Showing papers by "Academia Sinica published in 1989"

Dose-response relation between arsenic concentration in well water and mortality from cancers and vascular diseases

Abstract: Age-adjusted mortality rates were analyzed to examine the dose-response relation between ingested arsenic levels and risk of cancers and vascular diseases among residents in the endemic area of blackfoot disease, a unique peripheral vascular disease associated with long-term exposure to high-arsenic artesian well water and confined to the southwestern coast of Taiwan. The arsenic levels in well water determined in 1964-1966 were available in 42 villages of the study area, while mortality and population data during 1973-1986 were obtained from the local household registration offices and Taiwan Provincial Department of Health. Age-adjusted mortality rates from various cancers and vascular diseases by sex were calculated using the 1976 world population as the standard population. A significant dose-response relation was observed between arsenic levels in well water and cancers of the bladder, kidney, skin, and lung in both males and females, and cancers of the prostate and liver in males. However, there was no association for cancers of the nasopharynx, esophagus, stomach, colon, and uterine cervix, and for leukemia. Arsenic levels in well water were also associated with peripheral vascular diseases and cardiovascular diseases in a dose-response pattern, but not with cerebrovascular accidents. The dual effect of arsenic on carcinogenesis and arteriosclerosismore » and the interrelation between these two pathogenic mechanisms deserve more intensive study.« less

The influence of ENSO on the summer climate change in China and its mechanism

Abstract: The influence of ENSO on the summer climate change in China and its mechanism from the observed data is discussed. It is discovered that in the developing stage of ENSO, the SST in the western tropical Pacific is colder in summer, the convective activities may be weak around the South China Sea and the Philippines. As a consequence, the subtropical high shifted southward. Therefore, a drought may be caused in the Indo-China peninsula and in the South China. Moreover, in midsummer the subtropical high is weak over the Yangtze River valley and Huaihe River valley, and the flood may be caused in the area from the Yangtze River valley to Huaihe River valley. On the contrary, in the decaying stage of ENSO, the convective activities may be strong around the Philippines, and the subtropical high shifted northward, a drought may be caused in the Yangtze River valley and Huaihe River valley.

Prevalence of psychiatric disorders in Taiwan defined by the Chinese Diagnostic Interview Schedule.

Abstract: The Taiwan Psychiatric Epidemiological Project, conducted from 1982 to 1986, used the multistage random sampling method with 5005, 3004 and 2995 subjects selected respectively from metropolitan Taipei (MT), 2 small towns (ST) and 6 rural villages (RV). The case identification tool was the Chinese modified Diagnostic Interview Schedule (DIS-CM). This study presents the lifetime and one-year prevalence of 27 and of 17 specific psychiatric disorders respectively. The lifetime prevalence of any disorder defined by the DIS-CM—excluding tobacco dependence—was 16.3%, 28.0% and 21.5% in the MT, ST and RV samples respectively. The differences in lifetime prevalence between the sexes and between the 3 sampling areas were significant for 15 and 8 disorders respectively. The ST sample seemed to have the most disorders, with the highest prevalence among 3 sampling areas. The mean ratio of one-year to lifetime prevalence was 0.67. The differences in prevalence rates between the 3 sampling areas and between the international studies are discussed from methodological, social and cultural points of view.

Holocene--late pleistocene climatic ice core records from qinghai-tibetan plateau.

Abstract: Three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau of China provide a detailed record of Holocene and Wisconsin-Wurm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative δ 18 O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly ∼10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago.

