Frozen Period Research Articles

Coordinated expression of Jumonji and AHCY under OCT transcription factor control to regulate gene methylation in wood frogs during anoxia.

Wood frogs (Rana sylvatica) can survive extended periods of whole body freezing. Freezing imparts multiple stresses on cells that include anoxia and dehydration, but these can also be experienced as independent stresses. Under anoxia stress, energy metabolism is suppressed, and pro-survival pathways are prioritized to differentially regulate some transcription factors including OCT1 and OCT4. Jumonji C domain proteins (JMJD1A and JMJD2C) are hypoxia responsive demethylases whose expression is accelerated by OCT1 and OCT4 which act to demethylate genes related to the methionine cycle. The responses by these factors to 24h anoxia exposure and 4h aerobic recovery was analyzed in liver and skeletal muscle of wood frogs to assess their involvement in metabolic adaptation to oxygen limitation. Immunoblot results showed a decrease in JMJD1A levels under anoxia in liver and muscle, but an increase was observed in JMJD2C demethylase protein in anoxic skeletal muscle. Protein levels of adenosylhomocysteinase (AHCY) and methionine adenosyl transferase (MAT), enzymes of the methionine cycle, also showed an increase in the reoxygenated liver, whereas the levels decreased in muscle. A transcription factor ELISA showed a decrease in DNA binding by OCT1 in the reoxygenated liver and anoxic skeletal muscle, and transcript levels also showed tissue specific gene expression. The present study provides the first analysis of the role of the OCT1 transcription factor, associated proteins, and lysine demethylases in mediating responses to anoxia by wood frog tissues.

Stability of SARS-CoV-2 Spike G614 Variant Surpasses That of the D614 Variant after Cold Storage.

ABSTRACTSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) carrying the D614G mutation on the spike protein is the predominant circulating variant and is associated with enhanced infectivity. However, whether this dominant variant can potentially spread through the cold chain and whether the spike protein affects virus stability after cold storage remain unclear. To compare the infectivity of two SARS-CoV-2 variants, namely, SARS-CoV-2 variants with spike protein with the D614 mutation (S-D614) and G614 mutation (S-G614), after different periods of refrigeration (4°C) and freezing (−20°C). We also determined the integrity of the viral RNA and the ability of the spike protein to bind angiotensin-converting enzyme 2 (ACE2) after storage at these conditions. The results showed that SARS-CoV-2 was more stable and infectious after storage at −20°C than at 4°C. Particularly, the S-G614 variant was found to be more stable than the S-D614 variant. The spike protein of the S-G614 variant had better binding ability with the ACE2 receptor than that of the S-D614 variant after storage at −20°C for up to 30 days. Our findings revealed that SARS-CoV-2 remains stable and infectious after refrigeration or freezing, and their stability and infectivity up to 30 days depends on the spike variant. Stability and infectivity are related to each other, and the higher stability of S-G614 compared to that of S-D614 may contribute to rapid viral spread of the S-G614 variant.IMPORTANCE It has been observed that variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are more stable and infectious after storage at −20°C than at 4°C. A SARS-CoV-2 S-D614G variant is currently the most dominant variant in circulation and is associated with enhanced infectivity. We compared the stability of two SARS-CoV-2 variants: the early S-D614 variant carrying the D614 spike protein and the new S-G614 variant carrying the G614 spike protein, stored at both 4°C and −20°C for different periods. We observed that SARS-CoV-2 remains stable and infectious after refrigeration or freezing, which further depends on the spike variant, that is, the ability of the spike protein to bind with the ACE2 receptor with higher efficiency. The high stability of the S-G614 variant also explains its rapid spread and infectivity. Therefore, precautions should be taken during and after handling food preserved under cold conditions.

