Showing papers by "Sichuan University published in 2002"

Ultrasonic irradiation: A novel approach to prepare conductive polyaniline/nanocrystalline titanium oxide composites

Abstract: A novel approach, i.e., ultrasonic irradiation, was used to prepare polyaniline/nanocrystalline TiO2 composite particles. Polymerization of aniline proceeded under ultrasonic irradiation in the presence of nanocrystalline TiO2. The aggregation of nano TiO2 can be reduced under ultrasonic irradiation, and the nanoparticles can be redispersed in the aqueous solution. The polyaniline deposits on the surface of the nanoparticle, which leads to a core−shell structure. The resulting polyaniline/nano TiO2 composite particles are spherical, and the sizes vary with the content of TiO2. The polyaniline/nano TiO2 composite particles prepared by the conventional stirring method have a “raspberry” aggregate structure, which is different from that obtained through ultrasonic irradiation. The presence of nanocrystalline TiO2 strengthens the UV absorption of polyaniline and leads to a blue shift of the π-polaron absorption of polyaniline. Ultrasound can enhance the doping level. When polyaniline deposits on the surface o...

Transcutaneous electrical nerve stimulation for primary dysmenorrhoea

Abstract: Background Medical therapy for dysmenorrhoea (painful menstrual cramps of the uterus) such as non-steroidal anti-inflammatory drugs or the oral contraceptive pill work by reducing myometrial (uterine muscle) activity. Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacological intervention shown to be effective for pain relief in a variety of conditions. TENS may be able to alter the body's ability to receive and perceive pain signals rather than having a direct effect on uterine contractions. Objectives To determine the effectiveness of high and low-frequency TENS when compared to placebo, no treatment, or medical treatment for primary dysmenorrhoea. Search methods Electronic searches of the Cochrane Menstrual Disorders and Subfertility Group Register of controlled trials, The Cochrane Library (Issue 1, 2009), MEDLINE, EMBASE, CINAHL, and AMED were performed (updated April 2009) to identify relevant randomised controlled trials. The Cochrane Complementary Medicine Field Register of controlled trials (CISCOM) was also searched. Attempts were also made to identify trials from the UK National Research Register, the Clinical Trial Register, and the citation lists of review articles and included trials. Selection criteria The inclusion criteria were: randomised controlled trials (RCTs) of TENS compared to placebo, no treatment, or medical treatment for primary dysmenorrhoea. Exclusion criteria were: mild, infrequent, or secondary dysmenorrhoea and dysmenorrhoea associated with an intrauterine device (IUD). Data collection and analysis Seven RCTs were identified that fulfilled the inclusion criteria for this review. No new studies were identified in the update. Quality assessment and data extraction were performed independently by two review authors. Data unsuitable for meta-analysis were reported as descriptive data and were included for discussion. The outcome measures were pain relief (dichotomous, visual analogue scale, descriptive), adverse effects, use of analgesics additional to treatment, and absence from work or school. Main results Overall, high-frequency TENS was shown to be more effective for pain relief than placebo TENS (OR 7.2, 95% CI 3.1 to 16.5). Low-frequency TENS was found to be no more effective in reducing pain than placebo TENS (OR 1.48, 95% CI 0.43 to 5.08). There were conflicting results regarding whether high-frequency TENS was more effective than low-frequency TENS. Authors' conclusions High-frequency TENS was found to be effective for the treatment of dysmenorrhoea by a number of small trials. The minor adverse effects reported in one trial require further investigation. There is insufficient evidence to determine the effectiveness of low-frequency TENS in reducing dysmenorrhoea.

POLY(p-DIOXANONE) AND ITS COPOLYMERS

Abstract: This paper reviews the synthesis, properties, and applications of biodegradable polymer, poly(p-dioxanone) (PPDO), and its copolymers. Recent progress in ring-opening polymerization of p-dioxanone employing several effective catalysts is described. Properties of PPDO are given. The copolymers based on PPDO are also discussed.

Characterization of surface oxide films on titanium and bioactivity.

