Freezing Temperature Research Articles

Understanding the Topology Freezing Temperature of Vitrimer-Like Materials through Complementary Structural and Rheological Analyses for Phase-Separated Network.

Vitrimers are sustainable cross-linked polymers characterized by an associative bond exchange mechanism within their network. A well-known feature of vitrimers is the Arrhenius dependence of the viscosity or relaxation time. Another important aspect is the existence of a topology-freezing temperature (Tv), which represents a transition between the viscoelastic solid state and the malleable viscoelastic liquid state. Various methods, including viscosity-temperature plots and temperature-ramp creep (or dilatometry), have been proposed for determining the Tv. In this study, we complementarily employ X-ray scattering-based structural analysis and rheological analysis to assign Tv in phase-separated vitrimer-like materials undergoing trans-N-alkylation bond exchange. Note that the trans-N-alkylation progresses via the dissociative bond exchange pathway, whereas our previous studies demonstrated that the temperature-dependence of relaxation time followed the Arrhenius dependence, which was the reason for the classification as a vitrimer-like material. Specifically, we identify Tv as the temperature at which an anomalous increase in domain distance occurs during the rubbery state in the structural analysis. In the rheological analysis, Tv corresponds to the transition temperature marking the shift from the Williams-Landel-Ferry dependence to the Arrhenius dependence in the shift factors used to create master curves for frequency sweep rheology data. Importantly, both methods yield nearly the same Tv, validating the accuracy of the proposed assignment and, thus, providing valuable insights into the specific properties of vitrimers.

Pressure-dependent magnetism of the Kitaev candidate Li2RhO3

We use magnetization measurements under pressure along with ab initio and cluster many-body calculations to investigate magnetism of the Kitaev candidate Li2RhO3. Hydrostatic compression leads to a decrease in the magnitude of the nearest-neighbor ferromagnetic Kitaev coupling K1 and the corresponding increase in the off-diagonal anisotropy Γ1, whereas the experimental Curie-Weiss temperature changes from negative to positive with the slope of +40 K/GPa. On the other hand, spin freezing persists up to at least 3.46 GPa with the almost constant freezing temperature of 5 K that does not follow the large changes in the exchange couplings and indicates the likely extrinsic origin of spin freezing. Magnetic frustration in Li2RhO3 is mainly related to the interplay between ferromagnetic K1 and antiferromagnetic Γ1, along with the weakness of the third-neighbor coupling J3 that would otherwise stabilize zigzag order. The small J3 distinguishes Li2RhO3 from other Kitaev candidates.

Dual-modality flow phantom for ultrasound and optical flow measurements.

As ultrasound-compatible flow phantoms are devised for performance testing and calibration, there is a practical need to obtain independent flow measurements for validation using a gold-standard technique such as particle image velocimetry (PIV). In this paper, we present the design of a new dual-modality flow phantom that allows ultrasound and PIV measurements to be simultaneously performed. Our phantom's tissue mimicking material is based on a novel hydrogel formula that uses propylene glycol to lower the freezing temperature of an ultrasound-compatible poly(vinyl) alcohol cryogel and, in turn, maintain the solution's optical transparency after thermocycling. The hydrogel's optical attenuation {1.56 dB cm-1with 95% confidence interval (CI) of [1.512 1.608]}, refractive index {1.337, CI: [1.340 1.333]}, acoustic attenuation {0.038 dB/(cm × MHzb), CI: [0.0368 0.0403]; frequency dependent factor of 1.321, CI: [1.296 1.346]}, and speed of sound {1523.6 m s-1, CI: [1523.8 1523.4]} were found to be suitable for PIV and ultrasound flow measurements. As an application demonstration, a bimodal flow phantom with spiral lumen was fabricated and used in simultaneous flow measurements with PIV and ultrasound color flow imaging (CFI). Velocity fields and profiles were compared between the two modalities under a constant flow rate (2.5 ml s-1). CFI was found to overestimate flow speed compared to the PIV measurements, with a 14%, 10%, and 6% difference between PIV and ultrasound for the 60°, 45°, and 30° angles measured. These results demonstrate the new phantom's feasibility in enabling performance validation of ultrasound flow mapping tools.

Relating Photoperiod and Outdoor Temperature With Sleep Architecture in Patients With Neuropsychiatric Sleep Disorders.

