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Temperature Variation (temperature + variation)
Selected AbstractsThermal influence of urban groundwater recharge from stormwater infiltration basinsHYDROLOGICAL PROCESSES, Issue 12 2009Arnaud Foulquier Abstract Groundwater warming below cities has become a major environmental issue; but the effect of distinct local anthropogenic sources of heat on urban groundwater temperature distributions is still poorly documented. Our study addressed the local effect of stormwater infiltration on the thermal regime of urban groundwater by examining differences in water temperature beneath stormwater infiltration basins (SIB) and reference sites fed exclusively by direct infiltration of rainwater at the land surface. Stormwater infiltration dramatically increased the thermal amplitude of groundwater at event and season scales. Temperature variation at the scale of rainfall events reached 3 °C and was controlled by the interaction between runoff amount and difference in temperature between stormwater and groundwater. The annual amplitude of groundwater temperature was on average nine times higher below SIB (range: 0·9,8·6 °C) than at reference sites (range: 0,1·2 °C) and increased with catchment area of SIB. Elevated summer temperature of infiltrating stormwater (up to 21 °C) decreased oxygen solubility and stimulated microbial respiration in the soil and vadose zone, thereby lowering dissolved oxygen (DO) concentration in groundwater. The net effect of infiltration on average groundwater temperature depended upon the seasonal distribution of rainfall: groundwater below large SIB warmed up (+0·4 °C) when rainfall occurred predominantly during warm seasons. The thermal effect of stormwater infiltration strongly attenuated with increasing depth below the groundwater table indicating advective heat transport was restricted to the uppermost layers of groundwater. Moreover, excessive groundwater temperature variation at event and season scales can be attenuated by reducing the size of catchment areas drained by SIB and by promoting source control drainage systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Temperature variation of radiative recombination rate of electron-hole pairs responsible for defect photoluminescence in a-Si:HPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009C. Ogihara Abstract Lifetime distribution and characteristic lifetime of the defect photoluminescence (PL) in a-Si:H have been obtained by means of frequency resolved spectroscopy at various temperatures in the range of 10-200 K. Temperature variation of the radiative recombination rate has been obtained from the intensities and the characteristic lifetimes. The results obtained for the a-Si:H films as grown and after prolonged illumination have been compared. Thermal quenching of the defect PL becomes more significant after illumination. However the decrease of lifetime with raising temperature becomes less significant after illumination. Increase of the radiative recombination rate with increasing temperature, which is significantly observed above 100 K, becomes less significant after the illumination, indicating that the illumination causes the increase of the density of strongly localised tail states. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Winter temperature covariances in the middle and the lower troposphere over Europe and the North Atlantic OceanINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2001C.J. Lolis Abstract In this work, the variability and covariability of winter temperatures in the middle and the lower troposphere are studied over Europe and the North Atlantic Ocean. Temperature variations of the middle and the lower troposphere are examined in terms of (a) 500,700 hPa and 700,l000 hPa thickness and (b) air temperature on the isobaric surfaces of 500 hPa and 700 hPa. At first, factor analysis (FA) defined areas with characteristic temperature variability in each layer (and on each isobaric surface) and then, canonical correlation analysis (CCA) revealed areas in both layers (and on both isobaric surfaces) presenting common temperature variations. A temperature see-saw between N Europe and W Asia was revealed for both layers and isobaric surfaces implying that temperature changes in these areas are vertically spread. Another well-defined area, appearing in both analyses, is the area of the Labrador Sea and S Greenland. This region is also teleconnected to other regions, though not very clearly in every height. These temperature patterns are mainly attributed to the Eurasian (EU) and North Atlantic Oscillation (NAO) circulation patterns, which are responsible for large air mass exchanges in the area, being vertically extended in the middle and the lower troposphere. Copyright © 2001 Royal Meteorological Society [source] Temperature affects longevity and age-related locomotor and cognitive decay in the short-lived fish Nothobranchius furzeriAGING CELL, Issue 3 2006Dario R. Valenzano Summary Temperature variations are known to modulate aging and life-history traits in poikilotherms as different as worms, flies and fish. In invertebrates, temperature affects lifespan by modulating the slope of age-dependent acceleration in death rate, which is thought to reflect the rate of age-related damage accumulation. Here, we studied the effects of temperature on aging kinetics, aging-related behavioural deficits, and age-associated histological markers of senescence in the short-lived fish Nothobranchius furzeri. This species shows a maximum captive lifespan of only 3 months, which is tied with acceleration in growth and expression of aging