Scavenging effect of extracts of green tea and natural antioxidants on active oxygen radicals

Abstract: With the use of the spin trapping methods, the scavenging effects of the extracts of green tea and other natural foods are studied. In stimulated polymorphonuclear leukocytes (PMN) system, water extract fraction 6 (F6) from green tea and green tea polyphenols (GTP) have the strongest scavenging effect on the active oxygen radicals, much stronger than vitamin C (Vc) and vitamin E (VE). Rosemary antioxidants (RA) and Curcumin (Cur) have weaker scavenging effects than Vc, but stronger than VE. In Fenton Reaction, Cur has the strongest scavenging effect (69%) on hydroxyl radicals. In irradiation, riboflavin system F6(74%) and GTP(72%) have very strong scavenging effects that are weaker than Vc, but much stronger than VE (23%). With the use of spin probe oxymetry, the oxygen consumption in respiratory burst of stimulated PMN were measured when the antioxidants existed in these systems. The results demonstrated that these antioxidants did not affect the respiratory burst of human polymorphonuclear leukocytes stimulated with PMA.

Human hepatitis delta virus RNA subfragments contain an autocleavage activity.

Abstract: Hepatitis delta virus (HDV) contains a single-stranded circular RNA genome of 1.7 kilobases. In this report we demonstrate that subfragments of HDV RNA can undergo autocatalytic cleavage. This cleavage requires at least 500 microM of Mg2+ or Ca2+, is not affected by varying the pH from 5.0 to 9.1, and occurs with RNA fragments as small as 133 nucleotides. The larger RNA fragments containing additional HDV sequences have a lower efficiency of cleavage. Deletion analysis at both ends of RNA subfragments suggested that the catalytic ability of HDV RNA resides in a stretch of no more than 117 nucleotides around the cleavage site. The cleavage occurs at the phosphodiester bond between nucleotides 688 and 689 on the HDV genomic map, generating a 5' fragment with a terminal uridyl 2',3'-cyclic monophosphate residue and a 3' fragment with a guanosyl residue with a 5'-hydroxyl group. The smallest autocleaving RNA does not contain the "hammerhead" sequence required for the autocleavage of other known self-cleaving RNA. The cleavage of HDV RNA occurs at a much faster rate, even at a very low Mg2+ concentration, than that of other "ribozymes." Thus, HDV RNA represents a distinct class of ribozyme.

Specific detection of circulating surface/secreted glycoproteins of viable cysticerci in Taenia saginata cysticercosis

Abstract: A mouse monoclonal antibody (MoAb), reactive with a repetitive carbohydrate epitope on lentil-lectin adherent glycoproteins present on the surface and in the secretions of Taenia saginata cysticerci, was used in the construction of a diagnostic ELISA assay to detect these glycoproteins in the serum of T. saginata infected cattle. The MoAb was used as the trapping layer and subsequently bound glycoprotein was revealed using the same MoAb and biotinylated peroxidase-streptavidin complex as the developing system. The assay was suitably specific. Exceptionally low background values were obtained with sera from animals with a range of commonly occurring tropical parasitic infections, including Taenia hydatigena, Echinococcus granulosus and Fasciola gigantica. The minimal detection level was approximately 200 live cysticerci in cattle. Parasite derived glycoprotein could be detected in serum from about 4-5 weeks post-infection onwards and was associated with a current infection, as drug treatment of infected cattle to kill the cysticerci resulted in the disappearance of these components from the circulation, while the titre of anti-parasite antibody remained high. The same assay also detected Taenia solium cysticercosis in humans.

Convergence of the fractional step Lax-Friedrichs scheme and Godunov scheme for the isentropic system of gas dynamics

Abstract: A convergence theorem of the fractional step Lax-Friedrichs scheme and Godunov scheme for an inhomogeneous system of isentropic gas dynamics (1<γ≦5/3) is established by using the framework of compensated compactness. Meanwhile, a corresponding existence theorem of global solutions with large data containing the vacuum is obtained.

Photosensitized reduction of benzil by heteroatom-containing anthracene dyes

Abstract: Benzil in methanol was quantitatively reduced to benzoin by triethylamine in the presence of some heteroatom-containing anthracene dyes under visible irradiation. The thermodynamics, kinetics, and various quantum yields were investigated. The transient intermediate of the reaction was detected by flash photolysis. The relationship between the photosensitized reduction and the fading of the dyes was studied. The requirements for the dyes and the mechanism of these reactions were clarified.

