废蚕丝中提取丝胶工艺研究     

蓝建京  甘配芳 《河池学院学报》2011,31(5):56-60

通过对透析法、酸析法和冰冻法提取丝胶效果的比较,得出冰冻法是提取丝胶的较好的方法,其最佳的提取条件是:pH=4,-20℃,冰冻时间为13 h,丝胶液浓度为32.8%。  相似文献   

Maximal heart rate declines linearly with age independent of cardiorespiratory fitness levels     

Cemal Ozemek  Mitchell H. Whaley  W. Holmes Finch  Leonard A. Kaminsky 《European Journal of Sport Science》2017,17(5):563-570

There have been many conflicting observations between the linear or curvilinear decline in maximal heart rate (HR_max) with age. The aim of this study was to determine if linear or curvilinear equations would better describe the decline in HR_max with age in individuals of differing cardiorespiratory fitness (CRF) levels. Treadmill cardiopulmonary exercise test (CPX) results from participants (1510 men and 1134 women; 18–76 years) free of overt cardiovascular disease were retrospectively examined using cross-sectional and longitudinal study designs. Participants completing ≥2 CPX with ≥1 year between test dates were included in the longitudinal analysis (325 men and 150 women). Linear and quadratic regressions were applied to age and HR_max for the whole cohort and respective CRF groups (high, moderate, and low, relative to age and gender normative values). To test for differences among linear, quadratic, and polynomial equations, the change in R² (cross-sectional analysis) and Bayesian information criterion (BIC) (longitudinal analysis) from the linear to the more complex models were calculated. The quadratic or polynomial regression in the cross-sectional analysis, marginally improved the variance in HR_max explained by age compared to the linear regression for the whole cohort (0.2%), moderate fit group (0.3%), and low fit group (0.8%). With no improvements in the high fit group. BIC did not improve for any CRF category in the longitudinal analysis. In conclusion, the minimal differences among linear, quadratic, and polynomial equations in the respective CRF groups, emphasizes the use of linear prediction equations to estimate HR_max.  相似文献   

4周下肢间歇负压干预对优秀赛艇运动员心率变异性和儿茶酚胺的影响     

董徽徽  高炳宏 《上海体育学院学报》2020,(4):78-83

目的探讨下肢间歇负压干预对赛艇运动员心率变异性(HRV)相关指标和儿茶酚胺的影响。方法将国家赛艇队的14名运动员分为试验组和对照组,试验组运动员每周用间歇负压干预5 d,持续4周,对照组无其他干预方式。试验期间均对2组运动员进行HRV相关指标和儿茶酚胺的测试。结果试验前2组运动员各指标均无统计学差异。开始干预后2组的变化如下:①在时域指标中,试验组正常窦性R-R间期标准差(SDNN)在第3周时高于对照组(P<0.05)。②在频域指标中,试验组高频(HF)值在第2周和第3周时高于对照组(P<0.05),而其高频与低频比(LF/HF)在第1、3和4周时低于对照组(P<0.05)。③2组儿茶酚胺组内、组间比较均无统计学差异,但试验组儿茶酚胺下降程度比对照组高。结论4周的间歇负压干预对运动员自主神经系统功能的恢复有明显促进作用,对儿茶酚胺的分泌也具有抑制趋势;这有利于降低运动员心脏负荷,促进运动后的生理恢复。  相似文献   

优秀女子足球运动员间歇性恢复能力的评价研究     

秦旸  张娜 《南京体育学院学报(社会科学版)》2016,(2):103-107

目的：：探讨运用限定级数YO-YO IR2测试以及心率恢复速率评价我国优秀女足运动员的间歇恢复能力。方法：运用测试法对2013年冬训期间的10名国家女足运动员进行YO-YO IR2测试、心率监控以及比赛监测，采集运动员测试跑动距离、心率特征以及比赛中高强度跑动距离，进行统计学分析。结论：女足运动员YO-YO IR2测试结果以及心率恢复速率与比赛中的高强度跑动能力具有紧密相关性，提示YO-YO IR2测试以及心率监控可以作为评价女足运动员间歇性恢复能力的有效方法。与传统的力竭性YO-YO IR2测试法相比，采用限定级数的YO-YO IR2测试后的心率恢复速率评价更易于女足运动员接受，在训练中具有更好的适用性。  相似文献   

Thermoneutral immersion exercise accelerates heart rate recovery: A potential novel training modality     

Mauricio Garzon  Olivier Dupuy  Laurent Bosquet  Anil Nigam  Alain Steve Comtois  Martin Juneau 《European Journal of Sport Science》2017,17(3):310-316

This study compared heart rate recovery (HRR) after incremental maximal exercise performed at the same external power output (P_ext) on dry land ergocycle (DE) vs. immersible ergocycle (IE). Fifteen young healthy participants (30?±?7 years, 13 men and 2 women) performed incremental maximal exercise tests on DE and on IE. The initial P_ext on DE was 25?W and was increased by 25?W/min at a pedalling cadence between 60 and 80?rpm, while during IE immersion at chest level in thermoneutral water (30°C), the initial P_ext deployment was at a cadence of 40?rpm which was increased by 10?rpm until 70?rpm and thereafter by 5?rpm until exhaustion. Gas exchange and heart rate (HR) were measured continuously during exercise and recovery for 5?min. Maximal HR (DE: 176?±?15 vs. IE 169?±?12?bpm) reached by the subjects in the two conditions did not differ (P?>?.05). Parasympathetic reactivation parameters (ΔHR from 10 to 300?s) were compared during the DE and IE HR recovery recordings. During the IE recovery, parasympathetic reactivation in the early phase was more predominant (HRR at Δ10–Δ60?s, P?<?.05), but similar in the late phase (HRR at Δ120–Δ300?s, P?>?.05) when compared to the DE condition. In conclusion, incremental maximal IE exercise at chest level immersion in thermoneutral water accelerates the early phase parasympathetic reactivation compared to DE in healthy young participants.  相似文献   