biomarkers. These biological peculiarities make it a very convenient animal model for testing the effects of experimental manipulations on life-history traits in vertebrates. Here, we show that (i) lowering temperature from 25 °C to 22 °C increases both median and maximum lifespan; (ii) life extension is due to reduction in the slope of the age-dependent acceleration in death rate; (iii) lowering temperature from 25 °C to 22 °C retards the onset of age-related locomotor and learning deficits; and (iv) lowering temperature from 25 °C to 22 °C reduces the accumulation of the age-related marker lipofuscin. We conclude that lowering water temperature is a simple experimental manipulation which retards the rate of age-related damage accumulation in this short-lived species. [source] Functionally distinct haemoglobins of the cryopelagic Antarctic teleost Pagothenia borchgrevinkiJOURNAL OF FISH BIOLOGY, Issue 2000A. Riccio Pagothenia borchgrevinki, has a higher haemoglobin concentration than other Antarctic notothenioids and the high oxygen capacity may correlate with the relatively active mode of life of this fish. The fish has five haemoglobins (Hb C, Hb 0, Hb 1, Hb 2 and Hb 3) with Hb 1 accounting for 70,80% of the total, and Hb C being present in trace amounts. Hb 1 and Hb 2 are functionally similar in terms of Bohr and Root effects. Hb 3 has a weaker Bohr effect than Hb 1 and Hb 2, and the Root effect is similar to that of Hb 1. Hb 0 has a strong Bohr effect and the Root effect is enhanced to a larger extent by the physiological effectors chlorides and phosphates than that of the other components with the exception of Hb C. The heats of oxygenation are lower than those of temperate fish haemoglobins. Temperature variations may have a different effect on the functional properties of each haemoglobin, and chloride and phosphates may play an important role in the conformational change between the oxy and deoxy structures. The complete amino acid sequences of Hb 1 and Hb 0, as well as partial N-terminal or internal sequences of the other haemoglobins, have been established. The high multiplicity of functionally distinct haemoglobins indicates that P. borchgrevinki, has a specialized haemoglobin system. [source] Crystal Structure and Characterization of Pure and Ag-Doped (La1,xYx)2Ba2CaCu5Oz (0,x,0.5) SuperconductorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007Pramoda Kumar Nayak Pure and 5 wt% of Ag-doped (La1,xYx)2Ba2CaCu5Oz superconducting compounds for x=0,0.5 have been prepared. Analysis of X-ray diffraction patterns shows that the samples are essentially in the single-phase form and they could be refined using the P4/mmm space group in a tetragonal cell. The typical lattice parameters are found to be a=b=3.879 Å, c=11.646 Å for x=0 and a=b=3.856 Å, c=11.576 Å for x=0.5 samples. The detailed crystal structure parameters are presented. The average grain size values from scanning electron microscope images are found to be in the order of 1,3 ,m. Temperature variations of ac susceptibility and electrical resistivity have been measured. Superconducting transitions with diamagnetic Tc ranging from 60 to 75 K have been observed, with the maximum Tc for the x=0.25 sample. Ag-doped samples exhibit improved inter-granular coupling and homogeneous oxygenation. [source] Lifetime distribution of photoluminescence and radiative recombination rate of electron-hole pairs in a-Si:HPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Chisato Ogihara Abstract Temperature variations of radiative recombination rates of electron-hole pairs responsible for photoluminescence in a-Si:H films have been analysed from the intensity, I, and the characteristic value of the lifetime, ,, obtained from frequency resolved spectroscopy. In a defective a-Si:H film, the radiative recombinationrate increases with increasing temperature because of thermal excitation of the electrons and holes from the tail states to more ex-tended tail states. In the case of a high-quality a-Si:H film, the temperature variation of I,,1 is explained by contributions from regions in the vicinity of the defects and the regions not affected by the defects (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Evaluating Degradation with Fragment Formation of Prehospital Succinylcholine by Mass SpectrometryACADEMIC EMERGENCY MEDICINE, Issue 6 2010EMT-P, Mark A. Merlin DO Abstract Objectives:, Pharmaceutical manufacturers recommend refrigerating succinylcholine at a temperature range of 2,8°C. With widespread use of prehospital succinylcholine on ambulances without refrigeration, it is important to understand the stability of this drug. Using mass spectrometry, this study investigated the degradation of the succinylcholine compound before and after its exposure to ambulance cabin temperatures, while removing light exposure. A 10% degradation threshold was set as not appropriate for human use, in accordance with U.S. Food and Drug Administration guidelines. Methods:, The study used 17 vials of succinylcholine sealed with duct tape in light-resistant bags. The bags were placed in climate controlled compartments in two ambulances: one stationed in a garage and the other stationed outdoors. Mass spectrometry analysis was used to examine drug degradation at Time 0, the 14th day of the first month, and monthly from Time 0 to 7 months. Results:, The degradation products of succinyl monocholine (SMC) and choline are already present at Day 0. Ten percent degradation was achieved at approximately 90 days into the experiment. Temperature in the ambulance climate controlled compartment was 70°F, with a range from 56 to 89°F during the 6-month time