文言课刺激学生思维之我见

文言诗文教学是中学语文教学的重点,可是多数学生对文言课不感兴趣,文言教学索然无味,那么怎样激发学生学习文言的热情,给文言教学增添活力呢？笔者认为文言课一定要不停地刺激学生的思维,刺激学生的思维可采取情感法、幽默法、形象法、质疑法、反弹法、故事法等。     

ISSR markers based on GA and AG repeats reveal genetic relationship among rice varieties tolerant to drought, flood, or salinity

Drought,flood,salinity,or a combination of these limits rice production.Several rice varieties are well known for their tolerance to specific abiotic stresses.We determined genetic relationship among 12 rice varieties including 9 tolerant to drought,flood,or salinity using inter-simple sequence repeat (ISSR) markers.Based on all markers,the nine tolerant varieties formed one cluster distinct from the cluster of three control varieties.The salt-tolerant varieties were closest to two flood-tolerant varieties,and together they were distinct from the drought-tolerant varieties.(GA)8 YG was the most informative primer,showing the highest polymorphic information content (PIC) and resolving power (Rp).The drought-,flood-,and salt-tolerant varieties grouped in three distinct clusters within the group of tolerant varieties,when (GA)8 YG was used.Sabita was the only exception.The two aus varieties,Nagina22 and FR13A,were separated and grouped with the drought-and flood-tolerant varieties,respectively,but they were together in dendrograms based on other primers.The results show that ISSR markers associated with (GA)8 YG delineated the three groups of stress-tolerant varieties from each other and can be used to identify genes/new alleles associated with the three abiotic stresses in rice germplasm.     

耐镉根瘤菌的筛选

采用液体培养基摇床培养根瘤菌,研究了Cd处理对根瘤菌生长的影响.依时间进程测定培养液在600nm吸光度并绘制根瘤菌生长曲线.筛选到一株耐Cd根瘤菌菌株X.5和10 μmol/L Cd处理48h对苜蓿根瘤菌标准菌株USDA生长抑制率分别为38%和58%,而此浓度Cd处理对X菌株生长具有一定的促进作用.BTB反应鉴定结果表明,菌株USDA和X均为快生型根瘤菌.     

坑道操对坑道作业人员反应时昼夜节律及调整的研究

以现代时间生物学理论为指导,应用单个余弦法进行生物节律分析和数据统计,观察在坑道环境中,正常作息制和光暗倒相制下坑道作业人员反应时的昼夜节律相位情况,以及坑道操对反应时节律的相位影响特点及规律。结果表明在正常作息制条件下,反应时表现明显的昼夜节律（P〈0.05）。在光暗倒相状态下,坑道操组表现明显的昼夜节律（P〈0.05）,而对照组不具有明显的昼夜节律。坑道操对反应时具有明显的调节作用。     

Independence of reaction time and response force control during isometric leg extension

In this study, we examined the relative control of reaction time and force in responses of the lower limb. Fourteen female participants (age 21.2±1.0 years, height 1.62±0.05?m, body mass 54.1±6.1?kg; mean±s) were instructed to exert their maximal isometric one-leg extension force as quickly as possible in response to an auditory stimulus presented after one of 13 foreperiod durations, ranging from 0.5 to 10.0?s. In the ‘irregular condition’ each foreperiod was presented in random order, while in the ‘regular condition’ each foreperiod was repeated consecutively. A significant interactive effect of foreperiod duration and regularity on reaction time was observed (P?<?0.001 in two-way ANOVA with repeated measures). In the irregular condition the shorter foreperiod induced a longer reaction time, while in the regular condition the shorter foreperiod induced a shorter reaction time. Peak amplitude of isometric force was affected only by the regularity of foreperiod and there was a significant variation of changes in peak force across participants; nine participants were shown to significantly increase peak force for the regular condition (P?<?0.001), three to decrease it (P?<?0.05) and two showed no difference. These results indicate the independence of reaction time and response force control in the lower limb motor system. Variation of changes in peak force across participants may be due to the different attention to the bipolar nature of the task requirements such as maximal force and maximal speed.     

