As the CESM1-LE uses a single model unlike the CMIP5 multi-model ensemble, the internal variability and the externally forced components can be separated more clearly. The projections are calculated by comparing the period 2081-2100 relative to the time period 2001-2020. The CESM1-LE projects an AA of 2.5-2.8 times faster than the global average, which is within the range of those from the CMIP5 multi-model ensemble. However, the spread of AA from the CESM1-LE, which is attributed to the internal variability, is 2-3 times smaller than that of the CMIP5 ensemble, which may also include the inter-model differences. CESM1LE projects a decrease in the atmospheric heat transport into the Arctic and an increase in the oceanic heat transport. The atmospheric heat transport is further decomposed into moisture transport and dry static energy transport. Also, the oceanic heat transport is decomposed into the Pacific and Atlantic contributions.

Experimental Evidence for Fast Lithium Diffusion and Isotope Fractionation in Water-bearing Rhyolitic Melts at Magmatic Conditions

NASA Astrophysics Data System (ADS)

Cichy, S. B.; Till, C. B.; Roggensack, K.; Hervig, R. L.; Clarke, A. B.

2015-12-01

The aim of this work is to extend the existing database of experimentally-determined lithium diffusion coefficients to more natural cases of water-bearing melts at the pressure-temperature range of the upper crust. In particular, we are investigating Li intra-melt and melt-vapor diffusion and Li isotope fractionation, which have the potential to record short-lived magmatic processes (seconds to hours) in the shallow crust, especially during decompression-induced magma degassing. Hydrated intra-melt Li diffusion-couple experiments on Los Posos rhyolite glass [1] were performed in a piston cylinder at 300 MPa and 1050 °C. The polished interfaces between the diffusion couples were marked by addition of Pt powder for post-run detection. Secondary ion mass spectrometry analyses indicate that lithium diffuses extremely fast in the presence of water. Re-equilibration of a hydrated ~2.5 mm long diffusion-couple experiment was observed during the heating period from room temperature to the final temperature of 1050 °C at a rate of ~32 °C/min. Fractionation of ~40‰ δ7Li was also detected in this zero-time experiment. The 0.5h and 3h runs show progressively higher degrees of re-equilibration, while the isotope fractionation becomes imperceptible. Li contamination was observed in some experiments when flakes filed off Pt tubing were used to mark the diffusion couple boundary, while the use of high purity Pt powder produced better results and allowed easier detection of the diffusion-couple boundary. The preliminary lithium isotope fractionation results (δ7Li vs. distance) support findings from [2] that 6Li diffuses substantially faster than 7Li. Further experimental sets are in progress, including lower run temperatures (e.g. 900 °C), faster heating procedure (~100 °C/min), shorter run durations and the extension to mafic systems. [1] Stanton (1990) Ph.D. thesis, Arizona State Univ., [2] Richter et al. (2003) GCA 67, 3905-3923.

Lunar base heat pump

NASA Technical Reports Server (NTRS)

Goldman, Jeffrey H.; Tetreault, R.; Fischbach, D.; Walker, D.

1994-01-01

A heat pump is a device which elevates the temperature of a heat flow by a means of an energy input. By doing this, the heat pump can cause heat to transfer faster from a warm region to a cool region, or it can cause heat to flow from a cool region to a warmer region. The second case is the one which finds vast commercial applications such as air conditioning, heating, and refrigeration. Aerospace applications of heat pumps include both cases. The NASA Johnson Space Center is currently developing a Life Support Systems Integration Facility (LSSIF, previously SIRF) to provide system-level integration, operational test experience, and performance data that will enable NASA to develop flight-certified hardware for future planetary missions. A high lift heat pump is a significant part of the TCS hardware development associated with the LSSIF. The high lift heat pump program discussed here is being performed in three phases. In Phase 1, the objective is to develop heat pump concepts for a lunar base, a lunar lander, and for a ground development unit for the SIRF. In Phase 2, the design of the SIRF ground test unit is being performed, including identification and evaluation of safety and reliability issues. In Phase 3, the SIRF unit will be manufactured, tested, and delivered to the NASA Johnson Space Center.

Self-Propagating Frontal Polymerization in Water at Ambient Pressure

NASA Technical Reports Server (NTRS)

Olten, Nesrin; Kraigsley, Alison; Ronney, Paul D.

2003-01-01

Advances in polymer chemistry have led to the development of monomers and initiation agents that enable propagating free-radical polymerization fronts to exist. These fronts are driven by the exothermicity of the polymerization reaction and the transport of heat from the polymerized product to the reactant monomer/solvent/initiator solution. The thermal energy transported to the reactant solution causes the initiator to decompose, yielding free radicals, which start the free radical polymerization process as discussed in recent reviews. The use of polymerization processes based on propagating fronts has numerous applications. Perhaps the most important of these is that it enables rapid curing of polymers without external heating since the polymerization process itself provides the high temperatures necessary to initiate and sustain polymerization. This process also enables more uniform curing of arbitrarily thick samples since it does not rely on heat transfer from an external source, which will necessarily cause the temperature history of the sample to vary with distance from the surface according to a diffusion-like process. Frontal polymerization also enables filling and sealing of structures having cavities of arbitrary shape without having to externally heat the structure. Water at atmospheric pressure is most convenient solvent to employ and the most important for practical applications (because of the cost and environmental issues associated with DMSO and other solvents). Nevertheless, to our knowledge, steady, self-propagating polymerization fronts have not been reported in water at atmospheric pressure. Currently, polymerization fronts require a high boiling point solvent (either water at high pressures or an alternative solvent such as dimethyl sulfoxide (DMSO) (boiling point 189 C at atmospheric pressure.) Early work on frontal polymerization, employed pressures up to 5000 atm in order to avoid boiling of the monomer/solvent/initiator solution. High boiling point solutions are needed because in order to produce a propagating front, a high front temperature is needed to produce sufficiently rapid decomposition of the free radical initiator and subsequent free radical polymerization and heat release at a rate faster than heat losses remove thermal energy from the system. (While the conduction heat loss rate increases linearly with temperature, the free radical initiator decomposition is a high activation energy process whose rate increases much more rapidly than linearly with temperature, thus as the temperature decreases, the ratio of heat loss to heat generation increases, eventually leading to extinction of the front if the temperature is too low.) In order to obtain atmospheric pressure frontal polymerization in water, it is necessary to identify a monomer/initiator combination that is water soluble and will not extinguish even when the peak temperature (T*) is less than 100 C. In this work acrylic acid (AA) was chosen as the monomer because is it one of the most reactive monomers and can polymerize readily at low temperatures even without initiators. Ammonium persulfate (AP) was chosen as the initiator because it decomposes readily at low temperatures, produces relatively few bubbles and is commercially available. The propagation rates and extinction conditions of the fronts are studied for a range of AA and AP concentrations. Small amounts of fumed silica powder (Cab-o-sil, Cabot Corporation) were added to the solutions to inhibit buoyancy induced convection in the solutions; future studies will investigate the effects of buoyant convection within the solutions.

Melt-Infiltration Process For SiC Ceramics And Composites

NASA Technical Reports Server (NTRS)

Behrendt, Donald R.; Singh, Mrityunjay

1994-01-01

Reactive melt infiltration produces silicon carbide-based ceramics and composites faster and more economically than do such processes as chemical vapor infiltration (CVI), reaction sintering, pressureless sintering, hot pressing, and hot isostatic pressing. Process yields dense, strong materials at relatively low cost. Silicon carbide ceramics and composites made by reactive melt infiltration used in combustor liners of jet engines and in nose cones and leading edges of high-speed aircraft and returning spacecraft. In energy industry, materials used in radiant-heater tubes, heat exchangers, heat recuperators, and turbine parts. Materials also well suited to demands of advanced automobile engines.

Screening of liquids for thermocapillary bubble movement

NASA Technical Reports Server (NTRS)

Wilcox, W. R.; Subramanian, R. S.; Papazian, J. M.; Smith, H. D.; Mattox, D. M.

1979-01-01

Ground-based methods for pretesting qualitatively the thermocapillary movement of gas bubbles in a liquid to be used in space processing are discussed. Theoretical considerations are shown to require the use of a thin, enclosed, horizontal liquid film in order that the bubbles move faster than the bulk convection of the liquid, with insulating boundaries to prevent the onset of instabilities. Experimental realizations of horizontal cells in which to test the thermocapillary movement of bubbles in sheets of molten glass heated from below and organic melts in tubes heated from both ends are briefly described and the results of experiments are indicated.

Pain hypersensitivity in congenital blindness is associated with faster central processing of C-fibre input.

PubMed

Slimani, H; Plaghki, L; Ptito, M; Kupers, R

2016-10-01

We have recently shown that visual deprivation from birth exacerbates responses to painful thermal stimuli. However, the mechanisms underlying pain hypersensitivity in congenital blindness are unclear. To study the contribution of Aδ- and C-fibres in pain perception, we measured thresholds and response times to selective C- and Aδ-fibre activation in congenitally blind, late blind and normally sighted participants. Ultrafast constant-temperature heat pulses were delivered to the hand with a CO2 laser using an interleaved adaptive double staircase procedure. Participants were instructed to respond as quickly as possible when detecting a laser-induced sensation. We used a 650 ms cut-off criterion to distinguish fast Aδ- from slow C-fibre-mediated sensations. Congenitally blind participants showed significantly faster reaction times to C- but not to Aδ-fibre-mediated sensations. In contrast, thresholds for Aδ- and C-fibre stimulation did not differ between groups. Late blind individuals did not differ from sighted controls in any aspect. A follow-up experiment using only suprathreshold stimuli for Aδ- and C-fibre activation confirmed these findings and further showed that congenitally blind individuals detected significantly more C-fibre-mediated stimuli than sighted controls. A decomposition analysis of the reaction times indicated that the faster response times in the congenitally blind are due to more efficient central processing of C-fibre-mediated sensations. The increased sensitivity to painful thermal stimulation in congenital blindness may be due to more efficient central processing of C-fibre-mediated input, which may help to avoid impending dangerous encounters with stimuli that threaten the bodily integrity. WHAT DOES THIS STUDY ADD?: Hypersensitivity to heat pain in congenital blindness is associated with faster responses to C-fibre activation, likely caused by more efficient central processing of C-fibre-mediated input. © 2016 European Pain Federation - EFIC®

Temperature controlled CO(2) laser welding of soft tissues: urinary bladder welding in different animal models (rats, rabbits, and cats).

PubMed

Lobel, B; Eyal, O; Kariv, N; Katzir, A

2000-01-01

Laser welding of tissues is a method of closure of surgical incisions that, in principle, may have advantages over conventional closure methods. It is a noncontact technique that introduces no foreign body, the closure is continuous and watertight, and the procedure is faster and requires less skill to master. However, in practice, there have been difficulties in obtaining strong and reliable welding. We assumed that the quality of the weld depends on the ability to monitor and control the surface temperature of the welded zone during the procedure. Our objective was to develop a "smart" fiberoptic laser system for controlled temperature welding. We have developed a welding system based on a CO(2) laser and on infrared transmitting AgClBr fibers. This fiberoptic system plays a double role: transmitting laser power for tissue heating and noncontact (radiometric) temperature monitoring and control. The "true" temperature of the heated tissue was determined by using an improved calibration method. We carried out long-studies of CO(2) laser welding of urinary bladders in various animal models. Cystotomies were performed on the animals, and complete closure of the bladder was obtained with a surface temperature of 55 +/- 5 degrees C at the welding site. In early experiments on 31 rats, the success rate was 73%. In later experiments with 10 rabbits and 3 cats, there was an 80% and a 100% success rate, respectively. The success rate in these preliminary experiments and the quality of the weld, as determined histologically, demonstrate that temperature controlled CO(2) laser welding can produce effective welding of tissues. The fiberoptic system can be adapted for endoscopic laser welding. Copyright 2000 Wiley-Liss, Inc.

Non-Maxwellian electron energy probability functions in the plume of a SPT-100 Hall thruster

NASA Astrophysics Data System (ADS)

Giono, G.; Gudmundsson, J. T.; Ivchenko, N.; Mazouffre, S.; Dannenmayer, K.; Loubère, D.; Popelier, L.; Merino, M.; Olentšenko, G.

2018-01-01

We present measurements of the electron density, the effective electron temperature, the plasma potential, and the electron energy probability function (EEPF) in the plume of a 1.5 kW-class SPT-100 Hall thruster, derived from cylindrical Langmuir probe measurements. The measurements were taken on the plume axis at distances between 550 and 1550 mm from the thruster exit plane, and at different angles from the plume axis at 550 mm for three operating points of the thruster, characterized by different discharge voltages and mass flow rates. The bulk of the electron population can be approximated as a Maxwellian distribution, but the measured distributions were seen to decline faster at higher energy. The measured EEPFs were best modelled with a general EEPF with an exponent α between 1.2 and 1.5, and their axial and angular characteristics were studied for the different operating points of the thruster. As a result, the exponent α from the fitted distribution was seen to be almost constant as a function of the axial distance along the plume, as well as across the angles. However, the exponent α was seen to be affected by the mass flow rate, suggesting a possible relationship with the collision rate, especially close to the thruster exit. The ratio of the specific heats, the γ factor, between the measured plasma parameters was found to be lower than the adiabatic value of 5/3 for each of the thruster settings, indicating the existence of non-trivial kinetic heat fluxes in the near collisionless plume. These results are intended to be used as input and/or testing properties for plume expansion models in further work.

Effect of caffeine on cycling time-trial performance in the heat.

PubMed

Pitchford, Nathan W; Fell, James W; Leveritt, Michael D; Desbrow, Ben; Shing, Cecilia M

2014-07-01

The purpose of this investigation was to determine whether a moderate dose of caffeine would improve a laboratory simulated cycling time-trial in the heat. Nine well-trained male subjects (VO2max 64.4±6.8mLmin(-1)kg(-1), peak power output 378±40W) completed one familiarisation and two experimental laboratory simulated cycling time-trials in environmental conditions of 35°C and 25% RH 90min after consuming either caffeine (3mgkg(-1) BW) or placebo, in a double blind, cross-over study. Time-trial performance was faster in the caffeine trial compared with the placebo trial (mean±SD, 3806±359s versus 4079±333s, p=0.06, 90%CI 42-500s, 86% likelihood of benefit, d=-0.79). Caffeine ingestion was associated with small to moderate increases in average heart rate (p=0.178, d=0.39), VO2 (p=0.154, d=0.45), respiratory exchange ratio (p=0.292, d=0.35) and core temperature (p=0.616, d=0.22) when compared to placebo, however, these were not statistically significant. Average RPE during the caffeine supplemented time-trial was not significantly different from placebo (p=0.41, d=-0.13). Caffeine supplementation at 3mgkg(-1) BW resulted in a worthwhile improvement in cycling time-trial performance in the heat. Double-blind cross-over study. Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

(99)Tc(VII) Retardation, Reduction, and Redox Rate Scaling in Naturally Reduced Sediments.

PubMed

Liu, Yuanyuan; Liu, Chongxuan; Kukkadapu, Ravi K; McKinley, James P; Zachara, John; Plymale, Andrew E; Miller, Micah D; Varga, Tamas; Resch, Charles T

2015-11-17

An experimental and modeling study was conducted to investigate pertechnetate (Tc(VII)O4(-)) retardation, reduction, and rate scaling in three sediments from Ringold formation at U.S. Department of Energy's Hanford site, where (99)Tc is a major contaminant in groundwater. Tc(VII) was reduced in all the sediments in both batch reactors and diffusion columns, with a faster rate in a sediment containing a higher concentration of HCl-extractable Fe(II). Tc(VII) migration in the diffusion columns was reductively retarded with retardation degrees correlated with Tc(VII) reduction rates. The reduction rates were faster in the diffusion columns than those in the batch reactors, apparently influenced by the spatial distribution of redox-reactive minerals along transport paths that supplied Tc(VII). X-ray computed tomography and autoradiography were performed to identify the spatial locations of Tc(VII) reduction and transport paths in the sediments, and results generally confirmed the newly found behavior of reaction rate changes from batch to column. The results from this study implied that Tc(VII) migration can be reductively retarded at Hanford site with a retardation degree dependent on reactive Fe(II) content and its distribution in sediments. This study also demonstrated that an effective reaction rate may be faster in transport systems than that in well-mixed reactors.

A rate-based transcutaneous CO2 sensor for noninvasive respiration monitoring.

PubMed

Chatterjee, M; Ge, X; Kostov, Y; Luu, P; Tolosa, L; Woo, H; Viscardi, R; Falk, S; Potts, R; Rao, G

2015-05-01

The pain and risk of infection associated with invasive blood sampling for blood gas measurements necessitate the search for reliable noninvasive techniques. In this work we developed a novel rate-based noninvasive method for a safe and fast assessment of respiratory status. A small sampler was built to collect the gases diffusing out of the skin. It was connected to a CO2 sensor through gas-impermeable tubing. During a measurement, the CO2 initially present in the sampler was first removed by purging it with nitrogen. The gases in the system were then recirculated between the sampler and the CO2 sensor, and the CO2 diffusion rate into the sampler was measured. Because the measurement is based on the initial transcutaneous diffusion rate, reaching mass transfer equilibrium and heating the skin is no longer required, thus, making it much faster and safer than traditional method. A series of designed experiments were performed to analyze the effect of the measurement parameters such as sampler size, measurement location, subject positions, and movement. After the factor analysis tests, the prototype was sent to a level IV NICU for clinical trial. The results show that the measured initial rate of increase in CO2 partial pressure is linearly correlated with the corresponding arterial blood gas measurements. The new approach can be used as a trending tool, making frequent blood sampling unnecessary for respiratory status monitoring.

Experience gained in France on heat recovery from nuclear plants for agriculture and pisciculture

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

Balligand, P.; Le Gouellec, P.; Dumont, M.

1978-04-01

Since 1972, the Commissariat a l'Energie Atomique, Electricite de France, and the French Ministry of Agriculture have jointly examined the possibility of using thermal wastes from nuclear power plants for the benefit of agricultural production. A new process to heat greenhouses with water at 303 K using a double-wall plastic mulching laid directly on the soil has been successfully used for a few years on several hectares. When necessary, heat pumps are utilized. Very good results have been obtained for tomatoes, cucumbers, flowers, and strawberries, etc. Outdoor soil heating with buried pipes has been tested in Cadarache near an experimentalmore » pressurized water reactor for market garden crops and forestry. Gains in precocity and yield have been excellent, especially for asparagus, strawberries, and potatoes. Growing of eels has been four times faster in warm water over one year.« less

Physique traits of lightweight rowers and their relationship to competitive success

PubMed Central

Slater, G; Rice, A; Mujika, I; Hahn, A; Sharpe, K; Jenkins, D

2005-01-01

Objectives: Physique traits and their relationship to competitive success were assessed amongst lightweight rowers competing at the 2003 Australian Rowing Championships. Methods: Full anthropometric profiles were collected from 107 lightweight rowers (n = 65 males, n = 45 females) competing in the Under 23 and Open age categories. Performance assessments were obtained for 66 of these rowers based on results in the single sculls events. The relationship between physique traits and competitive success was then determined. Results: Lower body fat (heat time estimate –8.4 s kg–1, p<0.01), greater total body mass (heat time estimate –4.4 s kg–1, p = 0.03), and muscle mass (heat time estimate –10.2 s kg–1, p<0.01) were associated with faster 2000 m heat times. Conclusions: The more successful lightweight rowers were those who had lower body fat and greater total muscle mass. PMID:16183770

Kinetic modeling of Nernst effect in magnetized hohlraums.

PubMed

Joglekar, A S; Ridgers, C P; Kingham, R J; Thomas, A G R

2016-04-01

We present nanosecond time-scale Vlasov-Fokker-Planck-Maxwell modeling of magnetized plasma transport and dynamics in a hohlraum with an applied external magnetic field, under conditions similar to recent experiments. Self-consistent modeling of the kinetic electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's law, including Nernst advection of magnetic fields. In addition to showing the prevalence of nonlocal behavior, we demonstrate that effects such as anomalous heat flow are induced by inverse bremsstrahlung heating. We show magnetic field amplification up to a factor of 3 from Nernst compression into the hohlraum wall. The magnetic field is also expelled towards the hohlraum axis due to Nernst advection faster than frozen-in flux would suggest. Nonlocality contributes to the heat flow towards the hohlraum axis and results in an augmented Nernst advection mechanism that is included self-consistently through kinetic modeling.

Future heat waves due to climate change threaten the survival of Posidonia oceanica seedlings.

PubMed

Guerrero-Meseguer, Laura; Marín, Arnaldo; Sanz-Lázaro, Carlos

2017-11-01

Extreme weather events are major drivers of ecological change, and their occurrence is likely to increase due to climate change. The transient increases in atmospheric temperatures are leading to a greater occurrence of heat waves, extreme events that can produce a substantial warming of water, especially in enclosed basins such as the Mediterranean Sea. Here, we tested the effects of current and predicted heat waves on the early stages of development of the seagrass Posidonia oceanica. Temperatures above 27 °C limited the growth of the plant by inhibiting its photosynthetic system. It suffered a reduction in leaf growth and faster leaf senescence, and in some cases mortality. This study demonstrates that the greater frequency of heat waves, along with anticipated temperature rises in coming decades, are expected to negatively affect the germination of P. oceanica seedlings. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determining the Extent of Hydrothermal Interaction on the Southern Costa Rica Rift Ridge Flank During the Past 8 Ma from Joint Inversion of Geophysical Data

NASA Astrophysics Data System (ADS)

Wilson, D. J.; Moorkamp, M.; Hobbs, R. W.; Peirce, C.; Harris, R. N.; Morgan, J. V.

2017-12-01

Advective hydrothermal systems preferentially develop in zones of high porosity and permeability, driven by a local heat source. Associated chemical reactions lead to changes in the bulk physical properties, so variations in velocity and density, and the relationship connecting them, may provide a record of alteration by hydrothermal fluids. Oceanic crust accreted at intermediate rate ridges displays a range of characteristics between those typical for fast and slow spreading rates so changes in crustal porosity and permeability are sensitive to the interplay between tectonic stretching, magmatic supply and plate motions. Hence, changes in spreading style and sediment cover will influence the extent of the hydrothermal interaction that occurs and the mode of heat loss as evidenced by heat flow measurements. Using a variety of geophysical data we determine where hydrothermal circulation has been active in young oceanic crust that was accreted at an intermediate spreading rate. Results from traveltime tomography along a 300 km profile across the southern flank of the Costa Rica Rift reveal several variations in the P-wave velocity structure of the upper crust (layer 2). Following an initial increase in P-wave velocity near the ridge axis there is a section of the model 80 km in length that has lower P-wave velocity (up to 0.5 km s-1) compared to adjacent crust. This section has shallower bathymetry, by up to 500 m, than predicted by the subsidence curve and the top basement surface is rougher with a greater amount of faulting and larger throws. This zone is preceded by crust with significantly faster P-wave velocities (up to 1.0 km s-1) that was sampled by DSDP/ODP 504B. We characterise these changes in the shallow crustal structure by jointly inverting travel-time data and gravity data with deeper control from coincident magnetotelluric data. Using a cross-gradient approach allows us to search for models with a structural match, thus determining the relationship between P-wave velocity and density models from which we infer the likely hydrothermal regimes at the time of formation at the spreading ridge. This research is part of a major, interdisciplinary NERC-funded collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Microwave ablation at 10.0 GHz achieves comparable ablation zones to 1.9 GHz in ex vivo bovine liver.

PubMed

Luyen, Hung; Gao, Fuqiang; Hagness, Susan C; Behdad, Nader

2014-06-01

We demonstrate the feasibility of using high-frequency microwaves for tissue ablation by comparing the performance of a 10 GHz microwave ablation system with that of a 1.9 GHz system. Two sets of floating sleeve dipole antennas operating at these frequencies were designed and fabricated for use in ex vivo experiments with bovine livers. Combined electromagnetic and transient thermal simulations were conducted to analyze the performance of these antennas. Subsequently, a total of 16 ablation experiments (eight at 1.9 GHz and eight at 10.0 GHz) were conducted at a power level of 42 W for either 5 or 10 min. In all cases, the 1.9 and 10 GHz experiments resulted in comparable ablation zone dimensions. Temperature monitoring probes revealed faster heating rates in the immediate vicinity of the 10.0 GHz antenna compared to the 1.9 GHz antenna, along with a slightly delayed onset of heating farther from the 10 GHz antenna, suggesting that heat conduction plays a greater role at higher microwave frequencies in achieving a comparably sized ablation zone. The results obtained from these experiments agree very well with the combined electromagnetic/thermal simulation results. These simulations and experiments show that using lower frequency microwaves does not offer any significant advantages, in terms of the achievable ablation zones, over using higher frequency microwaves. Indeed, it is demonstrated that high-frequency microwave antennas may be used to create reasonably large ablation zones. Higher frequencies offer the advantage of smaller antenna size, which is expected to lead to less invasive interstitial devices and may possibly lead to the development of more compact multielement arrays with heating properties not available from single-element antennas.

Shock initiated thermal and chemical responses of HMX crystal from ReaxFF molecular dynamics simulation.

PubMed

Zhou, Tingting; Song, Huajie; Liu, Yi; Huang, Fenglei

2014-07-21

To gain an atomistic-level understanding of the thermal and chemical responses of condensed energetic materials under thermal shock, we developed a thermal shock reactive dynamics (TS-RD) computational protocol using molecular dynamics simulation coupled with ReaxFF force field. β-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) was selected as a a target explosive due to its wide usage in the military and industry. The results show that a thermal shock initiated by a large temperature gradient between the "hot" region and the "cold" region results in thermal expansion of the particles and induces a thermal-mechanical wave propagating back and forth in the system with an averaged velocity of 3.32 km s(-1). Heat propagating along the direction of thermal shock leads to a temperature increment of the system and thus chemical reaction initiation. Applying a continuum reactive heat conduction model combined with the temperature distribution obtained from the RD simulation, a heat conduction coefficient is derived as 0.80 W m(-1) K(-1). The chemical reaction mechanisms during thermal shock were analyzed, showing that the reaction is triggered by N-NO2 bond breaking followed by HONO elimination and ring fission. The propagation rates of the reaction front and reaction center are obtained to be 0.069 and 0.038 km s(-1), based on the time and spatial distribution of NO2. The pressure effect on the thermal shock was also investigated by employing uniaxial compression before the thermal shock. We find that compression significantly accelerates thermal-mechanical wave propagation and heat conduction, resulting in higher temperature and more excited molecules and thus earlier initiation and faster propagation of chemical reactions.

Fiber Laser Weldability of Austenitic Nickel Alloys

NASA Astrophysics Data System (ADS)

Watson, Jonathan

Recent developments of fiber lasers allow for easier beam delivery facilitating greater applications for laser welding in industry. Welding with high energy density heat sources allows for faster travel speeds, faster cooling rates, and smaller heat affected zones. However, there is a still a lack of knowledge base on how laser welding process parameters affect the weldability of austenitic nickel alloys. In this work, laser welds were made on several austenitic nickel alloys from different alloy families: HAYNESRTM 214RTM alloy, HAYNESRTM 282RTM alloy, HAYNESRTM 230RTM alloy, HAYNESRTM HR-120RTM alloy, HAYNESRTM HR-160 RTM alloy, HAYNESRTM 188 alloy, HAYNESRTM 718 alloy. Welds were made at 25 mm/s at laser powers ranging from 400 to 600 Watts. Solidification cracking was observed in cross-sections of the fusion zone of HR-160RTM alloy and HR-120RTM alloy. Dendritic solidification was found in all alloys, and partitioning within the dendritic structure compared well with Scheil calculations performed using ThermoCalc software. A eutectic liquid rich in carbide forming elements was found at the interdendritic regions in 188, 230RTM, 282 RTM, and 718 alloys and was quantified by processing backscatter electron images of the fusion zone. This interdendritic liquid was found to back fill solidification cracks that formed in the fusion zone during weldability testing. Transverse Varestraint and Sigma-Jig testing were performed to rank the weldability of alloys. During Transvarestraint testing, the ram drop timing was recorded in relation to the laser output, and a type R thermocouple was also placed in the laser path, and the approximate cooling rate of the fusion zone was recorded and used to calculate the solidification cracking temperature range. Rankings of the weldability compared well between Sigma-Jig and Transvarestraint testing, with the exception of 214 alloy and HR-120 alloy, which ranked much better and worse, respectively in Sigma-Jig tests. A possible explanation for this difference is the higher thermal conductivity and lower yields strength of 214 alloy and high temperatures, allowing it to accommodate more stress in the Sigma-Jig test. The final ranking of alloys from more weldable to less weldable by Sigma-Jig testing is 188, 214, 282, 718, 230, HR-120, and HR-160. The final ranking by maximum crack length in Transvarestraint specimens listed from more weldable to less weldable is: 188, 282, HR-120, 718, 230, 214, and HR-160.

The Pace of Cultural Evolution

PubMed Central

Perreault, Charles

2012-01-01

Today, humans inhabit most of the world’s terrestrial habitats. This observation has been explained by the fact that we possess a secondary inheritance mechanism, culture, in addition to a genetic system. Because it is assumed that cultural evolution occurs faster than biological evolution, humans can adapt to new ecosystems more rapidly than other animals. This assumption, however, has never been tested empirically. Here, I compare rates of change in human technologies to rates of change in animal morphologies. I find that rates of cultural evolution are inversely correlated with the time interval over which they are measured, which is similar to what is known for biological rates. This correlation explains why the pace of cultural evolution appears faster when measured over recent time periods, where time intervals are often shorter. Controlling for the correlation between rates and time intervals, I show that (1) cultural evolution is faster than biological evolution; (2) this effect holds true even when the generation time of species is controlled for; and (3) culture allows us to evolve over short time scales, which are normally accessible only to short-lived species, while at the same time allowing for us to enjoy the benefits of having a long life history. PMID:23024804

Multi-element microelectropolishing method

DOEpatents

Lee, P.J.

1994-10-11

A method is provided for microelectropolishing a transmission electron microscopy nonhomogeneous multi-element compound foil. The foil is electrolyzed at different polishing rates for different elements by rapidly cycling between different current densities. During a first portion of each cycle at a first voltage a first element electrolyzes at a higher current density than a second element such that the material of the first element leaves the anode foil at a faster rate than the second element and creates a solid surface film, and such that the solid surface film is removed at a faster rate than the first element leaves the anode foil. During a second portion of each cycle at a second voltage the second element electrolyzes at a higher current density than the first element, and the material of the second element leaves the anode foil at a faster rate than the first element and creates a solid surface film, and the solid surface film is removed at a slower rate than the second element leaves the foil. The solid surface film is built up during the second portion of the cycle, and removed during the first portion of the cycle. 10 figs.

