Influence of the Mixture of Carrageenan Oligosaccharides and Egg White Protein on the Gelation Properties of Culter alburnus Myofibrillar Protein under Repeated Freezing–Thawing Cycles

This study aims to investigate the influence of the mixture (CGO/EWP) of carrageenan oligosaccharide (CGO) and egg white protein (EWP) (CGO/EWP, CGO: EWP = 1:1, m/m) on the functional, structural, and gelling properties of Culter alburnus myofibrillar protein (MP) during repeated freezing–thawing cycles by treating MP samples separately with EWP, CGO, or CGO/EWP based on the wet weight (1%, m/m), using samples without any cryoprotectant as the blank group. After the second repeated freezing–thawing cycle, the sulfhydryl group content was found to be significantly (p < 0.05) higher in the CGO/EWP (30.57 nmol/mg) and CGO (36.14 nmol/mg) groups than in the EWP group (23.80 nmol/mg), indicating that CGO/EWP and CGO can more effectively delay the oxidative deterioration of functional groups. Additionally, the surface hydrophobicity was shown to be significantly lower in the CGO (25.74) and CGO/EWP (27.46) groups than in the EWP (34.66) and blank (39.32) groups. Moreover, the α-helix content was higher in the CGO (35.2%) and CGO/EWP (32.3%) groups than in the EWP (29.2%) and blank (25.0%) groups. These data indicated that CGO and CGO/EWP could more effectively increase the structural stability, thereby inhibiting the exposure of hydrophobic groups and curbing the decline of α-helix content. During the heat-induced gel-forming process, EWP and CGO/EWP could enhance the gel viscoelasticity and strength. After the second freezing–thawing cycle, when compared with the blank group, the CGO/EWP group showed significantly (p < 0.05) higher water-holding capacity (66.30% versus 53.93%) and shorter T22 relaxation time (413.56 versus 474.99 ms). The integrated results indicated that CGO/EWP could more effectively delay the decrease of protein–water molecular interaction forces in the MP gel. This study shed light on the mechanism of CGO/EWP as a cryoprotective mixture in improving the deterioration of MP gelation properties during repeated freezing–thawing cycles.

Investigation of the Shear Mechanical Behavior of Sandstone with Unloading Normal Stress after Freezing–Thawing Cycles

Freezing–thawing action has a great impact on the physical and mechanical deterioration processes of rock materials in cold areas where environmental changes are very complicated. The direct shear test under unloading normal stress was adopted to investigate the shear mechanical behavior of sandstone samples after a freezing–thawing cycle in this paper. The failure shear displacement (Dsf), the failure normal displacement (Dnf), the shear displacement of unloading (Dsu), and the normal displacement of unloading (Dnu) were analyzed to describe the evolution of shear and normal deformation during the test. The results indicated that the shear displacement increased as the freezing–thawing cycle duration increased in a direct shear test under unloading normal stress. The unloading rate and the number of freezing–thawing cycles affected the failure pattern of the rock sample significantly in both the direct shear test under unloading normal stress and the direct shear test. The three-dimensional inclination angle, the distortion coefficient, and the roughness correlation coefficient of the fracture surface are dependent on the number of freezing–thawing cycles and the unloading rate. The surface average gradient mode of the fracture surface decreased as the freezing–thawing cycle times and unloading rate rose.

Impact of Operational Factors, Inoculum Origin, and Feedstock Preservation on the Biochemical Methane Potential

Anaerobic digestion for the valorization of organic wastes into biogas is gaining worldwide interest. Nonetheless, the sizing of the biogas plant units require knowledge of the quantity of feedstock, and their associated methane potentials, estimated widely by Biochemical Methane Potential (BMP) tests. Discrepancies exist among laboratories due to variability of protocols adopted and operational factors used. The aim of this study is to verify the influence of some operational factors (e.g., analysis frequency, trace elements and vitamins solution addition and flushing gas), feedstock conservation and the source of inoculum on BMP. Among the operational parameters tested on cellulose degradation, only the type of gas used for flushing headspace of BMP assays had shown a significant influence on methane yields from cellulose. Methane yields of 344 ± 6 NL CH4 kg−1 VS and 321 ± 10 NL CH4 kg−1 VS obtained from assays flushed with pure N2 and N2/CO2 (60/40 v/v). The origin of inoculum (fed in co-digestion) only significantly affected the methane yields for straw, 253 ± 3 and 333 ± 3 NL CH4 kg−1 VS. Finally, freezing/thawing cycle effect depended of the substrate (tested on biowaste, manure, straw and WWTP sludge) with a possible effect of water content substrate.

Biological and Biochemical factors Predictive of Oocyte survival, Fertilization, Pregnancy in oocyte thawing cycles

Optimization and monitoring of IVF treatments requires good data on the effect and magnitude of clinical factors affecting treatment outcome. Many factors have been known to affect IVF outcomes. Currently there are still no data to predict whether a patient who undergoes In Vitro Fertilization (IVF) cycles can be considered a good candidate for oocyte freezing. The aim of this study was therefore to evaluate which biological and biochemical factors can be predictive of oocyte survival and fertilization, as well as of clinical pregnancy in oocyte thawing cycles. This study showed that none of the factors available on the day of the pick-up is able to predict (in case of oocyte cryopreservation) the success of a subsequent oocyte thawing cycle. Only the transfer of at least one Grade 1 embryo after oocyte thawing cycle has a statistically significant impact on pregnancy. Unfortunately, this cannot be considered an elective factor to guide the clinician and/or the embryologist in choosing patient's treatment as it is not available on the day of the oocyte pick up but it is a result of oocyte thawing. Keywords: Oocyte thawing; Biological and biochemical markers; Fertilization rate; Ongoing pregnancy rate

