Showing papers by "Sun Yat-sen University published in 1990"
TL;DR: Fractional derivative spectra (FDS) are developed for analyzing the dimensionality of solids from the measured interband optical spectra in van Hove singularity regions and the fractional dimension determined is related to the anisotropic electron-lattice interactions and quantitatively describes the degree of anisotropy.
Abstract: The model of fractional-dimensional space is used to study optical properties associated with electron interband transitions near van Hove critical points in anisotropic systems. Bloch electrons in an anisotropic solid are treated as an isotropic fractional-dimensional free gas, where the dimension is determined by the degree of anisotropy. Density of states and optical spectra are obtained as a function of spatial dimension. Fractional derivative spectra (FDS) are developed for analyzing the dimensionality of solids from the measured interband optical spectra in van Hove singularity regions. Using fractional differentiation, the dimension, as well as critical-point parameters, of a solid is straightforwardly determined from the derivative order that yields a symmetric line shape, Lorentzian or its derivative, in FDS. The fractional dimension determined by FDS is related to the anisotropic electron-lattice interactions and quantitatively describes the degree of anisotropy.
83 citations
TL;DR: In this article, a model of fraction-dimensional space is proposed for dealing with anisotropic interactions, where the density of states calculated with the fraction dimension model are in good accordance with those obtained using previous methods.
75 citations
TL;DR: The demographic impact of economic development that has occurred in the Pearl River Delta Region of China a region strongly influenced by Hong Kong and Macau is analyzed in this paper, where more liberal policies with regard to migration have evolved in association with this economic development resulting in a marked increase in rural-urban migration.
Abstract: The demographic impact of the economic development that has occurred in the Pearl River Delta Region of China a region strongly influenced by Hong Kong and Macau is analyzed. The authors note that more liberal policies with regard to migration have evolved in association with this economic development resulting in a marked increase in rural-urban migration. "However in contrast to the usual pattern found in most third world countries accelerated urbanization in the Pearl River Delta Region in recent years has not been associated with increasing primacy. Nor has overurbanization--in the sense that massive rural to urban migration is not accompanied by rapid industrialization--been apparent. Instead there is a discernable trend toward a rank-size urban hierarchy. Also industrial development in the small and intermediate urban places has been gathering pace. In many respects the Chinese experience is an anomaly and does not readily fit the conventional models of regional development." (SUMMARY IN FRE) (EXCERPT)
69 citations
TL;DR: In this article, it was shown that under suitable conditions on f and h, the inhomogeneous problem has at least two positive solutions under the concentration-compactness method and the mountain pass theorem.
Abstract: By using the concentration-compactness method of Lions [14, 16] and the mountain pass theorem of Ambrosetti and Rabinowitz [3], through a careful inspection of the energy balance for some sequence of approximated solutions, we show that under suitable conditions on f and h, the inhomogeneous problem. −Δu + c2u = λ(f(u) + h(x)) for x ∈ Ω (Ω is an exterior domain in ℝN, N≧ 3) and has at least two positive solutions.
61 citations
TL;DR: The present studies show that the pathological features of lipid liver disease are anaemia and hepatic ceroidosis, and the main cause is assumed to be an imbalance of nutrients in daily feed and the lock of some lipotropic substances.
Abstract: The inadequate nutrient content of pellet feeds widely used in recent years in China for grass carp farming led to lipid liver degeneration in the fish The present studies show that the pathological features of lipid liver disease are anaemia and hepatic ceroidosis Other clinical features are; the ratio of liver to body weight exceeds 3% and lipid content exceeds 5% Extreme infiltration of hepaiocytes by lipid results in the following deteriorative effects: swelling of the liver cells, increase of lipid droplets in the cytoplasm and dislocation of the nucleus, loss of cytoplasm staining affinity, and increased activities of GOT and GPT in serum Lipid liver degeneration of grass carp can be divided into three stages: 1) deposition of liver lipid; 2) lipid infiltration of hepatic parenchyma; 3) atrophy of liver nucleus The causes of lipid liver degeneration are complicated, but the main cause is assumed to be an imbalance of nutrients in daily feed and the lock of some lipotropic substances
24 citations
TL;DR: In this paper, a set of atom equivalents is developed to relate ab initio total energies (6-31G ∗ basis set) to heats of formation. But the method was used to treat only 11 parameters to treat 62 sample molecules including acyclic and strained hydrocarbons.