period. Conclusions:, Identifiable breakdown fragments of succinylcholine have been identified using mass spectrometry with fresh drug upon receipt from the manufacturer. Ten percent degradation was not observed until approximately 90 days after being placed on ambulances. Temperature variations did not significantly contribute to degradation of succinylcholine, and it is safe for injection until approximately 90 days in similar climates. ACADEMIC EMERGENCY MEDICINE 2010; 17:631,637 © 2010 by the Society for Academic Emergency Medicine [source] The role of moisture cycling in the weathering of a quartz chlorite schist in a tropical environment: findings of a laboratory simulationEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2005Tony Wells Abstract Long-term weathering of a quartz chlorite schist via wetting and drying was studied under a simulated tropical climate. Cubic rock samples (15 mm × 15 mm × 15 mm) were cut from larger rocks and subjected to time-compressed climatic conditions simulating the tropical wet season climate at the Ranger Uranium Mine in the Northern Territory, Australia. Fragmentation, moisture content and moisture uptake rate were monitored over 5000 cycles of wetting and drying. To determine the impact of climatic variables, five climatic regimes were simulated, varying water application, temperature and drying. One of the climatic regimes reproduced observed temperature and moisture variability at the Ranger Uranium Mine, but over a compressed time scale. It is shown that wetting and drying is capable of weathering quartz chlorite schist with changes expected over a real time period of decades. While wetting and drying alone does produce changes to rock morphology, the incorporation of temperature variation further enhances weathering rates. Although little fragmentation occurred in experiments, significant changes to internal pore structure were observed, which could potentially enhance other weathering mechanisms. Moisture variability is shown to lead to higher weathering rates than are observed when samples are subjected only to leaching. Finally, experiments were conducted on two rock samples from the same source having only subtle differences in mineralogy. The samples exhibited quite different weathering rates leading to the conclusion that our knowledge of the role of rock type and composition in weathering is insufficient for the accurate determination of weathering rates. Copyright © 2005 John Wiley & Sons, Ltd. [source] CLINES IN CUTICULAR HYDROCARBONS IN TWO DROSOPHILA SPECIES WITH INDEPENDENT POPULATION HISTORIESEVOLUTION, Issue 6 2010Francesca D. Frentiu We took a comparative approach utilizing clines to investigate the extent to which natural selection may have shaped population divergence in cuticular hydrocarbons (CHCs) that are also under sexual selection in Drosophila. We detected the presence of CHC clines along a latitudinal gradient on the east coast of Australia in two fly species with independent phylogenetic and population histories, suggesting adaptation to shared abiotic factors. For both species, significant associations were detected between clinal variation in CHCs and temperature variation along the gradient, suggesting temperature maxima as a candidate abiotic factor shaping CHC variation among populations. However, rainfall and humidity correlated with CHC variation to differing extents in the two species, suggesting that response to these abiotic factors may vary in a species-specific manner. Our results suggest that natural selection, in addition to sexual selection, plays a significant role in structuring among-population variation in sexually selected traits in Drosophila. [source] POPULATION DIFFERENTIATION IN THE BEETLE TRIBOLIUM CASTANEUM.EVOLUTION, Issue 3 2007We used joint-scaling analyses in conjunction with rearing temperature variation to investigate the contributions of additive, non-additive, and environmental effects to genetic divergence and incipient speciation among 12 populations of the red flour beetle, Tribolium castaneum, with small levels of pairwise nuclear genetic divergence (0.033 < Nei's D < 0.125). For 15 population pairs we created a full spectrum of line crosses (two parental, two reciprocal F1's, four F2's, and eight backcrosses), reared them at multiple temperatures, and analyzed the numbers and developmental defects of offspring. We assayed a total of 219,388 offspring from 5147 families. Failed crosses occurred predominately in F2's, giving evidence of F2 breakdown within this species. In all cases where a significant model could be fit to the data on offspring number, we observed at least one type of digenic epistasis. We also found maternal and cytoplasmic effects to be common components of divergence among T. castaneum populations. In some cases, the most complex model tested (additive, dominance, epistatic, maternal, and cytoplasmic effects) did not provide a significant fit to the data, suggesting that linkage or higher order epistasis is involved in differentiation between some populations. For the limb deformity data, we observed significant genotype-by-environment interaction in most crosses and pure parent crosses tended to have fewer deformities than hybrid crosses. Complexity of genetic architecture was not correlated with either geographic distance or genetic distance. Our results support the view that genetic incompatibilities responsible for postzygotic isolation, an important component of speciation, may be a natural but serendipitous consequence of nonadditive genetic effects and structured populations. [source] Temperature-Responsive Substrates: Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture Substrates (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Mater. Abstract Thermoresponsive poly(N -isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non-covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels' physico-chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties. [source] Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Stephan Schmidt Abstract Thermoresponsive poly(N -isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non-covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels' physico-chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties. [source] Fatigue crack initiation detection by an infrared thermography methodFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2010D. WAGNER ABSTRACT In this paper, the study of the temperature variation during fatigue tests was carried out on different materials (steels and aluminium alloys). Tests were performed at ambient temperature using a piezoelectric fatigue system (20 kHz). The temperature field was measured on the surface of the specimen, by means of an infrared camera. Just at the beginning of the test, it was observed that the temperature increased, followed by a stabilization which corresponds to the balance between dissipated energy associated with microplasticity and the energy lost by convection and radiation at the specimen surface and by conduction inside the specimen. At the crack initiation, the surface temperature suddenly increases (whatever the localization of the initiation), which allows the determination of the number of cycles at the crack initiation and the number of cycles devoted to the fatigue crack propagation. In the gigacycle fatigue domain, more than 92% of the total life is devoted to the initiation of the crack. So, the study of the thermal dissipation during the test appears a promising method to improve the understanding of the damage and failure mechanism in fatigue and to determine the number of cycles at initiation. [source] Using patch studies to link mesoscale patterns of feeding and growth in larval fish to environmental variabilityFISHERIES OCEANOGRAPHY, Issue 4 2002John F. Dower We present results from a series of three patch studies designed to examine links between environmental variability and mesoscale patterns of feeding and growth of larval radiated shanny (Ulvaria subbifurcata). We examine the effects of variability in temperature, turbulence and prey concentration on both the mean (i.e. population level) and the variance (i.e. individual level) of larval feeding and growth rates among the three bays. Although both gut fullness and growth rates differ significantly between bays, our results show only weak environmental influences. When larvae are pooled across bays (i.e. treated as independent observations), environmental factors generally explain <4% of the variability in gut fullness. When treated as daily mean residuals, however, temperature accounts for 41% of the variability in mean gut fullness, while both temperature and prey concentration also explain significant portions of the variance in gut fullness (38 and 43%, respectively). Between-bay differences in larval growth rates are consistent with patterns of temperature variation but not with patterns of prey availability. Studies relying on tracking a single patch of larvae typically suffer from having too few observations to detect significant relationships between feeding or growth and environmental variables. By following three patches we collected a larger number of observations. However, as we encountered only a limited range of environmental conditions it remains difficult to adequately assess the role of environmental factors. In part, this problem stems from the inability of fisheries oceanographers to track the recent environmental history of individual larvae on the same fine scales currently employed to collect biological data (e.g. guts and otoliths) on individuals. [source] Stream temperature and the potential growth and survival of juvenile Oncorhynchus mykiss in a southern California creekFRESHWATER BIOLOGY, Issue 7 2007DAVID A. BOUGHTON Summary 1.,We asked whether an increase in food supply in the field would increase the ability of fish populations to withstand climate warming, as predicted by certain bioenergetic models and aquarium experiments. 2.,We subsidised the in situ food supply of wild juvenile steelhead (Oncorhynchus mykiss) in a small stream near the species' southern limit. High-quality food (10% of fish biomass per day) was added to the drift in eight in-stream enclosures along a naturally-occurring thermal gradient. 3.,The temperatures during the experiment were well below the upper thermal limit for the species (means of enclosures ranged from 15.1 to 16.5 °C). Food supplements had no discernible effect on survival, but raised mean (± SD) specific growth rate substantially, from 0.038 ± 0.135 in controls to 2.28 ± 0.51 in feeding treatments. Food supplements doubled the variation in growth among fish. 4.,The mean and variance of water temperature were correlated across the enclosures, and were therefore transformed into principal component scores T1 (which expressed the stream-wide correlation pattern) and T2 (which expressed local departures from the pattern). Even though T1 accounted for 96% of the variation in temperature mean and variance, it was not a significant predictor of fish growth. T2 was a significant predictor of growth. The predicted time to double body mass in an enclosure with a large T2 score (cool-variable) was half that in an enclosure with a low T2 score (warm-stable). 