In a recent paper (Olah et al., 1985) we found that the active areas of UK Lac exhibited sometimes smali, sometimes large scale motions. In the case of the Sun it is well knovvn that new spots exhibit large proper motions while the old ones move almost together with the surrounding photosphere. On UK Lac both a newly formed active area and an existing old one showed rapid motions at the same time. A possible interpretation of this phenomenon is that new spots appeared in both the new and the old active areas simultaneously. This time coincidence may be aceidental, but if spots originate in dceper layers, than spots of common decp origin may appear in remote places of the stellar surface at the same time. Similar phenomena are seen on the Sun, when we observe simultaneous emergence of new flux in various parts of an extended active region (Zirin, 1983). The distribution of the active areas on the surface of HK Lac during the past eight years, is
discussed.
A problem of start detector is very topical in laser radar station working with a train of pulses generating by mode locked Nd:YAG laser. This article deals with new developed start detector used in INTERCOSMOS laser radar station in Helwan, Egypt. A time resolution of the detector is better 150ps.
Increased excitability of the spinal motor system has been observed after loud and unexpe cted acoustic stimuli (AS) preceding H-reflexes. The paradigm has been proposed as an electrophysiological marker of reticulospinal tract activity in humans. The brainstem reticular formation also maintains dense anatomical interconnections wi th the cortical motor system. When a startling AS is delivered, prior to transcranial magnetic stimulation (TMS), the AS produces a suppression of motor evoked potential (MEP) amplitud e in hand and arm muscles of healthy subjects. Here we analyzed the conditioning effect of a startling AS on MEP amplitude evoked by TMS to the primary motor leg area. Ten healthy volunteers participated in two experiments that used a conditioning-test paradigm. In the first experiment, a startling AS preceded a suprathreshold transcranial test stimulus. The interstimulus interval (ISI) varied between 20 to 160 ms. When given alone, the test stimulus evoked a MEP amplitude of approximately 0.5 mV in the slightly preinervated soleus muscle (SOL). In the seco nd experiment, the startling AS was used to condition the size of the H-reflex in SOL muscle. Mean MEP amplitude was calc ulated for each ISI. The conditioning AS suppressed MEP amplitude at ISIs of 30-80 ms. By contrast, H-reflex amplitude was augmented at ISIs of 100- 200 ms. In conclusions, acoustic stimulation exerts opposite and ISI-specific effects on the amplitude of MEPs and H-reflex in the SOL muscle, indicating different mechanism of auditory-to-motor interactions at cortical and spinal level of motor system., T: V. Ilic ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy