Showing papers by "University of Science and Technology of China published in 1998"
TL;DR: In this paper, the authors present a synthesis of crustal evolution in SE China based on extensive Nd and Sr isotopic data compiled from the literature for intrusive granitoids, volcanic, sedimentary and metamorphic rocks from three major tectonic units of SE China: Dabie, Yangtze and Cathaysia.
881 citations
TL;DR: In this paper, the conformation of individual PNIPAM chains change from a coil to a fully collapsed thermodynamically stable single chain globule and then back to a coil in an extremely dilute aqueous solution (6.7 10-7 g/mL).
Abstract: Using a newly prepared nearly monodisperse (Mw/Mn < 1.05) high molar mass (Mw = 1.3 107 g/mol) poly(N-isopropylacrylamide) (PNIPAM) sample, we successfully, for the first time, made the conformation of individual PNIPAM chains change from a coil to a fully collapsed thermodynamically stable single chain globule and then back to a coil in an extremely dilute aqueous solution (6.7 10-7 g/mL). The average chain density in the globule state is 0.34 g/mL, close to 0.40 g/cm3 predicted on the basis of a space-filling model, indicating that the globule still contains 66% water even in its fully collapsed state. At a given temperature around the lower critical solution temperature, the chains are smaller in the globule-to-coil transition than in the coil-to-globule transition, revealing that the coil-to-globule transition is an irreversible process. The hysteresis can be attributed to the formation of intrachain structures, presumably the intrachain hydrogen bonding, in the globule state. We confirmed the existen...
647 citations
TL;DR: In this article, a nearly monodisperse high molar mass poly( $N$-isopropylacrylamide) (PNIPAM) sample was used to study the globule-to-coil transition of a single homopolymer chain in solution.
Abstract: Using a nearly monodisperse high molar mass poly( $N$-isopropylacrylamide) (PNIPAM) sample, we successfully made the conformation change of individual PNIPAM chains from a coil to a fully collapsed stable single chain globule in an extremely dilute aqueous solution, which enabled us to study for the first time the globule-to-coil transition of a single homopolymer chain in solution. A comparison to the coil-to-globule and the globule-to-coil transitions revealed a hysteresis in the globule-to-coil transition. Our results also confirmed the existence of two additional thermodynamically stable states between the coil and the globule states, namely, the crumpled coil and the molten globule.
555 citations
TL;DR: In this article, the authors constructed a probabilistic quantum cloning machine by a general unitary reduction operation, which yielded faithful copies of the input states with a postselection of the measurement results.
Abstract: We construct a probabilistic quantum cloning machine by a general unitary-reduction operation. With a postselection of the measurement results, the machine yields faithful copies of the input states. It is shown that the states secretly chosen from a certain set $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}{|{\ensuremath{\Psi}}_{1}〉,|{\ensuremath{\Psi}}_{2}〉,\dots{},|{\ensuremath{\Psi}}_{n}〉}$ can be probabilistically cloned if and only if $|{\ensuremath{\Psi}}_{1}〉,|{\ensuremath{\Psi}}_{2}〉,\dots{},\mathrm{and}|{\ensuremath{\Psi}}_{n}〉$ are linearly independent. We derive the best possible cloning efficiencies. Probabilistic cloning has a close connection with the problem of identification of a set of states, which is a type of $n+1$ outcome measurement on $n$ linearly independent states. The optimal efficiencies for this type of measurement are obtained.
377 citations
TL;DR: A solvent-coordinating molecular template mechanism to synthesize one-dimensional nanostructure CdS was speculated in the equation below as discussed by the authors, where the solvent molecule ethylenediamine played an important role.
Abstract: A solvent-coordinating molecular template mechanism to synthesize one-dimensional nanostructure CdS was speculated in the equation below. The solvent molecule ethylenediamine plays an important rol...
300 citations
TL;DR: In this article, the authors make the assumption that all quantum bits (qubits) interact with the same environment rather than the assumption of separate environments for different qubits, and they find that the qubits decohere collectively.
Abstract: Decoherence in quantum-computer memory due to the inevitable coupling to the external environment is examined. We make the assumption that all quantum bits (qubits) interact with the same environment rather than the assumption of separate environments for different qubits. It is found that the qubits decohere collectively. For some kinds of entangled input states, no decoherence occurs at all in the memory, even if the qubits are interacting with the environment. Based on this phenomenon, a scheme is proposed for reducing the collective decoherence. We also discuss possible implications of this decoherence model for quantum measurements.
246 citations
TL;DR: In this article, the oxygen and hydrogen isotope compositions of mineral separates have been determined for ultrahigh pressure eclogites from Shuanghe in the eastern Dabie Mountains and from Donghai in the western Sulu terrane, East China.
228 citations
TL;DR: In this article, the formation of double degenerates via binary interactions was investigated and the effects of various assumptions about age, metallicity, mass ratio distribution and wind velocity were explored.
Abstract: I systematically investigate the formation of double degenerates (DDs) via binary interactions. I consider three evolutionary channels for their formation [stable Roche lobe overflow (RLOF) plus common envelope (CE), CE plus CE, exposed core plus CE], and carry out Monte Carlo simulations. I explore the effects of model parameters, such as the tidal-enhancement parameter for stellar wind, the mass transfer efficiency for stable RLOF and the CE ejection efficiency, on my results. I also explore the effects of various assumptions about age, metallicity, mass ratio distribution and wind velocity. My results show that the model is successful in the explanation of the formation of DDs. I explain satisfactorily the distributions of masses, mass ratios, orbital periods and birth rate of the observed DDs. The main conclusions are the following. (i) Stable RLOF plus CE and CE plus CE are the main evolutionary scenarios leading to the formation of DDs. (ii) The Galactic birth rate of DDs is 0.03 yr(-1), and the birth rate of DDs with helium (He) white dwarfs (WDs) as brighter components is 0.017 yr(-1). (iii) The number of detectable DDs in our Galaxy is 3 x 10(6), and DDs with brighter He WDs make up 56 per cent. (iv) The distribution of orbital periods for detectable DDs peaks around 6 h. (v) WD 0957-666 and WD 1101+364 are formed through the stable RLOF plus CE scenario, and WD 0135-052 is possibly a carbon-oxygen (CO) WD pair rather than a helium (He) WD pair. (vi) The Galactic birth rates of close i, respectively. (vii) The mergers of two WD binaries and DD mergers are 0.074 and 0.029 yr(-1), respectively. (vii) The merges of two He WDs and the mergers of He and CO WDs have masses of 0.61 +/- 0.09 and 0.96 +/- 0.13 M., respectively. (viii) Mass transfer during stable RLOF is not conservative. (ix) A tidally enhanced stellar wind exists. I also investigate the formation of Type Ia supernovae (SNe Ia), cataclysmic variables (CVs), subdwarf O-type (sdO) stars and R Coronae Borealis (R CrB) stars. The birth rates of SNe Ia and CVs are successfully explained in the above model. The model also shows that CVs with long orbital periods tend to have CO WDs. The birth rates of the mergers of two He WDs (sdO stars) and the mergers of He and CO WDs (R CrB stars) are 0.006 and 0.018 yr(-1) in the Galaxy, respectively. The birth rates of CVs, DDs, DD mergers and SNe Ia are more sensitive to the recent stellar formation history than to the past one.
227 citations
TL;DR: In this paper, the effect of pH on the autoxidation rate of pyrogallol was investigated in the presence of EDTA or DETAPAC in the pH range 7.87 to 9.10.
197 citations
TL;DR: In this article, a solvent-othermal route to group II−VI nanocrystalline CdE (E = S Se, Te) semiconductors has been successfully developed, which can be expressed as CdC2O4 + E CdS + 2CO2↑.
Abstract: A novel solventothermal route to group II−VI nanocrystalline CdE (E = S Se, Te) semiconductors has been successfully developed. The reaction can be expressed as CdC2O4 + E CdE + 2CO2↑. As-prepared CdE powders in polyamines such as ethylenediamine, diethylenetriamine, and triethylenetetraamine display rodlike morphology with diameters of 20−50 nm and lengths up to several microns. The morphology of CdE powders in the present method can be controlled by choosing different solvents. The CdS nanorods synthesized in polyamines display different optical properties from the disklike CdS particles synthesized in pyridine.
