Showing papers by "University of Science and Technology of China published in 1999"

The Ski oncoprotein interacts with the Smad proteins to repress TGFbeta signaling.

Abstract: Smad proteins are critical signal transducers downstream of the receptors of the transforming growth factor-β (TGFβ) superfamily. On phosphorylation and activation by the active TGFβ receptor complex, Smad2 and Smad3 form hetero-oligomers with Smad4 and translocate into the nucleus, where they interact with different cellular partners, bind to DNA, regulate transcription of various downstream response genes, and cross-talk with other signaling pathways. Here we show that a nuclear oncoprotein, Ski, can interact directly with Smad2, Smad3, and Smad4 on a TGFβ-responsive promoter element and repress their abilities to activate transcription through recruitment of the nuclear transcriptional corepressor N-CoR and possibly its associated histone deacetylase complex. Overexpression of Ski in a TGFβ-responsive cell line renders it resistant to TGFβ-induced growth inhibition and defective in activation of JunB expression. This ability to overcome TGFβ-induced growth arrest may be responsible for the transforming activity of Ski in human and avian cancer cells. Our studies suggest a new paradigm for inactivation of the Smad proteins by an oncoprotein through transcriptional repression.

Oxygen isotope fractionation in carbonate and sulfate minerals

Abstract: Oxygen isotope fractionations involving carbonates and sulfates have been controversial for a long time. There are important unresolved conflicts among the results of theoretical calculations, experimental measurements and empirical estimates. In this paper, the increment method is adapted to systematically evaluate oxygen isotope fractionations in the carbonates and sulfates. The following sequence of 18-enrichment in carbonate minerals is obtained: siderite > ankerite > magnesite ≥ dolomite > calcite > aragonite > strontianite > cerussite ≥ witherite. The sequence of 18O-enrichment in sulfate minerals is predicted as follows: anhydrite > celestite > barite > anglesite. The internally consistent fractionation factors for the systems carbonate-water and sulfate-water are acquired for a temperature range of 0 to 1200°C, which are in fair agreement with existing experimental and/or empirical data. The present calculations suggest that dolomite should behave isotopically like calcite; equilibrium fractionation between dolomite and calcite is only 0.56‰ at 25°C. Aragonite is predicted to be significantly depleted in 18O relative to calcite; equilibrium fractionation between calcite and aragonite is 4.47‰ at 25°C. It is possible that polymorphic transition from aragonite to calcite could proceed through an essentially intact oxygen structure without isotopic resetting. As a result, the temperature dependence of oxygen isotope partitioning in aragonite could be conveyed to calcite. Oxygen isotope inheritance in calcite formation by the polymorphic transition may be of critical importance in attempts to resolve dilemma involving fractionations in aragonite-calcite-dolomite-water systems.

Solvothermal Elemental Direct Reaction to CdE (E = S, Se, Te) Semiconductor Nanorod

Abstract: The solvothermal reaction of sulfur, selenium, or tellurium with cadmium metal powder in different organic solvents in the temperature range 120−200 °C was investigated systematically to prepare ca...

A Novel Ultraviolet Irradiation Technique for Shape-Controlled Synthesis of Gold Nanoparticles at Room Temperature

Abstract: Shape-controlled gold nanoparticles were synthesized using a novel ultraviolet irradiation technique at room temperature. The very slow ultraviolet irradiation photoreduction process may favor the formation of the shaped gold nanoparticles. It was found that not only the concentration of gold cations and the irradiation time but also the concentration and the species of polymer capping materials play important roles in the morphology control of the gold nanoparticles.

Atmospheric Water Vapor Flux and Its Association with Rainfall over China in Summer

Abstract: The summer moisture transport by the large-scale circulation over China has been investigated using ECMWF–WMO twice-daily analyses for the period 1980–96. The horizontal flux of atmospheric water vapor and its divergence has been calculated over two target regions, namely, southeast China (25°–35°N, 110°–120°E) and northeast China (40°–50°N, 120°–130°E). The time-averaged fluxes show the southeastern Asian and Indian monsoon circulations bringing abundant moisture from the South China Sea and the Bay of Bengal, respectively, to southeast China while the midlatitude westerlies dominate the moisture transport over northeast China. The association between the interannual variations of moisture flux and rainfall over China has been examined. The comparison of the fluxes for wet and dry years over the southeast showed there to be, for the former, much stronger moisture transport by the southeastern Asian monsoon through the southern boundary but little change associated with transport by the Indian mo...

