Examination of a pre-exercise, high energy supplement on exercise performance

Background  

The purpose of this study was to examine the effect of a pre-exercise high energy drink on reaction time and anaerobic power in competitive strength/power athletes. In addition, the effect of the pre-exercise drink on subjective feelings of energy, fatigue, alertness and focus was also explored.     

The effects of creatine pyruvate and creatine citrate on performance during high intensity exercise

Background

A double-blind, placebo-controlled, randomized study was performed to evaluate the effect of oral creatine pyruvate (Cr-Pyr) and creatine citrate (Cr-Cit) supplementation on exercise performance in healthy young athletes.

Methods

Performance during intermittent handgrip exercise of maximal intensity was evaluated before (pretest) and after (posttest) 28 days of Cr-Pyr (5 g/d, n = 16), Cr-Cit (5 g/d, n = 16) or placebo (pla, 5 g/d, n = 17) intake. Subjects performed ten 15-sec exercise intervals, each followed by 45 sec rest periods.

Results

Cr-Pyr (p < 0.001) and Cr-Cit (p < 0.01) significantly increased mean power over all intervals. Cr-Cit increased force during the first and second interval (p < 0.01) compared to placebo. The effect of Cr-Cit on force decreased over time and the improvement was not significant at the sixth and ninth interval, whereas Cr-Pyr significantly increased force during all intervals (p < 0.001). Cr-Pyr (p < 0.001) and Cr-Cit (p < 0.01) resulted in an increase in contraction velocity, whereas only Cr-Pyr intake significantly (p < 0.01) increased relaxation velocity. Oxygen consumption measured during rest periods significantly increased with Cr-Pyr (p < 0.05), whereas Cr-Cit and placebo intake did not result in significant improvements.

Conclusion

It is concluded that four weeks of Cr-Pyr and Cr-Cit intake significantly improves performance during intermittent handgrip exercise of maximal intensity and that Cr-Pyr might benefit endurance, due to enhanced activity of the aerobic metabolism.     

储氢合金对GAP基高能固体推进剂性能的影响

在聚叠氮缩水甘油醚(GAP)基固体推进剂体系中,采用储氢合金取代不同含量的微米级铝粉,获得无孔的高能固体推进剂。采用扫描电镜表征了含储氢合金的GAP基固体推进剂的微观形貌,采用药块分别测试了推进剂的安全、力学、静态燃烧性能和爆热,并采用BSFΦ75发动机测试了动态燃烧性能。结果表明,含储氢合金药块的密度比原配方的密度略低,内部结合更紧密。一定含量的储氢合金不影响原配方的安全性能和力学性能,可提高原配方的动、静态燃速。随着储氢合金质量分数从9%增加至18%(全部取代微米级铝粉),推进剂的静态燃速无明显变化。     

含能交联剂对PBT高能推进剂力学性能的影响

以小分子交联剂作对比,重点研究了含能大分子多元醇交联剂PBT(3,3–双(叠氮甲基)氧杂环丁烷与四氢呋喃(BAMO–THF)共聚醚)三元醇(TBT)对PBT高能固体推进剂力学性能的影响。结果表明:1采用小分子交联剂,PBT推进剂具有较高的拉伸强度与模量;同时,小分子交联剂是一种键合剂,可有效阻止推进剂在断裂拉伸时基体与填料之间的"脱湿"。2采用含能大分子交联剂,PBT推进剂具有良好的最大伸长率,但断裂拉伸时推进剂的"脱湿"现象十分严重;随含能交联剂含量的变化,PBT推进剂热稳定性基本不变。     

硝酸三氮烷胺高能离子液体的合成及性能研究

以偏二甲肼为原料,经季铵化及复分解反应得到一种高能离子液体硝酸三氮烷胺,其结构组成经质谱和元素分析进行表征,采用差热–热重分析(DSC–TGA)研究了化合物的热稳定性,通过吉布斯最小自由能对其理论比冲进行了计算,并建立了该产物纯度的分析方法。结果表明:该化合物对高温比较敏感,热分解温度为146℃;用四氧化二氮为作氧化剂时,硝酸三氮烷胺/四氧化二氮的比冲性能优于偏二甲肼/四氧化二氮;所建立的该高能离子液体化合物的纯度分析方法准确可靠,有利于有效控制产品质量。     