While artificial light in urban environments was previously thought to override seasonality in humans, recent studies have challenged this assumption. We aimed to explore the relationship between seasonally varying environmental factors and changes in sleep architecture in patients with neuropsychiatric sleep disorders by comparing two consecutive years. In 770 patients, three-night polysomnography was performed at the Clinic for Sleep & Chronomedicine (St. Hedwig Hospital, Berlin, Germany) in 2018/2019. Sleep times were adjusted to patients' preferred schedules, patients slept in, and were unaware of day-night indicators. Digital devices and clocks were not allowed. Days were spent outside the lab with work or naps not allowed. After exclusions (mostly due to psychotropic medication), analysis was conducted on the second PSG-night in 377 patients (49.1 ± 16.8 year; 54% female). Sleep parameters were plotted as 90-day moving-averages (MvA) across date-of-record. Periodicity and seasonal windows in the MvA were identified by utilizing autocorrelations. Linear mixed-effect models were applied to seasonal windows. Sleep parameters were correlated with same-day photoperiod, temperature, and sunshine duration. The MvA of total sleep time (TST) and REM sleep began a 5-month-long decline shortly after the last occurrence of freezing 24-h mean temperatures (correlation of TST between 2018 and 2019 at 2-month lag: rs361 = 0.87, p < 0.001; maximum peak-to-nadir amplitude: ΔTST ~ 62 min, ΔREM ~ 24 min). The MvA nadirs of slow wave sleep (SWS) occurred approximately at the autumnal equinox (correlation between 2018 and 2019: rs361 = 0.83, p < 0.001). Post hoc testing following significant linear mixed-effect model indicate that TST and REM sleep were longer around November till February than May till August (ΔTST = 36 min; ΔREM = 14 min), while SWS was 23 min longer around February till May than August till November. Proportional seasonal variation of SWS and of REM sleep as percentages of TST differed profoundly (SWS = 31.6%; REM = 8.4%). In patients with neuropsychiatric sleep disorders living in an urban environment, data collected in 2018 show similar patterns and magnitudes in seasonal variation of sleep architecture as the 2019 data. Interestingly, whereas SWS patterns were consistent between years with possible links to photoperiod, annual variations of TST and REM sleep seem to be related to times of outside freezing temperature. For generalization, the data need to be confirmed in a healthy population. No clinical trial was registered.

Variation of postharvest quality attributes and aroma development of Xiaobai apricot during storage at near freezing temperature

Variation of postharvest quality attributes and aroma development of Xiaobai apricot during storage at near freezing temperature

Закономерности массообменных процессов при криоконцентрировании обезжиренного молока

Low-temperature concentration of milk and dairy products is a prospective alternative to such traditional concentration methods as evaporation or membrane technologies. This energy-effective method preserves the native properties of dairy raw materials. In this research, the kinetics of moisture freezing made it possible to determine the effect of time, temperature, and composition on the amount of frozen ice on the cooled surface. The study featured the main physical and chemical parameters of milk, i.e., water, fat, protein, and solids. Chromel-copel thermoelectric converters were used to identify the freezing temperature. Experimental laboratory equipment made it possible to describe the kinetics of low-temperature concentration. The ice growth rate curves were similar and not linear at temperatures between –2 and –8°C. At all temperature conditions, the solids increased together with the freezing time as the coolant temperature went down. The experiment yielded a regression equation that revealed the mass fraction of solids in concentrated skim milk depending on the temperature and freezing time. The temperature and freezing time affected the transition rate of milk solids into ice. The coolant temperature had the greatest effect on the cryoconcentration of skim milk. When the temperature of the coolant was reduced from –2 to –8℃, it increased the share of solids in the finished product and sped up its transition into ice. The optimal temperature for milk concentration in the experimental capacitive-type crystallizer proved to be –4°C.

Proteomic Insights into the Regulatory Mechanisms of the Freezing Response in the Alpine Subnivale Plant Chorispora bungeana.

