Showing papers by "Sun Yat-sen University published in 1998"
TL;DR: In this paper, the self-assembly of AgX (X = NO3-, ClO4-) with 2,4-bipyridine (2,4‘-bpy) was studied.
Abstract: Two compounds, [Ag(2,4‘-bpy)]NO3 (1) and [Ag(2,4‘-bpy)]ClO4 (2), were obtained from self-assembly of AgX (X = NO3-, ClO4-) with 2,4‘-bipyridine (2,4‘-bpy). 1 crystallizes in the orthorhombic space group Pbca, with a = 11.2884(7) A, b = 11.3981(10) A, c = 16.5299(13) A, and Z = 8, while 2 crystallizes in the monoclinic space group P21/c, with a = 10.6361(4) A, b = 9.9896(4) A, c = 11.2661(6) A, β = 98.527(4)°, and Z = 4. Both complexes consist of helical [Ag(2,4‘-bpy)]∞ chains that are surrounded by nitrate or perchlorate counterions. Adjacent helical chains are racemic. The AgI atom is linked to two nitrogen atoms of the 2-pyridyl and 4‘-pyridyl groups from two different 2,4‘-bpy ligands as well as to the oxygen atom of the counterion. In 1, another oxygen atom of the counterion is weakly coordinated to the AgI atom of an adjacent chain, thus bridging the helical chains into a wavy 2-D network structure, whereas in 2, adjacent helical chains are linked by the weak ligand-unsupported metal−metal interactio...
183 citations
TL;DR: It is shown that Aβ-induced toxicity of cultured fetal rat cortical neurons is associated with internucleosomal DNA fragmentation beginning just 6 h after neurons are exposed to Aβ, and alterations in NF-κB-directed gene expression may contribute to both the neurodegeneration and inflammatory response which occur in AD.
181 citations
TL;DR: In this paper, the use of 10 mmol litre −1 glutathione and 100 mmollitre − 1 citric acid was found to give good control of the browning of litchi fruit and 80-85% inhibition of PPO observed.
110 citations
TL;DR: The high litter production and rapid turnover of leaf litter indicated the importance of this mangrove swamp in supplying nutrients and organic matter to the estuarine ecosystems.
103 citations
TL;DR: The rate of reinfection and ulcer recurrence in Chinese patients cured of H. pylori and duodenal ulcer disease and random amplification of polymorphic DNA fingerprinting was used to compare isolates before and after therapy.
99 citations
TL;DR: TLC determinations showed that AFB1 at an initial concentration of 16 microM was completely detoxified (100%) by the fungal multienzyme, and the infrared spectrum suggests that the multien enzyme is responsible for opening the difuran ring of AFB1.
93 citations
TL;DR: In this article, a reproducible positive temperature coefficient (PTC) composite with acceptable PTC intensity, effect of conductive filler content, processing conditions and filler treatment with nitric acid, and titanate coupling agents was described and discussed.
Abstract: Polymer-based positive temperature coefficient (PTC) composites are of special interest because they have great potential in temperature-sensitive devices. To obtain a reproducible PTC composite with acceptable PTC intensity, effect of conductive filler content, processing conditions and filler treatment with nitric acid, and titanate coupling agents on room temperature resistivity and PTC intensity of carbon-black-filled low-density polyethylene composites have been described and discussed herein. The results showed that filler arrangement is a key factor influencing the ultimate material performance, which can be tailored in various ways. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 559–566, 1998
87 citations
TL;DR: Titanocene complexes based on an amido-fluorenyl ligand bridged by a dimethylsilylene group, such as (η1:η5-C13H8SiMe2NCMe3)TiCl2 (3) as discussed by the authors, have been synthesized.
