Temperature Limit Research Articles

High latitude Northern bats (Eptesicus nilssonii) reveal adaptations to both high and low ambient temperatures.

Insectivorous bats at northern latitudes need to cope with long periods of no food for large parts of the year. Hence, bats which are resident at northern latitudes throughout the year will need to undergo a long hibernation season and a short reproductive season where foraging time is limited by extended daylight periods. Eptesicus nilssonii is the northernmost occurring bat species worldwide and hibernates locally when ambient temperatures (Ta) limit prey availability. Therefore, we investigated the energy spent maintaining normothermy at different Tas, as well as how much bats limit energy expenditure while in torpor. We found that, despite being exposed to Ta as low as 1.1°C, bats did not increase torpid metabolic rate, thus indicating that E. nilssonii can survive and hibernate at low ambient temperatures. Furthermore, we found a lower critical temperature (Tlc) of 27.8°C, which is lower than in most other vespertilionid bats, and we found no indication of any metabolic response to Tas up to 37.1°C. Interestingly, carbon dioxide production increased with increasing Ta above the Tlc, presumably caused by a release of retained CO2 in bats that remained in torpor for longer and aroused at Ta above the Tlc. Our results indicate that E. nilssonii can thermoconform at near-freezing Ta, and hence maintain longer torpor bouts with limited energy expenditure, yet also cope with high Tawhen sun-exposed in roosts during long summer days. These physiological traits will likely enable the species to cope with ongoing and predicted climate change.

Population Status of the Ctenophores <i>Mnemiopsis leidyi</i> Agassiz, 1865 and <i>Beroe ovata</i> Bruguiere, 1789 in the Waters of the North and Middle Caspian Western Shelf in August–September, 2022

The latitudinal distribution of the ctenophores Mnemiopsis leidyi A. Agassiz, 1865 and Beroe ovata Bruguière, 1789 in the Russian sector of the Caspian Sea has different borders of their ranges. Studies on the occurrence of ctenophores in the water column have demonstrated that each species has a characteristic temperature limit of its vertical distribution. Investigations into interactions between ctenophores showed a considerable abundance suppression of M. leidyi (particularly of smaller individuals) by B. ovata.

Effect of fin design and continuous cycling on thermal performance of PCM-HP hybrid BTMS for high ambient temperature applications

In the present work, the thermal performance assessment of fins for a Phase Change Material-Heat Pipe (PCM-HP) based hybrid battery thermal management system (BTMS) for maintaining the average temperature of the battery surface below the safe temperature limits during continuous discharge and charge cycles is presented. A 2D computational model is used for fin design selection and to investigate the thermal performance of the PCM-HP hybrid BTMS. Two base designs and twelve fin designs with varying geometry are studied. The optimal design is chosen based on the effectiveness of the fins, the maximum battery temperature, and the PCM melt fraction. With the optimized fin design, the PCM-HP hybrid BTMS reduces the maximum battery surface temperature by 2.95 °C from 62.85 °C to 59.9 °C as compared to PCM-HP BTMS without fin. Using the selected fin the maximum battery surface temperature is maintained below 60 °C with minimum PCM melt fraction at a heat transfer coefficient of 90 W/m2K for three continuous cycles at an ambient temperature of 40 °C. Experiments are performed to verify the thermal performance of the optimized design. Further, it is observed that increasing the latent heat and thermal conductivity enhances the thermal performance of the PCM-HP hybrid BTMS.

Fabrication, Functional Properties, and Potential Applications of Mixed Gellan-Polysaccharide Systems: A Review.

Gellan, an anionic heteropolysaccharide synthesized by Sphingomonas elodea, is an excellent gelling agent. However, its poor mechanical strength and high gelling temperature limit its application. Recent studies have reported that combining gellan with other polysaccharides achieves desirable properties for food- and biomaterial-related applications. This review summarizes the fabrication methods, functional properties, and potential applications of gellan-polysaccharide systems. Starch, pectin, xanthan gum, and konjac glucomannan are the most widely used polysaccharides in these composite systems. Heating-cooling and ionic-induced cross-linking approaches have been used in the fabrication of these systems. Composite gels fabricated using gellan and various polysaccharides exhibit different functional properties, possibly because of their distinct molecular interactions. In terms of applications, mixed gellan-polysaccharide systems have been extensively used in texture modification, edible coatings and films, bioactive component delivery, and tissue-engineering applications. Further scientific studies, including structural determinations of mixed systems, optimization of processing methods, and expansion of applications in food-related fields, are needed.