Abstract: By using the linear-regression method a set of atom equivalents is developed to relate ab initio total energies (6-31G ∗ basis set) to heats of formation. Instead of about 50 parameters of the scheme reported previously only 11 parameters are employed to treat 62 sample molecules including acyclic and strained hydrocarbons, fluorinated and chlorinated hydrocarbons, and nitrogen-and oxygen-containing organic compounds. The calculated heats of formation are in good agreement with the experimental values: absolute deviation 1.34 kcal mol −1 , and mean-square deviation 1.80 kcal mol −1 .
16 citations
TL;DR: The title complex of as mentioned in this paper consists of an assembly of [C(NH2)3]+ cations, [TiO(CO3)3]4− anions, and water molecules which are interlinked by hydrogen bonds to form a three-dimensional network.
16 citations
TL;DR: This experiment stores and recalls two images and shows that the system has real time multiple-image storage and recall functions and an associative memory with a dynamic threshold level to decide the closest match of an incomplete input is proposed.
Abstract: We present a real time holographic associative memory implemented with photorefractive KNSBN:Co crystal as the memory element and a liquid crystal electrooptic switch array as the reflective thresholding device. Our experiment stores and recalls two images and shows that the system has real time multiple-image storage and recall functions. An associative memory with a dynamic threshold level to decide the closest match of an incomplete input is proposed.
16 citations
TL;DR: Microwave-assisted extraction coupled with high-speed counter-current chromatography is a powerful tool for extraction, separation and purification of dehydrocavidine from C. saxicola.
Abstract: Introduction – Dehydrocavidine is a major component of Corydalis saxicola Bunting with sedative, analgesic, anticonvulsive and antibacterial activities. Conventional methods have disadvantages in extracting, separating and purifying dehydrocavidine from C. saxicola. Hence, an efficient method should be established.
Objective – To develop a suitable preparative method in order to isolate dehydrocavidine from a complex C. saxicola extract by preparative HSCCC.
Methodology – The methanol extract of C. saxicola was prepared by optimised microwave-assisted extraction (MAE). The analytical HSCCC was used for the exploration of suitable solvent systems and the preparative HSCCC was used for larger scale separation and purification. Dehydrocavidine was analysed by high-performance liquid chromatography (HPLC) and further identified by ESI-MS and 1H NMR.
Results – The optimised MAE experimental conditions were as follows: extraction temperature, 60°C; ratio of liquid to solid, 20; extraction time, 15 min; and microwave power, 700 W. In less than 4 h, 42.1 mg of dehydrocavidine (98.9% purity) was obtained from 900 mg crude extract in a one-step separation, using a two-phase solvent system composed of chloroform–methanol–0.3 m hydrochloric acid (4 : 0.5 : 2, v/v/v).
Conclusion – Microwave-assisted extraction coupled with high-speed counter-current chromatography is a powerful tool for extraction, separation and purification of dehydrocavidine from C. saxicola. Copyright © 2009 John Wiley & Sons, Ltd.
15 citations
TL;DR: The presence of the 1-benzyltetrahydroisoquinoline-derived alkaloid α-allocryptopine is further chemical evidence supporting the argument that Tetradium is closely allied to Zanthoxylum and Phellodendron.
15 citations
TL;DR: In this article, twelve derivatives of tetraphenyl porphyrins with electron- withdrawing and -donating substituents in the benzene ring, and their Fe(III) and Mn(III), were prepared, some of which have not been reported.
01 Jan 1990
TL;DR: In this article, the use of a combined purification system, which includes an aquatic treatment pond with Typha latifolia Linn. (Typhaceae) as the dominant species, and a stabilization pond, to treat the wastewater from a Pb/Zn mine at Shaoguan, Guangdong Province, China.
