Freezing Temperature Research Articles

Silicon and Potassium-Induced Modulations in Leaf Carbohydrate Metabolism Confer Freezing Tolerance in Satsuma Mandarin

Freezing temperatures are a severe issue in North Florida, primarily due to occasional cold snaps and frost events in winter and early spring that cause damage to citrus groves, resulting in reduced fruit yield. The apoplasm is the primary cell component that interacts with environmental stress and is essential for plant tolerance to freezing temperatures. The present study was conducted to gain insight into how the application of silicon (Si) and potassium (K) are involved in the leaf apoplasm contributes to freezing stress tolerance, and regulates carbohydrate metabolism. We used Satsuma mandarin (Citrus unshiu Marc.), the most successful commercially grown citrus cultivar in North Florida, and treated trees with two concentrations of Si and K (50 and 100 ppm) both individually and combined as foliar spray to determine their effect as they relate to improving cold hardiness. Freezing stress (-6 °C) caused a severe reduction in photosynthesis, and modulations in leaf carbohydrate metabolism resulted in inhibited plant growth. The exogenous application of Si and K both improved the photosynthesis rate, soluble sugars, and activities of enzymes of carbohydrate metabolism such as fructokinase, phosphofructokinase, hexokinase, sucrose and phosphate synthase, and acid and neutral invertase. Applying Si (100 ppm) and combined treatment (Si + K-50) showed the best response by inducing the maximum tolerance to freeze stress. Our data demonstrated the ameliorative effect of Si and K under freezing stress in citrus is associated with modification in carbohydrate metabolism in the leaf apoplasm. This study provides direction for future research to investigate the effect of Si and K on the transcriptome and metabolome in citrus plants and their tissues under freezing stress.Graphical

Effects of Freezing Temperature Parameterization on Simulated Sea‐Ice Thickness Validated by MOSAiC Observations

AbstractFreezing temperature parameterization significantly impacts the heat balance at sea‐ice bottom and, consequently, the simulated sea‐ice thickness. Here, the single‐column model ICEPACK was used to investigate the impact of the freezing temperature parameterization on the simulated sea‐ice thermodynamic growth during the MOSAiC expedition from October 2019 to September 2020. It is shown that large model errors exist with the standard parameterization and that different formulations for calculating the freezing temperature impact the simulated sea‐ice thickness significantly. Considering the winter mixed layer temperature, a modified parameterization of the freezing point temperature based on Mushy scheme was developed. The mean absolute error (ratio) of simulating sea‐ice thickness for all buoys reduces from 7.4 cm (4.9%) with the “Millero” scheme, which performs the best among the existing schemes in the ICEPACK model, to 4.2 cm (2.9%) with the new developed scheme.

Role of ice formation mechanisms occurring inside stylolite on limestone tilestone frost susceptibility

Freeze temperature and ice quantity formed inside porous media has been investigated on limestone tilestone samples by Differential Scanning Calorimetry (DSC) measurements. The aim was to determine the role of these stone frost features on limestone damage to Freeze-Thaw (FT) cycles, in relation to the presence of stylolite inside their structure. In fact, the presence of stylolite inside the structure leads to increase locally the pore rate and size, with connected pores. This implies a local increase of ice quantity formed at the surround of stylolite. Damage is thus associated to a heterogeneous nucleation, a rapid growth and ice-front propagation inside pores induced by the presence of stylolite. Specimens exhibiting an increase of quantity of ice formed inside their stylolite – of more than 30% compared to host rock – were damaged by freeze/thaw cycles. Furthermore, stones with freezing temperature lower than the minimum of FT cycles temperature are frost resistant. Finally, low-temperature calorimetry appears to be a practical and cheap method for quickly assessing frost limestone susceptibility. For example, this method can benefit some modest heritage constructions in UNESCO World Heritage site ‘Causse & Cevennes’, made by craftsmen who need to quickly know the frost resistance of the stones they use.