Abstract: Titanocene complexes based on an amido-fluorenyl ligand bridged by a dimethylsilylene group, (η1:η5-C13H8SiMe2NCMe3)TiCl2 (3) and (η1:η5-C13H8SiMe2NCMe3)TiMe2 (5), have been synthesized. Reaction of 5 with 1 equiv of [Ph3C][B(C6F5)4] (2) was almost quantitative to give the “cationic” compound [(η1:η5-C13H8SiMe2NCMe3)TiMe]+[B(C6F5)4]- (1), as identified on the basis of elemental analyses and spectroscopic properties. The “cation” 1 was highly active and stereoselective in the copolymerization of ethylene (E) and styrene (S), depending upon the polymerization conditions, to produce predominantly a new microstructural E−S copolymer (together with some polyethylene homopolymer) with an activity of (0.65−1.58) × 105 g of bulk polymer/(mol of Ti·mol of total monomers·h). As thoroughly characterized by solvent extraction, GPC, 13C NMR, DSC, and DMA, the E−S copolymer obtained by catalyst 1 proved to be a perfectly alternating copolymer with well-defined isotactic polystyrene structure, together with a single gla...
87 citations
TL;DR: Wang et al. as mentioned in this paper investigated the possible contamination of teas with the trace metals: Al, Cu and Zn, which may be due to the lower soil pH in these areas.
Abstract: The present project aims to investigate the possible contamination of teas with the trace metals: Al, Cu and Zn. Tea bushes sampled from two tea plantations in the northern part of Guangdong Province accumulated higher concentrations of Cu and Zn in young leaves, and of Al in old leaves. The analysis of the three metals in tea produced in different provinces indicated higher Al levels in those obtained from Guangdong and Yunnan Provinces, which may be due to the lower soil pH in these areas. Green tea had the lowest Al concentration among the four types of tea studied, as only the bud and two young leaves are used, whereas older leaves are used for other types of tea (black, Oolong and Puerh tea). The transfer of Al, Cu and Zn from soil to different parts of tea bushes was low in general, except for Zn at Lechang tea plantation which next to a Pb/Zn mine, where a higher transfer was observed from young leaves to tea products, indicating possible metal contamination during tea processing. However, low concentrations of Cu and Zn (less than 0.07 mg Cu L-1 and 0.17 mg Zn L-1), and moderate amounts of Al (2.1-2.5 mg L-1) were obtained in the tea liquor (1% hot water extracts).
84 citations
TL;DR: Comparisons with results of phylogenetic analyses of other genera suggested that (1) the floristic connection between eastern North America and western North America may be stronger than previously thought; and (2) the biogeographic patterns in the Northern Hemisphere are complex.
Abstract: Aralia sect. Aralia (Araliaceae) consists of approximately eight species disjunctly distributed in Asia and North America. Phylogenetic and biogeographic analyses were conducted using sequences of the internal transcribed spacer regions of the nuclear ribosomal DNA. Aralia racemosa from eastern North America was sister to A. californica from western North America. Aralia cordata from eastern Asia did not form a species-pair relationship with the eastern North American A. racemosa. The two subspecies of A. racemosa formed a monophyletic group. Biogeographic analyses showed a close area relationship between eastern North America and western North America. The Himalayas were cladistically basal and eastern Asia was placed between the Himalayas and North America. The biogeographic analysis supported the origin of the eastern Asian and eastern North American disjunct pattern in Aralia sect. Aralia via the Bering land bridges. Comparisons with results of phylogenetic analyses of other genera suggested that (1) the floristic connection between eastern North America and western North America may be stronger than previously thought; and (2) the biogeographic patterns in the Northern Hemisphere are complex. Furthermore, a lack of correlation between sequence divergence values and phylogenetic positions was observed, suggesting the importance of a phylogenetic framework in biogeographic analyses.
82 citations
TL;DR: In this paper, the authors applied the linear water wave theory and the eigenfunction expansion method to the wave reflection by a vertical wall with a horizontal submerged porous plate, and the numerical results concerning the effects of the dimensionless plate length, the relative water depth and the porous effect parameter of the plate on the wave loads on the plate and the wave height near the wall as well as the reflection coefficient, are discussed.
