Showing papers by "Chinese Academy of Sciences published in 1987"
TL;DR: In this article, the feasibility and effectiveness of teaching several mathematical skills by presenting students with carefully chosen sequences of worked-out examples and problems without lectures or other direct instruction is demonstrated.
Abstract: This article demonstrates the feasibility and effectiveness of teaching several mathematical skills by presenting students with carefully chosen sequences of worked-out examples and problems - without lectures or other direct instruction. Thinking-aloud protocols of 20 students learning factorization by this method are analyzed to determine the kinds and depth of understanding students attained. Students did not simply memorize procedures but were able to recognize when the procedures were applicable and to apply them. Most students were also able to use their understanding of the concept of factorization to help learn the procedures and to check their results. The method of learning from examples has now been tested successfully with a class covering the entire 3-year curriculum in algebra and geometry in a Chinese middle school.
352 citations
TL;DR: Injection of the active enzyme elicited long-lasting enhancement of synaptic transmission, similar to LTP, whereas inactivated kinase failed to do so and the observed changes included an increased amplitude of the excitatory post-synaptic potential and an increased probability of firing and a reduced latency of the associated actin potential.
Abstract: Long-term potentiation (LTP) in the hippocampus is an interesting example of synaptic plasticity because of its induction by physiological discharge rates and its long duration1,2. Of the possible biochemical mechanisms that regulate prolonged changes in cell function, protein phosphorylation is a particularly attractive candidate3. We have therefore examined the effect of intracellular injection of calcium/diacylglycerol-dependent protein kinase (protein kinase C (PKC)) in CA1 pyramidal neurones in hippocampal slices. Injection of the active enzyme elicited long-lasting enhancement of synaptic transmission, similar to LTP, whereas inactivated kinase failed to do so. The observed changes included an increased amplitude of the excitatory post-synaptic potential (e.p.s.p.) and an increased probability of firing and a reduced latency of the associated actin potential.
335 citations
TL;DR: A 2D quasicrystal with an eightfold rotational axis has been found in rapidly solidified V- Ni-Si and Cr-Ni-Si alloys by means of transmission electron microscopy.
Abstract: A 2D quasicrystal with an eightfold rotational axis has been found in rapidly solidified V-Ni-Si and Cr-Ni-Si alloys by means of transmission electron microscopy. The electron diffraction pattern taken along this axis shows no periodicity but a clear eightfold orientation symmetry. The corresponding high-resolution electron microscopic image agrees well with the 2D eightfold quasilattice consisting of squares and 45\ifmmode^\circ\else\textdegree\fi{} rhombi.
280 citations
TL;DR: Comparison of the crystal structure of inactive unliganded trp aporepressor with that of trp repressor shows that binding tryptophan activates the dimer a thousandfold by moving two symmetrically-disposed flexible bihelical motifs.
Abstract: Comparison of the crystal structure of inactive unliganded trp aporepressor with that of trp repressor shows that binding tryptophan activates the dimer a thousandfold by moving two symmetrically-disposed flexible bihelical motifs. These flexible 'DNA-reading heads' flank a highly inflexible core domain formed by an unusual arrangement of interlocking alpha-helices from both subunits.
224 citations
TL;DR: In this article, the results of the first carbon isotopic study of the Upper Proterozoic carbonate strata from the type locality of the Sinian System in the Yangtze Gorges sections near Yichang, South China, and discuss their implications for accumulation of organic matter.
Abstract: The δ13C values for Phanerozoic marine carbonates display secular trends, mainly in the range –1 to 2‰1. These have been interpreted as primary features reflecting changes in the carbon isotope composition of dissolved bicarbonate in seawater, brought about largely by variations in the proportions of carbon being sequestered in the oxidized and reduced carbon reservoirs1,2. Carbon isotope trends are not as well established for the Precambrian, but there are indications that Upper Proterozoic sequences contain carbonates with unusually high δ13C values3–9. Here we present the results of the first carbon isotopic study of the Upper Proterozoic carbonate strata from the type locality of the Sinian System in the Yangtze Gorges sections near Yichang, South China, and discuss their implications for accumulation of organic matter. We also compare the results for these Chinese strata with δ13C trends in other Upper Proterozoic–Cambrian sequences, and assess the extent to which such isotopic data can be used to make stratigraphic correlations between widely spaced sequences.
151 citations
TL;DR: In this paper, a series of Ba2(Y1−xPrCu3O9−y ) solid solutions with the orthorhombic distorted perovskite structure were prepared with the O(Y) structure.