Light-Scattering Study of Coil-to-Globule Transition of a Poly(N-isopropylacrylamide) Chain in Deuterated Water

Abstract: Using a nearly monodisperse (Mw/Mn < 1.1) high molar mass (1.3 × 107 g/mol) poly(N-isopropylacrylamide) (PNIPAM), we studied the conformation change of individual PNIPAM chains between an extended random coil and a fully collapsed thermodynamically stable single chain globule in an extremely dilute D2O solution (∼6.3 × 10-7 g/mL) by a combination of static and dynamic laser light scattering (LLS). In comparison with PNIPAM in H2O, the ϑ-temperature of PNIPAM in D2O is slightly higher, shifting from 30.6 to 32.1 °C. Moreover, the coil-to-globule transition in D2O showed no molten globular state, different from PNIPAM in H2O. However, the molten globular state exists in the globule-to-coil transition in D2O. The size of the PNIPAM chains near the ϑ-temperature in the globule-to-coil transition is smaller than that in the coil-to-globule transition; i.e., there exists a hysteresis, similar to PNIPAM in H2O. The hysteresis can be attributed to the intrachain interaction formed in the globular state. Our resul...

Formation of silver nanowires by a novel solid-liquid phase arc discharge method

Abstract: A novel technique for fabrication of silver nanowires was successfully developed via a so-called solid−liquid phase arc discharge method (SLPAD). It was found that the aging time following the SLPAD method has a significant effect on the formation and growth of silver nanowires. The possible formation process of the silver nanowires was proposed. The present technique may be extended for preparation of other metal nanowires.

Sm/Nd, Rb/Sr, and40Ar/39Ar Isotopic Systematics of the Ultrahigh-Pressure Metamorphic Rocks in the Dabie-Sulu Belt, Central China: A Retrospective View

Abstract: Because of a complicated metamorphic history, the isotopic systematics of the ultrahigh-pressure (UHP) metamorphic rocks in the Dabie-Sulu belt, east China, appear to be rather different from what were expected. Depending on the degree of retrograde metamorphism and on the retentivity of isotopes, the radiogenic isotopic systematics in the UHP metamorphic rocks yielded a wide range of radiometric ages. Some of these ages are geologically meaningful, but others may not be. In some fine-grained UHP metamorphic rocks, Sm/Nd isotopic systematics appear to be in equilibrium among the UHP phases, showing the best estimate for the age of peak metamorphism at 226 ± 3 Ma. On the other hand, retrograde overprinting often makes the interpretation of isotopic data more difficult. It is common to find that the Sm/Nd and Rb/Sr isotopic systematics among the UHP phases and retrograde phases are not in equilibrium. Regression of isotopic data involving both UHP and retrograde minerals in isotopic correlation diagrams oft...

Thermally Sensitive and Biocompatible Poly(N-vinylcaprolactam): Synthesis and Characterization of High Molar Mass Linear Chains

Abstract: High molar mass poly(N-vinylcaprolactam) (PVCa) was synthesized by free-radical bulk polymerization. Four narrowly distributed fractions of PVCa were obtained in the tetrahydrofuran/n-hexane mixture. A combination of static and dynamic laser light scattering led to a scaling between the translational diffusion coefficient (D) and molar mass (M), D (cm2/s) = 8.47 × 10-5Mw-0.503, with which we transferred the translational diffusion coefficient distribution of each fraction into a corresponding molar mass distribution. We also established a scaling between the weight average molar mass (Mw) and the radius of gyration (〈Rg〉), 〈Rg〉 (nm) = 2.94 × 10-2Mw0.54, for PVCa in water at 25 °C. Moreover, we found a novel way to estimate the ϑ-temperature (∼29.5 °C) from the temperature and concentration dependence of the hydrodynamic radius (〈Rh〉). The lower critical solution temperature (LCST, ∼31.5 °C) of linear PVCa chains in water determined from the variations of both 〈Rh〉 and scattering intensity is close to the ...

