Negative Temperatures Research Articles

Landau damping effects on dust ion-acoustic solitary waves in a nonthermal pair-ion plasma

The Landau damping effects on the nonlinear propagation of dust ion-acoustic solitary waves (DIASWs) are studied in an electron-free unmagnetized collisionless dusty pair-ion plasma. The two species of nonthermal ions (positive and negative) are described by the kinetic Vlasov equations, whereas the massive charged dust grains form only the background plasma. Using the multi-scale reductive perturbation technique generalized for the applications to the Vlasov equation, we derive a modified Korteweg–de Vries (KdV) equation that governs the evolution of DIASWs with the effects of linear resonance, in particular, linear Landau damping. The properties of the phase velocity and the Landau damping rate of DIASWs are studied with the effects of positive and negative-ion nonthermality parameters ( α p , α n ), the ratios of the positive to negative ion masses (m) and temperatures (T) as well as the dust to negative-ion number density ratio (δ). It is found that, depend on the degree of positive to negative ion mass ratios (m), both of damped and growing oscillations occur in a collisionless dusty pair-ion plasma due to the resonance phenomena between the wave and the nonthermal particles of the system. The properties of the decay rates of the amplitude of the KdV soliton with a small effect of Landau damping are also studied with the above system of parameters. The results may be useful for understanding the localization of solitary pulses and associated resonance damping and/or growing oscillations of the wave in laboratory and space plasmas, in which the number density of free electrons is much smaller than that of ions and highly charged heavy, micron seized dust grains.

Steady-state quantum thermodynamics with synthetic negative temperatures

A bath with a negative temperature is a subject of intense debate in recent times. It raises fundamental questions not only on our understanding of negative temperature of a bath in connection with thermodynamics but also on the possibilities of constructing devices using such baths. In this work, we study steady-state quantum thermodynamics involving baths with negative temperatures. A bath with a negative temperature is created synthetically using two baths of positive temperatures and weakly coupling these with a qutrit system. These baths are then coupled to each other via a working system. At steady state, the laws of thermodynamics are analyzed. We find that whenever the temperatures of these synthetic baths are identical, there is no heat flow, which reaffirms the zeroth law. There is always a spontaneous heat flow for different temperatures. In particular, heat flows from a bath with a negative temperature to a bath with a positive temperature which, in turn, implies that a bath with a negative temperature is “hotter” than a bath with a positive temperature. This warrants an amendment in the Kelvin-Planck statement of the second law, as suggested in earlier studies. In all these processes, the overall entropy production is positive, as required by the Clausius statement of the second law. We construct continuous heat engines operating between positive and negative temperature baths. These engines yield maximum possible heat-to-work conversion efficiency, that is, unity. We also study the thermodynamic nature of heat from a bath with a negative temperature and find that it is thermodynamic work but with negative entropy. Published by the American Physical Society 2024

Justification of usability of the heat accumulator of phase transition in vehicles’ engines pre-start warming-up procedure

BACKGROUND: The trend of activity increase in exploration of transpolar areas has been observed for recent years. Negative temperatures, the key feature of the North, have a negative impact on state of piston engines of on-ground transport. In engine’s cylinders, the process of transition of liquid fuel in gaseous state goes before the mixture ignition. Negative temperatures affect the phase transition process and impede the working body homogenization. Therefore, engine pre-start warming-up procedure goes before successful engine start. Existing typical methods of pre-start warming-up demand fuel consumption and, generally, significant staff resources. Achievements of modern science offer new technologies for solving the issues of warming-up procedures based on accumulating, storage and deployment of heat energy produces by an engine during its operation. AIM: Justification of usability of the heat accumulator of phase transition in pre-start warming-up procedure for vehicles’ engines operating in conditions of negative temperatures of cold climate. METHODS: Numerical values of heat accumulator charging period depending on temperature of heat-accumulating material at various initial temperatures of coolant as well as values of the discharging period depending on temperature of heat-accumulating material at various coolant rates were defined experimentally. High-density polyethylene was used as a heat-accumulating material. RESULTS: As a result of the described experiment, curves of heat accumulator charging period depending on heat-accumulating material temperature at various initial temperatures of coolant and curves of heat accumulator discharging period depending on coolant temperature at various coolant rates were built. CONCLUSIONS: It is found that the heat accumulator of phase transition with high-density polyethylene as a heat-accumulating material can be used for improving the reliability of vehicles’ piston engine start in conditions of negative temperatures of cold climate.