Freezing temperatures impose significant constraints on plant growth and productivity. While cold tolerance mechanisms have been extensively studied in model species, the molecular basis of freezing tolerance in naturally adapted plants remains underexplored. Chorispora bungeana, an alpine plant with a strong freezing tolerance, provides a valuable model for investigating these adaptive mechanisms. In this study, we used Tandem Mass Tag (TMT)-based quantitative proteomics to analyze C. bungeana seedlings subjected to freezing stress (-6 °C) at 6 and 30 h, identifying 302 differentially expressed proteins (DEPs) compared with controls. Our findings capture the dynamic proteomic landscape of C. bungeana under freezing stress, revealing distinct early and prolonged responses. Early responses featured upregulated proteins involved in signaling and stress protection, with no clear involvement of the ICE1-CBF pathway (ICE1: Inducer of CBF Expression 1; CBF: C-repeat Binding Factor) found in cold-acclimating plants, while calcium signaling and epigenetic modifications enabled a rapid response. Extended exposure involved DEPs in RNA modification, glutamine metabolism, and biosynthesis of polysaccharides and flavonoids, highlighting metabolic adjustments crucial for long-term adaptation. By combining protein-protein interaction (PPI) networks and functional analysis, we identified 54 key proteins validated by qRT-PCR. These findings provide comprehensive insight into freezing tolerance mechanisms, identifying candidate proteins for enhancing cold resilience in crops and mitigating agricultural cold stress impacts.

Experimental Study on the Change in Freezing Temperature During the Remediation of Pb-Contaminated Soils with Biochar

Experimental Study on the Change in Freezing Temperature During the Remediation of Pb-Contaminated Soils with Biochar

Influence of storage conditions on the stability of ozonized vegetable oils

Ozonation of polyunsaturated vegetable oils imparts antimicrobial, wound healing, and antioxidant properties, expanding their potential applications in pharmaceutical, cosmetic, and food industries. These oils have been increasingly used as natural alternatives in wound treatments due to the formation of reactive oxygen species, such as peroxides, hydroperoxides, and ozonides, during the ozonation process. This study aimed to evaluate the ozonation levels of six polyunsaturated vegetable oils (sunflower, coconut, copaiba, grape seed, olive, and rosehip), using peroxide value as an indicator. Among these, sunflower oil exhibited the highest peroxide value and was selected for detailed monitoring of the ozonation process, including infrared spectroscopy and peroxide value analyses. To assess the effects of storage, the ozonized oil was stored under three conditions: freezer (-18°C), refrigerator (4°C), and room temperature (25°C), with evaluations every 30 days over 180 days. Results demonstrated that room temperature significantly reduced the peroxide value, compromising oxidative stability, while freezer and refrigerator storage better preserved reactive species, such as peroxides, hydroperoxides, and ozonides, with the freezer offering the highest level of conservation. These storage conditions are essential to maintain the antimicrobial and wound-healing potential of ozonized oils, particularly for therapeutic applications. This study highlights the importance of adequate storage strategies to ensure the efficacy and longevity of ozonized oils, contributing to the development of high-value-added products.

Characterization and effectiveness analysis of ternary organic eutectic mixture/hybrid-nanoparticles based phase change material for cold storage applications

Abstract A novel organic ternary mixture composed of Lauric acid, Myristic acid, and Dodecanol (referred to as LMD) has been synthesized as a Phase Change Material (PCM), specifically designed for cold storage applications. Although organic PCMs are highly effective, their low thermal conductivity frequently restricts their heat transfer performance. To address this issue, a hybrid Nano-enhanced PCM (HNe-PCMs) has been developed in this study. This involved dispersing two types of nanoparticles, Graphene nanoparticles (GNP)-Al2O3 and GNP-CuO, each at a 1% weight fraction, within the LMD matrix. The thermal and chemical characteristics of developed pure LMD and HNe-PCMs were studied using Electron microscope scanning (SEM), Fourier transform infrared spectrophotometer (FTIR), x-ray diffractometer (XRD), Thermal conductivity analyser (TC), Differential scanning calorimeter (DSC), and Thermo gravimetric analyser (TGA) and explored their potential in cold storage application. Chemical and thermal characterization revealed that the freezing and melting temperatures of LMD are 8.4 ± 0.1 °C and 15.6 ± 0.1 °C, respectively, with corresponding latent heats (LH) of freezing/melting of 125.4 ± 1.8 J g−1 and 131.5 ± 1.8 J g−1. Upon incorporation of the nanoparticles, the thermal conductivities of LMD/GNP-Al2O3 and LMD/GNP-CuO were notably enhanced by 57.4% and 49.8%, respectively, compared to pure LMD. However, a slight deviation in the melting/freezing LH of 2.9% and 1.9%, and in phase change temperature of 12.1% and 7.1%, respectively, was observed for the LMD/GNP-Al2O3 HNe-PCMs compared to the pure LMD. Through effectiveness analysis, it was depicted that the LMD/GNP combined with Al2O3 exhibits a reduction of 13.94% and 12.4% in charging-discharge time compared to pure LMD. In contrast, the LMD/GNP with CuO showed a 12.73% and 10.87% reduction in these times respectively. Overall, LMD/GNP-Al2O3 emerges as a promising material for passive cold storage applications, improving thermal conductivity while preserving similar phase change characteristics to pure LMD performance.