Adaptable Polyurethane Networks Containing Tertiary Amines as Intrinsic Bond Exchange Catalyst

AbstractVitrimers exhibit unique properties, such as thermal recyclability akin to thermoplastics, while structurally mirroring thermosets in terms of strength, durability, and chemical resistance. However, a significant limitation of these materials is their dependence on an external catalyst. Consequently, this research aims to develop vitrimer materials that incorporate an intrinsic catalyst, thus maintaining excellent thermomechanical properties and recyclability. Polyaddition polymerization is employed to synthesize the desired polymer, incorporating a self‐synthesized tertiary amine unit, (bis(2‐hydroxyethyl)‐3,3′‐((2‐(dimethylamino)ethyl)azanediyl)dipropanoate) (N‐diol), as an internal catalyst for transcarbamoylation and potential transesterification reactions. The resulting polymer, with a gel content of 97% and a glass transition temperature of 29 °C, is fabricated into test samples for comprehensive thermal and mechanical evaluations. The material demonstrates an initial Young's modulus of 555 MPa, retaining 81% of this value after two recycling processes. Additionally, using stress relaxation analysis (SRA), a topology freezing temperature of 82 °C, indicative of the characteristic Arrhenius‐like relaxation behavior, is identified with a bond exchange activation energy of 163 kJ mol−1.

In situ investigation of ice fractions and water states during partial freezing of pork loins and shrimps

Ice fractions and water states in partially frozen muscle foods greatly affect their quality. In the study, a variable temperature nuclear magnetic resonance (VT-NMR) with a liquid nitrogen temperature control system was employed to in situ investigate the relationship between ice fractions and temperatures and changes in water states during partial freezing and thawing of pork and shrimp. Results indicated that changes in ice fractions ranging from −2 ∼ −20 °C could be divided into 3 stages including slow increase, random leap and remarkable leap. More serious damages to the structures related to immobile water occurred in shrimp than in pork, and partial freezing also caused deterioration in muscle fibres related to free water. Additionally, −2 ∼ −3 °C and − 3.5 °C were the appropriate partial freezing temperatures for pork and shrimp, respectively. Therefore, the VT-NMR method possessed great potential for fundamental studies and applications of partial freezing of muscle foods.

Exchange Bias Induced by the Spin-Glass-Like State in a Te-Rich FeGeTe van der Waals Ferromagnet.

We have experimentally investigated the mechanism of the exchange bias in 2D van der Waals (vdW) ferromagnets by means of the anomalous Hall effect (AHE) together with the dynamical magnetization property. The temperature dependence of the AC susceptibility with its frequency response indicates a glassy transition of the magnetic property for the Te-rich FeGeTe vdW ferromagnet. We also found that the irreversible temperature dependence in the anomalous Hall voltage follows the de Almeida-Thouless line. Moreover, the freezing temperature of the spin-glass-like phase is found to correlate with the disappearance temperature of the exchange bias. These important signatures suggest that the emergence of magnetic exchange bias in the 2D van der Waals ferromagnets is induced by the presence of the spin-glass-like state in FeGeTe. The unprecedented insights gained from these findings shed light on the underlying principles governing exchange bias in vdW ferromagnets, contributing to the advancement of our understanding.

Double Helix of Icosahedra Structure and Spin Glass Magnetism of the δ-Co2.5Zn17.5-xMnx (x = 0.4-3.5) Pseudo-Binary Alloys.

We have synthesized δ-Co2.5Zn17.5-xMnx (x = 0.4-3.5) pseudo-binary alloys of 10 different compositions by a high-temperature solid-state synthetic route, determined their crystal structures and the Mn substitution pattern, and estimated the existence range of the δ-phase. The alloys crystallize in two chiral enantiomorphic space groups P62 and P64, where the basic atomic polyhedron of the chiral structure is an icosahedron and the neighboring icosahedra share vertices to form an infinitely long double helix along the hexagonal axis (like in the δ-Co2.5Zn17.5 parent binary phase). The alloys are pure δ-phase up to the Mn content x ≈ 3.5. The Mn atoms partially substitute Zn atoms at particular crystallographic sites located on the icosahedra. The study of magnetism was performed on the Co2.5Zn17.1Mn0.4 alloy with the lowest Mn content. Contrary to the expectation that structural chirality may induce the formation of a nontrivial magnetic state, a spin glass state with no relation to the structural chirality was found. The magnetic sublattice contains all of the necessary ingredients (randomness and frustration) for the formation of a spin glass state. Typical out-of-equilibrium dynamic phenomena of a spin system with broken ergodicity were detected below the spin freezing temperature Tf ≈ 8 K.