5.,Contrary to expectation, temperature effects were neutral, at least with respect to the main axis of variation among enclosures (cool-stable versus warm-variable). Along the orthogonal axis (cool-variable versus warm-stable), the effect was opposite from expectations, probably because of temperature variation. Subtle patterns of temperature heterogeneity in streams can be important to potential growth of O. mykiss. [source] What limits insect fecundity?FUNCTIONAL ECOLOGY, Issue 3 2008Body size-, oviposition in a butterfly, temperature-dependent egg maturation Summary 1Large female insects usually have high potential fecundity. Therefore selection should favour an increase in body size given that these females get opportunities to realize their potential advantage by maturing and laying more eggs. However, ectotherm physiology is strongly temperature-dependent, and activities are carried out sufficiently only within certain temperature ranges. Thus it remains unclear if the fecundity advantage of a large size is fully realized in natural environments, where thermal conditions are limiting. 2Insect fecundity might be limited by temperature at two levels; first eggs need to mature, and then the female needs time for strategic ovipositing of the egg. Since a female cannot foresee the number of oviposition opportunities that she will encounter on a given day, the optimal rate of egg maturation will be governed by trade-offs associated with egg- and time-limited oviposition. As females of different sizes will have different amounts of body reserves, size-dependent allocation trade-offs between the mother's condition and her egg production might be expected. 3In the temperate butterfly Pararge aegeria, the time and temperature dependence of oviposition and egg maturation, and the interrelatedness of these two processes were investigated in a series of laboratory experiments, allowing a decoupling of the time budgets for the respective processes. 4The results show that realized fecundity of this species can be limited by both the temperature dependence of egg maturation and oviposition under certain thermal regimes. Furthermore, rates of oviposition and egg maturation seemed to have regulatory effects upon each other. Early reproductive output was correlated with short life span, indicating a cost of reproduction. Finally, large females matured more eggs than small females when deprived of oviposition opportunities. Thus, the optimal allocation of resources to egg production seems dependent on female size. 5This study highlights the complexity of processes underlying rates of egg maturation and oviposition in ectotherms under natural conditions. We further discuss the importance of temperature variation for egg- vs. time-limited fecundity and the consequences for the evolution of female body size in insects. [source] On the variability of respiration in terrestrial ecosystems: moving beyond Q10GLOBAL CHANGE BIOLOGY, Issue 2 2006ERIC A. DAVIDSON Abstract Respiration, which is the second most important carbon flux in ecosystems following gross primary productivity, is typically represented in biogeochemical models by simple temperature dependence equations. These equations were established in the 19th century and have been modified very little since then. Recent applications of these equations to data on soil respiration have produced highly variable apparent temperature sensitivities. This paper searches for reasons for this variability, ranging from biochemical reactions to ecosystem-scale substrate supply. For a simple membrane-bound enzymatic system that follows Michaelis,Menten kinetics, the temperature sensitivities of maximum enzyme activity (Vmax) and the half-saturation constant that reflects the affinity of the enzyme for the substrate (Km) can cancel each other to produce no net temperature dependence of the enzyme. Alternatively, when diffusion of substrates covaries with temperature, then the combined temperature sensitivity can be higher than that of each individual process. We also present examples to show that soluble carbon substrate supply is likely to be important at scales ranging from transport across membranes, diffusion through soil water films, allocation to aboveground and belowground plant tissues, phenological patterns of carbon allocation and growth, and intersite differences in productivity. Robust models of soil respiration will require that the direct effects of substrate supply, temperature, and desiccation stress be separated from the indirect effects of temperature and soil water content on substrate diffusion and availability. We speculate that apparent Q10 values of respiration that are significantly above about 2.5 probably indicate that some unidentified process of substrate supply is confounded with observed temperature variation. [source] Fabrication of a Memory Chip by a Complete Self-Assembly Process Using State-of-the-Art Multilevel Cell (MLC) Technology,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2008Anirban Bandyopadhyay Abstract Using a two bit molecular switch, an ultra-dense memory chip has been built following a fully automated fabrication process. Well-ordered templates are grown naturally using a well-defined protocol of temperature variation. This template is so designed that molecules are adsorbed selectively only into particular sites whenever they are bombarded on the template through an e-beam evaporator for a particular time. The technique is a generalized protocol that has been used to grow atomic-scale templates by proper tuning of basic global parameters like temperature and evaporation time. Tuning of the basic template parameters is also demonstrated here, and has been used to scale down parameter values following the same route. Tuning the junction profile should allow selective adsorption of more complicated multi-level switches in future. Therefore, a fairly simple technology has been established that addresses one of the most fundamental issues of continuous miniaturization, i.e., simultaneous automated growth of thousands of atomically precise single molecular devices. [source] Heat transportation by oscillatory flow with steady flow componentHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2006Akira Inukai Abstract This paper deals with heat transportation by an oscillatory flow composed of a sinusoidal oscillatory flow superimposed with a steady flow. Velocity and temperature fields, heat transportation rate, work rate, and heat transportation efficiency were investigated through numerical analysis. Results obtained elucidated that (1) the phase difference between velocity and temperature variation remained the same as that of the sinusoidal reciprocal flow without the use of a steady flow component. (2) In the upstream direction heat was mainly transported by the steady flow component and in the downstream direction transportation was mainly performed by the oscillatory flow component. (3) The heat transportation rate of the present oscillatory flow composed of both steady and oscillatory flow components was less than the arithmetic sum of the rates produced by the steady flow and the sinusoidal oscillatory flow. (4) The heat transportation rate was increased immensely by superimposing the steady flow on the sinusoidal oscillatory flow. (5) Conversely, work done by the present oscillatory flow increased only slightly. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 482,500, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20130 [source] Effect of the plate thermal resistance on the heat transfer performance of a corrugated thin plate heat exchangerHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2006Hiroshi Iwai Abstract Two-dimensional conjugate conduction/convection numerical simulations were carried out for flow and thermal fields in a unit model of a counter-flow-type corrugated thin plate heat exchanger core. The effects of the thermal resistance of the solid plate, namely the variation of the plate thickness and the difference of the plate material, on the heat exchanger performance were examined in the Reynolds number range of 100 Simulation of heat transfer in the cool storage unit of a liquid,air energy storage systemHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2002Hidefumi Araki Abstract An energy storage system that stores energy in the form of liquid air was studied. In this system, the cool storage unit was the most important unit. From the viewpoint of safety and economy, it was most promising to store the cold energy as the sensitive heat of a solid such as pebbles or concrete. A simulator was developed to predict temperature variations of the solid cool storage unit. The simulator calculated unsteady heat transfer between a supercritical gas flow and the solid material. Comparison of calculated and experimental results showed that the temperature variation of the metal cool storage medium was accurate within 11%. The calculated results showed for the concrete cool storage unit that a smaller quantity of medium was required with a smaller pitch of the tube. The minimum quantity of concrete calculated at the smallest pitch was three times that of concrete, which was simply estimated from the heat capacity of concrete and air. The volume required for concrete cool storage was less than 1/100 that of reservoirs for a pumped-hydro power station having a vertical drop of 500 m. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(4): 284,296, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10035 [source] Thermal influence of urban groundwater recharge from stormwater infiltration basinsHYDROLOGICAL PROCESSES, Issue 12 2009Arnaud Foulquier Abstract Groundwater warming below cities has become a major environmental issue; but the effect of distinct local anthropogenic sources of heat on urban groundwater temperature distributions is still poorly documented. Our study addressed the local effect of stormwater infiltration on the thermal regime of urban groundwater by examining differences in water temperature beneath stormwater infiltration basins (SIB) and reference sites fed exclusively by direct infiltration of rainwater at the land surface. Stormwater infiltration dramatically increased the thermal amplitude of groundwater at event and season scales. Temperature variation at the scale of rainfall events reached 3 °C and was controlled by the interaction between runoff amount and difference in temperature between stormwater and groundwater. The annual amplitude of groundwater temperature was on average nine times higher below SIB (range: 0·9,8·6 °C) than at reference sites (range: 0,1·2 °C) and increased with catchment area of SIB. Elevated summer temperature of infiltrating stormwater (up to 21 °C) decreased oxygen solubility and stimulated microbial respiration in the soil and vadose zone, thereby lowering dissolved oxygen (DO) concentration in groundwater. The net effect of infiltration on average groundwater temperature depended upon the seasonal distribution of rainfall: groundwater below large SIB warmed up (+0·4 °C) when rainfall occurred predominantly during warm seasons. The thermal effect of stormwater infiltration strongly attenuated with increasing depth below the groundwater table indicating advective heat transport was restricted to the uppermost layers of groundwater. Moreover, excessive