Risk Behaviors for Reproductive Tract Infection in Women Who Have Sex with Women in Beijing, China

OBJECTIVES: To assess risk behaviors for reproductive tract infections (RTI) including sexually transmitted infections (STI) among women who have sex with women (WSW) in Beijing, China. METHODS: A cross-sectional study of women recruited from venues and internet outreach analyzed using interviews. RESULTS: We recruited 224 WSW, among whom were 37 couples. The average age of participants was 25.6 years. Sex with men in the past year was reported by 10.7% of participants. During the past year, 34.3% (77/224) had had >1 sexual partner and 72.4% (162/224) had ever had >1 sexual partner. Condom use in the last sex with a man was reported by 54.2% (13/24) of women; 12.5% (3/24) reported never having used a condom with a man in the past year. In the past year, 13.4% (30/224) reported using sex toys with their female partners; of these, 43.3% (13/30) reported consistent condom use with the sex toys and 36.7% (11/30) had shared sex toys. Among participants 65.2% (120/184) reported that their "G-spot" had been stimulated during sex, 49.2% (59/120) of whom reported bleeding during or after sex. Only 12.5% (8/64) of those never reporting "G spot" stimulation reported bleeding during or after sex (P<0.001). CONCLUSIONS: WSW in Beijing engaged in high-risk sexual behaviors that may carry a substantial risk of being infected with STI/RTI. To implement STI/RTI prevention and intervention among women, women-women sexual behavior should be considered when doing research and intervention programs

True intrinsic mechanical behaviour of semi-crystalline and amorphous polymers: Influences of volume deformation and cavities shape

International audienceA model enabling the determination of the intrinsic mechanical constitutive equations of uniaxially stretched polymers is presented. This model takes into account the cavitation-induced volume strain which can occur during the deformation of such materials. In particular, the true intrinsic axial stress and strain depends on the overall volume strain and a form factor depicting the evolution of the voids shape. Based on our model, the true intrinsic behaviour of high-density polyethylene (HDPE), polypropylene/ethylene-propylene rubber (PP/EPR), and polyethylene terephtalate (PET) was assessed in tension. Compared to the overall true behaviour, the intrinsic true behaviour of the materials did not exhibit anomalies at large strain levels with changing experimental parameters (strain rate and temperature), and can be accurately predicted by means of phenomenological constitutive equations as the one proposed by G'sell and Jonas (1979)

Volume Variation Process of High-Density Polyethylene During Tensile and Creep Tests

Samples of high-density polyethylene have been subjected to tensile tests and creep experiments by means of a video-controlled testing system (VidéoTraction ©). The evolution of specific volume in this semi-crystalline polymer is determined versus true strain. In the elastic stage, we measure a hydrostatic expansion and then, in the plastic stage, we observe a competition between a compaction effect and a dilatation phenomenon. Although compaction is probably overestimated in the present testing technique, it represents a pertinent mechanism that is ascribed to the orientation of the amorphous chains during stretching. This phenomenon is characterized by X-ray diffraction measurements that show a reduction of average distance between amorphous chains. Dilatation process is explained by the diminution of crystallinity and by the formation, growth and coalescence of crazes inside and between spherulites. Electron microscopy reveals these defects. The competition between compaction and dilatation, controlled by the mobility of the amorphous phase, depends on temperature and time

Influence of chain orientation on the dissipated energy during reciprocating sliding test for ultra-high molecular weight polyethylene

abstract + poster presentationstatus: publishe

Micromechanical modeling of the elastic behavior of polypropylene based organoclay nanocomposites under a wide range of temperatures and strain rates/frequencies

International audienc

Experimental investigation and micromechanical modeling of high strain rate compressive yield stress of a melt mixing polypropylene organoclay nanocomposites

International audienc

Resolving cavitation in silica-filled styrene-butadiene rubber composites upon cyclic tensile testing

Cavitation phenomena were resolved in silica-filled styrene-butadiene-rubber composite upon cyclic tensile testing, prior to and after an accelerated thermal exposure. To this end, 3D digital image correlation (3D-DIC) and micro-computed x-ray tomography (μCT) were employed with in-situ approaches. It was found that thermal exposure induced structural changes in the composite similar to those occurring in real tires, such as the increase of the crosslink density of the rubber matrix, and the increase of its stiffness. The 3D-DIC measurements revealed that the mechanical hysteresis and volume strain were higher in the thermally-treated composite. The μCT results indicated three types of cavitation phenomenon as sources of volume change: i) debonding at the agglomerate poles, ii) internal agglomerate fracture and iii) a combination of both of them. Cavities were initially oblate and became more spherical when stretching the materials. The μCT measurements confirmed a faster increase in size and sphericity of voids for the thermally-treated composite when deformed, which is probably due to the higher stiffness of the rubber matrix

Effect of ZnO and organo-modified montmorillonite on thermal degradation of poly(methyl methacrylate) nanocomposites

International audienceSince a few years ago, a topic of interest consists in developing composites filled with nanofillers to improve thermal degradation and flammability property of poly(methyl methacrylate) (PMMA). In the present work, the effects of ZnO nanoparticles and organo-modified montmorillonite (OMMT) on the thermal degradation of PMMA were investigated by thermogravimetric analysis (TGA). PMMA–ZnO and PMMA–OMMT nanocomposites were prepared by melt blending with different (2, 5, and 10 wt%) loadings. SEM and TEM analyses of nanocomposites were performed in order to investigate the dispersion of nanofillers in the matrix. According to TGA results, the addition of ZnO nanoparticles does not affect the thermal degradation of PMMA under an inert atmosphere. However, in an oxidative atmosphere, two contrary effects were observed, a catalytic effect at lower concentration of ZnO in the PMMA matrix and a stabilizing effect when the ZnO concentration is higher (10 wt%). In contrast, the presence of OMMT stabilizes the thermal degradation of PMMA whatever be the atmosphere. Differential thermal analysis (DTA) curves showed surprising results, because a dramatic change of exothermic reaction of the PMMA degradation process to an endothermic reaction was observed only in the case of OMMT. During the degradation of PMMA–ZnO nanocomposites, pyrolysis-gas chromatography coupled to mass spectrometer (Py-GC/MS) showed an increase in the formation of methanol and methacrylic acid while a decrease in the formation of propanoic acid methyl ester occurred. In the case of PMMA–OMMT systems, a very significant reduction in the quantity of all these degradation products of PMMA was observed with increasing OMMT concentration. It is also noted that during PMMA–OMMT degradation less energy was released as the decomposition is an endothermic reaction and the material was cooled