Time Dependent Impact of Reactive Oxidants on Seminal Attributes of Murrah Bull during Cryopreservation and Storage

Background: Cryopreservation is an invaluable technique yet it is also known to be detrimental to sperm function and fertility due to cryo-injury and concomitant generation of reactive oxidants. During laboratory manipulation for the cryopreservation and freeze-thaw process, spermatozoa undergo osmotic stress, ionic imbalance, metabolic decoupling, membrane phase transition, destabilization of the cytoskeleton and antioxidant depletion which communally hampers the semen quality.Methods: With the aim of determining implications of cryopreservation and storage, semen samples were collected by artificial vagina technique from 12 Murrah bulls and subsequently examined at 0 hour (before cryopreservation) and at 24 hour, 1 month and 2 month of storage for various seminal attributes. Simultaneously seminal plasma was separated and preserved at -20oC till the analysis of biochemical indicators of semen quality viz., nitric oxide (NO), total antioxidant quantity (TAC) and lipid peroxidation status (TBARS). Result: A sharp reduction (p less than 0.01) in the semen quality was observed only at 24 h after cryopreservation except for viability. Significant reduction (p less than 0.05) in viable counts was observed up to 1 month interval. The capacitated sperm percentage was greater (p less than 0.01) in the cryopreserved semen as compared to fresh ejaculate. The mean ± SE levels of NO (μmol/L), TAC and TBARS (Units/ml) was 2.31±0.27, 0.73±0.04 and 1.11±0.16 respectively in seminal plasma of neat semen stored at -20oC, while the values in the extended seminal plasma after cryopreservation was 2.37±0.31, 0.44±0.03 and 0.65±0.03 respectively. So it can be inferred that most of the damage encountered by spermatozoa is during the initial period of freezing, but the damage associated by various stressors cannot be ignored.

Control of the Interactions Between Stream and Groundwater by Permafrost and Seasonal Frost in an Alpine Catchment, Northeastern Tibet Plateau, China

AbstractWhile the individual effects of permafrost and seasonal frost on the interactions between groundwater and surface water have received much attention, few attempts have been made to investigate the effects of permafrost and seasonal frost together on groundwater flow and its interactions with surface water. In this study, hydraulic, chemical, and isotopic data as well as a Bayesian mixing model were employed to investigate the interactions between streams and groundwater, the contributions of groundwater to the mainstream, and their relationships to the distribution of permafrost and seasonal frost in a representative subcatchment in the headwater region of the Heihe River Basin on the northeastern Qinghai‐Tibet Plateau in China. Our results showed that due to the freezing and thawing of recharge water sources and soils, the groundwater flow and stream flux from the permafrost zone to the seasonal frost zone increased during the thawing period, with maximum values in thawed period, and decreased during the frozen period. These variations affected groundwater recharge in the seasonal frost zone, resulting in dynamic changes in the groundwater table and the hydraulic gradient between the recharge and discharge points in the seasonal frost zone during the different freeze‐thaw periods. Correspondingly, the contribution of groundwater to the mainstream discharge decreased from 95% during the frozen period to 80%–90% during the thawing period. It then decreased to ∼40%–60% of the mainstream discharge during the thawed period and increased to ∼70%–90% during the refreezing period. From the permafrost zone to the seasonal frost zone and the catchment outlet, the aquifers in the piedmont plain of the seasonal frost zone play an important role in maintaining streamflows by switching their hydrological functions, that is, slowly releasing groundwater to maintain the streamflow during the frozen period and rapidly transferring the groundwater to mainstream during the thawed period.

