Steady Cold Research Articles

Cold-Temperature Coding with Bursting and Spiking Based on TRP Channel Dynamics in Drosophila Larva Sensory Neurons.

Temperature sensation involves thermosensitive TRP (thermoTRP) and non-TRP channels. Drosophila larval Class III (CIII) neurons serve as the primary cold nociceptors and express a suite of thermoTRP channels implicated in noxious cold sensation. How CIII neurons code temperature remains unclear. We combined computational and electrophysiological methods to address this question. In electrophysiological experiments, we identified two basic cold-evoked patterns of CIII neurons: bursting and spiking. In response to a fast temperature drop to noxious cold, CIII neurons distinctly mark different phases of the stimulus. Bursts frequently occurred along with the fast temperature drop, forming a peak in the spiking rate and likely coding the high rate of the temperature change. Single spikes dominated at a steady temperature and exhibited frequency adaptation following the peak. When temperature decreased slowly to the same value, mainly spiking activity was observed, with bursts occurring sporadically throughout the stimulation. The spike and the burst frequencies positively correlated with the rate of the temperature drop. Using a computational model, we explain the distinction in the occurrence of the two CIII cold-evoked patterns bursting and spiking using the dynamics of a thermoTRP current. A two-parameter activity map (Temperature, constant TRP current conductance) marks parameters that support silent, spiking, and bursting regimes. Projecting on the map the instantaneous TRP conductance, governed by activation and inactivation processes, reflects temperature coding responses as a path across silent, spiking, or bursting domains on the map. The map sheds light on how various parameter sets for TRP kinetics represent various types of cold-evoked responses. Together, our results indicate that bursting detects the high rate of temperature change, whereas tonic spiking could reflect both the rate of change and magnitude of steady cold temperature.

Thermal Management for Natural Convection within Porous Enclosures

Various simulations and numerical studies have been carried out for free convection heat transfer of a square enclosure filled with porous matrix for sinusoidal and uniform heating conditions also varying Rayleigh values from 1 to 500 by using a mathematical finite element simulation. The porous media chosen for this research is saturated water medium (H2O).The enclosure properties have been predefined as follows: The top and base walls of the enclosure are made adiabatic, whereas the right wall is kept at a steady cold temperature. The hot left wall is treated at varying temperatures. The Nusselt values as well as mean Nusselt values have been quantified for the aforementioned values. It has been observed that the mean Nusselt values rise with the surge in Rayleigh values. For the Rayleigh value of 500, we found that uniform heating condition showed larger values of streamline function when compared to Sinusoidal heating conditions. These simulations were performed by considering a Solar Fresnel as a real-world example. We hope that scholars and engineers collectively working on enhancing or aspiring to numerically model the thermal exchange through a square enclosure filled porous matrix will benefit from the information provided in this research article.

Does urban climate follow urban form? Analysing intraurban LST trajectories versus urban form trends in 3 cities with different background climates

The current climate change trend urges the application of efficient spatial planning to mitigate the effects of urbanization on local urban warming. Nevertheless, how urban temperatures respond to urban form changes inside cities is still insufficiently understood. In this paper, we explored the relationship between urban form and diurnal space-time land surface temperature (LST) trends (2003–2019) in Beijing (continental climate), Cairo (arid) and Santiago (temperate). We analysed changes in land cover, white sky albedo (WSA), night-time lights (NL) and the enhanced vegetation index (EVI) inside areas representing clustered thermal performance (steady cold and hot spots and warming cold and hot spots). The structure of local climate zones (LCZs) was assessed for each LST trend. To test the relevance of other urban form dimensions, we analysed the hierarchical influence of the employed 2D metrics (i.e., built-up cover, WSA, NL and EVI) and additional 3D indicators (i.e., height and volume) on LST, applying machine learning classification and regression trees (CARTs) to Beijing's data. Despite diverse patterns of urban form change, cities in our sample present common LST trends, with thermal differences as a consequence of local climate. LCZs are composed of highly heterogeneous built-up areas inside LST trend categories. In the case of Beijing, LST is hierarchically driven by footprint, WSA and EVI. Moreover, by adding height and volume, urban form differences between LST trend classes that are not evident with 2D data were found. Our findings suggest that a compact green urban tissue is necessary to cope with the current trends of urban warming, taking into account city-specific measures based on the local background climate.