Abstract: This paper describes the use of a combined purification system, which includes an aquatic treatment pond with Typha latifolia Linn. (Typhaceae) as the dominant species, and a stabilization pond, to treat the wastewater from a Pb/Zn mine at Shaoguan, Guangdong Province, China. A preliminary survey was made in 1983 of the mining area and it was noted that T. latifolia was growing luxuriously in areas affected by the wastewater emitted from the mine. A combined purification system was subsequently built by constructing a dam using waste rocks and gravels. Before entering the pond, the untreated wastewater contained rather high levels of total suspended solids (4,635 mg/l), chemical oxygen demand (14.5 mg/l) as well as Pb (1.6 mg/l) and Zn (1.9 mg/l). After passing through the purification pond, the water quality improved tremendously, with the total suspended solids reduced 99%, chemical oxygen demand 55%, Pb 95% and Zn 80%. The results of plant tissue analysis indicated that T. latifolia had an excellent ability in assimilating Pb and Zn, especially in the root portion. An ecological survey conducted in 1986 also indicated that there were several species of algae and fish flourishing in the pond, usually with a higher density in areas containing lower metal concentrations in the water.
TL;DR: Future applications of this model include determining: (1) the effect different concentrations of EGF and calcium in the media will have on esophageal proliferation and differentiation, and (2) the role of different basement membrane associated proteins on the plating efficiency of either isolated or outgrowth epithelial esphageal cells.
Abstract: Human esophageal epithelium obtained from intermediate autopsies (<12 h) was maintained as cell and explant cultures. In order to develop a serum-free, defined media culture model, several medias and additives were evaluated. The viability and differentiation of the epithelial cells cultured with serum-free, Keratinocyte Growth Media (KGM, Clonetics Co., San Diego, CA) was improved over that of esophageal cells and explants cultured in either serum-supplemented CMRL 1066 (OCM), serum-free additive-supplemented CMRL 1066, or cimetidine-supplemented CMRL 1066. The KGM component EGF was determined to be trophic for esophagus cells on the basis of findings of increased 3H-TdR tabelling in KGM cultures when compared to control cells grown in KGM without EGF (KBM). The morphologic pattern of the cytoskeletal proteins actin, keratin, and vimentin were characterized in isolated cell populations. The intermediate filaments, keratin, and vimentin were co-expressed in these epithelial cells. Esophageal explant viability, differentiation, and outgrowth from 15 cases were also evaluated in dishes coated with basement membrane associated proteins. Explants cultured in these dishes were equally well-preserved and differentiated. There were no significant differences in the explant histology when there was protein coating of the culture dishes, although one case showed improved outgrowth with laminin coating. A main advantage for using this culture system is that the same medium (KGM) can be used for both the culture of explants and isolated epithelial cells. Future applications of this model include determining: (1) the effect different concentrations of EGF and calcium in the media will have on esophageal proliferation and differentiation, and (2) the role of different basement membrane associated proteins on the plating efficiency of either isolated or outgrowth epithelial esophageal cells.
20 Dec 1990-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the average concentration of natural radionuclides in a high-radiation-background area and a control area in Yangjiang and the Enping county of the province Guangdong, PR China, have been measured by in-situ gamma spectrometry and by sampling analysis in our laboratory.
Abstract: The average concentration of natural radionuclides in a high-radiation-background area and a control area in Yangjiang and the Enping county of the province Guangdong, PR China, have been measured by in-situ gamma spectrometry and by sampling analysis in our laboratory. Average data on surface and depth distributions in soil have been obtained. The exposure rates to the environmental gamma-radiation field in both areas have been calculated from in-situ gamma spectra with Beck's conversion factor and by the method of total spectrum energy. The averaged total absorbed dose rates, including the cosmic-ray contribution obtained from in-situ gamma spectroscopy, are (18.2 ± 5.0) × 10 −8 and (6.6 ± 1.2) × 10 −8 Gy/h in the high-background and control areas, respectively.
TL;DR: It is demonstrated that viable H. pylori and human gastric epithelium can be maintained in explant organ culture and suggested that this gastric mucosal explant culture system may be useful in studying the significance of H.pylori infection of human gastrics epithelia.