How the Structure of GDP of Ukraine Responded to COVID-19

The impact of the COVID-19 pandemic on the structure of Ukrainian GDP is studied, with summing up the causes of impact occurrence and mechanisms of manifestation. The peculiarities of the pandemic’s impact on the institutional and industrial structure of economy in the specific conditions of Ukraine are revealed. The dynamics of the structure of the domestic GDP in the conditions of pandemic is analyzed.
 The contribution of the sectors of non-financial corporations, households, financial corporations and government in the Ukrainian GDP is highlighted. It is shown that the increased economic activity of non-financial sector resulted in a growth in dividends, royalties and other components of the property income. However, financial corporations, general government and households were losing property incomes, first of all due to the decreased interest rate of the National Bank of Ukraine, which reduced incomes of financial corporations in form of interests on loans, bond yields of the government, and deposit incomes of households.
 Problems of redistribution of primary incomes of sectors by the financial system are discussed. Emphasis is made on the banking sector. With the pandemic shattering the financial health of banks, they started to increase the commission fees to compensate the losses. This process is expected to go on in the forthcoming months. At the initial period of the economy freezing, banks did not feel its outcomes as severely as sectors like tourism, transport or culture. The dynamics of GDP structure by economic activity is analyzed by three dimensions given the available national accounts data of the State Statistics Service of Ukraine. The analysis covers, first, the dynamics of GDP structure by economic activity in absolute terms, second, the dynamics of GDP structure in current prices, and, third, the dynamics of GDP structure in last year prices, thus eliminating the price effect for the dynamics of GDP. The adverse impact of the dynamics of prices occurred in the following sectors: manufacturing; health care and social aid; education; water supply, sanitation, waste treatment; transport; storage facilities; postal and courier activities; temporary accommodation and public catering. While the grown prices for these sectors’ products increased their weight in GDP in current prices, this weight was smaller in comparable prices. 
 The study was conducted on the basis of research publications and material of the State Statistics Service of Ukraine and professional organizations. Desk research method was used in the process, i. e. analysis of available data, involving extraction and exploration of the already available information, which is the basis for producing new data in line of the author’s research objective.

Žurnāla „Inostrannaja Literatura” rezonanse Latvijas literārajā telpā politiskā atkušņa laikā

The paper is devoted to a parallel description of the literary processes in the Soviet Union and Soviet Latvia during Nikita Khrushchev’ reign, also known as the period of political thaw or the liberalisation of the communist regime (1953–1964). The main object of the research is the literary magazine Inostrannaja literatura (Иностранная литература), issued in the Soviet Union since 1955, dedicated to foreign literature and its translations; the principles of creating its content and structure during the political thaw period. The aim of the research: with concrete examples, to show the role of this legendary Russian literary periodical in the Iron Curtain period, expansion of freedom of thought, decanonization of socialist realism dogmas in general in the USSR, and also in the Latvian SSR. The methodological basis of the research consists of a comparative literature approach and a new historicism position that the literary text is important in studying different lines of history. The analysis of the publications clearly shows the replacement of the so-called periods of thaw and freezing. The article proves that the appearance of translations, reviews, previews, and research articles of foreign literature in this journal is closely connected with various political peripeteia of the USSR. In Latvia, there is a great resonance of Inostrannaja literatura, and it had an eventual influence on overcoming the dogmas of socialist realism in Latvian literature. The publications about the journal in Latvian literary editions and the study of the reception of one text example, a comparison of various editions of the writer Ēvalds Vilks’s (1923–1976) story “Twelve Kilometers”, prove it.

Heat transfer characteristics of gravelly soils with different compactness during unidirectional freezing process

During the construction of clay core rockfill dam in cold regions in winter, the heat transfer characteristics of gravelly soil are important to the anti-freezing control of the core. Laboratory experiment and field test data showed that the frost depth of gravelly soil in unconsolidated state was deeper than that in compacted state at the early period of soil freezing. With the increase of the freezing time, however, the frost depth of compacted soil is deeper than that of unconsolidated soil. Further study showed that this phenomenon was main caused by the change of thermophysical parameters between unconsolidated and compacted soil. Under the same soil temperature, the thermal conductivity of compacted soil was approximately 2.6 times of that of unconsolidated soil, and the volume heat capacity and phase change latent heat of compacted soil was approximately 1.7 times of that of unconsolidated soil. The different thermophysical parameters caused the differences of the heat transfer rate, temperature distribution and heat release by cooling between compacted soil and unconsolidated soil. This study provides a theoretical guidance for freezing process of soil with different compactness and anti-freezing technology of clay core rockfill dam in cold regions.