Characteristics of Hydrothermal Mineralization in Ultraslow Spreading Ridges

NASA Astrophysics Data System (ADS)

Zhou, H.; Yang, Q.; Ji, F.; Dick, H. J.

2014-12-01

Hydrothermal activity is a major component of the processes that shape the composition and structure of the ocean crust, providing a major pathway for the exchange of heat and elements between the Earth's crust and oceans, and a locus for intense biological activity on the seafloor and underlying crust. In other hand, the structure and composition of hydrothermal systems are the result of complex interactions between heat sources, fluids, wall rocks, tectonic controls and even biological processes. Ultraslow spreading ridges, including the Southwest Indian Ridge, the Gakkel Ridge, are most remarkable end member in plate-boundary structures (Dick et al., 2003), featured with extensive tectonic amagmatic spreading and frequent exposure of peridotite and gabbro. With intensive surveys in last decades, it is suggested that ultraslow ridges are several times more effective than faster-spreading ridges in sustaining hydrothermal activities. This increased efficiency could attributed to deep mining of heat and even exothermic serpentinisation (Baker et al., 2004). Distinct from in faster spreading ridges, one characteristics of hydrothermal mineralization on seafloor in ultraslow spreading ridges, including the active Dragon Flag hydrothermal field at 49.6 degree of the Southwest Indian Ridge, is abundant and pervasive distribution of lower temperature precipitated minerals ( such as Fe-silica or silica, Mn (Fe) oxides, sepiolite, pyrite, marcasite etc. ) in hydrothermal fields. Structures formed by lower temperature activities in active and dead hydrothermal fields are also obviously. High temperature precipitated minerals such as chalcopyrite etc. are rare or very limited in hydrothermal chimneys. Distribution of diverse low temperature hydrothermal activities is consistence with the deep heating mechanisms and hydrothermal circulations in the complex background of ultraslow spreading tectonics. Meanwhile, deeper and larger mineralization at certain locations along the ultraslow spreading ridges is also presumable.

Proof of concept of the CaO/Ca(OH)2 reaction in a continuous heat-exchanger BFB reactor for thermochemical heat storage in CSP plants

NASA Astrophysics Data System (ADS)

Rougé, Sylvie; Criado, Yolanda A.; Huille, Arthur; Abanades, J. Carlos

2017-06-01

The CaO/Ca(OH)2 hydration/dehydration reaction has long been identified as a attractive method for storing CSP heat. However, the technology applications are still at laboratory scale (TG or small fixed beds). The objective of this work is to investigate the hydration and dehydration reactions performance in a bubbling fluidized bed (BFB) which offers a good potential with regards to heat and mass transfers and upscaling at industrial level. The reactions are first investigated in a 5.5 kW batch BFB, the main conditions are the bed temperature (400-500°C), the molar fraction of steam in the fluidizing gas (0-0.8), the fluidizing gas velocity (0.2-0.7 m/s) and the mass of lime in the batch (1.5-3.5 kg). To assist in the interpretation of the experimental results, a standard 1D bubbling reactor model is formulated and fitted to the experimental results. The results indicate that the hydration reaction is mainly controlled by the slow kinetics of the CaO material tested while significant emulsion-bubble mass-transfer resistances are identified during dehydration due to the much faster dehydration kinetics. In the continuity of these preliminary investigations, a continuous 15.5 kW BFB set-up has been designed, manufactured and started with the objective to operate the hydration and dehydration reactions in steady state during a few hours, and to investigate conditions of faster reactivity such as higher steam molar fractions (up to 1), temperatures (up to 600°C) and velocities (up to 1.5 m/s).

Temperature analysis during bonding of brackets using LED or halogen light base units.

PubMed

Silva, Paulo César Gomes; De Fátima Zanirato Lizarelli, Rosane; Moriyama, Lílian Tan; De Toledo Porto Neto, Sizenando; Bagnato, Vanderlei Salvador

2005-02-01

The purpose of our investigation is to compare the intrapulpal temperature changes following blue LED system and halogen lamp irradiation at the enamel surface of permanent teeth. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Several light sources can be used: halogens, arc plasma, lasers, and recently blue LED systems. An important aspect to be observed during such a procedures is the temperature change. In this study, we have used nine human extracted permanent teeth: three central incisors, three lateral incisors, and three canines. Teeth were exposed to two light sources: blue LED system (preliminary commercial model LEC 470-II) and halogen lamp (conventional photo-cure equipment). The surface of teeth was exposed for 20, 40, and 60 sec at the buccal and lingual enamel surface with an angle of 45 degrees. Temperature values measured by a thermistor placed at pulpar chamber were read in time intervals of 1 sec. We obtained plots showing the temperature evolution as a function of time for each experiment. There is a correlation between heating quantity and exposition time of light source: with increasing exposition time, heating increases into the pulpal chamber. The halogen lamp showed higher heating than the LED system, which showed a shorter time of cooling than halogen lamp. The blue LED system seems like the indicated light source for photo-cure of composite resin during the bonding of brackets. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Blue LED equipment did not heat during its use. This could permit a shorter clinical time of operation and better performance.

Heat flux instrumentation for Hyflite thermal protection system

NASA Technical Reports Server (NTRS)

Diller, T. E.

1994-01-01

Using Thermal Protection Tile core samples supplied by NASA, the surface characteristics of the FRCI, TUFI, and RCG coatings were evaluated. Based on these results, appropriate methods of surface preparation were determined and tested for the required sputtering processes. Sample sensors were fabricated on the RCG coating and adhesion was acceptable. Based on these encouraging results, complete Heat Flux Microsensors were fabricated on the RCG coating. The issue of lead attachment was addressed with the annnealing and welding methods developed at NASA Lewis. Parallel gap welding appears to be the best method of lead attachment with prior heat treatment of the sputtered pads. Sample Heat Flux Microsensors were submitted for testing in the NASA Ames arc jet facility. Details of the project are contained in two attached reports. One additional item of interest is contained in the attached AIAA paper, which gives details of the transient response of a Heat Flux Microsensors in a shock tube facility at Virginia Tech. The response of the heat flux sensor was measured to be faster than 10 micro-s.

Water and heat transport in boreal soils: Implications for soil response to climate change

USGS Publications Warehouse

Fan, Z.; Neff, J.C.; Harden, J.W.; Zhang, T.; Veldhuis, H.; Czimczik, C.I.; Winston, G.C.; O'Donnell, J. A.

2011-01-01

Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4??C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30. years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate. ?? 2011 Elsevier B.V.

Water and heat transport in boreal soils: Implications for soil response to climate change

USGS Publications Warehouse

Fan, Zhaosheng; Harden, Jennifer W.; Winston, G.C.; O'Donnell, Jonathan A.; Neff, Jason C.; Zhang, Tingjun; Veldhuis, Hugo; Czimczik, C.I.

2011-01-01

Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2–4 °C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30 years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate.

Higher rate alternative non-drug reinforcement produces faster suppression of cocaine seeking but more resurgence when removed.

PubMed

Craig, Andrew R; Nall, Rusty W; Madden, Gregory J; Shahan, Timothy A

2016-06-01

Relapse following removal of an alternative source of reinforcement introduced during extinction of a target behavior is called resurgence. This form of relapse may be related to relapse of drug taking following loss of alternative non-drug reinforcement in human populations. Laboratory investigations of factors mediating resurgence with food-maintained behavior suggest higher rates of alternative reinforcement produce faster suppression of target behavior but paradoxically generate more relapse when alternative reinforcement is discontinued. At present, it is unknown if a similar effect occurs when target behavior is maintained by drug reinforcement and the alternative is a non-drug reinforcer. In the present experiment three groups of rats were trained to lever press for infusions of cocaine during baseline. Next, during treatment, cocaine reinforcement was suspended and an alternative response was reinforced with either high-rate, low-rate, or no alternative food reinforcement. Finally, all reinforcement was suspended to test for relapse of cocaine seeking. Higher rate alternative reinforcement produced faster elimination of cocaine seeking than lower rates or extinction alone, but when treatment was suspended resurgence of cocaine seeking occurred following only high-rate alternative reinforcement. Thus, although higher rate alternative reinforcement appears to more effectively suppress drug seeking, should it become unavailable, it can have the unfortunate effect of increasing relapse. Copyright © 2016 Elsevier B.V. All rights reserved.

Shanghai: a study on the spatial growth of population and economy in a Chinese metropolitan area.

PubMed

Zhu, J

1995-01-01

In this study of the growth in population and industry in Shanghai, China, between the 1982 and 1990 censuses, data on administrative divisions was normalized through digitization and spatial analysis. Analysis focused on spatial units, intensity of growth, time period, distance, rate of growth, and direction of spatial growth. The trisection method divided the city into city proper, outskirts, and suburbs. The distance function method considered the distance from center city as a function: exponential, power, trigonometric, logarithmic, and polynomial. Population growth and employment in all sectors increased in the outskirts and suburbs and decreased in the city proper except tertiary sectors. Primary sector employment decreased in all three sections. Employment in the secondary increased faster in the outskirts and suburbs than the total rate of growth of population and employment. In the city secondary sector employment rates decreased faster than total population and employment rates. The tertiary sector had the highest rate of growth in all sections, and employment grew faster than secondary sector rates. Tertiary growth was highest in real estate, finance, and insurance. Industrial growth in the secondary sector was 160.2% in the suburbs, 156.6% in the outskirts, and 80.9% in the city. In the distance function analysis, industry expanded further out than the entire secondary sector. Commerce grew the fastest in areas 15.4 km from center city. Economic growth was faster after economic reforms in 1978. Growth was led by industry and followed by the secondary sector, the tertiary sector, and population. Industrial expansion resulted from inner pressure, political factors controlling size, the social and economic system, and the housing construction and distribution system. Initially sociopsychological factors affected urban concentration.

The heat rate index indicator

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

Lasasso, M.; Runyan, B.; Napoli, J.

1995-06-01

This paper describes a method of tracking unit performance through the use of a reference number called the Heat Rate Index Indicator. The ABB Power Plant Controls OTIS performance monitor is used to determine when steady load conditions exist and then to collect controllable and equipment loss data which significantly impact thermal efficiency. By comparing these loss parameters to those found during the previous heat balance, it is possible to develop a new adjusted heat rate curve. These impacts on heat rate are used to changes the shape of the tested heat rate curve by the appropriate percentages over amore » specified load range. Mathcad is used to determine the Heat Rate Index by integrating for the areas beneath the adjusted heat rate curve and a heat rate curve that represents the unit`s ideal heat rate curve is the Heat Rate Index. An index of 1.0 indicates that the unit is operating at an ideal efficiency, while an index of less than 1.0 indicates that the unit is operating at less than ideal conditions. A one per cent change in the Heat Rate Index is equivalent to a one percent change in heat rate. The new shape of the adjusted heat rate curve and the individual curves generated from the controllable and equipment loss parameters are useful for determining performance problems in specific load ranges.« less

Program documentation: Surface heating rate of thin skin models (THNSKN)

NASA Technical Reports Server (NTRS)

Mcbryde, J. D.

1975-01-01

Program THNSKN computes the mean heating rate at a maximum of 100 locations on the surface of thin skin transient heating rate models. Output is printed in tabular form and consists of time history tabulation of temperatures, average temperatures, heat loss without conduction correction, mean heating rate, least squares heating rate, and the percent standard error of the least squares heating rates. The input tape used is produced by the program EHTS03.

KSC-2009-6811

NASA Image and Video Library

2009-12-14

CAPE CANAVERAL, Fla. - In Orbiter Processing Facility Bay 1 at NASA's Kennedy Space Center in Florida, United Space Alliance technician Jeff Holmes uses heat lamps in a putty repair on some of the high-temperature reusable surface insulation tiles, or HRSI tiles, on the lower forward fuselage of space shuttle Atlantis. An average of 125 tiles are replaced after each mission either due to handling damage or accumulated repairs. These black tiles are optimized for maximum emissivity, which means they lose heat faster than white tiles. This property is required to maximize heat rejection during the hot phase of reentry. Atlantis next is slated to deliver an Integrated Cargo Carrier and Russian-built Mini Research Module to the International Space Station on the STS-132 mission. Launch is targeted for May 14, 2010. Photo credit: NASA/Jack Pfaller

KSC-2009-6812

NASA Image and Video Library

2009-12-14

CAPE CANAVERAL, Fla. - In Orbiter Processing Facility Bay 1 at NASA's Kennedy Space Center in Florida, heat lamps assist United Space Alliance technician Jeff Holmes in a putty repair on some of the high-temperature reusable surface insulation tiles, or HRSI tiles, on the lower forward fuselage of space shuttle Atlantis. An average of 125 tiles are replaced after each mission either due to handling damage or accumulated repairs. These black tiles are optimized for maximum emissivity, which means they lose heat faster than white tiles. This property is required to maximize heat rejection during the hot phase of reentry. Atlantis next is slated to deliver an Integrated Cargo Carrier and Russian-built Mini Research Module to the International Space Station on the STS-132 mission. Launch is targeted for May 14, 2010. Photo credit: NASA/Jack Pfaller

Validation of radio-frequency dielectric heating system for destruction of Cronobacter sakazakii and Salmonella species in nonfat dry milk.

PubMed

Michael, M; Phebus, R K; Thippareddi, H; Subbiah, J; Birla, S L; Schmidt, K A

2014-12-01

Cronobacter sakazakii and Salmonella species have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. Cronobacter sakazakii and Salmonella spp. can survive the spray-drying process if milk is contaminated after pasteurization, and the dried product can be contaminated from environmental sources. Compared with conventional heating, radio-frequency dielectric heating (RFDH) is a faster and more uniform process for heating low-moisture foods. The objective of this study was to design an RFDH process to achieve target destruction (log reductions) of C. sakazakii and Salmonella spp. The thermal destruction (decimal reduction time; D-value) of C. sakazakii and Salmonella spp. in NDM (high-heat, HH; and low-heat, LH) was determined at 75, 80, 85, or 90 °C using a thermal-death-time (TDT) disk method, and the z-values (the temperature increase required to obtain a decimal reduction of the D-value) were calculated. Time and temperature requirements to achieve specific destruction of the pathogens were calculated from the thermal destruction parameters, and the efficacy of the RFDH process was validated by heating NDM using RFDH to achieve the target temperatures and holding the product in a convection oven for the required period. Linear regression was used to determine the D-values and z-values. The D-values of C. sakazakii in HH- and LH-NDM were 24.86 and 23.0 min at 75 °C, 13.75 and 7.52 min at 80 °C, 8.0 and 6.03 min at 85 °C, and 5.57 and 5.37 min at 90 °C, respectively. The D-values of Salmonella spp. in HH- and LH-NDM were 23.02 and 24.94 min at 75 °C, 10.45 and 12.54 min at 80 °C, 8.63 and 8.68 min at 85 °C, and 5.82 and 4.55 min at 90 °C, respectively. The predicted and observed destruction of C. sakazakii and Salmonella spp. were in agreement, indicating that the behavior of the organisms was similar regardless of the heating system (conventional vs. RFDH). Radio-frequency dielectric heating can be used as a faster and more uniform heating method for NDM to achieve target temperatures for a postprocess lethality treatment of NDM before packaging. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Faster Self-paced Rate of Drinking for Alcohol Mixed with Energy Drinks versus Alcohol Alone

PubMed Central

Marczinski, Cecile A.; Fillmore, Mark T.; Maloney, Sarah F.; Stamates, Amy L.

2016-01-01

The consumption of alcohol mixed with energy drinks (AmED) has been associated with higher rates of binge drinking and impaired driving when compared to alcohol alone. However, it remains unclear why the risks of use of AmED are heightened compared to alcohol alone even when the doses of alcohol consumed are similar. Therefore, the purpose of this laboratory study was to investigate if the rate of self-paced beverage consumption was faster for a dose of AmED versus alcohol alone using a double-blind, within-subjects, placebo-controlled study design. Participants (n = 16) of equal gender who were social drinkers attended 4 separate test sessions that involved consumption of alcohol (1.97 ml/kg vodka) and energy drinks, alone and in combination. On each test day, the dose assigned was divided into 10 cups. Participants were informed that they would have a two hour period to consume the 10 drinks. After the self-paced drinking period, participants completed a cued go/no-go reaction time task and subjective ratings of stimulation and sedation. The results indicated that participants consumed the AmED dose significantly faster (by approximately 16 minutes) than the alcohol dose. For the performance task, participants’ mean reaction times were slower in the alcohol conditions and faster in the energy drink conditions. In conclusion, alcohol consumers should be made aware that rapid drinking might occur for AmED beverages thus heightening alcohol-related safety risks. The fast rate of drinking may be related to the generalized speeding of responses following energy drink consumption. PMID:27819431

Effects of music tempo upon submaximal cycling performance.

PubMed

Waterhouse, J; Hudson, P; Edwards, B

2010-08-01

In an in vivo laboratory controlled study, 12 healthy male students cycled at self-chosen work-rates while listening to a program of six popular music tracks of different tempi. The program lasted about 25 min and was performed on three occasions--unknown to the participants, its tempo was normal, increased by 10% or decreased by 10%. Work done, distance covered and cadence were measured at the end of each track, as were heart rate and subjective measures of exertion, thermal comfort and how much the music was liked. Speeding up the music program increased distance covered/unit time, power and pedal cadence by 2.1%, 3.5% and 0.7%, respectively; slowing the program produced falls of 3.8%, 9.8% and 5.9%. Average heart rate changes were +0.1% (faster program) and -2.2% (slower program). Perceived exertion and how much the music was liked increased (faster program) by 2.4% and 1.3%, respectively, and decreased (slower program) by 3.6% and 35.4%. That is, healthy individuals performing submaximal exercise not only worked harder with faster music but also chose to do so and enjoyed the music more when it was played at a faster tempo. Implications of these findings for improving training regimens are discussed.

RATES OF SOLVOLYSIS OF SOME DEUTERATED 2-PHENYLETHYL p-TOLUENESULFONATES

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

Saunders, W.H. Jr.; Asperger, S.; Edison, D.H.

1958-05-20

Rates of solvolysis of 2-phenylethyl (Ia), b 2/ (Ic) p-toluenesulfonates were determined in formic and in acetic acid. In formolysis Ia and Ic react at the same rate, but Ia reacts 17 plus or minus 2% faster than Ib. In acetolysis small effects are observed with both deuterated com. pounds: Ia is 3 plus or minus 1% faster than Ib and 4 plus or minus 3% faster than Ic. The formates and acetates produced in the solvolyses were converted to the corresponding 2phenylethanols II. Comparison of the infrared spectra of the products with those of synthetic mixture of IIb andmore » IIc revealed that ca. 45% phenyl migration had occurred in the formolysis and ca. 10% phenyl migration in acetolysis. These results suggest that phenyl participation predominates in formolysis, but is unimportant in acetolysis. The nature of the transition state in phenyl- participation reactions and the factors contributing to secondary deuterium isotope effects are discussed. (auth)« less

High Heating Rates Affect Greatly the Inactivation Rate of Escherichia coli.

PubMed

Huertas, Juan-Pablo; Aznar, Arantxa; Esnoz, Arturo; Fernández, Pablo S; Iguaz, Asunción; Periago, Paula M; Palop, Alfredo

2016-01-01

Heat resistance of microorganisms can be affected by different influencing factors. Although, the effect of heating rates has been scarcely explored by the scientific community, recent researches have unraveled its important effect on the thermal resistance of different species of vegetative bacteria. Typically heating rates described in the literature ranged from 1 to 20°C/min but the impact of much higher heating rates is unclear. The aim of this research was to explore the effect of different heating rates, such as those currently achieved in the heat exchangers used in the food industry, on the heat resistance of Escherichia coli. A pilot plant tubular heat exchanger and a thermoresistometer Mastia were used for this purpose. Results showed that fast heating rates had a deep impact on the thermal resistance of E. coli. Heating rates between 20 and 50°C/min were achieved in the heat exchanger, which were much slower than those around 20°C/s achieved in the thermoresistometer. In all cases, these high heating rates led to higher inactivation than expected: in the heat exchanger, for all the experiments performed, when the observed inactivation had reached about seven log cycles, the predictions estimated about 1 log cycle of inactivation; in the thermoresistometer these differences between observed and predicted values were even more than 10 times higher, from 4.07 log cycles observed to 0.34 predicted at a flow rate of 70 mL/min and a maximum heating rate of 14.7°C/s. A quantification of the impact of the heating rates on the level of inactivation achieved was established. These results point out the important effect that the heating rate has on the thermal resistance of E. coli, with high heating rates resulting in an additional sensitization to heat and therefore an effective food safety strategy in terms of food processing.

High Heating Rates Affect Greatly the Inactivation Rate of Escherichia coli

PubMed Central

Huertas, Juan-Pablo; Aznar, Arantxa; Esnoz, Arturo; Fernández, Pablo S.; Iguaz, Asunción; Periago, Paula M.; Palop, Alfredo

2016-01-01

Heat resistance of microorganisms can be affected by different influencing factors. Although, the effect of heating rates has been scarcely explored by the scientific community, recent researches have unraveled its important effect on the thermal resistance of different species of vegetative bacteria. Typically heating rates described in the literature ranged from 1 to 20°C/min but the impact of much higher heating rates is unclear. The aim of this research was to explore the effect of different heating rates, such as those currently achieved in the heat exchangers used in the food industry, on the heat resistance of Escherichia coli. A pilot plant tubular heat exchanger and a thermoresistometer Mastia were used for this purpose. Results showed that fast heating rates had a deep impact on the thermal resistance of E. coli. Heating rates between 20 and 50°C/min were achieved in the heat exchanger, which were much slower than those around 20°C/s achieved in the thermoresistometer. In all cases, these high heating rates led to higher inactivation than expected: in the heat exchanger, for all the experiments performed, when the observed inactivation had reached about seven log cycles, the predictions estimated about 1 log cycle of inactivation; in the thermoresistometer these differences between observed and predicted values were even more than 10 times higher, from 4.07 log cycles observed to 0.34 predicted at a flow rate of 70 mL/min and a maximum heating rate of 14.7°C/s. A quantification of the impact of the heating rates on the level of inactivation achieved was established. These results point out the important effect that the heating rate has on the thermal resistance of E. coli, with high heating rates resulting in an additional sensitization to heat and therefore an effective food safety strategy in terms of food processing. PMID:27563300

Energy and material flows of megacities

PubMed Central

Kennedy, Christopher A.; Stewart, Iain; Facchini, Angelo; Cersosimo, Igor; Mele, Renata; Chen, Bin; Uda, Mariko; Kansal, Arun; Chiu, Anthony; Kim, Kwi-gon; Dubeux, Carolina; Lebre La Rovere, Emilio; Cunha, Bruno; Pincetl, Stephanie; Keirstead, James; Barles, Sabine; Pusaka, Semerdanta; Gunawan, Juniati; Adegbile, Michael; Nazariha, Mehrdad; Hoque, Shamsul; Marcotullio, Peter J.; González Otharán, Florencia; Genena, Tarek; Ibrahim, Nadine; Farooqui, Rizwan; Cervantes, Gemma; Sahin, Ahmet Duran

2015-01-01

Understanding the drivers of energy and material flows of cities is important for addressing global environmental challenges. Accessing, sharing, and managing energy and material resources is particularly critical for megacities, which face enormous social stresses because of their sheer size and complexity. Here we quantify the energy and material flows through the world’s 27 megacities with populations greater than 10 million people as of 2010. Collectively the resource flows through megacities are largely consistent with scaling laws established in the emerging science of cities. Correlations are established for electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of heating-degree-days, urban form, economic activity, and population growth. The results help identify megacities exhibiting high and low levels of consumption and those making efficient use of resources. The correlation between per capita electricity use and urbanized area per capita is shown to be a consequence of gross building floor area per capita, which is found to increase for lower-density cities. Many of the megacities are growing rapidly in population but are growing even faster in terms of gross domestic product (GDP) and energy use. In the decade from 2001–2011, electricity use and ground transportation fuel use in megacities grew at approximately half the rate of GDP growth. PMID:25918371

Energy and material flows of megacities.

PubMed

Kennedy, Christopher A; Stewart, Iain; Facchini, Angelo; Cersosimo, Igor; Mele, Renata; Chen, Bin; Uda, Mariko; Kansal, Arun; Chiu, Anthony; Kim, Kwi-Gon; Dubeux, Carolina; Lebre La Rovere, Emilio; Cunha, Bruno; Pincetl, Stephanie; Keirstead, James; Barles, Sabine; Pusaka, Semerdanta; Gunawan, Juniati; Adegbile, Michael; Nazariha, Mehrdad; Hoque, Shamsul; Marcotullio, Peter J; González Otharán, Florencia; Genena, Tarek; Ibrahim, Nadine; Farooqui, Rizwan; Cervantes, Gemma; Sahin, Ahmet Duran

2015-05-12

Understanding the drivers of energy and material flows of cities is important for addressing global environmental challenges. Accessing, sharing, and managing energy and material resources is particularly critical for megacities, which face enormous social stresses because of their sheer size and complexity. Here we quantify the energy and material flows through the world's 27 megacities with populations greater than 10 million people as of 2010. Collectively the resource flows through megacities are largely consistent with scaling laws established in the emerging science of cities. Correlations are established for electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of heating-degree-days, urban form, economic activity, and population growth. The results help identify megacities exhibiting high and low levels of consumption and those making efficient use of resources. The correlation between per capita electricity use and urbanized area per capita is shown to be a consequence of gross building floor area per capita, which is found to increase for lower-density cities. Many of the megacities are growing rapidly in population but are growing even faster in terms of gross domestic product (GDP) and energy use. In the decade from 2001-2011, electricity use and ground transportation fuel use in megacities grew at approximately half the rate of GDP growth.

Spray Bar Zero-Gravity Vent System for On-Orbit Liquid Hydrogen Storage

NASA Technical Reports Server (NTRS)

Hastings, L. J.; Flachbart, R. H.; Martin, J. J.; Hedayat, A.; Fazah, M.; Lak, T.; Nguyen, H.; Bailey, J. W.

2003-01-01

During zero-gravity orbital cryogenic propulsion operations, a thermodynamic vent system (TVS) concept is expected to maintain tank pressure control without propellant resettling. In this case, a longitudinal spray bar mixer system, coupled with a Joule-Thompson (J-T) valve and heat exchanger, was evaluated in a series of TVS tests using the 18 cu m multipurpose hydrogen test bed. Tests performed at fill levels of 90, 50, and 25 percent, coupled with heat tank leaks of about 20 and 50 W, successfully demonstrated tank pressure control within a 7-kPa band. Based on limited testing, the presence of helium constrained the energy exchange between the gaseous and liquid hydrogen (LH2) during the mixing cycles. A transient analytical model, formulated to characterize TVS performance, was used to correlate the test data. During self-pressurization cycles following tank lockup, the model predicted faster pressure rise rates than were measured; however, once the system entered the cyclic self-pressurization/mixing/venting operational mode, the modeled and measured data were quite similar. During a special test at the 25-percent fill level, the J-T valve was allowed to remain open and successfully reduced the bulk LH2 saturation pressure from 133 to 70 kPa in 188 min.

Performance enhancement of fin attached ice-on-coil type thermal storage tank for different fin orientations using constrained and unconstrained simulations

NASA Astrophysics Data System (ADS)

Kim, M. H.; Duong, X. Q.; Chung, J. D.

2017-03-01

One of the drawbacks in latent thermal energy storage system is the slow charging and discharging time due to the low thermal conductivity of the phase change materials (PCM). This study numerically investigated the PCM melting process inside a finned tube to determine enhanced heat transfer performance. The influences of fin length and fin numbers were investigated. Also, two different fin orientations, a vertical and horizontal type, were examined, using two different simulation methods, constrained and unconstrained. The unconstrained simulation, which considers the density difference between the solid and liquid PCM showed approximately 40 % faster melting rate than that of constrained simulation. For a precise estimation of discharging performance, unconstrained simulation is essential. Thermal instability was found in the liquid layer below the solid PCM, which is contrary to the linear stability theory, due to the strong convection driven by heat flux from the coil wall. As the fin length increases, the area affected by the fin becomes larger, thus the discharging time becomes shorter. The discharging performance also increased as the fin number increased, but the enhancement of discharging performance by more than two fins was not discernible. The horizontal type shortened the complete melting time by approximately 10 % compared to the vertical type.

Design of High Frequency Pulse Tube Cryocooler for Onboard Space Applications

NASA Astrophysics Data System (ADS)

Srikanth, Thota; Padmanabhan; Gurudath, C. S.; Amrit, A.; Basavaraj, S.; Dinesh, K.

2017-02-01

To meet the growing demands of on-board applications such as cooling meteorological payloads and the satellite operational constraints like power, lower mass, reduced size and redundancy; a Pulse Tube Cryocooler (PTC) is designed by arriving at an operating frequency of 100 Hz and Helium gas pressure of 35 bar based on insights obtained from combination of phasor diagram, pulse tube and regenerator geometries with overall system mass of ≤ 2.0 kg. High frequency operation would allow reducing the size and mass of pressure wave modulator for a given input power. High Frequency also helps in reducing the volume of regenerator for a given cooling power, which increases the power density and leads to faster cool down. A component level modelling of the regenerator for optimising length and diameter for maximum Coefficient of Performance (COP) is carried out using REGEN3.3. The overall system level modelling of PTC is carried out using 1-D software SAGE. The cold end mass flow rate of the optimised regenerator is taken as reference for the system modelling. The performance achieved in REGEN3.3 is 2.15 W of net heat lift against the performance of 1.02 W of net heat lift at 80 K in SAGE.

An approximate viscous shock layer technique for calculating chemically reacting hypersonic flows about blunt-nosed bodies

NASA Technical Reports Server (NTRS)

Cheatwood, F. Mcneil; Dejarnette, Fred R.

1991-01-01

An approximate axisymmetric method was developed which can reliably calculate fully viscous hypersonic flows over blunt nosed bodies. By substituting Maslen's second order pressure expression for the normal momentum equation, a simplified form of the viscous shock layer (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the shock layer without a starting solution for the shock shape. The approach is applicable to perfect gas, equilibrium, and nonequilibrium flowfields. Since the method is fully viscous, the problems associated with a boundary layer solution with an inviscid layer solution are avoided. This procedure is significantly faster than the parabolized Navier-Stokes (PNS) or VSL solvers and would be useful in a preliminary design environment. Problems associated with a previously developed approximate VSL technique are addressed before extending the method to nonequilibrium calculations. Perfect gas (laminar and turbulent), equilibrium, and nonequilibrium solutions were generated for airflows over several analytic body shapes. Surface heat transfer, skin friction, and pressure predictions are comparable to VSL results. In addition, computed heating rates are in good agreement with experimental data. The present technique generates its own shock shape as part of its solution, and therefore could be used to provide more accurate initial shock shapes for higher order procedures which require starting solutions.