Influence of an alkalizing supplement on markers of endurance performance using a double-blind placebo-controlled design

Background

Previous research has shown that ingestion of substances that enhance the body's hydrogen ion buffering capacity during high intensity exercise can improve exercise performance. The present study aimed to determine whether the chronic ingestion of an alkalizing supplement, which purports to enhance both intracellular and extracellular buffering capacity, could impact cardiorespiratory and performance markers in trained Nordic skiers.

Methods

Twenty-four skiers (12 men, 12 women), matched for upper body power (UBP), were split into treatment and placebo groups. The treatment group ingested Alka-Myte^?-based alkalizing tablets (1 tablet/22.7 kg body mass/day) over seven successive days while the placebo group consumed placebo tablets (i.e., no Alka-Myte^?) at the same dosage. Prior to tablet ingestion (i.e., pre-testing), both groups completed a constant power UBP test, three successive 10-sec UBP tests, and then a 60-sec UBP test. Next, skiers completed the 7-day ingestion of their assigned tablets followed immediately by a repeat of the same UBP tests (i.e., post-testing). Neither the skiers nor the researchers were aware of which tablets were being consumed by either group until after all testing was complete. Dependent measures for analysis included heart rate (HR), oxygen consumption (VO₂), minute ventilation (V_E), blood lactate (LA), as well as 10-sec (W10, W) and 60-sec (W60, W) UBP. All data were evaluated using a two-factor multivariate repeated measures ANOVA with planned contrasts for post-hoc testing (alpha = 0.05).

Results

Post-testing cardiorespiratory (HR, VO₂, V_E) and LA measures for the treatment group tended to be significantly lower when measured for both constant power and UBP60 tests, while measures of both 10-sec (W10: 229 to 243 W) and 60-sec UBP (W60: 190 to 198 W) were significantly higher (P < 0.05). In contrast, there were no significant changes for the placebo group (P > 0.05).

Conclusions

Following the 7-day loading phase of Alka-Myte^?-based alkalizing tablets, trained Nordic skiers experienced significantly lower cardiorespiratory stress, lower blood lactate responses, and higher UBP measures. Thus, the use of this supplement appeared to impart an ergogenic benefit to the skiers that may be similar to the effects expected from consuming well-studied extracellular buffering agents such as sodium bicarbonate.     

高性能聚乙烯纤维的生产、性能与应用

简述了国内外高性能聚乙烯纤维的生产概况,介绍了高性能聚乙烯纤维的性能,讨论了该纤维在各行业的应用,并对其应用前景进行了探讨和预测。     

Structural of BCTZ nanowires and high performance BCTZ-based nanogenerator for biomechanical energy harvesting

Owing to its excellent piezoelectric and ferroelectric properties, (Ba,Ca)(Ti,Zr)O₃ (BCTZ) family is considered as one of the most promising piezoelectric materials to replace the lead-based piezoelectrics, such as Pb(Zr,Ti)O₃ et al.. In this study, a BCTZ nanowires (NWs) based piezoelectric nanogenerator (NG) was fabricated. BCTZ NWs were prepared by an electrospinning technique. The NG achieved an excellent piezoelectric performance with a maximum open-circuit voltage of 0.65 V and short-circuit current of 2.2 nA by bending periodically. Furthermore, the NG obtained a maximum voltage of 2.2 V and current of 90 nA by tapping it. Results indicate that the lead-free BCTZ has a huge application potential in biomechanical energy harvesting.     