Abstract: These studies were undertaken to define conditions under which Helicobacter (formerly Campylobacter) pylori and viable human gastric mucosa could coexist in tissue culture with the ultimate goal of de
TL;DR: Cinetique de la terpolymerisation catalysee par TiCl 4, Ti(OBu) 4 /MgCl 2 /PhCO 2 Et/Ph 2 SiCl 2/AlEt 3 and mesure de l'efficacite du catalyseur as mentioned in this paper.
Abstract: Cinetique de la terpolymerisation catalysee par TiCl 4 , Ti(OBu) 4 /MgCl 2 /PhCO 2 Et/Ph 2 SiCl 2 /AlEt 3 et mesure de l'efficacite du catalyseur. Determination par RMN 13 C de la microstructure des copolymeres; certains sont des elastomeres avec une cristallinite nulle. Mesure de la permeabilite de l'azote et de l'oxygene dans des membranes de terpolymere. Mesure des proprietes mecaniques des terpolymeres vulcanises
01 Dec 1990
TL;DR: The variation of the laser linewidth within an optically pumped NH3 FIR laser has been studied theoretically on the basis of three-level quantum system approach in this article, where it has been shown that the activation medium within the sample tube of an ASE FIR laser can be divided into three regions: A). Laser induced line narrowing region, in which the FIR laser linwidth is less than Lorentz linewight; B). Saturation broadening region, where the power density of the FIR signal becomes large enough to make saturation effect important and the linew
Abstract: The variation of the laser linewidth within an optically pumped NH3 FIR laser has been studied theoretically on the basis of three-level quantum system approach. It has been shown that the activated medium within the sample tube of an optically pumped ASE FIR laser can be divided into three regions: A). Laser induced line narrowing region, in which the FIR laser linewidth is less than Lorentz linewidth; B). Saturation broadening region, in which the power density of the FIR. signal becomes large enough to make saturation effect important and the linewidth broadens; C), Self-absorption narrowing region, in which the pumping energy density is below the threshold, so self-absorption dominates and the linewidth decreases. The necessary linewidth of the OPFIRL can be obtained by appropriate selection of the length of the sample tube.
TL;DR: The FDS peak-to-peak height, which describes the crystal damage in the implanted region, is related to the fractional number of dangling bonds, found to vary with 1-(Φ d /Φ)β, where β∼0.33 initially followed by a transfer to 0.78 until saturation, Φ is the total dose, and Φ d is a constant.
Abstract: Fractional-derivative spectra (FDS) have been developed for studying radiation effects in crystals by monitoring the optical interband transitions at critical points. Optical spectra of ${\mathit{E}}_{1}$ structure of ${\mathrm{As}}^{+}$-implanted Si, at doses from 3\ifmmode\times\else\texttimes\fi{}${10}^{12}$ to 1\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ions ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$, have been analyzed with use of 3/2th-derivative spectra. Symmetric line shapes in the ${\mathit{E}}_{1}$ region near 3.4 eV were found in the FDS both for crystalline and ion-implanted samples until the critical dose, above which the spectra became structureless. No change was determined, within the experimental errors, either in the line-shape symmetry or in the ${\mathit{E}}_{1}$ critical-point threshold for the implanted samples, compared with those of crystal Si, but a sharp increase in linewidth was observed. The FDS peak-to-peak height, which describes the crystal damage in the implanted region, is related to the fractional number of dangling bonds, found to vary with 1-(${\mathrm{\ensuremath{\Phi}}}_{\mathit{d}}$/\ensuremath{\Phi}${)}^{\mathrm{\ensuremath{\beta}}}$, where \ensuremath{\beta}\ensuremath{\approxeq}0.33 initially followed by a transfer to 0.78 until saturation, \ensuremath{\Phi} is the total dose, and ${\mathrm{\ensuremath{\Phi}}}_{\mathit{d}}$ is a constant. Both of the sharp changes in linewidth and in dependence of the number of dangling bonds take place at the dose of 3\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ions ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$, attributed to the accumulated stresses in the damaged region. The relationship between dangling bonds and structural disorder is discussed. For annealed samples, FDS directly yielded a shrinking of the ${\mathit{E}}_{1}$ threshold, together with a decrease in the optical response. They were found to be logarithmically dependent on impurity concentration.