Contact angle for theoretical parameterization of immersion freezing rate inferred from the freezing temperature

AbstractThis study derived contact angles for fifteen types of pollens, nine types of fungi, ten types of bacteria, one type of diatom, and twelve types of mineral dust for use in the parameterization of immersion freezing based on the classical nucleation theory (CNT). Our approach is to interpret freezing temperature measurement results with the stochastic nucleation concept. In this way, the abundant freezing temperature data available in the literature can be converted to contact angles that needed in the CNT parameterization for a variety of INPs. The derived contact angles compared well with values independently obtained in earlier studies based on a pure-CNT approach using laboratory nucleation rate data. The uncertainties in contact angle calculation associated with the definition of onset nucleation rate, the activation energy, and the ice-nuclei size are estimated to be about ± 1–2°, ± 1–5°, and ± 1–2°, respectively, among different ice-nucleating particles.

Multi-scale modeling of hydrogel-based concrete formed under the ambient environment and the extremely harsh environment of Mars

Hydrogel-based concretes (HBCs) are an emerging class of load-bearing composite materials consisting of inert particles joined together by micro-hydrogel joints. As HBCs can harden via sol-gel process and H2O phase changes under a freezing temperature and vacuum, they are suitable for future exterritorial constructions. Previous studies have demonstrated that the internal microstructure of the hydrogel joints in HBC varies significantly with curing temperature and air pressure, leading to variations in their mechanical properties. In this study, we present a new multi-scale model that quantitatively predicts the mechanical properties of HBC formed under different curing environments including Martian atmosphere. On the micro-scale, four representative joint microstructures are studied, including tubular, foamy, honeycomb, and tube-cased-foam joints. We experimentally studied and analytically derived the constitutive relationship between the joint force and displacement. Particularly, we determined the process of hydrogel skin peeling from the particle's surface of tubular joints based on force and energy equilibrium. On the macro-scale, we simplified the constitutive joint relationships in a linear parallel bond model (LPM) and employed them to quantify interparticle relationships in a discrete element method (DEM)-based HBC model. The Weibull distribution is used to consider the variation of tensile and shear strengths of the hydrogel joints in the DEM. The modeling results are not only validated with the experimentally acquired compressive stress-strain curves of HBC, but also accurately predict the combined influence of mix design and curing conditions on the mechanical properties.

Enhancing 3D printing accuracy of cassava starch gel through temperature-controlled freezing

Starch is an important renewable resource, however, the performance of 3D printing inks prepared from it requires improvement. This study revealed the effects of different freezing temperatures (25 °C, 4 °C, 0 °C, −20 °C, −40 °C, −80 °C) on the 3D printing accuracy of cassava starch (CS) gels in terms of starch gel properties (rheological properties, moisture distribution, submicroscopic structure) and multiscale structure (molecular size, chain length distribution, short-range ordered structure). As the freezing temperature decreased, the molecular size and the amylose (Am) content in CS gel were increased, particularly for short Am chains (X∼100–1000). These resulted in a greater orderly structure of the starch, enhancing the elastic modulus of the gel. Moreover, the lower the freezing temperature, the higher mobility of water molecules within the gel matrix after thawed, which in turn caused the reduction of gel viscosity and facilitated the smooth squeezing of the gel. After freeze-thawing at cryogenic temperatures, the above changes in CS gel properties improved the stiffness and support performance of the gel structure, thereby enhancing the 3D printing precision. This study provides insights into the development of 3D printing technology for starchy food materials, emphasizing its potential to transform the customization of starch-based food processing by enabling customized food products, enhancing texture, and offering consumers personalized food choices and improved sensory experiences.