Two-temperature equilibration in warm dense hydrogen measured with x-ray scattering from the LCLS

NASA Astrophysics Data System (ADS)

Fletcher, Luke; High Energy Density Sciences Collaboration

2017-10-01

Understanding the properties of warm dense hydrogen plasmas is critical for modeling stellar and planetary interiors, as well as for inertial confinement fusion (ICF) experiments. Of central importance are the electron-ion collision and equilibration times that determine the microscopic properties in a high energy density state. Spectrally and angularly resolved x-ray scattering measurements from fs-laser heated hydrogen have resolved the picosecond evolution and energy relaxation from a two-temperature plasma towards thermodynamic equilibrium in the warm dense matter regime. The interaction of rapidly heated cryogenic hydrogen irradiated by a 400 nm, 5x1017 W/cm2 , 70 fs-laser is visualized with ultra-bright 5.5 kev x-ray pulses from the Linac Coherent Light (LCLS) source in 1 Hz repetition rate pump-probe setting. We demonstrate that the energy relaxation is faster than many classical binary collision theories that use ad hoc cutoff parameters used in the Landau-Spitzer determination of the Coulomb logarithm. This work was supported by the DOE Office of Science, Fusion Energy Science under contract No. SF00515 and supported under FWP 100182 and DOE Office of Basic Energy Sciences, Materials Sciences and Engineering Division, contract DE-AC02-76SF00515.

Physiologic and Perceptual Responses to Cold-Shower Cooling After Exercise-Induced Hyperthermia

PubMed Central

Butts, Cory L.; McDermott, Brendon P.; Buening, Brian J.; Bonacci, Jeffrey A.; Ganio, Matthew S.; Adams, J. D.; Tucker, Matthew A.; Kavouras, Stavros A.

2016-01-01

Context:  Exercise conducted in hot, humid environments increases the risk for exertional heat stroke (EHS). The current recommended treatment of EHS is cold-water immersion; however, limitations may require the use of alternative resources such as a cold shower (CS) or dousing with a hose to cool EHS patients. Objective:  To investigate the cooling effectiveness of a CS after exercise-induced hyperthermia. Design:  Randomized, crossover controlled study. Setting:  Environmental chamber (temperature = 33.4°C ± 2.1°C; relative humidity = 27.1% ± 1.4%). Patients or Other Participants:  Seventeen participants (10 male, 7 female; height = 1.75 ± 0.07 m, body mass = 70.4 ± 8.7 kg, body surface area = 1.85 ± 0.13 m2, age range = 19–35 years) volunteered. Intervention(s):  On 2 occasions, participants completed matched-intensity volitional exercise on an ergometer or treadmill to elevate rectal temperature to ≥39°C or until participant fatigue prevented continuation (reaching at least 38.5°C). They were then either treated with a CS (20.8°C ± 0.80°C) or seated in the chamber (control [CON] condition) for 15 minutes. Main Outcome Measure(s):  Rectal temperature, calculated cooling rate, heart rate, and perceptual measures (thermal sensation and perceived muscle pain). Results:  The rectal temperature (P = .98), heart rate (P = .85), thermal sensation (P = .69), and muscle pain (P = .31) were not different during exercise for the CS and CON trials (P > .05). Overall, the cooling rate was faster during CS (0.07°C/min ± 0.03°C/min) than during CON (0.04°C/min ± 0.03°C/min; t16 = 2.77, P = .01). Heart-rate changes were greater during CS (45 ± 20 beats per minute) compared with CON (27 ± 10 beats per minute; t16 = 3.32, P = .004). Thermal sensation was reduced to a greater extent with CS than with CON (F3,45 = 41.12, P < .001). Conclusions:  Although the CS facilitated cooling rates faster than no treatment, clinicians should continue to advocate for accepted cooling modalities and use CS only if no other validated means of cooling are available. PMID:26942657

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

Basak, Sushovan, E-mail: sushovanbasak@gmail.com; Das, Hrishikesh, E-mail: hrishichem@gmail.com; Pal, Tapan Kumar, E-mail: tkpal.ju@gmail.com

In order to meet the demand for lighter and more fuel efficient vehicles, a significant attempt is currently being focused toward the substitution of aluminum for steel in the car body structure. It generates vital challenge with respect to the methods of joining to be used for fabrication. However, the conventional fusion joining has its own difficulty owing to formation of the brittle intermetallic phases. In this present study AA6061-T6 of 2 mm and HIF-GA steel sheet of 1 mm thick are metal inert gas (MIG) brazed with 0.8 mm Al–5Si filler wire under three different heat inputs. The effectmore » of the heat inputs on bead geometry, microstructure and joint properties of MIG brazed Al-steel joints were exclusively studied and characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), electron probe micro analyzer (EPMA) and high resolution transmission electron microscopy (HRTEM) assisted X-ray spectroscopy (EDS) and selective area diffraction pattern. Finally microstructures were correlated with the performance of the joint. Diffusion induced intermetallic thickness measured by FESEM image and concentration profile agreed well with the numerically calculated one. HRTEM assisted EDS study was used to identify the large size FeAl{sub 3} and small size Fe{sub 2}Al{sub 5} type intermetallic compounds at the interface. The growth of these two phases in A2 (heat input: 182 J mm{sup −1}) is attributed to the slower cooling rate with higher diffusion time (~ 61 s) along the interface in comparison to the same for A1 (heat input: 155 J mm{sup −1}) with faster cooling rate and shorter diffusion time (~ 24 s). The joint efficiency as high as 65% of steel base metal is achieved for A2 which is the optimized parameter in the present study. - Highlights: • AA 6061 and HIF-GA could be successfully joined by MIG brazing. • Intermetallics are exclusively studied and characterized by XRD, FESEM and EPMA. • Intermetallic formation by diffusion is worth considering or not. • HRTEM-EDS, SAD pattern identifies the morphologies and size of intermetallics. • A compromise concerning formation of IMC is necessary.« less

Muscular Oxygen Uptake Kinetics in Aged Adults.

PubMed

Koschate, J; Drescher, U; Baum, K; Eichberg, S; Schiffer, T; Latsch, J; Brixius, K; Hoffmann, U

2016-06-01

Pulmonary oxygen uptake (V˙O2) kinetics and heart rate kinetics are influenced by age and fitness. Muscular V˙O2 kinetics can be estimated from heart rate and pulmonary V˙O2. In this study the applicability of a test using pseudo-random binary sequences in combination with a model to estimate muscular V˙O2 kinetics was tested. Muscular V˙O2 kinetics were expected to be faster than pulmonary V˙O2 kinetics, slowed in aged subjects and correlated with maximum V˙O2 and heart rate kinetics. 27 elderly subjects (73±3 years; 81.1±8.2 kg; 175±4.7 cm) participated. Cardiorespiratory kinetics were assessed using the maximum of cross-correlation functions, higher maxima implying faster kinetics. Muscular V˙O2 kinetics were faster than pulmonary V˙O2 kinetics (0.31±0.1 vs. 0.29±0.1 s; p=0.004). Heart rate kinetics were not correlated with muscular or pulmonary V˙O2 kinetics or maximum V˙O2. Muscular V˙O2 kinetics correlated with maximum V˙O2 (r=0.35; p=0.033). This suggests, that muscular V˙O2 kinetics are faster than estimates from pulmonary V˙O2 and related to maximum V˙O2 in aged subjects. In the future this experimental approach may help to characterize alterations in muscular V˙O2 under various conditions independent of motivation and maximal effort. © Georg Thieme Verlag KG Stuttgart · New York.

Effects of shape and size of agar gels on heating uniformity during pulsed microwave treatment.

PubMed

Soto-Reyes, Nohemí; Temis-Pérez, Ana L; López-Malo, Aurelio; Rojas-Laguna, Roberto; Sosa-Morales, María Elena

2015-05-01

Model gel systems with different shape (sphere, cylinder, and slab) and size (180 and 290 g) were prepared with agar (5%) and sucrose (5%). Dielectric constant (ε'), loss factor (ε"), thermophysical properties, and temperature distribution of the model system were measured. Each agar model system was immersed and suspended in water, and then, heated in a microwave oven with intermittent heating until the core temperature reached 50 °C. The ε' and ε" of agar gels decreased when frequency increased. The density and thermal conductivity values of the agar gels were 1033 kg/m(3) and 0.55 W/m °C, respectively. The temperature distribution of sphere, cylinder, and slab was different when similar power doses were applied. The slab reached 50 °C in less time (10 min) and showed a more uniform heating than spheres and cylinders in both sizes. Agar model systems of 180 g heated faster than those of 290 g. The coldest point was the center of the model systems in all studied cases. Shape and size are critical food factors that affect the heating uniformity during microwave heating processes. © 2015 Institute of Food Technologists®

Magnetic Heating of Iron Oxide Nanoparticles and Magnetic Micelles for Cancer Therapy.

PubMed

Glover, Amanda L; Bennett, James B; Pritchett, Jeremy S; Nikles, Sarah M; Nikles, David E; Nikles, Jacqueline A; Brazel, Christopher S

2013-01-01

The inclusion of magnetic nanoparticles into block copolymer micelles was studied towards the development of a targeted, magnetically triggered drug delivery system for cancer therapy. Herein, we report the synthesis of magnetic nanoparticles and poly(ethylene glycol-b-caprolactone) block copolymers, and experimental verification of magnetic heating of the nanoparticles, self-assembly of the block copolymers to form magnetic micelles, and thermally-enhanced drug release. The semicrystalline core of the micelles melted at temperatures just above physiological conditions, indicating that they could be used to release a chemotherapy agent from a thermo-responsive polymer system. The magnetic nanoparticles were shown to heat effectively in high frequency magnetic fields ranging from 30-70 kA/m. Magnetic micelles also showed heating properties, that when combined with a chemotherapeutic agent and a targeting ligand could be developed for localized, triggered drug delivery. During the magnetic heating experiments, a time lag was observed in the temperature profile for magnetic micelles, likely due to the heat of fusion of melting of polycaprolactone micelle cores before bulk solution temperatures increased. Doxorubicin, incorporated into the micelles, released faster when the micelles were heated above the core melting point.

Modeling of cryopreservation of engineered tissues with one-dimensional geometry.

PubMed

Cui, Z F; Dykhuizen, R C; Nerem, R M; Sembanis, A

2002-01-01

Long-term storage of engineered bio-artificial tissues is required to ensure the off-the-shelf availability to clinicians due to their long production cycle. Cryopreservation is likely the choice for long-term preservation. Although the cryopreservation of cells is well established for many cell types, cryopreservation of tissues is far more complicated. Cells at different locations in the tissue could experience very different local environmental changes, i.e., the change of concentration of cryoprotecting chemicals (CPA) and temperature, during the addition/removal of CPA and cooling/warming, which leads to nonuniformity in cell survival in the tissue. This is due to the limitation of mass and heat transfer within the tissue. A specific aim of cryopreservation of tissue is to ensure a maximum recovery of cells and their functionality throughout a tissue. Cells at all locations should be protected adequately by the CPA and frozen at rates conducive to survival. It is hence highly desirable to know the cell transient and final states during cryopreservation within the whole tissue, which can be best studied by mathematical modeling. In this work, a model framework for cryopreservation of one-dimensional artificial tissues is developed on the basis of solving the coupled equations to describe the mass and heat transfer within the tissue and osmotic transport through the cell membrane. Using an artificial pancreas as an example, we carried out a simulation to examine the temperature history, cell volume, solute redistribution, and other state parameters during the freezing of the spherical heterogeneous construct (a single bead). It is found that the parameters affecting the mass transfer of CPA in tissue and through the cell membrane and the freezing rate play dominant roles in affecting the cell volume transient and extracellular ice formation. Thermal conductivity and extracellular ice formation kinetics, on the other hand, have little effect on cell transient and final states, as the heat transfer rate is much faster than mass diffusion. The outcome of such a model study can be used to evaluate the construct design on its survivability during cryopreservation and to select a cryopreservation protocol to achieve maximum cell survival.

Time-domain measurement of optical transport in silicon micro-ring resonators.

PubMed

Pernice, Wolfram H P; Li, Mo; Tang, Hong X

2010-08-16

We perform time-domain measurements of optical transport dynamics in silicon nano-photonic devices. Using pulsed optical excitation the thermal and carrier induced optical nonlinearities of micro-ring resonators are investigated, allowing for identification of their individual contributions. Under pulsed excitation build-up of free carriers and heat in the waveguides leads to a beating oscillation of the cavity resonance frequency. When employing a burst of pulse trains shorter than the carrier life-time, the slower heating effect can be separated from the faster carrier effect. Our scheme provides a convenient way to thermally stabilize optical resonators for high-power time-domain applications and nonlinear optical conversion.

Thermal Inactivation of Aerosolized Bacillus subtilis var. niger Spores

PubMed Central

Mullican, Charles L.; Buchanan, Lee M.; Hoffman, Robert K.

1971-01-01

A hot-air sterilizer capable of exposing airborne microorganisms to elevated temperatures with an almost instantaneous heating time was developed and evaluated. With this apparatus, aerosolized Bacillus subtilis var. niger spores were killed in about 0.02 sec when exposed to temperatures above 260 C. This is about 500 times faster than killing times reported by others. Extrapolation and comparison of data on the time and temperature required to klll B. subtilis var. niger spores on surfaces show that approximately the same killing time is required as is necessary for spores in air, if corrections are made for the heating time of the surface. PMID:5002138

The ‘neutron deficit’ in the JET tokamak

NASA Astrophysics Data System (ADS)

Weisen, H.; Kim, Hyun-Tae; Strachan, J.; Scott, S.; Baranov, Y.; Buchanan, J.; Fitzgerald, M.; Keeling, D.; King, D. B.; Giacomelli, L.; Koskela, T.; Weisen, M. J.; Giroud, C.; Maslov, M.; Core, W. G.; Zastrow, K.-D.; Syme, D. B.; Popovichev, S.; Conroy, S.; Lengar, I.; Snoj, L.; Batistoni, P.; Santala, M.; Contributors, JET

2017-07-01

The measured D-D neutron rate of neutral beam heated JET baseline and hybrid H-modes in deuterium is found to be between approximately 50% and 100% of the neutron rate expected from the TRANSP code, depending on the plasma parameters. A number of candidate explanations for the shortfall, such as fuel dilution, errors in beam penetration and effectively available beam power have been excluded. As the neutron rate in JET is dominated by beam-plasma interactions, the ‘neutron deficit’ may be caused by a yet unidentified form of fast particle redistribution. Modelling, which assumes fast particle transport to be responsible for the deficit, indicates that such redistribution would have to happen at time scales faster than both the slowing down time and the energy confinement time. Sawteeth and edge localised modes are found to make no significant contribution to the deficit. There is also no obvious correlation with magnetohydrodynamic activity measured using magnetic probes at the tokamak vessel walls. Modelling of fast particle orbits in the 3D fields of neoclassical tearing modes shows that realistically sized islands can only contribute a few percent to the deficit. In view of these results it appears unlikely that the neutron deficit results from a single physical process in the plasma.

Microstructural Characterization of a Polycrystalline Nickel-Based Superalloy Processed via Tungsten-Intert-Gas-Shaped Metal Deposition

NASA Astrophysics Data System (ADS)

Clark, Daniel; Bache, Martin R.; Whittaker, Mark T.

2010-12-01

Recent trials have produced tungsten-inert-gas (TIG)-welded structures of a suitable scale to allow an evaluation of the technique as an economic and commercial process for the manufacture of complex aeroengine components. The employment of TIG welding is shown to have specific advantages over alternative techniques based on metal inert gas (MIG) systems. Investigations using the nickel-based superalloy 718 have shown that TIG induces a smaller weld pool with less compositional segregation. In addition, because the TIG process involves a pulsed power source, a faster cooling rate is achieved, although this rate, in turn, compromises the deposition rate. The microstructures produced by the two techniques differ significantly, with TIG showing an absence of the detrimental delta and Laves phases typically produced by extended periods at a high temperature using MIG. Instead, an anisotropic dendritic microstructure was evident with a preferred orientation relative to the axis of epitaxy. Niobium was segregated to the interdendritic regions. A fine-scale porosity was evident within the microstructure with a maximum diameter of approximately 5 μm. This porosity often was found in clusters and usually was associated with the interdendritic regions. Subsequent postdeposition heat treatment was shown to have no effect on preexisting porosity and to have a minimal effect on the microstructure.

Radio-manganese, -iron, -phosphorus uptake by water hyacinth and economic implications

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

Colley, T.N.; Gonzalez, M.H.; Martin, D.F.

To determine the effects of the deprivation of specific micronutrients on the water hyacinth (Eichhornia crassipes), the rate of uptake by the water hyacinth of iron and manganese in comparison with phosphorus was studied. Materials and methodology are described. Experimentation indicates that all three elements are actively absorbed by the root systems, but the rates of absorption differ markedly. The rate of absorption of manganese by roots is 13 and 21 times that for radio-iron and -phosphorous, and iron was taken up by the roots at nearly twice the rate of phosphorous. Manganese translocation appeared to be faster than phosphorusmore » translocation by an order of magnitude and 65 times faster than iron translocation. 9 references, 2 tables.« less

Heat transfer in a microvascular network: the effect of heart rate on heating and cooling in reptiles (Pogona barbata and Varanus varius).

PubMed

Seebacher, F

2000-03-21

Thermally-induced changes in heart rate and blood flow in reptiles are believed to be of selective advantage by allowing animal to exert some control over rates of heating and cooling. This notion has become one of the principal paradigms in reptilian thermal physiology. However, the functional significance of changes in heart rate is unclear, because the effect of heart rate and blood flow on total animal heat transfer is not known. I used heat transfer theory to determine the importance of heat transfer by blood flow relative to conduction. I validated theoretical predictions by comparing them with field data from two species of lizard, bearded dragons (Pogona barbata) and lace monitors (Varanus varius). Heart rates measured in free-ranging lizards in the field were significantly higher during heating than during cooling, and heart rates decreased with body mass. Convective heat transfer by blood flow increased with heart rate. Rates of heat transfer by both blood flow and conduction decreased with mass, but the mass scaling exponents were different. Hence, rate of conductive heat transfer decreased more rapidly with increasing mass than did heat transfer by blood flow, so that the relative importance of blood flow in total animal heat transfer increased with mass. The functional significance of changes in heart rate and, hence, rates of heat transfer, in response to heating and cooling in lizards was quantified. For example, by increasing heart rate when entering a heating environment in the morning, and decreasing heart rate when the environment cools in the evening a Pogona can spend up to 44 min longer per day with body temperature within its preferred range. It was concluded that changes in heart rate in response to heating and cooling confer a selective advantage at least on reptiles of mass similar to that of the study animals (0. 21-5.6 kg). Copyright 2000 Academic Press.

Treatment of munitions in soils using phytoslurries.

PubMed

Medina, Victor F; Larson, Steven L; Agwaramgbo, Lovell; Perez, Waleska

2002-01-01

Phytoremediation is an established technology for the treatment of explosives in water and soil. This study investigated the possibility of using slurried plants (or phytoslurries) to treat explosives (TNT and RDX). The degradation of TNT in solution using intact and slurried parrotfeather (Myriophyllum aquaticum), spinach (Spinicia oleracea), and mustard greens (Brassica juncea) was evaluated. Phytoslurries of parrotfeather and spinach removed the TNT faster than the intact plant. Conversely, the removal rate constants for slurried and intact mustard greens were about the same. A study using pressurized heating to destroy enzymatic activity in the phytoslurries was also conducted to compare removal from released plant chemicals to adsorptive removal. Aqueous phase removal of TNT by autoclaved spinach phytoslurry was compared with nonautoclaved spinach phytoslurry. The autoclaved phytoslurry did remove TNT, but not as completely as nonautoclaved slurry. This suggests that some removal is due to adsorption, but not all. Phytoslurries of mustard greens and parrotfeather had higher RDX removal rates compared with intact plant removal, but the rates for parrotfeather in either case were relatively low. Phytoslurries of spinach had relatively modest increases in RDX removal rates compared with intact plant. Studies were then conducted with phytoslurry/soil mixtures at two scales: 60 ml and 1.5 l. In both cases, phytoslurries of mustard greens and spinach removed TNT and RDX at higher levels than control slurries.

Kinetic effect of heating rate on the thermal maturity of carbonaceous material as an indicator of frictional heat during earthquakes

NASA Astrophysics Data System (ADS)

Kaneki, Shunya; Hirono, Tetsuro

2018-06-01

Because the maximum temperature reached in the slip zone is significant information for understanding slip behaviors during an earthquake, the maturity of carbonaceous material (CM) is widely used as a proxy for detecting frictional heat recorded by fault rocks. The degree of maturation of CM is controlled not only by maximum temperature but also by the heating rate. Nevertheless, maximum slip zone temperature has been estimated previously by comparing the maturity of CM in natural fault rocks with that of synthetic products heated at rates of about 1 °C s-1, even though this rate is much lower than the actual heating rate during an earthquake. In this study, we investigated the kinetic effect of the heating rate on the CM maturation process by performing organochemical analyses of CM heated at slow (1 °C s-1) and fast (100 °C s-1) rates. The results clearly showed that a higher heating rate can inhibit the maturation reactions of CM; for example, extinction of aliphatic hydrocarbon chains occurred at 600 °C at a heating rate of 1 °C s-1 and at 900 °C at a heating rate of 100 °C s-1. However, shear-enhanced mechanochemical effects can also promote CM maturation reactions and may offset the effect of a high heating rate. We should thus consider simultaneously the effects of both heating rate and mechanochemistry on CM maturation to establish CM as a more rigorous proxy for frictional heat recorded by fault rocks and for estimating slip behaviors during earthquake.

Effect of heating rate on thermoluminescence output of LiF: Mg, Ti (TLD-100) in dosimetric applications

NASA Astrophysics Data System (ADS)

Singh, Ranjit; Kainth, Harpreet Singh

2018-07-01

The luminiscence characteristics of thermoluminscence dosimeter LiF: Mg, Ti (TLD-100) irradiated to X-rays from 6 MV linac have been studied for wide range of 2-50 K/s readout linear heating rates. The reproducibility of glow curves for TLDs is found to be better at lower heating rates and depreciate at higher heating rates. The glow curve spectra were analysed using deconvolution procedure based on general-order kinetics. Shift in the peak maximum temperature per unit rise in heating rate for various peaks were found to decrease with heating rate. The TLDs irradiated with same dose exhibit decreasing TL counts with increase in the heating rate, which indicate the thermal quenching effect in TLD-100. The value of activation energy for each peak within the glow curve increases with heating rate. Calibration curves plotted for the dose range 0.4-1020 cGy exhibit decreasing slope with increasing readout heating rate. Corrections for temperature lag between the heating element and the dosimeter, and the effective heating rate (βeff) across the sample estimated using formulation proposed by Kitis and Tuyn and are found to be fairly applicable.

Faster self-paced rate of drinking for alcohol mixed with energy drinks versus alcohol alone.

PubMed

Marczinski, Cecile A; Fillmore, Mark T; Maloney, Sarah F; Stamates, Amy L

2017-03-01

The consumption of alcohol mixed with energy drinks (AmED) has been associated with higher rates of binge drinking and impaired driving when compared with alcohol alone. However, it remains unclear why the risks of use of AmED are heightened compared with alcohol alone even when the doses of alcohol consumed are similar. Therefore, the purpose of this laboratory study was to investigate if the rate of self-paced beverage consumption was faster for a dose of AmED versus alcohol alone using a double-blind, within-subjects, placebo-controlled study design. Participants (n = 16) of equal gender who were social drinkers attended 4 separate test sessions that involved consumption of alcohol (1.97 ml/kg vodka) and energy drinks, alone and in combination. On each test day, the dose assigned was divided into 10 cups. Participants were informed that they would have a 2-h period to consume the 10 drinks. After the self-paced drinking period, participants completed a cued go/no-go reaction time (RT) task and subjective ratings of stimulation and sedation. The results indicated that participants consumed the AmED dose significantly faster (by ∼16 min) than the alcohol dose. For the performance task, participants' mean RTs were slower in the alcohol conditions and faster in the energy-drink conditions. In conclusion, alcohol consumers should be made aware that rapid drinking might occur for AmED beverages, thus heightening alcohol-related safety risks. The fast rate of drinking may be related to the generalized speeding of responses after energy-drink consumption. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

A fast response, low heat generating activation method for LHe level sensors

NASA Astrophysics Data System (ADS)

Choudhury, Anup; Sahu, Santosh; Kanjilal, Dinakar

2018-06-01

A superconducting liquid helium (LHe) level sensor of length 300 mm has been fabricated based on the principle of differential heat transfer characteristic in helium gas compared to that in liquid. The sensor wire used has a diameter of 38 μm, and the wire was obtained from a pack of multifilament wires. A full thermo-electrical characterisation of the sensor was carried out in a dedicated setup. Its dynamic thermal response was also studied to understand its timing characteristics at different liquid levels and excitation currents. Based on the sensor characterisation, a new level measurement technique is evaluated which can reduce the heat load going to LHe during sensor activation without compromising on its sensitivity or accuracy. The timing response with this technique will make the level detection faster compared to the conventional techniques.

Faster fertilization rate in conspecific versus heterospecific matings in house mice.

PubMed

Dean, Matthew D; Nachman, Michael W

2009-01-01

Barriers to gene flow can arise at any stage in the reproductive sequence. Most studies of reproductive isolation focus on premating or postzygotic phenotypes, leaving the importance of differences in fertilization rate overlooked. Two closely related species of house mice, Mus domesticus and M. musculus, form a narrow hybrid zone in Europe, suggesting that one or more isolating factors operate in the face of ongoing gene flow. Here, we test for differences in fertilization rate using laboratory matings as well as in vitro sperm competition assays. In noncompetitive matings, we show that fertilization occurs significantly faster in conspecific versus heterospecific matings and that this difference arises after mating and before zygotes form. To further explore the mechanisms underlying this conspecific advantage, we used competitive in vitro assays to isolate gamete interactions. Surprisingly, we discovered that M. musculus sperm consistently outcompeted M. domesticus sperm regardless of which species donated ova. These results suggest that in vivo fertilization rate is mediated by interactions between sperm, the internal female environment, and/or contributions from male seminal fluid. We discuss the implications of faster conspecific fertilization in terms of reproductive isolation among these two naturally hybridizing species.

Music increases alcohol consumption rate in young females.

PubMed

Stafford, Lorenzo D; Dodd, Hannah

2013-10-01

Previous field research has shown that individuals consumed more alcohol and at a faster rate in environments paired with loud music. Theoretically, this effect has been linked to approach/avoidance accounts of how music influences arousal and mood, but no work has tested this experimentally. In the present study, female participants (n = 45) consumed an alcoholic (4% alcohol-by-volume) beverage in one of three contexts: slow tempo music, fast tempo music, or a no-music control. Results revealed that, compared with the control, the beverage was consumed fastest in the two music conditions. Interestingly, whereas arousal and negative mood declined in the control condition, this was not the case for either of the music conditions, suggesting a downregulation of alcohol effects. We additionally found evidence for music to disrupt sensory systems in that, counterintuitively, faster consumption was driven by increases in perceived alcohol strength, which, in turn, predicted lower breath alcohol level (BrAL). These findings suggest a unique interaction of music environment and psychoactive effects of alcohol itself on consumption rate. Because alcohol consumed at a faster rate induces greater intoxication, these findings have implications for applied and theoretical work. PsycINFO Database Record (c) 2013 APA, all rights reserved.

The effects of L-theanine, caffeine and their combination on cognition and mood.

PubMed

Haskell, Crystal F; Kennedy, David O; Milne, Anthea L; Wesnes, Keith A; Scholey, Andrew B

2008-02-01

L-Theanine is an amino acid found naturally in tea. Despite the common consumption of L-theanine, predominantly in combination with caffeine in the form of tea, only one study to date has examined the cognitive effects of this substance alone, and none have examined its effects when combined with caffeine. The present randomised, placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of L-theanine (250 mg), and caffeine (150 mg), in isolation and in combination. Salivary caffeine levels were co-monitored. L-Theanine increased 'headache' ratings and decreased correct serial seven subtractions. Caffeine led to faster digit vigilance reaction time, improved Rapid Visual Information Processing (RVIP) accuracy and attenuated increases in self-reported 'mental fatigue'. In addition to improving RVIP accuracy and 'mental fatigue' ratings, the combination also led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy. 'Headache' and 'tired' ratings were reduced and 'alert' ratings increased. There was also a significant positive caffeine x L-theanine interaction on delayed word recognition reaction time. These results suggest that beverages containing L-theanine and caffeine may have a different pharmacological profile to those containing caffeine alone.

