Background： Smokeless tobacco is widely used by athletes to enhance performance. Nicotine is a central nervous system stimulant and acts on cardiocirculatory and metabolic systems, involving tissue blood flow and cir...Background： Smokeless tobacco is widely used by athletes to enhance performance. Nicotine is a central nervous system stimulant and acts on cardiocirculatory and metabolic systems, involving tissue blood flow and circulatory vasoreactivity. The aim of this study was to investigate the effects of the oral smokeless tobacco （Swedish snus （SS）） on the perception of fatigue and time to exhaustion （TTE） during moderate-intensity aerobic exercise. Methods： Fourteen healthy non-tobacco male users were recruited for a double-blind, controlled crossover design （SS vs. snus placebo （SP））. Subjects were tested for 3 sessions： experimental session 1 （Exp 1） consisted of an incremental test to determine the maximal aerobic power out-put （Wmax）, whereas Exp2 and Exp3 consisted of exercising at 65%Wmax until exhaustion in SS or SP conditions. During Exp2 and Exp3, muscle and cerebral oxygenation was assessed by means of near-infrared spectroscopy, and the rating of perceived exertion （RPE） was recorded. Results： Comparing SS with SP tests, significant differences （p 〈 0.05） were found in the values of cerebral （-3%） and muscular tissues oxygenation （-4%） in the first 30 min of exercise. The RPE values were not significantly different between the 2 conditions （SS vs. SP）. No significant difference was found in TTE （SS： 54.25 ± 21.84 min; SP： 50.01 ± 17.03 min）. Conclusion： This study showed that muscular and cerebral oxygenation increased significantly with snus administration during an endurance exercise until exhaustion, but this did not affect fatigue perception and TTE. The results showed that snus could not be considered an ergogenic substance in non-tobacco users.2018 Published by Elsevier B.V. on behalf of Shanghai University of Sport. This is an open access article under the CC BY-NC-ND license. （http：//creativecommons.org/licenses/by-nc-nd/4.0/）.展开更多
The stability of natural slope was analyzed on the basis of limit analysis. The sliding model of a kind of natural slope was presented. A new kinematically admissible velocity field for the new sliding model was const...The stability of natural slope was analyzed on the basis of limit analysis. The sliding model of a kind of natural slope was presented. A new kinematically admissible velocity field for the new sliding model was constructed. The stability factor formulation by the upper bound theorem leads to a classical nonlinear programming problem, when the external work rate and internal energy dissipation were solved, and the constraint condition of the programming problem was given. The upper bound optimization problem can be solved efficiently by applying a nonlinear SQP algorithm, and stability factor was obtained, which agrees well with previous achievements.展开更多
This study compared two learning strategies (word-part method and context-clue method) for Chinese EFL learners' vocabulary acquisition and retention. The results revealed that the context-clue group yielded signi...This study compared two learning strategies (word-part method and context-clue method) for Chinese EFL learners' vocabulary acquisition and retention. The results revealed that the context-clue group yielded significantly higher scores on the immediate posttests than the word-part group. The context-clue group outperformed on the immediate and delayed fill-in-the-blank posttests than the word-part group. As regards gender effects, no overall differences were found between male and female students. Additionally, the pretest had positive effects on two posttests for the female students, but negative effects for the male students. In educational settings, the context-clue method is highly suggested for explicit vocabulary instruction.展开更多
We present a study of the electric field effect on electrochemically grown ultrathin, straight platinum nanowires with minimum diameter of 15 nm and length in the micrometer range, synthesized on a silicon oxide subst...We present a study of the electric field effect on electrochemically grown ultrathin, straight platinum nanowires with minimum diameter of 15 nm and length in the micrometer range, synthesized on a silicon oxide substrate between metal electrodes in H2PtC16 solution. The influence of the concentration of the platinum- containing acid and the frequency of the applied voltage on the diameter of the nanowires is discussed with a corresponding theoretical analysis. We demonstrate for the first time that the electric field profile, provided by the specific geometry of the metal electrodes, dramatically influences the growth and morphology of the nanowires. Finally, we provide guidelines for the controlled fabrication and contacting of straight, ultrathin metal wires, eliminating branching and dendritic growth, which is one of the main shortcomings of the current bottom-up nanotechnology. The proposed concept of self-assembly of thin nanowires, influenced by the electric field, potentially represents a new route for guided nanocontacting via smart design of the electrode geometry. The possible applications reach from nanoelectronics to gas sensors and biosensors.展开更多