Abstract: A series of Ba2(Y1−x
Pr
x
)Cu3O9−y
solid solutions were prepared with the orthorhombic distorted perovskite structure. The compound Ba2PrCu3O9−y
belonging to tetragonal system is a good semiconductor. The superconductivity is observed for samples withx<0.6. With the increase of Y content, the distortion of crystal structure is greater and the superconductive transition temperature of zero resistanceTc(0) raises.
86 citations
TL;DR: In this article, the synthesis and crystal structure of a cubane-like cluster with a [Mo3S4[S2P(OC2H5)2]4}·H20.
64 citations
TL;DR: In this paper, the adsorption of sulphate and fluoride by three variable charge soils was studied and the ratios of the amount of released OH−to that of adsorbed SO2-4 at pH 5−0 were 0.12, 0.14 and 0.20 for the three soils, respectively, much lower than the corresponding OH−/F− ratios which ranged from 0.3 to 1.0.
Abstract: SUMMARY
The adsorption of sulphate and fluoride by three variable charge soils was studied. Adsorption increased with increase in the amount of sulphate added at constant pH, and decreased with increase of pH.
The ratios of the amount of released OH−to that of the adsorbed SO2-4 at pH 5–0 were 0.12, 0.14 and 0.20 for the three soils, respectively, much lower than the corresponding OH−/F− ratios which ranged from 0.3 to 1.0. For a ferric acrisol the OH− released accounted, on average, for only 15% of the SO2-4 adsorbed, leaving more than 60% to be explained by the decrease in positive charge and the increase in negative charge carried by the soil.
63 citations
TL;DR: In this article, the coexistence of the tenfold twins and decagonal quasicrystal is confirmed by high-resolution electron microscopy, and the development of the 10fold diffraction pattern from the twins is clearly shown, and compared to the ten-fold pattern of the decagonal phase found in the same specimen.
Abstract: Al13 Fe4 tenfold twins, found in rapidly cooled Al–Fe alloys, have been studied by transmission electron microscopy. The development of the tenfold diffraction pattern from the twins is clearly shown, and compared to the tenfold pattern of the decagonal phase found in the same specimen. The coexistence of the tenfold twins and decagonal quasicrystal is confirmed by high-resolution electron microscopy.
62 citations
TL;DR: A strong correlation was demonstrated between erb B expression and alteration of its gene structure in human cirrhotic liver and hepatoma and a lack of change in mRNA levels during fetal liver development and in hepatoma.
59 citations
TL;DR: This is a report on the present status of computer-aided enumeration and classification of benzenoids and coronoids (polyhexes) and on the existing data from previous works.
Abstract: This is a report on the present status of computer-aided enumeration and classification of benzenoids and coronoids (polyhexes). The existing data from previous works are displayed in comprehensive tables. Numerous data from papers in press are included, as well as original contributions.
TL;DR: In this article, high-resolution electron energy loss spectra of the sulfur 2p, 2s and oxygen 1s inner shells of SO 2 have been obtained under conditions of high impact energy (1-3 keV) and zero-degree scattering angle.
TL;DR: In this article, it was shown that decagonal quasicrystal and 10-fold twins of monoclinic al-Fe coexist in rapidly cooled Al-Fe alloy.
Abstract: We have found that decagonal quasicrystal and 10-fold twins of monoclinic ${\mathrm{Al}}_{13}$${\mathrm{Fe}}_{4}$ coexist in rapidly cooled Al-Fe alloy. The tenfold axis of the decagonal phase is parallel to the pseudotenfold [010] axis of the twins. There is good coincidence between the strong spots of the decagonal twofold diffraction patterns and the corresponding diffraction patterns of ${\mathrm{Al}}_{13}$${\mathrm{Fe}}_{4}$. This orientation relationship is also observed when the decagonal phase transforms into a ${\mathrm{Al}}_{13}$${\mathrm{Fe}}_{4}$ twin on heating in an electron microscope. This shows that the decagonal quasicrystal is not a set of twins although they are closely related in structure.
TL;DR: Two new polyphenols, 4,6di-O-galloylarbutin and 2,4,6-tri-Ogalloyl-D-glucose, were isolated from the root of Bergenia purpurascens as mentioned in this paper.
TL;DR: The structure of corianin was elucidated on the basis of nuclear magnetic resonance and chemical evidence and the previously proposed structure for coriatin was also s ubstantiated.
Abstract: Pseudotutin previously isolated from Coriaria japonica A. GRAY was revealed to be a molecular compound consisting of equimolar tutin (2) and a new related sesquiterpene lactone, corianin (3). Corianin was also isolated together with coriamyrtin (1), tutin (2) and coriatin (4), from Loranthus parasiticus MERR., a parasitic plant that grows on the twigs of Coriaria sinica MAXIM. The structure of corianin was elucidated on the basis of nuclear magnetic resonance and chemical evidence. The previously proposed structure (4) for coriatin was also s ubstantiated.
