Bacterial degradation of monocrotophos and phyto- and cyto-toxicological evaluation of metabolites

The bacterium Serratia marsescens strain JAS16 was isolated from agricultural soil which had prior exposure to monocrotophos for three years. The strain JAS16 tolerated up to 1200 mg L^–1 monocrotophos and degraded the insecticide (1000 mg L^–1) at a degradation rate constant of 136 d^?1 (DT₅₀ = 3.7 d). In soil, the degradation rate constant was 105 d^?1 (DT₅₀ = 4.8 d). A schematic pathway is being proposed from the degraded products derived from gas chromatography--mass spectrometry (GC-MS). The phytotoxicity of degradation products to Vigna radiata, Vigna unguiculata, and Macrotyloma uniflorum and the genotoxicity to Allium cepa roots were found to be low. A cost-effective powder-based formulation was achieved with the isolate. The isolate remained viable during the storage and also multiplied with a higher colony forming units (CFU) load g^–1 for over a period of seven weeks of storage.     

重庆三叠系碳酸盐岩热储热水水文地球化学特征

地下热水的水文地球化学特征研究有利于地下热水的开发,对重庆三叠系碳酸盐岩热储热水的研究可以更好地实现重庆地下热水的可持续开发。通过2009年1月和2009年7月对重庆市三叠系碳酸盐岩热储热水进行野外监测、取样和室内分析,发现重庆三叠系碳酸盐岩热储热水水化学性质相近,pH呈中性,水温30℃~50℃,电导率为1 320 μs/cm~3 250 μs/cm,水化学类型为SO₄-Ca(Mg)型,是典型的碳酸盐岩热储中-低温地下热水。温泉水的主要阳离子为Ca²⁺和Mg²⁺,阴离子为SO₄^2-和HCO₃^-,除青木关温泉外,SO₄^2-和Ca²⁺、Mg²⁺随时空变化较小,体现了碳酸盐岩中石膏与地下热水的水-岩作用对地下热水水文地球化学特征的控制。热水中的方解石和白云石都处于饱和与不饱和的临界状态,没有明显钙华沉积的现象;Na-K-Mg-Ca图解显示各个季节地下热水的物质来源基本一致,均没有达到水岩平衡状态。     

不同磁黄铁矿自养反硝化脱氮除磷作用

氮磷排放标准日趋严格,开发高效廉价脱氮除磷材料已成为研究热点.采用黄铁矿与赤铁矿在管式炉中氮气气氛下600 ℃煅烧,得到硫化赤铁矿形成的磁黄铁矿、黄铁矿热分解形成的磁黄铁矿,构建磁黄铁矿-方解石体系处理含氮磷模拟废水,对比不同方式制备的磁黄铁矿、天然磁黄铁矿、黄铁矿、硫磺脱氮除磷性能,考察不同磁黄铁矿晶体结构和结晶度差异及其对脱氮除磷影响,探究不同体系中矿物结构和微生物群落变化.结果表明：黄铁矿热分解产物以六方磁黄铁矿为主;硫化赤铁矿产物以低结晶度的单斜磁黄铁矿为主,因而表现出优异的脱氮除磷活性,氮磷去除率分别为99.8%和96.8%.铁硫化物与微生物反应产物的XRD、SEM和FE-TEM分析结果表明,微生物能有效利用磁黄铁矿进行脱氮,磷酸盐主要以FePO₄形式被去除.群落分析结果表明铁硫化物脱氮除磷体系中的主要功能菌属为Thiobacillus和 Sulfurimonas,结晶度低的单斜磁黄铁矿更有利于Thiobacillus定向富集.     

焊接工艺多源散发的高温颗粒污染物扩散特性数值模拟

为探究热工艺过程产生的热气流作用下颗粒的迁移规律,基于气固两相离散粒子模型(DPM)对多源浮射流伴生的高温颗粒的扩散特性进行了数值研究,讨论了两相流运动过程中热气流与颗粒群的温度和速度的瞬时变化情况.结果表明,对于473K£T₀£673K的高温颗粒群,温度衰减趋势类似,颗粒群温度分布呈中心对称;当5μm£d_p£20μm时,颗粒与气流之间的跟随性随着粒径的增大而降低;热羽流随时间经历了独立发展和相互合并的过程,羽流之间涡旋结构的消失导致中心位污染源散发的d_p=10μm的颗粒更容易发生沉降.     