Changes of plasma osmolality, chloride concentration and gill Na−K-ATPase activity in tilapia Oreochromis mossambicus during seawater acclimation

Abstract: Changes of plasma osmolality, chloride concentration and gill Na−K-ATPase activity in tilapia Oreochromis mossambicus (obtained from Tainan Fish Culture Station of Taiwan Fisheries Research Institute, 1987) during seawater acclimation were examined. Three experiments were performed. (1) Freshwater (FW) to 30‰ salinity seawater (SW): plasma osmolality and chloride rose violently immediately post-transfer. At 6 h, gill Na−K-ATPase activity began to increase but most fish died from excessive plasma osmolality and Cl. (2) FW to 20‰ salinity SW: plasma osmolality and chloride increased immediately post-transfer, but more slowly than in (1), and began to decrease at 24 h. However it was not until 12 h post-transfer that gill Na−K-ATPase activity rose slowly. (3) FW to 20‰ salinity SW for 24 h, then to 30‰ salinity SW: after transfer to 30‰ salinity, plasma osmolality and chloride showed only a small increase initially then declined, while gill Na−K-ATPase activity started to rise rapidly within 3 h. The present results coincided with our previous morphological data concerning the ultrastructural responses of gill chloride cells. These are discussed to elucidate the osmoregulation mechanisms in tilapia during seawater acclimation.

A suggested fractionation scheme of inorganic phosphorus in calcareous soils

Abstract: On the basis of a critical review on conventional fractionation schemes of inorganic phosphate and further study of chemical behaviors of Ca-P and Fe-P in calcareous soils, a systematic scheme for the separation of soil inorganic phosphates in calcareous soils is suggested. In the scheme calcium phosphate is classified into dicalcium phosphate, octacalcium phosphate and apatite types, and Ca2-P is extracted by NaHCO3 solution, Ca8-P by NH4Ac, Al-P by NH4F, Fe-P by NaOH-Na2CO3, occluded-P by Na3Cit-Na2S2O4-NaOH, and Ca10-P by H2SO4. Synthetic phosphates prepared of which the chemical and physical assay show good consonance with the theoretical value were used in experiment, the recovery rates of the phosphates added into the calcareous soils by specific extractants is at the range of 85–99%.

The effect of SiO2 particles upon stabilization of foam

Abstract: Factors influencing the bubble stabilization by spherical monodisperse SiO2 particles with diameters ranging from 20 to 700 nm have been examined. Results showed that hydrophobic silica particles had good stabilization for foam produced by sodium dodecyl sulfonate in alkaline aqueous medium. The smaller the particle size, the stronger the stabilization. The possible mechanism of the stabilization effect has been discussed.

Analyses of the mechanical properties and microstructure of bamboo-epoxy composites

Abstract: Bamboo reinforced epoxy possesses reasonably good properties to waarrant its use as a structural material, and is fabricated by utilizing bamboo, an abundant material resource, in the technology of fibre composites. Literature on bamboo-plastics composites is rare. This work is an experimental study of unidirectional bamboo-epoxy laminates of varying laminae number, in which tensile, compressive, flexural and interlaminar shear properties are evaluated. Further, the disposition of bamboo fibre, the parenchymatous tissue, and the resin matrix under different loading conditions are examined. Our results show that the specific strength and specific modulus of bamboo-epoxy laminates are adequate, the former being 3 to 4 times that of mild steel. Its mechanical properties are generally comparable to those of ordinary glass-fibre composites. The fracture behaviour of bamboo-epoxy under different loading conditions were observed using both acoustic emission techniques and scanning electron microscopy. The fracture mode varied with load, the fracture mechanism being similar to glass and carbon reinforced composites. Microstructural analyses revealed that natural bamboo is eligibly a fibre composite in itself; its inclusion in a plastic matrix will help solve the problems of cracking due to desiccation and bioerosion caused by insect pests. Furthermore, the thickness and shape of the composite can be tailored during fabrication to meet specific requirements, thereby enabling a wide spectrum of applications.

