The Influence of Freezing and Thawing Process on the Bending Moment Capacity of L-Shaped Heat-Treated Wood Dowel Joints

In this work, the influence of the freezing and thawing process on the bending moment capacity of L-shaped heat-treated wood dowel joints is analysed. The parts of the joints were made of heat-treated ash (Fraxinus excelsior) wood. Half of the analysed joints were randomly divided in two groups. One group was frozen and thawed in a climatic chamber and the other group was kept in laboratory environmental conditions. The bending moment capacity was calculated by means of ultimate failure load, which was experimentally obtained. One-way analysis of variance (One-way ANOVA) was applied to figure out if there is a significant difference between the analysed groups. Based on the obtained results, it was concluded that the freezing and thawing process did not significantly affect the strength of the L-shaped heat-treated wood dowel joints.

Conducting Cytocompatible Scaffolds: Composite of Sodium Hyaluronate and Colloidal Particles of Conducting Polymers

Novel bio-inspired conductive scaffolds composed of sodium hyaluronate containing water soluble polyaniline or polypyrrole colloidal particles (concentrations 0.108, 0.054 and 0.036 % w/w) were manufactured. For this purpose, either crosslinking with N-(3-dimethylaminopropyl-N-ethylcarbodiimide hydrochloride and N-hydroxysuccinimid or a freeze-thawing process in the presence of poly(vinylalcohol) were used. The scaffolds comprised interconnected pores with prevailing porosity values of ~30 % and pore sizes enabling the accommodation of cells. Good swelling capacity (92 – 97 %) without any sign of disintegration was typical for all samples. The elasticity modulus depended on the composition of the scaffolds, with the highest value of ~50 000 Pa obtained for the sample containing the highest content of polypyrrole particles. The scaffolds did not possess cytotoxicity and allowed cell adhesion and growth on the surface. Using the in vivo-mimicking conditions in a bioreactor, cells were also able to grow into the structure of the scaffolds. The technique of scaffold preparation used here thus overcomes the limitations of conducting polymers (e.g. poor solubility in an aqueous environment, and limited miscibility with other hydrophilic polymer matrices) and moreover leads to the preparation of cytocompatible scaffolds with potentially cell-instructive properties, which may be of advantage in the healing of damaged electro-sensitive tissues.

Numerical simulation of coupled liquid water, stress and heat for frozen soil in the thawing process

PurposeThe purpose of this paper is to perform the thermo-hydro-mechanical (THM) numerical analysis in order to study the thawing process for frozen soil and to predict the thawing settlement.Design/methodology/approachA new one-dimensional multi-field physical coupled model was proposed here to describe the thawing process of saturated frozen soil, whereby the void ratio varied linearly with effective stress (Eq. 10) and hydraulic conductivity (Eq. 27b). The thawing process was simulated with different initial and boundary conditions in an open system with temperature variations. The mechanical behavior and water migration of the representative cases were also investigated.FindingsThe comparisons of representative cases with experimental data demonstrated that the model predicts thawing settlement well. It was found that the larger temperature gradient, higher overburden pressure and higher water content could lead to larger thawing settlement. The temperature was observed that to distribute height linearly in both frozen zone and unfrozen zone of the sample. Water migration forced to a decrease in the water content of the unfrozen zone and an increase in water content at the thawing front.Research limitations/implicationsIn this study, only the one-directional thawing processes along the frozen soil samples were investigated numerically and compared with test results, which can be extended to two-dimensional analysis of thawing process in frozen soil.Originality/valueThis study helps to understand the thawing process of frozen soil by coupled thermo-hydro-mechanical numerical simulation.

RESEARCH INTO THE THERMOPHYSICAL CHARACTERISTICS OF MUSCLE AND ADIPOSE TISSUES IN THE FREEZING–THAWING PROCESS

The paper presents a study of the thermophysical characteristics of meat systems based on minced beef and pork with different morphological composition in the freezing–thawing process, and those of model systems based on minced beef with addition of adipose tissue (raw fat). The method used to detect and compare the thermodynamic changes consisted in determining the effective specific heat capacity by freeze-thaw thermograms and was based on a set of informational parameters related to it (cryoscopic temperature, cryoscopic interval of temperatures, specific heat of phase transition in the cryoscopic temperature interval, change of enthalpy in the interval of temperatures of the sample tested, proportion of moisture that changes its physical state in the cryoscopic temperature interval). It has been shown that the morphological structure of meat (the ratio of muscle, connective, and adipose tissues) significantly affects the thermophysical parameters of meat systems during freezing and defrosting. It has been found that under the conditions of a freeze–thaw cycle, an increase in the content of connective tissue leads to a higher proportion of moisture that changes its physical state in the cryoscopic temperature interval, while an increase in the adipose tissue content in a meat system reduces the moisture that changes its physical state in the cryoscopic temperature interval. When adipose tissue was introduced into meat systems, the freezing process resulted in a higher rate of formation of ice crystals and a lower rate of moisture migration from cells to the intercellular space, and crystal formation became a controlled process. When manufacturing semi-finished frozen meat products, regulating the ratio of muscle and adipose tissues makes it possible to influence the stability of the properties of meat systems in the technological cycle “freezing – storage – thawing” and to create products with the required functional, technological, and thermophysical parameters. This research can be a basis for developing the recipe compositions and technological parameters of manufacturing semi-finished frozen meat products and finished products based on them