190 citations
TL;DR: A general approach for constructing a response system to implement generalized chaos synchronization with drive systems is proposed, i.e., that encoding communication realized through generalized synchronization is more reliable than the usual synchronization methods.
Abstract: A general approach for constructing a response system to implement generalized chaos synchronization with drive systems is proposed. Possible applications of generalized chaos synchronization to communication are discussed, i.e., that encoding communication realized through generalized synchronization is more reliable than the usual synchronization methods.
TL;DR: In this paper, the authors show that the component of the kinetic temperature in the direction perpendicular to the magnetic field, for both isotropic and anisotropic temperature distributions, affects both the amount of Doppler dimming and pumping.
Abstract: Recent observations of the spectral line profiles and intensity ratio of the O VI λλ1032 and 1037.6 doublet by the Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO), made in coronal holes below 3.5 RS, provide evidence for Doppler dimming of the O VI λ1037.6 line and pumping by the chromospheric C II λ1037.0182 line. Evidence for a significant kinetic temperature anisotropy of O5+ ions was also derived from these observations. We show in this Letter how the component of the kinetic temperature in the direction perpendicular to the magnetic field, for both isotropic and anisotropic temperature distributions, affects both the amount of Doppler dimming and pumping. Taking this component into account, we further show that the observation of the O VI doublet intensity ratio less than unity can be accounted for only if pumping by C II λ1036.3367 in addition to C II λ1037.0182 is in effect. The inclusion of the C II λ1036.3367 pumping implies that the speed of the O5+ ions can reach 400 km s-1 around 3 RS, which is significantly higher than the reported UVCS values for atomic hydrogen in polar coronal holes. These results imply that oxygen ions flow much faster than protons at that heliocentric distance.
TL;DR: It is shown that the ideal of any degree n planar rational curve can be generated by two polynomials that are each linear in x, y and degree n1 and n2 (⩾ n1) in t, n1 + n2 = n.
TL;DR: In this article, the volume phase transition of PNIPAM microgels was studied by a combination of static and dynamic laser light scattering and the thermodynamically stable collapsed single-chain globule was observed for the first time.
TL;DR: In this paper, a new class of backward stochastic differential equations involving the integral with respect to a continuous increasing process is studied, and a probabilistic formula for solutions of semilinear partial differential equations with Neumann boundary condition is given, where the boundary condition itself is nonlinear.
Abstract: We study a new class of backward stochastic differential equations, which involves the integral with respect to a continuous increasing process This allows us to give a probabilistic formula for solutions of semilinear partial differential equations with Neumann boundary condition, where the boundary condition itself is nonlinear We consider both parabolic and elliptic equations
TL;DR: In this paper, an empirical model for predicting oxygen diffusivity from anion porosity is presented for a wide range of minerals, based on the examination of experimental diffusion data under anhydrous and hydrothermal conditions.
Abstract: An empirical model for predicting oxygen diffusivity from anion porosity is presented for a wide range of minerals. It is based on the examination of experimental diffusion data under anhydrous and hydrothermal conditions. The relationship between activation energies and pre-exponential factors in all minerals is assumed to obey a common compensation law regardless of diffusion medium (H2O, OH-, CO2 or O2). However, the H2O molecules and OH- groups are relatively small in volume and thus can migrate within mineral structures with given anion porosities easier than the CO2 and O2. As a result, the rates of oxygen diffusion in minerals under hydrothermal conditions are greater than those under anhydrous conditions. The Arrhenius parameters for oxygen diffusion in about 130 minerals have been estimated for the anhydrous and hydrothermal conditions, respectively. The empirical results on oxygen diffusivity are internally consistent for the minerals of geochemical interest and thus can be applicable to oxygen isotope geospeedometry during cooling of high-temperature mineral assemblages.
TL;DR: In this article, the β-SiC nanorods with amorphous SiO2 wrapping layers were obtained by carboreduction at 1650 °C for 1.5 h, and at the end of one.5h the temperature was steeply raised to 1800 °C and held for 30 min; they are typically up to 20 µm in length.