Bacterial shifts on broiler carcasses at retail upon frozen storage

Freezing broiler carcasses, industrially or at home, not only delays spoilage, but also is expected to increase food safety by hampering growth of food pathogens. However, detailed knowledge on microbial changes after a short or longer freezing period of fresh broiler meat in home freezing setting is lacking and no comparison between different freezing periods has been published yet.The present study combined classical isolation techniques and identification by MALDI-TOF MS with 16S rRNA amplicon sequencing to assess bacterial contamination on broiler carcasses that were either bought fresh and then frozen for short periods (total n = 20) in home freezing, or industrial frozen one (total n = 4) at retail. Changes in total aerobic bacteria (TAB) were also studied on 78 freshly bought broiler carcasses that were then stored frozen for up to 6 months in domestic freezers. Salmonella and Campylobacter were examined to assess the effect of freezing on controlling common foodborne pathogens.The contamination level of mesophilic and psychrotrophic TAB was numerically equal on carcasses at retail, either fresh or frozen at different time points. After short and long freezing period, a decrease in counts of mesophilic TAB was observed, while changes in counts of psychrotrophic TAB were rarely observed. No correlation between home freezing period and TAB load, either mesophilic (R = -0.006, p = 0.949) or psychrotrophic (R = 0.080, p = 0.389), was observed. No Salmonella and Campylobacter was detected on industrial frozen carcasses but on fresh carcasses at retail, either pre-freezing or after freezing. The bacterial communities were influenced by freezing, in which some genera showed significantly changes in relative abundance after freezing.In conclusion, from a food safety point of view, freezing of meat products does not serve as safety hurdle, and freezing should only be considered as a method for extending shelf life compared with fresh chicken meat. Applying hygienic slaughter procedures to keep the initial contamination as low as possible, and the maintenance of the cold chain during further processing are the key factors in food safety.

Methane emissions during different freezing-thawing periods from a fen on the Qinghai-Tibetan Plateau: Four years of measurements

How methane (CH4) fluxes from alpine peatlands, especially during freeze-thaw cycles, affect the global CH4 budget is poorly understood. The present research combined the eddy covariance method, incubation experiments and high-throughput sequencing to observe CH4 flux from an alpine fen during thawing-freezing periods over a period of four years. The response of CH4 production potential and methanogenic archaea to climate change was analyzed. We found a relatively high mean annual cumulative CH4 emission of 37.7 g CH4-C m−2. The dominant contributor to CH4 emission was the thawing period: warmer, longer thawing periods contributed 69.1-88.6% to the annual CH4 budget. Non-thawing periods also contributed, with shorter frozen-thawing periods accounting for up to 18.5% and shorter thawing-freezing periods accounting for up to 8.8%. Over the course of a year, emission peaked in the peak growing season and at onset of thawing and freezing. In contrast, emission did not vary substantially during the frozen period. Daily mean emission was highest during the thawing period and lowest during the frozen period. Diurnal patterns of CH4 emission were similar among the four periods, with peaks ranging from 12:00 to 18:00 and the lowest emission around 00:00. Water table and temperature were the dominant factors controlling CH4 emissions during different thawing-freezing periods. Our results suggest that CH4 emission from peatland will change substantially as CH4 production, microbial composition, and patterns of thawing-freezing cycles change with global warming. Therefore, frequent monitoring of CH4 fluxes in more peatlands and in situ monitoring of methanogenesis and related microbes are needed to provide a clear picture of CH4 fluxes and the thawing-freezing processes that affect them.

On the impact of release policies on bug handling activity: A case study of Eclipse

Large software projects follow a continuous development process with regular releases during which bugs are handled. In recent years, many software projects shifted to rapid releases that reduce time-to-market and claim a faster delivery of fixed issues, but also have a shorter period to address bugs. To better understand the impact of rapid releases on bug handling activity, we empirically analyze successive releases of the Eclipse Core projects, focusing on the bug handling rates and durations as well as the feature freeze period. We study the impact of Eclipse’s transition from a yearly to quarterly release cycle. We confirm our findings through feedback received from five Eclipse Core maintainers. Among others, our results reveal that Eclipse’s bug handling process is becoming more stable over time, with a decreasing number of reported bugs before releases, an increasing bug fixing rate and an increasingly balanced bug handling workload before and after releases. The transition to a quarterly release cycle continued to improve bug handling. In addition, more effort is spent on bug fixing during the feature freeze period, while the bug handling rates do not differ between both periods.

