Vitrification Ability of Combined and Single Cryoprotective Agents

Cryoprotective agents (CPA) are an important part of many current vitrification methods. The vitrification ability of CPAs influences the probability of the glass transition and water crystallization occurrence. Thermal characteristics and the vitrification ability of two combined CPAs (PVS2 and PVS3), common plant vitrification solutions, and four single CPAs (ethylene glycol, DMSO, glycerol, and sucrose), the components of the mentioned PVSs, were evaluated utilizing a differential scanning calorimetry (DSC) during standard cooling/warming rates of 10 °C min−1. The effect of solute concentration on their vitrification ability was shown in the CPAs tested. Four typical concentration regions at which the glassy state and/or crystallization occurred were defined. We suggest the solute concentration of 0.7 g g−1 as the universal vitrification concentration, characterized by an actual Tg of CPA solution and limited water crystallization. Knowledge of the thermal properties of CPAs allows the design of new combined CPAs with the required vitrification ability respecting the cryopreservation method used and the characteristics of the cryopreserved sample.

In-situ preparation of hierarchical Beta zeolite by steam- assisted crystallization method using meso-macroporous silica

In this paper, a series of meso-macroporous silica (MMS) were prepared by phase separation, then mic-meso-macroporous Beta zeolite was prepared by steam-assisted crystallization (SAC) method using the meso-macroporous silica as substrate. The factors such as the amount of water, crystallization time, aluminum source, amount of template agent during the SAC method were investigated. Various characterization methods such as BET, XRD, SEM were used to investigate the physical and chemical properties of the prepared materials. The results showed that the meso-macroporous silica could be transformed into Beta zeolite through the SAC method while the macroporous structure was still maintained.

Change in the volume of water crystallization as a result of exposure to a high-frequency electromagnetic field

The influence of a high-frequency electromagnetic field on the process of water crystallization has been stud-ied.Water irradiated by аfield at 30–200 MHz was kept from 0 to 21 days, then it was frozen. Volumes of ice at crystallization were compared for water irradiated and unirradiated by the field. Values located more or less symmetrically near zero; 2) values with a predominantly positive shift, and 3) values for which the shift is mostly negative. Positive shift was noted when combining 200 MHz and the exposure time up to 11 days. The maximum effect of relative volume increase almost two times was observed at 200 MHz and one day ex-posure time. The maximum compression of ice approximately three times compared to the unirradiated sam-ple occurred twice: after field effect at 90 MHz and exposure time of 11 days, and at 140 MHz and exposure time of 21 days. The similarity of time dependence at 170MHz with the dependence of thermal effect of glu-cose dissolution found in early works was noted.The data obtained confirm that field effect results in both strengthening and loosening of water structure

CALCULATION OF HEAT CAPACITY IN MEAT DURING ITS FREEZING CONSIDERING PHASE CHANGE

As a consequence of insufficient study of water phase change in meat accompanied by water crystallization, its modeling is currently based on the empirical dependence of the frozen water portion on temperature. Such model does not allow answering a number of questions such as of metrological order, and also of physicochemical interpretation of processes occurring in meat during water crystallization. In this paper, we propose an approach to modeling the phase change process of meat during its freezing on the basis of the phonon theory of Debye crystallization, which allows to obtain physically justified dependences of heat capacity on temperature in the phase change region. The obtained dependences may serve as a simple method for calculating the heat capacity of meat in the temperature range of 113 K to the cryoscopic temperature of the given meat type, or as a basis for the analysis and correction of factors affecting the meat freezing in the temperature range of the phase change.

Study of Water Freezing in Nano-Channels of Supramolecular Structure Formed by Wedge-Shaped Amphiphilic Molecules

Phase behavior and supramolecular structure stability of wedge-shaped mesogens at negative temperature have been studied for the first time. The effect of geometrical confinement on water crystallization in different channels was examined. The role of local ordering of linear alkyl groups on stability of the nanochannels during water freezing was enlighten.

Influence of the relative dimensions of the cavity on the conjugate convective heat transfer and on the shape of crystallization fronts in the method of Horizontal Directed Crystallization

The process of water crystallization in rectangular cavities is numerically studied. The liquid being studied is water having an inverse temperature dependence of the density. Calculations were carried out with a suddenly cooled vertical wall of a rectangular cavity. The initial temperature of the melt is maintained on the opposite wall. The finite element method was used to solve a system of equations for the nonstationary free convection of a melt, taking into account the dependence of the density on temperature. The heat conduction equation in the solidified substance was also solved. The problems were solved in a conjugate formulation taking into account the release of the latent heat of crystallization at the liquid-solid interface.