groundwater temperature variation at event and season scales can be attenuated by reducing the size of catchment areas drained by SIB and by promoting source control drainage systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hydrogeologic controls on summer stream temperatures in the McKenzie River basin, OregonHYDROLOGICAL PROCESSES, Issue 24 2007Christina Tague Abstract Stream temperature is a complex function of energy inputs including solar radiation and latent and sensible heat transfer. In streams where groundwater inputs are significant, energy input through advection can also be an important control on stream temperature. For an individual stream reach, models of stream temperature can take advantage of direct measurement or estimation of these energy inputs for a given river channel environment. Understanding spatial patterns of stream temperature at a landscape scale requires predicting how this environment varies through space, and under different atmospheric conditions. At the landscape scale, air temperature is often used as a surrogate for the dominant controls on stream temperature. In this study we show that, in regions where groundwater inputs are key controls and the degree of groundwater input varies in space, air temperature alone is unlikely to explain within-landscape stream temperature patterns. We illustrate how a geologic template can offer insight into landscape-scale patterns of stream temperature and its predictability from air temperature relationships. We focus on variation in stream temperature within headwater streams within the McKenzie River basin in western Oregon. In this region, as in other areas of the Pacific Northwest, fish sensitivity to summer stream temperatures continues to be a pressing environmental issue. We show that, within the McKenzie, streams which are sourced from deeper groundwater reservoirs versus shallow subsurface flow systems have distinct summer temperature regimes. Groundwater streams are colder, less variable and less sensitive to air temperature variation. We use these results from the western Oregon Cascade hydroclimatic regime to illustrate a conceptual framework for developing regional-scale indicators of stream temperature variation that considers the underlying geologic controls on spatial variation, and the relative roles played by energy and water inputs. Copyright © 2007 John Wiley & Sons, Ltd. [source] Modelling snowpack surface temperature in the Canadian Prairies using simplified heat flow modelsHYDROLOGICAL PROCESSES, Issue 18 2005Purushottam Raj Singh Abstract Three practical schemes for computing the snow surface temperature Ts, i.e. the force,restore method (FRM), the surface conductance method (SCM), and the Kondo and Yamazaki method (KYM), were assessed with respect to Ts retrieved from cloud-free, NOAA-AVHRR satellite data for three land-cover types of the Paddle River basin of central Alberta. In terms of R2, the mean Ts, the t -test and F -test, the FRM generally simulated more accurate Ts than the SCM and KYM. The bias in simulated Ts is usually within several degrees Celsius of the NOAA-AVHRR Ts for both the calibration and validation periods, but larger errors are encountered occasionally, especially when Ts is substantially above 0 °C. Results show that the simulated Ts of the FRM is more consistent than that of the SCM, which in turn was more consistent than that of the KYM. This is partly because the FRM considers two aspects of heat conduction into snow, a stationary-mean diurnal (sinusoidal) temperature variation at the surface coupled to a near steady-state ground heat flux, whereas the SCM assumes a near steady-state, simple heat conduction, and other simplifying assumptions, and the KYM does not balance the snowpack heat fluxes by assuming the snowpack having a vertical temperature profile that is linear. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Effect of Dopants on the Dielectric Properties of Ba(B,1/2Ta1/2)O3 (B,=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) Microwave CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2009Lamrat Abdul Khalam Low-loss dielectric ceramics based on Ba(B,1/2Ta1/2)O3 (B,=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) complex perovskites have been prepared by the solid-state ceramic route. The dielectric properties (,r, Qu, and ,f) of the ceramics have been measured in the frequency range 4,6 GHz by the resonance method. The resonators have a relatively high dielectric constant and high quality factor. Most of the compounds have a low coefficient of temperature variation of the resonant frequencies. The microwave dielectric properties have been improved by the addition of dopants and by solid solution formation. The solid solution Ba[(Y1,xPrx)1/2Ta1/2]O3 has x=0.15, with ,r=33.2, Qu×f=51,500 GHz, and ,f,0. The microwave dielectric properties of Ba(B,1/2Ta1/2)O3 ceramics are found to depend on the tolerance factor (t), ionic radius, and ionization energy. [source] Humidity parameters from temperature: test of a simple methodology for European conditionsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2008Yvonne Andersson-Sköld Abstract Atmospheric water content is important for local and regional climate, and for chemical processes of soluble and solute species in the atmosphere. Further, vapour pressure deficit (D) is one of the key controls on the opening of stomata in plants and is thus an important force for evapotransporation, plant respiration and biomass production and for the uptake of harmful pollutants such as ozone through the stomata. Most meteorological stations typically measure both temperature