Effect Of Cold Conditions Research Articles

Effects of cold conditions on the growth rates of a subtropical conifer

Araucaria angustifolia is an endangered species that occurs in the high and cold regions of southern Brazil. This species has economic importance due to its wood and seeds, as well as playing a fundamental ecological role for the southern fauna and flora. Climate change can affect its distributional area and conservation, making it urgent to investigate the effect of climate on its development. The objective of our study was to investigate how growth rates of A. angustifolia vary in relation to interannual precipitation, temperature, frost and snowfall events. For this purpose, we used two samples obtained from each of 33 individual trees from a forest fragment on the Santa Catarina plateau, Brazil. Classical dendrochronological methods were applied for the preparation and dating of the samples. The tree rings were measured using specialized software. Superposed Epoch analysis was used to test the snow accumulation events. The climatic variables were tested by means of a correlation analysis. The Superposed Epoch analysis was used to test the snow accumulation events. Our results indicate that the species shows significant sensitivity to the climate, with the maximum and minimum absolute temperatures respectively correlated with positive and negative growth rates. Snowfall also reduced growth of A. angustifolia. Overall, extreme cold events are threats to the conservation of the species.

Modelling of equilibrium working capacity of PSA, TSA and TVSA processes for CO2 adsorption under direct air capture conditions

In this study, direct air capture performance of polymeric adsorbent was studied by determining CO2-isotherms in very dilute conditions (CO2 partial pressure up to 5mbar). The effect of cold conditions (0°C and −10°C) and humidity on the CO2 capacity was also studied. The experimental isotherms were used in temperature-dependent equilibrium modelling to simulate equilibrium CO2 working capacities in pressure-swing adsorption (PSA), temperature-swing adsorption (TSA) and temperature-vacuum swing adsorption (TVSA). Experimental adsorption capacities of 0.80mmolCO2/gsorbent and 0.89mmolCO2/gsorbent were obtained from 400ppmv CO2 in dry cold conditions and at 25°C in humid conditions, respectively. The highest experimental capacity gained from 400ppmv CO2 was 1.06mmolCO2/gsorbent in humid cold conditions. In terms of the working capacity, PSA was found not to be a viable process option. Humidity promoted TSA working capacity up to by 0.36mmolCO2/gsorbent (78%). TSA could produce larger than 0.5mmolCO2/gsorbent working capacity levels even with very low regeneration temperatures (50–60°C) when adsorbing either in dry cold conditions or humid warm conditions. Such EWC levels with dry TVSA could only be achieved using 90°C regeneration temperature with adsorption in either cold conditions or from compressed air. Based on these results, TVSA should only be considered in PtX applications requiring high-purity CO2.

French vertical-flow constructed wetlands in mountain areas: how do cold temperatures impact performances?

The French version of vertical-flow constructed wetlands (VFCWs) is characterized by treating directly raw wastewater on a first-stage filter. VFCW is a well developed technology with more than 3,500 plants in operation in France. However, VFCW performance may be affected under the low temperatures reached in mountain areas during winter. The effect of cold conditions over 12 plants, ranging from 75 to 1,900 person equivalent and from 680 to 1,500 m above sea level, was studied over 2 years. The plant hydraulic loads, and air and filter temperatures were continuously measured. In addition, 24-h flow proportional sampling, at each stage of treatment, was conducted in summer (as a reference) and winter. Online measurements of ammonium and nitrates were also analyzed to describe the nitrogen removal dynamics. Since no impact on chemical oxygen demand (COD), biochemical oxygen demand (BOD) and suspended solids removal was observed, the effect of cold temperatures on nitrification was further analyzed. Nitrogen removal was relatively unaffected during winter season. Significant effects were confirmed only for the second stage for loads above 10 gTKN/m²/d (TKN: total Kjeldahl nitrogen). Temperature profiles allowed analysis of the filter buffer capacity in terms of freezing. Under minimal air temperature of -19 °C, no critical operation was observed, although design and operation recommendations can be provided to ensure suitable plant performances.