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

Perry, William L; Gunderson, Jake A; Dickson, Peter M

There has been a long history of interest in the decomposition kinetics of HMX and HMX-based formulations due to the widespread use of this explosive in high performance systems. The kinetics allow us to predict, or attempt to predict, the behavior of the explosive when subjected to thermal hazard scenarios that lead to ignition via impact, spark, friction or external heat. The latter, commonly referred to as 'cook off', has been widely studied and contemporary kinetic and transport models accurately predict time and location of ignition for simple geometries. However, there has been relatively little attention given to the problemmore » of localized ignition that results from the first three ignition sources of impact, spark and friction. The use of a zero-order single-rate expression describing the exothermic decomposition of explosives dates to the early work of Frank-Kamanetskii in the late 1930s and continued through the 60's and 70's. This expression provides very general qualitative insight, but cannot provide accurate spatial or timing details of slow cook off ignition. In the 70s, Catalano, et al., noted that single step kinetics would not accurately predict time to ignition in the one-dimensional time to explosion apparatus (ODTX). In the early 80s, Tarver and McGuire published their well-known three step kinetic expression that included an endothermic decomposition step. This scheme significantly improved the accuracy of ignition time prediction for the ODTX. However, the Tarver/McGuire model could not produce the internal temperature profiles observed in the small-scale radial experiments nor could it accurately predict the location of ignition. Those factors are suspected to significantly affect the post-ignition behavior and better models were needed. Brill, et al. noted that the enthalpy change due to the beta-delta crystal phase transition was similar to the assumed endothermic decomposition step in the Tarver/McGuire model. Henson, et al., deduced the kinetics and thermodynamics of the phase transition, providing Dickson, et al. with the information necessary to develop a four-step model that included a two-step nucleation and growth mechanism for the {beta}-{delta} phase transition. Initially, an irreversible scheme was proposed. That model accurately predicted the spatial and temporal cook off behavior of the small-scale radial experiment under slow heating conditions, but did not accurately capture the endothermic phase transition at a faster heating rate. The current version of the four-step model includes reversibility and accurately describes the small-scale radial experiment over a wide range of heating rates. We have observed impact-induced friction ignition of PBX 9501 with grit embedded between the explosive and the lower anvil surface. Observation was done using an infrared camera looking through the sapphire bottom anvil. Time to ignition and temperature-time behavior were recorded. The time to ignition was approximately 500 microseconds and the temperature was approximately 1000 K. The four step reversible kinetic scheme was previously validated for slow cook off scenarios. Our intention was to test the validity for significantly faster hot-spot processes, such as the impact-induced grit friction process studied here. We found the model predicted the ignition time within experimental error. There are caveats to consider when evaluating the agreement. The primary input to the model was friction work over an area computed by a stress analysis. The work rate itself, and the relative velocity of the grit and substrate both have a strong dependence on the initial position of the grit. Any errors in the analysis or the initial grit position would affect the model results. At this time, we do not know the sensitivity to these issues. However, the good agreement does suggest the four step kinetic scheme may have universal applicability for HMX systems.« less

Cellulose nanomaterials as additives for cementitious materials

Treesearch

Tengfei Fu; Robert J. Moon; Pablo Zavatierri; Jeffrey Youngblood; William Jason Weiss

2017-01-01

Cementitious materials cover a very broad area of industries/products (buildings, streets and highways, water and waste management, and many others; see Fig. 20.1). Annual production of cements is on the order of 4 billion metric tons [2]. In general these industries want stronger, cheaper, more durable concrete, with faster setting times, faster rates of strength gain...

Ballistic Range Measurements of Stagnation-Point Heat Transfer in Air and in Carbon Dioxide at Velocities up to 18,000 Feet Per Second

NASA Technical Reports Server (NTRS)

Yee, Layton; Bailey, Harry E.; Woodward, Henry T.

1961-01-01

A new technique for measuring heat-transfer rates on free-flight models in a ballistic range is described in this report. The accuracy of the heat-transfer rates measured in this way is shown to be comparable with the accuracy obtained in shock-tube measurements. The specific results of the present experiments consist of measurements of the stagnation-point heat-transfer rates experienced by a spherical-nosed model during flight through air and through carbon dioxide at velocities up to 18,000 feet per second. For flight through air these measured heat-transfer rates agree well with both the theoretically predicted rates and the rates measured in shock tubes. the heat-transfer rates agree well with the rates measured in a shock tube. Two methods of estimating the stagnation-point heat-transfer rates in carbon dioxide are compared with the experimental measurements. At each velocity the measured stagnation-point heat-transfer rate in carbon dioxide is about the same as the measured heat-transfer rate in air.

THE DYNAMICS OF SPIRAL ARMS IN PURE STELLAR DISKS

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

Fujii, M. S.; Baba, J.; Saitoh, T. R.

2011-04-01

It has been believed that spiral arms in pure stellar disks, especially the ones spontaneously formed, decay in several galactic rotations due to the increase of stellar velocity dispersions. Therefore, some cooling mechanism, for example dissipational effects of the interstellar medium, was assumed to be necessary to keep the spiral arms. Here, we show that stellar disks can maintain spiral features for several tens of rotations without the help of cooling, using a series of high-resolution three-dimensional N-body simulations of pure stellar disks. We found that if the number of particles is sufficiently large, e.g., 3 x 10{sup 6}, multi-armmore » spirals developed in an isolated disk can survive for more than 10 Gyr. We confirmed that there is a self-regulating mechanism that maintains the amplitude of the spiral arms. Spiral arms increase Toomre's Q of the disk, and the heating rate correlates with the squared amplitude of the spirals. Since the amplitude itself is limited by Q, this makes the dynamical heating less effective in the later phase of evolution. A simple analytical argument suggests that the heating is caused by gravitational scattering of stars by spiral arms and that the self-regulating mechanism in pure stellar disks can effectively maintain spiral arms on a cosmological timescale. In the case of a smaller number of particles, e.g., 3 x 10{sup 5}, spiral arms grow faster in the beginning of the simulation (while Q is small) and they cause a rapid increase of Q. As a result, the spiral arms become faint in several Gyr.« less

Precooling leg muscle improves intermittent sprint exercise performance in hot, humid conditions.

PubMed

Castle, Paul C; Macdonald, Adam L; Philp, Andrew; Webborn, Anthony; Watt, Peter W; Maxwell, Neil S

2006-04-01

We used three techniques of precooling to test the hypothesis that heat strain would be alleviated, muscle temperature (Tmu) would be reduced, and as a result there would be delayed decrements in peak power output (PPO) during exercise in hot, humid conditions. Twelve male team-sport players completed four cycling intermittent sprint protocols (CISP). Each CISP consisted of twenty 2-min periods, each including 10 s of passive rest, 5 s of maximal sprint against a resistance of 7.5% body mass, and 105 s of active recovery. The CISP, preceded by 20 min of no cooling (Control), precooling via an ice vest (Vest), cold water immersion (Water), and ice packs covering the upper legs (Packs), was performed in hot, humid conditions (mean +/- SE; 33.7 +/- 0.3 degrees C, 51.6 +/- 2.2% relative humidity) in a randomized order. The rate of heat strain increase during the CISP was faster in Control than Water and Packs (P < 0.01), but it was similar to Vest. Packs and Water blunted the rise of Tmu until minute 16 and for the duration of the CISP (40 min), respectively (P < 0.01). Reductions in PPO occurred from minute 32 onward in Control, and an increase in PPO by approximately 4% due to Packs was observed (main effect; P < 0.05). The method of precooling determined the extent to which heat strain was reduced during intermittent sprint cycling, with leg precooling offering the greater ergogenic effect on PPO than either upper body or whole body cooling.

Fatigue crack growth in SA508-CL2 steel in a high temperature, high purity water environment

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

Gerber, T.L.; Heald, J.D.; Kiss, E.

1974-10-01

Fatigue crack growth tests were conducted with 1 in. plate specimens of SA508-CL 2 steel in room temperature air, 550$sup 0$F air and in a 550$sup 0$F, high purity, water environment. Zero-tension load controlled tests were run at cyclic frequencies as low as 0.037 CPM. Results show that growth rates in the simulated Boiling Water Reactor (BWR) water environment are faster than growth rates observed in 550$sup 0$F air and these rates are faster than the room temperature rate. In the BWR water environment, lowering the cyclic frequency from 0.37 to 0.037 CPM caused only a slight increase in themore » fatigue crack growth rate. All growth rates measured in these tests were below the upper bound design curve presented in Section XI of the ASME Code. (auth)« less

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

Lapsa, Melissa Voss; Khowailed, Gannate

The heating and cooling equipment market in the United States (U.S.) evolved in the last two decades affected by the housing market and external market conditions. The average home size increased by 25% since 1999, contributing to increased average equipment size of heat pumps (HPs) and air conditioners (ACs). The home size increase did not correlate with higher residential energy used. The last decade is recognized for improved home insulation and equipment efficiency, which has made up for the larger home size and still yielded lower residential energy use. The lower energy use coincides with more homes using HPs. HPmore » growth was supported by the price stability and affordability of electricity. The heating and cooling equipment market also seems to be rebounding faster than the housing market after the economic crises. In 2009 only 22% of HPs were sold to new homes, reflecting increased heat pump sales for add-on and replacement applications. HPs are growing in popularity and becoming an established economic technology. The increased usage of HPs will result in reduced residential heating energy use and carbon dioxide emissions.« less

Fluidized-bed pyrolysis of oil shale: oil yield, composition, and kinetics

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

Richardson, J H; Huss, E B; Ott, L L

1982-09-01

A quartz isothermal fluidized-bed reactor has been used to measure kinetics and oil properties relevant to surface processing of oil shale. The rate of oil formation has been described with two sequential first-order rate equations characterized by two rate constants, k/sub 1/ = 2.18 x 10/sup 10/ exp(-41.6 kcal/RT) s/sup -1/ and k/sub 2/ = 4.4 x 10/sup 6/ exp(-29.7 kcal/RT) s/sup -1/. These rate constants together with an expression for the appropriate weighting coefficients describe approximately 97/sup +/% of the total oil produced. A description is given of the results of different attempts to mathematically describe the data inmore » a manner suitable for modeling applications. Preliminary results are also presented for species-selective kinetics of methane, ethene, ethane and hydrogen, where the latter is clearly distinguished as the product of a distinct intermediate. Oil yields from Western oil shale are approximately 100% Fischer assay. Oil composition is as expected based on previous work and the higher heating rates (temperatures) inherent in fluidized-bed pyrolysis. Neither the oil yield, composition nor the kinetics varied with particle size between 0.2 and 2.0 mm within experimental error. The qualitatively expected change in oil composition due to cracking was observed over the temperature range studied (460 to 540/sup 0/C). Eastern shale exhibited significantly faster kinetics and higher oil yields than did Western shale.« less

Comparison of PCE and TCE disappearance in heated volatile organic analysis vials and flame-sealed ampules.

PubMed

Costanza, Jed; Pennell, Kurt D

2008-02-01

The rates of hydrolysis reported for tetrachloroethylene (PCE) and trichloroethylene (TCE) at elevated temperatures range over two orders-of-magnitude, where some of the variability may be due to the presence of a gas phase. Recent studies suggest that volatile organic analysis (VOA) vials provide a low-cost and readily available zero headspace system for measuring aqueous-phase hydrolysis rates. This work involved measuring rates of PCE and TCE disappearance and the corresponding appearance of dechlorination products in water-filled VOA vials and flame-sealed ampules incubated at 21 and 55 degrees C for up to 95.5 days. While PCE and TCE concentrations readily decreased in the VOA vials to yield first-order half lives of 11.2 days for PCE and 21.1 days for TCE at 55 degrees C, concentrations of anticipated dechlorination products, including chloride, remained constant or were not detected. The rate of PCE disappearance was 34 times faster in VOA vials at 55 degrees C compared to values obtained with flame-sealed ampules containing PCE-contaminated water. In addition, the concentration of TCE increased slightly in flame-sealed ampules incubated at 55 degrees C, while a decrease in TCE levels was observed in the VOA vials. The observed losses of PCE and TCE in the VOA vials were attributed to diffusion and sorption in the septa, rather than to dechlorination. These findings demonstrate that VOA vials are not suitable for measuring rates of volatile organic compound hydrolysis at elevated temperatures.

Development and Operation of Arrays of TES x-ray Microcalorimeters Suitable for Constellation-X

NASA Technical Reports Server (NTRS)

Kilbourne, C. A.; Bandler, S. R.; Brown, A. D.; Chervenak, J. A.; Eckart, M. E.; Finkbeiner, F. M.; Iyomoto, N.; Kelley, R. L.; Porter, F. S.; Smith, S. J.;

Cross-correlation spectroscopy study of the transient spark discharge in atmospheric pressure air

NASA Astrophysics Data System (ADS)

Janda, Mário; Hoder, Tomáš; Sarani, Abdollah; Brandenburg, Ronny; Machala, Zdenko

2017-05-01

A streamer-to-spark transition in a self-pulsing transient spark (TS) discharge of positive polarity in air was investigated using cross-correlation spectroscopy. The entire temporal evolution of the TS was recorded for several spectral bands and lines: the second positive system of N2 (337.1 nm), the first negative system of {{{{N}}}2}+ (391.4 nm), and atomic oxygen (777.1 nm). The results enable the visualization of the different phases of discharge development including the primary streamer, the secondary streamer, and the transition to the spark. The spatio-temporal distribution of the reduced electric field strength during the primary streamer phase of the TS was determined and discussed. The transition from the streamer to the spark proceeds very fast within about 10 ns for the TS with a current pulse repetition rate in the range 8-10 kHz. This is attributed to memory effects, leading to a low net electron attachment rate and faster propagation of the secondary streamer. Gas heating, accumulation of species such as oxygen atoms from the previous TS pulses, as well as generation of charged particles by stepwise ionization seem to play important roles contributing to this fast streamer-to-spark transition.

The Intrinsic Variability in the Water Vapor Saturation Ratio Due to Turbulence

NASA Astrophysics Data System (ADS)

Anderson, Jesse Charles

The water vapor concentration plays an important role for many atmospheric processes. The mean concentration is key to understand water vapor's effect on the climate as a greenhouse gas. The fluctuations about the mean are important to understand heat fluxes between Earth's surface and the boundary layer. These fluctuations are linked to turbulence that is present in the boundary layer. Turbulent conditions are simulated in Michigan Tech's multiphase, turbulent reaction chamber, the pi chamber. Measurements for temperature and water vapor concentration were recorded under forced Rayleigh- Benard convection at several turbulent intensities. These were used to calculate the saturation ratio, often referred to as the relative humidity. The fluctuations in the water vapor concentration were found to be the more important than the temperature for the variability of the saturation ratio. The fluctuations in the saturation ratio result in some cloud droplets experiencing a higher supersaturation than other cloud droplets, causing those "lucky" droplets to grow at a faster rate than other droplets. This difference in growth rates could contribute to a broadening of the size distribution of cloud droplets, resulting in the enhancement of collision-coalescence. These fluctuations become more pronounced with more intense turbulence.

Regional warming of hot extremes accelerated by surface energy fluxes consistent with drying soils

NASA Astrophysics Data System (ADS)

Donat, M.; Pitman, A.; Seneviratne, S. I.

2017-12-01

Strong regional differences exist in how hot temperature extremes increase under global warming. Using an ensemble of coupled climate models, we examine the regional warming rates of hot extremes relative to annual average warming rates in the same regions. We identify hotspots of accelerated warming of model-simulated hot extremes in Europe, North America, South America and Southeast China. These hotspots indicate where the warm tail of a distribution of temperatures increases faster than the average and are robust across most CMIP5 models. Exploring the conditions on the specific day the hot extreme occurs demonstrates the hotspots are explained by changes in the surface energy fluxes consistent with drying soils. Furthermore, in these hotspot regions we find a relationship between the temperature - heat flux correlation under current climate conditions and the magnitude of future projected changes in hot extremes, pointing to a potential emergent constraint for simulations of future hot extremes. However, the model-simulated accelerated warming of hot extremes appears inconsistent with observations of the past 60 years, except over Europe. The simulated acceleration of hot extremes may therefore be unreliable, a result that necessitates a re-evaluation of how climate models resolve the relevant terrestrial processes.

Evolution and plasticity: Divergence of song discrimination is faster in birds with innate song than in song learners in Neotropical passerine birds.

PubMed

Freeman, Benjamin G; Montgomery, Graham A; Schluter, Dolph

2017-09-01

Plasticity is often thought to accelerate trait evolution and speciation. For example, plasticity in birdsong may partially explain why clades of song learners are more diverse than related clades with innate song. This "song learning" hypothesis predicts that (1) differences in song traits evolve faster in song learners, and (2) behavioral discrimination against allopatric song (a proxy for premating reproductive isolation) evolves faster in song learners. We tested these predictions by analyzing acoustic traits and conducting playback experiments in allopatric Central American sister pairs of song learning oscines (N = 42) and nonlearning suboscines (N = 27). We found that nonlearners evolved mean acoustic differences slightly faster than did leaners, and that the mean evolutionary rate of song discrimination was 4.3 times faster in nonlearners than in learners. These unexpected results may be a consequence of significantly greater variability in song traits in song learners (by 54-79%) that requires song-learning oscines to evolve greater absolute differences in song before achieving the same level of behavioral song discrimination as nonlearning suboscines. This points to "a downside of learning" for the evolution of species discrimination, and represents an important example of plasticity reducing the rate of evolution and diversification by increasing variability. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

The Role of Vegetation Cover in Interactions between Climate and Erosion

NASA Astrophysics Data System (ADS)

Schildgen, T. F.; Torres-Acosta, V.; Düsing, W.; Garcin, Y.; Strecker, M. R.

2016-12-01

Interactions between tectonics, climate and erosion during mountain building are often considered to include a positive feedback between precipitation and erosion, with the onset of orographic rainfall inducing greater erosion, which in turn may drive faster deformation. Here, we consider two different case studies that explore specifically the relationship between climate and erosion. Within the Kenya Rift of East Africa, spatial variations in 10Be derived erosion rates show no clear dependency on yearly precipitation. Instead, we find that the data fall into two categories. In areas that are sparsely vegetated, erosion rates increase rapidly with slope, whereas in areas that are densely vegetated, erosion rates increase slowly with slope. These data imply that vegetation cover plays a major role in stabilizing hillslopes. From these results, we hypothesize that in a sparsely vegetated region, the onset of greater precipitation will lead to faster erosion, but only until vegetation becomes denser, after which erosion rates will strongly decrease. Initial results from an ongoing study that reconstruct paleo-erosion rates from a sedimentary archive support this hypothesis. Hence, we infer that in this region, vegetation cover acts as a negative feedback in the interactions between climate and erosion. Compared to East Africa, we find a very different relationship between climate and 10Be derived erosion rates in the Toro intermontane basin in NW Argentina. There, the fastest erosion rates occur in the wettest areas with dense vegetation cover, implying a positive feedback between increased precipitation and erosion rates. Also, paleo-erosion rates from the nearby Humahuaca Basin derived from fluvial terraces point to faster erosion during wetter periods in the past. In this region, the stabilizing effects of vegetation cover may be muted. Ultimately, whether increased precipitation leads to faster or slower erosion could hinge on the dominant erosion processes. Along the steep slopes of NW Argentina, landslides are the dominant process, and appear to be minimally affected by vegetation cover. In contrast, the more gentle hillslopes in East Africa appear to be stabilized by a dense vegetation cover.

Prompt Ion Outflows and Artificial Ducts during High-Power HF Heating at HAARP: Effect of Suprathermal Electrons?

NASA Astrophysics Data System (ADS)

Mishin, E. V.; Milikh, G. M.

2014-12-01

In situ observations from the DMSP and Demeter satellites established that high-power HF heating of the ionosphere F-region results in significant ion outflows associated with 10-30% density enhancements in the topside ionosphere magnetically-conjugate to the heated region. As follows from the SAMI2 two-fluid model calculations, their formation time should exceed 5-7 minutes. However, specially designed DMSP-HAARP experiments have shown that artificial ducts and ion outflows appear on the topside within 2 minutes. We describe the results of these observations and present a semi-quantitative explanation of the fast timescale due to suprathermal electrons accelerated by HF-induced plasma turbulence. There are two possible effects of suprathermal electrons: (1) the increase of the ambipolar electric field over the usual thermal ambipolar diffusion and (2) excitation of heat flux-driven plasma instability resulting in an anomalous electron-ion momentum exchange. Both effects result in faster upward ion flows.

Rate of nicotine metabolism and smoking cessation outcomes in a community-based sample of treatment-seeking smokers.

PubMed

Kaufmann, Amanda; Hitsman, Brian; Goelz, Patricia M; Veluz-Wilkins, Anna; Blazekovic, Sonja; Powers, Lindsay; Leone, Frank T; Gariti, Peter; Tyndale, Rachel F; Schnoll, Robert A

2015-12-01

In samples from controlled randomized clinical trials, a smoker's rate of nicotine metabolism, measured by the 3-hydroxycotinine to cotinine ratio (NMR), predicts response to transdermal nicotine. Replication of this relationship in community-based samples of treatment-seeking smokers may help guide the implementation of the NMR for personalized treatment for nicotine dependence. Data from a community-based sample of treatment seeking smokers (N=499) who received 8weeks of transdermal nicotine and 4 behavioral counseling sessions were used to evaluate associations between the NMR and smoking cessation. Secondary outcomes included withdrawal and craving, depression and anxiety, side effects, and treatment adherence. The NMR was a significant predictor of abstinence (OR=.56, 95% CI: 0.33-0.95, p=.03), with faster metabolizers showing lower quit rates than slower metabolizers (24% vs. 33%). Faster nicotine metabolizers exhibited significantly higher levels of anxiety symptoms over time during treatment, vs. slower metabolizers (NMR x Time interaction: F[3,357]=3.29, p=.02). NMR was not associated with changes in withdrawal, craving, depression, side effects, and treatment adherence (p's>.05). In a community-based sample of treatment-seeking smokers, faster nicotine metabolizers were significantly less likely to quit smoking and showed higher rates of anxiety symptoms during a smoking cessation treatment program, vs. slower nicotine metabolizers. These results provide further evidence that transdermal nicotine is less effective for faster nicotine metabolizers and suggest the need to address cessation-induced anxiety symptoms among these smokers to increase the chances for successful smoking cessation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Connecting localized DNA strand displacement reactions

NASA Astrophysics Data System (ADS)

Mullor Ruiz, Ismael; Arbona, Jean-Michel; Lad, Amitkumar; Mendoza, Oscar; Aimé, Jean-Pierre; Elezgaray, Juan

2015-07-01

Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions.Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR02434J

Shock heating in numerical simulations of kink-unstable coronal loops

PubMed Central

Bareford, M. R.; Hood, A. W.

2015-01-01

An analysis of the importance of shock heating within coronal magnetic fields has hitherto been a neglected area of study. We present new results obtained from nonlinear magnetohydrodynamic simulations of straight coronal loops. This work shows how the energy released from the magnetic field, following an ideal instability, can be converted into thermal energy, thereby heating the solar corona. Fast dissipation of magnetic energy is necessary for coronal heating and this requirement is compatible with the time scales associated with ideal instabilities. Therefore, we choose an initial loop configuration that is susceptible to the fast-growing kink, an instability that is likely to be created by convectively driven vortices, occurring where the loop field intersects the photosphere (i.e. the loop footpoints). The large-scale deformation of the field caused by the kinking creates the conditions for the formation of strong current sheets and magnetic reconnection, which have previously been considered as sites of heating, under the assumption of an enhanced resistivity. However, our simulations indicate that slow mode shocks are the primary heating mechanism, since, as well as creating current sheets, magnetic reconnection also generates plasma flows that are faster than the slow magnetoacoustic wave speed. PMID:25897092

Brain heating induced by near-infrared lasers during multiphoton microscopy

PubMed Central

Ranganathan, Gayathri

2016-01-01

Two-photon imaging and optogenetic stimulation rely on high illumination powers, particularly for state-of-the-art applications that target deeper structures, achieve faster measurements, or probe larger brain areas. However, little information is available on heating and resulting damage induced by high-power illumination in the brain. In the current study we used thermocouple probes and quantum dot nanothermometers to measure temperature changes induced by two-photon microscopy in the neocortex of awake and anaesthetized mice. We characterized heating as a function of wavelength, exposure time, and distance from the center of illumination. Although total power is highest near the surface of the brain, heating was most severe hundreds of micrometers below the focal plane, due to heat dissipation through the cranial window. Continuous illumination of a 1-mm2 area produced a peak temperature increase of ∼1.8°C/100 mW. Continuous illumination with powers above 250 mW induced lasting damage, detected with immunohistochemistry against Iba1, glial fibrillary acidic protein, heat shock proteins, and activated caspase-3. Higher powers were usable in experiments with limited duty ratios, suggesting an approach to mitigate damage in high-power microscopy experiments. PMID:27281749

Influence of heat and vibration on the movement of the northern fowl mite (Acari: Macronyssidae).

PubMed

Owen, Jeb P; Mullens, Bradley A

2004-09-01

Heat and vibration are common host-generated cues that ectoparasites use to orient to hosts. Three experiments evaluated effects of heat and vibration on the movement of northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago). Individual arrested mites in an isolation chamber always initiated movement (walking) after substrate vibration (7.8-min walking duration), but only initiated movement 50% of the time (2.8-min walking duration) upon exposure to a 3 degrees C heat fluctuation. Heat fluctuation in combination with vibration extended the period of activity by approximately 50% (11.6-min walking duration) compared with activity initiated by vibration alone. Mites with longer time off-host moved for shorter durations. In a choice test, individual mites consistently moved closer to a 35 degrees C heat source 1 or 6 mm away, but not to a heat source 11 mm away. In a circular arena, mites were able to orient accurately to a 35 degrees C heat source and reached the arena edge almost 4 times faster (11.2 s) than mites without a heat source (41.2 s). These results suggest that northern fowl mite is capable of directed thermo-orientation, as well as modulation of activity depending on the type of sensory information perceived. The adaptive significance of this orientation for a "permanent" ectoparasite is discussed.

Viability and antigenicity of anisakis simplex after conventional and microwave heating at fixed temperatures.

PubMed

Vidaček, Sanja; De Las Heras, Cristina; Solas, Maria Teresa; García, Maria Luisa; Mendizábal, Angel; Tejada, Margarita

2011-12-01

Inactivation of parasites in food by microwave treatment may vary due to differences in the characteristics of microwave ovens and food properties. Microwave treatment in standard domestic ovens results in hot and cold spots, and the microwaves do not penetrate all areas of the samples depending on the thickness, which makes it difficult to compare microwave with conventional heat treatments. The viability of Anisakis simplex (isolated larvae and infected fish muscle) heated in a microwave oven with precise temperature control was compared with that of larvae heated in a water bath to investigate any additional effect of the microwaves. At a given temperature, less time was required to kill the larvae by microwaves than by heated water. Microwave treatment killed A. simplex larvae faster than did conventional cooking when the microwaves fully penetrated the samples and resulted in fewer changes in the fish muscle. However, the heat-stable allergen Ani s 4 was detected by immunohistochemistry in the fish muscle after both heat treatments, even at 70°C, suggesting that Ani s 4 allergens were released from the larvae into the surrounding tissue and that the tissues retained their allergenicity even after the larvae were killed by both heat treatments. Thus, microwave cooking will not render fish safe for individuals already sensitized to A. simplex heat-resistant allergens.

Coarse Alignment Technology on Moving base for SINS Based on the Improved Quaternion Filter Algorithm.

PubMed

Zhang, Tao; Zhu, Yongyun; Zhou, Feng; Yan, Yaxiong; Tong, Jinwu

2017-06-17

Initial alignment of the strapdown inertial navigation system (SINS) is intended to determine the initial attitude matrix in a short time with certain accuracy. The alignment accuracy of the quaternion filter algorithm is remarkable, but the convergence rate is slow. To solve this problem, this paper proposes an improved quaternion filter algorithm for faster initial alignment based on the error model of the quaternion filter algorithm. The improved quaternion filter algorithm constructs the K matrix based on the principle of optimal quaternion algorithm, and rebuilds the measurement model by containing acceleration and velocity errors to make the convergence rate faster. A doppler velocity log (DVL) provides the reference velocity for the improved quaternion filter alignment algorithm. In order to demonstrate the performance of the improved quaternion filter algorithm in the field, a turntable experiment and a vehicle test are carried out. The results of the experiments show that the convergence rate of the proposed improved quaternion filter is faster than that of the tradition quaternion filter algorithm. In addition, the improved quaternion filter algorithm also demonstrates advantages in terms of correctness, effectiveness, and practicability.

Faster proton transfer dynamics of water on SnO2 compared to TiO2.

PubMed

Kumar, Nitin; Kent, Paul R C; Bandura, Andrei V; Kubicki, James D; Wesolowski, David J; Cole, David R; Sofo, Jorge O

2011-01-28

Proton jump processes in the hydration layer on the iso-structural TiO(2) rutile (110) and SnO(2) cassiterite (110) surfaces were studied with density functional theory molecular dynamics. We find that the proton jump rate is more than three times faster on cassiterite compared with rutile. A local analysis based on the correlation between the stretching band of the O-H vibrations and the strength of H-bonds indicates that the faster proton jump activity on cassiterite is produced by a stronger H-bond formation between the surface and the hydration layer above the surface. The origin of the increased H-bond strength on cassiterite is a combined effect of stronger covalent bonding and stronger electrostatic interactions due to differences of its electronic structure. The bridging oxygens form the strongest H-bonds between the surface and the hydration layer. This higher proton jump rate is likely to affect reactivity and catalytic activity on the surface. A better understanding of its origins will enable methods to control these rates.

The Kinetics of Myosin Light Chain Kinase Activation of Smooth Muscle Myosin in an In Vitro Model System

PubMed Central

Hong, Feng; Facemyer, Kevin C.; Carter, Michael S.; Jackson, Del R.; Haldeman, Brian D.; Ruana, Nick; Sutherland, Cindy; Walsh, Michael P.; Cremo, Christine R.; Baker, Josh E.

2013-01-01

During activation of smooth muscle contraction, one myosin light chain kinase (MLCK) molecule rapidly phosphorylates many smooth muscle myosin (SMM) molecules, suggesting that muscle activation rates are influenced by the kinetics of MLCK-SMM interactions. To determine the rate-limiting step underlying activation of SMM by MLCK, we measured the kinetics of calcium-calmodulin (Ca2+-CaM)-MLCK-mediated SMM phosphorylation and the corresponding initiation of SMM-based F-actin motility in an in vitro system with SMM attached to a coverslip surface. Fitting the time course of SMM phosphorylation to a kinetic model gave an initial phosphorylation rate, kpo, of ~1.17 heads s−1·MLCK−1. Also we measured the dwell time of single QD-labeled MLCK molecules interacting with surface-attached SMM and phosphorylated SMM using total internal reflection fluorescence microscopy. From these data, the dissociation rate constant from phosphorylated SMM was 0.80 s−1, which was similar to kpo mentioned above and with rates measured in solution. This dissociation rate was essentially independent of the phosphorylation state of SMM. From calculations using our measured dissociation rates and Kds, and estimates of [SMM] and [MLCK] in muscle, we predict that the dissociation of MLCK from phosphorylated SMM is rate-limiting and that the rate of the phosphorylation step is faster than this dissociation rate. Also, association to SMM (11-46 s−1) would be much faster than to pSMM (<0.1-0.2 s−1). This suggests that the probability of MLCK interacting with unphosphorylated versus pSMM is 55-460 times greater. This would avoid sequestering MLCK to unproductive interactions with previously phosphorylated SMM, potentially leading to faster rates of phosphorylation in muscle. PMID:24144337

New methods and astrophysical applications of adaptive mesh fluid simulations

NASA Astrophysics Data System (ADS)

Wang, Peng

The formation of stars, galaxies and supermassive black holes are among the most interesting unsolved problems in astrophysics. Those problems are highly nonlinear and involve enormous dynamical ranges. Thus numerical simulations with spatial adaptivity are crucial in understanding those processes. In this thesis, we discuss the development and application of adaptive mesh refinement (AMR) multi-physics fluid codes to simulate those nonlinear structure formation problems. To simulate the formation of star clusters, we have developed an AMR magnetohydrodynamics (MHD) code, coupled with radiative cooling. We have also developed novel algorithms for sink particle creation, accretion, merging and outflows, all of which are coupled with the fluid algorithms using operator splitting. With this code, we have been able to perform the first AMR-MHD simulation of star cluster formation for several dynamical times, including sink particle and protostellar outflow feedbacks. The results demonstrated that protostellar outflows can drive supersonic turbulence in dense clumps and explain the observed slow and inefficient star formation. We also suggest that global collapse rate is the most important factor in controlling massive star accretion rate. In the topics of galaxy formation, we discuss the results of three projects. In the first project, using cosmological AMR hydrodynamics simulations, we found that isolated massive star still forms in cosmic string wakes even though the mega-parsec scale structure has been perturbed significantly by the cosmic strings. In the second project, we calculated the dynamical heating rate in galaxy formation. We found that by balancing our heating rate with the atomic cooling rate, it gives a critical halo mass which agrees with the result of numerical simulations. This demonstrates that the effect of dynamical heating should be put into semi-analytical works in the future. In the third project, using our AMR-MHD code coupled with radiative cooling module, we performed the first MHD simulations of disk galaxy formation. We find that the initial magnetic fields are quickly amplified to Milky-Way strength in a self-regulated way with amplification rate roughly one e-folding per orbit. This suggests that Milky Way strength magnetic field might be common in high redshift disk galaxies. We have also developed AMR relativistic hydrodynamics code to simulate black hole relativistic jets. We discuss the coupling of the AMR framework with various relativistic solvers and conducted extensive algorithmic comparisons. Via various test problems, we emphasize the importance of resolution studies in relativistic flow simulations because extremely high resolution is required especially when shear flows are present in the problem. Then we present the results of 3D simulations of supermassive black hole jets propagation and gamma ray burst jet breakout. Resolution studies of the two 3D jets simulations further highlight the need of high resolutions to calculate accurately relativistic flow problems. Finally, to push forward the kind of simulations described above, we need faster codes with more physics included. We describe an implementation of compressible inviscid fluid solvers with AMR on Graphics Processing Units (GPU) using NVIDIA's CUDA. We show that the class of high resolution shock capturing schemes can be mapped naturally on this architecture. For both uniform and adaptive simulations, we achieve an overall speedup of approximately 10 times faster execution on one Quadro FX 5600 GPU as compared to a single 3 GHz Intel core on the host computer. Our framework can readily be applied to more general systems of conservation laws and extended to higher order shock capturing schemes. This is shown directly by an implementation of a magneto-hydrodynamic solver and comparing its performance to the pure hydrodynamic case.

Rhinoscintigraphic analysis of nasal mucociliary function in patients with Bell's palsy.

PubMed

Boynuegri, S; Ozer, S; Peksoy, I; Acikalin, A; Tuna, E Ü; Dursun, E; Eryilmaz, A

2016-01-01

Mucociliary transport (MCT) is an important defense mechanism of the respiratory tract. One of the major factors determining MCT is the ciliary activity of the respiratory epithelium. Rhinoscintigraphy is the most commonly used method for the analysis of mucociliary activity. The aim of this study was to investigate the effect of facial paralysis on the nasal mucociliary clearance. This study included 38 Bell's palsy patients as the study group and 10 subjects without any history of paranasal sinus disease or facial paralysis as the control group. A drop of technetium 99m-labeled macroaggregated albumin (Tc-99m MAA) was placed posterior to the head of the inferior turbinate and followed with a gamma camera. MCT rate was measured as the velocity of Tc-99m MAA drop. The mean MCT rate was 4.27 ± 0.76 millimeters per minute (mm/min) on 20 sides of 10 healthy controls, 4.11 ± 2.91 mm/min on the affected sides of the patients with Bell's palsy, and 6.03 ± 3.13 mm/min on the nonparalyzed sides of the patients. MCT rate was statistically significantly faster in the nonparalyzed side when compared to the paralyzed side in Bell's palsy patients (P = 0.001). MCT rates were not significantly different in the control group and paralyzed sides of the Bell's palsy patients (P = 0.810). The MCT rate was statistically significantly faster in the nonparalyzed sides of Bell's palsy patients when compared to the controls (P = 0.017). This study showed a faster MCT rate on the nonparalyzed side in Bell's palsy patients when compared to the paralyzed side and the control subjects. A compensatory mechanism could be the underlying reason for faster MCT on the nonparalyzed side. Further studies on larger patient groups are needed to investigate the effect of facial paralysis on the MCT and changes of facial nerve function on the opposite, nonparalyzed side of the face.

Transient Mass and Thermal Transport during Methane Adsorption into the Metal-Organic Framework HKUST-1.

PubMed

Babaei, Hasan; McGaughey, Alan J H; Wilmer, Christopher E

2018-01-24

Methane adsorption into the metal-organic framework (MOF) HKUST-1 and the resulting heat generation and dissipation are investigated using molecular dynamics simulations. Transient simulations reveal that thermal transport in the MOF occurs two orders of magnitude faster than gas diffusion. A large thermal resistance at the MOF-gas interface (equivalent to 127 nm of bulk HKUST-1), however, prevents fast release of the generated heat. The mass transport resistance at the MOF-gas interface is equivalent to 1 nm of bulk HKUST-1 and does not present a bottleneck in the adsorption process. These results provide important insights into the application of MOFs for gas storage applications.

Energetics and biomechanics of locomotion by red kangaroos (Macropus rufus).

PubMed

Kram, R; Dawson, T J

1998-05-01

As red kangaroos hop faster over level ground, their rate of oxygen consumption (indicating metabolic energy consumption) remains nearly the same. This phenomenon has been attributed to exceptional elastic energy storage and recovery via long compliant tendons in the legs. Alternatively, red kangaroos may have exceptionally efficient muscles. To estimate efficiency, we measured the metabolic cost of uphill hopping, where muscle fibers must perform mechanical work against gravity. We found that uphill hopping was much more expensive than level hopping. The maximal rate of oxygen consumption measured (3 ml O2 kg-1 s-1) exceeds all but a few vertebrate species. However, efficiency values were normal, approximately 30%. At faster level hopping speeds the effective mechanical advantage of the extensor muscles of the ankle joint remained the same. Thus, kangaroos generate the same muscular force at all speeds but do so more rapidly at faster hopping speeds. This contradicts a recent hypothesis for what sets the cost of locomotion. The cost of transport (J kg-1 m-1) decreases at faster hopping speeds, yet red kangaroos prefer to use relatively slow speeds that avoid high levels of tendon stress.

Drying process optimization for an API solvate using heat transfer model of an agitated filter dryer.

PubMed

Nere, Nandkishor K; Allen, Kimberley C; Marek, James C; Bordawekar, Shailendra V

2012-10-01

Drying an early stage active pharmaceutical ingredient candidate required excessively long cycle times in a pilot plant agitated filter dryer. The key to faster drying is to ensure sufficient heat transfer and minimize mass transfer limitations. Designing the right mixing protocol is of utmost importance to achieve efficient heat transfer. To this order, a composite model was developed for the removal of bound solvent that incorporates models for heat transfer and desolvation kinetics. The proposed heat transfer model differs from previously reported models in two respects: it accounts for the effects of a gas gap between the vessel wall and solids on the overall heat transfer coefficient, and headspace pressure on the mean free path length of the inert gas and thereby on the heat transfer between the vessel wall and the first layer of solids. A computational methodology was developed incorporating the effects of mixing and headspace pressure to simulate the drying profile using a modified model framework within the Dynochem software. A dryer operational protocol was designed based on the desolvation kinetics, thermal stability studies of wet and dry cake, and the understanding gained through model simulations, resulting in a multifold reduction in drying time. Copyright © 2012 Wiley-Liss, Inc.

Flour sodium dodecyl sulfate (SDS)-extractable protein level as a cookie flour quality indicator.

PubMed

Pareyt, Bram; Bruneel, Charlotte; Brijs, Kristof; Goesaert, Hans; Delcour, Jan A

2010-01-13

Flour characteristics of laboratory-milled flour fractions of two wheat cultivars were related to their cookie-baking performance. Cultivar (cv.) Albatros wheat milling yielded fractions with lower damaged starch (DS) and arabinoxylan levels and higher sodium dodecyl sulfate-extractable protein (SDSEP) levels than did cv. Meunier wheat milling. During baking, cv. Albatros flour doughs spread faster and set later than their cv. Meunier counterparts and, hence, resulted in larger cookie diameters. DS levels negatively affected spread rate during both cv. Albatros (R2=0.68) and cv. Meunier (R2=0.51) cookie baking. SDSEP levels also influenced cookie quality. The use of flour heat-treated to reduce its SDSEP levels to different degrees led to reduction of the set time (R2=0.90). It was deduced that larger gluten polymer sizes limit dough spread time during baking and that, apart from DS level, the SDSEP level is an indicator for cookie flour quality.

Dynamic weakening is limited by granular dynamics

NASA Astrophysics Data System (ADS)

Kuwano, O.; Hatano, T.

2011-12-01

Earthquakes are the result of the frictional instability of faults containing fine rock powders called gouge derived from attrition in past fault motions. Understanding the frictional instability of granular matter in terms of constitutive laws is thus important. Because of the importance of granular matter for industries and engineering, the friction of granular matter has been studied in the field of solid earth science and other fields, such as statistical physics. In solid earth science, the rate- and state-dependent friction law was established by laboratory experiments at a very low sliding velocity (μm/s to mm/s). Recent experiments conducted at sub-seismic to seismic sliding velocities (mm/s to m/s), however, show that frictional properties are much richer than those predicted by the rate- and state-dependent friction law. One of the most important findings in such experiments is the remarkable weakening due to mechano-chemical effects by frictional heating [Tullis, 2007]. In statistical physics, another empirical law holds for much faster deformation than the former, showing positive shear-rate dependence. Until Recently, friction of granular matter has been investigated independently in the fields of solid earth science and statistical physics, and thus the relation between these distinct constitutive laws is not clear. Recently, some experimental studies have been reported to connect the achievements in these two fields. For example, a laboratory experiment on dry glass beads under very low normal stress (0.02 to 0.05 MPa) in which the frictional heat is negligible reveals the transition from velocity-weakening friction at low sliding velocities to velocity-strengthening friction at high sliding velocities [Kuwano et al., 2011]. Importantly, the velocity-strengthening nature at high sliding velocities is quantitatively the same as those observed in simulations. The inelastic deformation of the grains therefore plays a vital role at high sliding velocities. In this study, we report a friction experiment under higher pressure (0.1 to 0.9 MPa), in which the frictional heat is significant. To clarify the effect of frictional heat in high-speed friction systematically, we investigated both the pressure and the velocity dependence of the friction coefficient over a wide range of sliding velocities ranging from aseismic to seismic slip velocities. We observed considerable weakening, described well by a flash-heating theory, above the sliding velocity of 1 cm/s regardless of pressure. At higher velocities, the velocity strengthening behavior replaced the velocity weakening behavior. This strengthening at higher velocities agrees with data from numerical simulations on sheared granular matter and is therefore described in terms of energy dissipation due to the inelastic deformation of grains. We propose a unified steady-state friction law that well describes the velocity and pressure dependence of the steady-state friction coefficient.

An algorithm for the kinetics of tire pyrolysis under different heating rates.

PubMed

Quek, Augustine; Balasubramanian, Rajashekhar

2009-07-15

Tires exhibit different kinetic behaviors when pyrolyzed under different heating rates. A new algorithm has been developed to investigate pyrolysis behavior of scrap tires. The algorithm includes heat and mass transfer equations to account for the different extents of thermal lag as the tire is heated at different heating rates. The algorithm uses an iterative approach to fit model equations to experimental data to obtain quantitative values of kinetic parameters. These parameters describe the pyrolysis process well, with good agreement (r(2)>0.96) between the model and experimental data when the model is applied to three different brands of automobile tires heated under five different heating rates in a pure nitrogen atmosphere. The model agrees with other researchers' results that frequencies factors increased and time constants decreased with increasing heating rates. The model also shows the change in the behavior of individual tire components when the heating rates are increased above 30 K min(-1). This result indicates that heating rates, rather than temperature, can significantly affect pyrolysis reactions. This algorithm is simple in structure and yet accurate in describing tire pyrolysis under a wide range of heating rates (10-50 K min(-1)). It improves our understanding of the tire pyrolysis process by showing the relationship between the heating rate and the many components in a tire that depolymerize as parallel reactions.

The effect of speaking rate on supersegmentals: An acoustic and perceptual analysis

NASA Astrophysics Data System (ADS)

Chiou, Hsin-Huei; Watson, Peter

2005-09-01

Rate manipulation has been used to study change in prosodic contrasts such as emphatic stress. Timing contrasts in stressed words are reduced or eliminated when speaking rate is increased. However, reports of intonation and rate change are mixed. Some studies have reported an increase of F0 movement [M. Steppling and A. Montgomery, J. Phonetics 64, 451-461 (2002)], and other reports have found that F0 movement is decreased at faster speaking rates [C. Fougeron and S. Jun, Percept. Psychophys. 26, 45-69 (1998)]. This study examined the effect of speaking rate on F0 and duration in sentences produced with emphatic stress in different sentential position and in declarative and interrogative forms. Essentially, durational contrasts were reduced at faster speaking rates and were more pronounced at slower speaking rates. Intonation, on the other hand, was more pronounced for the fast rate and somewhat reduced for the slow rate. A perceptual component will also be reported that examines a listener's ability to recognize stressed words and mode of sentence production (declarative and interrogative) at different speaking rates.

Physics of the Geospace Response to Powerful HF Radio Waves

DTIC Science & Technology

2012-10-31

studies of the response of the Earth’s space plasma to high-power HF radio waves from the High-frequency Active Auroral Research Program ( HAARP ...of HF heating and explored to simulate artificial ducts. DMSP- HAARP experiments revealed that HF-created ion outflows and artificial density ducts...in the topside ionosphere appeared faster than predicted by the models, pointing to kinetic (suprathermal) effects. CHAMP/GRACE- HAARP experiments

Motor Starters

NASA Technical Reports Server (NTRS)

1986-01-01

The power factor controller (PFC) was invented by a NASA engineer. It matches voltage with a motor's actual need by sensing shifts in the relationship between voltage and current flow. With the device, power can be trimmed as much as 65%. Intellinet adopted this technology and designed "soft start" and "load-responsive" control modes to start engines gradually and recycle voltage without reducing motor speed. Other features are lower motor heat and faster fault identification.

Bubble behavior in molten glass in a temperature gradient. [in reduced gravity rocket experiment

NASA Technical Reports Server (NTRS)

Meyyappan, M.; Subramanian, R. S.; Wilcox, W. R.; Smith, H.

1982-01-01

Gas bubble motion in a temperature gradient was observed in a sodium borate melt in a reduced gravity rocket experiment under the NASA SPAR program. Large bubbles tended to move faster than smaller ones, as predicted by theory. When the bubbles contacted a heated platinum strip, motion virtually ceased because the melt only imperfectly wets platinum. In some cases bubble diameter increased noticeably with time.

Association between rates of binocular visual field loss and vision-related quality of life in patients with glaucoma.

PubMed

Lisboa, Renato; Chun, Yeoun Sook; Zangwill, Linda M; Weinreb, Robert N; Rosen, Peter N; Liebmann, Jeffrey M; Girkin, Christopher A; Medeiros, Felipe A

2013-04-01

It is reasonable to hypothesize that for 2 patients with similar degrees of integrated binocular visual field (BVF) loss, the patient with a history of faster disease progression will report worse vision-related quality of life (VRQOL) than the patient with slowly progressing damage. However, to our knowledge, this hypothesis has not been investigated in the literature. To evaluate the association between binocular rates of visual field change and VRQOL in patients with glaucoma. DESIGN Observational cohort study. Patients were recruited from the Diagnostic Innovations in Glaucoma Study and the African Descent and Glaucoma Evaluation Study. The study included 796 eyes of 398 patients with diagnosed or suspected glaucoma followed up from October 1, 1998, until January 31, 2012, for a mean (SD) of 7.3 (2.0) years. The VRQOL was evaluated using the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) at the last follow-up visit. The NEI VFQ-25 was completed for all patients during the period extending from December 1, 2009, through January 31, 2012. Integrated BVFs were calculated from the monocular fields of each patient. Linear regression of mean deviation values was used to evaluate rates of BVF change during the follow-up period. Logistic regression models were used to investigate the association between abnormal VRQOL and rates of BVF change, while adjusting for potentially confounding socioeconomic and demographic variables. Thirty-two patients (8.0%) had abnormal VRQOL as determined by the results of the NEI VFQ-25. Patients with abnormal VRQOL had significantly faster rates of BVF change than those with normal VRQOL (-0.18 vs -0.06 dB/y; P < .001). Rates of BVF change were significantly associated with abnormality in VRQOL (odds ratio = 1.31 per 0.1 dB/y faster; P = .04), after adjustment for confounding variables. Patients with faster rates of BVF change were at higher risk of reporting abnormal VRQOL. Assessment of rates of BVF change may provide useful information in determining risk of functional impairment in glaucoma.

Mechanisms of viral mutation.

PubMed

Sanjuán, Rafael; Domingo-Calap, Pilar

2016-12-01

The remarkable capacity of some viruses to adapt to new hosts and environments is highly dependent on their ability to generate de novo diversity in a short period of time. Rates of spontaneous mutation vary amply among viruses. RNA viruses mutate faster than DNA viruses, single-stranded viruses mutate faster than double-strand virus, and genome size appears to correlate negatively with mutation rate. Viral mutation rates are modulated at different levels, including polymerase fidelity, sequence context, template secondary structure, cellular microenvironment, replication mechanisms, proofreading, and access to post-replicative repair. Additionally, massive numbers of mutations can be introduced by some virus-encoded diversity-generating elements, as well as by host-encoded cytidine/adenine deaminases. Our current knowledge of viral mutation rates indicates that viral genetic diversity is determined by multiple virus- and host-dependent processes, and that viral mutation rates can evolve in response to specific selective pressures.

Frictional strength and heat flow of southern San Andreas Fault

NASA Astrophysics Data System (ADS)

Zhu, P. P.

2016-01-01

Frictional strength and heat flow of faults are two related subjects in geophysics and seismology. To date, the investigation on regional frictional strength and heat flow still stays at the stage of qualitative estimation. This paper is concentrated on the regional frictional strength and heat flow of the southern San Andreas Fault (SAF). Based on the in situ borehole measured stress data, using the method of 3D dynamic faulting analysis, we quantitatively determine the regional normal stress, shear stress, and friction coefficient at various seismogenic depths. These new data indicate that the southern SAF is a weak fault within the depth of 15 km. As depth increases, all the regional normal and shear stresses and friction coefficient increase. The former two increase faster than the latter. Regional shear stress increment per kilometer equals 5.75 ± 0.05 MPa/km for depth ≤15 km; regional normal stress increment per kilometer is equal to 25.3 ± 0.1 MPa/km for depth ≤15 km. As depth increases, regional friction coefficient increment per kilometer decreases rapidly from 0.08 to 0.01/km at depths less than ~3 km. As depth increases from ~3 to ~5 km, it is 0.01/km and then from ~5 to 15 km, and it is 0.002/km. Previously, frictional strength could be qualitatively determined by heat flow measurements. It is difficult to obtain the quantitative heat flow data for the SAF because the measured heat flow data exhibit large scatter. However, our quantitative results of frictional strength can be employed to investigate the heat flow in the southern SAF. We use a physical quantity P f to describe heat flow. It represents the dissipative friction heat power per unit area generated by the relative motion of two tectonic plates accommodated by off-fault deformation. P f is called "fault friction heat." On the basis of our determined frictional strength data, utilizing the method of 3D dynamic faulting analysis, we quantitatively determine the regional long-term fault friction heat at various seismogenic depths in the southern SAF. The new data show that as depth increases, regional friction stress increases within the depth of 15 km; its increment per kilometer equals 5.75 ± 0.05 MPa/km. As depth increases, regional long-term fault friction heat increases; its increment per kilometer is equal to 3.68 ± 0.03 mW/m2/km. The values of regional long-term fault friction heat provided by this study are always lower than those from heat flow measurements. The difference between them and the scatter existing in the measured heat flow data are mainly caused by the following processes: (i) heat convection, (ii) heat advection, (iii) stress accumulation, (iv) seismic bursts between short-term lull periods in a long-term period, and (v) influence of seismicity in short-term periods upon long-term slip rate and heat flow. Fault friction heat is a fundamental parameter in research on heat flow.

New thermodynamical force in plasma phase space that controls turbulence and turbulent transport.

PubMed

Itoh, Sanae-I; Itoh, Kimitaka

2012-01-01

Physics of turbulence and turbulent transport has been developed on the central dogma that spatial gradients constitute the controlling parameters, such as Reynolds number and Rayleigh number. Recent experiments with the nonequilibrium plasmas in magnetic confinement devices, however, have shown that the turbulence and transport change much faster than global parameters, after an abrupt change of heating power. Here we propose a theory of turbulence in inhomogeneous magnetized plasmas, showing that the heating power directly influences the turbulence. New mechanism, that an external source couples with plasma fluctuations in phase space so as to affect turbulence, is investigated. A new thermodynamical force in phase-space, i.e., the derivative of heating power by plasma pressure, plays the role of new control parameter, in addition to spatial gradients. Following the change of turbulence, turbulent transport is modified accordingly. The condition under which this new effect can be observed is also evaluated.

Thermal systems design and analysis for a 10 K Sorption Cryocooler flight experiment

NASA Technical Reports Server (NTRS)

Bhandari, Pradeep; Bard, Steven

1993-01-01

The design, analysis and predicted performance of the Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE) is described from a thermal perspective. BETSCE is a shuttle side-wall mounted cryogenic technology demonstration experiment planned for launch in November 1994. BETSCE uses a significant amount of power (about 500 W peak) and the resultant heat must be rejected passively with radiators, as BETSCE has no access to the active cooling capability of the shuttle. It was a major challenge to design and configure the individual hardware assemblies, with their relatively large radiators, to enable them to reject their heat while satisfying numerous severe shuttle-imposed constraints. This paper is a useful case study of a small shuttle payload that needs to reject relatively high heat loads passively in a highly constrained thermal environment. The design approach described is consistent with today's era of 'faster, better, cheaper' small-scale space missions.

Superradiant Quantum Heat Engine.

PubMed

Hardal, Ali Ü C; Müstecaplıoğlu, Özgür E

2015-08-11

Quantum physics revolutionized classical disciplines of mechanics, statistical physics, and electrodynamics. One branch of scientific knowledge however seems untouched: thermodynamics. Major motivation behind thermodynamics is to develop efficient heat engines. Technology has a trend to miniaturize engines, reaching to quantum regimes. Development of quantum heat engines (QHEs) requires emerging field of quantum thermodynamics. Studies of QHEs debate whether quantum coherence can be used as a resource. We explore an alternative where it can function as an effective catalyst. We propose a QHE which consists of a photon gas inside an optical cavity as the working fluid and quantum coherent atomic clusters as the fuel. Utilizing the superradiance, where a cluster can radiate quadratically faster than a single atom, we show that the work output becomes proportional to the square of the number of the atoms. In addition to practical value of cranking up QHE, our result is a fundamental difference of a quantum fuel from its classical counterpart.

New Thermodynamical Force in Plasma Phase Space that Controls Turbulence and Turbulent Transport

PubMed Central

Itoh, Sanae-I.; Itoh, Kimitaka

2012-01-01

Physics of turbulence and turbulent transport has been developed on the central dogma that spatial gradients constitute the controlling parameters, such as Reynolds number and Rayleigh number. Recent experiments with the nonequilibrium plasmas in magnetic confinement devices, however, have shown that the turbulence and transport change much faster than global parameters, after an abrupt change of heating power. Here we propose a theory of turbulence in inhomogeneous magnetized plasmas, showing that the heating power directly influences the turbulence. New mechanism, that an external source couples with plasma fluctuations in phase space so as to affect turbulence, is investigated. A new thermodynamical force in phase-space, i.e., the derivative of heating power by plasma pressure, plays the role of new control parameter, in addition to spatial gradients. Following the change of turbulence, turbulent transport is modified accordingly. The condition under which this new effect can be observed is also evaluated. PMID:23155481

New Thermodynamical Force in Plasma Phase Space that Controls Turbulence and Turbulent Transport

NASA Astrophysics Data System (ADS)

Itoh, Sanae-I.; Itoh, Kimitaka

2012-11-01

Physics of turbulence and turbulent transport has been developed on the central dogma that spatial gradients constitute the controlling parameters, such as Reynolds number and Rayleigh number. Recent experiments with the nonequilibrium plasmas in magnetic confinement devices, however, have shown that the turbulence and transport change much faster than global parameters, after an abrupt change of heating power. Here we propose a theory of turbulence in inhomogeneous magnetized plasmas, showing that the heating power directly influences the turbulence. New mechanism, that an external source couples with plasma fluctuations in phase space so as to affect turbulence, is investigated. A new thermodynamical force in phase-space, i.e., the derivative of heating power by plasma pressure, plays the role of new control parameter, in addition to spatial gradients. Following the change of turbulence, turbulent transport is modified accordingly. The condition under which this new effect can be observed is also evaluated.

Positive selection drives faster-Z evolution in silkmoths

PubMed Central

Sackton, Timothy B.; Corbett-Detig, Russell B.; Nagaraju, Javaregowda; Vaishna, R. Lakshmi; Arunkumar, Kallare P.; Hartl, Daniel L.

2014-01-01

Genes linked to X or Z chromosomes, which are hemizygous in the heterogametic sex, are predicted to evolve at different rates than those on autosomes. This “faster-X effect” can arise either as a consequence of hemizygosity, which leads to more efficient selection for recessive beneficial mutations in the heterogametic sex, or as a consequence of reduced effective population size of the hemizygous chromosome, which leads to increased fixation of weakly deleterious mutations due to genetic drift. Empirical results to date suggest that, while the overall pattern across taxa is complicated, systems with male-heterogamy show a faster-X effect attributable to more efficient selection, while the faster-Z effect in female-heterogametic taxa is attributable to increased drift. To test the generality of the faster-Z pattern seen in birds and snakes, we sequenced the genome of the Lepidopteran silkmoth Bombyx huttoni. We show that silkmoths experience faster-Z evolution, but unlike in birds and snakes, the faster-Z effect appears to be attributable to more efficient positive selection. These results suggest that female-heterogamy alone is unlikely to explain the reduced efficacy of selection on the bird Z chromosome. It is likely that many factors, including differences in overall effective population size, influence Z chromosome evolution. PMID:24826901

Experimental study on heat transfer performance of fin-tube exchanger and PSHE for waste heat recovery

NASA Astrophysics Data System (ADS)

Chen, Ting; Bae, Kyung Jin; Kwon, Oh Kyung

2018-02-01

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

A systematic review of cognitive decline in dementia with Lewy bodies versus Alzheimer’s disease

PubMed Central

2014-01-01

Introduction The aim of this review was to investigate whether there is a faster cognitive decline in dementia with Lewy bodies (DLB) than in Alzheimer’s disease (AD) over time. Methods PsycINFO and Medline were searched from 1946 to February 2013. A quality rating from 1 to 15 (best) was applied to the included studies. A quantitative meta-analysis was done on studies with mini mental state examination (MMSE) as the outcome measure. Results A total of 18 studies were included. Of these, six (36%) reported significant differences in the rate of cognitive decline. Three studies reported a faster cognitive decline on MMSE in patients with mixed DLB and AD compared to pure forms, whereas two studies reported a faster decline on delayed recall and recognition in AD and one in DLB on verbal fluency. Mean quality scores for studies that did or did not differ were not significantly different. Six studies reported MMSE scores and were included in the meta-analysis, which showed no significant difference in annual decline on MMSE between DLB (mean 3.4) and AD (mean 3.3). Conclusions Our findings do not support the hypothesis of a faster rate of cognitive decline in DLB compared to AD. Future studies should apply recent diagnostic criteria, as well as extensive diagnostic evaluation and ideally autopsy diagnosis. Studies with large enough samples, detailed cognitive tests, at least two years follow up and multivariate statistical analysis are also needed. PMID:25478024

Geochemistry of dissolved gases in the hypersaline Orca basin. Technical report

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

Wiesenburg, D.A.

1980-12-01

Hypersaline, anoxic waters significantly affect the biogeochemistry of dissolved gases in the Orca Basin (Northern Gulf of Mexico). The high stability of the Orca brine pool makes it an ideal laboratory for studying production and consumption of dissolved gases during anaerobic decomposition. Depth distributions were determined for nitrogen, oxygen, argon, methane, ethane, propane, ammonia, hydrogen sulfide, and nitrous oxide. Physical stratification of the water column strongly influences Orca Basin gas distributions. The high salinity brine (approx. 250%) is internally well mixed due to convective overturning, but transfer across the brine-sea water interface is controlled by molecular diffusion. With a molecularmore » diffusivity of 0.00001 sq cm/sec, it will take 1,000,000 years for all salts to diffuse from the basin. Heat diffuses faster than salt and is lost from the basin at a rate of 0.5 microcal sq cm/sec. If geothermal heat input from the sediments is slightly higher, this input could account for the higher temperature in the brine (5.6C) compared to the deep Gulf waters (4.2 C). This study has shown the utility of dissolved gases in examining water chemistry of unusual areas. Since sources of dissolved gases are independent of the sources of major ions in solution, calculations of gas distributions on a salt-free basis are useful in examining production and consumption processes.« less

Systematic biology analysis on photosynthetic carbon metabolism of maize leaf following sudden heat shock under elevated CO2.

PubMed

Qu, Mingnan; Chen, Genyun; Bunce, James A; Zhu, Xiaocen; Sicher, Richard C

2018-05-18

Plants would experience more complex environments, such as sudden heat shock (SHS) stress combined with elevated CO 2 in the future, and might adapt to this stressful condition by optimizing photosynthetic carbon metabolism (PCM). It is interesting to understand whether this acclimation process would be altered in different genotypes of maize under elevated CO 2 , and which metabolites represent key indicators reflecting the photosynthetic rates (P N ) following SHS. Although B76 had greater reduction in P N during SHS treatment, our results indicated that P N in genotype B76, displayed faster recovery after SHS treatment under elevated CO 2 than in genotype B106. Furthermore, we employed a stepwise feature extraction approach by partial linear regression model. Our findings demonstrated that 9 key metabolites over the total (35 metabolites) can largely explain the variance of P N during recovery from SHS across two maize genotypes and two CO 2 grown conditions. Of these key metabolites, malate, valine, isoleucine, glucose and starch are positively correlated with recovery pattern of P N . Malate metabolites responses to SHS were further discussed by incorporating with the activities and gene expression of three C 4 photosynthesis-related key enzymes. We highlighted the importance of malate metabolism during photosynthesis recovery from short-term SHS, and data integration analysis to better comprehend the regulatory framework of PCM in response to abiotic stress.

