降雨增加对多年冻土区铁路路基水热影响研究

近50 a青藏高原湿化趋势显著,降雨变化导致地表能量平衡过程、活动层水分状况和水热输运过程改变。以青藏高原北麓河铁路路基试验段水分监测为基础,基于土壤–地表–大气能量平衡的冻土水–汽–热耦合模型研究在未来降雨变化情景下,降雨对冻土路基水热的影响机制与过程。结果表明:近6 a路基水分监测显示,虽然青藏高原年降雨量变化较大,夏季降雨引起土体表层水分短期显著波动,但长期路基含水量并未明显累积,路基蒸发、液态水与水汽运移显著;在未来湿化背景下,年降雨量增大导致地表潜热增大地表土壤热通量减小,降雨增大导致的热传导通量减小量比液态水对流热通量增大更大,人为冻土上限抬升;降雨增加缓解了路基工程对下伏多年冻土的热扰动,但降雨增加导致活动层水分累积,增大路基冻胀和融沉灾害风险。     

藏中联网后西藏电网安全稳定特性及控制策略分析

500 k V藏中联网工程投运后,西藏电网与西南主网联为一体,解决了长期困扰西藏地区的缺电问题。然而,联网初期由于长链式交流通道稳定水平低和柴拉直流与交流通道交互等因素的影响,西藏电网产生了新的安全稳定问题。针对藏中联网工程投运后存在的典型安全问题进行分析,如柴拉直流与交流通道交互影响、西藏电网负荷特性对藏中孤网的影响及500 k V/220 k V电磁环网的影响,讨论其安全稳定控制策略。     

西藏冈底斯西段松多复式岩体锆石U-Pb定年及地球化学特征

冈底斯岩浆岩带的岩石成因和动力学过程对于揭示新特提斯洋俯冲、印度-亚洲大陆碰撞和之后的高原隆升具有重要意义.通过对松多区岩体地球化学和锆石LA-ICP-MS U-Pb定年研究,结果表明:二长花岗斑岩锆石206 Pb/238 U年龄为(44.5±1.6) Ma(95％置信度,n=18,MSWD=1.5),黑云二长花岗斑岩...     

天然茶叶碱对运动员身体机能影响的研究

摘要：目的 本文通过实验运动员服用不同剂量的天然茶叶碱分析运动员基础身体指标、血常规、有氧运动、无氧运动下其身体机能状态的影响，采用方差分析的方法深入探讨服用茶叶碱对运动员的竞技技能和体能恢复效率的影响。方法 以三十六名身高体重接近，来自上海体育学院羽毛球专业二级男子运动员为实验对象，实验设计为随机单盲交叉的模式，将运动员平均分成3组，每组运动员分别服用茶叶碱的剂量分为高剂量、低剂量与安慰剂 3 种方式，测试内容包括基础指标测试、血液生理生化指标测试、有氧代谢测试和无氧能力测试，并采用SPSS17.0统计分析软件对结果分析。 结果 ：1、与服用前相比，表现无显著性差异（p>0.05），运动员总体重在服用不同剂量的茶叶碱后均表现出下降；不同剂量组的干预方式对运动员基础指标并无显著影响（p>0.05），但高剂量组表现出晨脉升高，安慰剂和低剂量组晨脉降低。去脂体重在服用茶叶碱后下降，并且随着服用剂量的升高而降低。2、与服用前相比，运动员血常规中RBC和HCT有所降低，但服用前后并无显著差异（p>0.05）；与高剂量组相比，低剂量组中服用茶叶碱前后的HB上升明显（p<0.01）。3、与服用前相比，不同剂量组运动员在呼吸交换率、相对最大摄氧量、无氧阈心率、每分钟通气量的表现值均呈现无显著性差异（p>0.05）；安慰剂组和高剂量组每分通气量的增长量显著高于低剂量组（p<0.05）。各血乳酸值在组内与组间均无显著性差异（p>0.05）。服用低剂量的茶叶碱其平均血乳酸值降低值大于安慰剂和高剂量组。4、与服用前相比，运动员在无氧运动的相对功率表现值稍微上升，但运动员在服用不同剂量茶叶碱后其相对峰功率、相对平均功率和功率递减率均无显著性差异（p>0.05）；服用后的高剂量组与安慰剂组无氧功血乳酸峰值相比服用前显著下降（p<0.05），而服用低剂量茶叶碱其血乳酸峰值较服用前有所上升，但并无显著性差异（p>0.05）； 结论 服用茶叶碱对与运动身体的基础指标和血常规并无显著影响，有利于体能恢复，可能对运动员的有氧运动有帮助，该研究有利于茶叶碱在营养保健品方面的推广。     

Extraction of Oxidative Enzymes from Green Tea Leaves and Optimization of Extraction Conditions