Effects of heat acclimation on hand cooling efficacy following exercise in the heat     

Elizabeth L. Adams  Lesley W. Vandermark  J. Luke Pryor  Riana R. Pryor  Rachel M. VanScoy  Craig R. Denegar 《Journal of sports sciences》2017,35(9):828-834

This study examined the separate and combined effects of heat acclimation and hand cooling on post-exercise cooling rates following bouts of exercise in the heat. Seventeen non-heat acclimated (NHA) males (mean ± SE; age, 23 ± 1 y; mass, 75.30 ± 2.27 kg; maximal oxygen consumption [VO₂ max], 54.1 ± 1.3 ml·kg^?1·min^?1) completed 2 heat stress tests (HST) when NHA, then 10 days of heat acclimation, then 2 HST once heat acclimated (HA) in an environmental chamber (40°C; 40%RH). HSTs were 2 60-min bouts of treadmill exercise (45% VO₂ max; 2% grade) each followed by 10 min of hand cooling (C) or no cooling (NC). Heat acclimation sessions were 90–240 min of treadmill or stationary bike exercise (60–80% VO₂ max). Repeated measures ANOVA with Fishers LSD post hoc (α < 0.05) identified differences. When NHA, C (0.020 ± 0.003°C·min^?1) had a greater cooling rate than NC (0.013 ± 0.003°C·min^?1) (mean difference [95%CI]; 0.007°C [0.001,0.013], P = 0.035). Once HA, C (0.021 ± 0.002°C·min^?1) was similar to NC (0.025 ± 0.002°C·min^?1) (0.004°C [?0.003,0.011], P = 0.216). Hand cooling when HA (0.021 ± 0.002°C·min^?1) was similar to when NHA (0.020 ± 0.003°C·min^?1) (P = 0.77). In conclusion, when NHA, C provided greater cooling rates than NC. Once HA, C and NC provided similar cooling rates.  相似文献   

Objective and subjective methods for quantifying training load in wheelchair basketball small-sided games     

Aitor Iturricastillo  Cristina Granados  Asier Los Arcos  Javier Yanci 《Journal of sports sciences》2017,35(8):749-755

The aim of the present study was to analyse the training load in wheelchair basketball small-sided games and determine the relationship between heart rate (HR)-based training load and perceived exertion (RPE)-based training load methods among small-sided games bouts. HR-based measurements of training load included Edwards’ training load and Stagno’s training impulses (TRIMP_MOD) while RPE-based training load measurements included cardiopulmonary (session RPEres) and muscular (session RPEmus) values. Data were collected from 12 wheelchair basketball players during five consecutive weeks. The total load for the small-sided games sessions was 67.5 ± 6.7 and 55.3 ± 12.5 AU in HR-based training load (Edwards’ training load and TRIMP_MOD), while the RPE-based training loads were 99.3 ± 26.9 (session RPEres) and 100.8 ± 31.2 AU (session RPEmus). Bout-to-bout analysis identified greater session RPEmus in the third [P < 0.05; effect size (ES) = 0.66, moderate] and fourth bouts (P < 0.05; ES = 0.64, moderate) than in the first bout, but other measures did not differ. Mean correlations indicated a trivial and small relationship among HR-based and RPE-based training loads. It is suggested that HR-based and RPE-based training loads provide different information, but these two methods could be complementary because one method could help us to understand the limitations of the other.  相似文献   

银行监督、利率管制与中小企业融资   总被引：1，自引：0，他引：1  

刘宇光 《徐州师范大学学报(哲学社会科学版)》2005,31(3):85-88,92

自有资金较少的中小企业只有在受到监督的情况下才能得到贷款。而监督需要成本,在监督成本较高的情况下,银行就不愿意发放监督贷款,中小企业就很难得到融资。只有进行利率市场化改革和降低监督成本,才能解决中小企业融资难的问题。  相似文献   

探讨人民币汇率制度的发展方向     

魏星 《徐州师范大学学报(哲学社会科学版)》2002,28(3):34-37

经济全球化和金融自由化推动了金融全球化的迅速发展。金融环境的变车呼唤着我国僵化的人民币汇率由有管理的浮动制度向真正的管理浮动制度转变。尤其进入新世纪，我国在经历了经济制度改革、创新后，经济日新月异，无论从GDP的年增长速度、国际收支状况，还是从金融市场的发展角度看，都具备了汇率制度改进的条件。在充分利用这一改革契机的同时，我们应该意识到经济、金融环境稳定对于一国改革、发展的重要性，认识到改革方式会直接制约改革成铲，所以汇率制度的发展应坚持循序渐进的原则，不宜完全浮动化,而适宜采取汇率目标区的形式，并注重加强亚洲地区的金融合作，增强汇率制度的稳定性。  相似文献   

关于义务教育办学效益的思考   总被引：2，自引：0，他引：2  

阎庆东 《民族教育研究》2002,13(2):57-59

办学效益的问题长期以来未得到应有的重视。义务教育办学效率评价指标包括义务教育的发展水平指标，投入水平指标，管理水平指标和教育质量水平指标，评价义务教育的办学效益高低，其中一个重要指标应是按时毕业率。  相似文献