Oxygen diffusion in the superconducting oxide YBa2Cu3O7-x.

Abstract: A low-frequency internal friction peak was observed at 200 \ifmmode^\circ\else\textdegree\fi{}C for sintered ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ bar specimens annealed at different temperatures between 400 and 650 \ifmmode^\circ\else\textdegree\fi{}C. This peak is interpreted in terms of diffusional jumps of oxygen atoms in the basal planes between sublattice sites ${\mathrm{O}}_{\mathrm{A}}$((1/2, 0,0) and ${\mathrm{O}}_{\mathrm{B}}$(0,(1/2,0). These two sites are not crystallographically equivalent in orthorhombic symmetry. Oxygen diffusivity for planar diffusion in the basal planes was derived on the basis of a one-dimensional random-walk process, which yields: D=((1/4)${d}^{2}$${C}_{B}$/(${C}_{A}$+${C}_{B}$)\ensuremath{ u} ${\ensuremath{ u}}_{0}$ exp(-${H}_{B}$/kT) =${D}_{0}$exp(-${H}_{B}$/kT), where ${H}_{B}$=${H}_{A}$+\ensuremath{\Delta}E. The parameters ${C}_{A}$, ${C}_{B}$, ${\ensuremath{ u}}_{0}$, and ${H}_{A}$ are evaluated from internal friction data for the specimens of known oxygen deficiency x and \ensuremath{\Delta}E, the poten- tial energy difference between sites ${\mathrm{O}}_{\mathrm{A}}$ and ${\mathrm{O}}_{\mathrm{B}}$, from Boltzmann's distribution law ${C}_{A}$/${C}_{B}$=exp(-\ensuremath{\Delta}E/kT). The preexponential factor ${D}_{0}$=3.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ ${\mathrm{cm}}^{2}$/sec and the activation energy of the 200 \ifmmode^\circ\else\textdegree\fi{}C internal-friction peak ${H}_{A}$=1.03 eV are both temperature insensitive. By contrast, \ensuremath{\Delta}E is temperature dependent; it is 0.23 eV at 400 \ifmmode^\circ\else\textdegree\fi{}C and decreases as the temperature is raised, vanishing at 670 \ifmmode^\circ\else\textdegree\fi{}C, the temperature of the orthorhombic-to-tetragonal transition temperature at which ${\mathrm{O}}_{\mathrm{A}}$ and ${\mathrm{O}}_{\mathrm{B}}$ sites become indistinguishable. Non-Arrhenius behavior exists between the oxygen diffusivity and the diffusion temperature in this type of diffusion mechanism.

Elevation of glutathione levels and glutathione S-transferase activity in arsenic-resistant Chinese hamster ovary cells.

Abstract: Arsenic-resistant Chinese hamster ovary (CHO) cells were established by progressively increasing the concentration of sodium arsenite in culture medium. One of the resistant clones, SA7, was also cross-resistant to As(V), Zn, Fe(II), Co, and Hg. The susceptibilities to sodium arsenite in parental CHO cells, revertant SA7N cells, and resistant SA7 cells were correlated with their intracellular glutathione (GSH) levels and glutathione S-transferase (GST) activity. The resistance in SA7 cells was diminished by depletion of GSH in cells after treatment with buthionine sulfoximine. Furthermore, after reexposure of revertant SA7N cells to sodium arsenite, the intracellular GSH levels, GST activity, and resistance to sodium arsenite were raised to the same levels as SA7 cells. These data indicate that the elevation of intracellular GSH levels and GST activity in SA7 cells may be responsible for the resistance to arsenite. A p25 protein, which could be a monomer subunit of GST, accumulated in SA7 cells. In addition, an outward transport inhibitor, verapamil, indiscriminately increased the arsenite toxicity in resistant and parental cells.

