软质聚氨酯泡沫塑料脱模剂的研制

对一种用于软质聚氨酯泡沫塑料成型加工的脱模剂进行了配方研究，脱模性能优良，可以重复多次利用，成本低廉，而且配料较为充足。     

Measures of cardiac autonomic control in women with differing volumes of physical activity

Abstract

The most recent (1996) drinking guidelines of the American College of Sports Medicine (ACSM) propose that athletes should drink “as much as tolerable” during exercise. Since some individuals can tolerate rates of free water ingestion that exceed their rates of free water loss during exercise, this advice has caused some to overdrink leading to water retention, weight gain and, in a few, death from exercise-associated hyponatraemic encephalopathy. The new drinking guidelines of the International Olympic Committee (IOC), recently re-published in this Journal, continue to argue that athletes must drink enough to replace all their weight lost during exercise and to ingest sodium chloride since sodium is “the electrolyte most critical to performance and health”. In this rebuttal to that Consensus Document, I argue that these new guidelines, like their predecessors, lack an adequate, scientifically proven evidence base. Nor have they been properly evaluated in appropriately controlled, randomized, prospective clinical trials. In particular, these new guidelines provide erroneous recommendations on five topics.

If novel universal guidelines for fluid ingestion during exercise are to be promulgated by important international bodies including the IOC, they should first be properly evaluated in appropriately controlled, randomized, prospective clinical trials conducted under environmental and other conditions that match those found in “out-of-doors” exercise. This, and the potential influence of commercial interests on scientific independence and objectivity, are the two most important lessons to be learned from the premature adoption of those 1996 ACSM drinking guidelines that are not evidence-based. These concerns need to be addressed before the novel IOC guidelines are accepted uncritically. Otherwise the predictable consequences of the premature adoption of the 1996 ACSM guidelines will be repeated.     

Fluid balance of elite Brazilian youth soccer players during consecutive days of training

Abstract

In this study we investigated pre-training hydration status, fluid intake, and sweat loss in 20 elite male Brazilian adolescent soccer players (mean ± s: age 17.2 ± 0.5 years; height 1.76 ± 0.05 m; body mass 69.9 ± 6.0 kg) on three consecutive days of typical training during the qualifying phase of the national soccer league. Urine specific gravity (USG) and body mass changes were evaluated before and after training sessions to estimate hydration status. Players began the days of training mildly hypohydrated (USG > 1.020) and fluid intake did not match fluid losses. It was warmer on Day 1 (33.1 ± 2.4°C and43.4 ± 3.2% relative humidity; P < 0.05) and total estimated sweat losses (2822 ± 530 mL) and fluid intake (1607 ± 460 mL) were significantly higher (P < 0.001) compared with Days 2 and 3. Data also indicate a significant correlation between the extent of sweat loss and the volume of fluid consumed (Day 1: r = 0.560, P = 0.010; Day 2: r = 0.445, P = 0.049; Day 3: r = 0.743, P = 0.0001). We conclude that young, native tropical soccer players arrive hypohydrated to training and that they exhibit voluntary dehydration; therefore, enhancing athletes' self-knowledge of sweat loss during training might help them to consume sufficient fluid to match the sweat losses.     

Evaluation of pre-game hydration status,heat stress,and fluid balance during professional soccer competition in the heat

Abstract

In this study, we assessed initial hydration status (stadium arrival urine specific gravity), fluid balance (pre- and post-game nude body weight, fluid intake, urine collection), and core temperature changes (pre-game, half-time, post-game) during a professional soccer game. We monitored 17 male players (including goalkeepers) between arrival at the stadium and the end of the game (3 h), playing at 34.9°C and 35.4% relative humidity, for an average wet bulb globe temperature (WBGT) heat stress index of 31.9°C. Data are reported as mean±standard deviation (range). Initial urine specific gravity was 1.018±0.008 (1.003–1.036); seven players showed urine specific gravity ≥ 1.020. Over the 3 h, body mass loss was 2.58±0.88 kg (1.08–4.17 kg), a dehydration of 3.38±1.11% body mass (1.68–5.34% body mass). Sweat loss was 4448±1216 ml (2950–6224 ml) versus a fluid intake of 1948±954 ml (655–4288 ml). Despite methodological problems with many players, core temperatures ≥ 39.0°C were registered in four players by half-time, and in nine players by the end of the game. Many of these players incurred significant dehydration during the game, compounded by initial hypohydration; thermoregulation may have been impaired to an extent we were unable to measure accurately. We suggest some new recommendations for soccer players training and competing in the heat to help them avoid substantial dehydration.     

