紧急启动及停炉后增压锅炉热防护砖衬结构的强度分析

针对船用增压锅炉在频繁启、停炉过程中,热防护砖衬结构中的耐火材料易出现的断裂、脱落等问题,采用有限元分析法对热防护砖衬结构进行强度校核,分析出现损伤的结构部件及耐火材料发生断裂的原因,对增压锅炉的安全使用与预防损坏具有一定的参考意义。     

天灾死亡人数不再是国家机密

近年来灾情数字已逐步公开 根据形势发展和救灾工作的需要,从2005年8月起,我国对全国及省、自治区、直辖市因自然灾害导致死亡人员的总数及相关资料解密。     

模拟成藏地质填埋及诱导填埋有机质生气的理论初探

填埋处理和垃圾生物气的开发利用是实现城市生活垃圾资源化、无害化、减量化处理的有效途径,引入模拟生物气成藏和含气系统的思路,开展地质填埋与诱导填埋有机质生气研究是对能源地质学和填埋设计理念的新探索.通过对比研究地质填埋结构与地质学中生物气藏系统的异同点、生气机理和影响因素的共性与差异,初步论证了将模拟生物气藏理论引入地质填埋设计、优化地质填埋结构、提高填埋有机质生物气化效率和抽排利用效率的可行性;探讨了生物气藏理论在构建地质填埋结构中的可能应用和启示.研究表明:模拟生物气藏地质填埋设计和非常规生物气开发理念具有理论依据和现实基础;生物气藏生、储、盖要素和运、圈、保过程的模拟可应用于垃圾地质填埋场的构建,微生物地球化学理论有助于对诱导填埋有机质生气条件优化的认识.     

Distribution,fractionation and risk assessment of mercury in surficial sediments of Nansi Lake,China

Nansi Lake is composed of four sub-lakes from north to south: Nanyang Lake, Dushan Lake, Zhaoyang Lake and Weishan Lake. An environmental pollution investigation was carried out to determine the fractionation, and pollution assessments of mercury (Hg) in surficial sediments from Nansi Lake. Results showed that the mean concentration of Hg was 3.1 times higher than its background value (0.015 mg kg^?1), and the high concentration of Hg which even reached up to five times than the background value in the part of Dushan Lake and Weishan Lake, which indicated that there are obvious spatial differences. The content of Hg was positively correlated with that of total organic carbon, and negatively correlated with that of pH and SiO₂ in surface sediments. An improved Tessier sequential extraction procedure was used to study the fractions of Hg in sediments. The results indicated that Hg existed primarily in the fraction of residual, which accounts for 58.4% of total mercury (THg), and the percentage of extractable Hg was only 1.93% of total mercury. High concentrations of mercury of non-residual phase were found in part lake area from the Nanyang Lake and the Weishan Lake, which indicating a higher potential ecological risk relative to the other lake areas. Based on the values of enrichment factor and geo-accumulation index, most part of Dushan Lake and Nanyang Lake and Weishan Lake were in a moderate pollution. And based on the fractionation of mercury, risk assessment code of Hg exhibited low risks to the environment in Nansi Lake.     

Evaluation on exposures to particulate matter at a junior secondary school: a comprehensive study on health risks and effective inflammatory responses in Northwestern China

Air pollutant measurement and respiratory inflammatory tests were conducted at a junior secondary school in Xi’an, Northwestern China. Hazardous substances including particulate matters (PMs), black carbon (BC) and particle-bounded polycyclic aromatic hydrocarbons (PAHs) were quantified both indoors and outdoors of the school. Source characterization with organic tracers and particle-size distribution demonstrated that the school’s air was mostly polluted by combustion emissions from the surrounding environment. The evaluation of health assessment related to air quality was conducted by two methods, including potential risk estimation of air pollutants and direct respiratory inflammatory test. The incremental lifetime cancer risks associated with PAHs were estimated and were 1.62 × 10⁻⁶ and 2.34 × 10⁻⁶, respectively, for indoor and outdoor fine PMs. Both the values exceeded the threshold value of 1 × 10⁻⁶, demonstrating that the carcinogenic PAHs are a health threat to the students. Respiratory inflammatory responses of 50 students who studied in the sample classroom were examined with a fractional exhaled nitric oxide (FeNO) test, with the aid of health questionnaires. The average FeNO concentration was 17.4 ± 8.5 ppb, which was slightly lower than the recommended level of 20 ppb established by the American Thoracic Society for children. However, a wide distribution and 6% of the values were > 35 ppb, suggesting that the potentials were still high for eosinophilic inflammation and responsiveness to corticosteroids. A preliminary interpretation of the relationship between air toxins and respiratory inflammatory response demonstrated the high exposure cancer risks and inflammatory responses of the students to PMs in the city.

     

Cloning and expression of RING-finger E3 ubiquitin ligase CsSDIR1 gene in tea plant (Camellia sinensis)北大核心CSCD

Protein ubiquitination regulates many aspects of plant development and stress response. The RING-finger type E3 ubiquitin ligase SDIR1 (salt and drought induced ring finger 1) gene plays a key role in plant stress response. In this study, the full-length cDNA and the promoter sequences of CsSDIR1 were isolated from tea plants using the RT-PCR technology, and its bioinformatics characteristics were systematically analyzed. The expression patterns of CsSDIR1 in various tissues and in response to cold, drought, salt, and ABA treatments were also investigated by quantitative real-time RT-PCR (qRT-PCR). The sequence of CsSDIR1 contains a complete open reading frame of 831 bp, coding for a 276-long amino acid protein with a molecular weight of (Mr) 30.085 × 103 and a theoretical isoelectric point of 6.54. CsSDIR1 was predicted to be a hydrophobic protein localized on the intracellular membranes. The analysis of the amino acid sequence characteristics showed that CsSDIR1 contains two putative transmembrane domains at the N-terminus and a C3H2C3 RING-finger domain at the C-terminus; it shares high similarity with other plants' SDIR1, and has the closest relationship to Actinidia sinensis. A cis-acting regulatory elements prediction showed that the CsSDIR1 promoter contains many cis-acting elements, especially drought and salt stress response elements. The qRT-PCR analysis indicated that the CsSDIR1 gene has a high expression level in stems, followed by roots, leaves, and flowers; the expression of the CsSDIR1 gene is up-regulated by ABA, salt, and drought treatments, whereas it is down-regulated in response to cold stress. These results demonstrated that the CsSDIR1 gene might be involved in the plant stress response of tea trees. © 2018 Science Press. All rights reserved.     

