Variable Environmental Temperatures Research Articles

Real-time optimization of the liquid-cooled data center based on cold plates under different ambient temperatures and thermal loads

With the advent of the information age, the scale of data centers has developed unprecedentedly, in which the cooling system consumes a lot of energy. Therefore, it is crucial to adjust the operating parameters in real-time to maximize energy savings. In this article, the mathematical models of each component are established, and the functions of system power consumption and chip temperatures are obtained for the liquid-cooled data center based on cold plates. The method proposed in this article has good accuracy through experimental verification and can be used for the optimization of operating parameters. The server chips in data centers need to be maintained within a safe range, so we take the minimum system power consumption as the optimization goal and the chip temperature as the constraint condition to calculate the optimal cooling tower wind volume, primary side flow rate, and secondary side flow rate under different environmental temperatures and heat loads, and fit all three for real-time optimization and regulation. The results show that the intelligent control proposed in this article can save 42.7% energy and reduce PUE to 1.16 under variable heat load, and save 30.6% energy and improve PUE by 4.3% under variable environmental temperature. The intelligent control method described in this article provides guidance for real-time optimization in data centers.

Influence of temperature variability on the feeding behavior and blood consumption of Triatoma infestans (Hemiptera: Reduviidae).

The transmission and incidence of vector-borne diseases rely on vector distribution and life history traits such as survival, fecundity, and feeding. Since arthropod disease vectors are ectotherms, these vital rates are strongly influenced by temperature. Chagas disease is a neglected tropical disease caused by the protozoan parasite, Trypanosoma cruzi. This parasite is transmitted when the feces of the infected triatomine enter the bloodstream of the host. One of the most important vector-species of this disease in the Southern Cone region of South America is Triatoma infestans. In this study, we evaluated the role of constant and variable environmental temperature on the feeding behavior of T. infestans. Fifth-instar nymphs were acclimatized to 4 thermal treatments comprising 2 temperatures (27 °C and 18 °C) with and without diurnal thermal variability (27 ± 5 °C and 18 ± 5 °C). Individuals were fed weekly for 7 wk to quantify their feeding. Our results showed lower feeding frequency in nymphs acclimatized to cold temperature compared to those from warmer temperature treatments. However, treatments with thermal variability presented a nonlinear effect on feeding, with an increased feeding rate in the cold, variable treatment and a decreased feeding rate in the warm, variable treatment. Individuals maintained under cold treatments, the variable temperature exhibited a higher feeding rate and the lowest amount of ingested blood among all treatments. Thus, natural diurnal temperature variation cannot be ignored if we are to make more accurate T. cruzi transmission risk predictions now and in the future.

Effect of brief exposures of anesthesia on thermotolerance and metabolic rate of the spotted-wing fly, Drosophila suzukii: Differences between sexes?

The spotted-wing fly, Drosophila suzukii, is a world-wide pest insect for which there is increasing interest in its physiological traits including metabolism and thermotolerance. Most studies focus only on survival to different time exposures to extreme temperatures, mainly in female flies. In addition, it has not been tested yet how anesthesia affects these measurements. We analyzed the effects of anesthesia by brief exposures to cold, anoxia by CO2 or N2 on three standard thermotolerance assays, as well as the aerobic metabolic rate in both sexes. For heat tolerance we measured CTmax by thermolimit respirometry, and CTmin and chill-coma recovery time for cold tolerance. Aerobic metabolism was calculated by CO2 production of individual flies in real time by open flow respirometry. Results showed that females have a significantly higher V̇CO2 for inactive (at 25 °C) and maximum metabolic rate than males. This difference is mainly explained by body mass and disappears after mass correction. Males had a more sensitive MR to temperature than females showed by a significantly higher Q10 (2.19 vs. 1.98, for males and females, respectively). We observed a significantly lower CTmin (X2 = 4.27, P = 0.03) in females (3.68 ± 0.38 °C) than males (4.56 ± 0.39 °C), although we did not find significant effects of anesthesia. In contrast, anesthesia significantly modifies CTmax for both sexes (F3,62 = 7.86, P < 0.001) with a decrease of the CTmax in cold-anesthetized flies. Finally, we found a significantly higher CTmax in females (37.87 ± 0.07 °C) than males (37.36 ± 0.09 °C). We conclude that cold anesthesia seems to have detrimental effects on heat tolerance, and females have broader thermotolerance range than males, which could help them to establish in invaded temperate regions with more variable environmental temperatures.