Low frequency of the wild-type freezing-tolerance LsCBF7 allele among lettuce population suggests a negative selection during domestication and breeding

Key messageSustainable winter production in lettuce requires freezing tolerant varieties. This study identified a wild-type allele of LsCBF7 that could contribute to freezing tolerance improvement in lettuce.Lettuce is one of the most consumed vegetables globally. While ideally grown in 13–21 °C, its cultivation extends into winter in milder climates. However, occasional freezing temperatures can significantly reduce yields. Therefore, the development of freezing-tolerant lettuce varieties has become a long-term goal of lettuce breeding programs. Despite its significance, our understanding of freezing tolerance in lettuce remains limited. Plants have evolved a coping mechanism against freezing, known as cold acclimation, whereby they can increase freezing tolerance when pre-exposed to low nonfreezing temperatures. The CBF pathway is well-known for its central role in cold acclimation. Previously, we identified 14 CBF genes in lettuce and discovered that one of them, LsCBF7, had a loss-of-function mutation. In this study, we uncovered that accessions from colder regions carried the wild-type allele of LsCBF7 and this allele likely contributed to increased freezing tolerance, with 14% of the lettuce population carrying this allele. Interestingly, in wild lettuce (L. serriola) that is considered a progenitor of cultivated lettuce, this wild-type allele was much more common, with a frequency of 90%. This finding suggests that this wild-type allele may have undergone negative selection during the domestication or breeding of lettuce. Our data strongly indicate that this allele could be linked to early bolting, an undesirable trait in lettuce, which may have driven the negative selection. While this wild-type allele shows promise for improving freezing tolerance in lettuce, it is crucial to decouple it from the early bolting trait to fully harness its potential in lettuce breeding.

Role of solvent composition and sintering time on the porosity of α‐alumina monoliths produced by freeze casting

AbstractThe present study reports the investigation of the influence of naphthalene–camphor binary solvent and the densification process on the pore structure formation of α‐alumina monoliths using the freeze‐casting technique with a freezing temperature control mechanism. Freeze‐casting technique allowed a controlled production of monoliths with high porosity (65%–70%) and distinct pore morphologies based on the adjustment of solvent composition (hypoeutectic, eutectic, and hypereutectic) and sintering time. In general, the longer the sintering time, the greater the average pore diameter (8–10 µm), the larger the grain size (∼319–596 nm), the higher the material density (∼1450–1650 kg/m3), the lower the open porosity (∼60%–49%), the higher the closed porosity (5%–18%), and the greater the compressive strength of the monoliths (hypoeutectic: 23.56 MPa; eutectic: 4.81 MPa; hypereutectic: 23.49 MPa). The study also reveals that the solvent composition directly influenced the alignment of the pore structure, as the pores of the final monolith resemble frozen solvent crystals. Hydraulic tortuosity varied from 1.30 to 1.53 for selected samples. Finally, solvent composition and sintering time proved to be important parameters that should be considered in the manufacturing process of porous ceramic structures via freeze casting.

Freezing of sessile water droplets on titanium alloy surfaces with various roughness: An in-situ experimental study

The threat of icing caused by supercooled water droplets on aircraft components such as wings and compressors is a serious concern for aviation safety, and the surface roughness of these components can experience alterations due to environmental corrosion or damage. However, the potential impact of surface roughness variation on their susceptibility to icing remains unclear. In this study, the freezing experiments of sessile water droplets on the surfaces of a typical aero-engine titanium alloy (ZTC4) with varying roughness were conducted using a laser confocal micro-Raman spectrometer with a heating/freezing stage. Three freezing stages were captured via an optical microscope, and the temperature changes of water droplet during the cooling process were explored through heat transfer simulation. In addition, the relationship between Raman peaks and temperatures of frozen droplets was quantified. The results of 200 repeated experiments demonstrated that the freezing temperatures of sessile water droplets exhibited a two-parameter Weibull distribution, and there was a nonlinear positive correlation between the mean freezing temperature and surface roughness, which implied that environmental corrosion or damage leading to an increase in surface roughness may significantly elevate the probability of component icing and safety issues.