Acute cell death rate of vascular smooth muscle cells during or after short heating up to 20s ranging 50 to 60°C as a basic study of thermal angioplasty

NASA Astrophysics Data System (ADS)

Shinozuka, Machiko; Shimazaki, Natsumi; Ogawa, Emiyu; Machida, Naoki; Arai, Tsunenori

2014-02-01

We studied the relations between the time history of smooth muscle cells (SMCs) death rate and heating condition in vitro to clarify cell death mechanism in heating angioplasty, in particular under the condition in which intimal hyperplasia growth had been prevented in vivo swine experiment. A flow heating system on the microscope stage was used for the SMCs death rate measurement during or after the heating. The cells were loaded step-heating by heated flow using a heater equipped in a Photo-thermo dynamic balloon. The heating temperature was set to 37, 50-60°C. The SMCs death rate was calculated by a division of PI stained cell number by Hoechst33342 stained cell number. The SMCs death rate increased 5-10% linearly during 20 s with the heating. The SMCs death rate increased with duration up to 15 min after 5 s heating. Because fragmented nuclei were observed from approximately 5 min after the heating, we defined that acute necrosis and late necrosis were corresponded to within 5 min after the heating and over 5 min after the heating, respectively. This late necrosis is probably corresponding to apoptosis. The ratio of necrotic interaction divided the acute necrosis rate by the late necrosis was calculated based on this consideration as 1.3 under the particular condition in which intimal hyperplasia growth was prevented in vivo previous porcine experiment. We think that necrotic interaction rate is larger than expected rate to obtain intimal hyperplasia suppression.

Determinants of a simulated cross-country skiing sprint competition using V2 skating technique on roller skis.

PubMed

Mikkola, Jussi; Laaksonen, Marko; Holmberg, Hans-Christer; Vesterinen, Ville; Nummela, Ari

2010-04-01

The present study investigated the performance-predicting factors of a simulated cross-country (XC) skiing sprint competition on roller skis, on a slow surface. Sixteen elite male XC skiers performed a simulated sprint competition (4 x 850 m heat with a 20-minute recovery) using V2 skating technique on an indoor tartan track. Heat velocities, oxygen consumption, and peak lactate were measured during or after the heats. Maximal skiing velocity was measured by performing a 30-m speed test. Explosive and maximal force production in the upper body was determined by bench press (BP). Subjects also performed maximal anaerobic skiing test (MAST) and the 2 x 2-km double poling (DP) test. The maximal velocity of MAST (VMAST) and velocities at 3 (V3), 5 (V5), 7 (V7) mmol.L lactate levels in MAST were determined. In the 2 x 2-km test, DP economy (VO2SUBDP) and maximal 2-km DP velocity (VDP2KM) were determined. The best single performance-predicting factors for the sprint performance were VDP2KM (r = 0.73, p < 0.01), V7 (r = 0.70, p < 0.01), and VO2SUBDP (r = -0.70, p < 0.01). Faster skiers in sprint simulation had a higher absolute VO2 (L.min) (p < 0.05-0.01) during sprint heats, and higher anaerobic skiing power (VMAST, p < 0.05) and better anaerobic skiing economy (V3, V5, V7, p < 0.05-0.001) than slower skiers. Faster skiers were also stronger in BP, with regard to both absolute (p < 0.01) and relative (p < 0.05) values. In addition, anaerobic characteristics seem to be of importance at the beginning of the XC skiing sprint competition, whereas the aerobic characteristics become more important as the XC skiing sprint competition progressed. This study indicates that sprint skiers should emphasize sport-specific upper body training, and training skiing economy at high speeds.

Seismic imaging of the metamorphism of young sediment into new crystalline crust in the actively rifting Imperial Valley, California

USGS Publications Warehouse

Han, Liang; Hole, John; Stock, Joann; Fuis, Gary S.; Williams, Colin F.; Delph, Jonathan; Davenport, Kathy; Livers, Amanda

2016-01-01

Plate-boundary rifting between transform faults is opening the Imperial Valley of southern California and the rift is rapidly filling with sediment from the Colorado River. Three 65–90 km long seismic refraction profiles across and along the valley, acquired as part of the 2011 Salton Seismic Imaging Project, were analyzed to constrain upper crustal structure and the transition from sediment to underlying crystalline rock. Both first arrival travel-time tomography and frequency-domain full-waveform inversion were applied to provide P-wave velocity models down to ∼7 km depth. The valley margins are fault-bounded, beyond which thinner sediment has been deposited on preexisting crystalline rocks. Within the central basin, seismic velocity increases continuously from ∼1.8 km/s sediment at the surface to >6 km/s crystalline rock with no sharp discontinuity. Borehole data show young sediment is progressively metamorphosed into crystalline rock. The seismic velocity gradient with depth decreases approximately at the 4 km/s contour, which coincides with changes in the porosity and density gradient in borehole core samples. This change occurs at ∼3 km depth in most of the valley, but at only ∼1.5 km depth in the Salton Sea geothermal field. We interpret progressive metamorphism caused by high heat flow to be creating new crystalline crust throughout the valley at a rate comparable to the ≥2 km/Myr sedimentation rate. The newly formed crystalline crust extends to at least 7–8 km depth, and it is shallower and faster where heat flow is higher. Most of the active seismicity occurs within this new crust.

Seismic imaging of the metamorphism of young sediment into new crystalline crust in the actively rifting Imperial Valley, California

NASA Astrophysics Data System (ADS)

Han, Liang; Hole, John A.; Stock, Joann M.; Fuis, Gary S.; Williams, Colin F.; Delph, Jonathan R.; Davenport, Kathy K.; Livers, Amanda J.

2016-11-01

Plate-boundary rifting between transform faults is opening the Imperial Valley of southern California and the rift is rapidly filling with sediment from the Colorado River. Three 65-90 km long seismic refraction profiles across and along the valley, acquired as part of the 2011 Salton Seismic Imaging Project, were analyzed to constrain upper crustal structure and the transition from sediment to underlying crystalline rock. Both first arrival travel-time tomography and frequency-domain full-waveform inversion were applied to provide P-wave velocity models down to ˜7 km depth. The valley margins are fault-bounded, beyond which thinner sediment has been deposited on preexisting crystalline rocks. Within the central basin, seismic velocity increases continuously from ˜1.8 km/s sediment at the surface to >6 km/s crystalline rock with no sharp discontinuity. Borehole data show young sediment is progressively metamorphosed into crystalline rock. The seismic velocity gradient with depth decreases approximately at the 4 km/s contour, which coincides with changes in the porosity and density gradient in borehole core samples. This change occurs at ˜3 km depth in most of the valley, but at only ˜1.5 km depth in the Salton Sea geothermal field. We interpret progressive metamorphism caused by high heat flow to be creating new crystalline crust throughout the valley at a rate comparable to the ≥2 km/Myr sedimentation rate. The newly formed crystalline crust extends to at least 7-8 km depth, and it is shallower and faster where heat flow is higher. Most of the active seismicity occurs within this new crust.

Disease course in patients with autosomal recessive retinitis pigmentosa due to the USH2A gene.

PubMed

Sandberg, Michael A; Rosner, Bernard; Weigel-DiFranco, Carol; McGee, Terri L; Dryja, Thaddeus P; Berson, Eliot L

2008-12-01

To estimate the mean rates of ocular function loss in patients with autosomal recessive retinitis pigmentosa due to USH2A mutations. In 125 patients with USH2A mutations, longitudinal regression was used to estimate mean rates of change in Snellen visual acuity, Goldmann visual field area (V4e white test light), and 30-Hz (cone) full-field electroretinogram amplitude. These rates were compared with those of previously studied cohorts with dominant retinitis pigmentosa due to RHO mutations and with X-linked retinitis pigmentosa due to RPGR mutations. Rates of change in patients with the Cys759Phe mutation, the USH2A mutation associated with nonsyndromic disease, were compared with rates of change in patients with the Glu767fs mutation, the most common USH2A mutation associated with Usher syndrome type II (i.e., retinitis pigmentosa and hearing loss). Mean annual exponential rates of decline for the USH2A patients were 2.6% for visual acuity, 7.0% for visual field area, and 13.2% for electroretinogram amplitude. The rate of acuity loss fell between the corresponding rates for the RHO and RPGR patients, whereas the rates for field and ERG amplitude loss were faster than those for the RHO and RPGR patients. No significant differences were found for patients with the Cys759Phe mutation versus patients with the Glu767fs mutation. On average, USH2A patients lose visual acuity faster than RHO patients and slower than RPGR patients. USH2A patients lose visual field and cone electroretinogram amplitude faster than patients with RHO or RPGR mutations. Patients with a nonsyndromic USH2A mutation have the same retinal disease course as patients with syndromic USH2A disease.

Single-domain angiotensin I converting enzyme (kininase II): characterization and properties.

PubMed

Deddish, P A; Wang, L X; Jackman, H L; Michel, B; Wang, J; Skidgel, R A; Erdös, E G

1996-12-01

Somatic angiotensin I converting enzyme (ACE; kininase II) has two active sites, in two (N and C) domains. We studied the active centers with separate N-domain ACE (N-ACE), testicular C-domain ACE (germinal ACE) and, as control, renal somatic ACE. Germinal ACE cleaved the nonapeptide bradykinin about two times faster than N-ACE in 20 mM Cl-. Bradykinin1-7 was hydrolyzed further to bradykinin1-5 by N-ACE four times faster in the absence of Cl-, but at 300 mM Cl- the C-domain hydrolyzed it twice as fast. The hematopoietic system regulatory peptide acetyl-Ser-Asp-Lys-Pro was split to two dipeptides by N-ACE, depending on the chloride concentration, 8 to 24 times faster than by germinal ACE; at 100 mM Cl-, the Kcat with N-ACE was eight times higher. One millimolar 1-fluoro-2,4-dinitrobenzene inhibited germinal ACE 96% but it inhibited N-ACE by only 31%. [3H]Ramiprilat was displaced by other unlabeled ACE inhibitors to establish their relative affinities. Captopril had the lowest IC50 (0.5 nM) with N-ACE and the highest IC50 (8.3 nM) with the germinal ACE. The IC50 values of ramiprilat and quinaprilat were about the same with both active sites. The association and dissociation constants of [3H]ramiprilat indicated faster association with and faster dissociation from N-ACE than from germinal ACE. After exposure to alkali or moderate heat, somatic ACE was cleaved by plasmin and kallikrein, releasing N-ACE and apparently inactivating the C-domain. These studies affirm the differences in the activity, stability and inhibition of the two active sites of ACE.

Rates of genomic divergence in humans, chimpanzees and their lice.

PubMed

Johnson, Kevin P; Allen, Julie M; Olds, Brett P; Mugisha, Lawrence; Reed, David L; Paige, Ken N; Pittendrigh, Barry R

2014-02-22

The rate of DNA mutation and divergence is highly variable across the tree of life. However, the reasons underlying this variation are not well understood. Comparing the rates of genetic changes between hosts and parasite lineages that diverged at the same time is one way to begin to understand differences in genetic mutation and substitution rates. Such studies have indicated that the rate of genetic divergence in parasites is often faster than that of their hosts when comparing single genes. However, the variation in this relative rate of molecular evolution across different genes in the genome is unknown. We compared the rate of DNA sequence divergence between humans, chimpanzees and their ectoparasitic lice for 1534 protein-coding genes across their genomes. The rate of DNA substitution in these orthologous genes was on average 14 times faster for lice than for humans and chimpanzees. In addition, these rates were positively correlated across genes. Because this correlation only occurred for substitutions that changed the amino acid, this pattern is probably produced by similar functional constraints across the same genes in humans, chimpanzees and their ectoparasites.

Rates of genomic divergence in humans, chimpanzees and their lice

PubMed Central

Johnson, Kevin P.; Allen, Julie M.; Olds, Brett P.; Mugisha, Lawrence; Reed, David L.; Paige, Ken N.; Pittendrigh, Barry R.

2014-01-01

The rate of DNA mutation and divergence is highly variable across the tree of life. However, the reasons underlying this variation are not well understood. Comparing the rates of genetic changes between hosts and parasite lineages that diverged at the same time is one way to begin to understand differences in genetic mutation and substitution rates. Such studies have indicated that the rate of genetic divergence in parasites is often faster than that of their hosts when comparing single genes. However, the variation in this relative rate of molecular evolution across different genes in the genome is unknown. We compared the rate of DNA sequence divergence between humans, chimpanzees and their ectoparasitic lice for 1534 protein-coding genes across their genomes. The rate of DNA substitution in these orthologous genes was on average 14 times faster for lice than for humans and chimpanzees. In addition, these rates were positively correlated across genes. Because this correlation only occurred for substitutions that changed the amino acid, this pattern is probably produced by similar functional constraints across the same genes in humans, chimpanzees and their ectoparasites. PMID:24403325

Interplanetary space flight compared with fetal/neonatal motor strategy: Theoretical and practical implications.

PubMed

Meigal, Alexander

2012-09-01

The condition of simulated or real manned spaceflight, i.e. thermally comfortable microgravitation (G∼0), is very similar to the intrauterine immersion to the amniotic fluid. Domination of fast muscle fibers and phasic movements forms the fetal strategy to survive in heating, strongly hypoxic, albeit normal for fetus, immersion. In adults, the adaptive response separately to microgravitation, heat stress and hypoxia also shifts muscle fiber properties to faster values. That allows to speculate about specific motor strategy induced by micro-or hypogravitation (fetal/microgravitation, or FM-strategy). After birth the newborn is subjected to a combined 'sensory attack' of Earth gravitation, cooler ambient temperature and normoxia which is actually hyperoxic for fetus. The process of parturition can be considered as equivalent to cosmonaut's/astronaut's transition from microgravitation back to Earth gravitation (G=1) during landing. These factors also act simultaneously and constitute another set of sensory inputs with the effect that is opposite to the intrauterine condition. In normal gravitation, comfortable temperature and normoxia decreases the motor unit activity (MU) firing rate to a level, characteristic for the regular Earth condition. In contrast to 'faster' fetal adaptive motor response (microgravitation, heat, hypoxia), the post-natal adult set of conditions (lower, but still normal temperature, normoxia, 1G gravitation, healthy maturation) may represent the 'Earth' adaptive motor response, or the (gravitation/Earth, or GE-strategy). The motor system undergoes a second profound remodeling in older people during healthy ageing that results in further domination of slow muscle fibers and slowing down motor unit activity, simulating the condition of hypergravitation (G>1). Similar slowing adaptive responses are represented by cold and hyperoxia thus forming further motor strategy that could be named as SJ-strategy (after 'slow' and Jupiter - the most massive planet and the only planet with G>1 in the solar system). These strategies suppose that definite sensory inputs and conditions may substitute each other due to its equivalent action on the motor system. Thus, cold 'sensory attack' may serve as a 'surrogate' for gravitation because these two conditions exert equivalent stimulating action on muscle tone. In that respect long-term mild cooling exposures or shorter severe cold exposures may be considered as a prophylactic countermeasure against hazardous action of weightlessness. Also, combination of cooling sensory intervention with traditional and well- documented interventions (whole body vibration and stimulation of 'support zone' afferents) may elevate their anti-microgravitation efficiency. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Kraken: ultrafast metagenomic sequence classification using exact alignments

PubMed Central

2014-01-01

Kraken is an ultrafast and highly accurate program for assigning taxonomic labels to metagenomic DNA sequences. Previous programs designed for this task have been relatively slow and computationally expensive, forcing researchers to use faster abundance estimation programs, which only classify small subsets of metagenomic data. Using exact alignment of k-mers, Kraken achieves classification accuracy comparable to the fastest BLAST program. In its fastest mode, Kraken classifies 100 base pair reads at a rate of over 4.1 million reads per minute, 909 times faster than Megablast and 11 times faster than the abundance estimation program MetaPhlAn. Kraken is available at http://ccb.jhu.edu/software/kraken/. PMID:24580807

Thermal Scanning Conductometry (TSC) as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels.

PubMed

Bielejewski, Michal

2018-01-23

The thermal scanning conductometry protocol is a new approach in studying ionic gels based on low molecular weight gelators. The method is designed to follow the dynamically changing state of the ionogels, and to deliver more information and details about the subtle change of conductive properties with an increase or decrease in the temperature. Moreover, the method allows the performance of long term (i.e. days, weeks) measurements at a constant temperature to investigate the stability and durability of the system and the aging effects. The main advantage of the TSC method over classical conductometry is the ability to perform measurements during the gelation process, which was impossible with the classical method due to temperature stabilization, which usually takes a long time before the individual measurement. It is a well-known fact that to obtain the physical gel phase, the cooling stage must be fast; moreover, depending on the cooling rate, different microstructures can be achieved. The TSC method can be performed with any cooling/heating rate that can be assured by the external temperature system. In our case, we can achieve linear temperature change rates between 0.1 and approximately 10 °C/min. The thermal scanning conductometry is designed to work in cycles, continuously changing between heating and cooling stages. Such an approach allows study of the reproducibility of the thermally reversible gel-sol phase transition. Moreover, it allows the performance of different experimental protocols on the same sample, which can be refreshed to initial state (if necessary) without removal from the measuring cell. Therefore, the measurements can be performed faster, in a more efficient way, and with much higher reproducibility and accuracy. Additionally, the TSC method can be also used as a tool to manufacture the ionogels with targeted properties, like microstructure, with an instant characterization of conductive properties.

Melting temperature and enthalpy variations of phase change materials (PCMs): a differential scanning calorimetry (DSC) analysis

NASA Astrophysics Data System (ADS)

Sun, Xiaoqin; Lee, Kyoung Ok; Medina, Mario A.; Chu, Youhong; Li, Chuanchang

2018-06-01

Differential scanning calorimetry (DSC) analysis is a standard thermal analysis technique used to determine the phase transition temperature, enthalpy, heat of fusion, specific heat and activation energy of phase change materials (PCMs). To determine the appropriate heating rate and sample mass, various DSC measurements were carried out using two kinds of PCMs, namely N-octadecane paraffin and calcium chloride hexahydrate. The variations in phase transition temperature, enthalpy, heat of fusion, specific heat and activation energy were observed within applicable heating rates and sample masses. It was found that the phase transition temperature range increased with increasing heating rate and sample mass; while the heat of fusion varied without any established pattern. The specific heat decreased with the increase of heating rate and sample mass. For accuracy purpose, it is recommended that for PCMs with high thermal conductivity (e.g. hydrated salt) the focus will be on heating rate rather than sample mass.

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

Wong, Melissa; Bolovan-Fritts, Cynthia; Dar, Roy D.

Signal transduction circuits have long been known to differentiate between signals by amplifying inputs to different levels. Here, we describe a novel transcriptional circuitry that dynamically converts greater input levels into faster rates, without increasing the final equilibrium level (i.e. a rate amplifier). We utilize time-lapse microscopy to study human herpesvirus (cytomegalovirus) infection of live cells in real time. Strikingly, our results show that transcriptional activators accelerate viral gene expression in single cells without amplifying the steady-state levels of gene products in these cells. Experiment and modeling show that rate amplification operates by dynamically manipulating the traditional gain-bandwidth feedback relationshipmore » from electrical circuit theory to convert greater input levels into faster rates, and is driven by highly self-cooperative transcriptional feedback encoded by the virus s essential transactivator, IE2. This transcriptional rate-amplifier provides a significant fitness advantage for the virus and for minimal synthetic circuits. In general, rate-amplifiers may provide a mechanism for signal-transduction circuits to respond quickly to external signals without increasing steady-state levels of potentially cytotoxic molecules.« less

The Influence of Stellar Spin on Ignition of Thermonuclear Runaways

NASA Astrophysics Data System (ADS)

Galloway, Duncan K.; in ’t Zand, Jean J. M.; Chenevez, Jérôme; Keek, Laurens; Sanchez-Fernandez, Celia; Worpel, Hauke; Lampe, Nathanael; Kuulkers, Erik; Watts, Anna; Ootes, Laura; The MINBAR collaboration

2018-04-01

Runaway thermonuclear burning of a layer of accumulated fuel on the surface of a compact star provides a brief but intense display of stellar nuclear processes. For neutron stars accreting from a binary companion, these events manifest as thermonuclear (type-I) X-ray bursts, and recur on typical timescales of hours to days. We measured the burst rate as a function of accretion rate, from seven neutron stars with known spin rates, using a burst sample accumulated over several decades. At the highest accretion rates, the burst rate is lower for faster spinning stars. The observations imply that fast (>400 Hz) rotation encourages stabilization of nuclear burning, suggesting a dynamical dependence of nuclear ignition on the spin rate. This dependence is unexpected, because faster rotation entails less shear between the surrounding accretion disk and the star. Large-scale circulation in the fuel layer, leading to enhanced mixing of the burst ashes into the fuel layer, may explain this behavior; further numerical simulations are required to confirm this.

Large Eddy Simulation of Heat Entrainment Under Arctic Sea Ice

NASA Astrophysics Data System (ADS)

Ramudu, Eshwan; Gelderloos, Renske; Yang, Di; Meneveau, Charles; Gnanadesikan, Anand

2018-01-01

Arctic sea ice has declined rapidly in recent decades. The faster than projected retreat suggests that free-running large-scale climate models may not be accurately representing some key processes. The small-scale turbulent entrainment of heat from the mixed layer could be one such process. To better understand this mechanism, we model the Arctic Ocean's Canada Basin, which is characterized by a perennial anomalously warm Pacific Summer Water (PSW) layer residing at the base of the mixed layer and a summertime Near-Surface Temperature Maximum (NSTM) within the mixed layer trapping heat from solar radiation. We use large eddy simulation (LES) to investigate heat entrainment for different ice-drift velocities and different initial temperature profiles. The value of LES is that the resolved turbulent fluxes are greater than the subgrid-scale fluxes for most of our parameter space. The results show that the presence of the NSTM enhances heat entrainment from the mixed layer. Additionally there is no PSW heat entrained under the parameter space considered. We propose a scaling law for the ocean-to-ice heat flux which depends on the initial temperature anomaly in the NSTM layer and the ice-drift velocity. A case study of "The Great Arctic Cyclone of 2012" gives a turbulent heat flux from the mixed layer that is approximately 70% of the total ocean-to-ice heat flux estimated from the PIOMAS model often used for short-term predictions. Present results highlight the need for large-scale climate models to account for the NSTM layer.

Atomistic modelling of evaporation and explosive boiling of thin film liquid argon over internally recessed nanostructured surface

NASA Astrophysics Data System (ADS)

Hasan, Mohammad Nasim; Shavik, Sheikh Mohammad; Rabbi, Kazi Fazle; Haque, Mominul

2016-07-01

Molecular dynamics (MD) simulations have been carried out to investigate evaporation and explosive boiling phenomena of thin film liquid argon on nanostructured solid surface with emphasis on the effect of solid-liquid interfacial wettability. The nanostructured surface considered herein consists of trapezoidal internal recesses of the solid platinum wall. The wetting conditions of the solid surface were assumed such that it covers both the hydrophilic and hydrophobic conditions and hence effect of interfacial wettability on resulting evaporation and boiling phenomena was the main focus of this study. The initial configuration of the simulation domain comprised of a three phase system (solid platinum, liquid argon and vapor argon) on which equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. After equilibrium of the three-phase system was established, the wall was set to different temperatures (130 K and 250 K for the case of evaporation and explosive boiling respectively) to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat flux normal to the solid surface was also calculated to illustrate the effectiveness of heat transfer for hydrophilic and hydrophobic surfaces in cases of both nanostructured surface and flat surface. The results obtained show that both the wetting condition of the surface and the presence of internal recesses have significant effect on normal evaporation and explosive boiling of the thin liquid film. The heat transfer from solid to liquid in cases of surface with recesses are higher compared to flat surface without recesses. Also the surface with higher wettability (hydrophilic) provides more favorable conditions for boiling than the low-wetting surface (hydrophobic) and therefore, liquid argon responds quickly and shifts from liquid to vapor phase faster in case of hydrophilic surface. The heat transfer rate is also much higher in case of hydrophilic surface.

Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

NASA Astrophysics Data System (ADS)

Reinink, Shawn K.; Yaras, Metin I.

2015-06-01

Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal property gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between hairpin vortices causes them to interact more frequently by merging together and by breaking apart into smaller turbulence structures.

Atomistic modelling of evaporation and explosive boiling of thin film liquid argon over internally recessed nanostructured surface

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

Hasan, Mohammad Nasim, E-mail: nasim@me.buet.ac.bd.com; Shavik, Sheikh Mohammad, E-mail: shavik@me.buet.ac.bd.com; Rabbi, Kazi Fazle, E-mail: rabbi35.me10@gmail.com

2016-07-12

Molecular dynamics (MD) simulations have been carried out to investigate evaporation and explosive boiling phenomena of thin film liquid argon on nanostructured solid surface with emphasis on the effect of solid-liquid interfacial wettability. The nanostructured surface considered herein consists of trapezoidal internal recesses of the solid platinum wall. The wetting conditions of the solid surface were assumed such that it covers both the hydrophilic and hydrophobic conditions and hence effect of interfacial wettability on resulting evaporation and boiling phenomena was the main focus of this study. The initial configuration of the simulation domain comprised of a three phase system (solidmore » platinum, liquid argon and vapor argon) on which equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. After equilibrium of the three-phase system was established, the wall was set to different temperatures (130 K and 250 K for the case of evaporation and explosive boiling respectively) to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat flux normal to the solid surface was also calculated to illustrate the effectiveness of heat transfer for hydrophilic and hydrophobic surfaces in cases of both nanostructured surface and flat surface. The results obtained show that both the wetting condition of the surface and the presence of internal recesses have significant effect on normal evaporation and explosive boiling of the thin liquid film. The heat transfer from solid to liquid in cases of surface with recesses are higher compared to flat surface without recesses. Also the surface with higher wettability (hydrophilic) provides more favorable conditions for boiling than the low-wetting surface (hydrophobic) and therefore, liquid argon responds quickly and shifts from liquid to vapor phase faster in case of hydrophilic surface. The heat transfer rate is also much higher in case of hydrophilic surface.« less

Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

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

Reinink, Shawn K.; Yaras, Metin I., E-mail: Metin.Yaras@carleton.ca

2015-06-15

Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal propertymore » gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between hairpin vortices causes them to interact more frequently by merging together and by breaking apart into smaller turbulence structures.« less

Individual Differences in Beat Perception Affect Gait Responses to Low- and High-Groove Music

PubMed Central

Leow, Li-Ann; Parrott, Taylor; Grahn, Jessica A.

2014-01-01

Slowed gait in patients with Parkinson’s disease (PD) can be improved when patients synchronize footsteps to isochronous metronome cues, but limited retention of such improvements suggest that permanent cueing regimes are needed for long-term improvements. If so, music might make permanent cueing regimes more pleasant, improving adherence; however, music cueing requires patients to synchronize movements to the “beat,” which might be difficult for patients with PD who tend to show weak beat perception. One solution may be to use high-groove music, which has high beat salience that may facilitate synchronization, and affective properties, which may improve motivation to move. As a first step to understanding how beat perception affects gait in complex neurological disorders, we examined how beat perception ability affected gait in neurotypical adults. Synchronization performance and gait parameters were assessed as healthy young adults with strong or weak beat perception synchronized to low-groove music, high-groove music, and metronome cues. High-groove music was predicted to elicit better synchronization than low-groove music, due to its higher beat salience. Two musical tempi, or rates, were used: (1) preferred tempo: beat rate matched to preferred step rate and (2) faster tempo: beat rate adjusted to 22.5% faster than preferred step rate. For both strong and weak beat-perceivers, synchronization performance was best with metronome cues, followed by high-groove music, and worst with low-groove music. In addition, high-groove music elicited longer and faster steps than low-groove music, both at preferred tempo and at faster tempo. Low-groove music was particularly detrimental to gait in weak beat-perceivers, who showed slower and shorter steps compared to uncued walking. The findings show that individual differences in beat perception affect gait when synchronizing footsteps to music, and have implications for using music in gait rehabilitation. PMID:25374521

Thermomechanical behavior of mica layers with lenticular fissures

NASA Astrophysics Data System (ADS)

Yang, Michael Xinyi

The thermomechanical behavior of natural phlogopite mica specimens from seven different origins is characterized. An initial heat treatment, to a temperature between 300°C and 400°C, is found to form fissures that stabilize in the material. Following the initial heat treatment, all the phlogopite specimens, regardless of their origin and polytype, exhibit the extraordinarily large thermal expansion (intumescence), more than 200% at 600°C, in the direction perpendicular to the basal planes. This phenomenon is strictly reproducible when tested under a range of thermal conditions including thermal shock, multiple thermal fatigue cycles, varying heating or cooling rates and isothermal heating over an extensive period of time at different temperatures up to 585°C. The hysteresis, associated with the thermal cycle, is increased when the specimen is heated or cooled at a faster rate. The maximum coefficient of linear thermal expansion, approximately 10 -2°C-1, is observed over the temperature range 100--120°C. This is due to the non-structural water, entrapped within the layer structure, which undergoes a phase transition and causes the mica layers to expand abruptly. A model of lenticular fissures is developed based on thin-plate mechanics and thermodynamics assumptions. The state of a lenticular fissure with water vapor molecules is determined to correlate the experimental parameters with the material properties. The average density of water vapor molecules within a lenticular fissure is calculated to be ˜1025 m 3 for the temperature interval between 100°C and 275°C. The concentration of non-structure water, based on the model calculation, is less than 0.1% by weight. Acoustic emission (AE) signals have been reported by Pranevicius et al. (1995) to correspond to the microstructure changes as the internal lenticular fissures develop in phlogopite. This technique has also been proven feasible to characterize the thermomechanical behavior of other layer structures (Pranevicius 1995). Other layer structures are reviewed to determine their potential reversible thermomechanical properties. When phlogopite is used as a model specimen to relate microstructure to intumescence, two criteria are established for selection of the layer structures of potential intumescence. The first is the need for flexible and elastic layers to withstand the strain imposed by large lateral expansion. The second is the requirement of a high degree for intercalation. Possible candidates that fit these two criteria are identified. Finally, a few potential applications of layer structures of intumescence are discussed, and future research in this area is proposed. (Abstract shortened by UMI.)