Cardiopulmonary loading in motocross riding

Abstract

The present study was designed to examine physiological responses during motocross riding. Nine Finnish A-level motocross riders performed a 15-min ride at a motocross track and a test of maximal oxygen uptake ([Vdot]O_2max) in the laboratory. Cardiopulmonary strain was measured continuously during the ride as well as in the [Vdot]O_2max test. During the ride, mean [Vdot]O₂ was 32 ml · kg^?1 · min^?1 (s = 4), which was 71% (s = 12) of maximum, while ventilation (V _E) was 73% (s = 15) of its maximum. The relative [Vdot]O₂ and V _E values during the riding correlated with successful riding performance (r = 0.80, P < 0.01 and r = 0.79, P < 0.01, respectively). Mean heart rate was maintained at 95% (s = 7) of its maximum. Mean blood lactate concentration was 5.0 mmol · l^?1 (s = 2.0) after the ride. A reduction of 16% (P < 0.001) in maximal isometric handgrip force was observed. In conclusion, motocross causes riders great physical stress. Both aerobic and anaerobic metabolism is required for the isometric and dynamic muscle actions experienced during a ride.     

Effect of target change during the simple attack in fencing

Abstract

The aim of this study was to test the effect that changing targets during a simple long lunge attack in fencing exerts on the temporal parameters of the reaction response, the execution speed, and the precision and the coordination of the movement pattern. Thirty fencers with more than 10 years of experience participated in this study. Two force platforms were used to record the horizontal components of the reaction forces and thereby to determine the beginning of the movement. A three-dimensional (3D) system recorded the spatial positions of the 9 markers situated on the fencer plus the epee, while a moving target was projected on a screen, enabling the control of the target change. The results indicated that when a target change is provoked the reaction time (RT), movement time (MT), and the time used in the acceleration phase of the centre of mass (CM) increases significantly with respect to the attack executed with a straight thrust. The speed and horizontal distance reached by the CM at the end of the acceleration phase (V_X(CM) and S_X(CM), respectively) significantly decreased, while the errors increased. However, the temporal sequence of the movement pattern did not appreciably change.     

Attentional focus effects on sprint start performance as a function of skill level

Abstract

Several researchers have demonstrated that an external focus of attention (about movement’s effects) during movement execution allowed better performances and learning of various motor tasks than an internal focus of attention (about movement itself). However, attentional focus effects have not been studied in tasks requiring explosive actions preceded by fast reaction time to a signal, such as a sprint start. We hypothesised that the beneficial effect of external focus of attention would be observed in the different stages of the sprint start (i.e. reaction time, block clearance and running) for both expert and novice sprinters. Novice and expert sprinters performed sprint starts followed by a 10 m sprint under three conditions: external focus instructions; internal focus instructions; and neutral instructions. The reaction time and the running time were significantly shorter in the external focus condition than in the internal focus condition, for both expert and novice participants. These results confirm the beneficial effect of an external focus of attention on the speed of movement execution. Moreover, they revealed that attentional focus influences movement preparation. Several hypotheses are proposed to account for these results, with reference to the processes that could be responsible for the observed effects.     

Sex and Athletic Status as Factors in Reaction Latency and Movement Time

Abstract

This study investigated the effects of sex and athletic status on reaction latencies and movement time. One hundred subjects, categorized into five groups of 20 subjects each—male athletes (MA), female athletes (FA), male nonathletes (MNA), female nonathletes (FNA), and control group (CG)—were tested over a period of five consecutive days. Several different types of incentives were used to ensure that subjects provided the fastest times possible. Two blocks of 25 trials were administered to each subject on each day. A 2 × 2 × 2 × 5 × 2 mixed factorial analysis of variance was used to test for between-subject differences of group (experimental/control), sex, and athletic status and for within-subject differences of days and blocks. The four dependent variables were reaction time (RT) mean, RT consistency, movement time (MT) mean, and MT consistency. Results did not support the classic finding of male superiority over females in RT/MT or athletes' superiority over nonathletes. Evidence of athletic superiority emerged, but for the first day of practice only. As subjects were allowed extended practice over a 5-day test period in which knowledge of results (KR) and other incentives were provided, differences in the experimental groups disappeared. Sex was the predominant factor in consistency, with males being less variable in RT (p = .02) performance than females. There were no sex differences in MT consistency.     

Children and Fitness: A Public Health Perspective: A Response

Abstract

The speed-accuracy operating curve was investigated in a movement precuing two- or four-choice reaction time task. Four levels of response preferences were manipulated with subject instructions and postresponse information: (a) accuracy, (b) reaction time latency, (c) accuracy and reaction time latency, and (d) no preference. Eighty subjects completed 480 discrete keypressing responses with the index and middle fingers of both hands. The mixed design mean reaction time analysis indicated faster performances for the reaction time latency and the accuracy and reaction time latency groups than the no preference group. Additionally, the percent correct analysis revealed two significant interactions: (a) Trial Block x Precue x Response Preference, and (b) Delay x Precue x Hand Position. Overall, the present findings provide partial support for the speed-accuracy operating curve predictions. Caution is advised when drawing chronometric inferences based only on reaction time data or when response accuracies are extremely high.