Showing papers by "Academia Sinica published in 1987"

Second harmonic generation and accurate index of refraction measurements in flux-grown KTiOPO 4

Abstract: Accurate index of refraction measurements have been performed in flux-grown KTiOPO(4). These measurements give good agreement between experiment and theory for angle phase matching in Type II second harmonic generation at 1.064 microm. These refractive-index data have allowed us to calculate the propagation angles for second harmonic generation at wavelengths of interest other than 1.064 microm such as 1.34 microm. Type II second harmonic energy conversion efficiency of 1.064 micro m of up to 59% in this material has also been demonstrated with higher efficiencies possible. Limits to conversion efficiency are discussed.

Diffusion for global optimization in R n

Abstract: We seek a global minimum of $U:\mathbb{R}^n \to \mathbb{R}$. The solution to $( * )({d / {dt}})X(t) = - abla U(X(t))$ will find local minima. Using the idea of simulated annealing, we consider th...

Acid rain: china, United States, and a remote area.

Abstract: The composition of precipitation in China is highly influenced by fossil fuel combustion and agricultural and cultural practices. Compared to the eastern United States, precipitation in China generally has higher concentrations of sulfate, ammonium, and calcium. Wet deposition rates of sulfur in China are 7 to 130 times higher than those in a remote area in the Southern Hemisphere. In many areas of the world, significant ecological changes have occurred in ecosystems that have acid deposition rates substantially less than those currently existing in China.

Isoparametric functions on Riemannian manifolds. I

Abstract: On etablit les proprietes de base des fonctions transnormales et on demontre le lemme du tube. On demontre que: soit M une variete de Riemann lisse, complete, connexe et f une fonction transnormale sur M. Alors: a) les varietes focales de f sont des sous-varietes lisses de M; b) chaque ensemble de niveau regulier de f est un tube sur d'autres des varietes focales

Geomorphic evidence for active faulting in the Altyn Tagh and northern Tibet and qualitative estimates of its contribution to the convergence of India and Eurasia

Abstract: A brief traverse across the Altyn Tagh and Kunlun in northern Tibet revealed abundant evidence for recent crustal deformation there. From ridges offset roughly 10 m and from fresh mole tracks 40 cm or more high along the Altyn Tagh strike-slip fault, we conclude that a large earthquake occurred in the past few hundred years. Accordingly, the rate of slip could be relatively high (30 ±20 mm/yr?). Active reverse (or thrust) faults mark the bases of several mountain ranges in the Altyn Tagh and Kunlun where the neighboring basins lie at elevations less than 4000 m. Therefore, roughly north-south crustal shortening appears to be occurring there, probably at a rate of several millimetres per year. The crustal shortening accommodated by strike-slip and reverse (or thrust) faulting appears to account for a significant part (10%–25%) of India's convergence with Eurasia. The broad zone of crustal shortening in northern Tibet indicates that the areal extent of the plateau is increasing northward by crustal thickening on its northern margin.

The symplectic methods for the computation of hamiltonian equations

Abstract: The present paper gives a brief survey of results from a systematic study, undertaken by the authors and their colleagues, on the symplectic approach to the numerical computation of Hamiltonian dynamical systems in finite and infinite dimensions. Both theoretical and practical aspects of the symplectic methods are considered. Almost all the real conservative physical processes can be cast in suitable Hamiltonian formulation in phase spaces with symplectic structure, which has the advantages to make the intrinsic properties and symmetries of the underlying processes more explicit than in other mathematically equivalent formulations, so we choose the Hamiltonian formalism as the basis, together with the mathematical and physical motivations of our symplectic approach for the purpose of numerical simulation of dynamical evolutions. We give some symplectic difference schemes and related general concepts for linear and nonlinear canonical systems in finite dimensions. The analysis confirms the expectation for them to behave more satisfactorily, especially in the desirable conservation properties, than the conventional schemes. We outline a general and constructive theory of generating functions and a general method of construction of symplectic difference schemes based on all possible generating functions. This is crucial for the developments of the symplectic methods. A generalization of the above theory and method to the canonical Hamiltonian eqs. in infinite dimensions is also given. The multi-level schemes, including the leapfrog one, are studied from the symplectic point of view. We given an application of symplectic schemes, with some indications of their potential usefulness, to the computation of chaos.

