The spatial and diurnal variation of rainfall over Asia was investigated using the spaceborne radar data for four seasons during 1998–2003. The regional variation of the prevailing precipitation systems most closely associated with the maximum hourly rainfall was shown by examining the fine spatial distribution of rainfall amount and scale‐based precipitation systems. Small precipitation systems (<102 km2) occurred most frequently around early afternoon over most land. The south facing slopes of the Himalayas, especially south of Mount Everest and the upper portion of the Brahmaputra valley, is the most obvious region of the daytime genesis of the convective systems over the Asian landmass. Over the Tibetan Plateau the occurrence of the small systems was larger than over inland India and the foothills. Large systems (>104 km2) developed mostly in the evening over nearly flat landmasses. Wide‐spread systems with intense rain pixels developed over the foothills of the Himalayas in late night–early morning period, which was distinct from the daytime convection. Over ocean, in addition to the morning signature, spatially inhomogeneous and systematic characteristics were evident over the offshore region, for example, around the maritime continent. Large systems, which are strongly associated with terrain, have a great influence on the total number of rain pixels and the total amount of rainfall. For 86% of the region where large system is dominant the time of maximum rainfall is within 3 hours of the time of maximum rainfall for large systems.

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Accumulations of β‐amyloid protein are characteristic and diagnostic features of the brain of Alzheimer's disease patients; however, the physiological role of this protein in CNS is unknown. We have previously reported that continuous infusion of β‐amyloid protein into rat cerebral ventricle impairs learning ability and decreases choline acetyltransferase activity, a marker enzyme of cholinergic neuron. In this study, the effects of β‐amyloid protein infusion on the release of neurotransmitters in cholinergic and dopaminergic neuronal systems were investigated by using an in vivo brain microdialysis method. Nicotine‐stimulated release of acetylcholine and dopamine in these animals was significantly lower than that in vehicle‐infused rats. Further, dopamine release induced by high‐K stimulation was decreased in β‐amyloid protein‐infused rats compared with vehicle‐infused rats. These results suggest that the release of the two transmitters, acetylcholine and dopamine, was decreased by β‐amyloid protein and that learning deficits observed in the β‐amyloid protein‐infused rats are partly due to the impairment of neurotransmitter release. Furthermore, continuous infusion of β‐amyloid protein may be a useful method to produce the animal model of Alzheimer's disease.

The adequacy of hourly rainfall sampling was examined in terms of the detection of diurnal variations using 8 yr (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) of data observed by the precipitation radar on the Tropical Rainfall Measuring Mission (TRMM) satellite. It was found that the monthly and hourly rain samples for each 0.2°grid point over the 8-yr period are composed of multiple precipitation systems. In this study, a "3-h-significant diurnal peak" was defined as the time of maximum rainfall with consecutive positive anomalies for more than 3 h. The fraction of the analyzed area with a 3-h-significant diurnal peak increased annually and accounted for 43% of the total global tropics at 0.2°resolution over the 8-yr period. The diurnal signature over Tibet and the Amazon showed a high degree of spatial uniformity (at Ͼ10°scale). The degree of similarity and locations of the regional diurnal characteristics are described in terms of seasonal variations and at multiple resolutions based on spatial uniformity. For example, uniform early-afternoon peaks generally appear over the coastal land and areas of high relief, whereas a seasonally invariant early-afternoon peak over the low-lying Amazon basin is recognized as a regional characteristic. In areas of coastal ocean, early-morning peaks appear in certain regions such as the area surrounding the so-called Maritime Continent and the area off the west coast of Mexico. These peaks are distinct from the global characteristics of late-morning rainfall maxima recorded over most coastal oceans and early-morning peaks recorded over open ocean. The results are also compared with those derived from TRMM Microwave Imager (TMI) data. In addition to obtaining a coherent signal, regional differences in the timing of maximum rainfall over the Tibetan Plateau were addressed; this discrepancy is attributed to limitations of the scattering algorithm used for TMI data in terms of detecting shallow convection and screening cold surfaces.