Using Acoustic Emission Pulses to Assess the Ductile–Brittle Transition Temperature of Aluminum Matrix Composites at Negative Temperatures

Using Acoustic Emission Pulses to Assess the Ductile–Brittle Transition Temperature of Aluminum Matrix Composites at Negative Temperatures

Assessment of the Nutritional Potential and Resistance to Oxidation of Sea Buckthorn and Rosehip Oils

Cold-pressed oils from non-typical materials, such as wild rose and sea buckthorn, should meet certain requirements to be approved for consumption. The aim of this study was to evaluate the nutritional potential and selected quality parameters with particular emphasis on oxidative stability of two commercially available cold-pressed oils: rose hip oil and sea buckthorn oil. The fatty acid composition, including nutritional indexes (polyunsaturated fatty acid/saturated fatty acid ratio PUFA/SFA; atherogenicity index IA is as follows: hypocholesterolemic/hypercholesterolemic index HH; health-promoting index HPI), positional distribution of fatty acids, melting profile and oxidative stability were analyzed. The tested oils were characterized by a high content of unsaturated fatty acids, which were mainly represented by oleic and linoleic acids. In the case of one of the analyzed rosehip oil oils (R1), α-linolenic acid was also found at the level of 26%, which contributed to obtaining the recommended ratio of omega-6 to omega-3 fatty acids. The lowest value of IA and the highest values of HH and HPI were also recorded for R1 rosehip oil. This oil was also characterized by the highest resistance to oxidation, as indicated by induction times measured at various temperatures. The distribution of fatty acids in triacylglycerols molecules in the analyzed oils was typical for vegetable oils. In the case of tested oils, similar melting profiles with endothermic peaks recorded at negative temperatures, which resulted from the presence of triacylglycerol fractions with a high proportion of mono- and polyunsaturated fatty acids, were observed.

Studying the effects of the butadiene rubber and nitrile butadiene rubber ratio on the elastomers properties

In this study the influence of the content of SKD-B butadiene rubber and BNKS-18 AMN nitrile rubber in the blend on the properties of the resulting elastomers is investigated. The combination of frost-resistant and aggressive media resistant rubbers in the blend allows to adapt the properties of vulcanizates to the required operating conditions. The research revealed that the level of physical and mechanical properties, aggressive media resistance and frost resistance depend on the ratio of rubbers. The study of properties of elastomers revealed two glass transition temperatures and two thermal transitions at negative temperatures corresponding to nitrilebutadiene and butadiene rubbers. The phase morphology of elastomers, characteristic for butadiene nitrile or butadiene rubbers in dependence on their ratio in the blend, was investigated by electron microscopy. Based on the developed elastomer, dust covers for CV-joints were produced. They were tested in real operating conditions in the temperature range from –52 to 33°C.

Performance of far forward iceless blood storage containers in controlled cold environments.