Heat accumulation period in the Mediterranean region: phenological response of the olive in different climate areas (Spain, Italy and Tunisia).

PubMed

Aguilera, Fátima; Ruiz, Luis; Fornaciari, Marco; Romano, Bruno; Galán, Carmen; Oteros, Jose; Ben Dhiab, Ali; Msallem, Monji; Orlandi, Fabio

2014-07-01

The main characteristics of the heat accumulation period and the possible existence of different types of biological response to the environment in different populations of olive through the Mediterranean region have been evaluated. Chilling curves to determine the start date of the heat accumulation period were constructed and evaluated. The results allow us to conclude that the northern olive populations have the greatest heat requirements for the development of their floral buds, and they need a period of time longer than olives in others areas to completely satisfy their biothermic requirements. The olive trees located in the warmest winter areas have a faster transition from endogenous to exogenous inhibition once the peak of chilling is met, and they show more rapid floral development. The lower heat requirements are due to better adaptation to warmer regions. Both the threshold temperature and the peak of flowering date are closely related to latitude. Different types of biological responses of olives to the environment were found. The adaptive capacity shown by the olive tree should be considered as a useful tool with which to study the effects of global climatic change on agro-ecosystems.

Does laser-driven heat front propagation depend on material microstructure?

NASA Astrophysics Data System (ADS)

Colvin, J. D.; Matsukuma, H.; Fournier, K. B.; Yoga, A.; Kemp, G. E.; Tanaka, N.; Zhang, Z.; Kota, K.; Tosaki, S.; Ikenouchi, T.; Nishimura, H.

2016-10-01

We showed earlier that the laser-driven heat front propagation velocity in low-density Ti-silica aerogel and TiO2 foam targets was slower than that simulated with a 2D radiation-hydrodynamics code incorporating an atomic kinetics model in non-LTE and assuming initially homogeneous material. Some theoretical models suggest that the heat front is slowed over what it would be in a homogeneous medium by the microstructure of the foam. In order to test this hypothesis we designed and conducted a comparison experiment on the GEKKO laser to measure heat front propagation velocity in two targets, one an Ar/CO2 gas mixture and the other a TiO2 foam, that had identical initial densities and average ionization states. We found that the heat front traveled about ten times faster in the gas than in the foam. We present the details of the experiment design and a comparison of the data with the simulations. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract No. DE-AC52-07NA27344, and the joint research project of ILE Osaka U. (contract Nos. 2014A1-04 and 2015A1-02).

Rate and Pattern of Rim Area Loss in Healthy and Progressing Glaucoma Eyes

PubMed Central

Hammel, Na’ama; Belghith, Akram; Bowd, Christopher; Medeiros, Felipe A.; Sharpsten, Lucie; Mendoza, Nadia; Tatham, Andrew J.; Khachatryan, Naira; Liebmann, Jeffrey M.; Girkin, Christopher A.; Weinreb, Robert N.; Zangwill, Linda M.

2015-01-01

Objective To characterize the rate and pattern of age-related and glaucomatous neuroretinal rim area changes in subjects of African descent (AD) and European descent (ED). Design Prospective longitudinal study. Subjects 296 eyes of 157 healthy subjects (88 AD and 69 ED) and 73 progressing glaucoma eyes of 67 subjects (24 AD and 43 ED) from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES) were included. Methods Global and sectoral rim area was measured using confocal laser scanning ophthalmoscopy (CSLO). Progression of glaucomatous optic disc damage was determined by masked stereophoto review. The rates of absolute rim area loss and percent rim area loss in healthy and progressing glaucomatous eyes were compared using multivariable nested mixed-effects models. Main Outcome Measures Rate of rim area loss over time. Results The median (inter-quartile range) follow-up time was 5.0 years (2.0–7.4) for healthy eyes and 8.3 years (7.5–9.9) for progressing glaucoma eyes. The mean rate of global rim area loss was significantly faster in progressing glaucoma eyes compared with healthy eyes for both rim area loss (−10.2 ×10−3 mm2/year vs. −2.8 ×10−3 mm2/year, respectively, P<.001) and percent rim area loss (−1.1 %/year vs. −0.2 %/year, respectively, P<.001), but there was considerable overlap between the two groups. 63% of progressing glaucoma eyes had a rate of change faster than the 5th quantile of healthy eyes. For both healthy and progressing eyes, the pattern of rim area loss and percent rim area loss was similar; it tended to be fastest in the superior temporal and inferior temporal sectors. The rate of change was similar in AD and ED progressing eyes. Conclusions Compared with healthy eyes, the mean rate of global rim area loss was 3.7 times faster and the mean rate of global percent rim area loss was 5.4 times faster in progressing glaucoma eyes. A reference database of healthy eyes can be used to help clinicians distinguish age-related rim area loss from rim area loss due to glaucoma. PMID:26746597

Molecular dynamics study on evaporation and condensation characteristics of thin film liquid Argon on nanostructured surface in nano-scale confinement

NASA Astrophysics Data System (ADS)

Hasan, Mohammad Nasim; Rabbi, Kazi Fazle; Sabah, Arefiny; Ahmed, Jannat; Kuri, Subrata Kumar; Rakibuzzaman, S. M.

2017-06-01

Investigation of Molecular level phase change phenomena are becoming important in heat and mass transfer research at a very high rate, driven both by the need to understand certain fundamental phenomena as well as by a plethora of new and forthcoming applications in the areas of micro- and nanotechnologies. Molecular dynamics simulation has been carried out to go through the evaporation and condensation characteristics of thin liquid argon film in Nano-scale confinement. In the present study, a cuboid system is modeled for understanding the Nano-scale physics of simultaneous evaporation and condensation. The cuboid system consists of hot and cold parallel platinum plates at the bottom and top ends. The fluid comprised of liquid argon film at the bottom plate and vapor argon in between liquid argon and upper plate of the domain. Three different simulation domains have been created here: (i) Both platinum plates are considered flat, (ii) Upper plate consisting of transverse slots of low height and (iii) Upper plate consisting of transverse slots of bigger height. Considering hydrophilic nature of top and bottom plates, two different high temperatures of the hot wall was set and an observation was made on normal and explosive vaporizations and their impacts on thermal transport. For all the structures, equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. Then the lower wall is set to two different temperatures like 110 K and 250 K for all three models to perform non-equilibrium molecular dynamics (NEMD). For vaporization, higher temperature of the hot wall led to faster transport of the liquid argon as a cluster moving from hot wall to cold wall. But excessive temperature causes explosive boiling which seems not good for heat transportation because of less phase change. In case of condensation, an observation was made which indicates that the nanostructured transverse slots facilitate condensation. Two factors affect the rate of condensation when nanostructures are there: (i) increased surface area and (ii) the nanostructure height. The variation of temperature and evaporation number with respect to time was monitored for all cases. An estimation of heat fluxes normal to top and bottom walls also was made to focus the effectiveness of heat transfer in hydrophilic confinement.

Chronic heat improves mechanical and metabolic response of trained rat heart on ischemia and reperfusion.

PubMed

Levy, E; Hasin, Y; Navon, G; Horowitz, M

1997-05-01

Cardiac mechanics and metabolic performance were studied in isolated perfused hearts of rats subjected to a combined chronic stress of heat acclimation and swimming training (EXAC) or swimming training alone (EX). Diastolic (DP) and systolic pressures (SP), coronary flow (CF), and oxygen consumption were measured during normoperfusion (80 mmHg), and the appearance of ischemic contracture (IC), DP, and SP were measured during progressive graded ischemia, total ischemia (TI), and reperfusion insults. ATP, phosphocreatine, and intracellular pH were measured during TI and reperfusion with 31P nuclear magnetic resonance spectroscopy. During normoperfusion, SP and cardiac efficiency (derived from rate-pressure product-oxygen consumption relationships) were the highest in the 2-mo EXAC hearts (P < 0.0001). During progressive graded ischemia, the development of IC (percentage of total hearts) was similar in both EXAC and EX hearts; the only significant difference was confined to the 1- vs. 2-mo groups. The onset of IC was delayed in the EXAC hearts and, on reperfusion, recovery, particularly of DP, was significantly improved in the latter. After TI, EXAC hearts retained 30% of the ATP pool and there was a delayed decline in intracellular pH. On reperfusion, these hearts also displayed improved ATP and phosphocreatine recovery, the 2-mo EXAC heart demonstrating significantly faster high-energy phosphate salvage, improved diastolic function, and pulse pressure recovery. The data attest to the beneficial effects of heat acclimation on cardiac mechanics of trained rats during normoperfusion and cardiac protection on ischemia and reperfusion. Possibly, energy sparing, lesser acidosis, and shorter duration of IC on ischemia and improved energy salvage on reperfusion contribute synergistically to this potent beneficial effect.

Relationship Between Rates of Binocular Visual Field Loss and Vision-Related Quality of Life in Glaucoma

PubMed Central

Lisboa, Renato; Chun, Yeoun Sook; Zangwill, Linda M.; Weinreb, Robert N.; Rosen, Peter N.; Liebmann, Jeffrey M.; Girkin, Christopher A.; Medeiros, Felipe A.

2013-01-01

Objective To evaluate the relationship between binocular rates of visual field change and vision-related quality of life (VRQOL) in glaucoma. Methods The study included 796 eyes of 398 participants that had diagnosed or suspected glaucoma followed for an average of 7.3 ± 2.0 years. Subjects were recruited from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES). VRQOL was evaluated using the National Eye Institute Visual Function Questionnaire (NEI VFQ-25) at the last follow-up visit. Integrated binocular visual fields (BVF) were calculated from the monocular fields of each patient. Linear regression of mean deviation (MD) values was used to evaluate rates of visual field change during the follow-up period. Logistic regression models were used to investigate the relationship between abnormal VRQOL and rates of visual field change, while adjusting for potentially confounding socio-economic and demographic variables. Results Thirty-two patients (8.0%) had abnormal VRQOL as determined by the results of the NEI VFQ-25 questionnaire. Subjects with abnormal VRQOL had significantly faster rates of BVF change than those with normal VRQOL (−0.18 db/year vs. −0.06 dB/year, respectively; P < 0.001). Rates of BVF change were significantly associated with abnormality in VRQOL (OR = 1.31 per 0.1dB/year faster; P = 0.038), after adjustment for confounding variables. Conclusions Patients with faster rates of BVF change were at higher risk of reporting abnormal VRQOL. Assessment of rates of BVF change may provide useful information in determining risk of functional impairment in glaucoma. PMID:23450425

Aerodynamic heating and surface temperatures on vehicles for computer-aided design studies

NASA Technical Reports Server (NTRS)

Dejarnette, F. R.; Kania, L. A.; Chitty, A.

1983-01-01

A computer subprogram has been developed to calculate aerodynamic and radiative heating rates and to determine surface temperatures by integrating the heating rates along the trajectory of a vehicle. Convective heating rates are calculated by applying the axisymmetric analogue to inviscid surface streamlines and using relatively simple techniques to calculate laminar, transitional, or turbulent heating rates. Options are provided for the selection of gas model, transition criterion, turbulent heating method, Reynolds Analogy factor, and entropy-layer swallowing effects. Heating rates are compared to experimental data, and the time history of surface temperatures are given for a high-speed trajectory. The computer subprogram is developed for preliminary design and mission analysis where parametric studies are needed at all speeds.

On the heat capacity of elements in WMD regime

NASA Astrophysics Data System (ADS)

Hamel, Sebatien

2014-03-01

Once thought to get simpler with increasing pressure, elemental systems have been discovered to exhibit complex structures and multiple phases at high pressure. For carbon, QMD/PIMC simulations have been performed and the results are guiding alternative modelling methodologies for constructing a carbon equation-of-state covering the warm dense matter regime. One of the main results of our new QMD/PIMC carbon equation of state is that the decay of the ion-thermal specific heat with temperature is much faster than previously expected. An important question is whether this is only found in carbon and not other element. In this presentation, based on QMD calculations for several elements, we explore trends in the transition from condensed matter to warm dense matter regime.

Selection for rapid embryo development correlates with embryo exposure to maternal androgens among passerine birds

USGS Publications Warehouse

Schwabl, H.; Palacios, M.G.; Martin, T.E.

2007-01-01

Greater offspring predation favors evolution of faster development among species. We hypothesized that greater offspring predation exerts selection on mothers to increase levels of anabolic androgens in egg yolks to achieve faster development. Here, we tested whether (1) concentrations of yolk androgens in passerine species were associated with offspring predation and (2) embryo and nestling development rates were associated with yolk androgen concentrations. We examined three androgens that increase in potency along the synthesis pathway: androstenedione (A4) to testosterone (T) to 5??- dihydrotestosterone (5??-DHT). Concentrations of none of these steroids were related to clutch size; only A4 was allometrically related to egg volume. Species that experience greater predation showed higher yolk concentrations of T and 5??-DHT. Higher concentrations of T and particularly 5??-DHT were strongly correlated with faster development during the embryo period and less so during the nestling period. Development rates were most strongly correlated with 5??-DHT, suggesting that potency increases along the androgen synthesis pathway and that effects are mediated by the androgen receptor pathway. These results are consistent with the hypothesis that selection for faster development by time-dependent offspring mortality may be achieved epigenetically by varying embryo exposure to maternal anabolic steroids. ?? 2007 by The University of Chicago. All rights reserved.

Lung cancer death rates fall, helping drive decrease in overall cancer death rates

Cancer.gov

The Annual Report to the Nation on the Status of Cancer, covering the period 1975–2010, showed death rates for lung cancer, which accounts for more than one in four cancer deaths, dropping at a faster pace than in previous years.

Spatially resolved heat release rate measurements in turbulent premixed flames

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

Ayoola, B.O.; Kaminski, C.F.; Balachandran, R.

Heat release rate is a fundamental property of great importance for the theoretical and experimental elucidation of unsteady flame behaviors such as combustion noise, combustion instabilities, and pulsed combustion. Investigations of such thermoacoustic interactions require a reliable indicator of heat release rate capable of resolving spatial structures in turbulent flames. Traditionally, heat release rate has been estimated via OH or CH radical chemiluminescence; however, chemiluminescence suffers from being a line-of-sight technique with limited capability for resolving small-scale structures. In this paper, we report spatially resolved two-dimensional measurements of a quantity closely related to heat release rate. The diagnostic technique usesmore » simultaneous OH and CH{sub 2}O planar laser-induced fluorescence (PLIF), and the pixel-by-pixel product of the OH and CH{sub 2}O PLIF signals has previously been shown to correlate well with local heat release rates. Results from this diagnostic technique, which we refer to as heat release rate imaging (HR imaging), are compared with traditional OH chemiluminescence measurements in several flames. Studies were performed in lean premixed ethylene flames stabilized between opposed jets and with a bluff body. Correlations between bulk strain rates and local heat release rates were obtained and the effects of curvature on heat release rate were investigated. The results show that the heat release rate tends to increase with increasing negative curvature for the flames investigated for which Lewis numbers are greater than unity. This correlation becomes more pronounced as the flame gets closer to global extinction.« less

Bypass valve and coolant flow controls for optimum temperatures in waste heat recovery systems

DOEpatents

Meisner, Gregory P

2013-10-08

Implementing an optimized waste heat recovery system includes calculating a temperature and a rate of change in temperature of a heat exchanger of a waste heat recovery system, and predicting a temperature and a rate of change in temperature of a material flowing through a channel of the waste heat recovery system. Upon determining the rate of change in the temperature of the material is predicted to be higher than the rate of change in the temperature of the heat exchanger, the optimized waste heat recovery system calculates a valve position and timing for the channel that is configurable for achieving a rate of material flow that is determined to produce and maintain a defined threshold temperature of the heat exchanger, and actuates the valve according to the calculated valve position and calculated timing.

Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; İpek, Osman

2017-02-01

In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

Mechanisms of material removal and mass transport in focused ion beam nanopore formation

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

Das, Kallol, E-mail: das7@illinois.edu; Johnson, Harley T., E-mail: htj@illinois.edu; Freund, Jonathan B., E-mail: jbfreund@illinois.edu

2015-02-28

Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can bemore » shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions.« less

Trajectories of Infants' Biobehavioral Development: Timing and Rate of A-Not-B Performance Gains and EEG Maturation.

PubMed

MacNeill, Leigha A; Ram, Nilam; Bell, Martha Ann; Fox, Nathan A; Pérez-Edgar, Koraly

2018-05-01

This study examined how timing (i.e., relative maturity) and rate (i.e., how quickly infants attain proficiency) of A-not-B performance were related to changes in brain activity from age 6 to 12 months. A-not-B performance and resting EEG (electroencephalography) were measured monthly from age 6 to 12 months in 28 infants and were modeled using logistic and linear growth curve models. Infants with faster performance rates reached performance milestones earlier. Infants with faster rates of increase in A-not-B performance had lower occipital power at 6 months and greater linear increases in occipital power. The results underscore the importance of considering nonlinear change processes for studying infants' cognitive development as well as how these changes are related to trajectories of EEG power. © 2018 The Authors. Child Development © 2018 Society for Research in Child Development, Inc.

40 CFR 75.83 - Calculation of Hg mass emissions and heat input rate.

Code of Federal Regulations, 2010 CFR

2010-07-01

... heat input rate. 75.83 Section 75.83 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Calculation of Hg mass emissions and heat input rate. The owner or operator shall calculate Hg mass emissions and heat input rate in accordance with the procedures in sections 9.1 through 9.3 of appendix F to...

Simultaneous determination of thermal conductivity, thermal diffusivity and specific heat in sI methane hydrate

USGS Publications Warehouse

Waite, W.F.; Stern, L.A.; Kirby, S.H.; Winters, W.J.; Mason, D.H.

2007-01-01

Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between −20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment.

Laser-heated emissive plasma probe.

PubMed

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K

2008-08-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

Characteristics and performance of the variable polarity plasma arc welding process used in the Space Shuttle external tank

NASA Technical Reports Server (NTRS)

Hung, R. J.; Lee, C. C.; Liu, J. W.

1990-01-01

Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. Flow profiles and power distribution of argon plasma gas as a working fluid to produce plasma arc jet in the VPPA welding process was analyzed. Major loss of heat transfer for flow through the nozzle is convective heat transfer; for the plasma jet flow between the outlet of the nozzle and workpiece is radiative heat transfer; and for the flow through the keyhole of the workpiece is convective heat transfer. The majority of the power absorbed by the keyhole of the workpiece is used for melting the solid metal workpiece into a molten metallic puddle. The crown and root widths and the crown and root heights can be predicted. An algorithm for promoting automatic control of flow parameters and the dimensions of the final product of the welding specification to be used for the VPPA Welding System operated at MSFC are provided.

A Review of Aerothermal Modeling for Mars Entry Missions

NASA Technical Reports Server (NTRS)

Wright, Michael J; Tang, Chun Y.; Edquist, Karl T.; Hollis, Brian R.; Krasa, Paul

2009-01-01

The current status of aerothermal analysis for Mars entry missions is reviewed. The aeroheating environment of all Mars missions to date has been dominated by convective heating. Two primary uncertainties in our ability to predict forebody convective heating are turbulence on a blunt lifting cone and surface catalysis in a predominantly CO2 environment. Future missions, particularly crewed vehicles, will encounter additional heating from shock-layer radiation due to a combination of larger size and faster entry velocity. Localized heating due to penetrations or other singularities on the aeroshell must also be taken into account. The physical models employed to predict these phenomena are reviewed, and key uncertainties or deficiencies inherent in these models are explored. Capabilities of existing ground test facilities to support aeroheating validation are also summarized. Engineering flight data from the Viking and Pathfinder missions, which may be useful for aerothermal model validation, are discussed, and an argument is presented for obtaining additional flight data. Examples are taken from past, present, and future Mars entry missions, including the twin Mars Exploration Rovers and the Mars Science Laboratory, scheduled for launch by NASA in 2011.

Catalytic Ignition and Upstream Reaction Propagation in Monolith Reactors

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Dietrich, Daniel L.; Miller, Fletcher J.; T'ien, James S.

2007-01-01

Using numerical simulations, this work demonstrates a concept called back-end ignition for lighting-off and pre-heating a catalytic monolith in a power generation system. In this concept, a downstream heat source (e.g. a flame) or resistive heating in the downstream portion of the monolith initiates a localized catalytic reaction which subsequently propagates upstream and heats the entire monolith. The simulations used a transient numerical model of a single catalytic channel which characterizes the behavior of the entire monolith. The model treats both the gas and solid phases and includes detailed homogeneous and heterogeneous reactions. An important parameter in the model for back-end ignition is upstream heat conduction along the solid. The simulations used both dry and wet CO chemistry as a model fuel for the proof-of-concept calculations; the presence of water vapor can trigger homogenous reactions, provided that gas-phase temperatures are adequately high and there is sufficient fuel remaining after surface reactions. With sufficiently high inlet equivalence ratio, back-end ignition occurs using the thermophysical properties of both a ceramic and metal monolith (coated with platinum in both cases), with the heat-up times significantly faster for the metal monolith. For lower equivalence ratios, back-end ignition occurs without upstream propagation. Once light-off and propagation occur, the inlet equivalence ratio could be reduced significantly while still maintaining an ignited monolith as demonstrated by calculations using complete monolith heating.

The characteristics of heat flow in the Shenhu gas hydrate drilling area, northern South China Sea

NASA Astrophysics Data System (ADS)

Xu, Xing; Wan, Zhifeng; Wang, Xianqing; Sun, Yuefeng; Xia, Bin

2016-12-01

Marine heat flow is of great significance for the formation and occurrence of seabed oil, gas and gas hydrate resources. Geothermal gradient is an important parameter in determining the thickness of the hydrate stability zone. The northern slope of the South China Sea is rich in gas hydrate resources. Several borehole drilling attempts were successful in finding hydrates in the Shenhu area, while others were not. The failures demand further study on the distribution regularities of heat flow and its controlling effects on hydrate occurrence. In this study, forty-eight heat flow measurements are analyzed in the Shenhu gas hydrate drilling area, located in the northern South China Sea, together with their relationship to topography, sedimentary environment and tectonic setting. Canyons are well developed in the study area, caused mainly by the development of faults, faster sediment supply and slumping of the Pearl River Estuary since the late Miocene in the northern South China Sea. The heat flow values in grooves, occurring always in fault zones, are higher than those of ridges. Additionally, the heat flow values gradually increase from the inner fan, to the middle fan, to the external fan subfacies. The locations with low heat flow such as ridges, locations away from faults and the middle fan subfacies, are more conducive to gas hydrate occurrence.

Visual monitoring of the melting front propagation in a paraffin-based PCM

NASA Astrophysics Data System (ADS)

Charvát, Pavel; Štětina, Josef; Mauder, Tomáš; Klimeš, Lubomír

Experiments were carried out in an environmental chamber with the aim to monitor the melting front propagation in a rectangular cavity filled with a paraffin-based Phase Change Material (PCM). The PCM was contained in transparent containers with the heat flux introduced by means of an electric heating element. The stabilized power source was used to maintain the constant heat output of the heating elements. The experiments were performed for the heat flux introduced at the side wall of the container and at the upper surface of the PCM. The paraffin-based PCM RT28HC with the phase change temperature of 28 °C was used in the experiments. The temperature in the environmental chamber was maintained at the melting temperature of the PCM. The propagation of the melting front was monitored with a digital camera and temperatures at several locations were monitored with RTDs and thermocouples. Significant natural convection was observed for the heat flux introduced at the side wall of the container. As a result the melting front propagated much faster at the top of the container than at its bottom. The heat flux introduced at the upper-surface of the PCM resulted in almost one-dimensional propagation of the melting front. The acquired data are to be used for validation of an in-house developed numerical model based on the front-tracking method.

Is thermal dispersivity significant for the use of heat as a tracer?

NASA Astrophysics Data System (ADS)

Rau, G. C.; Andersen, M. S.; Acworth, I.

2011-12-01

Heat profiles are regularly used to estimate sediment thermal parameters and to quantify vertical water flow velocity in fully saturated porous media. However, it has been pointed out by several authors that there is disagreement regarding the use of thermal dispersivity in heat transport models [e.g. Anderson, 2005]. Some researchers argue that this term should be treated analogous to solute transport [e.g. de Marsily, 1986], whilst others state that because heat diffusion is much faster than solute diffusion the dispersivity term can be neglected [e.g. Ingebritsen and Sanford, 1998]. This issue has never been properly addressed experimentally for environmentally relevant conditions. In order to address this question a hydraulic laboratory experiment was designed to investigate heat transport for different steady-state uniform flow velocities in the Darcy range (between 0 and 100 m/d) through homogeneous sand. For each flow velocity a point heat source at the center of the tank was instantaneously activated, and the thermal response was measured at 27 different locations using high resolution temperature probes. For the same flow velocities, a solute slug was injected in the center of the tank and the solute slug breakthrough was measured using 3 fluid EC sensors at different distances downstream of the injection point. This enabled direct comparison of solute and heat transport under identical conditions. The recorded temperature time-series data were used to calculate the thermal properties of the sand for conduction only, and estimate water flow velocity and thermal dispersion. The recorded EC time-series data were used to independently estimate water flow velocity but also solute dispersivity. The analytical solution for the solute transport case [Hunt, 1978] was adapted for heat transport and extended to account for slightly non-ideal experiment conditions. Velocity results independently derived from solute and heat show a discrepancy of up to 20%. The reason for this is not clear. Furthermore, the results show that thermal dispersivity can best be approximated with a square dependency on flow velocity. This agrees with earlier experiments in ideal materials by Green et al. [1964] as well as theoretical derivations [Kaviany, 1995]. However, this is in contrast to the linear dispersion model which has been adapted from solute transport and is commonly used in groundwater studies. The experimental results can be visualized in a conceptual plot devised by Bear [1972] for solute dispersion data (Figure 1). From this it becomes clear that the heat and solute transport Peclet numbers differs by several orders of magnitude for the same flow velocity and material because diffusion of heat is much faster than solute diffusion. As a result, the same Darcy flow range covers a different Peclet number range in heat transport and solute transport. This explains the controversy in the hydrologic community regarding the use of thermal dispersivity in transport models. In summary, for this experiment thermal dispersivity can be neglected when thermal Pe < 0.5, but should be considered for Pe > 0.5 with a square dependency on velocity.

Afterbody Heating Predictions for a Mars Science Laboratory Entry Vehicle

NASA Technical Reports Server (NTRS)

Edquist, Karl T.

2005-01-01

The Mars Science Laboratory mission intends to deliver a large rover to the Martian surface within 10 km of its target site. One candidate entry vehicle aeroshell consists of a 3.75-m diameter, 70-deg sphere-cone forebody and a biconic afterbody similar to that of Viking. This paper presents computational fluid dynamics predictions of laminar afterbody heating rates for this configuration and a 2010 arrival at Mars. Computational solutions at flight conditions used an 8-species Mars gas model in chemical and thermal non-equilibrium. A grid resolution study examined the effects of mesh spacing on afterbody heating rates and resulted in grids used for heating predictions on a reference entry trajectory. Afterbody heating rate reaches its maximum value near 0.6 W/sq cm on the first windward afterbody cone at the time of peak freestream dynamic pressure. Predicted afterbody heating rates generally are below 3% of the forebody laminar nose cap heating rate throughout the design trajectory. The heating rates integrated over time provide total heat load during entry, which drives thermal protection material thickness.

Cardiorespiratory Kinetics Determined by Pseudo-Random Binary Sequences - Comparisons between Walking and Cycling.

PubMed

Koschate, J; Drescher, U; Thieschäfer, L; Heine, O; Baum, K; Hoffmann, U

2016-12-01

This study aims to compare cardiorespiratory kinetics as a response to a standardised work rate protocol with pseudo-random binary sequences between cycling and walking in young healthy subjects. Muscular and pulmonary oxygen uptake (V̇O 2 ) kinetics as well as heart rate kinetics were expected to be similar for walking and cycling. Cardiac data and V̇O 2 of 23 healthy young subjects were measured in response to pseudo-random binary sequences. Kinetics were assessed applying time series analysis. Higher maxima of cross-correlation functions between work rate and the respective parameter indicate faster kinetics responses. Muscular V̇O 2 kinetics were estimated from heart rate and pulmonary V̇O 2 using a circulatory model. Muscular (walking vs. cycling [mean±SD in arbitrary units]: 0.40±0.08 vs. 0.41±0.08) and pulmonary V̇O 2 kinetics (0.35±0.06 vs. 0.35±0.06) were not different, although the time courses of the cross-correlation functions of pulmonary V̇O 2 showed unexpected biphasic responses. Heart rate kinetics (0.50±0.14 vs. 0.40±0.14; P=0.017) was faster for walking. Regarding the biphasic cross-correlation functions of pulmonary V̇O 2 during walking, the assessment of muscular V̇O 2 kinetics via pseudo-random binary sequences requires a circulatory model to account for cardio-dynamic distortions. Faster heart rate kinetics for walking should be considered by comparing results from cycle and treadmill ergometry. © Georg Thieme Verlag KG Stuttgart · New York.

Patterns of Interspecific Variation in the Heart Rates of Embryonic Reptiles

PubMed Central

Du, Wei-Guo; Ye, Hua; Zhao, Bo; Pizzatto, Ligia; Ji, Xiang; Shine, Richard

2011-01-01

New non-invasive technologies allow direct measurement of heart rates (and thus, developmental rates) of embryos. We applied these methods to a diverse array of oviparous reptiles (24 species of lizards, 18 snakes, 11 turtles, 1 crocodilian), to identify general influences on cardiac rates during embryogenesis. Heart rates increased with ambient temperature in all lineages, but (at the same temperature) were faster in lizards and turtles than in snakes and crocodilians. We analysed these data within a phylogenetic framework. Embryonic heart rates were faster in species with smaller adult sizes, smaller egg sizes, and shorter incubation periods. Phylogenetic changes in heart rates were negatively correlated with concurrent changes in adult body mass and residual incubation period among the lizards, snakes (especially within pythons) and crocodilians. The total number of embryonic heart beats between oviposition and hatching was lower in squamates than in turtles or the crocodilian. Within squamates, embryonic iguanians and gekkonids required more heartbeats to complete development than did embryos of the other squamate families that we tested. These differences plausibly reflect phylogenetic divergence in the proportion of embryogenesis completed before versus after laying. PMID:22174948

X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

DOE PAGES

Harris, William H.; Guillen, Donna P.; Klouzek, Jaroslav; ...

