Showing papers by "Academia Sinica published in 1969"

Note on the Multivariate and the Generalized Multivariate Beta Distributions

Abstract: In this paper some properties of the multivariate Beta distributions are discussed. Specifically it is shown that the density of the multivariate Beta I distribution can be decomposed as a product of independent ordinary Beta I densities and the Dirichlet densities, while the density of the multivariate Beta II distribution as a product of independent ordinary Beta II densities and the inverted Dirichlet densities. Some extentions of the results to the generalized multivariate Beta distributions are indicated.

Factors influencing the production and further metabolism of indole-3-acetic acid by pseudomonas savastanoi

Abstract: Certain factors which affect production and accumulation of indole-3- acetic acid (IAA) and activity of enzymes associated with its synthesis from L-tryptophan were investigated in Pseudomonas savastanoi. Addition of L- tryptophan to the culture medium enhances the accumulation of IAA by the bacterium. However, both tryptophan oxidative decarboxylase and indoleacetamide hydrolase, which are involved in the conversion of L-tryptophan to IAA, are produced by the bacterium without addition of L-tryptophan to the medium. In a medium containing L-tryptophan, yields of tryptophan oxidative decarboxylase per liter of culture suspension were increased as much as 2-fold.IAA and indole-3-acetamide (IAM) strongly inhibit tryptophan oxidative decarboxylase. IAA up to 6×10-3M did not inhibit indoleacetamide hydrolase. IAA also inhibits uptake of L-tryptophan by whole cells.IAA is converted to its lysine conjugate by the bacterium. During logarithmic phase of growth in a nutrient medium, the specific activities of tryptophan oxidative decarboxylase and indoleacetamide hydrolase were 2-fold greater than that for the system converting IAA to its lysine conjugate. During the stationary growth phase, specific activity of all three enzymes decreased but that for the first two enzymes did so more rapidly than the specific activity of the lysine conjugate synthetase. Accumulation of IAA in culture filtrates is controlled to a large extent by the relative activities of the systems synthesizing and utilizing IAA.

Disparity, decimation and the Cambrian "explosion": comparison of early Cambrian and Present faunal communities with emphasis on velvet worms (Onychophora)

Abstract: The controversy about a Cambrian " explosion" of morphological disparity (followed by decimation), eladogenesis and fossilization is of central importanee for the history of life. This p aper revisits the controversy (with emphasis in onychophorans, which inelude emblematic organisms such as Hallucigenia), presents new data about the Chengjiang (Cambrian of China) faunal community and compares it and Ihe Burgess Shale (Cambrian of Canada) with an ecologically similar bul modern tropical marine site where onychophorans are absent, and with a modern neo tropical terrestrial onychophoran community. B i ovolume was estimated from material collected in Costa Rica and morphometric measurements were made on enlarged images of fossils. CaJTlbrian tropical mudflats were characterized by the adaptive radiation of two contrasting groups: the vagile arthropods and the sessile poriferans. Arthropods were later replaced as the dominant benthic laxon by polychaetes. Vagility and the exoskeleton may explain the success of arthropods from the Cambrian to the modern marine and terrestrial communities, both in population and biovolume. Food ecological displacement was apparen t i n the B. Shale, but not in Chengjiang or the terrestrial community. When only hard parts were preserved, marine and terrestrial fossil deposits of tropical origin are even less representative than deposits produced by temperate taxa, Chengjiang being an exception. Nutrient limitations might explain why deposit feeding is less important in terrestrial onychophoran communities, where carnivory, scavenging and omnivory (associated with high motility and life over the substrate) became moreimportant. Fossil morphometry supports the interpretation of "lobopod animal s" as onychophorans, whose abundance in Chengjiang was equal lo their abundance in modern communities. The extinction of marine onychophorans may reflect domination of the infaunal habitat by polychaetes. We conclude tha! ( 1 ) a mature ecological community structure was generalized during the Cambrian, and even biodiversity and equitability indices were surprisingly elose lo modern values; (2) the morphological diversity and geographic distribution of onychophorans indicate a significant pre-Cambrian evolutionary history which does no! support the "explosion" hypothesis; (3) disparity among phyla was not as important as the explosion-decimation model predicIs, bu! in the case of onychophorans, disparity wIlhin the phylum was greater than it is today and its reduction may have been associated with migration into the sedi ment when large predators evolved.

Fluctuation analysis of the24Mg(d, α)22Na reaction

Abstract: The24Mg(d, α)22Na reaction has been studied in the deuteron energy range (1.83÷3.05) MeV. Excitation functions were measured in steps of 25 keV at five angles between 40° and 140°. The transitions to the lowest three states of22Na have been analysed in terms of the fluctuation theory of Ericson and of Brink and Stephen. Autocorrelation functions and probability distributions have been calculated and used to deduce values of the average fluctuation width (≈50 keV) and the average level spacingD 0 (≈2 keV) in the compound nucleus26Al in the (13÷15) MeV excitation-energy interval. The direct effect was estimated and discussed. After subtracting the direct contribution, the total cross-section of the resulting compound contribution agrees with a statisticaltheory calculation.