Extension of Shelf Life of Roasted Duck by combination of Vacuum Packaging and Low Temperature Storage

A study was conducted to assess the shelf life of roasted duck under aerobic and vacuum packaging and in refrigerator (4±1° C) and freezer (-18±1° C) storage. The samples were analyzed for moisture content, pH, Thiobarbituric Acid (TBA) Value, Tyrosine value, Total Plate Count (TPC), Total Psychrophilic Count (TPSC), Yeast and Mould Count (YMC), colour, flavour and tenderness. The products showed an increasing trend in pH, TBA value, tyrosine value, TPC, TPSC and YMC during the storage period in refrigerated and freezer temperatures irrespective of the packaging methods i.e. aerobic and vacuum, whereas, the moisture content, colour, flavor and tenderness of the product followed a declining trend during storage. Though the sensory parameter scores declined during storage, but these changes were less in the vacuum packed and frozen products. The study showed that the aerobically packed roasted duck was acceptable upto 7th day and vacuum packed roasted duck was acceptable upto 14th day in the refrigerated storage. The freezer storage extended the shelf life of the roasted duck till 40th day in aerobic packaging while the combination of freezer storage and vacuum packaging extended the shelf life of the roasted duck till 60th day. These findings have significant implications for the food industry, enabling the development of strategies to extend the shelf life of roasted duck and reduce food waste.

Exploring the dynamic mechanical response and mesoscopic characteristics of typical frozen rock in Yulong Copper Mine

Dynamic mechanical characteristic testing at low temperatures was conducted for the typical porphyry and sandstone specimens of Yulong Copper Mine in Tibet, China. The stress and strain characteristics of the specimens at different temperatures were analyzed. A dynamic constitutive model was developed by considering the initial damage. Furthermore, microscopic damage characteristics during the water-saturated rock freezing process were investigated using the PFC3D software, revealing the mechanisms of frost heave damage to rocks. The results indicated that the water-ice phase transition either enhanced or deteriorated the specimen strength at low temperatures. Specifically, freezing at −10°C and −20°C enhanced the strength of sandstone. However, freezing at −10°C enhanced the porphyry specimens, and freezing at −20°C caused significant frost swelling injury. The new constitutive equation effectively fitted the dynamic stress and strain curves for both specimens, highlighting their differences. The maximum contact force and particle contact in the frozen rock PFC3D model were affected by rock and water particle deformations. The frost swelling deformation of water particles had a more pronounced impact on specimen damage and was related to the temperature. A specific freezing temperature existed at which the increase in saturated rock strength corresponded to the maximum specimen strength at that temperature.

PROPERTIES OF MONOLITHIC CEMENT CONCRETE, HARDENING AT TEMPERATURES CLOSE TO ZERO

One of the main problems of hardening monolithic cement concrete, especially in the conditions of restoration and reconstruction of various objects, is the hardening of concrete in conditions of negative temperatures. Winter concreting technologies are divided into two main methods: the thermos method, in which the temperature of the environment in which the concrete hardens, must be above zero degrees Celsius, or the use of antifreeze additives. In the last case, it is advisable to introduce antifreeze chemical additives into the concrete composition, which lower the freezing temperature of water in concrete. However, previously conducted studies are known that show that even in the case of early freezing of concrete, its quality remains high. In this case, it is necessary that the beginning of setting of the cement paste occurs before the concrete can freeze. In addition, it has been suggested that concrete hardening at low temperatures can occur without using the thermos method. The article presents the results of the influence of hardening temperature on the setting time of cement paste. It is shown how hardening conditions affect on the strength and frost resistance of concrete.

Polymer Electrolytes with High Ionic Conductivities at Freezing Temperature for Aqueous Hybrid Batteries.