Abstract: Preparation of β–SiC nanorods with and without amorphous SiO2 wrapping layers was achieved by carbothermal reduction of sol-gel derived silica xerogels containing carbon nanoparticles. The β–SiC nanorods with amorphous SiO2 wrapping layers were obtained by carboreduction at 1650 °C for 1.5 h, and at the end of 1.5 h the temperature was steeply raised to 1800 °C and held for 30 min; they are typically up to 20 µm in length. The diameters of the center thinner β–SiC nanorods within the amorphous SiO2 wrapping layers are in the range 10–30 nm, while the outer diameters of the corresponding amorphous SiO2 wrapping layers are between 20 and 70 nm. The β–SiC nanorods without amorphous SiO2 wrapping layers were produced by carbothermal reduction only at 1650 °C for 2.5 h, and their diameters are in agreement with those of the center thinner β–SiC nanorods wrapped in amorphous SiO2 layers. Large quantities of SiC rod nuclei and the nanometer-sized nucleus sites on carbon nanoparticles are both favorable to the formation of much thinner β–SiC nanorods. The formation of the outer amorphous SiO2 wrapping layer is from the combination reaction of decomposed SiO vapor and O2.
TL;DR: In this article, the photoluminescence spectra and quenching concentration of nanocrystalline Y2SiO5:Eu and normal Y2 SiO5 :Eu synthesized by high-sintering method were measured and compared.
TL;DR: In this paper, the highly c-axis oriented ZnO films were deposited on Si substrates with Zn buffer layers, and the intense cathodoluminescence, including UV, blue, and green emissions, was observed in these films at room temperature.
TL;DR: In this paper, the Raman spectra of nanometer Mn3O4 with different sizes at room temperature were reported and the result of experiment shows that the shifting and broadening of Raman spectrum was mainly due to grain size effect.
TL;DR: In this paper, a bimodal Weibull distribution statistical model of strain-rate dependence of fibres and a test method of determining mechanical properties and Weibbullion parameters of fibers from fibre bundle test was used to study the rate dependence of kevlar49 fibre strength.
Abstract: The stress–strain curves of kevlar49 aramid fibre bundles under both quasi-static loading and high rate loading were obtained. The strain rate ranges from 10−4/s to 103/s. Based on a bimodal Weibull distribution statistical model of strain-rate dependence of fibres and a test method of determining mechanical properties and Weibull parameters of fibres from fibre bundle test, the rate dependence of kevlar49 fibre strength is studied. Experimental results show that kevlar49 fibre has sensitivity to strain rate. The peculiar `skin-core' structure of kevlar aramid fibre and experimental Weibull data confirm that there are two types of fracture mode in kevlar fibre and the application of bimodal Weibull distribution is correct. Consistence of simulated and experimental results indicates that the model is valid to explain the mechanical behaviour of kevlar49 fibre and the test method is feasible and reliable.
TL;DR: Comparison of the structure of the N15 TCR-VSV8-H-2Kb complex revealed a common docking mode, regardless of TCR specificity or species origin, in which the TCR variable Valpha domain overlie the MHC alpha2 helix and the Vbeta domain overlies the M HC alpha1 helix.
TL;DR: The present results suggest that the ability to respond to boundaries in a cue-invariant manner originates at relatively early stages of cortical processing.
Abstract: The responses of neurons in areas V1 (17) and V2 (18) of anesthetized and paralyzed rhesus monkeys and cats were recorded while presenting a set of computer-generated visual stimuli that varied in pattern, texture, luminance, and contrast. We find that a class of extrastriate cortical cells in cats and monkeys can signal the presence of boundaries regardless of the cue or cues that define the boundaries. These cue-invariant (CI) cells were rare in area V1 but easily found in V2. CI cortical cells responded more strongly to more salient boundaries regardless of the cue defining the boundaries. Many CI cortical cells responded to illusory contours and exhibited the same degree of orientation and direction selectivity when tested with boundaries defined by different cues. These cells have significant computational power inherent in their receptive fields since they were able to generalize across stimuli and integrate multiple cues simultaneously in order to signal boundaries. Cells in higher order cortical areas such as MT (Albright, 1992), MST (Geesaman & Anderson, 1996), and IT (Sary et al., 1993) have previously been reported to respond in a cue invariant fashion. The present results suggest that the ability to respond to boundaries in a cue-invariant manner originates at relatively early stages of cortical processing.