Impacts of non-homogeneous nanofluid approach and orientation angle on convection heat transfer within a 3D wavy cavity

Steady laminar natural convection and heat transfer inside a tilted 3D wavy cavity filled by water-Al2O3 nanofluid does examined numerically by applying the finite element technique. An isothermal curved heater is located at the right surface of the chamber while the left surface remains in a steady cold temperature. The top and bottom horizontal surfaces (top and bottom) are held adiabatic. The governing equations are formulated in the non-dimensional model using the two-component non-homogeneous equilibrium model through transporting phenomena in nanofluids connecting among the influences of Brownian diffusion and thermophoresis. The results of the dimensionless buoyancy-driven parameter, inclination angle, nanoparticle volume fraction and number of undulations were examined. It is shown that the inclination angle, the wavy shape of the surface plus the features of nanofluid are outstanding control parameters to the rate of the heat transfer and the distribution of the fluid flow.

Temporal dynamics of precipitation in an extreme mid-latitude monsoonal climate

Trends of precipitation over the twentieth century are examined by a variety of methods to more fully describe how precipitation has changed in the Russian Far East. Data used are considered to represent conditions of the extreme monsoonal climate of the high-to-mid-latitude climate of the Russian Far East region for the period 1911 to 2005. The study examines within-year characteristics of the 95-year time series. The results show variability of precipitation is high in all months, but especially so during the cold season. Trends in the data indicate that both the wettest and driest months of the year are getting wetter. There are some distinct shifts in the trend patterns. Most noticeable is a shift from positive trends to negative trends. Overall, the results show the highest twentieth century precipitation in the early 1960s and in the late 1970s, with a general decrease since the mid-1980s. This differs from trends and means for Russia as a whole. The results also show standard normals to be different from a complete record of monthly precipitation data. Further, it may not enough to use a limited period times series such as a 30-year normal to represent a steady average for a year or a season, as the mean changes through time; in particular, for a steady cold season, mean one should use the full period.

Effect of hydrogen loop fluctuation on cold neutron performance with hybrid control system in JSNS

Supercritical hydrogen is selected as a moderator material in Japan Spallation Neutron Source Facility (JSNS). Total nuclear heating in the moderator is estimated to be 3.75 kW at 1 MW proton beam power, which provides a hydrogen cryogenic system as a heat load. The heat load changes significantly due to pulse proton beam operation. A control system to mitigate such heat load changes is required for the hydrogen cryogenic system in order to maintain stable operation and steady cold neutron generation. A hybrid control system, which consists of a heater and an accumulator, is developed and installed in the system. In order to build the optimal control method, the behaviors of hydrogen loop are analyzed with an original computer code. The analysis suggests that a stability of hydrogen system and a cold neutron beam performance by the hybrid fluctuation control system are compatible.

Structure of thermal convection development based on inhomogeneous water surface cooling

The generation and development of thermal convection based on inhomogeneous water surface cooling were examined by hydraulic and numerical experiments to examine the characteristics of thermal convection in a closed water body with aquatic plants. A visualization experiment revealed the structural characteristics of a whirlpool when thermal convection was generated quantitatively by using PIV analysis. Then, a water temperature measurement experiment demonstrated that a steady cold water mass generated based on the heat flux transport from the water surface increases. This explained each of the three stages in the convection development process. Moreover, aquatic plants, which grow thickly on the water surface, cause not only vertical but also horizontal flows based on the density difference with the water surface that is not covered by plants, and thus change the development process of the convection cell.

The galaxy stellar mass-star formation rate relation: evidence for an evolving stellar initial mass function?

The evolution of the galaxy stellar mass--star formation rate relationship (M*-SFR) provides key constraints on the stellar mass assembly histories of galaxies. For star-forming galaxies, M*-SFR is observed to be fairly tight with a slope close to unity from z~0-2. Simulations of galaxy formation reproduce these trends owing to the generic dominance of smooth and steady cold accretion in these systems. In contrast, the amplitude of the M*-SFR relation evolves markedly differently than in models. Stated in terms of a star formation activity parameter alpha=(M*/SFR)/(t_H-1 Gyr), models predict a constant alpha~1 out to redshifts z=4+, while the observed M*-SFR relation indicates that alpha increases by X3 from z~2 until today. The low alpha at high-z not only conflicts with models, but is also difficult to reconcile with other observations of high-z galaxies. Systematic biases could significantly affect measurements of M* and SFR, but detailed considerations suggest that none are obvious candidates to reconcile the discrepancy. A speculative solution is considered in which the stellar initial mass function (IMF) evolves towards more high-mass star formation at earlier epochs. Following Larson, a model is investigated in which the characteristic mass Mhat where the IMF turns over increases with redshift. The observed and predicted M*-SFR evolution may be brought into agreement if Mhat=0.5(1+z)^2 Mo out to z~2. Such evolution broadly matches recent observations of cosmic stellar mass growth, and the resulting z=0 cumulative IMF is similar to the paunchy IMF favored by Fardal et al to reconcile the observed cosmic star formation history with present-day fossil light measures. [abridged]