Rechargeable and flexible aqueous batteries (ABs) have emerged as one of promising energy devices which is primarily due to the safety, environmental friendliness and economic efficiency. However, because of the freezing behavior of aqueous electrolytes, most ABs possess poor performance when the working temperature drops below zero. To solve this problem, a gel polymer electrolyte (GPE) with high ionic conductivity (IC) and frost-resistance is designed for aqueous Zn-Li hybrid batteries by a biomass-based polymers complex consisting of carboxyl modified sodium alginate (SA) and zwitterionic betaine (BA). Introducing iminodiacetic acid to enrich -COOH groups along the SA main chains could improve IC of the prepared GPEs to 41.27 and 20.96 mS cm-1 at 20 and -20 °C, respectively. At -20 °C, the discharge capacity of the resultant cell is two times higher than that of the liquid electrolyte-based cell, and the cell presents a capacity retention of 91.6 % after 300 charge/discharge cycles at 1 C. This proposed strategy greatly improve the IC of GPEs at freezing temperature, which is expected to broaden the practical application of GPEs in wide range of temperature.

Effect of Freezing Temperature on the Thermal, Rheological, and Gelatinization Properties of Freeze-Thaw-Dehydrated Potato Powder.

To promote the application of freeze-thaw-dehydrated (FTD) potatoes and their gels, this study aimed to investigate the effects of freezing temperature on the physicochemical and gel properties of FTD potato powder and their correlation. The results revealed that, as the freezing temperature decreased, the solubility exhibited an overall downwards trend resulting from soluble solids and amylose liberation. Owing to the better cell integrity at -20 °C, the solubility was greater than that of the other treatment groups. In contrast, the trough viscosity and melting enthalpy increased, and the final viscosity, and setback first increased but then decreased. Regarding the properties of the FTD potato powder gel, the storage modulus, loss modulus, hardness, adhesiveness, chewiness, and consistency first increased but then decreased with decreasing freezing temperature. At a moderate freezing temperature (-20 °C), the solubility and stability of the FTD potato powder were well maintained, and the final viscosity, setback, and hardness reached their highest values. Correlation analysis revealed that, with decreasing freezing temperature, the amount of FTD potato powder initially increased, followed by a decrease in the final viscosity and setback. This trend was positively correlated with the hardness of the FTD potato gel (r = 0.98, r = 0.93).

Synthesis of complex esters of 2,2-dimethylolpropane and their study as high temperature resistant lubricants

Complex esters of 2,2-dimethylolpropane with caproic, adipic, sebacic acids and methyl, hexyl, 2-ethyl hexyl alcohols were synthesized according to a 3-stage scheme, they were studied as new high temperature resistant lubricants. It was found that these esters have a viscosity of 10.13–16.12 mm2/s at 100 oC temperature, a high viscosity index of 130–145 units, an flash point of 240–274 oC, a low freezing temperature of minus 40- minus 45 oC. It was determined as a result of determination of thermooxidation stabilities that after oxidation, they are 2.83–3.40 mg KOH/g acid value, 0.036–0.045 mass % precipitate insoluble in isooctane, 0.023–0.040 mg/cm2 corrosion at AK-4 electrode, and 0.040–0.065 mg/cm2 corrosion on ШХ-15 electrode, 0.40–0.55 % mass volatility. During the study of the lubricating properties of esters, the main indicators were found to be: the amount of critical load Pc H=800–950, the diameter of the wear circle Dw=0.40–0.55 mm, P=196H. Taking into account the above-mentioned indicators, it can be concluded that complex esters of 2,2-dimethylolpropane (neopentylglycol (NPG)) may be recommended as high temperature resistant special purpose oils, as a dispersion medium of high temperature and pressure resistant plastic lubricants, as a component that improves the operational properties of other oils.

Increased Freezing Temperature of Clouds Over China Due To Anthropogenic Pollution

AbstractThe temperature for cloud glaciation importantly determines the initialization of precipitation and lifetime of clouds. The role of anthropogenic pollutants as ice nucleating particles (INPs) to determine the cloud glaciation remains uncertain. In this study, based on satellite radar and lidar observations, the clouds either in pure liquid or mixed‐phase with liquid top were statistically analyzed over China during 2006–2019, to obtain the transition freezing temperature (T*) of cloud top where mixed‐phase becomes more frequent than pure water, with further validation by the aircraft in situ measurements. Anthropogenic pollution was observed to raise T* up to −9°C, significantly increasing it by approximately 5°C per unit of aerosol optical depth. The results provide regional‐scale evidence that anthropogenic pollutants act as efficient INPs, increasing the freezing temperature of mixed‐phase clouds.