2017-05-10

The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fractions at temperatures between 600°C and 1040°C. Tomore » track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower total amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.« less

X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

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

Harris, William H.; Guillen, Donna P.; Klouzek, Jaroslav

The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fractions at temperatures between 600°C and 1040°C. Tomore » track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower total amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.« less

Observations of Urban Heat Island Mitigation in California Coastal Cities due to a Sea Breeze Induced Coastal-Cooling ``REVERSE-REACTION'' to Global Warming

NASA Astrophysics Data System (ADS)

Bornstein, R. D.; Lebassi, B.; Gonzalez, J.

2010-12-01

The study evaluated long-term (1948-2005) air temperatures at over 300 urban and rural sites in California (CA) during summer (June-August, JJA). The aggregate CA results showed asymmetric warming, as daily min temperatures increased faster than daily max temperatures. The spatial distributions of daily max temperatures in the heavily urbanized South Coast and San Francisco Bay Area air basins, however, exhibited a complex pattern, with cooling at low-elevation (mainly urban) coastal-areas and warming at (mainly rural) inland areas. Previous studies have suggested that cooling summer max temperatures in CA were due to increased irrigation, coastal upwelling, or cloud cover. The current hypothesis, however, is that this temperature pattern arises from a “reverse-reaction” to greenhouse gas (GHG) induced global-warming. In this hypothesis, the global warming of inland areas resulted in an increased (cooling) sea breeze activity in coastal areas. That daytime summer coastal cooling was seen in coastal urban areas implies that urban heat island (UHI) warming was weaker than the reverse-reaction sea breeze cooling; if there was no UHI effect, then the cooling would have been even stronger. Analysis of daytime summer max temperatures at four adjacent pairs of urban and rural sites near the inland cooling-warming boundary, however, showed that the rural sites experienced cooling, while the urban sites showed warming due to UHI development. The rate of heat island growth was estimated as the sum of each urban warming rate and the absolute magnitude of the concurrent adjacent rural cooling rate. Values ranged from 0.12 to 0.55 K decade-1, and were proportional to changes in urban population and urban extent. As Sacramento, Modesto, Stockton, and San José have grown in aerial extent (21 to 59%) and population (40 to 118%), part of the observed increased JJA max values could be due to increased daytime UHI-intensity. Without UHI effects, the currently observed JJA SFBA coastal-cooling area might have expanded to include these sites, as the first three are adjacent to rural airport sites that showed cooling max-values due to increased marine influences. In addition, all urbanized sites with decreasing max-values would probably show even larger cooling rates if UHI effects could be removed. Significant societal impacts may result from this observed reverse-reaction to GHG-warming. Possible beneficial effects (especially during periods of UHI growth) include decreased maximum: O3 levels, per-capita energy requirements for cooling, and human thermal-stress levels.

Experimental and Numerical Study of Ammonium Perchlorate Counterflow Diffusion Flames

NASA Technical Reports Server (NTRS)

Smooke, M. D.; Yetter, R. A.; Parr, T. P.; Hanson-Parr, D. M.; Tanoff, M. A.

1999-01-01

Many solid rocket propellants are based on a composite mixture of ammonium perchlorate (AP) oxidizer and polymeric binder fuels. In these propellants, complex three-dimensional diffusion flame structures between the AP and binder decomposition products, dependent upon the length scales of the heterogeneous mixture, drive the combustion via heat transfer back to the surface. Changing the AP crystal size changes the burn rate of such propellants. Large AP crystals are governed by the cooler AP self-deflagration flame and burn slowly, while small AP crystals are governed more by the hot diffusion flame with the binder and burn faster. This allows control of composite propellant ballistic properties via particle size variation. Previous measurements on these diffusion flames in the planar two-dimensional sandwich configuration yielded insight into controlling flame structure, but there are several drawbacks that make comparison with modeling difficult. First, the flames are two-dimensional and this makes modeling much more complex computationally than with one-dimensional problems, such as RDX self- and laser-supported deflagration. In addition, little is known about the nature, concentration, and evolution rates of the gaseous chemical species produced by the various binders as they decompose. This makes comparison with models quite difficult. Alternatively, counterflow flames provide an excellent geometric configuration within which AP/binder diffusion flames can be studied both experimentally and computationally.

Stepwise crystallization and the layered distribution in crystallization kinetics of ultra-thin poly(ethylene terephthalate) film

NASA Astrophysics Data System (ADS)

Zuo, Biao; Xu, Jianquan; Sun, Shuzheng; Liu, Yue; Yang, Juping; Zhang, Li; Wang, Xinping

2016-06-01

Crystallization is an important property of polymeric materials. In conventional viewpoint, the transformation of disordered chains into crystals is usually a spatially homogeneous process (i.e., it occurs simultaneously throughout the sample), that is, the crystallization rate at each local position within the sample is almost the same. Here, we show that crystallization of ultra-thin poly(ethylene terephthalate) (PET) films can occur in the heterogeneous way, exhibiting a stepwise crystallization process. We found that the layered distribution of glass transition dynamics of thin film modifies the corresponding crystallization behavior, giving rise to the layered distribution of the crystallization kinetics of PET films, with an 11-nm-thick surface layer having faster crystallization rate and the underlying layer showing bulk-like behavior. The layered distribution in crystallization kinetics results in a particular stepwise crystallization behavior during heating the sample, with the two cold-crystallization temperatures separated by up to 20 K. Meanwhile, interfacial interaction is crucial for the occurrence of the heterogeneous crystallization, as the thin film crystallizes simultaneously if the interfacial interaction is relatively strong. We anticipate that this mechanism of stepwise crystallization of thin polymeric films will allow new insight into the chain organization in confined environments and permit independent manipulation of localized properties of nanomaterials.

Effect of high pressure homogenization on the structure and the interfacial and emulsifying properties of β-lactoglobulin.

PubMed

Ali, Ali; Le Potier, Isabelle; Huang, Nicolas; Rosilio, Véronique; Cheron, Monique; Faivre, Vincent; Turbica, Isabelle; Agnely, Florence; Mekhloufi, Ghozlene

2018-02-15

The effect of high pressure homogenization (HPH) on the structure of β-lactoglobulin (β-lg) was studied by combining spectroscopic, chromatographic, and electrophoretic methods. The consequences of the resulting structure modifications on oil/water (O/W) interfacial properties were also assessed. Moderated HPH treatment (100 MPa/4 cycles) showed no significant modification of protein structure and interfacial properties. However, a harsher HPH treatment (300 MPa/5 cycles) induced structural transformation, mainly from β-sheets to random coils, wide loss in lipocalin core, and protein aggregation via intermolecular disulfide bridges. HPH-modified β-lg displayed higher surface hydrophobicity leading to a faster adsorption rate at the interface and an earlier formation of an elastic interfacial film at C β-lg  = 0.1 wt%. However, no modification of the interfacial properties was observed at C β-lg  = 1 wt%. At this protein concentration, the prior denaturation of β-lg by HPH did not modify the droplet size of nanoemulsions prepared with these β-lg solutions as the aqueous phases. A slightly increased creaming rate was however observed. The effects of HPH and heat denaturations appeared qualitatively similar, but with differences in their extent. Copyright © 2017 Elsevier B.V. All rights reserved.

Stepwise crystallization and the layered distribution in crystallization kinetics of ultra-thin poly(ethylene terephthalate) film

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

Zuo, Biao, E-mail: chemizuo@zstu.edu.cn, E-mail: wxinping@yahoo.com; Xu, Jianquan; Sun, Shuzheng

2016-06-21

Crystallization is an important property of polymeric materials. In conventional viewpoint, the transformation of disordered chains into crystals is usually a spatially homogeneous process (i.e., it occurs simultaneously throughout the sample), that is, the crystallization rate at each local position within the sample is almost the same. Here, we show that crystallization of ultra-thin poly(ethylene terephthalate) (PET) films can occur in the heterogeneous way, exhibiting a stepwise crystallization process. We found that the layered distribution of glass transition dynamics of thin film modifies the corresponding crystallization behavior, giving rise to the layered distribution of the crystallization kinetics of PET films,more » with an 11-nm-thick surface layer having faster crystallization rate and the underlying layer showing bulk-like behavior. The layered distribution in crystallization kinetics results in a particular stepwise crystallization behavior during heating the sample, with the two cold-crystallization temperatures separated by up to 20 K. Meanwhile, interfacial interaction is crucial for the occurrence of the heterogeneous crystallization, as the thin film crystallizes simultaneously if the interfacial interaction is relatively strong. We anticipate that this mechanism of stepwise crystallization of thin polymeric films will allow new insight into the chain organization in confined environments and permit independent manipulation of localized properties of nanomaterials.« less

Optimization of protein solution by a novel experimental design method using thermodynamic properties.

PubMed

Kim, Nam Ah; An, In Bok; Lee, Sang Yeol; Park, Eun-Seok; Jeong, Seong Hoon

2012-09-01

In this study, the structural stability of hen egg white lysozyme in solution at various pH levels and in different types of buffers, including acetate, phosphate, histidine, and Tris, was investigated by means of differential scanning calorimetry (DSC). Reasonable pH values were selected from the buffer ranges and were analyzed statistically through design of experiment (DoE). Four factors were used to characterize the thermograms: calorimetric enthalpy (ΔH), temperature at maximum heat flux (T( m )), van't Hoff enthalpy (ΔH( V )), and apparent activation energy of protein solution (E(app)). It was possible to calculate E(app) through mathematical elaboration from the Lumry-Eyring model by changing the scan rate. The transition temperature of protein solution, T( m ), increased when the scan rate was faster. When comparing the T( m ), ΔH( V ), ΔH, and E(app) of lysozyme in various pH ranges and buffers with different priorities, lysozyme in acetate buffer at pH 4.767 (scenario 9) to pH 4.969 (scenario 11) exhibited the highest thermodynamic stability. Through this experiment, we found a significant difference in the thermal stability of lysozyme in various pH ranges and buffers and also a new approach to investigate the physical stability of protein by DoE.

The Relationship between Speech Rate and Memory Span in Children.

ERIC Educational Resources Information Center

Henry, Lucy A.

1994-01-01

Examined whether speech rate is related to the amount recalled and if developmental increases in speech rate allow faster rehearsal with age, and hence, greater recall. Found that the group relationship was clear and replicable but that speech rates of individual children were not good predictors of those children's memory spans; age was found to…

Testing the Effectiveness of the iRelate Program on Marines: An Enhanced Program Evaluation

ERIC Educational Resources Information Center

Lloyd, Griselda M.

2017-01-01

Junior enlisted Marines are getting married at a faster rate than their civilian counterparts and nearly twice that of senior personnel (Gomulka, 2010; Cohen, Passel, Wang, & Livingston, 2011). With the high rate of marriage, these same junior Marines have a disproportionately high divorce rate. While the high rate of divorce is a significant…

High-power laser interaction with low-density C–Cu foams

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

Pérez, F.; Colvin, J. D.; May, M. J.

2015-11-15

We study the propagation of high-power laser beams in micro-structured carbon foams by monitoring the x-ray output from deliberately introduced Cu content. In particular, we characterize this phenomenon measuring absolute time-resolved x-ray yields, time-resolved x-ray imaging, and x-ray spectroscopy. New experimental results for C–Cu foams show a faster heat front velocity than simulation that assumed homogeneous plasma. We suggest the foam micro-structure may explain this trend.

Local Stretching Theories

DTIC Science & Technology

2010-06-24

diffusivity of the scalar. (If the scalar is heat, then the Schmidt number becomes the Prandtl number.) Momentum diffuses significantly faster than the...derive the Cramér function explicitly in the simple case where the xi have a Bernoulli distribution, though the general formula for S may be derived by...an analogous procedure. 5 Large deviation CLT for the Bernoulli distribution Let xi have the PDF of a fair coin, p(xi) = 1 2δ(xi + 1) + 1 2δ(xi − 1

High-power laser interaction with low-density C–Cu foams

DOE PAGES

Pérez, F.; Colvin, J. D.; May, M. J.; ...

2015-11-19

Here, we study the propagation of high-power laser beams in micro-structured carbon foams by monitoring the x-ray output from deliberately introduced Cu content. In particular, we characterize this phenomenon measuring absolute time-resolved x-ray yields, time-resolved x-ray imaging, and x-ray spectroscopy. New experimental results for C–Cu foams show a faster heat front velocity than simulation that assumed homogeneous plasma. We suggest the foam micro-structure may explain this trend.

Tolerence for work-induced heat stress in men wearing liquidcooled garments

NASA Technical Reports Server (NTRS)

Blockley, W. V.; Roth, H. P.

1971-01-01

An investigation of the heat tolerance in men unable to dispose of metabolic heat as fast as it is produced within the body is discussed. Examinations were made of (a) the effect of work rate (metabolic rate) on tolerance time when body heat storage rate is a fixed quantity, and (b) tolerance time as a function of metabolic rate when heat loss is terminated after a thermal quasi-equilibrium was attained under comfortable conditions of heat transfer. The nature of the physiological mechanisms involved in such heat stress situations, and the possibility of using prediction techniques to establish standard procedures in emergencies involving cooling system failures are also discussed.

40 CFR 75.36 - Missing data procedures for heat input rate determinations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 16 2011-07-01 2011-07-01 false Missing data procedures for heat input... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING Missing Data Substitution Procedures § 75.36 Missing data procedures for heat input rate determinations. (a) When hourly heat input rate is...

40 CFR 75.36 - Missing data procedures for heat input rate determinations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Missing data procedures for heat input... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING Missing Data Substitution Procedures § 75.36 Missing data procedures for heat input rate determinations. (a) When hourly heat input rate is...

40 CFR 75.36 - Missing data procedures for heat input rate determinations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Missing data procedures for heat input... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING Missing Data Substitution Procedures § 75.36 Missing data procedures for heat input rate determinations. (a) When hourly heat input rate is...

40 CFR 75.36 - Missing data procedures for heat input rate determinations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Missing data procedures for heat input... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING Missing Data Substitution Procedures § 75.36 Missing data procedures for heat input rate determinations. (a) When hourly heat input rate is...

40 CFR 75.36 - Missing data procedures for heat input rate determinations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 17 2012-07-01 2012-07-01 false Missing data procedures for heat input... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING Missing Data Substitution Procedures § 75.36 Missing data procedures for heat input rate determinations. (a) When hourly heat input rate is...

Laminar and turbulent heating predictions for mars entry vehicles

NASA Astrophysics Data System (ADS)

Wang, Xiaoyong; Yan, Chao; Zheng, Weilin; Zhong, Kang; Geng, Yunfei

2016-11-01

Laminar and turbulent heating rates play an important role in the design of Mars entry vehicles. Two distinct gas models, thermochemical non-equilibrium (real gas) model and perfect gas model with specified effective specific heat ratio, are utilized to investigate the aerothermodynamics of Mars entry vehicle named Mars Science Laboratory (MSL). Menter shear stress transport (SST) turbulent model with compressible correction is implemented to take account of the turbulent effect. The laminar and turbulent heating rates of the two gas models are compared and analyzed in detail. The laminar heating rates predicted by the two gas models are nearly the same at forebody of the vehicle, while the turbulent heating environments predicted by the real gas model are severer than the perfect gas model. The difference of specific heat ratio between the two gas models not only induces the flow structure's discrepancy but also increases the heating rates at afterbody of the vehicle obviously. Simple correlations for turbulent heating augmentation in terms of laminar momentum thickness Reynolds number, which can be employed as engineering level design and analysis tools, are also developed from numerical results. At the time of peak heat flux on the +3σ heat load trajectory, the maximum value of momentum thickness Reynolds number at the MSL's forebody is about 500, and the maximum value of turbulent augmentation factor (turbulent heating rates divided by laminar heating rates) is 5 for perfect gas model and 8 for real gas model.

Method and apparatus for obtaining enhanced production rate of thermal chemical reactions

DOEpatents

Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Wegeng, Robert S [Richland, WA; Gao, Yufei [Kennewick, WA

2003-04-01

The present invention is a method and apparatus (vessel) for providing a heat transfer rate from a reaction chamber through a wall to a heat transfer chamber substantially matching a local heat transfer rate of a catalytic thermal chemical reaction. The key to the invention is a thermal distance defined on a cross sectional plane through the vessel inclusive of a heat transfer chamber, reaction chamber and a wall between the chambers. The cross sectional plane is perpendicular to a bulk flow direction of the reactant stream, and the thermal distance is a distance between a coolest position and a hottest position on the cross sectional plane. The thermal distance is of a length wherein the heat transfer rate from the reaction chamber to the heat transfer chamber substantially matches the local heat transfer rate.

Work Rate during Self-paced Exercise is not Mediated by the Rate of Heat Storage.

PubMed

Friesen, Brian J; Périard, Julien D; Poirier, Martin P; Lauzon, Martin; Blondin, Denis P; Haman, Francois; Kenny, Glen P

2018-01-01

To date, there have been mixed findings on whether greater anticipatory reductions in self-paced exercise intensity in the heat are mediated by early differences in rate of body heat storage. The disparity may be due to an inability to accurately measure minute-to-minute changes in whole-body heat loss. Thus, we evaluated whether early differences in rate of heat storage can mediate exercise intensity during self-paced cycling at a fixed rate of perceived exertion (RPE of 16; hard-to-very-hard work effort) in COOL (15°C), NORMAL (25°C), and HOT (35°C) ambient conditions. On separate days, nine endurance-trained cyclists exercised in COOL, NORMAL, and HOT conditions at a fixed RPE until work rate (measured after first 5 min of exercise) decreased to 70% of starting values. Whole-body heat loss and metabolic heat production were measured by direct and indirect calorimetry, respectively. Total exercise time was shorter in HOT (57 ± 20 min) relative to both NORMAL (72 ± 23 min, P = 0.004) and COOL (70 ± 26 min, P = 0.045). Starting work rate was lower in HOT (153 ± 31 W) compared with NORMAL (166 ± 27 W, P = 0.024) and COOL (170 ± 33 W, P = 0.037). Rate of heat storage was similar between conditions during the first 4 min of exercise (all P > 0.05). Thereafter, rate of heat storage was lower in HOT relative to NORMAL and COOL until 30 min of exercise (last common time-point between conditions; all P < 0.05). Further, rate of heat storage was significantly higher in COOL compared with NORMAL at 15 min (P = 0.026) and 20 min (P = 0.020) of exercise. No differences were measured at end exercise. We show that rate of heat storage does not mediate exercise intensity during self-paced exercise at a fixed RPE in cool to hot ambient conditions.

Cooperative Electrocatalytic O 2 Reduction Involving Co(salophen) with p- Hydroquinone as an Electron–Proton Transfer Mediator

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

Anson, Colin W.; Stahl, Shannon S.

2017-12-01

The molecular cobalt complex, Co(salophen), and para-hydroquinone (H2Q) serve as effective cocatalysts for the electrochemical reduction of O2 to water. Mechanistic studies reveal redox cooperativity between Co(salophen) and H2Q. H2Q serves as an electron-proton transfer mediator (EPTM) that enables electrochemical O2 reduction at higher potentials and with faster rates than is observed with Co(salophen) alone. Replacement of H2Q with the higher potential EPTM, 2-chloro-H2Q, allows for faster O2 reduction rates at higher applied potential. These results demonstrate a unique strategy to achieve improved performance with molecular electrocatalyst systems.

A novel compact heat exchanger using gap flow mechanism.

PubMed

Liang, J S; Zhang, Y; Wang, D Z; Luo, T P; Ren, T Q

2015-02-01

A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.

Columbia: The first five flights entry heating data series. Volume 2: The OMS Pod

NASA Technical Reports Server (NTRS)

Williams, S. D.

1983-01-01

Entry heating flight data and wind tunnel data on the OMS Pod are presented for the first five flights of the Space Shuttle Orbiter. The heating rate data are presented in terms of normalized film heat transfer coefficients as a function of angle-of-attack, Mach number, and normal shock Reynolds number. The surface heating rates and temperatures were obtained via the JSC NONLIN/INVERSE computer program. Time history plots of the surface heating rates and temperatures are also presented.

Real-time aerodynamic heating and surface temperature calculations for hypersonic flight simulation

NASA Technical Reports Server (NTRS)

Quinn, Robert D.; Gong, Leslie

1990-01-01

A real-time heating algorithm was derived and installed on the Ames Research Center Dryden Flight Research Facility real-time flight simulator. This program can calculate two- and three-dimensional stagnation point surface heating rates and surface temperatures. The two-dimensional calculations can be made with or without leading-edge sweep. In addition, upper and lower surface heating rates and surface temperatures for flat plates, wedges, and cones can be calculated. Laminar or turbulent heating can be calculated, with boundary-layer transition made a function of free-stream Reynolds number and free-stream Mach number. Real-time heating rates and surface temperatures calculated for a generic hypersonic vehicle are presented and compared with more exact values computed by a batch aeroheating program. As these comparisons show, the heating algorithm used on the flight simulator calculates surface heating rates and temperatures well within the accuracy required to evaluate flight profiles for acceptable heating trajectories.

Convective Heat Transfer Scaling of Ignition Delay and Burning Rate with Heat Flux and Stretch Rate in the Equivalent Low Stretch Apparatus

NASA Technical Reports Server (NTRS)

Olson, Sandra

2011-01-01

To better evaluate the buoyant contributions to the convective cooling (or heating) inherent in normal-gravity material flammability test methods, we derive a convective heat transfer correlation that can be used to account for the forced convective stretch effects on the net radiant heat flux for both ignition delay time and burning rate. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone heater to minimize buoyant effects while at the same time providing a forced stagnation flow on the sample, which ignites and burns as a ceiling fire. Ignition delay and burning rate data is correlated with incident heat flux and convective heat transfer and compared to results from other test methods and fuel geometries using similarity to determine the equivalent stretch rates and thus convective cooling (or heating) rates for those geometries. With this correlation methodology, buoyant effects inherent in normal gravity material flammability test methods can be estimated, to better apply the test results to low stretch environments relevant to spacecraft material selection.

Effect of heating rate on thermal cracking characteristics and kinetics of Xinjiang oil sand bitumen by TG-FTIR

NASA Astrophysics Data System (ADS)

Hao, Junhui; Zhang, Jinhong; Qiao, Yingyun; Tian, Yuanyu

2017-08-01

This work was aimed to investigate effects of heating rate on thermal cracking behaviors, distribution of gaseous products and activation energy of the thermal cracking process of Xinjiang oil sand bitumen (OSB). The thermal cracking experiments of Xinjiang OSB were performed by using thermogravimetric analyzer (TGA) at various heating rates of 10, 20, 50, 80 and 120 K/min. The evolving characteristic of gaseous products produced from the thermal cracking process was evaluated by the Fourier transform infrared spectrometry (FTIR) connected with TG. The kinetic parameters of the thermal cracking process of Xinjiang OSB at each of heating rate were determined by the Coats-Redfern model. The result show that the temperature intervals of DE volatilization stage and main reaction stage, the ((dw/dt) max and Tmax in thermal cracking process of Xinjiang OSB all increased with the increasing heating rate. While the heating rate has not obvious effect on the coke yield of Xinjiang OSB. Furthermore, the maximum absorbance of gaseous products and corresponding temperature became larger as the heating rate increases. The activation energy of this two stage both presented increasing trend with the rising heating rate, while the increasing content of that of DE volatilization stage was weaker compared to that of main reaction stage.

Initial Progress Rates as Related to Performance in a Personalized System of Instruction

ERIC Educational Resources Information Center

Henneberry, John K.

1976-01-01

Discusses research which explored the hypothesis that students who are fast starters in a personalized system of instruction psychology course would perform better and maintain faster course progress rates than slow starters. Findings indicate that students' starting pace is predictive of course performance and subsequent progress rates.…

Experimental Investigation of A Heat Pipe-Assisted Latent Heat Thermal Energy Storage System

NASA Astrophysics Data System (ADS)

Tiari, Saeed; Mahdavi, Mahboobe; Qiu, Songgang

2016-11-01

In the present work, different operation modes of a latent heat thermal energy storage system assisted by a heat pipe network were studied experimentally. Rubitherm RT55 enclosed by a vertical cylindrical container was used as the Phase Change Material (PCM). The embedded heat pipe network consisting of a primary heat pipe and an array of four secondary heat pipes were employed to transfer heat to the PCM. The primary heat pipe transports heat from the heat source to the heat sink. The secondary heat pipes transfer the extra heat from the heat source to PCM during charging process or retrieve thermal energy from PCM during discharging process. The effects of heat transfer fluid (HTF) flow rate and temperature on the thermal performance of the system were investigated for both charging and discharging processes. It was found that the HTF flow rate has a significant effect on the total charging time of the system. Increasing the HTF flow rate results in a remarkable increase in the system input thermal power. The results also showed that the discharging process is hardly affected by the HTF flow rate but HTF temperature plays an important role in both charging and discharging processes. The authors would like to acknowledge the financial supports by Temple University for the project.

Report of results of benchmarking survey of central heating operations at NASA centers and various corporations

NASA Technical Reports Server (NTRS)

Hoffman, Thomas R.

1995-01-01

In recent years, Total Quality Management has swept across the country. Many companies and the Government have started looking at every aspect on how business is done and how money is spent. The idea or goal is to provide a service that is better, faster and cheaper. The first step in this process is to document or measure the process or operation as it stands now. For Lewis Research Center, this report is the first step in the analysis of heating plant operations. This report establishes the original benchmark that can be referred to in the future. The report also provides a comparison to other organization's heating plants to help in the brainstorming of new ideas. The next step is to propose and implement changes that would meet the goals as mentioned above. After the changes have been implemented the measuring process starts over again. This provides for a continuous improvement process.

Graded meshes in bio-thermal problems with transmission-line modeling method.

PubMed

Milan, Hugo F M; Carvalho, Carlos A T; Maia, Alex S C; Gebremedhin, Kifle G

2014-10-01

In this study, the transmission-line modeling (TLM) applied to bio-thermal problems was improved by incorporating several novel computational techniques, which include application of graded meshes which resulted in 9 times faster in computational time and uses only a fraction (16%) of the computational resources used by regular meshes in analyzing heat flow through heterogeneous media. Graded meshes, unlike regular meshes, allow heat sources to be modeled in all segments of the mesh. A new boundary condition that considers thermal properties and thus resulting in a more realistic modeling of complex problems is introduced. Also, a new way of calculating an error parameter is introduced. The calculated temperatures between nodes were compared against the results obtained from the literature and agreed within less than 1% difference. It is reasonable, therefore, to conclude that the improved TLM model described herein has great potential in heat transfer of biological systems. Copyright © 2014 Elsevier Ltd. All rights reserved.

Physiological constraints to climate warming in fish follow principles of plastic floors and concrete ceilings.

PubMed

Sandblom, Erik; Clark, Timothy D; Gräns, Albin; Ekström, Andreas; Brijs, Jeroen; Sundström, L Fredrik; Odelström, Anne; Adill, Anders; Aho, Teija; Jutfelt, Fredrik

2016-05-17

Understanding the resilience of aquatic ectothermic animals to climate warming has been hindered by the absence of experimental systems experiencing warming across relevant timescales (for example, decades). Here, we examine European perch (Perca fluviatilis, L.) from the Biotest enclosure, a unique coastal ecosystem that maintains natural thermal fluctuations but has been warmed by 5-10 °C by a nuclear power plant for over three decades. We show that Biotest perch grow faster and display thermally compensated resting cardiorespiratory functions compared with reference perch living at natural temperatures in adjacent waters. However, maximum cardiorespiratory capacities and heat tolerance limits exhibit limited or no thermal compensation when compared with acutely heated reference perch. We propose that while basal energy requirements and resting cardiorespiratory functions (floors) are thermally plastic, maximum capacities and upper critical heat limits (ceilings) are much less flexible and thus will limit the adaptive capacity of fishes in a warming climate.

Microwave selective thermal development of latent fingerprints on porous surfaces: potentialities of the method and preliminary experimental results.

PubMed

Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina

2013-09-01

The thermal development of latent fingerprints on paper surfaces is a simple, safe, and chemicals-free method, based on the faster heating of the substrate underlying the print residue. Microwave heating is proposed for the first time for the development of latent fingerprints on cellulose-based substrate, in order to add to the thermal development mechanism the further characteristic of being able to heat the fingerprint residues to a different extent with respect to the substrate, due to the intrinsic difference in their dielectric properties. Numerical simulation was performed to confirm and highlight the selectivity of microwaves, and preliminary experimental results point out the great potentialities of this technique, which allowed developing both latent sebaceous-rich and latent eccrine-rich fingerprints on different porous surfaces, in less than 30 sec time with an applied output power of 500 W. Microwaves demonstrated more effectiveness in the development of eccrine-rich residues, aged up to 12 weeks. © 2013 American Academy of Forensic Sciences.

Synthetic-rubber extrusions form low cost roll-on solar collector

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

Smay, V.E.

1979-06-01

Synthetic rubber extrusions composed of ethylene propylene diene monomer (EPDM) have been developed in 4.4-inch-wide mats as solar absorbers that are light weight and simple to install. The mats, which come in rolls up to 600 ft long, have 6 small tubes alternating with thin webbing. EPDM has a lifespan of 30-50 yrs and maintains its flexibility within a temperature range of -80 to 375/sup 0/F. The mats are laid over rigid insulation and covered with glazing, detailed assembly instructions are provided. EPDM is not subject to corrosion and is not damaged by freezing water, a second EPDM extrusion ismore » used for glazed solar collectors. The efficiency of the design is attributed to the greater surface-to-mass ratio, permitting more heat collection, and the smaller mass of the synthetic rubber, which allows faster heat-up. The total cost for a complete, installed solar heating system of this type, including pumps, tanks, and plumbing, is about $12/ft/sup 2/.« less

An induction reactor for studying crude-oil oxidation relevant to in situ combustion.

PubMed

Bazargan, Mohammad; Lapene, Alexandre; Chen, Bo; Castanier, Louis M; Kovscek, Anthony R

2013-07-01

In a conventional ramped temperature oxidation kinetics cell experiment, an electrical furnace is used to ramp temperature at a prescribed rate. Thus, the heating rate of a kinetics cell experiment is limited by furnace performance to heating rates of about 0.5-3 °C/min. A new reactor has been designed to overcome this limit. It uses an induction heating method to ramp temperature. Induction heating is fast and easily controlled. The new reactor covers heating rates from 1 to 30 °C/min. This is the first time that the oxidation profiles of a crude oil are available over such a wide range of heating rate. The results from an induction reactor and a conventional kinetics cell at roughly 2 °C/min are compared to illustrate consistency between the two reactors. The results at low heating rate are the same as the conventional kinetics cell. As presented in the paper, the new reactor couples well with the isoconversional method for interpretation of reaction kinetics.