Uniform connectedness and classical Gestalt principles of perceptual grouping.

Abstract: We assessed whether uniform connectedness (UC; Palmer & Rock, 1994) operates prior to effects reflecting classical principles of grouping: proximity and similarity. In Experiments 1 and 2, reaction times to discriminate global letters (H vs. E), made up of small circles, were recorded. The small circles were respectively grouped by proximity, similarity of shapes, and by UC. The discrimination of stimuli grouped by similarity was slower than those grouped by proximity, and it was speeded up by the addition of UC. However, the discrimination of stimuli grouped by proxhnity was unaffected by connecting the local elements. In Experiment 3, similar results occurred in a task requiring discrimination of the orientation of grouped elements, except that the discrimination of stimuli grouped by UC was faster than that of those grouped by weak proximity. Experiment 4 further showed that subjects could respond to letters composed of discriminably separate local elements as fast as to those without separated local elements. The results suggest that grouping by similarity of shapes is perceived slower than grouping by UC, but grouping by proximity can be as fast and efficient as that by UC.

Self-similar Solution of Optically Thick Advection-dominated Flows

Abstract: The photons released by the viscosity process in a disk with accretion rate exceeding the Eddington critical value will be trapped and restored as entropy in the accreting gas rather than being radiated from the disk surface, since the advection cooling dominates the diffusion cooling in such a flow. In this paper a self-similar solution of optically thick advection-dominated flow has been obtained. This kind of flow shows some interesting characteristics that differ from both the optically thin advection-dominated disk and the standard disk. Such a flow is thermally stable. The Bernoulli number is not positive in a wide range of parameters unless the viscosity α is extremely small. The shape always stays slim and is independent of the accretion rate (H/r≈1/√5). The gas rotates with sub-Keplerian angular velocity Ω≈ΩK/√5 (for smaller viscosity). The luminosity of the disk weakly depends on the accretion rate, and the maximum luminosity is about 4.0 × 1037 (ergs s-1) (M/M☉) (less than the Eddington luminosity), although the accretion rate is super-Eddington. This provides a method for estimating the mass of a black hole. The validity of this solution has been tested and found to be suitable in most of the accretion disk (within the photon trapping radius). Its potential applications to the saturated accreting systems are pointed out.

Light Scattering Study of the Formation and Structure of Partially Hydrolyzed Poly(acrylamide)/Calcium(II) Complexes

Abstract: The Ca2+ concentration and hydrolysis degree [−COO-] dependence of the self-complexation of partially hydrolyzed poly(acrylamide) (HPAM) chains in CaCl2 aqueous solution was systematically investigated by a combination of static and dynamic laser light scattering. We have, for the first time, revealed a transition between the intrachain and interchain complexations. For each given HPAM sample, there exists a critical Ca2+ concentration ([Ca2+]agg) at which the interchain HPAM complexation becomes dominant. [Ca2+]agg is related to [−COO-] by [Ca2+]agg = 7.46 × 10-9 [−COO-]-1.4, indicating that the complexation is not stoichiomeric and many Ca2+ ions are free in water. We also found that even at [Ca2+] > [Ca2+]agg, the complexation at the initial stage was mainly an intrachain process, but gradually evolved into an interchain aggregation. The length of the initial stage increases as [−COO-] and [Ca2+] decrease. Our results showed that in the complexation process, the weight average molecular weight (Mw) of ...

Fast accent identification and accented speech recognition

Abstract: The performance of speech recognition systems degrades when speaker accent is different from that in the training set. Accent-independent or accent-dependent recognition both require collection of more training data. In this paper, we propose a faster accent classification approach using phoneme-class models. We also present our findings in acoustic features sensitive to a Cantonese accent, and possibly other Asian language accents. In addition, we show how we can rapidly transform a native accent pronunciation dictionary to that for accented speech by simply using knowledge of the native language of the foreign speaker. The use of this accent-adapted dictionary reduces recognition error rate by 13.5%, similar to the results obtained from a longer, data-driven process.

