氟化物对幼年大鼠骨矿物质和血微量元素的影响及其相关性研究

为探讨氟化钠对幼年大鼠血清4种微量元素和骨矿物质含量的影响,以及大鼠骨矿物质和血清微量元素的相关性,将80只2月龄SPF级SO大鼠,雌雄各半,随机分成8组：对照（幼年CS、成年AS）组和用药组（幼年高氟组CHS、幼年低氟组CLS、成年高氟组AHS、成年低氟组ALS、幼年长期高氟组HS、幼年长期低氟组15）。对照组灌胃生理盐水,用药组分别按相应时间给予不同剂量的NaF灌胃,测定了大鼠尺骨和血清中的Ca、P、Fe、Zn含量。结果表明,（1）血清微量元素：①与cs组相比,CHS组和CLS组的磷（P）分别增加100．0％和193．8％（P〈0．05）。②与AS组相比,HS组的Ca、Zn分别下降了20．5％和40．0％,而P则增加了74．0％（P〈0．05）;Ls组的Zn下降了33．3％（P〈0．05）。与HS组比较,CHS组的Ca增加22．3％。③与LS组比较,CLS组的P和Zn明显增加49．2％和28．5％（P〈0．05）。（2）骨矿物质：①与As组相比,HS组的Ca分别下降了23．9％（P〈0．05）,Zn则增加了36．1％（P〈0．05）。②与HS组相比,CHS组的Ca和Fe分别增加了42．3％和36．05％,Zn下降了38．6％（P〈0．05）。（3）骨矿物质和血清微量元素的相关性：骨Ca和血Ca、骨P和血P、骨Zn和血Zn、骨Fe和血Fe的相关系数分别为0．435、0．347、0．136和0．059（P〉0．05）。提示长期使用氟化钠,可以导致幼年大鼠血中微量元素代谢紊乱,骨矿物含量降低,但未确定大鼠骨矿物含量和血微量元素具有相关性。     

TEP-DMAc混合溶剂对PVDF膜性能的影响

利用非溶剂相转化法(NIPS)制备聚偏氟乙烯(PVDF)膜,考察了聚乙二醇(PEG200)与N,N-二甲基乙酰胺(DMAc)的质量比对膜分相速率和膜性能的影响,讨论了以磷酸三乙酯(TEP)和DMAc的混合液作溶剂对PVDF膜凝胶速率、膜结构和膜通量的影响。结果表明:PEG200的加入减弱了溶剂对聚合物的溶解能力,但铸膜液的分相行为由延迟分相转变为瞬时分相,膜通量提高。随着混合溶剂中TEP含量的增大,铸膜液的黏度增大,分相速率减慢;在高质量比m(TEP)/m(DMAc)时,膜表面的孔增多,指状孔膜结构逐渐消失,整个膜截面呈海绵状,膜通量变大,力学性能提高。     

TIPS法制备聚偏氟乙烯平板微孔膜及其表征

以邻苯二甲酸二甲酯(DMP)为稀释剂,采用热致相分离法(TIPS)制备了聚偏氟乙烯(PVDF)平板微孔膜。利用差示扫描量热仪分析了不同PVDF/DMP体系的结晶性能;通过测试纯水通量、孔隙率、泡点、平均孔径、拉伸强度等对膜进行了表征。结果表明:DMP含量增大,结晶温度向低温方向移动,膜拉伸强度降低,当DMP的质量分数为0.70时膜拉伸强度有明显拐点;PVDF/DMP体系冷却发生固-液相分离;PVDF含量增大,膜水通量、孔隙率、最大孔径和平均孔径均减小。     

Experimental and chemical kinetic study of the pyrolysis of trifluoroethane and the reaction of trifluoromethane with methane

A detailed reaction mechanism is developed and used to model experimental data on the pyrolysis of CHF₃ and the non-oxidative gas-phase reaction of CHF₃ with CH₄ in an alumina tube reactor at temperatures between 873 and 1173 K and at atmospheric pressure. It was found that CHF₃ can be converted into C₂F₄ during pyrolysis and CH₂CF₂ via reaction with CH₄. Other products generated include C₃F₆, CH₂F₂, C₂H₃F, C₂HF₃, C₂H₆, C₂H₂ and CHF₂CHF₂. The rate of CHF₃ decomposition can be expressed as 5.2×10¹³ [s−1] e−295[kJ mol−1]/RT. During the pyrolysis of CHF₃ and in the reaction of CHF₃ with CH₄, the initial steps in the reaction involve the decomposition of CHF₃ and subsequent formation of CF₂ difluorocarbene radical and HF. It is proposed that CH₄ is activated by a series of chain reactions, initiated by H radicals. The NIST HFC and GRI-Mech mechanisms, with minor modifications, are able to obtain satisfactory agreement between modelling results and experimental data. With these modelling analyses, the reactions leading to the formation of major and minor products are fully elucidated.     