Abstract: Biological properties of titanium implant depend on its surface oxide film. In the present study, the surface oxide films on titanium were characterized and the relationship between the characterization and bioactivity of titanium was studied. The surface oxide films on titanium were obtained by heat-treatment in different oxidation atmospheres, such as air, oxygen and water vapor. The bioactivity of heat-treated titanium plates was investigated by immersion test in a supersaturated calcium phosphate solution. The surface roughness, energy morphology, chemical composition and crystal structure were used to characterize the titanium surfaces. The characterization was performed using profilometer, scanning electronic microscopy, ssesile drop method, X-ray photoelectron spectroscopy, common Bragg X-ray diffraction and sample tilting X-ray diffraction. Percentage of surface hydroxyl groups was determined by X-ray photoelectron spectroscopy analysis for titanium plates and density of surface hydroxyl groups was measured by chemical method for titanium powders. The results indicated that heat-treatment uniformly roughened the titanium surface and increased surface energy. After heat-treatment the surface titanium oxide was predominantly rutile TiO2, and crystal planes in the rutile films preferentially orientated in (1 1 0) plane with the highest density of titanium ions. Heat-treatment increased the amount of surface hydroxyl groups on titanium. The different oxidation atmospheres resulted in different percentages of oxygen species in TiO2, in physisorbed water and acidic hydroxyl groups, and in basic hydroxyl groups on the titanium surfaces. The immersion test in the supersaturated calcium phosphate solution showed that apatite spontaneously formed on to the rutile films. This revealed that rutile could be bioactivated. The analyses for the apatite coatings confirmed that the surface characterization of titanium has strong effect on bioactivity of titanium. The bioactivity of the rutile films on titanium was related not only to their surface basic hydroxyl groups, but also to acidic hydroxyl groups, and surface energy. Heat-treatment endowed titanium with bioactivity by increasing the amount of surface hydroxyl groups on titanium and its surface energy.

Volume of Fluid Model for Turbulence Numerical Simulation of Stepped Spillway Overflow

Abstract: The stepped spillway has increasingly become and effective energy dissipator. When the hydraulic performance of the overflow is clearly known, the energy dissipation could be increased. However, the study of stepped spillway overflow has been based only on model tests until now. In this paper, the \ik-ϵ turbulence model is used to simulate the complex turbulence overflow. The unstructured grid is used to fit the irregular boundaries and the volume of fluid method is introduced to solve the complex free-surface problem. The free surface, velocities, and pressures on the stepped spillway are obtained by the turbulence numerical simulation. Furthermore, the simulation results compare well with measured data. The study indicates that the turbulence numerical simulation is an efficient and useful method for the complex stepped spillway overflow.

A class of linear interval programming problems and its application to portfolio selection

Abstract: This paper discusses a class of linear programming problems with interval coefficients in both the objective functions and constraints. The noninferior solutions to such problems are defined based on two order relations between intervals, and can be found by solving a parametric linear programming problem. Considering the uncertain returns of assets in capital markets as intervals, we propose a model for portfolio selection based on the semiabsolute deviation measure of risk, which can be transformed to a linear interval programming model studied in the paper. The method is illustrated by solving a simplified portfolio selection problem.

C20-diterpenoid alkaloids

Abstract: Publisher Summary This chapter discusses the classification, distribution, and occurrence; biosynthesis and biogenesis; stereochemistry and reactions; and pharmacology of C 20 -diterpenoid alkaloids. With respect to the carbon skeleta, the C 20 -diterpenoid alkaloids may be divided into four classes: (1). Atisane-class: considered as the derivatives of aminated atisanes; (2) Kaurane-class: consided as the derivatives of aminated kauranes; (3) Rearranged-class: with a new heterocyclic skeleton formed by rearrangement of the hetisine- or denudatine-types; (4). Bisditerpcnoid-class: with the carbon skeleton of 40 or 39 carbon atoms—that is, by condensation of two Czo-diterpenoid alkaloids, or of one each of the C 20 - and C 19 -diterpenoid alkaloids. The richest sources of C 20 -diterpenoid aIkaloids are the plants of the two genera Aconitum and Delphinium in the Ranunculaceac and of the genus Spiraea in the Rosaceae. A sizable number of the C 20­ - diterpenoid alkaloids were isolated from the several Spiraea plants due to the Chinese scientists Liang and Hao. In addition, one interesting advance in the field is that three known C 20 -diterpenoid alkaloids acorientine, orientinine, and panicudine were identified from the epigeal parts of Rumex pictus by the Egyptian scientist Salama.

Chinese herbal medicines for type 2 diabetes mellitus

Abstract: Background Traditional Chinese herbal medicines have been used for a long time to treat diabetes, and many controlled trials have been done to investigate their efficacy. Objectives To assess the effects of Chinese herbal medicines in patients with type 2 diabetes mellitus. Search strategy We searched the following electronic databases: The Cochrane Library (CENTRAL), the Chinese BioMedical Database, MEDLINE, EMBASE, and LILACS, combined with hand searches on Chinese journals and conference proceedings. Date of last search was April 2004. No language restriction was used. Selection criteria Randomised trials of herbal medicines (with at least two months treatment duration) compared with placebo, pharmacological or non-pharmacological interventions were included. Data collection and analysis Data were extracted independently by two reviewers. The methodological quality of trials was evaluated using the parameters of randomisation, allocation concealment, double blinding, and drop-out rates. Meta-analyses were performed where data were available. Main results Sixty-six randomised trials, involving 8302 participants, met the inclusion criteria. Methodological quality was generally low. Sixty-nine different herbal medicines were tested in the included trials, which compared herbal medicines with placebo, hypoglycaemic drugs, or herbal medicines plus hypoglycaemic drugs. Compared with placebo, Holy basil leaves, Xianzhen Pian, Qidan Tongmai, traditional Chinese formulae (TCT), Huoxue Jiangtang Pingzhi, and Inolter showed significantly hypoglycaemic response. Compared with hypoglycaemic drugs including glibenclamide, tolbutamide, or gliclazide, seven herbal medicines demonstrated a significant better metabolic control, including Bushen Jiangtang Tang, Composite Trichosanthis, Jiangtang Kang, Ketang Ling, Shenqi Jiangtang Yin, Xiaoke Tang, and Yishen Huoxue Tiaogan. In 29 trials that evaluated herbal medicines combined with hypoglycaemic drugs, 15 different herbal preparations showed additional better effects than hypoglycaemic drugs monotherapy. Two herbal therapies combined with diet and behaviour change showed better hypoglycaemic effects than diet and behaviour change alone. No serious adverse effects from the herbal medicines were reported. Reviewers' conclusions Some herbal medicines show hypoglycaemic effects in type 2 diabetes. However, these findings should be carefully interpreted due to the low methodological quality, small sample size, and limited number of trials. In the light of some positive findings, some herbal medicines deserve further examination in high-quality trials.

Decentralized robust adaptive control of nonlinear systems with unmodeled dynamics

Abstract: The authors present a decentralized robust adaptive output feedback control scheme for a class of large-scale nonlinear systems of the output feedback canonical form with unmodeled dynamics. A modified dynamic signal is introduced for each subsystem to dominate the unmodeled dynamics and an adaptive nonlinear damping is used to counter the effects of the interconnections. It is shown that under certain assumptions, the proposed decentralized adaptive control scheme guarantees that all the signals in the closed-loop system are bounded in the presence of unmodeled dynamics, high-order interconnections and bounded disturbances. Furthermore, by choosing the design constants appropriately, the tracking error can be made arbitrarily small regardless of the interconnections, disturbances, and unmodeled dynamics in the system. An illustration example demonstrates the effectiveness of the proposed scheme.