Effect of Coolant Temperature on the Thermal Compensation of a Machine Tool

Machine tool (MT) accuracy is an important factor in the industry and is affected by heat generation through internal and external moving parts; the electrical components used; and variable environmental temperatures. Thermal errors lead to 40–60% of all MT errors. To improve MT accuracy, efficient techniques to minimize thermal errors must be identified. This study investigated the coolant temperature effects under different rotating speeds of a standalone built-in spindle system and computer numerical control (CNC) machine with a direct-drive spindle on the accuracy of thermal deformation prediction. The z-axis thermal deformation of the standalone built-in spindle system and CNC machine with a direct-drive spindle was conducted at different spindle rotating speeds and coolant temperatures at a constant coolant flow rate of 5 LPM. All experiments were conducted in a steady and dynamic operation according to ISO 230-3. For the standalone built-in spindle system, in comparison to the Mares model, the developed new model based on the coolant temperature effect on the Mares model (Mares CT model) can improve the thermal deformation prediction accuracy by 18.17% to 39.50% at different coolant temperatures of 12 ∘C to 26 ∘C and the accuracy can be controlled within the range of 0.03 μm to 5.24 μm, while the supply coolant temperature is above 16 ∘C. However, the thermal compensation analysis of the Mares CT model for a CNC machine with a direct-drive spindle shows a thermal deformation prediction accuracy improvement of 58.30% to 66.35% at different coolant temperatures of 22 ∘C to 28 ∘C and the accuracy can be controlled within the range of 0.14 μm to 4.05 μm. To validate the feasibility of the compensation model in real machining processes, dynamic operational analysis was performed for a standalone built-in spindle system and a CNC machine with a direct-drive spindle, and the thermal deformation prediction accuracy improved by 12.19% to 35.53% with the standalone built-in spindle system and 40.25% to 60.33% with the CNC machine with a direct-drive spindle. The compensation model analysis shows that the coolant temperature has a high impact on thermal deformation prediction and markedly affects system accuracy within certain limits.

Uncovering adaptive mechanisms and resilience among older adults: A qualitative study on the mental health impacts of temperature variations.

Variable environmental temperature changes have affected different population groups; however, limited empirical studies in nursing have focused on older adults. One of the most pressing issues of today is climate change, where nurses should explore and advance their roles. This study aimed to explore and describe the experience of older adults with temperature variations as a consequence of climate change and its impact on mental health. Descriptive phenomenological approach was used in this study. Purposeful sampling was used in selecting key informants, while individual telephone interviews and videoconferencing platforms using a semi-structured interview guide were used as the data gathering method to gather key informants' accounts of their experiences. Prior to data collection, authors bracket their preconceived beliefs and values regarding the phenomenon at hand. Colaizzi's seven-step method of data analysis combined with the use of qualitative data analysis software was used to develop the themes and sub-themes. Eleven key informants aged 60-77 participated in this study. Sixty significant statements on temperature variations and mental health were extracted, while forty-one meanings were formulated from the significant statements. Important meanings were grouped into a cluster of themes which built the three major themes and seven sub-themes. The major themes are Theme 1: Active recollection and recognition of their experience; Theme 2: Symptoms of physical, social, mental, and cognitive aspects transformation; and Theme 3: Establishing adaptive mechanisms. The themes reflect a mental or cognitive process of recognizing and understanding their experiences, experiencing their impacts, developing adaptive mechanisms, and showing characteristics of resilience. The themes and sub-themes developed in this study showed that despite their vulnerability, older adults were able to implement adaptive mechanisms and showed signs of resiliency. Temperature variations brought limitations or adjustments to the physical, social, mental, and cognitive aspects of the key informants. Further studies should be conducted in other population groups and various geographical locations to identify sources of adaptive mechanisms and resilience to temperature variations and climate change among older adults. The findings should be used in developing health programs and crafting policies.