基金supported by research funds allocated to the following departments at the University of Verona:Neurosciences,Biomedicine and Movement Sciences,and Diagnostic and Public Health
文摘Background： Smokeless tobacco is widely used by athletes to enhance performance. Nicotine is a central nervous system stimulant and acts on cardiocirculatory and metabolic systems, involving tissue blood flow and circulatory vasoreactivity. The aim of this study was to investigate the effects of the oral smokeless tobacco （Swedish snus （SS）） on the perception of fatigue and time to exhaustion （TTE） during moderate-intensity aerobic exercise. Methods： Fourteen healthy non-tobacco male users were recruited for a double-blind, controlled crossover design （SS vs. snus placebo （SP））. Subjects were tested for 3 sessions： experimental session 1 （Exp 1） consisted of an incremental test to determine the maximal aerobic power out-put （Wmax）, whereas Exp2 and Exp3 consisted of exercising at 65%Wmax until exhaustion in SS or SP conditions. During Exp2 and Exp3, muscle and cerebral oxygenation was assessed by means of near-infrared spectroscopy, and the rating of perceived exertion （RPE） was recorded. Results： Comparing SS with SP tests, significant differences （p 〈 0.05） were found in the values of cerebral （-3%） and muscular tissues oxygenation （-4%） in the first 30 min of exercise. The RPE values were not significantly different between the 2 conditions （SS vs. SP）. No significant difference was found in TTE （SS： 54.25 ± 21.84 min; SP： 50.01 ± 17.03 min）. Conclusion： This study showed that muscular and cerebral oxygenation increased significantly with snus administration during an endurance exercise until exhaustion, but this did not affect fatigue perception and TTE. The results showed that snus could not be considered an ergogenic substance in non-tobacco users.2018 Published by Elsevier B.V. on behalf of Shanghai University of Sport. This is an open access article under the CC BY-NC-ND license. （http：//creativecommons.org/licenses/by-nc-nd/4.0/）.
基金Project(2013CB036004)supported by the National Basic Research Program of ChinaProject(51178468)supported by the National Natural Science Foundation of China
文摘The stability of natural slope was analyzed on the basis of limit analysis. The sliding model of a kind of natural slope was presented. A new kinematically admissible velocity field for the new sliding model was constructed. The stability factor formulation by the upper bound theorem leads to a classical nonlinear programming problem, when the external work rate and internal energy dissipation were solved, and the constraint condition of the programming problem was given. The upper bound optimization problem can be solved efficiently by applying a nonlinear SQP algorithm, and stability factor was obtained, which agrees well with previous achievements.
文摘This study compared two learning strategies (word-part method and context-clue method) for Chinese EFL learners' vocabulary acquisition and retention. The results revealed that the context-clue group yielded significantly higher scores on the immediate posttests than the word-part group. The context-clue group outperformed on the immediate and delayed fill-in-the-blank posttests than the word-part group. As regards gender effects, no overall differences were found between male and female students. Additionally, the pretest had positive effects on two posttests for the female students, but negative effects for the male students. In educational settings, the context-clue method is highly suggested for explicit vocabulary instruction.
文摘We present a study of the electric field effect on electrochemically grown ultrathin, straight platinum nanowires with minimum diameter of 15 nm and length in the micrometer range, synthesized on a silicon oxide substrate between metal electrodes in H2PtC16 solution. The influence of the concentration of the platinum- containing acid and the frequency of the applied voltage on the diameter of the nanowires is discussed with a corresponding theoretical analysis. We demonstrate for the first time that the electric field profile, provided by the specific geometry of the metal electrodes, dramatically influences the growth and morphology of the nanowires. Finally, we provide guidelines for the controlled fabrication and contacting of straight, ultrathin metal wires, eliminating branching and dendritic growth, which is one of the main shortcomings of the current bottom-up nanotechnology. The proposed concept of self-assembly of thin nanowires, influenced by the electric field, potentially represents a new route for guided nanocontacting via smart design of the electrode geometry. The possible applications reach from nanoelectronics to gas sensors and biosensors.