TL;DR: In this paper, a new criterion for superconductivity was proposed, which can be applied to all the elements in the periodic table, and the criterion showed that the values of electronegativity of all superconducting elements concentrate in a narrow range from 1.3 to 1.9 and that elements with values outside this region would be non-superconductive.
TL;DR: The selectivity and analytical application of a thin-layer electrochemical detector comprised of glassy carbon electrode coated with Nafion film improved greatly and the response for neutral molecules is decreased three-fold, based on the results of flow injection experiments.
TL;DR: From the unripe fruits of Rosa roxburghii TRATT, two new hydrolyzable tannins were isolated and the structures of new tannnins were elucidated on the basis of chemical and spectral evidence.
Abstract: From the unripe fruits of Rosa roxburghii TRATT, two new hydrolyzable tannins, roxbin A (1) (a dimeric cllagitannin) and roxbin B (9), were isolated along with rugosin F (2), pedunculagin (3), casuarictin (4), alnusiin (5) stachyurin (6), tellimagrandin II (7), 2,3-O-(S)-hexahydroxydiphenoyl-D-glucose and (+)-catechin The structures of new tannnins were elucidated on the basis of chemical and spectral evidence
TL;DR: Positive ion fast atom bombardment mass spectrometric sensitivities of seven amino acids and the corresponding di-isopropylphosphorylated derivatives were carefully compared and showed an improvement in sensitivity by factors of 4-29.
Abstract: Positive ion fast atom bombardment mass spectrometric sensitivities of seven amino acids and the corresponding di-isopropylphosphorylated derivatives were carefully compared. Results showed that an improvement in sensitivity by factors of 4-29, mostly above 10, were achieved after the derivatization. The chemical noise derived from glycerol matrix was also greatly reduced by this derivatization.
TL;DR: Weakened binding of fibronectin to collagen occurred near the end of gestation concomitant with an increase in the quantity of larger polylactosamine glycopeptides.
TL;DR: A new alkaloid, N-allylnorgalanthamine, was isolated from the bulbs of LYCORIS GUANGXIENSIS Y. Hsu et Q. Fan (Amaryllidaceae) and the structure of 1 was established through the interpretation of spectral data.
Abstract: A new alkaloid, N-allylnorgalanthamine ( 1), was isolated from the bulbs of LYCORIS GUANGXIENSIS Y. Hsu et Q. J. Fan (Amaryllidaceae). Additionally, seven known alkaloids, lycorine, narwedine, galanthamine, lycoramine, crinine, norgalanthamine, and pseudolycorine were also obtained. The structure of 1 was established through the interpretation of spectral data.
TL;DR: In this paper, the authors present results obtained from a wide range of Chinese pottery, spanning the interval from 4000 BC to the present, indicating that the field behaviour was more complex.
Abstract: Past values for the geomagnetic intensity may be obtained by laboratory analysis of the thermoremanent magnetization carried by clay baked in ancient times. From global averages1–3 of such determinations it is commonly accepted that the intensity in any given region went through a broad maximum about 2,000 years ago, reaching a level ∼50% higher than at present. Here we present results obtained from a wide range of Chinese pottery, spanning the interval from 4000 BC to the present, indicating that the field behaviour was more complex. The intensity was high between 1500 and 1000 BC and again in the first half of the first millennium AD. Comparison with results reported4,5 for Western Asia, Egypt and Crete suggests that these high values are due to non-dipole disturbances in the geomagnetic field, consistent with long-term records6–8 of the cosmogenic radioisotopes 14C and 10Be.
TL;DR: In this article, the title compounds were synthesised from d-galactose via 9 steps and the key intermediates for the synthesis were 2-O -acetyl-3,4,6-tri- O -benzyl- and 2- O −acetyl -3, 4, 6-tri O -(p -bromobenzyl)-β- d -galactopyranosyl fluorides with silver fluoride.
TL;DR: The properties of plasmid replication proteins and direct nucleotide sequence repeats that are important for their opposing positive and negative roles in the regulation of the initiation of replication are described with particular emphasis onplasmid R6K of Escherichia coli.