TL;DR: In this paper, a phase transition between 60K to 80K was identified in the Niobate single crystal SBN, PBN, and KNSBN with tetragonal TB structure.
Abstract: The dielectric and pyroelectric experiments show that in the three kinds of ferroelectric niobate single crystals SBN, PBN, and KNSBN with tetragonal TB structure, there is a newly identified phase transition between 60K to 80K. The crystal's symmetry changes from point group 4mm to point group m as the temperature decreases.
TL;DR: The internal friction (IF) measurement technique is used to study the magnetization of pure iron, nickel and Permalloy-42 as mentioned in this paper, and it is measured with a torsion pendulum.
Abstract: The internal friction (IF) measurement technique is used to study the magnetization of pure iron, nickel and Permalloy-42 The IF of samples undergoing a uniform magnetic field sweep is measured with a torsion pendulum An IF peak is observed in the field range 0-10 Oe The field sweeping increases the IF and hence the characteristic quantity is the difference between the IF measured in field sweeping and that in a static field, which is called dynamic internal friction The dynamic IF shows a viscoelastic feature; it increases with increasing H/ omega where H is the field sweep rate and omega the angular frequency of the alternating strain The behaviour of the dynamic IF shows that it is caused by the domain wall motion in field sweeping and thus is related to a magnetomechanical interaction
01 Feb 1990
TL;DR: A motion vision system is developed in which a moving object can be detected and image displacement can be estimated based on human visual characteristics and use of a multiresolution image.
Abstract: A motion vision system is developed in which a moving object can be detected and image displacement can be estimated based on human visual characteristics and use of a multiresolution image. The system consists of four parts: (1) Temporal gradient, logic AND, and dynamic thresholding operations are used to obtain the primary mask. (2) A region growing algorithm is applied. (3) A hierarchical object detection algorithm is used to identify image patterns. (4) Displacement of the image is estimated by breaking each frame of the motion sequence into local regions (edges). A search is undertaken to discover how the image pattern within a given region appears displaced. This search takes the form of motion channels, the output of which are used to obtain the estimation of displacement. A correlative measure is proposed to match the patterns.
TL;DR: In this article, the microstructure distributions of ethylene-propene(EP) copolymers and propene homopolymers prepared with supported titanium catalyst were analyzed by 13C NMR spectroscopy.
Abstract: The microstructure distributions of ethylene-propene(EP) copolymers and propene homopolymers prepared with supported titanium catalyst were analyzed by 13C NMR spectroscopy. A two-site model with an isospecific site and a non-stereospecific site was used to describe the stereospecific polymerization of propene. A second two-site model with individual r1r2 = 1 was applied to the analysis of the ethylene-propene copolymerization. The addition of an external base, ethyl benzoate (EB), alters the relative concentrations of catalytic sites. Based on the comparison of the results from the homopolymers and copolymers prepared under different EB concentrations, the correlations between the stereospecificity and the activity toward the monomers were established: the isospecific site produces the copolymer with lower ethylene content; the non-stereospecific site gives the copolymer with higher ethylene content.
TL;DR: The physical vacuum state and general expression for the Hamiltonian ofd+1 dimensional lattice gauge theory were given by incorporating the exact ground state of pure gauge theory and the variational fermion vacuum state.
Abstract: The physical vacuum state and general expression for the Hamiltonian ofd+1 dimensional lattice gauge theory are given by incorporating the exact ground state of pure gauge theory and the variational fermion vacuum state. The applications toSU(2) andSU(3) gauge theories in 2+1 and 3+1 dimensions are demonstrated and the fermion condensates\(\left\langle {\bar \psi \psi } \right\rangle \) as functions of 1/g2 are calculated.
TL;DR: In this paper, the wind flow around a 31-storey tower block with a low-rise block on the other side of a 20 m-wide street was computed by the SIMPLE method.
TL;DR: In this article, the interaction of the electrons with the phonons in GaAs/AlGaAs quantum wells, quantum well wires, and quantum well boxes has been studied by means of their time resolved photoluminescence (PL) spectra.