A comparison of thermal sensitivities of wing muscle contractile properties from a temperate and tropical bat species.

Endotherms experience temperature variation among body regions, or regional heterothermy, despite maintaining high core body temperatures. Bat forelimbs are elongated to function as wings, which makes them vulnerable to heat loss and exaggerates regional heterothermy. A tropical bat species, Carollia perspicillata, flies with distal wing muscles that are substantially (>10°C) cooler than proximal wing muscles and significantly less temperature sensitive. We hypothesized that the difference between proximal and distal wing muscles would be even more extreme in a temperate bat species that is capable of flight at variable environmental temperatures. We measured the contractile properties of the proximal pectoralis muscle and distal extensor carpi radialis muscle at a range of temperatures in the big brown bat, Eptesicus fuscus, and compared their thermal dependence with that of the same muscles in C. perspicillata. We found that, overall, temperature sensitivities between species were remarkably similar. The sole exception was the shortening velocity of the pectoralis muscle in E. fuscus, which was less temperature sensitive than in C. perspicillata. This decreased temperature sensitivity in a proximal muscle runs counter to our prediction. We suggest that the relative lability of body temperature in E. fuscus may make better pectoralis function at low temperatures advantageous.

Thermoregulation by Bullsnakes (Pituophis catenifer sayi): do burrows make life easier on the prairies?

Reptiles living in the grasslands of Western Canada cope with extremely variable environmental temperatures. We studied body temperatures (Tb) and operative environmental temperatures (Te) for Bullsnakes (Pituophis catenifer sayi (Schlegel, 1837)) to address uncertainties regarding challenges posed by the thermal environments of northern grasslands, and to evaluate conflicting hypotheses regarding thermoregulatory strategies. Despite potentially extreme surface temperatures (meanmin. = 9.3 °C, meanmax. = 31.4 °C), mammal burrows remained within voluntary limits (15–35 °C) for 93% of the active season and created thermal gradients (up to 27.2 °C) which may facilitate thermoregulation by creating high thermal heterogeneity. This evidence suggests that grasslands may actually be less challenging for thermoregulation than comparable forests. Fifty-eight percent (57.8%) of the variation in observed Tb (meanmin. = 20.1 °C, meanmax. = 29.1 °C) was explained by three simple variables: time of day, day of year, and bare ground Te. Bullsnakes thermoregulated by conforming to Te near their preferred range (21–27 °C), selecting locations that enabled heating up below this range and avoiding warmth above this range. Our results support broad hypotheses of reptilian thermoregulation that predict increased thermoregulation when (i) environmental temperatures deviate farther from preferred ranges and (ii) costs of thermoregulation are lower due to thermal heterogeneity.

A comprehensive procedure for estimating the stressed-strained state of a reinforced concrete bridge under the action of variable environmental temperatures

This paper reports the full-scale experimental measurements of temperature distribution over the surfaces of bridges' steel-concrete beams under the influence of positive and negative ambient temperatures. It has been established that the temperature is distributed unevenly along the vertical direction of a bridge's steel-concrete beam. It was found that the metal beam accepted higher temperature values. The maximum registered temperature difference between a metal beam and a reinforced concrete slab at positive ambient temperatures was +9.0 °C, and the minimum temperature difference was −2.1 °C. The mathematical models for calculating a temperature field and a thermally strained state of bridges' steel-concrete beams under the influence of variable climatic temperature changes in the environment have been improved, taking into consideration the uneven temperature distribution across a bridge's reinforced concrete beam. The possibility has been established to consider a one-dimensional problem or to apply the three-dimensional estimated problem schemes as the estimation schemes for determining the thermo-elastic state of reinforced concrete bridges. The temperature field and the stressed state of bridges' reinforced concrete beams were determined. It was found that the maximum stresses arise at the place where a metal beam meets a reinforced concrete slab. These stresses amount to 73.4 MPa at positive ambient temperatures, and 69.3 MPa at negative ambient temperatures. The amount of stresses is up to 35 % of the permissible stress values. The overall stressed-strained state of a bridge's reinforced concrete beams should be assessed at the joint action of temperature-induced climatic influences and loads from moving vehicles