Biofilm-overproducing Bacillus subtilis B12ΔYwcc decreases Cd uptake in Chinese cabbage through increasing Cd-immobilizing related gene abundance and root surface colonization

Biofilm-producing bacteria can decrease Cd uptake in vegetables, but mechanisms underlying this effect are poorly characterized. In this study, two mutant strains B12ΔYwcc and B12ΔSlrR were constructed from a biofilm-producing Bacillus subtilis strain B12. Then, the impacts of strain B12 and its high biofilm-producing mutant strain B12ΔYwcc and low biofilm-producing mutant strain B12ΔSlrR on Cd availability and uptake in Chinese cabbage and the related mechanisms were investigated in the Cd-polluted soil. Strain B12 and its mutants B12ΔYwcc and B12ΔSlrR increased the dry biomasses of edible tissues by 54%–130% compared with the controls. Strain B12 and its mutant B12ΔYwcc reduced the soil available Cd content by 36%–50% and root and edible tissue Cd contents by 23%–50% compared with the controls. Furthermore, the mutant strain B12ΔYwcc reduced the edible tissue Cd content by 40% and increased the polysaccharide content by 23%, invertase activity by 139%, and gene copies of the cumA by 4.5-fold, epsA by 7.1-fold, and cadA by 4.3-fold, which were involved in Cd adsorption in the rhizosphere soils, respectively, compared with strain B12. The polysaccharide content and cumA, epsA, and cadA gene copy numbers showed significantly reverse correlations with the available Cd content. Notably, the mutant strain B12ΔYwcc showed better ability to colonize the vegetable root surface than strain B12. These findings demonstrated that the biofilm-overproducing mutant strain B12ΔYwcc increased the polysaccharide production and Cd-immobilizing related cumA, epsA, and cadA gene copies, resulting in lower Cd availability and accumulation in Chinese cabbage in the Cd-polluted soil.     

焙烧炉筒体结构强度有限元分析

对焙烧炉筒体结构进行有限元建模仿真,考虑热应力、压力和重力对筒体结构受力的影响,计算了焙烧炉关键部位的蠕变疲劳寿命,同时探究进气温度、保温层及对流系数等参数的影响。结果表明:热应力是影响结构强度的关键因素;焙烧炉筒体在许用蠕变变形量为5%的情况下,其使用寿命超过设计寿命;在筒体加热过渡段铺设保温层,降低与外界空气对流和提高进气温度,有利于降低筒体应力。     

SiO2气凝胶隔热性能的影响因素研究

目的 在不同热流条件下,通过调整SiO2气凝胶的孔隙率、涂层厚度等,以满足合适的隔热要求。方法 针对中短程飞行器飞行时外壁面承受短时高热流的特点,在分析孔隙率对SiO2气凝胶热导率影响规律的基础上,通过数值仿真研究不同气凝胶孔隙率、气凝胶厚度及热流作用下的温度响应。结果 得到了不同条件下满足隔热要求的气凝胶最小厚度,以及气凝胶表面的最高温度。高温情况下,气凝胶孔隙率为96%时,有效热导率最低,孔隙率超过96%时,隔热性能变差。结论 当飞行器内壁面温度满足要求时,增大气凝胶的孔隙率,则需要减小气凝胶的厚度,相应的气凝胶表面温度会升高,但升幅很小。当飞行器外壁面承受长时间大热流时,仅调整气凝胶的厚度和孔隙率不能达到结构的隔热要求。     

Creating False Images: Stream Restoration in an Urban Setting

Stream restoration has become a multibillion dollar business with mixed results as to its efficacy. This case study utilizes pre‐ and post‐monitoring data from restoration projects on an urban stream to assess how well stream conditions, publicly stated project goals, and project implementation align. Our research confirms previous studies showing little communication among academic researchers and restoration practitioners as well as provides further evidence that restoration efforts tend to focus on small‐scale, specific sites without considering broader land use patterns. This study advances our understanding of restoration by documenting that although improving ecological conditions is a stated goal for restoration projects, the implemented measures are not always focused on those issues that are the most ecologically salient. What these projects have accomplished is to protect the built environment and promote positive public perception. We argue that these disconnects among publicized goals for restoration, the implemented features, and actual stream conditions may create a false image of what an ecologically stable stream looks like and therefore perpetuate a false sense of optimism about the feasibility of restoring urban streams.     

探讨ADC芯片引脚与印制板之间的固封方式

通过故障分析,将某产品高温老炼试验过程中发生的性能异常现象定位于ADC芯片部分引脚焊点脱焊。为验证芯片引脚与印制板之间的固封方式对焊点受力的影响,分别对"底部灌封+四角固封"及"底部灌封+四边固封"固封方式进行试验验证及随机振动、热应力分析。根据分析结果,高温浸泡时"底部灌封+四边固封"方式下,焊点受力均匀,最大热应力低于3MPa;而"底部灌封+四角固封"固封方式下的焊点最大热应力约5.1MPa,导致了焊点的蠕变疲劳失效。为减少高温浸泡时焊点的热应力,设计了"底部不灌胶,四边固封但一角不封口"的固封方式,并顺利通过相应的验证试验,证明这是一种较为妥当的固封方式。     

变压器发热试验自动测试平台的开发

研究开发了变压器认证标准GB19212．1（IEC 61558－1）中发热试验项目的自动测试平台,详细叙述了试验操作过程、自动测试平台的软硬件结构,继电器控制模块组成与硬件设计,以及虚拟仪器软件实现流程。该平台可显著减少检测人员的在线工作时间,并行测试可提高设备使用率,同时相比之前的手动测试,可明显降低人工测量部分的不确定度。