基于改进灰色模型的管壁蜡沉积厚度预测研究

为对含蜡原油管道中的蜡沉积厚度进行准确预测,在函数cot(x2)变换的基础上,结合平移变换思想,利用cot(x2+c)变换建立新的改进GM(1,1)模型。以现场管道结蜡数据和室内环道结蜡数据为例,对比改进GM(1,1)模型、基于函数cot(x2)变换建立的GM(1,1)模型及传统GM(1,1)模型之间的预测精度,并分析平移量c对改进GM(1,1)模型预测精度的影响。结果表明:改进GM(1,1)模型的预测精度最高,其次是基于函数cot(x2)变换建立的GM(1,1)模型,而传统GM(1,1)模型的预测精度最低;随着平移量的增大,改进GM(1,1)模型的平均相对预测误差呈现出先减小后增大的趋势,因此合理的平移量有助于模型精度的提高。应用改进GM(1,1)模型来预测管道蜡沉积厚度是可行的,该方法可为含蜡原油管道蜡沉积厚度的准确预测提供参考和借鉴。     

大同矿区煤的导热系数灰色关联分析及预测

为分析煤质指标及密度对导热系数的影响作用,选取了山西大同矿区的不同煤质煤样,进行导热系数测定实验,应用灰色系统理论对导热系数与影响因素进行灰色关联分析,建立导热系数与主要影响因素的GM(1,4)灰色预测模型,进行导热系数预测。结果表明:固定碳、密度和水分是影响煤导热系数的主要因素;根据得出的主要影响因素建立的GM(1,4)预测模型平均相对误差为4.5%,预测精度较高,能够用于导热系数的预测。     

基于GM-SVR的小样本条件下化工设备可靠性预测

为了准确预测化工设备可靠性趋势，针对化工设备失效寿命数据为小样本的情形，基于灰色估计法与支持向量回归机在小样本数据处理中的优势，建立了失效寿命时间服从三参数威布尔分布的化工设备可靠性模型；结合GM（1，1）和SVR对模型进行参数估计，在压缩机可靠性分析中进行了实例应用，对比分析了最小二乘法、灰色估计法和GM-SVR的估计效果。研究结果表明:GM-SVR对威布尔分布参数的估计精度明显优于最小二乘法和灰色估计法，可以有效地应用于化工设备失效数据为小样本时的可靠性预测。     

基于G1-VPRS-MIE多层次灰色理论的引水明渠运行风险评价

引水明渠的安全运行风险评价对减少和预防其在输水运行过程中的灾害发生、提高其在运营期间的社会经济效益具有重要的意义。为了对引水明渠在运行期间的风险进行合理赋权和评价,通过科学合理的方法构建了多指标参数的明渠运行风险影响因素指标体系,包括主体结构风险、自然风险、水污染风险、组织管理风险和运行调度风险5个风险因子子系统及20个二级指标在内的评价指标体系;运用G1和VPRS法分别确定各指标的主观权重和客观权重,结合MIE理论优化指标权重;根据明渠工程的运行特点,选取多层次灰色理论计算引水明渠运行风险值,并根据相关规范和安全风险评价实践确定风险评价等级。将该模型应用于引大入秦工程中,结果表明:采用序关系分析法(G1法)和变精度粗糙集理论(VPRS)并结合最小信息熵原理(MIE)的权重确定方法(G1-VPRS-MIE),不但避免了层次分析法过度依赖专家的主观经验、克服了粗糙集理论在边界刻画的局限性,而且弥补了主观和客观方法相结合的不足;对于指标权重的确定更加客观合理,既能满足所得权重的客观性,也能保证评估结果具有一定的解释性,同时能够减少单一权重计算的偏差;多层次灰色评价模型对于引水明渠安全运行风险等级的确定较为有效,并得出其风险等级为中等偏高,与实际情况一致。研究成果为引水明渠工程安全运行提供了一定的参考,同时可为类似气候环境的引水明渠区域规划、设计、施工提供有效的借鉴。     

