Wettability of four Asian meranti species

Summary The wettability of four Asian meranti species (dark red, light red, white, and yellow) in various liquids was studied by a cone-immersion technique. Wettability was expressed in terms of the area under the force-immersion curve and referred to as the wettability index. Wettability was strongly influenced by the pH of the solution, generally increasing with increasing pH. Surfactant type affected wettability, with the cationic type yielding the greatest wettability followed by anionic and nonionic types. Among the liquids used, distilled water gave the lowest, and acetone-isopropyl alcohol solution gave the greatest wettability. Of the meranti species, yellow meranti showed the greatest wettability, followed by white, light red, and dark red meranti.A plot of the relative amount of liquid absorbed into the wood sample versus wettability index yielded two regions, one attributed mainly to liquid trapped in crevices on the wood surface, and another which may be more indicative of wood-liquid interactions. A highly significant linear correlation between wettability index and liquid surface tension was found for those species with low and medium wettability, while that with high wettability showed no correlation. A new empirical approach of determining the critical surface tension of wood is discussed. Limited data for the present method indicated close agreement with result from the literature obtained by the use of the well-known Zisman's contact angle approach.     

马铃薯晚疫病菌在水和土壤中的侵染力与形态变化的研究

 马铃薯晚疫病菌以薄壁圆孢子和厚垣孢子的形态存在于润湿的土壤中。保持侵染力的时间最长为75天。病种薯上的病原菌在pH 7.5、含水率17-22%的土壤中,保持侵染力的时间是90天。
病原菌在各种液体中都能形成厚垣孢子。
较低的温度和较好的营养条件能延长孢囊孢子的寿命和延缓厚垣孢子的形成期。     

Phosphorus in wine: comparison of atomic absorption spectrometry methods

Phosphorus in wine may be determined directly or indirectly by atomic absorption spectrometry. The direct method uses the carbon rod atomizer as the excitation source and a phosphorus hollow cathode lamp. In the indirect determination, one measures the amount of molybdenum that will complex with phosphorus in the wine. Both nitrous oxide-acetylene and air-acetylene flames are suitable as atomization sources in this indirect method. The resultant data have been compared with those from the AOAC colorimetric method (11.032-11.034). A 2-sample comparison test showed the results to be insignificantly different at the 95% confidence limits.     

大白菜窖藏中一些腐烂细菌的研究

 窖藏白菜腐烂是由许多细菌造成的。最重要的是Erwinia aroideae和E.phytophthora以及被认为是腐生菌的三种芽孢杆菌Bacillus pumilus,B.poly-myxa和B.subtilis。试验证明在一定条件下后者能引致明显的腐烂。     

Type II Supernova Matter in a Silicon Carbide Grain from the Murchison Meteorite

The circumstellar silicon carbide (SiC) grain X57 from the Murchison meteorite contains large amounts of radiogenic calcium-44 (20 times its solar system abundance) and has an anomalous silicon isotopic composition, different from other circumstellar SiC grains. Its inferred initial 44Ti/Si and 44Ti/48Ti ratios are 1.6 x 10(-4) and 0.37. In addition, it contains radiogenic magnesium-26; the inferred initial 26Al/27Al ratio is 0.11. The isotopic and elemental data of X57 can be explained by selective mixing of matter from different zones of a typical type II supernova of 25 solar masses during its explosion. The high 44Ti/Si ratio requires contributions from the innermost nickel zone of the supernova to the SiC condensation site, as similarly suggested by astronomical observations.     

Quantal release of transmitter is not associated with channel opening on the neuronal membrane

The traditional view that quantal release of neurotransmitter results from the fusion of transmitter-containing vesicles with the neuronal membrane has been recently challenged. Although various alternative mechanisms have been proposed, a common element among them is the release of cytoplasmic transmitter, which, in one view, could occur through large conductance channels on the presynaptic membrane. Six nerve-muscle cell pairs were examined with a whole-cell patch clamp for the presence of such channels that are associated with the production of miniature end-plate potentials. Examination of the neuronal membrane current during the occurrence of 822 miniature end-plate potentials produced no evidence of large channels. Thus it is unlikely that quantal release is mediated by such channels in the neuromuscular junction.     

Adaptive radiation from resource competition in digital organisms

Species richness often peaks at intermediate productivity and decreases as resources become more or less abundant. The mechanisms that produce this pattern are not completely known, but several previous studies have suggested environmental heterogeneity as a cause. In experiments with evolving digital organisms and populations of fixed size, maximum species richness emerges at intermediate productivity, even in a spatially homogeneous environment, owing to frequency-dependent selection to exploit an influx of mixed resources. A diverse pool of limiting resources is sufficient to cause adaptive radiation, which is manifest by the origin and maintenance of phenotypically and phylogenetically distinct groups of organisms.