High postnatal exposures to polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) via breast milk in California: does BDE-209 transfer to breast milk?

Breast milk samples collected during 2003-2005 from 82 first-time mothers in 24 communities located throughout California contained levels of polybrominated diphenyl ethers (∑(tri-hexa (8))PBDEs; median = 53.3 ng/g lw, range = 9.60-1291) and polychlorinated biphenyls (∑(12)PCBs; median = 73.4 ng/g lw, range = 22.2-433) that are among the highest in the world. PBDE levels varied 100-fold. BDE-47 was the dominant PBDE congener, with levels exceeding the U.S.EPA Reference Dose (RfD) for neurodevelopmental toxicity (100 ng/kg/day) in most (60%) breast milk samples. In some samples, BDE-209 (2/82) and/or BDE-153 (5/82) were the dominant congeners, suggesting that BDE-209 can transfer to breast milk and/or break down in the mother and transfer to the nursing infant as the lower-brominated PBDEs associated with adverse effects. PBDE levels in California breast milk are approaching those of PCBs, and the trend PBDEs > PCBs may continue as PBDEs migrate from products to the indoor and outdoor environments.     

酵母振动膜过滤系统的应用研究

本文通过对酵母振动膜过滤系统的组成,系统分离的过程、原理,系统的优点,系统的运行状况,以及系统的经济技术特点进行论述,阐明了酵母振动膜过滤系统的应用价值。     

一种新结构超支化环氧树脂的合成及其性能研究

以双酚A(BPA)作为A2单体,异氰尿酸三缩水甘油酯(TGIC)作为B3单体,采用质子转移法合成了一种结构新颖的超支化环氧树脂.采用FTIR、NMR、GPC对该环氧树脂的结构和分子量进行了表征.固化产物的极限氧指数达到26,热分解(5%)温度为266℃,具有较好的阻燃性与热稳定性.     

复合涂料中纳米TiO2降解污染物和抗菌性能研究

利用纳米尺度分散TiO2的光催化作用,研究纳米TiO2光催化剂复合涂料降解空气中氨气、甲醛和苯类化合物及抗菌防霉的性能。测试结果表明：该涂料对密闭空间内的甲醛、氨气和苯类等化合物的降解效率均可达到90％以上,对多种有害细菌均具有杀菌彻底性和长效性,并且其光催化作用可以摆脱光源条件的严格限制。并探讨了纳米TiO2复合涂料光催化降解及抗菌作用的机理。     

钙铝类水滑石结构与组成研究

钙铝类水滑石是一种典型层状复合金属氢氧化物,被广泛用作PVC材料的热稳定剂、建筑材料、水污染处理等领域。文章通过晶体化学理论建立Ca/Al-LDHs微观结构模型与静电作用模型,运用几何函数与晶格能Kapustinskii方程,对钙铝类水滑石的结构与热稳定性做出参数量化估算。研究结果表明,该组模型可以用于钙铝类水滑石的结构与性能的简单预测与比较,同时也能为研究新型插层Ca/Al-LDHs材料提供较有价值的参考。     

污染水体脱氮工艺中外加碳源的研究进展

碳源是传统生物脱氮过程中的一个重要因素,当水体中碳氮质量比过低时,往往需要投加外加碳源作为电子供体,以保证反硝化反应的顺利进行.作者主要对污水脱氮过程中添加不同外加碳源后,对氮的去除率、工艺的优缺点及成本等方面进行了总结.     

Synthesis and heavy metal immobilization behaviors of fly ash based gepolymer

Two aspects of studies were carried out: 1) synthesis of geopolymer by using fly ash and metakaolin; 2) Immobilization behaviors of fly ash based geopolymer in a presence of Pb and Cu ions. As for the synthesis of fly ash based geopolymer, 4 different fly ash content (10%, 30%, 50%, 70%) and 3 types of curing regimes (standard curing, steam curing and autoclave curing) were investigated to obtain the optimum synthesis condition based on the compressive and flexural strength. The experimental results show that geopolymer, containing 30% fly ash and synthesized at steam curing (80° for 8 h), exhibits higher mechanical strengths. The compressive and flexural strengths of fly ash based geopolymer reach 32.2 MPa and 7.15 MPa, respectively. Additionally, Infrared (IR) and X-ray diffraction (XRD) techniques were used to characterize the microstructure of the fly ash geopolymer. IR spectra shows that the absorptive band at 1086 cm⁻¹ shifts to lower wave number around 1033 cm⁻¹, and the 6-coordinated Al transforms into 4-coordination during the synthesis of fly ash based geopolymer. The resulting geopolymeric products were X-ray amorphous materials. As for immobilization of heavy metals, the leaching tests were employed to investigate the immobilization behaviors of the fly ash based geopolymer synthesized under the above optimum condition. The leaching tests showed that fly ash based geopolymer can effectively immobilize Cu and Pb heavy metal ions, and the immobilization efficiency reached 90% greater when heavy metals were incorporated in the fly ash geopolymer in the range of 0.1% to 0.3%. The Pb exhibits better immobilization efficiency than the Cu, especially in the case of large dosages of heavy metals.     

新型半桥高频软开关PWM DC-DC气保逆变焊机

在传统半桥气保逆变焊机中,功率开关多处于硬开关状态或部分软开关状态。当其开关频率过高时损耗很大,降低了工作效率。本文提出了一种新型半桥高频软开关PWMDC-DC拓扑,该拓扑具有电路结构简单、逆变开关频率高、所有开关器件均能实现ZVZCS通断、控制方便等优点。在分析新型半桥软开关气保逆变拓扑工作原理的基础上,研究了一种适用于低电压、大电流场合的全数字化控制的新型半桥高频软开关气保逆变焊机。新型半桥软开关气保逆变焊机电路的实验与仿真结果验证了数字化控制的新型半桥软开关系统的优良性能。     

2-(乙酰基-乙氧羰基)亚甲基四氢咪唑与Fe(Ⅲ)、Fe(Ⅱ)、Cu(Ⅱ)相互作用的快原子轰击质谱研究

本文利用快原子轰击质谱研究了2－（乙酰基－乙氧羰基）亚甲基四氢咪唑与Fe（Ⅲ）、Fe（Ⅱ）、Cu（Ⅱ）间的相互作同。不同的质谱特征表明了Fe（Ⅲ）与配位体形成了稳定的配合物，而Fe（Ⅱ）和Cu（Ⅱ）却具有促进配体之间的聚合作用。同时，观察到形成低聚体的不同说明了Cu（Ⅱ）的催化聚合比Fe（Ⅱ）更加有效。而且，为了使以上实验现象得到合理的解释，提出了相应的配住物中间体作用机理。