Gravity Currents in a Deep Anelastic Atmosphere

Abstract This study presents analytic results for steady gravity currents in a channel using the deep anelastic equations. Results are cast in terms of a nondimensional parameter H/H0 that relates the channel depth H to a scale depth H0 (the depth at which density goes to zero in an isentropic atmosphere). The classic results based on the incompressible equations correspond to H/H0 = 0. For cold gravity currents (at the bottom of a channel), assuming energy-conserving flow, the nondimensional current depth h/H is much smaller, and nondimensional propagation speed C/(gH)1/2 is slightly smaller as H/H0 increases. For flows with energy dissipation, C/(gH)1/2 decreases as H/H0 increases, even for fixed h/H. The authors conclude that as H/H0 increases the normalized hydrostatic pressure rise in the cold pool increases near the bottom of the channel, whereas drag decreases near the top of the channel; these changes require gravity currents to propagate slower for steady flow to be maintained. From these results, the authors find that steady cold pools have a likely maximum depth of 4 km in the atmosphere (in the absence of shear). For warm gravity currents (at the top of a channel), h/H is slightly larger and C/(gH)1/2 is much larger as H/H0 increases. The authors also conduct two-dimensional numerical simulations of “lock-exchange flow” to provide an independent evaluation of the analytic results. For cold gravity currents the simulations support the analytic results. However, for warm gravity currents the simulations show unsteady behavior that cannot be captured by the analytic theory and which appears to have no analog in incompressible flow.

A note on the Strouhal number dependence of the relative importance of internal and external flow noise sources in IC engine exhaust systems

This note discusses issues related to the estimation of flow noise emission from rear mufflers in IC engine exhaust systems, through the analysis of measurements performed in a steady cold flow bench. First, the net acoustic power transmitted along the outlet pipe is obtained from in-duct pressure measurements. The in-duct power is then compared with noise measurements carried out in a semianechoic chamber, in order to distinguish between flow noise contributions associated with internal generation (muffler and tailpipe) and flow noise produced in the discharge process (interaction between the outgoing flow and the outside atmosphere). The ratio between the tailpipe in-duct acoustic power and the radiated acoustic power is analysed as a function of the Strouhal number. The results provide some information about the relative importance of internal and external sources.

Temperature and vacuum measurements on the commercial assembly of a large-volume Ge detector

This work reports on tests which have been extensively made on the assembly of a “dummy” large-volume germanium detector with the aim of measuring temperature gradients along the crystal, as well as in different parts of the cryostat, during the steady cold, room temperature and annealing phases and in the transitions between them. Measurements of the vacuum level and trends of the residual gas composition in the cryostat in the different phases of operation are also reported.

Application of computational fluid dynamics tools to circuit-breaker flow analysis

This paper presents the results of the application of a computational fluid dynamics computer program to the simulation of cold and plasma flows in circuit breakers. The underlying physical model is based on the axisymmetric form of the conservation equations which are coupled with an arc model including ohmic heating and radiative exchanges of energy in the fluid. Various cases are computed, ranging from steady cold flow to unsteady arc-flow interaction. A good agreement has been found between the computed solutions and the available experimental data, demonstrating a great potential of these tools for circuit-breaker design and analysis in the future.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Activation in frog atrial trabeculae: dependence on temperature and length

Isolated frog atrial trabeculae were activated using the method of Na+ withdrawal to induce contractures of relatively steady tension. External Na+ concentration [( Na+]o) during contractures was varied between 0.25 and 45 mM. Isometric contracture tension was measured at cold (4 degrees C) and warm (20 degrees C) temperatures. In addition, rapid temperature jumps (complete in approximately 400 ms) were imposed during cold contractures, resulting in tension transients that consisted of an initial increase in tension followed by a decrease, the latter phase being greater at small and moderate reductions in [Na+]o. Peak contracture tension varied with relative muscle length. The trabeculae became more sensitive with stretch to Na+ withdrawal at 20 degrees C and generated relatively greater tensions at a given [Na+]o. The initial tension increase after a temperature jump was directly proportional to the peak contracture tension immediately preceding the increase in temperature and was therefore interpreted as reflecting an effect of the higher temperature on the attached force-generating cross bridges. The effects of cold and warm steady temperatures and temperature jumps during isometric twitches were also studied. Peak twitch tension varied inversely with temperature (stimulus frequency = 0.2 Hz). In contrast, temperature jumps imposed during the rising phase of twitches at a steady cold temperature (approximately 4 degrees C) resulted in a large initial increase in tension followed by relaxation at a rate that was characteristic of the elevated temperature. The results suggest that, at the warmer temperature (approximately 20 degrees C), activation (i.e., number of attached cross bridges) of the myocardium is significantly less than maximal during the twitch response. The dependence of the tension vs. [Na+]o curves and the tension transients resulting from the temperature jumps on relative muscle length provide evidence for a length dependency of contractile activation in intact atrial trabeculae under conditions of steady-state tension development.