Effect of Cold Conditions on Double Poling Sprint Performance of Well-Trained Male Cross-Country Skiers

This study compared the effects of cold (-14° C) and moderate environments (6° C) on double poling (DP) sprint performance. Wearing modern cross-country ski racing suits, 14 highly trained male cross-country skiers performed a test protocol on a DP ergometer, consisting of a standardized warm-up followed by a 30-second maximal sprint (DP30s) and a 2-minute maximal sprint (DP2min), and after an 8-minute recovery period, another DP30s and DP2min were performed. Finally, the participants performed an incremental DP test to exhaustion. We observed no difference between rectal temperature in cold and moderate conditions. Mean skin temperature (Tskin) was lower in the cold condition; the lowest values being 20.3° C at -14° C and 27.0° C at 6° C. Power output decreased between the first and the second DP30s under both conditions, but the reduction was 4.9% (p < 0.05) greater in the cold condition. Power output decreased by 4.8% (p < 0.05) between the first and second DP2min at -14° C, but we found no difference at 6° C. In the incremental test to exhaustion, there was a 7.2% (p < 0.05) reduction in peak power output and a 7.8% (p < 0.05) lower peak oxygen consumption at -14° C. In conclusion, this study demonstrated that DP sprint performance was lower at -14° C than at 6° C. Tskin and body temperature were lower at -14° C. This may indicate cooling of superficial musculature and may explain the reduced DP sprint performance observed in our study.

Lipid mobilization, gluconeogenesis and ageing-related processes in dormant walnut kernels during moist chilling and warm incubation

AbstractTo understand the beneficial effects of cold conditions during the alleviation of dormancy of walnut (Juglans regiaL.), lipid mobilization, gluconeogenesis and changes related to ageing were compared in dormant kernels incubated in the cold and under deteriorating warm conditions. Stratifying kernels at 5°C for 30 d enhanced their germination capacity, whereas warm-incubated (27°C) kernels turned rancid after 20 d and had reduced germination. Kernel imbibition was sufficient to bring about lipid mobilization, irrespective of temperature of incubation. Although imbibed kernels displayed high isocitrate lyase activity, starch and soluble sugar accumulation occurred only under cold conditions. Deteriorative 64 kDa fatty acyl-ester hydrolase activity declined in cold-stratified kernels. Cold treatment also led to reduced lipid peroxidation and hydrogen peroxide in kernels. The activity of NADP+-isocitrate dehydrogenase, an NADPH-generating enzyme, declined in warm-incubated kernels. Thus, warm-incubated kernels undergo ageing associated with oxidative stress, but there are beneficial effects of cold stratification in preventing deteriorative ageing-related processes. Imbibition is sufficient to allow lipid mobilization to occur in dormant walnut kernels, although cold stratification accompanied by gluconeogenesis is essential for kernel germination.

Sea temperature variations in the Tsitsikamma Coastal National Park, South Africa, with notes on the effect of cold conditions on some fish populations

From sea surface temperature records for the Storms River area, South Africa, between 1978 and 1984, a mean of nine major declines (≥ 3°C within 48 h) per annum were recorded, 81 per cent between November and April. Continuous temperature records were made at 12 and 22 m during summer 1983/84, and 90 percent of the temperature declines (≥ 1°C) were found to occur during or just after (≤ 3 days) easterly (NE–SE) winds. Also, there was a marked tendency (c. 75%) for temperatures at the surface and 12 m deep to decrease during the first day of these winds and, conversely, to increase during the first day of westerly (NW–SW) winds. Cool conditions in January 1984 resulted in the death of 14 fish species and, for some of the species, the rapidity of the temperature decline appeared to be the determinant factor. A comparison of rock and estuarine angling catches for the Tsitsikamma region during summers experiencing warm (1983) and cold (1984) sea conditions suggests that Pomatomus saltatrix (elf) migrate into the Keurbooms Estuary during cold upwelling events.

Cold Stress as it Affects Animal Production

Almost two-thirds of all livestock in North America are raised in regions where the mean January temperature is below 0 C. The effects of cold conditions on productivity and efficiency of feed conversion by swine, dairy and beef cattle are reviewed. Swine are rather cold-susceptible and are therefore usually kept in heated housing when raised in colder regions. Lactating or fattening cattle are extremely cold-hardy and rarely experience climatic conditions below their lower critical temperature. Despite the absence of a challenge to homothermy in cattle, there are marked seasonal fluctuations in the cattle's level and efficiency of production which probably arise from hormonal and adaptive changes occurring as a consequence of mild cold stress. Primary among these changes are an increase resting metabolic rate, and hence an increased energy requirement for maintenance, and an increased rate of passage of digesta, which results in reduced digestive efficiency. With cold there is stimulation of appetite, which may partially counteract the reduced level of production but not the reduced efficiency of utilization of dietary energy.