Discovery of novel halogenase genes using sequence-driven metagenomics approach北大核心CSCD

It is of great significance to ability to obtain new natural products with diverse activities through the study of soil microorganisms. However, less than 1% of the total soil microorganisms can be cultured under laboratory conditions, thus limiting the discovery of new compounds. Metagenomics, by which the genomic DNA of soil microorganisms can be extracted and expressed in heterologous hosts, provides a new approach for the functional study of soil microorganisms. Natural halides have good bioactivities, including antibacterial and antitumor activities. Halogenases play an important role in biosynthesis, and introducing bioactivities of halogenated compounds. To investigate the potential of halogenated compounds production from soil microorganisms, a soil metagenomic library was screened by PCR for clones harboring reduced flavin adenine dinucleotide (FADH2) - dependent halogenase genes. Sixty-five positive clones were identified from the library, and the amino acid sequences of halogenase genes within the positive clones were analyzed. Phylogenetic analyses revealed that more than 85% of these genes were separated from known halogenases to form new clades in the phylogenetic tree; moreover the soilderived halogenases showed high diversity. By further biosynthetic gene analysis of the positive clones, a new type I polyketide biosynthetic gene sequence was identified, which is probably related to the biosynthesis of the halogenated type I polyketide. In conclusion, novel and diverse halogenase genes were identified on sixty-five metagenomic clones using a sequence-driven metagenomic approach, laying a foundation for the further discovery of novel natural halides biosynthetic gene clusters and halides. © 2018 Science Press. All rights reserved.     

Discovery of nano-sized gold particles in natural plant tissues

Biological effects of nanoparticles have attracted widespread attention. However, the interaction between plants and nanoparticles remains unclear. The purpose of this study was to investigate characteristics of nano-sized metal particles in two representative plant species, Erigeron canadensis and Boehmeria nivea, in the Guangdong Province, China. The stems of the plants were sliced and placed on Ni–C grids for field-emission transmission electron microscopy (TEM). The metal-bearing nanoparticles were further analysed for their size, shape, composition, content and other characteristics using X-ray energy spectrum analysis, scanning TEM and selected-area electron diffraction pattern. The results revealed that the plants contain nano-sized Au-bearing particles with a diameter of 5–50 nm, ellipsoid, spherical and bone-rod shapes or irregular morphology with smooth edges. These nanoparticles primarily consisted of Au, Cu, O and Cl. The discovery of Au-bearing nanoparticles in natural plant tissues is of great significance for biological nanoscience. Here, we discuss the function and absorption mechanism of Au-bearing nanoparticles in plants and present the influence of the discovery of Au-bearing nanoparticles in natural plants.     

Effects of source size,monitoring distance and aquifer heterogeneity on contaminant mass discharge and plume spread uncertainty

Estimating the movement of dissolved contaminants in heterogeneous aquifers is very important for the monitoring design, risk assessment, and remediation of contaminated aquifers. This work explored the influence of source size, monitoring distance, and aquifer heterogeneity on the accuracy of contaminant mass discharge (CMD) estimation using leaching surface approach as well as on the plume spread uncertainty in a 2-D heterogeneous aquifer. The interaction among source size, monitoring distance, and aquifer heterogeneity regarding the accuracy of CMD estimation and the plume spread uncertainty at downstream of the contaminated aquifer was extensively investigated. The transient leaking of a contaminated aquifer in a saturated heterogeneous aquifer under steady-state flow conditions was simulated. The effect of aquifer heterogeneity on the CMD uncertainty was evaluated through the expected values and variance. The results showed that the CMD estimation error varied from underestimation in the mildly heterogeneous aquifer, over accurate estimation in the medium heterogeneous aquifer to overestimation in the highly heterogeneous aquifer. Additionally, the results illustrated that the mean and variance of the transverse spatial extent of the peak concentrations for the plume at the control plane were very sensitive to the aquifer heterogeneity and detectable concentrations of contaminants.     

邻苯二甲酸酯的环境污染和生态行为及毒理效应研究进展

邻苯二甲酸酯作为产品改性剂被广泛应用于食品包装、建筑板材、医疗器械等产品中,由于PAEs与塑料分子难以形成强力的共价结合,造成其不断泄露至脂溶性环境中,在基质接触和食物网传递作用下,PAEs被各种生物体蓄积并表现出一定的内分泌干扰效应。文章以PAEs的物化性质及其在大气、水体、土壤中的污染现状为研究基础,介绍了PAEs的生物体蓄积水平与代谢路径,并分别从水解、光解及生物降解3个角度展示了PAEs的环境降解过程与机理;此外,结合实验室报道及社会调查,深入探讨了PAEs的环境激素效应,"致癌、致畸、致突变"效应,酶与激素毒性;最后,基于当前PAEs在毒理分析、降解途径及环境暴露统计研究上的不足,指出需进一步进行复杂食物链毒性积累与放大研究,发展PAEs的生物治理与削减技术以及进行PAEs环境暴露水平调查,确定全面合理的环境标准限值。