Thermal and Rheological Properties of Poly(lactic acid)/Low-Density Polyethylene Blends and Their Supercritical CO<Subscript>2</Subscript> Foaming Behavior

Low-density polyethylene (LDPE) was employed to improve the thermal and rheological properties as well as the supercritical CO₂ foaming behavior of poly(lactic acid) (PLA) through melt mixing and batch foaming method, due to its long branched chain structure, moderate crystallization capacity and good foamability. The differential scanning calorimetry and polarized optical microscope results showed that the introduction of LDPE had a slight effect for promoting the crystallization of PLA. An important synergistic effect on the rheological properties of PLA/LDPE blends was found through rotational rheometer. With the content of LDPE, the size of spherical LDPE dispersion phase became bigger gradually, which was observed by scanning electron microscope (SEM). A very interesting cellular morphology evolution from flower-like cellular structure to complex cellular structure and then to mono-porous cell structure was found in the SEM images of the PLA/LDPE blending foams with the foaming temperature at 95 °C. The effect of blending ratio and foaming temperature on the cellular morphology and foaming parameters was investigated.     

The association between air pollutants and autism spectrum disorders

Autism spectrum disorders are a member of the pervasive developmental disorders (PDDs) that have been increasing dramatically since described by Leo Kanner in 1943. In the past decade, the number of epidemiological publications addressing air pollution exposures and autism has grown correspondingly, but the association is still unclear. Whether air pollutants play a causal role and which substances are related with autism requires further study. We systematically reviewed the literature from 2005 to 2016 in MEDLINE (National Library of Medicine), Web of Science, and PubMed and summarized the association between different air pollutants and autism. Furthermore, we further discussed the exposure time window and potential confounders that should be considered in the association analysis studies. Our objective is to summarize the association between different air pollutants and autism with literature, which has been published since 2005, and explore whether the exposure time window and potential confounders have influence on this association. These results could provide more comprehensive information about the association between air pollutants and autism and be helpful towards further validation study.

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五氧化二钒类Fenton降解邻苯二甲酸二乙酯的机制研究

发展了基于五氧化二钒(V_2O_5)和过氧化氢(H_2O_2)的新型类Fenton体系,探索了此体系产生羟基(·OH)的机制及降解邻苯二甲酸二乙酯(DEP)的效率;并考察了V_2O_5投加量、H_2O_2浓度,以及草酸对DEP降解的影响。结果表明,当V_2O_5投加量为0.1 g·L-1,H_2O_2浓度为2.0 mmol·L-1,反应24 h后,对DEP(25 mg·L-1)的降解率可达61.1%,增加或降低V_2O_5投加量和H_2O_2浓度均不利于DEP的降解。利用电子顺磁共振技术(Electron Paramagnetic Resonance,EPR)耦合5,5-二甲基-1-吡咯啉氮氧化物(DMPO)为捕获剂对反应体系中的主导自由基进行鉴定,发现·OH是体系降解DEP的主要活性物种,利用苯甲酸作为探针分子实现了·OH的间接定量,并初步推测了V_2O_5活化H_2O_2的过程。     

Antimicrobial activities of flavonoids against bamboo-destroying fungi and molds

It is well-known that Poria vaporaria (Pers.:Fr.) Cooke, Paecilomyces variotii Bainier and Aspergillus niger are fungi and molds which destroy bamboo. The aim of this study was to compare the effectiveness of antibacterial activity of 16 flavonoids in preventing the actions of these three bamboo-destroying fungi and molds (Poria vaporaria (Pers.:Fr.) Cooke, Paecilomyces variotii Bainier and Aspergillus niger). The results showed that baicalein(1) exerted the highest inhibitory effect on Poria vaporaria (Pers.:Fr.) Cooke and Paecilomyces variotii Bainier indicating that baicalein(1) may be considered as a potential agent to develop as natural bactericide to preserve natural bamboo.     