Nano-CaCO3/polypropylene composites made with ultra-high-speed mixer

Abstract: In polymer-based nanocomposites, because of the large fraction of the nanoparticle atoms that reside at the interface, there would be a strong interface interaction between filler and polymer. The mechanical properties of nanocomposites would improve significantly at a low filler content if the ultrafine phase dimension was retained [1]. However, the homogeneous dispersion of nonaparticles is very difficult because nanoparticles with high surface energy are easy to agglomerate. To break up the agglomerates, studies have been carried out on the approaches of in situ polymerization of monomers in the presence of nanoparticles [2–4] and other intercalation polymerization techniques [5]. Although nanoparticles can be dispersed uniformly, the methods with complex processes, special conditions and high cost are limited to laboratory scale. Melt blending nanoparticles with polymer is the best compounding technique in the case of mass production of nanocomposites with low cost. In the literature [6–9], it is reported that the problem of melt blending is that nanoparticles tend to agglomerate due to their high surface energy during mixing even when the nanoparticle content in the composites is small. The key is to decrease the surface energy of the nanoparticles, however, the uniform surface coverage of nanoparticles is hard to realize by simply physical and mechanical means. In order to resolve this problem, an ultra-high-speed mixer has been designed to treat the surface of the nanoparticles [10]. The mixer has high speed (6000 rpm), special rotors that are designed to deal with nanoparticles. Under high shear force, the nanoparticle surface is modified with coupling agent, which is added by means of an atomizer. The purpose of this letter is to show how efficiently the mechanical performance of the nanocomposites can be improved by the above approach. Isotactic polypropylene (PP) homopolymer (melting flow index (MI) = 5g/10 min) was used as matrix and CaCO3 (diameter = 70 nm, density = 2400 kg/m3) was selected as the filler. Stearic acid was used as coupling agent. Nano-CaCO3 and stearic acid were mixed in the high speed mixer for 5 min. Because of high shear force, the temperature of mixtures could increase to 140 ◦C, and the powders were ready for compounding. PP and fillers were melt mixed in a twin-screw extruder at 200 ◦C and 100 rpm. The specimens for

Internet-based manufacturing: a review and a new infrastructure for distributed intelligent manufacturing

Abstract: Global competition and rapidly changing customer requirements are forcing major changes in the production styles and configuration of manufacturing enterprises Traditional centralized manufacturing systems are not able to meet these requirements In recent years, the internet has become the worldwide information platform for the sharing of information and data Information processing is an important challenge in an internet-based manufacturing environment, and must facilitate distribution, heterogeneity, autonomy and cooperation This paper reviews recent trends and major developments in internet-based manufacturing Broad categories of distributed information management are identified, based upon the development of computer integrated manufacturing, and the possible direction of future research is indicated

Convergence of implicit iteration process for a finite family of asymptotically nonexpansive mappings in banach spaces

Abstract: The purpose of this paper is to study the weak and strong convergence of implicit iteration process to a common fixed point for a finite family of asymptotically nonexpansive mappings and nonexpansive mappings in Banach spaces. The results presented in this paper extend and improve the corresponding results of Refs. [1], 5-7, 10-11.

Study on the volumetric expansion of benzoxazine curing with different catalysts

Abstract: A systematic investigation on the volumetric expansion of four benzoxazine systems, which are benzoxazine, benzoxazine/tertiary amine, benzoxazine/organic acid, and benzoxazine/epoxy resin/tertiary amine, was done. By using gravitometric and dilatometric methods, etc., studies on volumetric shrinkage, isothermal cure shrinkage, and density versus cure time plots were done. The cure reactions of these benzoxazines were carried out at 140 and 160°C. The results show that all benzoxazine systems exhibit apparent volumetric expansion after polymerization, that is, the densities of monomers are larger than are those of polymers at room temperature. But, meanwhile, they exhibit volumetric shrinkage while curing isothermally. The results also show that the higher the cure temperature is, the larger the cure shrinkage of the benzoxazines will be and that the extent of the cure shrinkage of the benzoxazines with the aid of catalysts is larger than is that of thermal polymerization systems. The reason for this is that, accelerated by catalysts, the polymerization rate become faster and the extent of polymerizatiom becomes larger. It is obvious that catalysts can make a notable impact on the cure reaction of benzoxazines. Therefore, the dimension of the volumetric expansion of benzoxazine is associated with its polymerization mechanism, molecular structure, and extent of polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1107–1113, 2002; DOI 10.1002/app.10267

Induction of apoptosis by norcantharidin in human colorectal carcinoma cell lines: involvement of the CD95 receptor/ligand.