TL;DR: Diamond powder was synthesized through a metallic reduction-pyrolysis-catalysis route with the reaction of carbon tetrachloride and sodium at 700 degreesC, in which the sodium was used as reductant and flux.
Abstract: Diamond powder was synthesized through a metallic reduction-pyrolysis-catalysis route with the reaction of carbon tetrachloride and sodium at 700°C, in which the sodium was used as reductant and flux. This temperature is much lower than that of traditional methods. The x-ray powder diffraction patterns showed three strong peaks of diamond. The Raman spectrum showed a sharp peak at 1332 inverse centimeters, which is characteristic of diamond. Although the yield was only 2 percent, this method is a simple means of forming diamond.
TL;DR: It seems that, when lowering the pH value, the polarization capability of the Glu143 carboxylate group to the catalytic water molecule become weaker, which might be the structural reason why the snake venom metalloproteinases are inactive or have a low activity under acidic conditions.
TL;DR: In this paper, an upper bound for the spectral radius of Laplacian matrix of a graph in terms of a 2-degree of a vertex is presented. But this upper bound is not applicable to the case of graphs.
TL;DR: In this paper, the transmission characteristics of phase-shifted long period gratings (LPGs) are examined theoretically by a combination of coupled-mode theory and transfer matrix formulation, and it is shown that the transmission spectrum of such a grating can be significantly controlled by the phase shift which allows the shape of the spectrum to be tailored to meet the requirements of many kinds of gain flattening.
Abstract: The transmission characteristics of phase-shifted long period gratings (LPGs) are examined theoretically by a combination of coupled-mode theory and transfer matrix formulation. It is shown that the transmission spectrum of such a grating can be significantly controlled by the phase shift which allows the shape of the spectrum to be tailored to meet the requirements of many kinds of gain flattening. By choosing the phase shift and the index change appropriately, a phase-shifted LPG is designed to flatten the spectrum of an Er:silica superfluorescent fibre source.
TL;DR: A predictive model has been developed by using 125 isomers in alkanes as the training set, and its performance was certified by employing 25 alkanes chosen randomly as the test set from a total of 150 alkane compounds; excellent predicted results were obtained.
Abstract: Models that estimate and predict the normal boiling point (NBP) of alkanes based on a molecular distance-edge (MDE) vector, λ, have been developed by using multiple linear regression (MLR) methods. The structures of the examined compounds are selectively described by an MDE vector structure descriptor, a novel molecular distance-edge vector recently developed in our laboratory. MLR was used to develop a linear model containing ten variables with a high precision root mean squares error (RMS = 4.985K) and a good correlation with the correlation coefficient (R = 0.9948). In addition, a predictive model has been developed by using 125 isomers in alkanes as the training set, and its performance was certified by employing 25 alkanes chosen randomly as the test set from a total of 150 alkane compounds; excellent predicted results were obtained with the RMS and R values found between the calculated value and observed NBP being RMS = 4.486K and R = 0.9945.
TL;DR: In this paper, the authors define affine Weyl groups and prove an analogue of Chevalley Theorem for their invariants, and construct a Frobenius structure on their orbit spaces.
Abstract: We define certain extensions of affine Weyl groups (distinct from these considered by K. Saito [S1] in the theory of extended affine root systems), prove an analogue of Chevalley Theorem for their invariants, and construct a Frobenius structure on their orbit spaces. This produces solutions F(t1, ..., tn) of WDVV equations of associativity polynomial in t1, ..., tn-1, exp tn.
TL;DR: In this paper, a solvothermal elemental reaction to nanocrystalline zinc selenide was proposed and the coordinating ability of the solvent was found to play an important role on the nucleation and growth of the ZnSe.
Abstract: A solvothermal elemental reaction to nanocrystalline zinc selenide was proposed. The coordinating ability of the solvent was found to play an important role on the nucleation and growth of the nanocrystalline ZnSe.