Effects of thermal cycles on microstructural and functional properties of nano treated clayey soil

Thermal cycles can remarkably alter the geological and resistance properties of soil beneath structures. This research examined the effect of simultaneous use of glass fiber and nano-SiO2 on strength properties of low plasticity clay (CL) under various thermal cycles. The contents of glass fiber and nano-SiO2 were chosen 1.5%, 2.5%, 3.5% and 0.5%, 1.0%, 1.5% of the soil dry weight, respectively. The strength properties of natural soil and treated clay were estimated via unconfined compression and direct shear tests. Further, the images of scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests were used to assess the microstructure of soil affected by freeze and thaw periods. The obtained results indicated that different mixtures of nano-SiO2 and glass fiber can be employed as effective additives to reduce the negative impacts of thermal cycles. The mixture of 1.0% nano-SiO2 and 2.5% glass fiber with clay was found as an optimum mixture content, causing elevation of unconfined compressive strength (UCS) from 0.717 MPa to 1.381 MPa even after 12 thermal cycles. The combined impact of nano-SiO2 and glass fiber on the internal friction angle was greater than its effect on the cohesion of the samples. On the other hand, the cohesion and internal friction angle of the samples treated with 1.0% nano-SiO2 and 2.5% glass fiber were obtained 1.36 and 2.47 times of the natural clay, respectively. Microstructural evaluation through SEM images and BET analyses showed that thermal cycles led to an increase in the micro-voids of clay structure and separated clay minerals from each other. Observation of SEM images reflected the fact that thermal stresses due to freeze and thaw periods caused whiskers' growth from nano-SiO2 surfaces. The whiskers and glass fiber lead to modify strength properties and structure of clayey soil by creating filamentary networks on nano and macro scales, respectively.

Characteristics of mesoscale eddies of Arctic marginal seas: results of numerical modeling

A simple method is proposed for identifying mesoscale eddies in the results of numerical modeling. The method uses extrema in distributions of the sea level elevation as eddy markers. By using the method, we analyze statistics of mesoscale eddies resulting from SibPOM numerical simulations in the Eurasian sector of the Arctic marginal seas. The results of using this method show that the number of cyclonic eddies slightly exceeds the number of anticyclonic eddies, but the excess is only 2-3%. Also, we demonstrate that a significant number of eddies arise under the ice cover. The number of such eddies increases significantly in winter. This fact indicates that the convection caused by salt rejection during freezing plays an essential role in their formation. The numerical modeling results confirm the phenomenon of active eddy generation in the ice edge zone. Besides, the results show that in the near-edge zone, a more significant number of eddies are formed from the icy side adjacent to the edge, and not from the ice-free side. The periods of seawater freezing and ice melting, accompanied by corresponding displacements in the ice edge, produce eddies different in nature. The number of eddies in the marginal ice zone has two seasonal maxima corresponding to these two periods.

Pathway analysis to quantify the relationship between runoff and meteorological factors in re-identifying seasonality throughout the Ashi River watershed, Northeast China

At the watershed scale, weather types show variability and heterogeneity throughout a basin; as a result, unified weather conditions are not realistic for analyzing the underlying surface response. The Ashi River watershed was selected as a case in the present study, and weather types were redefined. Statistics on the spatial and temporal changes of meteorological factors from 1989 to 2015 and path analysis were used to identify the relationship between meteorological factors and runoff. Results showed that (1) statistical weather analysis revealed multidimensional heterogeneity of season types. The weather was clearly diverse in the sub-basins. The redivided times for the seasons were 61 days for spring, 55 days for summer, 48 days for autumn, 201 days for winter, and a frozen period (spring, summer, autumn) and non-frozen period (winter). (2) Temperature decreased by 0.35 °C over the past 27 years, and it increased gradually from the southeast to the northwest. Precipitation and runoff increased from 1989 to 2015. Mutations in precipitation and runoff occurred in 1994 and 1998. Temperature, precipitation, and runoff varied across frozen and non-frozen periods. (3) In different typical hydrologic years, meteorological factors affected runoff in different ways, and the direct effect of temperature on runoff was larger and positive. Precipitation in the flood year had a significant and direct impact on runoff in the non-frozen period, while evaporation had a significant and indirect impact on runoff in the dry year. The barometric pressure also had different impacts on runoff in the dry and median years. The purpose of this study was to provide scientific guidance for local agricultural production and water distribution.