Optimization of the method of hydrothermal treatment of mogar grain for production of food concentrate "Talkan"

The possibility of using mogar grain for the production of food concentrates based on the traditional national dish "Talkan" is considered. "Talkan" is a national food concentrate for Republic of Kazakhstan, which has been used as a staple food in long-distance trekking by various cultures for centuries. Traditionally, talkan is prepared from various cereals, particularly millet, wheat and barley. When boiling water and oil are added, it turns into a hearty porridge, and when oil and sugar are added, it becomes a delicious dessert. The difficulty lies in the careful handling and preparation of the mogar grain. During intensive cooking, the grain can easily overcook, resulting in all the valuable nutrients being leached into the broth. In addition, improperly prepared mogar can burn during further roasting. To determine the optimal parameters of mogar hydrothermal treatment and to create a high-quality food concentrate based on the national dish "Talkan", a complex experiment was conducted using modern methods of experiment planning. A number of variables were tested during the experiment, including temperature limits and duration of cooking, as well as temperature, duration and intensity of stirring during drying and roasting of mogar. The study showed that the most favourable conditions for mogar grain involve cooking at an initial temperature of between 15–20 °C for about 60 minutes, gradually reaching 100 °C. The drying and roasting processes are best carried out for 25 minutes, with a layer thickness of 25 mm and a surface temperature of 250 °C. The determined of hydrothermal treatment serve as a basis for the design of specialised equipment for preparation of mogar grain for the purpose of making Talkan

Analytical Study of Acceptable Cover Thickness and Temperature Limits of Tunnel Lining Concrete for Fire Resistance

Analytical Study of Acceptable Cover Thickness and Temperature Limits of Tunnel Lining Concrete for Fire Resistance

Bioenergetic Model of the Highly Exploited Shark Mustelus schmitti under a Global Warming Context

Bioenergetic models are tools that allow the evaluation of the effect of environmental variables on fish growth. Successful implementation of this approach has been achieved in a few elasmobranch species. Our objective was to develop a bioenergetic model for Mustelus schmitti. The model developed showed a good fit to the field data available and accurately described the growth of this species. The practical example developed in this study provides novel population estimates of prey consumption and daily ration for the species. Results also indicate that this species would be susceptible to the effects of climate change. In the simulated climate change scenarios, the energy budget of M. schmitti was significantly altered, with increased food consumption and impaired growth. While there exists a number of limitations for the model developed in this article, namely its limitation to immature individuals, and its restricted temperature model, it provides an important tool for the management of this and other shark populations under heavy exploitation.

The now and future of human biology at the extremes: An introduction to the special issue.

A hallmark of the human species is our adaptability to a wide range of different ecologies and ecosystems, including some of the most extreme settings. Human biologists have long studied how humans have successfully (and sometimes unsuccessfully) adapted to such extremes, particularly ecological extremes like environments at lower limits of temperature and high altitude. In this special issue, we revisit traditional definitions and explore new conceptions of work in extreme environments. We argue that our definitions of extremes should change with our changing world, and account for extremes unique to the Anthropocene, including environments of inequality and precarity, pandemic landscapes, climate-impacted settings, obesogenic environments, and the environments of human spaceflight. We also explore the future of work at the extremes and provide some suggested guidelines on how human biologists can continue to build and expand on foundational work in this area. While human biologists have done critical work on groups living in extreme environments, our definitions of humans at the limits continue to change as the world around us also changes. Scholars in this area have a responsibility to re-examine the parameters of extremes to stay at the forefront of scientific exploration and collaboration so human biology, as a discipline, can continue to shape our understanding of adaptability, and thus contribute to the continued thriving of all humans as we endure new climatic, environmental, and societal extremes.

High-fidelity numerical investigation on structural integrity of SFR fuel cladding during design basis events

A high-fidelity numerical analysis methodology was proposed for evaluating the fuel rod cladding integrity of a Prototype Gen IV Sodium Fast Reactor (PGSFR) during normal operation and Design basis events (DBEs). The MARS-LMR code, system transient safety analysis code, was applied to analyze the DBEs. The results of the MARS-LMR code were used as boundary condition for a 3D computational fluid dynamics (CFD) analysis. The peak temperatures considering HCFs satisfied the cladding temperature limit. The temperature and pressure distributions were calculated by ANSYS CFX code, and applied to structural analysis. Structural analysis was performed using ANSYS Mechanical code. The seismic reactivity insertion SSE accident among DBEs had the highest peak cladding temperature and the maximum stress, as the value of 87 MPa. The fuel cladding had over 40 % safety margin, and the strain was below the strain limit. Deformation behavior was elucidated for providing relative coordinate data on each active fuel rod center. Bending deformation resulted in a flower shape, and bowing bundle did not interact with the duct of fuel assemblies. Fuel rod maximum expansion was generated with highest stress. Therefore, it was concluded that the fuel rod cladding of the PGSFR has sufficient structural safety margin during DBEs.