固体试剂快速测定水中阴离子表面活性剂

对亚甲蓝分光光度法进行改进,用固体试剂快速测定水中的阴离子表面活性剂。在最大吸收波长652nm处,阴离子表面活性剂质量浓度为0~2.0m g/L时遵守比尔定律,表观摩尔吸光系数为1.56×104L/(m o.lcm),检出限为0.03m g/L。该方法用于自来水、河水和工业废水中阴离子表面活性剂的测定,取得了满意结果。环境水样的平均回收率为88.3%~108.0%,相对标准偏差不超过4.67%。     

鸡粪卫生无害化处理技术研究

利用2级厌氧处理实验,为中小型养鸡场的鸡粪处理提供了一种处理工艺和新的一体化装置,特别研究了鸡粪卫生无害化处理方法.实验在HRT为3.01 d,有机负荷7.85kg COD/m3·d的条件下,COD去除率达到了75.77%,COD产气率0.381 m3/kg COD·d,出水卫生指标符合国标要求.     

Spatial distribution and potential ecologic risk assessment of heavy metals in the sediments of the Nansi Lake in China

The contamination levels and ecological risks of heavy metals in the sediments of the Nansi Lake were investigated. The contents of Cd, Cr, Cu, Pb, Zn, Ni, and Co in the surface sediments collected at 20 sites ranged from 0.08 to 1.12, 58.92 to 135.62, 38.09 to 78.65, 24.51 to 53.95, 110.51 to 235.36, 11.30 to 65.40, and 4.12 to 20.14 mg/kg, respectively. The results of partitioning analysis revealed that the proportions of soluble and exchangeable fraction were less than 1 %, the proportions of carbonate, amorphous oxides, organic matter, and crystalline oxides fraction were less than 10 %, and 10.52 % of Cd was associated with carbonate. The average proportions in the residual fraction ranged from 48.62 % for Cu to 73.76 % for Ni, indicating low mobility and bioavailability. The geoaccumulation index (I _geo), relative enrichment factor (REF), sediment pollution index (SPI), and potential effect concentration quotient (PECQ) values of the heavy metals in the sediments were not in agreement with each another. The average REF values of Cd and Zn were higher than those of other metals. However, the average PECQ values were higher for Cr and Ni than those of other metals, indicating that these two metals would cause higher adverse biological effects. Therefore, it is suggested that future management and pollution control might focus on Cd, Zn, Cr, and Ni in the sediments of the Nansi Lake.     

塔里木河流域水质变化趋势分析

应用季节性肯达尔非参数检验方法,对塔里木河干流及三大源流１９９２－１９９８年间的水质变化趋势进行了分析检验,客观、定量地描述了塔里木河的水质变化动态,对于进一步掌握塔里木河的水质变化有着重要意义。     

Factors regulating trophic status in a large subtropical reservoir, China

We evaluated a 4-year data set (July 2003 to June 2007) to assess the trophic state and its limiting factors of Three-Gorges Reservoir (TGR), China, a large subtropical reservoir. Based on Carlson-type trophic state index (TSI)_CHL, the trophic state of the system was oligotrophic (TSI_S?< 40) in most months after the reservoir became operational, although both TSI_TP and TSI_TN were higher than the critical value of eutrophic state (TSI_S?>?50). Using Carlson’s (1991) two-dimensional approach, deviations of the TSI_S indicated that factors other than phosphorus and nitrogen limited algal growth and that nonalgal particles affected light attenuation. These findings were further supported by the significant correlation among the values of TSI_CHL ? TSI_SD and nonvolatile suspended solids and water residence time. The logarithmic model showed that an equivalent TSI_CHL and TSI_SD could be found at τ?=?54 days in the TGR (Fig. 7). Accordingly, nonalgal particulates dominated light attenuation and limited algal biomass of the reservoir when τ?<?54 days.     

Enhanced anthropogenic heavy metal dispersal from tidal disturbance in the Jiaozhou Bay, North China

Heavy metal contamination in surface sediments of the Jiaozhou Bay was investigated in this study. Sediment sample was collected from the Jiaozhou Bay and its rivers. Heavy metal concentration was determined by inductively coupled plasma atomic emission spectroscopy and graphite furnace atomic absorption spectrometry. The result shows that river sediment in the east coast of the Jiaozhou Bay was heavily polluted especially for the Cu, Pb, Cd, and Zn. A slightly increase of heavy metal concentration was observed at stations near the east coast in the Jiaozhou Bay; however, contaminated sediment from polluted river was constrained mostly near shore within 3–4 km. Downstream decrease of heavy metals in river mouth suggested dilution from strong tidal current. Rapid seaward decline in the east coast and alongshore band dispersal pattern of heavy metals in surface sediment indicated mixing and remobilizing enhanced by large tidal range that regulated dispersal of sediments and anthropogenic heavy metals in the Jiaozhou Bay area.