Testing water fluxes and storage from two hydrology configurations within the ORCHIDEE land surface model across US semi-arid sites

Abstract. Plant activity in semi-arid ecosystems is largely controlled by pulses of precipitation, making them particularly vulnerable to increased aridity that is expected with climate change. Simple bucket-model hydrology schemes in land surface models (LSMs) have had limited ability in accurately capturing semi-arid water stores and fluxes. Recent, more complex, LSM hydrology models have not been widely evaluated against semi-arid ecosystem in situ data. We hypothesize that the failure of older LSM versions to represent evapotranspiration, ET, in arid lands is because simple bucket models do not capture realistic fluctuations in upper-layer soil moisture. We therefore predict that including a discretized soil hydrology scheme based on a mechanistic description of moisture diffusion will result in an improvement in model ET when compared to data because the temporal variability of upper-layer soil moisture content better corresponds to that of precipitation inputs. To test this prediction, we compared ORCHIDEE LSM simulations from (1) a simple conceptual 2-layer bucket scheme with fixed hydraulic parameters and (2) an 11-layer discretized mechanistic scheme of moisture diffusion in unsaturated soil based on Richards equations, against daily and monthly soil moisture and ET observations, together with data-derived estimates of transpiration / evapotranspiration, T∕ET, ratios, from six semi-arid grass, shrub, and forest sites in the south-western USA. The 11-layer scheme also has modified calculations of surface runoff, water limitation, and resistance to bare soil evaporation, E, to be compatible with the more complex hydrology configuration. To diagnose remaining discrepancies in the 11-layer model, we tested two further configurations: (i) the addition of a term that captures bare soil evaporation resistance to dry soil; and (ii) reduced bare soil fractional vegetation cover. We found that the more mechanistic 11-layer model results in a better representation of the daily and monthly ET observations. We show that, as predicted, this is because of improved simulation of soil moisture in the upper layers of soil (top ∼ 10 cm). Some discrepancies between observed and modelled soil moisture and ET may allow us to prioritize future model development and the collection of additional data. Biases in winter and spring soil moisture at the forest sites could be explained by inaccurate soil moisture data during periods of soil freezing and/or underestimated snow forcing data. Although ET is generally well captured by the 11-layer model, modelled T∕ET ratios were generally lower than estimated values across all sites, particularly during the monsoon season. Adding a soil resistance term generally decreased simulated bare soil evaporation, E, and increased soil moisture content, thus increasing transpiration, T, and reducing the negative bias between modelled and estimated monsoon T∕ET ratios. This negative bias could also be accounted for at the low-elevation sites by decreasing the model bare soil fraction, thus increasing the amount of transpiring leaf area. However, adding the bare soil resistance term and decreasing the bare soil fraction both degraded the model fit to ET observations. Furthermore, remaining discrepancies in the timing of the transition from minimum T∕ET ratios during the hot, dry May–June period to high values at the start of the monsoon in July–August may also point towards incorrect modelling of leaf phenology and vegetation growth in response to monsoon rains. We conclude that a discretized soil hydrology scheme and associated developments improve estimates of ET by allowing the modelled upper-layer soil moisture to more closely match the pulse precipitation dynamics of these semi-arid ecosystems; however, the partitioning of T from E is not solved by this modification alone.