The acute effects of the thermogenic supplement Meltdown on energy expenditure,fat oxidation,and hemodynamic responses in young,healthy males

The purpose of this study was to evaluate the effects of a thermogenic supplement, Meltdown, on energy expenditure, fat oxidation, and hemodynamics before and after maximal treadmill exercise. In a double-blind, randomized, placebo-controlled, cross-over design, 12 male participants underwent two testing sessions after consuming either the Meltdown or placebo supplement. While in a fasted state, participants rested for one hour, orally ingested either Meltdown or placebo and rested for another hour, performed a maximal treadmill exercise test, and then rested for another hour. Throughout the testing protocol, resting energy expenditure (REE) and respiratory exchange ratio (RER) were assessed. In addition, heart rate (HR) and blood pressure (BP) were assessed before and after exercise. Meltdown increased REE significantly more than placebo at 45 min (1.44 ± 0.25 vs. 1.28 ± 0.23 kcal/min; p = 0.003), 60 min (1.49 ± 0.28 vs. 1.30 ± 0.22 kcal/min; p = 0.025), and 120 min (1.51 ± 0.26 vs. 1.33 ± 0.27 kcals/min; p = 0.014) post-ingestion. Meltdown significantly decreased RER at 30 min (0.84 ± 0.03 vs. 0.91 ± 0.04; p = 0.022) and 45 min post-ingestion (0.82 ± 0.04 vs. 0.89 ± 0.05; p = 0.042), and immediately post-exercise (0.83 ± 0.05 vs. 0.90 ± 0.07; p = 0.009). Furthermore, over the course of the evaluation period, area under the curve assessment demonstrated that REE was significantly increased with Meltdown compared to placebo (992.5 ± 133.1 vs. 895.1 ± 296.1 kcals; p = 0.043), while RER was significantly less than placebo (5.55 ± 0.61 vs. 5.89 ± 0.44; p = 0.002) following ingestion. HR and BP were not significantly affected prior to exercise with either supplement (p > 0.05) and the exercise-induced increases for HR and BP decreased into recovery and were not different between supplements (p > 0.05). These data suggest that Meltdown enhances REE and fat oxidation more than placebo for several hours after ingestion in fully rested and post-exercise states without any adverse hemodynamic responses associated with maximal exercise.     

Simultaneously achieving high energy storage performance and low electrostrictive strain in BT-based ceramics

Dielectric ceramics with high recoverable energy storage density (W_rec) and high energy storage efficiency (η) are urgently needed due to their potential application in pulse capacitor devices. However, the low  η and breakdown strength (BDS) have produced a bottleneck for achieving high W_rec at high electric field. Here, we introduce Bi(Mg_0.5Ti_0.5)O₃ (BMT) into Ba(Ti_0.92Sn_0.08)O₃ (BTS) matrix to enhance the relaxor character of BTS–xBMT and reduce the electrostrictive strain generated during electric field loading. The enhanced relaxor character is beneficial for increasing the efficiency, whereas the reduced electrostrictive strain is profitable to increase the BDS. Furthermore, the BDS is significantly improved by the polymer viscous rolling process. Finally, the electrostrictive effect was considerably lowered in an optimized BTS–0.1BMT composition. More crucially, a high W_rec of 4.34 J/cm³ was attained accompanied by excellent temperature stability (variation ≤±5% between 30 and 120°C). The current results show that the developed dielectric ceramics can be used in pulse capacitor devices for energy storage.     

关于高性能水泥的探讨

从混凝土的使用性能方面界定高性能水泥的含义，并且阐述了水泥高性能的主要途径，即优化熟料矿物组成，选择合理的粉磨工艺，采用非熟料的其它组分材料对水泥改性。     

Targeted doping builds a high energy density composite piezoceramics for energy harvesting

To build piezoceramics with high transduction coefficient (d₃₃ × g₃₃) is the key to improve the power generation capability of piezoelectric energy harvester. Here, a new targeted doping strategy has been proposed to significantly increase the energy density of piezoceramics. Taking the modification of 0.2Pb(Zn_1/3Nb_2/3)O₃-0.8Pb(Zr_0.5Ti_0.5)O₃ (PZN-PZT) as an example, dual functions can be achieved by introducing appropriate amount of target-doped (Zn_0.1Ni_0.9)TiO₃ (ZTN9) based on its pyrolysis characteristics. On the one hand, Ni²⁺ ions enter the perovskite matrix to replace Zn²⁺ ions to form equivalent doping; on the other hand, it induces the formation of 0-3 ZnO/perovskite composite structure, and both of which promote the large increase in d₃₃ × g₃₃ due to the changes in the domain configuration are more conducive to the ferro-/piezoelectricity. In all compositions, 0.67 mol% ZTN9 added specimen has a maximum value (12 433 × 10⁻¹⁵ m²/N) of the d₃₃ × g₃₃. The cantilever piezoelectric energy harvester fabricated with this material generates up to 4.50 μW/mm³ of power density at 1 g acceleration, which is capable of quickly charging a 47 μF electrolytic capacitor and then lit 135 parallel-connected commercial blue light-emitting diodes (LEDs), showing its important application in implementing self-powered microsensors.     