Experimental study on the characteristics of R1150/R600 mixed refrigerant Joule-Thomson low-temperature freezer

In this paper, a low-temperature freezer based on Joule-Thomson system with a variable frequency fan was developed by using the natural binary mixture of R1150/R600. The experiment results demonstrated the feasibility of using this mixture to obtain the low freezing temperature below −70 °C. It could be found that when the concentration of R1150 was 27.5 %, it had the lowest daily energy consumption of 5.94 kWh/24 h. Furthermore, the influences of different fan speeds and active fan speed control on the cool-down characteristics of the system were also studied. The results indicated that lower fan speed in the early stage could effectively improve the cool-down performance. It was 51 min faster than that of the fixed operating fan speed under the optimal fan speed control at the target freezing temperature. Finally, the noise test of the freezer was carried out, and the influences of on–off temperature and fan speed on the system noise were also analyzed. The noise level of the system is between 46.71 dB and 51.62 dB, which is acceptable for the users. Moreover, the influence of fan speed on system noise was greater than that of different on–off temperatures. Therefore, improving the heat exchange efficiency of the condenser to reduce the fan speed is the possible direction of noise reduction for low-temperature freezers in the future.

Freezing-enhanced degradation of azo dyes in the chloride-peroxymonosulfate system

In this study, we investigated the freezing-induced acceleration of dye bleaching by chloride-activated peroxymonosulfate (PMS). It has been observed that the oxidation of chloride by PMS generates a free chlorine species, such as hypochlorous acid (HOCl), under mild acidic and circumneutral pH condition. This process is the major reason for the enhanced oxidation capacity for electron-rich organic compounds (e.g., phenol) in the chloride-PMS system. However, we demonstrated that the chloride-PMS system clearly reduced the total organic carbon concentration (TOC), whereas the HOCl system did not lead to decrease in TOC. Overall, the chemical reaction is negligible in an aqueous condition if the concentrations of reagents are low, and freezing the solution accelerates the degradation of dye pollutants remarkably. Most notably, the pseudo-first order kinetic rate constant for acid orange 7 (AO7) degradation is approximately 0.252 h−1 with 0.5 mM PMS, 1 mM NaCl, initial pH 3, and a freezing temperature of −20 °C. AO7 degradation is not observed when the solution is not frozen. According to a confocal Raman-microscope analysis and an experiment that used an extremely high dose of reactants, the freeze concentration effect is the main reason for the acceleration phenomenon. Because the freezing phenomenon is spontaneous at high latitudes and at mid-latitudes in winter, and the chloride is ubiquitous elsewhere, the frozen chloride-PMS system has potential as a method for energy-free and eco-friendly technology for the degradation of organic pollutants in cold environments.

Adaptive and Robust Vitrimers Fabricated by Synergy of Traditional and Supramolecular Polymers.

Vitrimers offer a unique combination of mechanical performance, reprocessability, and recyclability that makes them highly promising for a wide range of applications. However, achieving dynamic behavior in vitrimeric materials at their intended usage temperatures, thus combining reprocessability with adaptivity through associative dynamic covalent bonds, represents an attractive but formidable objective. Herein, we couple boron-nitrogen (B-N) dative bonds and B-O covalent bonds to generate a new class of vitrimers, boron-nitrogen vitrimers (BNVs), to endow them with dynamic features at usage temperatures. Compared with boron-ester vitrimers (BEVs) without B-N dative bonds, the BNVs with B-N dative bonds showcase enhanced mechanical performance. The excellent mechanical properties come from the synergistic effect of the dative B-N supramolecular polymer and covalent boron-ester networks. Moreover, benefiting from the associative exchange of B-O dynamic covalent bonds above their topological freezing temperature (Tv), the resultant BNVs also possess the processability. This study leveraged the structural characteristics of a boron-based vitrimer to achieve material reinforcement and toughness enhancement, simultaneously providing novel design concepts for the construction of new vitrimeric materials.