Electrochemically prepared polypyrroles from aqueous solutions

Abstract: Polypyrrole (PPy) films generated electrochemically from aqueous solutions have been found to have also good electrical conductivity PPy films with the counter anions TsO−, SO4=, and NO3− showed compact structure with apparent densities close to their flotation densities The oxidative stability of PPy films has been compared by the value of the oxidation peak Epa around 10 V (vs SCE) in the cyclovoltammogram Prolonged electrolysis at +08 V led to oxidative degradation The temperature dependence of the conductivity followed the variable range hopping equation However voltage shorted compaction (VSC) conductivity measurements might show pronounced differences at low temperatures for some of these films No significant frequency dependence of the conductivity was found up to 35 GHz In the IR spectra of electrochemically reduced PPy film by transmission the v (N-H) and sp2 v (C-H) absorption bands were observed with no sp3 v (C-H) bands On grinding the reduced film with KBr to make powder compact the sp3 v (C-H) absorption bands appeared indicating a mobile proton on the N-atom of the pyrrole ring Definite evidence from IR spectra for the de-intercalation of the counter anion of the conducting PPy film during electrochemical reduction and chemical compensation has been obtained The intercalation and de-intercalation of the counter anions was found to be accompanied by profound morphological changes Molecular composites from in situ polymerization of aqueous pyrrole solution in a flexible polymer are briefly discussed

Geologic evolution of northern tibet: results of an expedition to ulugh muztagh.

Abstract: A reconnaissance expedition across the northern margin of the Tibetan plateau revealed evidence of a late Cenozoic northward progression of the locus of crustal shortening and, therefore, of a northward growth of the area encompassed by the plateau. Active reverse faults crop out at the foot of the Altyn Tagh, on the northern edge of the plateau, and at the bases of several ranges within the Altyn Tagh and Kunlun, where the elevations of the neighboring basins are less than 4000 meters. Farther south, where elevations are higher, there was no evidence of recent faulting, but late Cenozoic rock in the Ayak Kum Kol basin has been strongly folded. South of this basin, Ulugh Muztagh, apparently the highest mountain in the eastern Kunlun, is underlain by late Miocene, tourmaline-bearing and two-mica granite. These rocks suggest that thickening of continental crust had begun in this area by late Miocene time. Overlying quartz-sanidine welded tuffs of Pliocene age imply that uplift and erosion occurred between Miocene and Pliocene time, but with little subsequent erosion. In addition, we found an east-west trending belt of mafic and ultramafic rock that probably marks a suture of a crustal fragment with southern Asia in Triassic or more recent time.

Leaf carbon isotope ratios of plants from a subtropical monsoon forest.

Abstract: Carbon isotope ratios were used to survey the distribution of photosynthetic pathways among taxa, the relationship between photosynthetic pathway and habitat light levels, and the relationship between intercellular CO2 levels of C3 plants and habitat light levels within a subtropical monsoon forest in southern China. Of 128 species, most (94) possessed the C3 photosynthetic pathway; 33 species possessed the C4 pathway and all of these were restricted to high light locations. There was one epiphytic CAM species. The C3 species were classified as occurring in open, intermediate, and closed canopy sites. Among C3 species, carbon isotope ratios tended to become more negative with decreasing light availability in the habitat.