TL;DR: In this article, the Newtonian gravitational constant was determined by means of a high-Q torsion pendulum and the time-of-swing method, in which the period of the pendulum is altered by the presence of two 6.25-kg stainless steel cylinders.
Abstract: The Newtonian gravitational constant G is determined by means of a high-Q torsion pendulum and the time-of-swing method, in which the period of the pendulum is altered by the presence of two 6.25-kg stainless steel cylinders. The nonlinear fitting method is used to extract the frequencies from the angle-time data of the pendulum. The resulting value of G is $(6.6699\ifmmode\pm\else\textpm\fi{}0.0007)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}{\mathrm{m}}^{3}{\mathrm{}\mathrm{kg}}^{\mathrm{\ensuremath{-}}1}{\mathrm{}\mathrm{s}}^{\mathrm{\ensuremath{-}}2}.$
TL;DR: Results indicate that leaves of Camellia ptilophylla exhibit unusual purine alkaloid metabolism as they have the capacity to synthesize theobromine from adenine nucleotides, but they lack adequate methyltransferase activity to convert of theobomine to caffeine in detectable quantities, and the leaves have a capacity to convert xanthine to theobroma, probably via 3-methylxanthine.
Abstract: The biosynthesis and metabolism of purine alkaloids in leaves ofCamellia ptilophylla (cocoa tea), a new tea resource in China, have been investigated. The major purine alkaloid was theobromine, with theophylline also being present as a minor component. Caffeine was not accumulated in detectable quantities. Theobromine was synthesized from [8-14C] adenine and the rate of its biosynthesis in the segments from young and mature leaves from flush shoots was approximately 10 times higher than that from aged leaves from 1-year old shoots. Neither cellfree extracts nor segments fromC. ptilophylla leaves could convert theobromine to caffeine. A large quantity of [2-14C] xanthine taken up by the leaf segments was degraded to14CO2 via the conventional purine catabolic pathway that includes allantoin as an intermediate. However, small amounts of [2-14C] xanthine were also converted to theobromine. Considerable amounts of [8-14C] caffeine exogenously supplied to the leaf segments ofC. ptilophylla was changed to theobromine. These results indicate that leaves ofC. ptilophylla exhibit unusual purine alkaloid metabolism as i) they have the capacity to synthesize theobromine from adenine nucleotides, but they lack adequate methyltransferase activity to convert of theobromine to caffeine in detectable quantities, ii) the leaves have a capacity to convert xanthine to theobromine, probably via 3-methylxanthine.
TL;DR: In this paper, the impact strength and flexural strength of poly(ethylene terephthalate) (PET), polyamide-6 (PA-6), and a reactive compatibilizer (low molecular weight bisphenol-A epoxy resin) were prepared with the following E-44 weight percent concentrations: 0, 0.6, 1, 3, 5, and 10.
Abstract: Polymer blends incorporating poly (ethylene terephthalate) (PET), polyamide-6 (PA-6), and a reactive compatibilizer (low molecular weight bisphenol-A epoxy resin—E-44) were prepared with the following E-44 weight percent concentrations: 0, 0.3, 0.6, 1, 3, 5, and 10. The samples was studied by a scanning electron microscope (SEM), a polarizing microscope (PLM), dynamic mechanical thermal analysis (DMTA), wide-angle X-ray diffraction (WAXD), a differential scanning calorimeter (DSC), infrared spectroscopy (IR), and mechanical testing. SEM and PLM showed noticeable changes in both the amorphous region and the crystalline region of the blends. The changes indicated better compatibility between the dispersed phase (PA-6) and the matrix (PET), which was further confirmed by the DMTA test. The WAXD showed that PET and PA-6 crystallized separately and no cocrystallite was found. The melting and crystallization data, obtained by DSC, suggested that the crystallization of the blend was blocked, although the hindered mechanism for the effect of E-44 on PET was different from that on PA-6. The notched impact strength and flexural strength of the PET/PA-6 blends were significantly improved when the content of E-44 was 5 wt % (improved about 500 and 400%, respectively). IR was used to study the reaction among E-44, PET, and PA-6. The result indicated that the grafting reaction and the crosslinking reaction occurred during melt blending. The obvious increase of mechanical properties and the reinforcing and toughening effect were attributed to the formation of the crosslinking net in the blend. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1505–1515, 1998
TL;DR: It is inferred that the binding of [Co(phen)3]3 to DNA may be not by classical intercalation, as shown in the absorption spectroscopic studies and the viscosity experiment.