Adaptive and Robust Vitrimers Fabricated by Synergy of Traditional and Supramolecular Polymers

AbstractVitrimers offer a unique combination of mechanical performance, reprocessability, and recyclability that makes them highly promising for a wide range of applications. However, achieving dynamic behavior in vitrimeric materials at their intended usage temperatures, thus combining reprocessability with adaptivity through associative dynamic covalent bonds, represents an attractive but formidable objective. Herein, we couple boron‐nitrogen (B−N) dative bonds and B−O covalent bonds to generate a new class of vitrimers, boron‐nitrogen vitrimers (BNVs), to endow them with dynamic features at usage temperatures. Compared with boron‐ester vitrimers (BEVs) without B−N dative bonds, the BNVs with B−N dative bonds showcase enhanced mechanical performance. The excellent mechanical properties come from the synergistic effect of the dative B−N supramolecular polymer and covalent boron‐ester networks. Moreover, benefiting from the associative exchange of B−O dynamic covalent bonds above their topological freezing temperature (Tv), the resultant BNVs also possess the processability. This study leveraged the structural characteristics of a boron‐based vitrimer to achieve material reinforcement and toughness enhancement, simultaneously providing novel design concepts for the construction of new vitrimeric materials.

Freeze–thawed characteristics of lactone tofu under the synergy of low‐frequency electrostatic field

AbstractThe formation and melting of ice crystals bring undesirable changes to the gel structure of frozen food. To explore the role of Low‐frequency electrostatic field (LFE‐field) in the freeze–thaw quality of protein‐rich foods, the freezing temperature, thawing temperature, and the participation of the LFE‐field were used as variables to orthogonally optimize the treatment of tofu. The sensory score, color, moisture, aerobic bacterial count, and micromorphology were recorded to evaluate the quality variation of tofu. When be frozen at −50°C and thawed at 10°C, tofu maintains 91.1% hardness and 87.0% elasticity hinging on the effect of LFE‐field. When be frozen at −60°C in LFE‐field and thawed at 10°C, tofu maintains 90.7% hardness and 89.7% elasticity. The LFE‐field treatment also increased the water retention capacity and reduced the damage of ice crystals to the protein matrix structure of tofu. In addition, the LFE‐field has minimal impact influence on the tofu's color.Practical applicationsThe low‐frequency electrostatic field (LFE‐field) treatment increased the water retention capacity and reduced the damage of ice crystals to the protein matrix structure of tofu during the freeze–thaw process. In the future, the small LFE‐field could easily be installed in refrigerator and used for long time freezing preservation protein rich food to extend its shelf life and improve the storage quality, such as cheese, tofu, etc.

IMPLEMENTATION OF COLD CHAIN SYSTEM IN PEELED DEVEINED TAIL-ON VANNAMEI SHRIMP (Litopenaeus vannamei) PRODUCTS

Vannamei (Litopenaeus vannamei) Peeled Deveined Tail-On (PDTO) shrimp is frozen shrimp product consumers highly preferred. However, shrimp products are easily perishable that require a proper cold chain system to preserve their quality, shelf life, and nutritional value. This study investigated the cold chain implementation of PDTO shrimp processing in the fishery industry. The temperature of shrimp products, water, and rooms was monitored during processing. Results showed that the shrimp temperature measured in each process was below 5°C. However, abusive temperatures were detected in water used in the peeling and deveining step and soaking process, while water and shrimp temperatures altered each other. Moreover, room temperatures were recorded under 20°C, conforming to Ministry of Marine and Fisheries regulations. Air Blast Freezer and cold storage temperatures revealed that ABF and CS could not meet the company’s temperature standards. These findings may help shrimp companies monitor steps indicating to have temperature abuse attentively.

Preliminary Envelope for Large Transport Aircrafts Operating with Non-Primary Fuels AVGAS, MOGAS and F76-Dieso

This study explores the operational implications and safety considerations of using non-primary fuels—AVGAS, MOGAS, and F76 Dieso—in military transport aircraft, against the backdrop of standard aviation fuels. Through an analysis of fuel properties such as vapor pressure, density, viscosity, freeze temperature, water solubility, and thermal conductivity, this work outlines the operational envelopes for the mentioned non-primary fuels, highlighting the temperature and altitude limitations inherent to their use. The evaluation underscores the necessity of relevant testing, certification, and adherence to operational guidelines and constrains to ensure aircraft safety and reliability when standard fuels are unavailable, and hence, non-primary fuels may be required in special missions under emergency. Key findings include the specific altitude and temperature limitations for AVGAS and MOGAS to prevent fuel freezing and boiling, as well as the operational challenges posed by F76 Dieso due to its higher density and viscosity. The study also addresses the importance of managing water content in the fuel system, the flammability range of the non-primary fuels, and the considerations for fuel mixing to maintain aircraft performance and safety standards. This analysis aims to enhance the understanding of non-primary fuel usage in military transport aircraft, providing insights for system design, performance assessment, and the development of operational procedures to support military aviation in diverse operational scenarios.