APPLICATION OF ENERGY AND EXERGY ANALYSIS TO INVESTIGATE THE OPERATION OF AN AIR HANDLING UNIT WITH HEAT PUMP

With the growth of energy-efficient building sector, ventilation systems are becoming increasingly important not only of fresh air supply but also in terms of energy consumption. The aim of this paper is to describe and analyse the operation of an air handling unit (AHU) with a heat pump using energy and exergy analyses under the variable environmental temperature (from –30 °C to 10 °C). The application of selected methods is illustrated in a case study of an AHU using environmental temperatures of Vilnius city during heating season (from the beginning of October to the end of April). An analytical method for determining distribution of the environmental (outdoor air) temperature is used. Energy and exergy analyses showed periods when the highest amounts of energy and exergy were consumed and the greatest exergy losses occurred. This allowed to reveal the component of the system with the highest exergy losses – the heat pump evaporator. Therefore, further research is needed for its design and application. At the end of the article, the seasonal indicators of the AHU with heat pump operation were calculated: coefficient of performance and exergy efficiency. The presented research procedure could be applied to the analysis of other energy systems and processes in them.

Extreme and variable environmental temperatures are linked to reduction of social network cohesiveness in a highly social passerine

Organisms living in hot, arid environments face important risks associated with hyperthermia and dehydration which are expected to become more severe with climate change. To mitigate these risks, individuals often modify behaviour, e.g. reducing activity and seeking shade. These behavioural modifications may affect interactions between individuals, with consequences for the social structure of groups. We tested whether the social structure of cooperative groups of sociable weavers Philetairus socius varied with environmental temperature. We recorded the nature and frequency of interactions at feeders positioned beneath three sociable weaver colonies (n = 49 identified birds) in the Kalahari Desert with respect to environmental temperatures over a 30‐day period. Using random forest models, we examined whether thermal conditions predicted variation in social network structure. We also conducted focal observations of individual weavers to assess functional links between temperature, intensity of heat dissipation behaviour (panting) and immediate effects on social behaviour. Our results suggest that the social structure of weaver colonies becomes less cohesive and more fragmented at extreme and variable environmental temperatures. These changes in network structure appear to be linked with individuals’ heat dissipation behaviour: extreme and variable temperatures were associated with increased panting, which was significantly correlated with an immediate reduction in the frequency of association. Collectively, our results indicate that interactions within groups could be disturbed by environmental temperature variation and extremes. Changing temperature regimes could therefore affect the functioning of animal societies by altering social networks.

Performance Analysis of a Combined Absorption Refrigeration-Liquid Desiccant Dehumidification THIC System Driven by Low-Grade Heat Source

Traditional condensing air-conditioning systems consume large amounts of energy in hot and humid areas, and it is difficult to achieve simultaneous control of temperature and humidity. A combined absorption refrigeration (AR) and liquid desiccant dehumidification (LDD) air-conditioning system based on cascade utilization of low-grade heat source is proposed. The system can realize independent control of temperature and humidity and carry out profound recovery of low-grade heat sources. Under the design conditions, the heat utilization rate ζ reaches 21.05%, which is 2.73 times that of the conventional absorption refrigeration reference system. A parametric sensitivity analysis is performed to optimize the system. The ζ increases from 9.79% to 18.55% and the coefficient of performance COPt increases from 0.33 to 0.35 with an increase in chilled water temperature from 7°C to 15°C. With an increase in regenerant solution temperature from 60°C to 70°C, the ζ achieves the optimal value of 21.05% at 68°C. ζ decreases from 21.05% to 15.05% as the concentration of the regenerant solution increases from 36% to 40%. Under variable environmental temperature and humidity, the ζ of the proposed system changes within a small range and stays much higher than that of the reference system with the same quality heat source, which indicates that the proposed system has a better adaptability to changing environmental parameters.