Mathematical modeling of Arctic sea ice freezing and melting based on nonlinear growth theory

The spatiotemporal distribution of sea ice in the cold Arctic region is of climatic and engineering significance. However, in terms of statistics, there remains a lack of quantitative mathematical descriptions of the annual periodic sea ice cycle for the entire Arctic and its regional seas. Using the semi-enclosed and seasonally ice-covered Kara Sea as a systematic case study, this quantitative study focuses on the theoretical mathematical expressions of the nonlinear freezing and melting processes of sea ice. The periodic cycle of sea ice coverage was divided into freezing, frozen, and melting stages, with the continuous ice-coverage curves clearly highlighting temporal nonlinearity during both freezing and melting periods. Thus, nonlinear growth theory was used to quantitatively simulate ice-coverage curves. Results from a comparison of the various functions showed the Logistic function to most accurately quantify the annual periodic cycle, followed by the Gompertz and von Bertalanffy functions, with the Negative exponential and Brody functions having the least suitable results. Further, our results indicate that net sea surface heat flux primarily contributes to the nonlinear temporal freezing and melting of sea ice in the periodic cycle. The nonlinear growth theory was also applied to other Arctic sea areas, including the Laptev Sea, East Siberian Sea, Chukchi Sea, Beaufort Sea, and Baffin Bay. By using the developed mathematical equations, we are able to quantify sea ice conditions at any given time for different Arctic sea areas.

BORON INCREASES THE VIABILITY OF HUMAN CANCER AND MURINE FIBROBLAST CELLS AFTER LONG TIME OF CRYOPRESERVATION

Through the process of cryopreservation, cells are stored at very low temperature for a long time to decrease the biological and chemical reactions in viable cells. In this process, the administration of cryoprotective agents is crucial since cryopreservation is regarded as a leading process in various research fields such as biotechnology, clinical medicine and maintenance of both animal and plant cells. Even after a long time of storage in very low temperatures, a recovery is achieved by cryo-preservative agents that act on cellular metabolism and biophysiology of cells. In the current study, the effect of boron on cryopreservation of human lung cancer cell line, A549, and murine fibroblast cell line, L929, was investigated with the help of cell viability assay, colony forming unit assay and RT-PCR analysis. 15 µg/ml boron supplemented freezing medium was found to indicate a positive effect on cell viability. Moreover, gene expression profiles of A549 and L929 cell lines have been altered. The levels of apoptosis related genes decreased while proliferation related gene levels increased significantly after repeated freeze-thaw cycles or long period of freezing. As indicated through our results, sodium pentaborate pentahydrate, as a boron source, might be a crucial cryoprotective agent for cryo-protection and bio-banking of cancer and healthy cells while keeping their viability and functionality.

Effect of frozen storage on microbial load of hybrid heteroclarias, Clarias gariepinus and Oreochromis niloticus

Effect of frozen storage on microbial load of hybrid Heteroclarias, Clarias gariepinus and Oreochromis niloticus was studied. Fifty samples, each of Heteroclarias, C. gariepinus and O. niloticus with an average weight of 210 + 15g were collected at a commercial fish farm in the study area after which they were processed and frozen at -18°C and microbial analyses were done at 0, 14, 28, 42 and 56 days after frozen storage. Data obtained were logarithmically transformed (log cfu/g) and then subjected to statistical analysis using SPSS 16.0 version. No significant (p>0.05) difference was found for total viable count (TVC), total fungal count (TFC), total coliform count (TCC) and Klebsiella spp. count of the fish species studied during the frozen period. The potential of freezing as a good fish preservation method was established as it inhibited microbial activities thereby elongating fish shelf life. It was concluded that Clarias gariepinus and Oreochromis niloticus fish species can be kept safe up to 56 days by freezing as the microbial loads did not change significantly during the period. Uncontrolled discharge of effluents into the surrounding water bodies should also be checked to avoid contamination prior to fish harvest.