Effect of Low Temperature on Photosynthetic Characteristics, Senescence Characteristics, and Endogenous Hormones of Winter Wheat “Ji Mai 22” during the Jointing Stage

To investigate the effects of low-temperature (LT) stress on photosynthetic properties and senescence characteristics of winter wheat leaves during the jointing stage, an environmental temperature control experiment was designed at Nanjing University of Information Science and Technology in 2023, using Triticum aestivum L. cv. “Ji Mai 22” as the test material. Four different temperature levels were set: 18 °C/8 °C (daily maximum/daily minimum temperature; CK), 13 °C/3 °C, 10 °C/0 °C, and 7 °C/3 °C. The duration of each treatment was 2, 4, and 6 days, respectively. The experimental findings reveal that the changes in physiological parameters of winter wheat leaves under low-temperature stress treatments are nonlinear. Under the 3 °C LT treatment, the photosynthetic parameters and endogenous hormone levels of wheat leaves significantly decrease after 6 days of stress. Under the 0 °C LT treatment, the photosynthetic parameters, leaf pigment content, and endogenous hormones of wheat decrease significantly, while under the −3 °C LT treatment, all the parameters of winter wheat leaves show a significant decline. Generally, the “Ji Mai22” wheat cultivar has a lower growth temperature limit of −3 °C during the jointing stage.

Study of the radiofrequency-induced heating inside the human head with dental implants at 7 T.

Conductive dental implants are commonly used in restorative therapy to replace missing teeth in patients. Ensuring the radiofrequency (RF) safety of these patients is crucial when performing 7 T magnetic resonance scans of their heads. This study aimed to investigate RF-induced heating inside the human head with dental implants at 7 T. Dental implants and their attachments were fabricated and integrated into an anatomical head model, creating different measurement configurations (MCs). Numerical simulations were conducted using a 7 T transmit coil loaded with the anatomical head model, both with and without dental implants. The maximum temperatures inside the head for various MCs were computed using the maximum permissible input powers (MPIPs) obtained without dental implants and compared with published limits. Additionally, the MPIPs with dental implants were calculated for scenarios where the temperature limits were exceeded. The maximum temperatures observed inside the head ranged from 38.4°C to 39.6°C. The MPIPs in the presence of dental implants were 81.9%-97.3% of the MPIPs in the absence of dental implants for scenarios that exceeded the regulatory limit. RF-induced heating effect of the dental implants was not significant. The safe scanning condition in terms of RF exposure was achievable for patients with dental implants. For patients with conductive dental implants of unknown configuration, it is recommended to reduce the input power by 18.1% of MPIP without dental implants to ensure RF safety.

On the Existence of Ternary Compounds in the CaO-BaO-Al<sub>2</sub>O<sub>3</sub> System

In this article in order to verify the probability of the formation of the compound CaBaAl4O8, a thermodynamic analysis of the following possible solid-phase reactions of its formation was carried out: formation of CaBaAl4O8 from the initial components - calcium carbon dioxide, barium carbon dioxide and aluminum oxide; the probability of formation of dual compounds CaAl2O4 and BaAl2O4 from the same raw materials (since the compound CaBaAl4O8 is located on the BaAl2O4-CaAl2O4 conjugate) and the possibility of formation of the compound CaBaAl4O8 from binary compounds CaAl2O4 and BaAl2O4. As a result of our experimental studies, the existence of ternary compounds Вa3CaAl2O7 and ВaCa2Al8O15 was confirmed, and it was found that the Вa3CaAl2O7 compound exists in the system at least up to a temperature of 1400 °C. Thus, our studies have determined an increase in the temperature limits of its existence, in contrast to the data of previous researchers, who indicated 1250 °C as the upper temperature of existence of Вa3CaAl2O7.