The Golden Hour Box (GHB), an iceless blood container designed for transfusion closest to the point of injury, is used by military medical teams in remote damage control resuscitation. While its performance is well-established in hot environments, it remains underexplored in cold conditions, a significant consideration in emerging global conflict zones. Four GHBs were preconditioned at +4°C or +18°C for 8 h and subsequently exposed to controlled laboratory simulated temperatures of -5, -15, and -25°C for 100 h. The study focused on their capability to maintain an internal temperature between +2 and +6°C, the recommended range for red blood cells unit storage and transport, using calibrated sensors for precise monitoring. When exposed to negative Celsius temperatures, GHBs showed varied performance depending on preconditioning temperatures. When preconditioned at +4°C, GHBs maintained an internal temperature within the target range (+2 to +6°C) for 100 h at -5°C, 52 ± 1 h at -15°C, and 29 ± 4 h at -25°C. In contrast, the internal temperature of GHBs preconditioned at +18°C exceeded this range in less than 30 min, then dropped below 2°C more rapidly than those preconditioned at +4°C, occurring within 20 ± 2 h at -15 and 13 ± 1 h at -25°C. The GHB, when properly preconditioned, effectively maintains internal temperatures suitable for blood product transport in extreme cold. Future research, including analyses of blood performances, is still needed to validate these results in more realistic operational conditions for use in cold environments.

Confectionery products stored in permafrost conditions

Industrial development of the Arctic territories is a crucial direction in the development of our country. Expanding the market for confectionery products requires increasing their safety in various climatic conditions, which is only possible by ensuring quality indicators that guarantee their specified shelf life. Studies of confectionery products stored in conditions of unregulated negative temperatures of permafrost, according to organoleptic, physico-chemical and microbiological quality indicators, have been conducted. “Iris Kiss-Kiss” candies, “Strawberry” cookies, homemade crackers, biscuits, and chocolate were stored at unregulated low temperatures. In cookies, crackers, and biscuits, a foreign odor and rancid taste caused by oxidation products of the fat fraction were detected. As for chocolate after storage, heavy bloom and significant changes in structure and consistency were revealed. The moisture content of the chocolate increased. Storage conditions at low temperatures and high humidity increase the risk of microorganism development and microbiological spoilage. The results obtained allow concluding that long-term storage of confectionery products is possible under unregulated low temperatures.

TESTING OF D16T DURALUMIN SAMPLES UNDER STATIC LOADING USING THE ACOUSTIC EMISSION METHOD

Tests of samples made of D16T duralumin were carried out under static loading until failure under normal conditions, at positive and negative temperatures. Information was recorded using the acoustic emission method. In this case, a stable location of signals from defects corresponding to the beginning of sample destruction was observed. It was shown that at a low temperature of –50 oС the number of recorded signals increased, but the energy of the high-frequency component of the AE signals decreased, and the maximum energy was in the frequency band 550…600 kHz. At a temperature of +80 oC, the number of recorded signals decreased. Wavelet scalograms were constructed at various temperatures and loads. The sensitivity of the main informative parameters of acoustic emission signals, which made it possible to determine the onset of destruction of the sample material, was analyzed.

Shear strength model of unsaturated frozen soil based on soil freezing characteristic and soil water characteristic

The strength characteristics of unsaturated soil after freezing significantly influence the safety of engineering construction in frozen soil regions. In this study, the soil freezing characteristic curve (SFCC) and soil water characteristic curve (SWCC) of unsaturated lean clay were tested. Based on the similarity between SFCC and SWCC, the unfrozen water content of SFCC was used to replace the water content of the SWCC to obtain the expression for soil suction under different negative temperatures. A shear strength model of unsaturated frozen soil was established. According to unsaturated triaxial tests under different conditions, the effectiveness of the established unsaturated soil shear strength model was verified. The test results show that in the rapid freezing stage of the SFCC, the volumetric unfrozen water content with an initial matrix suction of 57 kPa exhibited the largest rate of change. The stress-strain curve of soil at positive temperature is strain hardening type, and that at negative temperature presents different types under the influence of temperature, initial matrix suction and confining pressure. The effective cohesion and internal friction angle of soil varied significantly under the influence of temperature and initial matrix suction. When the initial matrix suction was constant, the unsaturated shear strength of the soil increased nonlinearly with a decrease in temperature. When the temperature was ≥−5 °C, the shear strength increased with an increase in initial matrix suction, but decreased when the temperature was ≤−5 °C. The model fitting results were consistent with the measured results of the unsaturated triaxial test, which verifies the validity of the model. This research can provide a reference for studying the mechanical characteristics of unsaturated frozen soil under negative temperature.