Analysis of Karman vortex clouds revealed by satellite images

The analysis of the Karman vortex cloud street in the wake of Cheju Island Korea in geostationary meteorological satellite imageries together with meteorological data indicate following features. (1) The frequency of formation depends upon that of a cold-air outbreak. Frequency of a well developed one during a cold season of Dec., Jan., Feb. and March is in average 10. (2) Favorable meteorological conditions for the formation is a sharp air temperature inversion below the top of the highest mountain in the center of the island and a steady cold northerly wind. (3) Displacement speed of the vortices has an inverse relationship with the size of b/a where a is the distance of successive vortex pair and b is the distance between the vortices consisting a pair. (4) The time required to reach mature stage of a vortex pair is around three hours.

A Numerical Investigation of the Severe Thunderstorm Gust Front

The structure of the thunderstorm gust front is investigated by a nonhydrostatic, two-dimensional (x,z) numerical model. In the model, which is dry, the production of negatively buoyant air by evaporation is parameterized via an externally imposed, local-cooling function. This parameterization sustains a steady cold downdraft, which drives the surface outflow and associated gust front. It is shown that two dominant factors influencing gust front structure in the vertical plane are the solenoidal field coincident with the front and surface friction, modeled by means of a simple bulk aerodynamic drag formulation. The circulation theorem is invoked to illustrate how solenoidal accelerations oppose the deceleration by surface friction. After the onset of a downdraft in the model, these opposing tendencies soon reach a balance. Thus, following a brief transient stage, the model gust front exhibits a persistent configuration as it propagates rapidly forward. The essential features of this configuration are examined and compared with both tower observations of gust fronts and laboratory models of gravity currents.

Alterations in the Endogenous Enteric Bacterial Flora and Microbic Permeability of the Intestinal Wall in Relation to the Nutritional and Meteorological Changes

There are certain demonstrable changes that take place within the gastrointestinal tract during the process of adaptation to external stimuli. The body as a whole reacts in this adjustment to a changing environment. We have presented our evidence and indicated some instances where these gastrointestinal changes can be considered significant from an epidemiological and preventive medicine standpoint.The loss of the self-disinfecting power, changes in acid-base equilibrium, and other demonstrable alterations within the lumen of the alimentary tract are only a part of the changes taking place in the organism during the process of adaptation to external environmental changes. If certain diseases are associated with a disturbance of the equilibrium between the parasites and the host, then it naturally follows that we must have more information upon the biological mechanism of the host in regard to its changes in susceptibility and resistance to the parasitic environment. Our present knowledge of bacteriology throws little light upon this epidemiological question. It has been the aim of the author to study the mechanism by which the organism adapts itself to certain environmental changes. We have avoided using pharmacological and other artificial agents that would produce body changes, but have restricted ourselves to simple alterations in diet, external temperature and similar mild or natural environmental factors, and followed the mechanism of adaptation to these physiological stimuli.The loss of the power of a body-covering layer, to destroy bacteria in contact with it, must increase the hazards of invasion of this body surface by bacteria. We have shown that a sudden change in the intra-intestinal acid-base equilibrium leads to an inhibition of the mucosa to destroy bacteria within its lumen and is accompanied at times by the appearance of viable bacteria in the thoracic duct lymph stream.If an organism does not adapt itself to its meteorological environment, it is more susceptible to its parasitic environment. The same is true of the nutritional environmental factors. Disturbances due to lack of adaptation to climatic changes can in part be offset by altering the diet. The weather and food factors cannot be separated and one can influence the other.Changes in climate are beneficial to the well-being of the population living in the temperate zones where meteorological conditions are ever changing as compared to the steady cold in the arctic or constant heat as in the tropics. Changes in food are also beneficial. A high protein meal is stimulating. In the tropics where the skin is in a state of over-stimulation due to the high external temperature and humidity the ingestion of an alcoholic beverage to stimulate the splanchnic system before a meal is beneficial. Acidifying an infant's food in hot weather is a common practice. Many such instances could be cited. It seems to be of advantage to an organism to be in a changing environment. The tonus of our physiological systems is not static or fixed, but is ever changing. The more delicate the index used to measure functional changes, the more frequently are such changes observed. These alterations in environment must not exceed the power of the organism to adapt itself to these changes.