Uncertainties in the transport properties of helium gas at cryogenic temperatures determined using molecular dynamics simulation

In this study, the transport properties, such as diffusivity, viscosity, and thermal conductivity, of 4He at the gaseous phase are computed for state points in the temperature range of 10 K to 150 K and pressure range of 0.10 MPa (1 atm) to 0.21 MPa using classical and quantum frameworks. Within the classical molecular dynamics simulation (MDS), the Green–Kubo (GK) approach is used. The GK method has an inherent uncertainty associated with it due to the random fluctuations in the flux autocorrelation functions. Moreover, in the temperature range of 10 K to 40 K, the quantum nature of the helium gas particles becomes prominent. The classical MDS performed does not include these effects and hence introduces uncertainties in the calculated results. We discuss efficient ways of time averaging the autocorrelation function to reduce statistical fluctuations and perform the quantum scattering phase shift calculations within the Chapman–Cowling theory to study the quantum effects. Furthermore, this study also provides the transport properties data in the cryogenic temperature limit of 10 K to 150 K, which is scarcely studied in the literature and can be applied in complex systems.

Casimir free energy for massive scalars: A comparative study of various approaches

We compute the Casimir thermodynamic quantities for a massive real scalar field between two parallel plates with the Dirichlet boundary conditions, using three different general approaches and present explicit solutions for each. The Casimir thermodynamic quantities include the Casimir Helmholtz free energy, pressure, energy, and entropy. The three general approaches that we use are based on the fundamental definition of Casimir thermodynamic quantities, the analytic continuation method, and the zero temperature subtraction method. Within the analytic continuation approach, we use two distinct methods which are based on the utilization of the zeta function and the Schlömilch summation formula. We include the renormalized versions of the latter two approaches as well, whereas the first approach does not require one. Within each general approach, we obtain the same results in a few different ways to ascertain the selected cancellations of infinities have been done correctly. We show that, as expected, the results based on the zeta function and the Schlömilch summation formula are equivalent. We then do a comparative study of the three different general approaches and their results and show that they are in principle not equivalent to each other, and they yield equivalent results only in the massless case. In particular, we show that the Casimir energy calculated only by the first approach has all three properties of going to zero as the temperature, mass of the field or the distance between the plates increases. Moreover, we show that in this approach the Casimir entropy reaches a positive constant in the high temperature limit, which can explain the linear term in the Casimir free energy. We use the results obtained by the fundamental approach as our reference for the correct results.

Over-barrier photoelectron emission with Rashba spin–orbit coupling

We develop a theoretical model to calculate the quantum efficiency (QE) of photoelectron emission from materials with the Rashba spin–orbit coupling (RSOC) effect. In the low temperature limit, an analytical scaling between QE and the RSOC strength is obtained as QE ∝(ℏω−W)2+2ER(ℏω−W)−ER2/3, where ℏω, W, and ER are the incident photon energy, work function, and the RSOC parameter, respectively. Intriguingly, the RSOC effect substantially improves the QE for strong RSOC materials. For example, the QE of Bi2Se3 and Bi/Si(111) increases, by 149% and 122%, respectively, due to the presence of strong RSOC. By fitting to the photoelectron emission characteristics, the analytical scaling law can be employed to extract the RSOC strength, thus offering a useful tool to characterize the RSOC effect in materials. Importantly, when the traditional Fowler–Dubridge model is considered, the extracted results of the prefactor a1 in QE may substantially deviate from the actual values by ∼90%, thus highlighting the importance of employing our model to analyze the photoelectron emission especially for materials with strong RSOC. These findings provide a theoretical foundation for the design of photoemitters using Rashba spintronic materials.

Fabricating UHMWPE‐based shielding materials with excellent high‐temperature mechanical properties and irradiation endurance properties via controlling crosslinked and crystalline structures

AbstractShielding materials are important guarantees for the reliable operation of nuclear equipment and essential prerequisites for the safe application of nuclear energy. As an essential and most widely used shielding material, improving the high‐temperature mechanical properties of PE‐based shielding material is of significant importance for the lightweight and integrated design of nuclear shielding material systems. Here, a simple crosslinking method was proposed to control the crosslinking degree and crystallinity to prepare UHMWPE‐based shielding materials with excellent high‐temperature mechanical properties and irradiation endurance properties. The enhancement mechanisms of mechanical properties, irradiation endurance properties and shielding properties were revealed. Meanwhile, the γ‐rays and neutrons shielding properties were studied using Geant4. When the crosslinking degree was 20.62 × 10−3 g/mol and the crystallinity was 12.13%, UHMPE‐based shielding material with optimal overall performance was obtained. Compared with the un‐crosslinked control sample, the tensile strength and elongation at break at room temperature, 70 and 90°C were 22.3 MPa (48.90% increased) and 8.43% (154.68% increased), 8.65 MPa (105.46% increased) and 6.35% (154.00% increased), 7.48 MPa (128.75% increased) and 6.2% (89.60% increased), respectively. The vicat softening temperature and maximum thermal deformation temperature were enhance 4.20 and 6.56°C when the crosslinking degree was 27.51 × 10−3 g/mol and the crystallinity is 10.83%. Our work provided a feasible method to increase the upper temperature limit and broaden the application range of PE‐based nuclear shielding materials.