Exergy Analysis and Process Optimization with Variable Environment Temperature

In its usual definition, exergy cancels out at the ambient temperature which is thus taken both as a constant and as a reference. When the fluctuations of the ambient temperature, obviously real, are considered, the temperature where exergy cancels out can be equated, either to the current ambient temperature (thus variable), or to a constant reference temperature. Thermodynamic consequences of both approaches are mathematically derived. Only the second approach insures that minimizing the exergy loss maximizes performance in terms of energy. Moreover, it extends the notion of reversibility to the presence of an ideal heat storage. When the heat storage is real (non-ideal), the total exergy loss includes a component specifically related to the heat exchanges with variable ambient air. The design of the heat storage can then be incorporated into an optimization procedure for the whole process. That second approach with a constant reference is exemplified in the case study of heat pumping for heating a building in wintertime. The results show that the so-obtained total exergy loss is the lost mechanical energy, a property that is not verified when exergy analysis is conducted following the first approach.

Proteomic changes across a natural temperature gradient in a marine gastropod

Responses of marine ectotherms to variable environmental temperature often entails maintanence of cellular homeostasis and physiological function through temperature compensation and physiological changes. We investigated the physiological response to thermal stress by examining proteomic changes in the marine kelp forest gastropod and emerging fisheries species Kellet's whelk (Kelletia kelletii) across a naturally-existing thermal gradient that ranges from a warmer-water site inside the species' native range and extends to the northern, cold-water edge of the range. We hypothesized that abundance of cellular stress response and energy metabolism proteins would increase with decreasing temperature in support of cold-compensation. Our exploratory proteomic analysis of whelk gill tissue (N = 6 whelks) from each of the four California Channel Island sites revealed protein abundance changes related to the cytoskeleton, energy metabolism/oxidative stress, and cell signaling. The changes did not correlate consistently with temperature. Nonetheless, whelks from the coldest island site showed increased abundance of energy metabolism and oxidative stress proteins, possibly suggesting oxidative damage of lipid membranes that is ameliorated by antioxidants and may aid in their cold stress response. Similarly, our exploratory analysis revealed abundances of cell signaling proteins that were higher at the coldest site compared to the warmest site, possibly indicating an importance for cell signaling regulation in relatively cooler environments. This study provides protein targets for future studies related to thermal effects in marine animals and may contribute to understanding the physiological response of marine organisms to future ocean conditions.

The effect of body posture on available habitat and activity-time in a lizard: Implications for thermal ecology studies

Ectothermic animals contend with variable environmental temperature through behavioral thermoregulation, including selection of activity-times and microhabitat spaces with suitable operative temperatures. Thus, an important component to understanding the influence of temperature on animals is through the assessment of thermal constraints on time and space usage. Thermal ecologists have recognized that postural adjustments are an important part of behavioral thermoregulation. However, the impact of postural adjustments on available space and time has received little attention. We hypothesized that postural adjustments would significantly affect the thermal availability of space and time for surface activity. To test our hypothesis, we used data collected over a four-year study of the thermal ecology of Eastern Collared Lizards (Crotaphytus collaris) in Arkansas. We used a novel approach to model three distinct postures used by C. collaris, and to assess the impact of posture on available space and time. For our study species and habitat, posture had a significant impact on several indices of available space and time including: a) a 13% increase in length of the reproductive activity season, b) a 35% increase in the frequency distribution of habitat within active body temperature range and c) a 42% increase in average thermal quality index. We conclude that posture can significantly impact space and time available for surface activity in species that employ it for thermoregulation. Thus, a clearer understanding of the thermal constraints on time-space usage in ectotherms requires consideration of the impact of posture on the spatiotemporal distribution of thermally suitable microhabitats.

Effect of temperature on antioxidant defense and innate immunity in Brandt's voles.