The Modelling of Freezing Process in Saturated Soil Based on the Thermal-Hydro-Mechanical Multi-Physics Field Coupling Theory

The freezing process of saturated soil is studied under the condition of water replenishment. The process of soil freezing was simulated based on the theory of the energy and mass conservation equations and the equation of mechanical equilibrium. The accuracy of the model was verified by comparison with the experimental results of soil freezing. One-side freezing of a saturated 10-cm-high soil column in an open system with different parameters was simulated, and the effects of the initial void ratio, hydraulic conductivity, and thermal conductivity of soil particles on soil frost heave, freezing depth, and ice lenses distribution during soil freezing were explored. During the freezing process, water migrates from the warm end to the frozen fringe under the actions of the temperature gradient and pore pressure. During the initial period of freezing, the frozen front quickly moves downward, the freezing depth is about 5 cm after freezing for 30 h, and the final freezing depth remains about 6 cm. The freezing depth of the soil column is affected by soil porosity and thermal conductivity, but the final freezing depth mainly depends on the temperatures of the top and lower surfaces. The frost heave is mainly related to the amount of water migration. The relationship between the amount of frost heave and the hydraulic conductivity is positively correlated, and the thickness of the stable ice lens is greatly affected by the hydraulic conductivity. With the increase of the hydraulic conductivity and initial void ratio, the formation of ice lenses in the soil become easier. With the increase of the initial void ratio and thermal conductivity of soil particles, the frost heave of the soil column also increases. With high-thermal-conductivity soil, the formation of ice lenses become difficult.

Effects of natural and anthropogenic factors and their interactions on dust events in Northern China

Aeolian dust can influence the climate, air quality, human health, and ecosystems. Dust events in Northern China are the main contributors to dust aerosols in the world, but the impacts of meteorological and anthropogenic factors and their interactions on dust events remain unclear. This study analyzed the spatial and temporal variations of dust event frequencies and quantitatively investigated the impacts of meteorological conditions, anthropogenic factors, and their interactions on dust events using the geographical detector model (GeoDetector) in Northern China. Results revealed that the dust event frequency significantly decreased by 0.006 times yr−1 per site during 1980–2007. At the regional scale, there were large seasonal variations in the effects of meteorological conditions and anthropogenic factors on dust events. Strong winds and soil surface conditions are main drivers of dust events in spring. In summer and autumn, anthropogenic factors have significant impacts on the occurrence of dust events, but the frozen period and relative humidity are major impacting factors in winter. Effects of natural and anthropogenic factors on dust events showed great spatial and seasonal disparities over different vegetation regions. Interactions between two factors enhanced their impacts on the occurrence of dust events. There are also large spatial and seasonal variations in the primary interactions on dust events over different vegetation regions. The findings could help us to better understand the relative importance of various factors on dust events, which has important implications for improving the prediction of dust emission models and developing desertification control strategies.

Variability of chlorophyll and the influence factors during winter in seasonally ice-covered lakes

Lake ice is an essential and integral part of the cryosphere and freshwater systems. The formation of lake ice affects the physical, hydrological, and biological conditions of ecological systems. Global warming may contribute to even shorter periods of ice cover in the lakes of the Frigid Zone, which adversely affects the growth of phytoplankton and primary productivity. This study was conducted for the purpose of evaluating the growth of phytoplankton and factors involved, in 28 ice-covered lakes across the Songnen Plain, in the Northeast of China, to understand how they take part in the whole-ecosystem functioning. A total of 1026 water samples were collected in April, September, and January during the period 2014–2018. In the frozen period, the concentration levels of dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) were all comparable with the spring and autumn. Despite the limited light availability and low temperature, the phytoplankton survived in sub-ice waters during winter with a low concentration of chlorophyll a (Chla). Its average concentration was positively correlated with the concentration observed in the previous autumn (rp = 0.563, p < 0.01). According to the regression tree analysis, during the winter period, Chla was mainly related to the concentration of TN in sub-ice water (TNwater) and with the difference of concentration of TP between water and ice (TPcd). Furthermore, either in ice or in sub-ice water, the concentration of Chla was also significantly affected by total suspended matter (TSM) (p < 0.05). The levels of TNwater, TPcd, and TSM could explain the 77.8% of the variance in the concentration of Chla during winter with contributions in the ranges of 25.5%–35.0%, 9.2%–11.3%, and 21.5%–34.0%, respectively (p < 0.05). This research substantially contributes to comprehending how the existing conditions under-ice affect the whole ecosystem when the ice cover is reduced lakes or rivers.