Study on the Compressive and Flexural Properties of Coconut Fiber Magnesium Phosphate Cement Curing at Different Low Temperatures.

The incorporation of coconut fiber (CF) into magnesium phosphate cement (MPC) can effectively improve upon its high brittleness and ease of cracking. In practical engineering, coconut fiber-reinforced magnesium phosphate cement (CF-MPC) will likely work in cold environments. Therefore, it is essential to understand the effects of various types of low-temperature curing on CF-MPC performances, but there are very few studies in this area. In this study, the static compression and three-point bending test were utilized to examine the compressive and flexural characteristics of CF-MPC with various CF contents and different negative curing temperatures. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were conducted to observe the impact of low-temperature maintenance on the structure and hydration reaction of the specimens. The results indicate that CF-MPC curing at low temperatures was more prone to cracks during compression and bending, while the appropriate amount of CF could enhance its plastic deformation capability. The CF-MPC's compressive and flexural strength declined as the curing temperature dropped. Moreover, with the rise in CF content, the samples' compressive strength also tended to fall, and there was a critical point for the change in flexural strength. In addition, MPC's primary hydration product (MgKPO4·6H2O) decreased with a drop in curing temperature, and more holes and fractures appeared in CF-MPC.

Insufficient Cold Resistance as a Possible Reason for the Absence of Darkling Beetles (Coleoptera, Tenebrionidae) in Pleistocene Sediments of Siberia.

The level of diversity and abundance of darkling beetles (Coleoptera, Tenebrionidae) is the main difference between the late Pleistocene and modern insect faunas of arid regions. In the Pleistocene assemblages they are extremely rare, whereas in the modern ones they predominate. It is assumed that the reason for their rarity in fossil entomological complexes is their lack of cold resistance. The supercooling points (SCP) and low lethal temperatures (LLT) of adults from five species of Altai darkling beetles that overwinter in the soil and larvae from one such species were measured in the laboratory. All beetles supercooled at negative temperatures but could not survive freezing, with the average SCP of the most cold-resistant species between -25.7 and -21.7 °C (Bioramix picipes, Anatolica dashidorzsi, and Penthicus altaicus). However, 50% of the individuals from different species in the experiment died after exposure during two days at temperatures ranging from -22 to -20 °C. The focal species are distributed in parts of Central Asia with an extreme continental climate, and the temperatures measured in the soil of these natural areas turned out to be lower than or close to the limit of cold resistance of the beetles. Overwintering of darkling beetles is therefore only possible in areas with deep snow: in hollows, under bushes, and under large cereals. Darkling beetles with poor cold resistance could not have existed in the colder climate of the late Pleistocene, which explains their absence from fossil fauna.

Study of the properties of pectin substances for the production of healthy food products

The article is devoted to the research in the field of using frozen grapes in the technology of production of products for a healthy diet. The main objectives of the research are to substantiate technological significance of frozen table grapes for the development of functional desserts. To study the influence of negative temperatures on the gelling and complexing ability of pectin substances in frozen grapes with subsequent defrosting of the raw material. The object of the research was table grapes of 5 varieties grown in the Krasnodar region. Experimental studies of technological and biochemical parameters of fresh and frozen grapes in order to study and confirm the use of grapes in the food industry for the development of desserts with different functional areas were carried out on the territory of the Kuban State Agrarian University named after I.T. Trubilin in the laboratories of the Faculty of Food Production and Biotechnology. Biochemical methods of analysis, generally accepted in the food industry, were used as research tools. It is well known that low-temperature freezing helps to maximize the preservation of the nutritional value of plant materials, however, in the health food industry, recipes and technologies for processing frozen grapes are practically not represented. An information search of scientific literature has shown that there are no studies on the study and selection of grape varieties for canning by freezing and the production of functional products from defrosted raw materials, which indicates the need to conduct experimental studies, study the kinetics of the chemical and biochemical composition of fresh, frozen and defrosted grapes in order to differentiate raw materials for the production of desserts with different functional orientations. Using biochemical analysis methods, it has been established that, regardless of varietal characteristics, the main components of the chemical composition of grapes are preserved during freezing and further defrosting.