TL;DR: In this article, a planar ligand was synthesized for calf thymus DNA using various photophysical methods and the binding of the resulting ligands to calf thyus DNA was investigated.
TL;DR: The phylogeny of Hamamelidaceae was constructed based on sequences of the internal transcribed spacers (ITS) and the 5.8S coding region of nuclear ribosomal DNA and the monophyly of both the Altingioideae and the Hamamelidoideae was strongly supported.
TL;DR: The reaction of pentamethylcyclopentadienyltris((trimethylsilyl)methyl)titanium (Cp*Ti(CH2SiMe3)3) with 1 equiv of B(C6F5)3 was almost quantitative to give the “cationic” compound [Cp * Ti(CH 2SiMe 3)2] as mentioned in this paper.
Abstract: The reaction of pentamethylcyclopentadienyltris((trimethylsilyl)methyl)titanium (Cp*Ti(CH2SiMe3)3) with 1 equiv of B(C6F5)3 was almost quantitative to give the “cationic” compound [Cp*Ti(CH2SiMe3)2...
TL;DR: An experiment on the pump-power density dependence of Rh emission spectra shows that the lasing threshold of a Rh6G solution embedded with TiO(2) nanoparticle fractal aggregates is significantly reduced compared with that of a neat dye solution.
Abstract: The spectral and temporal emission properties of a Rhodamine (Rh) dye solution embedded with nanoparticle fractal aggregates are studied. An experiment on the pump-power density dependence of Rh emission spectra shows that the lasing threshold of a Rh6G solution embedded with TiO2 nanoparticle fractal aggregates is significantly reduced compared with that of a neat dye solution. The mechanism of this reduction in lasing threshold is discussed, together with the lasing properties of narrow bandwidth and short duration.
TL;DR: In this paper, six amine-linked thioxanthones were synthesized as water-compatible photoinitiators and identified with FTIR, MS, NMR, and elementary analysis.
Abstract: Six amine-linked thioxanthones, i.e., 2-(2-hydroxy-3-[bis(2-hydroxyethyl)-amino]propoxy)thioxanthone (HAPTX) and its 4-methyl, 1,3-dimethyl, 1,4-dimethyl, 3,4-dimethyl, and 1,3,4-trimethyl substituted derivatives, were synthesized as water-compatible photoinitiators and identified with FTIR, MS, NMR, and elementary analysis. The absorption and fluorescence properties were studied. Their photoinitiating polymerization efficiencies were tested with a recording dilatometer utilizing acrylamide as monomer in aqueous solution. The results show that the six amine-linked thioxanthones can independently initiate acrylamide polymerization efficiently without additional external amines as co-initiators.
TL;DR: In this paper, the chelating properties of N-(o-nitrophenyl)-N′-(methoxycarbonyl)thiourea (H2omt) were investigated through the study of the crystal structures of Cd(Homt)2(bpy), 1, 1, Zn(Homte-phen), 2 and 2 and H 2omt (bpy=2,2′-bipyridine, phen=o-phenanthroline).
TL;DR: In this article, the graft copolymerization of NaCMC with acrylamide (AM) and dimethylaminoethyl methylacrylate (DMAEMA) was conducted in an aqueous solution using ammonium persulfate (APS) and N,N,N′, N′-tetramethylethylene diamine (TMEDA) as the initiator.