亚硝酸盐型甲烷厌氧氧化微生物特性研究进展

亚硝酸盐型甲烷厌氧氧化(nitrite-dependent anaerobic methane oxidation,N-DAMO)是新近发现的生物反应,是偶联碳氮循环的关键环节,是环境领域和微生物领域的重大发现.N-DAMO的发现对于完善碳氮生物地球化学循环、丰富微生物学内容和研发新型生物脱氮除碳工艺均具有巨大的推动作用.催化N-DAMO反应的微生物为Candidatus Methylomirabilis oxyfera(M.oxyfera),其隶属于一新发现的细菌门——NC10门.近年来,M.oxyfera的生物学研究取得了许多突破性进展,如初步探明了其个体形态特征、细胞化学组分特征、富集培养特征、生理生化特征及生态学特征,最突出的例子包括发现了M.oxyfera独特的细胞(星状)形态及特殊的脂肪酸(10Me C16∶1Δ7)组分等.最近,N-DAMO的机制研究方面也有了突破性进展:发现了地球上第4种生物产氧途径.目前认为,M.oxyfera具有内产氧功能,其首先将NO-2还原为NO,然后将2分子NO进行歧化反应生成N2和O2,最后利用生成的O2对甲烷进行氧化.本文系统地介绍了M.oxyfera各方面的微生物特性.     

Determination of aflatoxin-B1 in poultry feed and its components employing enzyme-linked immunosorbent assay (ELISA)

A highly sensitive enzyme immunoassay was standardized for aflatoxin B₁ determination in poultry feed and its components using Riedel-de-Haen, ELISA Systems_. A microtitration plate method was optimized using anti-aflatoxin B₁ antibodies and peroxidase – aflatoxin B₁ conjugate, based on competitive enzyme immunoassay principle. Standards of concentrations of 5, 10, 20, 50, 100, 500?ng/L aflatoxin B₁, prepared in phosphate-buffered saline, were used. Standard curves showed that as the concentration of antigen decreased, absorbance values increased. Fifty percent inhibition was observed at 37?ng/L. Regression analysis showed that log concentration was inversely related to %B/B₀, with a highly significant negative correlation (?0.980). The lowest detection limit for aflatoxin B₁ was 5?ng/L. Using this standardized ELISA, aflatoxin B₁ was detected in most of the commercially available poultry feed samples and their components.

The data suggest that this test is suitable for the accurate determination of aflatoxin B₁ concentrations in poultry feed and its components.     

α1-Microglobulin levels and correlation with cadmium and other metals in urine of non-smoking women among general populations in Japan

The present study was initiated to examine urinary α₁-microglobulin (α₁-MG-U) levels among non-smoking women in the general population in Japan. A previously established database on spot urine samples from adult woman volunteers in 10 non-polluted areas all over Japan was re-examined. The data examined were on α₁-MG-U, cadmium, calcium, magnesium and zinc levels in urine (Cd-U, Ca-U, Mg-U and Zn-U, respectively), urinary creatinine (CR or cr), urine specific gravity (SG or sg), smoking habits and age. Thus, 8975 never-smoking women were selected for statistical analyses. The grand geometric mean (GM) for α₁-MG-U among the population was 2.1?mg/L or 2.5?mg/g?cr, depending on the correction for urine density. It was 1.1?µg/L or 1.3?µg/g?cr for GM Cd-U. The inter-area difference in α₁-MG-U was <1.5?mg/g?cr or <0.7?mg/L; the area with the highest or lowest GM Cd-U was not always highest or lowest in GM α₁-MG-U. The correlation coefficient (0.53) between log?Cd-U and log?α₁-MG-U (both without urine density correction) became substantially smaller when the analyte levels were corrected for CR (0.25) or SG (0.26). In multiple regression analysis, the power of influence of the five independent variables (log?Cd-U, Ca-U, Mg-U, Zn-U and age) in combination was small (R ²?≦?0.13). In contrast, logistic regression analysis suggested that α₁-MG-U might be elevated as a function of an increase in Cd-U, depending on the cut-off values. Discussion was made on dose (Cd-U_cr) and response (α₁-MG-U_cr) relationship based on information available in literatures to show that the increment in α₁-MG-U_cr per Cd-U_cr was much greater when Cd-U_cr was large, e.g., in excess of 10?µg/g?cr.     

