Synthesis and biodegradation of poly(γ-butyrolactone-co-l-lactide)

Biodegradable polyesters were synthesized by ring-opening copolymerization of p683m4k77564/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.p>1p>H andp>13p>C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×10p>4p>. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT _m andT _g values of the copolymers showed a gradual depression with an increase in BL content. NoT _m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of p683m4k77564/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-methyl-p683m4k77564/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-butyrolactone (MBL) or p683m4k77564/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-ethyl-p683m4k77564/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers.     

浅论建筑消防安全性能化评估技术

建筑消防安全性能化设计以其灵活性、科学性、经济性和有效性等优点受到了国际社会越来越多的重视,并在很多国家得到了应用。性能化评估作为性能化设计的核心环节,直接关系到性能化设计方案的成败。如何进行性能化评估,如何对性能化设计方案的评价和论证,如何设定相应的消防安全性能评估程序等等问题,都值得深入探讨。从建筑消防安全性能化设计的优点及其评估的重要性入手,从性能化评估的作用和必要性出发,深入分析了建筑消防安全性能化评估与性能化设计的关系;探讨了建筑消防安全性能化评估的步骤、流程、判定标准及其量化指标;并对国际上常用于性能化评估的3种典型的火灾风险评估模型进行了详细对比分析,并提出了进行性能化评估时需注意的一些关键问题。     

On the moral acceptability of killing animals

According to a p80/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">rights viewp80/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> it is acceptable to kill animals if they are innocent threats or shields or are in a p80/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">lifeboat situation.p80/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> However, according to advocates of such a view, our practices of killing animals for food or scientific research may be morally unacceptable. In this paper we argue that, even if we grant the basic assumptions of a rights view, a good deal of killing of animals for food and scientific research continues to be morally acceptable.     

Radiation Effects on Blends of Poly(ε-Caprolactone) and Diatomites

Poly(p3q68258u6k38035/xxlarge949.gif" alt="epsi" align="BASELINE" BORDER="0">-caprolactone) (PCL) was blended with diatomaceous earth (diatomite) and irradiated with p3q68258u6k38035/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-rays to introduce cross-linking between PCL molecules or both components. The unwashed diatomite containing a little of a volatile component showed high efficiency of introduction of cross-linking, whereas that with no volatile component showed low efficiency of introduction of cross-linking. Elongational viscosity, melt viscosity, and modulus of PCL/diatomite blend irradiated at various doses were significantly improved. Enzymatic degradation of the PCL/diatomite blend became faster than that of the PCL, though that of the blend irradiated became slower.     

Morphophysiological Rearrangements in Fish in Response to Pollution (in the Light of S.S. Shvarts' Theory)

The results of a study on morphophysiological variation in fish inhabiting a subarctic lake exposed to chronic industrial pollution are described using an example of cisco, Coregonus lavaretus. It is shown that indices of the heart, liver, kidneys, gills, and fatness in these fish are increased significantly and have retained increased values for the past 20 years. The observed changes are analyzed on the basis of biochemical data. The results of studies on the dynamics of hematological parameters in fish are used for characterizing the development of toxicosis. Adaptive rearrangements associated with an increase in the metabolic rate and the activation of protective systems in the fish are explained in the context of S.S. Schvarts' concept. The idea is proposed that the additional p6/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">energy costp6/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> of detoxification may be responsible for morphophysiological variation in fish under conditions of water pollution.     

Metabolic fate of dichloromethyl‐0,0‐diphenyl phosphonate (I) and dichloromethyl‐0,0‐di‐(p‐nitrophenyl) phosphonate (II) in/on rice plants∗

Abstractp> Metabolic fate of two dichloromethyl diaryl phosphonates (p>32p>P labelled) in/on rice plants was investigated. The test compounds were found to be less persistent on the surface of rice leaves with half lives 7.4 and 6.7 days respectively. Main degradation product from both the phosphonates were dichloromethyl phosphonic acid with trace of dichloromethyl‐O‐aryl phosphonate as a transitory intermediate product.     

Levels of Persistent Organochlorine Residues in Eggs of Greater Flamingos from the Guadalquivir Marshes (Doñana), Spain

p> Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) residue levels were determined in 53 unhatched eggs from greater roseus flamingos (Phoenicopterus ruber). Eggs were collected in 1996 from the National Park of Doñana (Guadalquivir marshes, Southwest Spain), immediately after one breeding colony abandoned the nesting site due to predator attacks. The main metabolite of p,p′-DDT, p,p′-DDE, was the OCP residue found at higher concentrations, with a geometric mean of 721 ng/g wet weight. Residues of other pesticides, including some hexachlorocyclohexane isomers, hexachlorobenzene, aldrin, heptachlor, and heptachlor-epoxide, were detected at much lower concentrations. The sum of PCBs was 528 ng/g, with PCB congeners #187 and #153 being the most prominent in eggs. The pattern observed in these compounds of industrial origin corresponded more to Aroclor 1260 than to any other commercial mixture. Levels of organochlorine residues indicate a medium degree of exposure, and they are not considered of any concern for the flamingo population. In particular, neither p,p′-DDE nor PCB levels were found to be correlated with the eggshell thickness.     

Prenatal diagnosis and fetal pathology of partial trisomy 20p–monosomy 4p resulting from paternal translocation

Amniocentesis was performed in view of a paternal balanced chromosomal rearrangement t(4;20)(p16;p12), inv(18)(p11q11). The pregnancy was complicated by severe oligohydramnios. The fetal karyotype was unbalanced: 46XX, der(4), t(4;20)(p16;p12), inv(18) (p11q11)pat., thus resulting in partial trisomy 2Op and monosomy 4p. In addition, the amniotic fluid alpha-fetoprotein (AFP) became increasingly elevated with gestational age. The pregnancy was terminated at 25 weeks. The fetus presented with typical facial dysmorphic features, unilateral cleft lip and palate, severe renal hypoplasia, consistent with the 4p- (Wolf-Hirschhorn) syndrome.