Warming Climate-Induced Changes in Lithuanian River Ice Phenology

Due to rising surface air temperatures, river ice is shrinking dramatically in the Northern Hemisphere. Ice cover during the cold season causes fundamental changes in river ecosystems and has important implications for nearby communities and industries. Changes caused by climate warming, therefore, affect the sustainability of key resources, livelihoods, and traditional practices. Thus far, too little attention has been paid to research into the phenomenon of river ice in the Baltic States. Since the observational data of the last sixty years are currently available, we took advantage of the unique opportunity to assess ice regime changes in the gauged rivers by comparing two climatological standard normals. By applying statistical methods (Mann–Kendall, Pettitt, SNHT, Buishand, von Neumann, and Wilcoxon rank sum tests), this study determined drastic changes in ice phenology parameters (freeze-up date, ice break-up date, and ice cover duration) of Lithuanian rivers in the last thirty-year period. The dependence of the selected parameters on local climatic factors and large-scale atmospheric circulation patterns was identified. It was established that the sum of negative air temperatures, as well as the North Atlantic Oscillation, East Atlantic, and Arctic Oscillation indices, have the greatest influence on the ice regime of Lithuanian rivers.

Some Remarks on the Phase Transformation of Gas Hydrates in Porous Sediments at Negative Celsius Temperatures

The article presents a solution to the problem of the phase transition of methane hydrate — methane-gas + ice in porous hydrate-containing sediments at a negative Celsius temperature in the medium. The numerical solution of the resulting system of differential equations of piezoand thermal conductivity makes it possible to effectively simulate the change in pressure and temperature in both time and space in a medium of any dimension during its heating or decompression. In this case, the medium is not subdivided into parts with varying phase states of methane hydrate. Instead, its sediment substance is considered as a single entity, with its physical properties changing in magnitude when the hydrates undergo phase transformation. As an example, the problem of the thermobaric regime of a heating spherical cavern containing ice, hydrate and free methane has been solved. This cavern is situated within a continuous gas-tight underground ice. The solution shows that although the temperature of the sphere surface increases considerably, the decomposition of hydrate only occurs in an extremely thin shell located directly between the surface and the displaced inward phase boundary.Over time, the stability conditions of hydrates establish anew but at a higher gas pressure and medium temperature. This phenomenon of severely limited decomposition of the hydrate in a closed gas-insulated space, nevertheless leading to an increase in pressure in it, is, apparently, the basic process that provides the “self-preservation” of methane hydrates.

A Binary Medium Constitutive Model for Frozen Solidified Saline Soil in Cold Regions and Its Fractal Characteristics Analysis

In addressing the issue of strength degradation in saline soil foundations under the salt-freeze coupling effects, a binary medium constitutive model suitable for un-solidified and solidified frozen saline soil is proposed considering both bonding and friction effects. To verify the validity of the constitutive model, freezing triaxial tests are carried out under different negative temperatures, confining pressures, and water contents. The pore structure and fractal characteristics of saline soil are analyzed using mercury intrusion porosimetry (MIP) and the fractal dimension D qualitatively and quantitatively, which shed light on the strength enhancement mechanism during the solidification of frozen saline soils. The results show that the constitutive model for frozen solidified saline soil based on binary medium theory aptly captures the stress–strain relationship before and after the solidification of frozen saline soil. The stress–strain relationship of frozen saline soil before and after solidification can be delineated into linear elasticity, elastoplasticity, and strain-hardening or -softening phases. Each of these phases can be coherently interpreted through the binary medium constitutive model. The un-solidified and solidified frozen both show pronounced fractal characteristics in fractal analysis. Notably, the fractal dimension D of the solidified saline soil exhibits a significant increase compared to that of un-solidified ones. In Regions I and III, the values of D for solidified saline soil are lower than those for untreated saline soil, which is attributed to the filling effect of hydration products and un-hydrated solidifying agent particles. In Region II, the fractal dimensions DMII and DNII of the solidified saline soil exhibit a “non-physical state”, which is mainly caused by the formation of a significant number of inkpot-type pores due to the binding of soil particles by hydration products.