Abstract: As for bacterial and animal viruses that employ different mechanisms for their duplication in a host cell, plasmids have evolved different strategies to assure their hereditary stability or maintenance at a specific copy number during cell growth and division. A characteristic feature of plasmid replication control, however, is an involvement of one or more negatively controlling elements. Furthermore, a majority of the bacterial plasmids examined to date contain direct nucleotide sequence repeats at their origin of replication and encode a replication protein that binds to these repeat sequences. The binding of the replication protein (pi protein) specified by the antibiotic resistance plasmid R6K to a set of 22 base pair direct nucleotide sequence repeats is required for the initiation of replication at each of three origins of replication (alpha, beta and gamma) within a 4 Kb segment of R6K. The pi initiation protein is multifunctional in that it has both positive and negative activities in both controlling the initiation of replication and autoregulating its own synthesis. Similarly, the direct repeats of plasmid R6K and several other plasmid systems play more than one role in plasmid replication. These repeats, termed iterons, are not only required for origin activity but also exert a negative effect on plasmid copy number possibly as a result of their 'titration' of a plasmid encoded replication protein. The properties of plasmid replication proteins and direct nucleotide sequence repeats that are important for their opposing positive and negative roles in the regulation of the initiation of replication are described with particular emphasis on plasmid R6K of Escherichia coli.
TL;DR: In this paper, the MBE growth of high quality modulation doped heterostructures on GaAs (110) without intentional misorientation was reported, and the same two-dimensional electron gas characteristics as the AlGaAs/GaAs (100) interface were obtained.
TL;DR: A recent World Bank report has stated that the world population will grow continuously until reaching a total of 12 to 13 billion people by the middle of the 22nd century, and much of this growth will take place in developing countries.
Abstract: A recent World Bank report has stated that the world population will grow continuously until reaching a total of 12 to 13 billion people by the middle of the 22nd century. Much of this growth will take place in developing countries. Of the 80 million births forecast for 1984, 70 million were expected to be born in developing countries. These countries now comprise three fourths of the world's population. Due to the success of China's population policies, however, the growth rate in East Asia, which peaked at 2.2% in 1970–75, is now 1.1% and should drop below 1% after the year 2000. China's experience to hold population growth down is most valuable to the world, especially to the developing countries.
TL;DR: In this paper, the requirements for batch dry-fermentation with agricultural wastes were reported and the optimum initial solids content was 25-30%, with ratios of rice straw to manure (on a dry matter basis) of 2 or 1:1.
TL;DR: In this paper, a slightly modified SOS Chromotest procedure was developed and applied to six sediment samples from Prince Edward Island, which showed weak inducibility expressed by SOSIP-SOS Inducing Potency.
Abstract: Noting that the inducibility of samples tested with the SOS Chromotest increased with increasing colour development time, a slightly modified Chromotest procedure was developed and applied to six sediment samples from Prince Edward Island. The samples tested by this newly developed short-term genotoxicity test showed weak inducibility expressed by the SOSIP—SOS Inducing Potency. Five of the six samples were activated by the addition of S-9 fraction, commonly used with the Ames/Microsome test. Only one of the samples showed toxic activity by the Microtox test.
TL;DR: In this article, the photomineralization mechanisms of two nonionic surfactants, N- (2-hydroxyethyl) dodecanoyl amide and N, n-bis (2]-dioxioxioxyl amide based on temporal changes in surface tension, ζ-potential, evolution of CO2 gas, formation of NH4+ and NO3- ions, and formation of carboxylic acids were determined.
Abstract: Study was made to determine the photomineralization mechanisms of two nonionic surfactants, N- (2-hydroxyethyl) dodecanoyl amide and N, N-bis (2-hydroxyethyl) dodecanoyl amide based on temporal changes in surface tension, ζ-potential, evolution of CO2 gas, formation of NH4+ and NO3- ions, and formation of carboxylic acids. The adsorption of surfactants on the TiO2 surface was also examined by dynamic light-scattering. The generation of NH4+ ions exceeded that of NO3- ions in the photodegradation of either surfactant. Positions on the surfactants attacked by ·OH radicals were determined by molecular orbital calculations of frontier electron density. Negatively charged positions in the surfactants adsorb on the positive TiO2 surface and could consequently be easily attacked by ·OH radicals. A photooxidation mechanism of N- (2-hydroxyethyl) dodecanoyl amide and N, N-bis (2-hydroxyethyl) dodecanoyl amide is proposed on the base of the present experimental data and comparison with calculation results.
TL;DR: In this paper, the authors derived an analytic solution for single solitons of the A and B types with use of multiple-scale analysis, where the velocity of the soliton is proportional to the shear rate.
Abstract: Equations of motion for nematic liquid crystals under time-dependent shear are derived. Soliton solutions are investigated. When the soliton velocity is large and the shear varies slowly in time, approximate analytic solutions for single solitons of the A and B types are found with use of multiple-scale analysis. These perturbed solitons move with time-dependent velocities but are constant in shape and carry no tails. The velocity is proportional to the shear rate. Numerical calculations of the director equation of motion are performed and are in agreement with the analytic results. A recent experiment in which dark lines (under white light) excited by a periodically moving plate at one end of a nematic cell are observed is analyzed and interpreted according to our theory. Good agreement between theory and experiment is obtained.