Abstract: The graft copolymerization of sodium carboxymethylcellulose (NaCMC) with acrylamide (AM) and dimethylaminoethyl methylacrylate (DMAEMA) was conducted in an aqueous solution using ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylene diamine (TMEDA) as the initiator. The effects of various factors on grafting, such as temperature, pH, initiator concentration, and concentrations of AM, DMAEMA, and NaCMC were studied. The composition and thermal stability of the graft copolymers were characterized by infrared, elemental, and thermogravimetric analysis, and degradation activation energy and kinetic order were calculated. The relationship between its reduced viscosity and pH in aqueous NaCl was also investigated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 879–885, 1998
TL;DR: In this paper, X-ray photoelectron spectroscopy has been employed to measure the atomic ratio of N to C in the carbon nitride films and the effect of N2 partial pressure on the properties of these films is also discussed.
TL;DR: In this article, a greenhouse study was conducted to evaluate the ameliorating role of river sediment, domestic refuse and inorganic fertilizers in the revegetation of the tailings.
TL;DR: In this paper, the Marion's conjecture on the Hausdorff measure of the Koch curve has been proved invalid and the self-similar sets satisfying the open condition have been studied.
Abstract: The self-similar sets satisfying the open condition have been studied. An estimation of fractal, by the definition can only give the upper limit of its Hausdorff measure. So to judge if such an upper limit is its exact value or not is important. A negative criterion has been given. As a consequence, the Marion’s conjecture on the Hausdorff measure of the Koch curve has been proved invalid.
TL;DR: Some relations between the Hausdorff-dimensions and the entropies for expansive homeomorphisms on compact metric spaces are obtained in this paper, where the authors show that these relations can be expressed as follows:
Abstract: Some relations between the Hausdorff-dimensions and the entropies for expansive homeomorphisms on compact metric spaces are obtained.
TL;DR: The TRAP-silver staining method was quick, safe, and effective, and can be used as a routine diagnostic method for the detection of telomerase activity in bone tumours.
Abstract: Telomerase activity has been observed in a high proportion of specimens from a wide variety of human malignant tumours, but not in non-neoplastic tissues. Measurement of telomerase activity is a possible diagnostic maker for malignant tumours. A non-isotopic telomeric repeat amplification protocol (TRAP) silver staining method for the detection of telomerase activity in human bone tumour tissues is described. The TRAP-silver staining method was quick, safe, and effective, and can be used as a routine diagnostic method for the detection of telomerase activity in bone tumours.
TL;DR: The recombinant grass carp GH had immunological and biological activities similar to the native hormone, indicating that the fish signal peptide was correctly processed by the insect cells.
TL;DR: In this paper, the authors applied the elliptic perturbation method to the study of the periodic solutions of strongly quadratic non-linear oscillators of the formx+c1x +c]2x2=ϵf(x,x), in which the Jacobian elliptic functions are employed.
TL;DR: In this paper, the effects of structure relaxation temperature (TR) on the fracture toughness (K1C) of amorphous Fe46Ni32V2Si14B6 alloy ribbon have been measured.
Abstract: The effects of structure relaxation temperature (TR) on the fracture toughness (K1C) of amorphous Fe46Ni32V2Si14B6 alloy ribbon have been measured. The value of K1C is approximately constant at 8 MPa m1/2 when TR<200°C, but it decreases to 2 MPa m1/2 if TR increases from 200°C to 350°C. Associated with the decrease of fracture toughness, the topography of the fractured crack profile transforms from irregular (or fractal) to smooth (or Euclidean). Fractal dimensions (D) of the fracture profiles have also been determined by the perpendicular sectioning method. The results illustrated that, under quasi-two-dimensional brittle fracture conditions, K1C was approximately a linear function of D∗, the square root of the fractal dimension increment. Based on experimental data, the characteristic length, a0, was calculated and is about 20 nm, which is in agreement with the precipitation cluster size of a FeNiB based amorphous alloy which has undergone structure relaxation.