Abstract: Purpose: Cantharidin, a natural toxin, is the active substance of mylabris and has antitumor effects in man. Norcantharidin, the demethylated analogue of cantharidin, has been used in the treatment of patients with primary hepatoma and those with leukopenia in China. The present study was designed to investigate whether norcantharidin exerts cytotoxic activity against colorectal cancer cells by inducing apoptosis and to examine the possible mechanism in the phenomenon. Methods: Inhibition of proliferation of norcantharidin on Colo205, HT-29, and SW480 colorectal cancer cells was determined by the trypan blue dye exclusion test. Apoptosis of norcantharidin-treated cells was determined by morphological analysis, agarose gel DNA electrophoresis, and quantitated by flow cytometry after staining with propidium iodide. Cell cycle and the cell surface expression of the CD95/CD95 ligand were evaluated by flow cytometry. Caspase 8-like protease and protein phosphatase 1 and 2A activities were also analyzed. Results: Treatment with norcantharidin of colorectal cancer cells not only inhibited cell proliferation, but also induced apoptosis. Norcantharidin induced apoptosis mainly in two phases: rapid apoptosis in S-phase cells and delayed apoptosis in G2/M arrested cells. Treatment with norcantharidin resulted in an upregulation of the CD95 receptor and CD95 ligand on the cell surface. Furthermore, stimulation with anti-CD95 monoclonal antibody (mAb) resulted in further induction of apoptosis after treatment with norcantharidin. In addition, the apoptosis-inducing effect of norcantharidin was almost completely inhibited by anti-CD95 ligand mAb. Norcantharidin-treated cells showed the activation of caspase 8. Both zVAD-FMK (a broad range caspase inhibitor) and IETD-FMK (a caspase-8 inhibitor) showed apparent inhibition of the apoptosis-inducing effect. Norcantharidin did not show an inhibitory effect on protein phosphatase. Conclusions: These results suggest that norcantharidin triggers apoptosis in colorectal cancer cell lines via the activation of the CD95 receptor/ligand system, and that this agent may be useful for developing new therapeutic regimens for the treatment of colorectal carcinoma.

Adsorption and desorption of copper(II) from solutions on new spherical cellulose adsorbent

Abstract: An investigation was conducted on the adsorption and desorption of copper(II) from aqueous solutions with a new spherical cellulose adsorbent containing the carboxyl anionic group. Various factors affecting the adsorption were optimized. The adsorption of Cu2+ ions on the adsorbent was found to be dependent on the initial time and pH, the concentration, and the temperature. The adsorption process follows both Freundlich and Langmuir adsorption isotherms and was found to be endothermic (DeltaH = 23.99 kJ/mol). The Cu2+ ions adsorbed on the adsorbent can be recovered with a NaOH or HCl aqueous solution. The maximum percentage of recovery is about 100% when 2.4 mol/L HCl solution is used. In addition, only 7.2% of the adsorption capacity is lost after 30 replications of the adsorption and desorption. (C) 2002 John Wiley Sons, Inc.

Influencing factors of pancreatic microcirculatory impairment in acute panceatitis

Abstract: Pancreatic microcirculatory disturbance plays an important role in th e pathogenesis of acute pancreatitis, and it involves a series of changes including vasoconstriction, ischaemia, increased vascular permeability, impairment of nutritive tissue perfusion, ischaemia/reperfusion, leukocyte adherence, hemorrheological changes and impaired lymphatic drainage. Ischaemia possibly acts as an initiating factor of pancreatic microcirculatory injury in acute pancreatitis, or as an aggravating/continuing mechanism. The end-artery feature of the intralobular arterioles suggests that the pancreatic microcirculation is highly susceptible to ischaemia. Various vasoactive mediators, as bradykinin, platelet activating factor, endothelin and nitric oxide participate in the development of microcirculatory failure.

A highly enantioselective hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene catalyzed by chiral titanium(IV) 5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol complexes.