Electron thermal confinement studies with applied resonant fields on TEXT

Abstract: Externally applied magnetic fields are used on the Texas Experimental Tokamak (TEXT) to study the possibility of controlling the particle, impurity and heat fluxes at the plasma edge. Fields with toroidal mode number n = 2 or 3 and multiple poloidal mode numbers m (dominantly m = 7) are used, with a poloidally and toroidally averaged ratio of radial to toroidal field components 〈|br/Bo〉 ≅0. 1%. Calculations show that it is possible to produce mixed islands and stochastic regions at the plasma edge (r/a ≥ 0.8) without affecting the interior. The expected magnetic field structure is described and experimental evidence of the existence of this structure is presented. The edge electron temperature decreases with increasing 〈|br/Bo〉, while interior values are not significantly affected. The implied increase in edge electron thermal diffusivity is compared with theoretical expectations and is shown to agree with applicable theories to within a factor of three.

How honeybees measure their distance from objects of unknown size

Abstract: 1. To investigate whether bees use motion cues in the task of estimating distance, they were trained to collect a food reward on one of several ‘flowers’ of different sizes on an artificial meadow (Figs. 1, 4a, 6a). In each experiment, the height of the rewarded flower was kept constant during training. The bees were prevented from learning the sizes and positions of the flowers by varying these parameters continually during training as well as during the subsequent discrimination tests. Thus, the only reliable cue that could be used to recognize the rewarded flower was the speed at which its image moved across the retina as the bees flew over the meadow: The contours of a high flower would move faster than those of a lower one, irrespective of size. 2. Bees that are rewarded on a flower placed at a particular height discriminate it from flowers at other heights (Fig. 2a, b). This is independent of whether the bees have been trained to the highest flower (Fig. 4b), the lowest flower (Fig. 5b), or one at an intermediate height (Fig. 6b). In each case, they are able to select the correct flower according to the particular speed at which its image moves across the eye during the searching flight. 3. Under our experimental conditions, bees can discriminate height differences of 2 cm (Figs. 4c, 5c). 4. Introduction of a textured background enhances the accuracy of height discrimination (Fig. 2d). 5. Discrimination of flower height breaks down in the absence of green contrast (Fig. 2c), showing that the bees' performance in this task is mediated by signals from the green-sensitive receptors and is consequently colour-blind, as are all of the motion-induced behaviours so far examined in the bee. 6. We conclude that bees can estimate an object's distance by using its apparent motion across the retina when the background is featureless, and possibly, in addition, its motion relative to the background when the background is textured. When encountering a novel environment comprising unfamiliar objects of unknown size, the bees can evidently use these two types of motion cues to acquire a three-dimensional percept of the visual world.

Transmission electron microscope observations of dislocations and stacking faults in a decagonal Al-Cu-Co alloy

Abstract: Dislocations and stacking faults have been observed for the first time in a decagonal quasicrystalline structure. The lattice defects found in the decagonal phase of A165Cu20Co15 give an electron diffraction contrast similar to that found in normal-crystalline materials.

Origin of ancient potash evaporites: clues from the modem nonmarine qaidam basin of Western china.

Abstract: Modern potash salt deposits and associated brines of the Qaidam Basin, western China, demonstrate that some anomalous marine evaporites may have formed from nonmarine brines instead of seawater. Qaidam Basin brines are derived from meteoric river inflow mixed with small amounts of CaCl spring inflow similar in composition to many saline formation waters and hydrothermal brines. Evaporation of springenriched inflow yields a predicted mineral sequence including carnallite, bischofite, and tachyhydrite that is identical to several anomalous marine evaporites. Other mixtures of river and spring inflow produce the salt assemblage expected from evaporation of seawater.