Direct Thermal Effects Research Articles

Maternal thermal effect on diapause inTrichogrammaspecies (Hymenoptera: Trichogrammatidae)

AbstractBoth direct thermal and maternal photoperiodic effects on diapause induction have been thoroughly investigated in many insect species, while maternal thermal effects have been infrequently studied. We studied the effect of temperature during development of maternal generation on the proportion of diapausing progeny in four species of the genusTrichogrammaWestw., minute egg parasitoids, widely used for biological control of lepidopteran pests. The maternal generations were reared at day lengths of 12 and 18 h and temperatures of 17, 20, 25 and 30°C, and their progeny developed under day length of 12 h and temperatures of 13 and 14°C. InT. evanescensandT. piceum, the proportion of diapausing progeny decreased with increasing temperature under all tested photoperiods and thermal regimes of progeny development; the high temperature of 30°C totally averted diapause of progeny. InT. buesiandT. principium,low temperatures of 17 and 20°C resulted in relatively high proportion of diapausing progeny only when the maternal generation developed under short‐day conditions. The threshold of the maternal thermal response varied from 17–18 to 22–23°C. Under field conditions,Trichogrammafemales are exposed to such high temperatures only during summer, when diapause in their progeny is in any case prevented by the maternal photoperiodic response and by the thermal response of the larvae. We conclude that the maternal thermal effect on diapause induction, although to a different extent, is inherent toTrichogrammaspecies but, at least as suggested by laboratory experiments, it does not play any role in the regulation of seasonal development under natural conditions. However, during mass rearing ofTrichogrammawasps, it should be taken into account that high temperature, even when combined with short photoperiod, can avert diapause in the next generation.

Climate change, extinction risks, and reproduction of terrestrial vertebrates.

This review includes a broad, but superficial, summary of our understanding about current and future climate changes, the predictions about how these changes will likely affect the risks of extinction of organisms, and how current climate changes are already affecting reproduction in terrestrial vertebrates. Many organisms have become extinct in the last century, but habitat destruction, disease and man-made factors other than climate change have been implicated as the causal factor in almost all of these. Reproduction is certain to be negatively impacted in all vertebrate groups for a variety of reasons, such as direct thermal and hydric effects on mortality of embryos, mismatches between optimal availability of food supplies, frequently determined by temperature, and reproductive capacities, sometimes determined by rigid factors such as photoperiod, and disappearance of appropriate foraging opportunities, such as melting sea ice. The numbers of studies documenting correlations between climate changes and biological phenomena are rapidly increasing, but more direct information about the consequences of these changes for species survival and ecosystem health is needed than is currently available.

Tumor Selective Hyperthermia Induced by Short-Wave Capacitively-Coupled RF Electric-Fields

There is a renewed interest in developing high-intensity short wave capacitively-coupled radiofrequency (RF) electric-fields for nanoparticle-mediated tumor-targeted hyperthermia. However, the direct thermal effects of such high-intensity electric-fields (13.56 MHZ, 600 W) on normal and tumor tissues are not completely understood. In this study, we investigate the heating behavior and dielectric properties of normal mouse tissues and orthotopically-implanted human hepatocellular and pancreatic carcinoma xenografts. We note tumor-selective hyperthermia (relative to normal mouse tissues) in implanted xenografts that can be explained on the basis of differential dielectric properties. Furthermore, we demonstrate that repeated RF exposure of tumor-bearing mice can result in significant anti-tumor effects compared to control groups without detectable harm to normal mouse tissues.