Optimization of a Protocol for the Cryopreservation of Sperm in Pellets for the Common Pheasant (Phasianus colchicus mongolicus)

The sperm of each avian species and breed have unique characteristics that render them more or less susceptible to the freezing–thawing process; therefore, a suitable cryopreservation protocol that is specific for the sperm of each type of bird is needed. In this context, little information about the common pheasant’s sperm is available. Therefore, the aim of this study was to test different parameters at each step of the process of freezing into pellets and thawing to detect the least deleterious parameter settings. Sixteen different protocols were tested by studying two levels in each of the four steps (dilution, equilibration at 5 °C, final dimethylacetamide concentration, and dimethylacetamide equilibration time) comprising the freezing process. The pheasant sperm exhibited a high susceptibility to the damage caused by freezing into pellets; however, the survival of the sperm reached 29%, and the greatest recovered mobility was 22%. The mobility of the sperm was affected by the dilution and the dimethylacetamide concentration, and the viability of the sperm was affected by the equilibration at 5 °C and the dimethylacetamide equilibration. The protocols that caused the least damage to the pheasant sperm were found to be those with higher dilution rates, 10 minutes of equilibration at 5 °C, and 6% dimethylacetamide equilibrated for 1 or 5 minutes. In the present study, we individualise some applicable parameters for certain critical steps of the freezing–thawing process; however, further investigations are needed in order to improve upon and complete a suitable protocol for the cryopreservation and thawing of pheasant sperm.

Comparing Glycerol with Dimethylformamide and Combination for Cryopreservation of Pug Dog Semen in Egg Yolk Plasma Containing Extender

Background: In order to find an alternative cryoprotectant for canine semen, different cryoprotectants, as dimethyl sulphoxide and ethylene glycol, dimethyle formamide either alone or in combination with glycerol have been evaluated on pooled semen of different breeds with different opinions. Methods: In the current study the effect of glycerol, DMF and their combination in Tris-citric acid-fructose egg yolk plasma extender on motility, viability, plasma membrane integrity (PMI), acrosome integrity (AI), inner mitochondrial membrane potential (IMMP), reactive oxygen species (ROS) and antioxidant enzymes in frozen-thaw semen of pug breed was compared. Result: Values for motility, viability, (PMI), AI were significantly (p less than 0.05) high in TCFEYP-G compared to TCFEYP-DMF and TCFEYP-G+DMF at post thaw. However, HIMMP and MIMMP/MDA were non-significantly (P greater than 0.05) high and low in TCFEYP-G compared to TCFEYP-DMF and TCFEYP- G + DMF at post thaw, respectively. MDA concentration was significantly (p less than 0.05) low in TCFEYP-G compared to TCFEYP-DMF and TCFEYP-G + TCFEYP-DMF extenders. However, H2O2, scavenging capacity of spermatozoa, cryopreserved in TCFEYP-G was significantly (p less than 0.05) higher than in TCFEYP-DMF and TCFEYP-G + TCFEYP-DMF. However, there was no significant (p greater than 0.05) difference in superoxide free radical scavenging activity and nitrite concentration of spermatozoa among the three extenders. Activity of GPX, SOD and Catalase was also significantly (p less than 0.05) higher in TCFEYP-G compared to TCFEYP-DMF and TCFEYP-G+DMF. However, values were reverse for GRE activity. This study concludes that glycerol is a healthier cryoprotectant to protect canine spermatozoa from cryo-injury during freezing-thawing process.

Preparation of regenerated cellulose from rice straw lignocellulosic waste and its use for reinforced paper products

Rice straw waste is a lignocellulosic waste produced by farmers in large quantities. In this study, regenerated cellulose (RC) from rice straw was prepared by dissolving rice straw holocellulose (HC) in NaOH/Urea/Thiourea/Water solution by the freeze-thawing process. The crystallinity index of RC was calculated at 31%, which is out of the crystallinity range of 39%–69% that has been previously suggested. The study indicated that the RC is amorphous with a low degree of polymerization (638) and higher hydroxyl group content as compared to HC. The fiber length of RC was found to be 26.7% shorter; however, the width of RC was 21.2% higher as compared to HC. Reduced kinked fiber content was observed in the fraction of RC (18.3%) as compared with HC (39.1%), and a higher curl index of fiber was observed more so in HC (10.5%) than RC (5.6%). Because of the regeneration process, the fiber length was reduced and a fines element content of about 96% was observed in RC compared to the initial fines content of HC (56.9%). Irrespective of the high fines element content of RC, the composite paper of rice straw bleached pulp and RC fibers was developed with an increase in the tensile index from 41.4 N.m/g to 71.2 N.m/g and an increase in the burst index from 4.7 kPa.m2/g to 5.3 kPa.m2/g with the addition of 5% and 15% RC, respectively. However, enhanced tear index of paper was observed up to 5% and then it declined upon further addition of RC. The study revealed that regenerated cellulose can be used as a strength additive to overcome the shortcomings of low mechanical properties in paper products.