Abstract: The interaction of the electrons with the phonons in GaAs/AlGaAs quantum wells, quantum well wires, and quantum well boxes has been studied by meansuring their time resolved photoluminescence (PL) spectra. In the quantum well (QW) system, relaxation time of the electron energy of the narrower well is shorter than that of the wider well. It is attributed to the stronger interaction of the electrons with the interface mode phonons. In the QW wires and QW boxes, the shortening of the relaxation time is obvious. It is due to the stronger electron-phonon interaction caused by the reduction of screening effect. Our experiments also demonstrated the incident laser intensity dependence of the relaxation time.
TL;DR: In this article, electrical conductivity in the Sr(Fe1−xTix)Oy system (0.0≤x≤0.9,y≤3) has been further studied by means of Mossbauer spectroscopy.
Abstract: On the basis of our previous work electrical conductivity in the Sr(Fe1−xTix)Oy system (0.0≤x≤0.9,y≤3) has been further studied by means of Mossbauer spectroscopy. When 0.0≤x≤0.6, the concentration of Fe3+ (II) doublet relates to the final firing temperature and electrical conductivity of the materials is sensitive to the concentration of Fe3+ (II). Atx=0.25, the curve of the resistivity versus Ti contentx shows a local minimum which is observed for the first time. The results indicate that the coexistence of Fe4+ and Fe3+ in the same lattice leads to high conductivity; the conductivity increases when the Fe4 concentration approaches to that of the Fe3+ one. When the temperature is at 260 K and 230 K, the presence of the intermediate state showing quadrupole splitting has an effect on the conductivity of the materials.
TL;DR: In this paper, an estimate to the maximum modulus is made for a special case of quasi-linear elliptic equations, i.e., the solutions of B satisfy the following structural conditions:
Abstract: Let G be a bounded domain in E
n
.Consider the following quasi-linear elliptic equation
Although the boundedness of generalized solutions of the equation is proved for very general structural conditions, it does not supply a priori estimate for maximum modulus of solutions. In this paper an estimate to the maximum modulus is made firstly for a special case of quasi-linear elliptic equations, i.e. the
$$\overrightarrow A $$
and B satisfy the following structural conditions:
01 Feb 1990
TL;DR: A pyramid-based method of dynamic thresholding where the Gaussian pyramid is used to support a “coarse-to-fine” search strategy is presented.
Abstract: A pyramid-based method of dynamic thresholding where the Gaussian pyramid is used to support a “coarse-to-fine” search strategy is presented. At the top level of the pyramid the image is divided into four subimages, and in each subimage, the gray-level variance is analyzed to find whether there is an edge. The hierarchical search is continued until the bottom level of the pyramid, or the original image, is reached. At the bottom level the threshold values of those subimages where an edge is present are estimated, and the value of zero is assigned to those subimages where no edge is present. Finally, by using interpolations of subimage and pixel threshold values, the dynamic threshold values are found.
Journal Article•
TL;DR: It is evident that moderate doses of chloroguanide retarded the formation of schizonts and thus delayed the primary parasitaemia in Rhesus monkeys inoculated with a large number of sporozoites of Plasmodium inui dissected from the salivary glands of infected mosquitoes, Anopheles dirus.
Abstract: Three Rhesus monkeys inoculated with a large number of sporozoites of Plasmodium inui dissected from the salivary glands of infected mosquitoes, Anopheles dirus. Two of the monkeys (inoculated with 8.06 x 10(5) and 1.3 x 10(7) sporozoites, respectively) were treated with chloroguanide base 6 mg/(kg.d) x 4 d starting from 24 h after the inoculations and the other one (inoculated with 5.93 x 10(6) sporozoites) was not treated with chloroguanide as control. The primary parasitaemia attacks occurred in the former 2 monkeys were 31 and 25 d respectively after inoculation, while in the control was 7.5 d. Liver biopsies were done in all of the 3 monkeys, normal schizonts were seen in the control monkey on d 8 after inoculation, while none were detected in the 2 monkeys treated with chloroguanide. However, the retarded exoerythrocytic schizonts were found by indirect fluorescent antibody test (IFAT) in liver sections of the monkey inoculated with 1.3 x 10(7) sporozoites. Therefore, it is evident that moderate doses of chloroguanide retarded the formation of schizonts and thus delayed the primary parasitaemia.