Decolorization and degradation of acid dyes mediated by salt fractionated turnip ( Brassica rapa ) peroxidases

Peroxidases from turnip roots (524?U?g^?1 of vegetable) were highly effective in decolorizing acid dyes having wide spectrum chemical groups. Dye solutions, containing 40–170?mg?dye?L^?1, were treated by turnip peroxidases (TP) (specific activity of 122.0?U?mg^?1 proteins). These enzymes were able to decolorize most of the acid dyes in the presence of 2.0?mM 1-hydroxybenzotriazole (HOBT). Increasing concentration of enzyme and time in the absence of HOBT did not influence dye decolorization. The rate of decolorization was significantly enhanced when HOBT was added to the decolorizing solutions. The decolorization of all the used dyes was maximum at pH 5.0 and 40°C. Complex mixtures of dyes were significantly decolorized when treated with enzyme in the presence of HOBT (2.0?mM). Phytotoxicity test based on Allium cepa root growth inhibition has shown that majority of the TP-treated dye product were not more toxic than their parent dye. Kinetic parameters of the TP with various dyes showed that this enzyme has highest affinity for Acid Yellow 42. This study demonstrates that the peroxidase/mediator system was an effective biocatalyst for the treatment of industrial effluents from textile, dye manufacturing, dyeing and printing industries or complex mixtures of dyes.     

Spore inhibition-based enzyme substrate assay for monitoring of aflatoxin M1 in milk

A spore germination-based concept and its transformation into a field level prototype for monitoring aflatoxin M₁ (AFM₁) in milk was developed. Initially, 15 strains of Bacillus spp. procured from different culture collection were screened for AFM₁ sensitivity using spot assay and marker strain showing inhibition at 0.5 ppb was selected based upon maximum zone of inhibition. The selected strain B. megaterium 2949 was further screened for different enzymes activities and subsequently its spores were produced to an extent of 73.13% ± 3.197% in newly developed sporulation medium containing beef extract (0.0075% ± 0.0004%), yeast extract (0.015% ± 0.001%), peptone (0.0375% ± 0.0016%), and sodium chloride (0.0375% ± 0.0018%). A spore germination-based concept/ assay was optimized by immobilizing spores in eppendorf with pretreated milk (80°C/15 min) containing germinant and chromogenic substrate followed by incubation at 37°C. The appearance of sky blue color within real time of 45 min indicated spores germination and release of specific marker enzyme such as acetyl esterase and its specific action on chromogenic substrate which demonstrates absence of AFM₁ in milk. However, if there was no color change, presence of AFM₁ at 0.5 ppb MRL was denoted by Codex. The developed concept on AFM₁ detection was validated and a correlation of 0.97 was established with AOAC approved Charm 6602 and ELISA at Codex MRL with minimal false positive and negative results. The cost effective test has potential application in dairy farms, manufacturing, and R&D units for routine monitoring of AFM₁ in milk.     

Oxidative stress and genotoxicity of 1-methyl-3-octylimidazolium chloride on loach (Misgurnus anguillicaudatus)

This study was a preliminary step to evaluate the acute toxicity of 1-methyl-3-octylimidazolium chloride ([C₈mim]Cl) on loach (Misgurnus anguillicaudatus) by determining the effects on hepatic antioxidant enzyme activities and by the comet assay. The results showed that [C₈mim]Cl had acute toxicity at concentrations above 20 mg L^?1, inducing oxidative stress and genotoxicity on fish liver cells. In respect to enzyme activities, [C₈mim]Cl induced changes in the activities of superoxide dismutase, catalase, and glutathione content the livers of fish exposed at 20–80 mg L^?1. [C₈mim]Cl at the same exposure level caused a remarkable increase in malondialdehyde level. The comet assay indicated that [C₈mim]Cl at 20–80 mg L^?1 induced genotoxicity in liver cells. With increased exposure concentration and time, the two comet parameters trailing rate and tail moment were significantly increased, with significant differences (P < 0.05) observed between control group and each treatment group. The present study shows that ionic liquids can be a threat to the health of aquatic organism when accidentally released to aquatic ecosystems.