Oxidative enzymes, polyphenol oxidase (PPO) and peroxidase (POD), were extracted from tea leaves and their activities were assessed. The Taguchi approach was used for the design, optimization, and statistical analysis of PPO and POD extraction. It was found that PPO and POD have the highest activity at an extraction temperature of 50 °C, at pH = 9 and 5 for PPO and POD, respectively, a buffer solution concentration of 0.05 M, a buffer solution/tea leaves ratio of 3, a contact time of 2 min, and in the presence of 6 % polyvinylpyrrolidone and 5 % Tween® 80. The highest activities were 0.380 and 0.022 U mL⁻¹ for PPO and POD, respectively. Furthermore, PPO was completely inactivated after 30 min at 40 and 60 °C. In contrast, POD lost only 40 % of its activity after 30 min at 40 and 60 °C.     

藏东南地区冰川泥石流形成条件初步分析——以天摩沟冰川泥石流为例

针对融雪、降雨融雪等条件诱发的冰川泥石流形成过程,为了更好的认识藏东南地区冰川泥石流形成条件,选取藏东南地区天摩沟为研究对象,根据研究区流域特征、冰川覆盖面积以及气温等条件,在热化学、土力学以及流体力学等理论基础上,分析得到藏东南地区冰川泥石流在融雪条件下的起动流深阀值。结果表明:由于藏东南地区冰川泥石流沟分布高程影响,使得冰川泥石流沟所处的大气压为41. 0×103～54. 0×103kPa,使得雪线位置的冰川熔点上升至0. 352～0. 45℃;天摩沟冰川泥石流沟道冰碛物表层有效粒径(d10=10 mm)起动的临界流深为0. 04 m;天摩沟冰川泥石流沟道冰碛物发生冲蚀剪切破坏时的临界地表流深为其侵蚀厚度的3. 17倍;当天摩沟的降雨强度大于10. 22mm/h时可诱发冰川泥石流过程。研究成果为藏东南地区冰川泥石流的防治提供一定的参考。     

Effect of ethanol content on supercritical carbon dioxide extraction of caffeine from tea stalk and fiber wastes

This study presents the effect of ethanol content on supercritical carbon dioxide extraction of caffeine from tea plant wastes. Tea stalk and fiber wastes of Turkish tea plants that have no economical value were evaluated as raw material throughout the caffeine extraction experiments. These wastes were supplied from tea factory marked “Çaykur” in the east blacksea region. They were separately ground, sieved and dried at 105 °C temperature in an oven. Parameters affecting caffeine leaching from tea wastes were determined to be, ethanol flow rate, extraction time, extraction temperature, carbon dioxide flow rate, process pressure and particle size. The maximum yield of caffeine from tea stalk wastes and fiber wastes were 14.95 mg/g tea stalk and 18.92 mg/g tea fiber, respectively. When the supercritical extraction conditions used of ethanol as cosolvent have been compared with the conditions of used only carbon dioxide, approximately the same yield has been reached at 2 h extraction period instead of 7 h. Beside of saving of the time and the amount of carbon dioxide, the supercritical extraction yield with cosolvent increase had been recorded as 62.5% and 63.1%, respectively, in comparison with the chloroform extraction as conventional method of tea stalk and fiber wastes.     

THE EFFECT OF TEMPERATURE ON THE RHEOLOGY OF BUTTER, A SPREADABLE BLEND AND SPREADS

The texture of lipid-based food materials is an important topic for investigation. In this study, the rheological properties of five edible fats were determined. A puncture test was performed to investigate the rheological properties of the food materials at 5C and at 19C using a texture analyzer. The force-displacement measurements were converted to stress–strain by assuming incompressibility of edible fat food materials in a linear viscoelastic region (LVR). Young's modulus of each edible fat was calculated using stress–stain curves in a LVR. Shear elastic moduli of edible fats in a LVR were obtained using a rheometer. Further to that the effect of temperature on storage modulus and loss modulus and creep test were obtained using a rheometer. The tests showed good correlation between Young's modulus and shear elastic modulus for each material. The mechanical properties correlated well with the structural properties of each of the materials.

PRACTICAL APPLICATIONS

The texture of butter, blends and spreads is determined by temperature, rheological properties, processing conditions and the composition of the material. Our research investigated the effect of temperature on the rheological properties of these foods. The results may be used to model the relationship between the microstructure and mechanical properties of the fat crystal network.     

光度法测定茶叶中铅结果的不确定度分析

对4- (2-吡啶偶氮)-间苯二酚(PAR)分光光度法测定茶叶中铅含量的方法进行不确定度评价。通过分析不确定度来源和量化计算,得到分析方法的扩展不确定度为4.2 μ g/g。茶叶中铅含量可表示为(40±4.2) μ g/g。