Direct and indirect thermal expansion effects in turbulent premixed flames

AbstractThe thermal expansion induced by the exothermic chemical reactions taking place in a turbulent reactive flow affects the velocity field so strongly that the large-scale velocity fluctuations as well as the small-scale velocity gradients can be governed by chemistry rather than by turbulence. Moreover, thermal expansion is well known to be responsible for counter-gradient turbulent diffusion and flame-generated turbulence phenomena. In the present study, by making use of an original splitting procedure applied to the velocity field, we establish the occurrence of two distinct thermal expansion effects in the flamelet regime of turbulent premixed combustion. The first is referred to as the direct thermal expansion effect. It is associated with a local flamelet crossing contribution as previously considered in early analyses of turbulent transport in premixed flames. The second, denoted herein as the indirect thermal expansion effect, is an outcome of the turbulent wrinkling processes that increases the flame surface area. Based on a splitting procedure applied to the velocity field, the respective influences of the two effects are identified and analysed. Furthermore, the theoretical analysis shows that the thermal expansion induced through the local flames can be treated separately in the usual continuity and momentum equations. This description of the turbulent reactive velocity field, leads also to relate all of the usual turbulent quantities to the reactive scalar field. Finally, algebraic closures for the turbulent transport terms of mass and momentum are proposed and successfully validated through comparison with direct numerical simulation data.

Direct and indirect thermal expansion effects in turbulent premixed flames

The thermal expansion induced by the exothermic chemical reactions taking place in a turbulent reactive flow affects the velocity field so strongly that the large-scale velocity fluctuations as well as the small-scale velocity gradients can be governed by chemistry rather than by turbulence. Moreover, thermal expansion is well known to be responsible for counter-gradient turbulent diffusion and flame-generated turbulence phenomena. In the present study, by making use of an original splitting procedure applied to the velocity field, we establish the occurrence of two distinct thermal expansion effects in the flamelet regime of turbulent premixed combustion. The first is referred to as the direct thermal expansion effect. It is associated with a local flamelet crossing contribution as previously considered in early analyses of turbulent transport in premixed flames. The second, denoted herein as the indirect thermal expansion effect, is an outcome of the turbulent wrinkling processes that increases the flame surface area. Based on a splitting procedure applied to the velocity field, the respective influences of the two effects are identified and analysed. Furthermore, the theoretical analysis shows that the thermal expansion induced through the local flames can be treated separately in the usual continuity and momentum equations. This description of the turbulent reactive velocity field, leads also to relate all of the usual turbulent quantities to the reactive scalar field. Finally, algebraic closures for the turbulent transport terms of mass and momentum are proposed and successfully validated through comparison with direct numerical simulation data.

Thermal responses of juvenile squaretail mullet ( Liza vaigiensis) and juvenile crescent terapon ( Terapon jarbua) acclimated at near-lethal temperatures, and the implications for climate change

The negative effects of climate alteration on coral reef fishes receive ever increasing attention; however, implications of rising sea temperatures on fishes inhabiting marine nursery environments are poorly understood. We used critical thermal methodology to quantify critical thermal maxima (CTmaxima) of juvenile squaretail mullet ( Liza vaigiensis) and juvenile crescent terapon ( Terapon jarbua) captured from shallow seagrass nursery areas around Hoga Island, southeast Sulawesi, Indonesia. We tested the hypothesis that these distantly related fishes, when acclimated to cycling temperatures, would display higher CTmaxima than groups acclimated at constant temperatures. Groups of mullet acclimated to a constant temperature of 37 °C and temperature cycles of 35 to 39 °C or 37 to 41 °C displayed statistically similar mean CTmaxima of 44.7, 44.4 and 44.8 °C, respectively. Likewise, terapon acclimated at temperature cycles of 37 to 40 °C did not display a higher CTmaxima than fish acclimated at a constant temperature of 37 °C, with both acclimation groups' mean CTmaxima equal to 43.8 °C. Acclimation to higher cycling temperatures did not result in significant upper temperature tolerance acquisition for either species; however, mullet values were significantly higher than those seen in terapon ( P < 0.0001). These data suggest that mullet and terapon will not suffer direct thermal effects should shallow nursery temperature increases be marginally higher than 1–2 °C above ~ 27 °C, and they provide evidence that the upper thermal tolerance of fishes inhabiting shallow seagrass and mangrove areas can approach the biokinetic limits for vertebrate life. Tropical marine fishes inhabiting fringing nursery environments may have the upper thermal tolerance necessary to endure substantial increases in sea temperatures.

Predicting the effects of climate change on reproductive fitness of an endangered montane lizard, Eulamprus leuraensis (Scincidae)

A shift in climatic conditions may directly modify critical organismal traits (such as reproductive output and offspring phenotypes), and experimental studies to document such direct effects thus may clarify the impacts of climate change on the species involved. The endangered Blue Mountains Water Skink (Eulamprus leuraensis) exhibits several traits predicted to imperil it under climate change: ectothermy, low reproductive output, specialisation to a restricted habitat type, montane endemicity, and a small geographic range. Congeneric species exhibit temperature-dependent sex determination, increasing potential sensitivity to climate change. We maintained wild-caught female lizards throughout pregnancy under thermal conditions simulating a shift in basking-time availability (3 vs 7 h/day) as might occur under climate change. Females with longer basking opportunities per day gave birth 2 weeks earlier, to slightly smaller offspring, that grew much faster in the first few weeks of life. Importantly, offspring sex ratios were not affected by maternal thermal regimes. Hence, some traits (e.g., offspring size, growth rates, dates of birth) are sensitive to ambient thermal conditions whereas other traits (e.g., offspring sex ratio and sprint speed) are not. On balance, the greatest threat to population persistence for E. leuraensis under climate change is likely to involve indirect effects mediated via habitat degradation (especially, drying-out of the hanging swamps) rather than direct thermal effects on lizard reproductive output or offspring phenotypes.

Dynamical heating of the polar summer mesopause induced by solar proton events

The observed heating of the polar summer mesopause during and after a solar proton event (SPE) is interpreted as a large‐scale dynamical response to the temporary diabatic cooling in the lower mesosphere above the summer pole that results from the temporary ozone depletion during an SPE. Our method is based on time slice sensitivity experiments performed with a mechanistic general circulation model. The model response shows that according to the gradient wind balance, the polar lower mesospheric cooling induces an anomalous eastward wind component. As a result, the drag exerted by eastward propagating gravity waves (GWs) shifts to lower altitudes in tandem with a balancing downward shift of the residual circulation. Around the extratropical summer mesopause, this is accompanied by an anomalous large‐scale dynamic heating which qualitatively explains the positive temperature response in this region. A quantitative inspection of the zonal momentum and sensible heat budgets reveals that the GW drag response is partly compensated by a downshift of planetary Rossby waves and that about two thirds of the anomalous large‐scale dynamic heating around the mesopause is balanced by changes of the direct thermal effects due to GWs, diffusion, and dissipation.

Giant impact stratification of the Martian core

We investigate the direct thermal effects of giant impacts on the Martian core and its dynamo. Shock wave heating of Mars is calculated in terms of the impact velocity and the final basin size. Although much of the shock wave heat is deposited in the mantle, shock heating from a giant impact produces non‐uniform temperatures in the core, leading to an overturn event and stable thermal stratification in the liquid core. Numerical dynamos with core heating from polar and equatorial impacts show that the overturn and stratification quickly destroys a pre‐existing core dynamo, within ten thousand years. Energy considerations reveal that both the stratification and the time required for removal of the stratification increase with impact size. Our calculations indicate that several tens to over one hundred million years are required for removal of core stratification following a giant impact.

Resolution of low voltage electrical injury induced psychosis with olanzapine

Background: The number of electrical injuries are rising in proportion to the increased use of electricity in both domestic and industrial sectors. There are multiple ways in which electricity can cause tissue damage, which can be due to direct effects, electroporation and thermal effects. However, these mechanisms fail to explain the enigmatous occurrences of diffuse and delayed neurological and psychological manifestations, especially those remote to the theoretical current pathway and in absence of any gross neurological abnormalities. Immediate neuropsychological sequelae have been well reported in the literature in the form of transient anxiety, emotional instability and memory disturbances. Among psychiatric manifestations, neurotic disorders like post-traumatic stress disorder, conversion and adjustment disorders have been appreciated many a times as a frequent accompaniment of these injuries. Occasional reports of occurrence of mania have also been recorded.Case study: This study reports a case of schizophrenia like illness following a low voltage electrical injury. A discussion regarding the ways in which electrical injury and schizophrenia like illness could be related has been put forth. A brief review of the literature regarding the occurrence of psychiatric disorders in such injuries is also presented.