Heat transport characteristics of a flat-evaporator loop heat pipe for use in a thermal management system of electric vehicles

In this work, a flat-evaporator loop heat pipe (FELHP), with a 100 cm2 rectangular thermal interface and an overall length of approximately 2 m was devised for the thermal management of electric vehicles. A simple rectangular-cuboid evaporator was devised using a novel stepped-flat wick structure, and the heat transport characteristics were systematically investigated in terms of the heat load, relative height of the evaporator to the condenser (i.e., position), heat sink temperature, and working fluid. In particular, water-ethanol binary mixtures with different compositions were tested to find an optimum low-freezing-temperature working fluid for use in thermal management system of the electric vehicles driving outdoors. Over the tested heat load range, a significant position dependence of the operating temperature was observed with a thermal resistance change from 0.21 K/W ± 0.02 K/W to 0.14 K/W ± 0.01 K/W for a 0.4 m change in the position. In contrast, the operating temperature of the FELHP was insensitive to changes in the heat sink temperature. A binary mixture containing 20% water and 80% ethanol (by volume) resulted in comparable heat transport characteristics to those of pure water but had a much lower freezing temperature (e.g., a thermal resistance of 0.25 K/W ± 0.03 K/W at 450 W and a freezing temperature of approximately -59 °C), demonstrating that this was an optimum composition of the water-ethanol mixture working fluid of the FELHP.

Metal Substitutions (M = Al, Ga, In; Sn, Ge; and Mn, Fe, Co) in ZnS: Sphalerite versus Wurtzite Formation.

A series of Zn1-xMxS polycrystalline samples were synthesized via a solid-state reaction in closed vessels to examine the solubility of foreign M cations within the wurtzite ZnS structure, employing quenching or slow cooling processes to favor specific polymorphs. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses revealed diverse structural behaviors across different cations. Group 13 elements (Al and Ga) formed solid solutions with a wurtzite structure, while In showed complex layer stacking defects. For 3d magnetic cations (Mn, Fe, and Co), a broad solubility range in the hexagonal structure was noted for Mn, whereas Fe and Co more readily formed cubic structures, with solubilities similar to Mn in the sphalerite form. Despite structural differences, magnetic susceptibilities and spin freezing temperatures for Fe and Co were comparable. Group 14 elements showed varied behaviors: Sn was insoluble in ZnS, as attested by unchanged unit cell parameters and surface crystallite Sn, whereas Ge only formed in the cubic phase with a solubility limit of x ≈ 0.2. The study discusses these variations in solubility and structure in terms of oxidation states, ionic-covalent radius, and coordination preferences in sulfides.

Anti-icing polyurethane coating on glass fiber-reinforced plastics induced by femtosecond laser texturing

Polyurethane coating has been commonly used in aerospace and construction, and enhancing anti-icing capabilities in low temperatures is crucial for preventing mechanical failures and reducing energy consumption. Utilizing a superhydrophobic surface was considered an important option to improve anti-icing performance. In this study, femtosecond laser treatment has applied to polyurethane coating on glass fiber-reinforced plastic (GFRP) to transform from hydrophilic to superhydrophobic. Results have indicated that laser treatment significantly reduced the solid–liquid contact area compared to the original surface. The non-polar groups on the surface contributed greatly to the enhancement of hydrophobicity. In comparison to the original surface, the freezing temperature of droplets on the superhydrophobic surface with improved anti-icing performance was reduced from −4.5 °C to −9.2 °C, while the freezing time was extended from 65 s to 269 s. This improvement was attributed to the reduction of solid–liquid contact area, resulting in a low heat transfer rate and a low heterogeneous nucleation rate. Additionally, the laser-treated surface exhibited excellent self-cleaning effects, along with mechanical and chemical stability.