A predictive theory on thermal runaway of ultrahigh capacity lithium-ion batteries

Ultrahigh capacity lithium-ion batteries (LIBs) with prudent safety measures are key to future transportation. The undesirable thermal events such as thermal runaway (TR) in LIBs can pose a direct risk to battery life and the consumers. In the present study, a set of new TR criteria are established by closely inspecting the relation between the rate of heat generation and dissipation to anticipate the TR at an early stage. From the proposed criteria, three alarming temperatures prior to TR are identified, such as the safe temperature limit TE (an intersection between heat generation curve and heat removal line), the maximum temperature limit TM (where second derivative of heat generation is zero), and the low temperature TC from the Semenov theory. For a safer battery operation, both the low and upper limit temperatures have to remain below the safety zone, i.e. TM < TE with TC < TE. The criteria are validated by implementing them on the ultrahigh capacity LIBs, which are subjected to the thermal abuse, wherein the rate of heat generation was determined from calorimetry. The state TM < TE indicates the first precursor to TR where a controlled measure can be taken to prevent the runaway. However, TE ≤ TM regarded as the critical state during which a self-sustaining reaction involving delithiated nickel-rich cathode, intercalated anode, and dissociated electrolyte progresses, resulting in an irreversible TR in the system. The validity of the proposed criteria is demonstrated, while additional work is considered in a broad class of batteries subjected to thermal abuse conditions for establishing a safety margin of operation.

Solubility of Lanthanum in Liquid Alloys with Gallium and Indium

The solubility of lanthanum in indium and Ga–In alloys containing 21.8, 40 and 70 wt. % In was determined experimentally at temperatures up to 1081 K. The low temperature limit depended on the melting point of the alloy. The solubility was measured using isothermal saturation and high-temperature filtration methods. The phase composition of solid intermetallic compounds formed in the ternary La–Ga–In systems of various compositions was determined by X-ray diffraction. Activity coefficients of lanthanum in the alloys based on gallium, indium and three Ga–In mixtures (21.8, 40 and 70 wt. % In) were calculated. Temperature dependencies of thermodynamically possible separation factors for the uranium/lanthanum couple in “LiCl–KCl–CsCl melt–liquid alloy” systems were derived for various gallium–indium alloys.

Applicability Evaluation of Natural Gas State Equations at Low Temperatures

The paper analyzes the possibility of operating range expanding of natural gas state equations for low temperatures. The state equations of natural gas and methods of estimating the compressibility factor, entrenched in modern national and international standards, were analyzed. It has been shown that the range of their applicability is limited to a temperature value of 250 K, however, these temperature limitations is not restricted bystate equations directly butstipulated by the lack of reliable data about natural gas compressibility factor values at temperatures below 250 K and methods for complementary errorcalculation that may arise. The results of comparison of values of natural gas compressibility factor as a function of temperature at pressure of 1.3 and 6 MPa calculated by means of the most widely used state equations are presented. It was found that the results of the calculation according to the considered methods have satisfactory convergence within the range of 220 K, that generally confirms the applicability of modern state equations for low temperatures. In its turn, the effect of assumptions applied nowadays to definegas volume flow rateon flow metering error showed that application of substitutive compressibility values may result in significant complementary systematic error. This indicates the practicability of expanding the database of compressibility factor values for natural gas for low temperatures, as well as developmentof a standard to assess the value of the corresponding complementary error.

Spontaneous symmetry breaking in the BFSS model: analytical results using the Gaussian expansion method

We apply the Gaussian expansion method to the BFSS matrix model in the high temperature limit. When the (Euclidean) BFSS action is expanded about a Gaussian ansatz, it is shown that the SO(9) symmetry is spontaneously broken, analogous to what happens in the IKKT model. The analysis of the free energy, using the set of gap equations which determines the width of the Gaussian terms, is sufficient to show that this symmetry breaking happens only when the fermionic terms are included and is absent in the bosonic case.