Microstructure and mechanical behavior of asphalt mixture based on freeze-thaw cycle

PurposeIn order to unravel the evolution of microstructure characteristics and the change of mechanical properties of bituminous mixture in the freezing and thawing environment in cold region, this study starts from macroscopic experiments and analyzes the changes in mechanical properties of asphalt mixtures before and after freezing and thawing in detail. On this basis, the displacement of key particles in the structure of asphalt mixture under the action of external forces (before and after freezing and thawing) is simulated through the combination macroscopic and microscopic methods.Design/methodology/approachThe climate in China exhibits high complexity and diversity, divided into five zones based on the temperature difference from south to north. Considering that the significant effect of geography and natural climate on the design, construction and maintenance of asphalt pavement, the criterion for the road construction at different areas should be highly different.FindingsThe results show that the mechanical properties of asphalt mixture greatly decrease due to the influence of freeze-thaw, and the displacement of key particles in the structure of asphalt mixture (several representative particle sizes were selected through experiments) is obviously observed because of the action of external force. By analyzing the variation of several key particle sizes after freezing-thawing cycle, the gradation standard of asphalt mixture aggregate suitable for cold area was obtained. The research results have certain theoretical and practical value for the design and application of asphalt mixture in cold area.Originality/valueThe results show that the mechanical properties of asphalt mixture greatly decrease due to the influence of freeze-thaw, and the displacement of key particles in the structure of asphalt mixture (several representative particle sizes were selected through experiments) is obviously observed because of the action of external force. By analyzing the variation of several key particle sizes after freezing-thawing cycle, the gradation standard of asphalt mixture aggregate suitable for cold area was obtained. The research results have certain theoretical and practical value for the design and application of asphalt mixture in cold area.

Experimental investigation on bond strength between BFRP bars and concrete under freeze-thaw cycles

To investigate the bond strength between BFRP bars and concrete under freezing and thawing cycles, a total of 36 specimens for freezing and thawing cycles tests and center pull-out tests were carried out with different times of freezing and thawing cycles (0, 10, 20, and 40 times) and different concrete strength grades (C30, C35, and C40). The results of this study showed that the specimens without freezing and thawing cycle (0 times) and specimens of C30 with freeze-thaw for 40 times were pulled out, and the remaining specimens were split. With the increase of the concrete strength grade, the debonding strength increases gradually and the ultimate bond strength does not increase in proportion. The debonding strength of BFRP bars and concrete decreases gradually with the times of freezing and thawing cycles. The ultimate bond strength and peak slip indicated a trend of increasing and then decreasing with the increasing times of freezing and thawing, while the peak slip of specimens of C30 with 40 times freeze-thaw increases slightly.

Soil microbial legacies differ following drying-rewetting and freezing-thawing cycles

Climate change alters frequencies and intensities of soil drying-rewetting and freezing-thawing cycles. These fluctuations affect soil water availability, a crucial driver of soil microbial activity. While these fluctuations are leaving imprints on soil microbiome structures, the question remains if the legacy of one type of weather fluctuation (e.g., drying-rewetting) affects the community response to the other (e.g., freezing-thawing). As both phenomenons give similar water availability fluctuations, we hypothesized that freezing-thawing and drying-rewetting cycles have similar effects on the soil microbiome. We tested this hypothesis by establishing targeted microcosm experiments. We created a legacy by exposing soil samples to a freezing-thawing or drying-rewetting cycle (phase 1), followed by an additional drying-rewetting or freezing-thawing cycle (phase 2). We measured soil respiration and analyzed soil microbiome structures. Across experiments, larger CO2 pulses and changes in microbiome structures were observed after rewetting than thawing. Drying-rewetting legacy affected the microbiome and CO2 emissions upon the following freezing-thawing cycle. Conversely, freezing-thawing legacy did not affect the microbial response to the drying-rewetting cycle. Our results suggest that drying-rewetting cycles have stronger effects on soil microbial communities and CO2 production than freezing-thawing cycles and that this pattern is mediated by sustained changes in soil microbiome structures.

Effect of a Freezing-thawing Cycle on Overall and Inter-variability of Runoff and Soil Loss Components for a Loess Soil

Background: Because control of runoff generation as well as soil loss is influenced by freezing-thawing, proper knowledge and insight into the freezing-thawing process in combination with other hydrological processes is essential for executives and planners. However, such dynamic phenomenon and corresponding consequences have not been studied adequately. The present study was therefore planned to comparatively analyze the effects of a freezing-thawing cycle on hydrologic behaviors of loess soil from northeast of Iran. Towards that, the small-size (0.5×0.50×0.30 m) erosion plots were subjected to a freezing-thawing cycle in accordance with governing conditions on the region of the origin soil. The plots were subjected to a freezing-thawing treatment through inducing cold air until temperature declined to below -20 °C and lasted for three days using a large cooling compartment system, and then were kept in the laboratory with ambient temperature of above 10 °C for two days. The treated plots as well as untreated (control) plots were then exposed to a simulated rainfall with an intensity of 72 mm h-1 and 0.5 h duration while they were placed on a slope of 20%. Results: The results indicated that the hybrid processes of freezing-thawing, and splash and interrill erosions significantly affected runoff generation and soil loss at small plots. So that the time to runoff reduced by 1.65 times in the freezing-thawing treatment compared to that reported for the control treatment. The runoff volume and soil loss also increased at tune of 1.38 and 2.90 times in treated plots in comparison with those measured for the untreated plots. Laboratorial results indicated significant differences (p< 0.006) between runoff and soil loss behaviors in plots subjected to a freezing-thawing cycle and those of control condition. Conclusion: The performance of ice lenses and freezing fronts and creating near-saturation moisture after completing the cycle were evaluated as the most important factors affecting the different soil behaviors under frozen-thawed cycle.