Negative-temperature pressure in black holes

The concept of negative temperature is unique to quantum physics and describes systems that are hotter than any positive-temperature system. For decades, negative temperatures have been shown in a number of spin systems, but experiments only recently demonstrated atomic ensembles with negative temperatures in their motional degrees of freedom. An observed behavior of such negative-temperature ensembles is that despite highly attractive forces between an arbitrary number of particles, there is a self-stabilization against collapse. Negative temperatures are only possible in quantum systems because there exists upper bounds on the energy of particles —a property not found in classical physics. Here we consider whether event horizons set up similar upper limits within black holes, giving rise to negative-temperature systems just within event horizons. Combining black-hole thermodynamics with experimentally observed negative-temperature effects could imply a quantum-based outward pressure in black holes.

Estimation of the temperature of the ductile-brittle transition of aluminum matrix composite materials at negative temperatures using classification of acoustic emission signal pulses

The results of experiments on assessing the mechanical properties, in particular the temperature of the ductilebrittle transition of aluminum matrix composite materials at negative temperatures using the classification of acoustic emission signal pulses, are presented. It is established that this transition is absent at temperatures down to –100 °C and, therefore, it is possible to use aluminum matrix composite materials for the manufacture of suspension elements for equipment operating in Arctic and Antarctic conditions. Keywords aluminum matrix composite materials, mechanical properties, temperature, ductile-brittle transition

Prospects for the use of lithium bromide and lithium chloride absorption heat pumps of the step-up type in heat power engineering and industry

The article discusses the possibilities of using a step-up absorption heat pumps in autonomous heating systems and in industry. A system of autonomous heating with a step-up heat pump is proposed, where the energy source is geothermal water with a temperature of 40 °C, and the surrounding winter air with negative temperatures is used to remove heat from the heat pump. Calculations were made of heat pump cycles for working fluids – LiBr and LiCl absorbents. As a result of cycle calculations, energy efficiency indicators were determined - transformation coefficients. The transformation coefficients for LiBr and LiCl are comparable and range from 0.46 to 0.48. Thus, it has been established that the use of LiCl as an alternative working fluid is promising.

Study of Using Electrical Heavy Concrete in the Improvement of Urban Areas

In regions with negative average daily temperatures, the development of the construction sector, including transport infrastructure facilities, requires increasing the efficiency of heating systems and deicing systems, while reducing the material consumption of their production. In the study, samples with dimensions of 70x70x70 mm and products with dimensions of 500 × 500 × 50 mm were made from electrically conductive coarse aggregate concrete. Additives of industrial soot suspension - 7% and carbon fiber - 1% were used as modifiers. The additives were introduced individually and in combination. The developed compositions ensure the mechanical compressive strength of concrete on the 28th day of more than 40 MPa. The combined use of modifiers allows the surface of the product to be heated from 21°C to 34°C within 30 minutes. Physicochemical studies of the compositions conducted after 3 cycles of heating and cooling showed optimal homogenization of carbon-containing materials and the absence of chemical interaction between carbon fiber and components of the mineral matrix. The obtained indicators of electrical and mechanical properties prove that it is possible to manufacture products based on the optimal composition that provide repeated heating and are optimal for use in the improvement of urban areas.