Novel Prediction for the Driving Force and Guest Orientation in the Complexation of α- and β-Cyclodextrin with Benzene Derivatives

Abstract: Taking the possibility of different inclusion orientations into consideration, a nonlinear free energy relationship model has been established by means of a genetic algorithm for the molecular recognition of α- and β-CD with mono- and 1,4-disubstituted benzenes. The association constants (Ka) for the inclusion complexation of α- and β-cyclodextrin with a number of benzene derivatives were evaluated by the model from the substituent molar refraction Rm, hydrophobic constant π, and Hammett constant σ, which respectively reflect the volume, hydrophobicity, and electronic property of the substituents in the guest compounds. The Ka values calculated by the model are quite close to those determined experimentally. It suggested that the van der Waals force, hydrophobic interactions, and electronic effects comprise the main driving forces for CD molecular recognition. Furthermore, van der Waals force plays a dominant role in α-CD complexation; on the other hand, van der Waals force and hydrophobic interactions pl...

Structure and properties of impact copolymer polypropylene. I. Chain structure

Abstract: In this work, impact copolymer polypropylene (ICPP) was fractionated into 4 fractions. ICPP and the 4 fractions were studied using Fourier transform infrared and 13C nuclear magnetic resonance analysis. The results demonstrate that fraction A is ethylene–propylene rubber, fraction B is ethylene–propylene (EP) segmented copolymer, fraction C is ethylene–propylene block copolymer, and fraction D is polypropylene with a few ethylene monomers in the chain. The differences in properties between different impact copolymer polypropylenes should be due to their fractions' differences in composition and chain sequence structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 93–101, 1999

Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XV. Long-Term Optical Monitoring of NGC 5548

Abstract: We present the results of 3 yr of ground-based observations of the Seyfert 1 galaxy NGC 5548, which, combined with previously reported data, yield optical continuum and broad-line Hβ light curves for a total of 8 yr. The light curves consist of over 800 points, with a typical spacing of a few days between observations. During this 8 yr period, the nuclear continuum has varied by more than a factor of 7, and the Hβ emission line has varied by a factor of nearly 6. The Hβ emission line responds to continuum variations with a time delay or lag of ~10-20 days, the precise value varying somewhat from year to year. We find some indications that the lag varies with continuum flux in the sense that the lag is larger when the source is brighter.

Parallel and competitive processes in hierarchical analysis: perceptual grouping and encoding of closure.

Abstract: The role of perceptual grouping and the encoding of closure of local elements in the processing of hierarchical patterns was studied. Experiments 1 and 2 showed a global advantage over the local level for 2 tasks involving the discrimination of orientation and closure, but there was a local advantage for the closure discrimination task relative to the orientation discrimination task. Experiment 3 showed a local precedence effect for the closure discrimination task when local element grouping was weakened by embedding the stimuli from Experiment 1 in a background made up of cross patterns. Experiments 4A and 4B found that dissimilarity of closure between the local elements of hierarchical stimuli and the background figures could facilitate the grouping of closed local elements and enhanced the perception of global structure. Experiment 5 showed that the advantage for detecting the closure of local elements in hierarchical analysis also held under divided- and selective-attention conditions. Results are consistent with the idea that grouping between local elements takes place in parallel and competes with the computation of closure of local elements in determining the selection between global and local levels of hierarchical patterns for response.

Preparation and gas sensitivity properties of znfe2o4 semiconductors

Abstract: This paper reports the preparation and gas-sensing properties of ZnFe 2 O 4 . Raw powders of ZnFe 2 O 4 were obtained by chemical coprecipitation. Effects of the calcining temperature on the phase constituents and microstructure are characterized by TG-DTA and XRD. The conductance-temperature, gas-sensing properties of ZnFe 2 O 4 were investigated. The results demonstrated that ZnFe 2 O 4 can be used as a new type of gas-sensing material which has a high sensitivity and good selectivity to C 2 H 5 OH.