Ambient temperature is an important factor influencing many physiological processes, including antioxidant defense and immunity. In the present study, we tested the hypothesis that antioxidant defense and immunity are suppressed by high and low temperature treatment in Brandt’s voles (Lasiopodomys brandtii). Thirty male voles were randomly assigned into different temperature groups (4, 23, and 32 °C, n=10 for each group), with the treatment course lasting for 27 d. Results showed that low temperature increased gross energy intake (GEI) and liver, heart, and kidney mass, but decreased body fat mass and dry carcass mass. With the decline in temperature, hydrogen peroxide (H2O2) concentration, which is indicative of reactive oxygen species (ROS) levels, increased in the liver, decreased in the heart, and was unchanged in the kidney, testis, and small intestine. Lipid peroxidation indicated by malonaldehyde (MDA) content in the liver, heart, kidney, testis, and small intestine did not differ among groups, implying that high and low temperature did not cause oxidative damage. Similarly, superoxide dismutase (SOD) and catalase (CAT) activities and total antioxidant capacity (T-AOC) in the five tissues did not respond to low or high temperature, except for elevation of CAT activity in the testis upon cold exposure. Bacteria killing capacity, which is indicative of innate immunity, was nearly suppressed in the 4 °C group in contrast to the 23 °C group, whereas spleen mass and white blood cells were unaffected by temperature treatment. The levels of testosterone, but not corticosterone, were influenced by temperature treatment, though neither were correlated with innate immunity, H2O2 and MDA levels, or SOD, CAT, and T-AOC activity in any detected tissues. Overall, these results showed that temperature had different influences on oxidative stress, antioxidant enzymes, and immunity, which depended on the tissues and parameters tested. Up-regulation or maintenance of antioxidant defense might be an important mechanism for voles to survive highly variable environmental temperatures.

A comparative thermodynamic analysis of air handling units at variable reference temperature

Ventilation and air conditioning systems are emerging as the major energy consumers in low energy buildings. The objective of this paper is to present new methodology for assessment of Air Handling Units (AHUs) taking into account the variations of reference temperature. The methodology using the concept of coenthalpy, developed for heat exchangers and published by the authors previously has been used. Four AHUs that comprise energy transfer devices, such as: Water-to-Air Heater (WAH), Heat Recovery Exchanger (HRE) and Heat Pump (HP) have been investigated. Thermodynamic parameters including Coefficient of Performance (COP), universal and functional exergy efficiencies have been used to compare AHUs and to calculate the exergy destruction in AHU components at variable environment temperature −30 °C… + 10 °C. The results of this study show that using HRE the COP and exergy efficiencies are significantly better compared with AHU without HRE. Using the HRE of higher effectiveness, the thermodynamic indicators can be improved considerably. The study shows that AHUs equipped with HP with advanced control method and HRE are more advantageous compared with other investigated AHUs.The presented methodology could have practical application for evaluating of energy and exergy efficiency of AHUs at different reference temperatures when designing HVAC systems and implementing optimum control methods.

Probabilistic Baseline of Finite Element Model of Bridges under Environmental Temperature Changes

AbstractThe material properties and structural stiffness of actual bridges fluctuate with variations in environmental temperature; therefore, it is not appropriate to use a determined finite element model (FEM) as the baseline model for localizing the structural damage of bridges. To address this issue, we proposed the concept of the probabilistic baseline of FEM of bridges under variable environmental temperature, that is, we established reasonable probability distributions of the physical parameters of bridges that are suitable for damage localization with varying environmental temperature. First, a method is presented to obtain the probabilistic baseline of FEM of bridges, which imports cluster analysis into stochastic FEM updating. Unlike the conventional methods, the measured natural frequencies first are classified into different clusters using the Gaussian mixture method (GMM), with each cluster consisting of measured data that satisfy the same Gaussian distribution. Then, the conventional methods of stochastic FEM updating can be conveniently implemented to obtain the probabilistic baseline of FEM for each cluster. Second, for each cluster, the mean values and covariance of the updating parameters are updated in two sequential steps, and a new approach is proposed for determining the initial covariance of the updating parameters. The results of an actual example show that predetermining a reasonable initial covariance for the updating parameters can accurately and efficiently obtain the updated results. Finally, the effectiveness of the presented method is verified through the monitoring data of an actual bridge.