and relative humidity (RH). However, even if recorded at finer time resolution, it is usually the daily or often monthly means of RH which are published in climate reports. Unfortunately, such data cannot be used to obtain the changes in RH or vapour pressure deficit over the day, as this depends strongly on the diurnal temperature variation during the day and not upon the mean temperature. Although RH typically changes significantly over the day, the ambient vapour pressure is often remarkably constant. Here a simple method to estimate diurnal vapour pressure is evaluated, based upon an assumed constant vapour pressure, and that recorded minimum temperatures approximate dew-point temperatures. With a knowledge of only temperature, we will show that day to day estimates of vapour pressure, humidity and especially D, can be made with reasonable accuracy. This methodology is tested using meteorological data from 32 sites covering a range of locations in Europe. Such a simple methodology may be used to extract approximate diurnal curves of vapour pressures from published meteorological data which contains only minimum temperatures for each day, or where humidity data are not available. Copyright © 2007 Royal Meteorological Society [source] Characterization of granular phase changing composites for thermal energy storage using the T-history methodINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2010M. A. Rady Abstract The present article reports on the characterization of granular phase changing composites using the T-history method. Further modifications and improvements of the method are employed to handle granular materials undergoing phase change over a temperature range. The accuracy of the T-history method is shown to be limited by the assumption of temperature-independent specific heats and the difficulty of determining the limits of solid and liquid phases. The concept of enthalpy and its relationship with temperature has been employed in the analysis to overcome these difficulties. Enthalpy,temperature and apparent heat capacity curves similar to those obtained using DSC have been developed. These characteristic curves are necessary for accurate design, modeling, and optimization of latent heat thermal energy storage systems. Experiments have been also carried out to measure the transient temperature distribution inside a cylindrical packed bed using phase changing granulates. Analysis of temperature variation along the bed shows good agreement with the measured phase change characteristics. Copyright © 2009 John Wiley & Sons, Ltd. [source] Second-law analysis and optimization of microchannel flows subjected to different thermal boundary conditionsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2005Kuan Chen Abstract Entropy generation and transfer in microchannel flows were calculated and analyzed for different thermal boundary conditions. Due to the small flow cross-sectional area, fluid temperature variation in the lateral direction was neglected and a laterally lumped model was developed and used in the first- and second-law analyses. Since the Peclet numbers of microchannel flows are typically low, heat conduction in the flow direction was taken into consideration. Computed fluid temperature and entropy generation rate were cast into dimensionless forms, thus can be applied to different fluids and channels of different sizes and configurations. Local entropy generation rate was found to be only dependent upon the temperature gradient in the flow direction. The optimization results of microchannel flows exchanging heat with their surroundings indicate the optimal fluid temperature distribution is a linear one. Copyright © 2004 John Wiley & Sons, Ltd. [source] Investigation of the temperature oscillations in the cylinder walls of a diesel engine with special reference to the limited cooled caseINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2004C. D. Rakopoulos Abstract This work investigates the interesting phenomenon of the temperature (cyclic) oscillations in the combustion chamber walls of a diesel engine. For this purpose, a comprehensive simulation code of the thermodynamic cycle of the engine is developed taking into account both the closed and the open parts of it. The energy and state equations are applied, with appropriate combustion, gas heat transfer, and mass exchange with the atmosphere sub-models, to yield cylinder pressure, local temperatures and heat release histories as well as various performance parameters of the engine. The model is appropriately coupled to a wall periodic conduction model, which uses the gas temperature variation as boundary condition throughout the engine cycle after being treated by Fourier analysis techniques. It is calibrated against measurements, at various load and speed conditions, from an experimental work carried out on a direct injection (DI), naturally aspirated, four-stroke, diesel engine located at the authors' laboratory, which has been reported in detail previously. After gaining confidence into the predictive capabilities of the model, it is used to investigate the phenomenon further, thus providing insight into many interesting aspects of transient engine heat transfer, as far as the influence that engine wall material properties have on the values of cyclic temperature swings. These swings can take prohibitive values causing high wall thermal fatigue, when materials of specific technological interest such as thermal insulators (ceramics) are used, and may lead to deterioration in engine performance. Copyright © 2004 John Wiley & Sons, Ltd. [source]
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