Effect of solution extrusion rate on morphology and performance of polyvinylidene fluoride hollow fiber membranes using polyvinyl pyrrolidone as an additive

<正>Polyvinylidene fluoride(PVDF) hollow fiber membranes prepared from spinning solutions with different polyvinyl pyrrolidone(PVP) contents(1%and 5%) at different extrusion rates were obtained by wet/dry phase process keeping all other spinning parameters constant.In spinning these PVDF hollow fibers,dimethylacetamide(DMAc) and PVP were used as a solvent and an additive,respectively.Water was used as the inner coagulant.Dimethylformamide(DMF) and water(30/70) were used as the external coagulant.The performances of membranes were characterized in terms of water flux,solute rejection for the wet membranes.The structure and morphology of PVDF hollow fiber were examined by BET adsorption,dry/wet weight method and scanning electron microscopy(SEM).It is found that the increase in PVP content and extrusion rate of spinning solution can result in the increase of water flux and decrease of solute rejection.The improvements of interconnected porous structure and pore size are induced by shear-thinning behavior of spinning solution at high extrusion rates,which could result in the increase of water flux of hollow fiber membranes.The increase of extrusion rate also leads to the increase of membrane thickness due to the recovery effect of elastic property of polymer chains.     

Synthesis of Alkyl-Aryl Ethers by Copper-catalyzed Etherization Reactions of Aryl Fluorides with Tetraalkylammonium Bromides and H2O

Synthesis of alkyl aryl ethers via copper‐catalyzed etherizations of electron‐deficient aryl fluorides with quaternary ammonium bromides and water has been developed. In the presence of Cu(OAc)₂, POPh₃ ( L4 ) and Cs₂CO₃, a variety of electron‐deficient aryl fluorides underwent the reaction with quaternary ammonium bromides and H₂O in moderate to good yields. The mechanism was also discussed.     

Effect of thermal treatment on the characteristics of electrospun PVDF−silica composite nanofibrous membrane

Composite nanofibrous membranes were prepared by the electrospinning and the thermal treatment from poly(vinylidene fluoride) (PVDF)-tetramethyl orthosilicate (TMOS) blend solutions. The average diameter of nanofibers was reduced with increasing the concentration of TMOS in the solution due to the decrease of the solution viscosity. The EDX spectra confirmed the presence of TMOS on the external surface of the composite nanofibrous membrane. The porosity of membranes was effectively enhanced by the introduction of electrospinning technique. However, the mechanical properties, thermal stability and hydrophobicity were not markedly amplified. Thus the thermal treatment of the composite membranes was carried out, leading to the enormous enhancement of the mechanical properties and hydrophobicity. In addition, XRD results revealed that the crystal structure of PVDF in the composite membranes transformed from α-phase to β-phase due to the formation of silica particles by the thermal treatment.     

Coupled structural and magnetic properties of ferric fluoride nanostructures part I: A Metropolis atomistic study

A modified Metropolis atomistic simulation is proposed to model the structure of grain boundaries (GBs) and interfaces in ionic nanostructured systems and is applied to the magnetically interesting case of iron trifluoride (FeF₃). We chose long-range interatomic potentials adjusted on experimental results and adapted a previously established Monte Carlo scheme consisting of various modifications of the simulated annealing/Metropolis algorithm. Atomic structures of twisted and tilted GBs as a function of the relative disorientation of the grains have been achieved yielding close to experimentally measured properties. This approach takes into account the structure of the grains far from the interface in order to constrain the relative orientation of the grains, without any periodic boundary conditions. One concludes that a long-range Coulombic fall off of the interatomic potentials is necessary to obtain GB structures presenting a correct local topology but with a smooth transition from crystalline to amorphous states. The structural features are finally discussed in terms of topological aspects and local magnetic structure.