热应激与运动

在热环境下运动时,热应激和运动应激联合作用导致体温、脑和肌肉局部温度升高并且出现脱水,全面影响运动员的生理功能、心理过程及运动能力.通过运动与热环境的联合刺激,运动员可获得对运动热应激的有效适应.科学补液是缓解运动中热应激和热脱水问题的有效措施.     

脱水山药片的加工工艺初探

脱水山药片是近年来出现的有一定药用价值的方便食品,能较好保持新鲜山药特有的营养成分,其色泽自然风味好、工艺简便、市场前景看好。     

Modeling and optimization of catalytic dehydration of ethanol to ethylene using central composite design

The central composite design in the modeling and optimization of catalytic dehydration of ethanol to ethylene was performed to improve the ethylene yield. A total of 20 experiments at random were conducted to investigate the effect of reaction temperature, Si/Al ratios of H-ZSM-5 catalyst and liquid hourly space velocity (LHSV) on the ethylene yield. The results show that the relationship between ethylene yield and the three significant independent variables can be approximated by a nonlinear polynomial model, with R-squared of 99.9% and adjusted R-squared of 99.8%. The maximal response for ethylene yield is 93.4% under the optimal condition of 328 °C, Si/Al ratio 85, and LHSV 3.8 h⁻¹.     

Organic synthesis using clay catalysts

Conclusion The clay minerals can catalyze a variety of organic reactions occurring on their surface and interstitial space. Synthetic organic chemists have been attracted to their tremendous potential as catalysts only relatively recently. Modification of their properties by incorporating different metal cations, molecules or complexes, can lead to catalysts that are useful in effecting even more varieties of reactions and higher selectivity in product structure and yield. There is a theory that the molecules of life actually developed in sedimentary clays. As the organic chemist is becoming more aware of the clay’s efficacy, its uses in organic synthesis are bound to increase, especially because it helps in developing eco-friendly chemical processes. The dark clay has a bright future in the area of organic synthesis.     

乙醇在浓硫酸催化下,温度不同产物不同之因探析

乙醇在浓硫酸催化下脱水反应,生成乙醚与乙烯的主要因素是温度。文章分析了不同温度下的产物。     

The impact of making-weight on cognitive performance in apprentice jockeys

Jockeys regularly engage in rapid weight-loss practices in preparation for competition. These practices are thought to impair cognitive function, although the evidence in support of this theory remains inconclusive. The purpose of this study was to examine the effects of making-weight on cognitive function in apprentice jockeys in a simulated and competitive environment. Apprentice jockeys (n = 12) reduced their body mass by 4% in 48 h in a simulated environment using weight-loss methods typically adopted in preparation for racing. Simple and choice reaction time, attention, learning and memory were assessed before and after the weight loss. A further 10 apprentice jockeys performed the cognitive function assessment in a competitive racing environment at both a self-reported “normal” and “light” body mass. Hydration status and body mass were assessed in all trials. In the simulated environment, body mass was reduced by 4.2 ± 0.3%, yet no change in cognitive function was observed. Cognitive function also remained unchanged in the competitive environment after a body mass loss of 5.7 ± 1.9%. Typical reductions in body mass in preparation for racing have no effect on cognitive function in apprentice jockeys in a simulated and competitive environment. Further research is required to investigate the physiological mechanisms preventing the adverse effects of making-weight on cognitive function in jockeys.