Abstract: The catalytic effect of chiral Lewis acids on the hetero-Diels-Alder reaction between aldehydes and Danishefsky's diene (1) has been investigated A variety of combinations of different ligands and Lewis acids have been examined as catalysts for the hetero-Diels-Alder reaction between benzaldehyde and 1, and it has been found that the readily accessible Ti(IV)-H(8)-BINOL (TiHBOL) complex is a very effective catalyst for the reaction, leading to products with very high enantioselectivity (up to 99% ee) and yield (92%) The hetero-Diels-Alder reaction of other aldehydes with 1 under the catalysis of TiHBOL is a general reaction which proceeds well with very high enantioselectivity and isolated yield for various aldehydes at 0 degrees C to room temperature Based on the experimental results, the proposed mechanism of the hetero-Diels-Alder reaction and the dihedral angle effects of ligands are discussed

Möbius Isoparametric Hypersurfaces in S n+1 with Two Distinct Principal Curvatures

Abstract: A hypersurface x : M → S n+1 without umbilic point is called a Mobius isoparametric hypersurface if its Mobius form Φ = −ρ −2∑ i (e i (H) + ∑ j (h ij −Hδ ij )e j (log ρ))θ i vanishes and its Mobius shape operator $$ {\Bbb {S}}$$ = ρ −1(S−Hid) has constant eigenvalues. Here {e i } is a local orthonormal basis for I = dx·dx with dual basis {θ i }, II = ∑ ij h ij θ i ⊗θ i is the second fundamental form, $$H = {1 \over n}\sum olimits_i {h_{ii} ,\rho^2 = {n \over {n - 1}}( {|| II ||^2 - nH^2 } )}$$ and S is the shape operator of x. It is clear that any conformal image of a (Euclidean) isoparametric hypersurface in S n+1 is a Mobius isoparametric hypersurface, but the converse is not true. In this paper we classify all Mobius isoparametric hypersurfaces in S n+1 with two distinct principal curvatures up to Mobius transformations. By using a theorem of Thorbergsson [1] we also show that the number of distinct principal curvatures of a compact Mobius isoparametric hypersurface embedded in S n+1 can take only the values 2, 3, 4, 6.

Allelic association analysis of the dopamine D2, D3, 5-HT2A, and GABAAγ2 receptors and serotonin transporter genes with heroin abuse in Chinese subjects

Abstract: Five candidate genes, the receptors DRD2, DRD3, HTR2A and GABA(A)gamma2, and the serotonin transporter (5-HTT) were analyzed for association with heroin abuse. We examined three polymorphisms (promoter - 141DeltaC, Ser311Cys, and TaqI) in the DRD2 gene, one polymorphism (Ser9Gly) in the DRD3 gene, two polymorphisms (promoter - 1438G/A and T102C) in the HTR2A gene, two polymorphisms (VNTR and Del/Ins) in 5-HTT gene, and one polymorphism (G3145A) in GABA(A)gamma2 gene in 121 Chinese heroin addicts and 194 controls. None of the polymorphisms differed significantly for allele, genotype, or haplotype frequencies, except for the DRD2 promoter polymorphism - 141DeltaC (genotype-wise and allele-wise, P = 0.05, uncorrected). An additional 344 subjects with heroin abuse and 104 controls were investigated for the - 141DeltaC polymorphism. In the second sample, there were no significant difference of genotype or allele frequencies between subjects with heroin abuse and normal controls. When we divided the sample by route of administration into nasal inhalers and IM or IV injectors, however, it produced a significant difference between inhalers of heroin and controls (genotype-wise, P = 0.006, allele-wise, P = 0.016) but not for injectors of heroin (genotype-wise, P = 0.81, allele-wise, P = 0.69). We also found that LD between all polymorphisms we examined in the gene was weak, possibly explaining why we see association of this polymorphism with heroin abuse but not with other markers in the gene. Overall our results indicates that the HTR2A, 5-HTT, DRD3 and GABA(A)gamma2 genes are not likely to be a major genetic risk factor for heroin abuse in this population, with the exception of possible association between nasal inhalation and DRD2 promoter - 141DeltaC polymorphism.