β-phase formation of poly(vinylidene fluoride) from the melt induced by quenching

Abstract: Influence de la trempe et du recuit etudiee par FTIR, diffractometrie RX et microscopie electronique

Tolerance and ultrastructural responses of branchial chloride cells to salinity changes in the euryhaline teleost Oreochromis mossambicus

Abstract: The changes of intercellular organization and junctional structures in branchial chloride cells reflect respective functions in different salinities. Under TEM, leaky junctions and intercellular digitations occurred between branchial chloride cells of Oreochromis mossambicus Peters adapted to seawater, but not in those adapted to freshwater. The fish transferred directly to 30‰ S seawater from freshwater died within 6 h, and their chloride cells developed neither leaky junctions nor interdigitations. The fishes acclimated to 20‰ S seawater for 12 h did not develop the characteristics of seawater-adapted chloride cells and died after transfer to 30‰ S seawater. The fish acclimated to 20‰ S seawater for 24 h started to develop seawater-adapted chloride cells, and were able to survive when transferred to 30‰ S seawater. Thus, the development of leaky junctions and interdigitations in branchial chloride cells appears to correlate to seawater adaptation in O. mossambicus. These changes of seawater-adapted chloride cells seem to be associated with the increase of ion permeability in the gill of teleosts adapted to seawater rather than those adapted to freshwater.

Pesticide clastogenicity in Chinese hamster ovary cells

Abstract: Paraquat, alachlor, butachlor, phorate and monocrotophos, several of the most extensively used pesticides in Taiwan, were investigated for their clastogenicity using chromosome aberration (CAb) induction in Chinese hamster ovary (CHO) cells. Significance levels of the binomial trend analysis and binomial mutagenicity data test were two criteria for the summary judgement of the pesticide clastogenicity. Except for phorate, all pesticides tested were clastogenic to CHO cells in the absence of in vitro metabolic activation by S9. 5 μl/ml rat-liver extract, S9, were used as the source of in vitro metabolic activation. 3 different outcomes were found after the addition of S9. (1) Paraquat: significant decrease in induced CAbs. (2) Monocrotophos: concomitant occurrence of decreased cytotoxicity and increased clastogenicity. (3) Alachlor, butachlor and phorate: increased cytotoxicities with no sign of enhancement in clastogenicity.

Scalar Curvatures on Sn.

Abstract: Soit (M n ,g) une variete de Riemann compacte de dimension n≥3, et R(x) une fonction lisse sur M n . On etudie si R(x) peut etre la courbure scalaire d'une metrique g~ qui est conforme point par point a la metrique originale g

Somatic embryogenesis and plant regeneration in Carica papaya L. tissue culture derived from root explants.

Abstract: The regeneration potential of shoot tip, stem, leaf, cotyledon and root explants of two papaya cultivars (Carica papaya cv. 'Solo' and cv. 'Sunrise') were studed. Callus induction of these two cultivars of papaya showed that the shoot tips and stems are most suitable for forming callus, while leaves, cotyledons and roots are comparatively difficult to induce callus. Callus induction also varied with the varities. Somatic embryogenesis was obtained from 3-month-old root cultures. A medium containing half strength of MS inorganic salts, 160 mg/l adenine sulfate, 1.0 mg/1 NAA, 0.5 mg/1 kinetin and 1.0 mg/1 GA3 was optimal for embryogenesis. The callus maintained high regenerative capacity after two years of culture on this medium. Plants derived from somatic embryos were obtained under green-house conditions.

Raw materials for making porcelain and the characteristics of porcelain wares in north and south china in ancient times

Abstract: This is a review of the raw materials used for producing ancient traditional porcelains in the famous kiln areas of north and south China. The relation between the use of porcelain stone and the invention of Chinese porcelain is described. The characteristics of porcelain stone and kaolin and their important role in the development of southern porcelains are discussed. As porcelain stone, which mainly consists of quartz and sericite, occurs widely in south China, the ancient southern porcelains were of a highly siliceous nature. From the beginning of the Yuan through to the Qing Dynasty more and more kaolin was added to the bodies to improve the quality of Jingdezhen porcelain. The glazes in south China were prepared from a mixture of porcelain stone and grass-plus-wood ash or glaze ash, here defined as the ash made by calcining limestone with plant material. The raw materials used in the north for making porcelain bodies were mainly various kinds of clay minerals. Feldspar, quartz and dolomite or calcite were used for northern porcelain glazes.