Response of a rocky intertidal ecosystem engineer and community dominant to climate change

To evaluate how climate change might impact a competitively dominant ecological engineer, we analysed the growth response of the mussel Mytilus californianus to climate patterns [El Niño-Southern Oscillation, Pacific Decadal Oscillation (PDO)]. Mussels grew faster during warmer climatic events. Growth was initially faster on a more productive cape compared to a less productive cape. Growth rates at the two capes merged in 2002, coincidentally with a several year-long shift from warm to cool PDO conditions. To determine the mechanism underlying this response, we examined growth responses to intertidal sea and air temperatures, phytoplankton, sea level and tide height. Together, water temperature (32%) and food (12.5%) explained 44.5% of the variance in mussel growth; contributions of other factors were not significant. In turn, water temperature and food respond to climate-driven variation in upwelling and other, unknown factors. Understanding responses of ecosystem engineers to climate change will require knowing direct thermal effects and indirect effects of factors altered by temperature change.

High-power low-frequency ultrasound: A review of tissue dissection and ablation in medicine and surgery

Abstract High-power low-frequency ultrasound in the range 20–60 kHz has wide ranging clinical applications in surgical and medical instruments for biological tissue cutting, ablation or fragmentation, and removal. Despite widespread clinical application and common device operating characteristics, there is an incomplete understanding of the mechanism of tissue failure, removal and damage. The relative contribution of cavitation, direct mechanical impact and thermal effects to each process for specific tissue types remains unclear. Different and distinct mechanisms and rates of tissue removal are observed for interaction with soft and hard tissue types. Device operating parameters known to affect the interaction include frequency, peak–peak tip amplitude, suction and application time. To date, there has been little analysis of the effect of variations in, and interactions of, these parameters on tissue removal and damage for individual biological tissue types. Potential controllable damage mechanisms occurring in tissues include alteration in global biomechanical properties, histomorphological changes, protein denaturation and tissue necrosis. This paper presents a critical review of the literature on the clinical application, mechanism of tissue interaction, removal and residual tissue damage. It describes known mechanisms for distinct tissue types.

Ultrafast all-optical control of the magnetization in magnetic dielectrics

The purpose of this review is to summarize the recent progress on laser-induced magnetization dynamics in magnetic dielectrics. Due to the slow phonon-magnon interaction in these materials, direct thermal effects of the laser excitation can only be seen on the time scale of almost a nanosecond and thus are clearly distinguished from the ultrafast nonthermal effects. However, laser pulses are shown to indirectly modify the magnetic anisotropy in rare-earth orthoferrites via the crystal field, and to bring about spin reorientation within a few picoseconds. More interesting, however, are the direct nonthermal effects of light on spin systems. We demonstrate coherent optical control of the magnetization in ferrimagnetic garnet films on a femtosecond time scale through a combination of two different ultrafast and nonthermal photomagnetic effects and by employing multiple pump pulses. Linearly polarized laser pulses are shown to create a long-lived modification of the magnetocrystalline anisotropy via optically induced electron transfer between nonequivalent ion sites. In addition, circularly polarized pulses are shown to act as strong transient magnetic field pulses originating from the nonabsorptive inverse Faraday effect. An all-optical scheme of excitation and detection of different antiferromagnetic resonance modes with frequencies of up to 500GHz will be discussed as well. The reported effects open new and exciting possibilities for ultrafast manipulation of spins by light and provide new insight into the physics of magnetism on ultrafast time scales.