The effect of exercise on plasma high density lipoproteins

The influence of vigorous activity in man on plasma lipids and lipoproteins is reviewed, with particular emphasis on high density lipoproteins. Both cross sectional and longitudinal (or training) studies have been reported, many of them of less than ideal design. Nonetheless, a consistent pattern emerges in which increased exercise levels lead to lower plasma concentrations of triglycerides and very low density lipoproteins, and of low density lipoproteins. High density lipoprotein levels increase. Sometimes, but not uniformly, plasma total cholesterol level falls as the result of these changes. The increase in plasma high density lipoprotein appears to be the result largely of an increase in the less dense HDL₂ subfraction. Plasma apolipoprotein A-I levels (but not apo-A-II levels) seem to increase concomitantly. The precise biochemical mechanism responsible for these changes has not been elucidated; but the recent finding of increased lipoprotein lipase activity in adipose tissue and muscle of endurance runners suggests that increased lipolytic rate of trigly ceride-rich lipoproteins may be an initial step in a sequence of events leading to higher plasma levels of HDL₂.     

高性能水泥与高性能混凝土的协调发展

１发展高性能混凝土（HPC）势在必行高性能混凝土是近期混凝土技术发展的主要方向，国外学者曾称之为２１世纪混凝土。挪威于１９８６年首先对此进行了研究，在１９９０年由美国国家标准与技术研究院（NIST）与美国混凝土学会（ACI）共同主办的一次研讨会上正式定名。由于高性能混凝土具有综合的优异技术特性，引起了国内外材料界与工程界的广泛重视与关注。我国１９９２年开始重视，现已在大城市商品混凝土和重要建筑中较普遍采用，形势很好。何谓高性能混凝土？美国混凝土学会（ACI）认为：HPC是用优质水泥、集料、水和活性细掺料…     

高保湿有机硅蜡的合成与性能研究

通过两步法以端氢硅油和1-十八烯为原料合成高保湿有机硅蜡,通过单因素试验和正交试验探究反应物摩尔比、反应温度和反应时间对转化率的影响。利用红外光谱对产物的结构进行表征,并研究了其保湿性。实验结果表明反应温度对转化率的影响较大,较佳反应条件为:n(端氢含氢硅油)∶n(1-十八烯)=1∶24,反应温度125℃,反应时间5 h,在此条件下转化率达92.87%。由红外光谱图可知合成产物为目标产物。将高保湿有机硅蜡的保湿性与市售有机硅蜡产品进行比较,结果显示高保湿有机硅蜡具有更优良的保湿性。     

Development of high performance, Pd-based, three way catalysts

The use of Pd in three-way catalytic (TWC) converters of automobiles presents serious limitations which are related to sintering, poisoning and excessive selectivity for HC and CO oxidation, making NO_x reduction difficult. In the present work, an advanced automotive exhaust catalyst design is applied which reduces, to a large extent, these shortcomings of Pd. This catalyst is based on dispersion of Pd on YSZ (ZrO₂ stabilized with 8 mol-% Y₂O₃) forming the internal layer of a three-layer washcoat. The external layers contain small quantities of Pt and Rh dispersed on suitable supports, such as γ-Al₂O₃ and W⁶⁺-doped TiO₂, respectively. This scheme offers a high performance TWC with low light-off temperature for the conversion of all three pollutants (CO, HC and NO_x), enhanced poisoning tolerance and improved thermal resistance.