Mass mortality of eastern box turtles with upper respiratory disease following atypical cold weather.

Emerging infectious diseases cause population declines in many ectotherms, with outbreaks frequently punctuated by periods of mass mortality. It remains unclear, however, whether thermoregulation by ectotherms and variation in environmental temperature is associated with mortality risk and disease progression, especially in wild populations. Here, we examined environmental and body temperatures of free-ranging eastern box turtles Terrapene carolina during a mass die-off coincident with upper respiratory disease. We recorded deaths of 17 turtles that showed clinical signs of upper respiratory disease among 76 adult turtles encountered in Berea, Kentucky (USA), in 2014. Of the 17 mortalities, 11 occurred approximately 14 d after mean environmental temperature dropped 2.5 SD below the 3 mo mean. Partial genomic sequencing of the major capsid protein from 1 sick turtle identified a ranavirus isolate similar to frog virus 3. Turtles that lacked clinical signs of disease had significantly higher body temperatures (23°C) than sick turtles (21°C) during the mass mortality, but sick turtles that survived and recovered eventually warmed (measured by temperature loggers). Finally, there was a significant negative effect of daily environmental temperature deviation from the 3 mo mean on survival, suggesting that rapid decreases in environmental temperature were correlated with mortality. Our results point to a potential role for environmental temperature variation and body temperature in disease progression and mortality risk of eastern box turtles affected by upper respiratory disease. Given our findings, it is possible that colder or more variable environmental temperatures and an inability to effectively thermoregulate are associated with poorer disease outcomes in eastern box turtles.

Measurement of early-age strains in mortar specimens subjected to cyclic temperature

As well known, the volume change induced by environment temperature variation can lead to cracking at the surface of cementitious materials with low water-cement ratio. Thus, it can be said that there is a pressing need to reveal the early-age performance of cementitous materials in a variable environment temperature. Conventional thermocouple and strain gauge have been widely used for measuring temperature and strain in cementitious materials, respectively. However, conventional sensors have several limitations for measuring strain and temperature in cementitous materials such as too many cables for multipoint measurement, short circuit, and electromagnetic interference. Compared to conventional electrical strain gauge, fiber Bragg grating (FBG) has several inherent advantages including multiplexable, resistance to electromagnetic interference, and stable signal in long distance transmission. In this study, two lines mutiplexed with FBG strain and temperature sensors were fabricated and employed to measure the quasi-distributed strain and temperatures in mortar specimens subjected to cyclic temperature.

Determination of time-dependent skin temperature decrease rates in the case of abrupt changes of environmental temperature

The present study deals with the development of a method for determining time-dependent temperature decrease rates and its application to postmortem surface cooling. The study concentrates on evaluating skin cooling behavior since data on skin cooling in the forensic literature are scarce. Furthermore, all heat transfer mechanisms strongly depend on the temperature gradient between body surface and environment. One of the main problems in modelling postmortem cooling processes is the dependence on the environmental temperature. All models for postmortem rectal cooling essentially presuppose a constant environmental temperature. In medico-legal practice, the temperature of the surrounding of a corpse mostly varies; therefore, an approach for extending the models to variable environmental temperatures is desirable. It consists in ‘localizing’ them to infinitesimal small intervals of time. An extended model differential equation is obtained and solved explicitly. The approach developed is applied to the single-exponential Newtonian model of surface cooling producing the following differential equation: T S ′(t)=−λ(t)(T S (t)−T E (t)) (with T S( t) the surface/skin temperature, T E( t) the environmental temperature, λ( t) the temperature decrease rate and T S′( t) the actual change of skin temperature or first-order derivative of T S). The differential equation directly provides an estimator: λ(t)=− T S ′(t) T S (t)−T E (t) for the time-dependent temperature decrease rate. The estimator is applied to two skin cooling experiments with different types of abrupt changes of environmental temperature, peak-like and step-like; the values of the time-dependent temperature decrease rate function were calculated. By reinserting them, the measured surface temperature curve could be accurately reconstructed, indicating that the extended model is well suited for describing surface cooling in the case of abrupt changes of environmental temperature.