The Roles of Exercise-Induced Immune System Disturbances in the Pathology of Heat Stroke

Heat stroke is a life-threatening condition that can be fatal if not appropriately managed. Although heat stroke has been recognised as a medical condition for centuries, a universally accepted definition of heat stroke is lacking and the pathology of heat stroke is not fully understood. Information derived from autopsy reports and the clinical presentation of patients with heat stroke indicates that hyperthermia, septicaemia, central nervous system impairment and cardiovascular failure play important roles in the pathology of heat stroke. The current models of heat stroke advocate that heat stroke is triggered by hyperthermia but is driven by endotoxaemia. Endotoxaemia triggers the systemic inflammatory response, which can lead to systemic coagulation and haemorrhage, necrosis, cell death and multi-organ failure. However, the current heat stroke models cannot fully explain the discrepancies in high core temperature (Tc) as a trigger of heat stroke within and between individuals. Research on the concept of critical Tc as a limitation to endurance exercise implies that a high Tc may function as a signal to trigger the protective mechanisms against heat stroke. Athletes undergoing a period of intense training are subjected to a variety of immune and gastrointestinal (GI) disturbances. The immune disturbances include the suppression of immune cells and their functions, suppression of cell-mediated immunity, translocation of lipopolysaccharide (LPS), suppression of anti-LPS antibodies, increased macrophage activity due to muscle tissue damage, and increased concentration of circulating inflammatory and pyrogenic cytokines. Common symptoms of exercise-induced GI disturbances include diarrhoea, vomiting, gastrointestinal bleeding, and cramps, which may increase gut-related LPS translocation. This article discusses the current evidence that supports the argument that these exercise-induced immune and GI disturbances may contribute to the development of endotoxaemia and heat stroke. When endotoxaemia can be tolerated or prevented, continuing exercise and heat exposure will elevate Tc to a higher level (>42 degrees C), where heat stroke may occur through the direct thermal effects of heat on organ tissues and cells. We also discuss the evidence suggesting that heat stroke may occur through endotoxaemia (heat sepsis), the primary pathway of heat stroke, or hyperthermia, the secondary pathway of heat stroke. The existence of these two pathways of heat stroke and the contribution of exercise-induced immune and GI disturbances in the primary pathway of heat stroke are illustrated in the dual pathway model of heat stroke. This model of heat stroke suggests that prolonged intense exercise suppresses anti-LPS mechanisms, and promotes inflammatory and pyrogenic activities in the pathway of heat stroke.

Machine tool errors caused by optical linear encoders

Position measurement in machine tools is usually carried out through rotary or linear encoders. Quite often, it is considered that part dimensional errors are only due to direct strain, thermal or vibration effects in the machine tool structure. There is, however, another important source of error: the encoder itself. This paper is intended to recognize, classify and determine the value of the different kinds of error in optical linear encoders: strain and displacement errors, thermal errors and errors caused by vibrations. The error identification will also permit a better understanding of some of the limitations that appear in the use of these devices.

Effect of western U.S. snow cover on climate

AbstractThe purpose of this study is to identify characterize and quantify local, regional and remote effects of snow cover on western U. S. climate and water resources. An ensemble of predictability and sensitivity studies was made with the U.S. National Center for Atmospheric Research (NCAR) Community Climate Model, version 3 (CCM3) to investigate the relative roles of snow-cover anomalies and initial atmospheric states in the subsequent accumulation and ablation seasons. The suite of model experiments focuses on the direct effect of snow on regional climate anomalies and ultimately will be used to examine the lagged effect of anomalous snow cover on the climate. The set of ensemble simulations presented here looks at the climate-system response to anomalously high and low snow cover at the start of the ablation season over the western U.S.A. These current results suggest that the initial state of snow cover is more important than the initial state of the atmosphere or of sea-surface temperatures because of direct thermal effects on the surface and subsequent indirect, dynamical effects on the atmospheric circulation.

Thermomechanical analysis of failure of metal field emitters

An analysis of the thermomechanics of metal (chiefly molybdenum) field emitters under normal operating conditions is given. The focus is on various ‘‘intrinsic’’ phenomena and the possibilities of triggering catastrophic breakdown. The heating is found to be predominantly Nottingham in origin (as opposed to ohmic) and is not appreciable unless the currents are well beyond the normal operating regime, e.g., as might occur under arcing conditions. As a result, the increases in temperature in operating tips are generally minimal unless the heat sinking to the substrate is weak, e.g., in ultrasharp tips, in tips on long, narrow posts, and/or in tips with severely degraded thermal conductivity. Apart from these exceptions, the small temperature excursions mean that no thermal runaway, melting, thermal desorption, or other direct thermal effects occur. Thermal stresses are of course also minimal; however, Maxwell stresses can be large under normal operating conditions, approaching the yield strength under high bias conditions.

Comment on “More evidence indicates link between El Niños and Seismicity”] Link Between El Niños and seismicity is still missing

In a recent Eos article, Walker [1995] presents evidence for a correlation between extreme lows in the Southern Oscillation Index and episodic seismic activity on the southern East Pacific Rise. He speculates that the causative link between seismicity and El Niños may be direct and indirect thermal effects associated with massive submarine volcanic and hydrothermal activity that may accompany the seismic swarms. In particular, he cites an unusual earthquake swarm at 18°, 116° in 1991/1992 and notes that large numbers of volcanos and young, extensive lava flows have been mapped near the East Pacific Rise from about 15° to 19° [Scheirer et al., 1993].

Phytoplankton community assessments of seven southeast U.S. cooling reservoirs

The phytoplankton community structure, productivity and biomass of seven southeastern United States cooling reservoirs were investigated between 1979 and 1986, with emphasis on data from 1984 to 1986. These reservoirs represented a variety of trophic states and geographic provinces, and included three piedmont systems, two coastal plain systems and one each in the mountains and sandhills. The study reservoirs differed from northern temperate lakes in seasonal phytoplankton taxonomic patterns, the dominance of flagellated chrysophytes and cryptomonads, lack of spring diatom blooms and generally low abundance of blue-green algae, particularly in the larger systems. The small reservoirs were more susceptible to algal blooms, caused by nutrient trapping and elevated temperatures from thermal loading. Direct thermal discharge effects upon the phytoplankton communities were either localized or non-significant, depending upon site-specific circumstances. Indirect effects of thermal loading caused ecosystem-wide alterations both from top-down (fish) and bottom-up (phytoplankton) effects. In one acidic reservoir, power-plant operational changes reduced concentrations of water-column metals, with major concurrent alterations in phytoplankton taxonomic structure.

Consequences of winter tropical pressure anomalies in the Australian region

AbstractWe have performed three general circulation model (GCM) experiments with a view to isolating the direct thermal effects of imposed sea‐surface temperature (SST) anomaly patterns to the north of Australia from the dynamic effects associated with the circulation changes they induce. We have done this by a novel technique of adding bias terms to the pressure‐tendency equation but leaving all other aspects of the model unchanged. The nature of the three pressure ‘nudging’ terms were designed so that in long model runs the simulated sea‐level reductions would be similar to those induced in the SST anomaly experiments performed previously. Hence, we have forced low‐level circulation anomalies without imposing any direct surface thermal forcing. The results are compared with standard runs performed with SST forcing.The changes in evaporation in the Australian region were rather different in the comparable pressure‐forcing and SST‐forced experiments. However, most of the parameters considered here responded to the surface‐pressure forcing in a very similar way to that due to ocean‐temperature forcing considered in our earlier study. This was true, in particular, for winter precipitation over Australia. The results suggest that, at least in the Australian tropics, the apparently large impacts of SST anomalies are associated fundamentally with the anomalous circulations they set up rather than the direct impact of the heated ocean waters themselves. We find, as have others, that precipitation anomalies are associated closely with changes of the low‐level convergence of moisture. Indeed, an intriguing finding from our present study is that anomalies of evaporation and precipitation assume opposite signs over most of the domain.Analyses with the comprehensive ocean‐atmosphere data set (COADS) imply that there is some persistence of winter tropical sea‐level pressure in the Australian region, independent of the local endurance of SST. Such persistence may provide some independent skill for Australian winter climate outlooks.