估算水电工程对生态系统生产力影响的一种方法

初级生产力是描述生态系统功能和稳定性的重要参数之一,但目前尚无定量估算水电工程占地对评价区生态系统初级生产力影响的适用方法。提出多个群落组成的生态系统加权平均净初级生产力的概念,用于定量估算水电站等各类工程占地对评价区生态系统净初级生产力的影响,并以川西某在建大型水电站的永久占地数据为例子,对方法的应用作了说明。该方法同时适用于评价水电或其他工程占地引起陆生和水生生态系统净初级生产力的变化。     

四川盆地高磨地区龙王庙组储层岩石流体概率识别技术

四川盆地高石梯—磨溪地区下寒武统龙王庙组气藏储层的岩性与流体性质地震识别难度较大,主要原因是不同岩性、不同流体性质地层的岩石物理参数往往存在着较大的重叠空间,由此增加了识别的不确定性与多解性。为破解上述难题,采用岩石流体概率识别技术进行了尝试。该方法首先依据岩石物理参数分析结果建立各种岩性、流体性质的概率分布函数,再根据联合求解来确定储层的岩性及流体性质的概率,以此开展岩性、流体性质识别。应用结果表明:较之于一般的叠前反演方法,该方法通过多弹性参数对的联合概率求解,既提高了对储层岩性、流体性质识别的精度,又为提高储层岩性、流体性质识别的可靠程度提供了量化依据,可以为油气藏勘探开发井位部署决策等提供更充足的量化参考指标和依据。     

水镁石纤维增强油井水泥石性能研究

分别对不同长度水镁石纤维油井水泥浆的流动性、API失水量、沉降稳定性进行了测试和分析;并讨论了纤维分散方式、加量范围、水泥石抗压强度、抗折强度、劈裂抗拉强度以及微观结构。结果表明,水镁石纤维能显著降低水泥浆体系流动性、使API失水量下降45%数50%,对水泥浆沉降稳定性的影响很小。水镁石纤维能显著提高水泥石的力学性能,水浴养护14 d后,3%纤维加量下的水泥石抗压强度提高16.2%,5%纤维加量下的水泥石抗折强度提高48.8%,8%纤维加量下的水泥石劈裂抗拉强度提高41.4%。通过机械剪切力和超声作用预分散处理后,水镁石纤维成细丝状均匀分布在水泥石中,能有效提高水泥石密实度和限制微裂纹发生与扩展。纤维的加入使得水泥石力学性能增益比显著增大,5%纤维加量水泥石的拉压比与空白试样相比提高27.5%,使得水泥石脆性得到较大改善。但高加量下水镁石纤维难分散、易团结,水镁石主要起填充作用,水泥石强度仍能得到一定的增加。     

油井水泥缓凝剂AID的合成与性能评价

针对目前常用的二元共聚物类水泥缓凝剂耐温性能差,及以丙烯酰胺(AM)为原料之一的三元共聚物类缓凝剂中AM易高温分解的问题,用N,N-二甲基丙烯酰胺(DMAM)取代AM,选取2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、衣康酸(IA)和DMAM等3种单体,根据自由基水溶液聚合原理,合成了三元聚合物类缓凝剂AID。通过凝胶色谱分析、红外光谱测定和热失重试验,分析了AID的结构和耐温性能,评价了其缓凝性能与对水泥石抗压强度的影响。试验结果显示:AID耐温可达355 ℃,热稳定性好;单体AMPS、IA和DMAM的质量比为10:4:1,反应温度为60 ℃,引发剂K2S2O8的加量为2.0%及反应时间为5 h的条件下,合成的缓凝剂性能较好;加入0.5%AID的水泥浆其稠化时间比未加AID的水泥浆长2倍之多;相同AID加量下,90~150 ℃温度范围内水泥浆的稠化时间均在300 min以上,水泥石强度发展均在14 MPa以上。研究表明,缓凝剂AID能显著延长水泥浆稠化时间,温度适应性强,对水泥石抗压强度的影响不明显,具有一定的应用前景。      

Thermal markers arising from changes in the protein component of milk

Classification of heat load applied to milk requires the detection of parameters appropriately related to the intensity of the heat treatment. Current analytical methods based on heat-induced changes in the protein component of milk have been directed either to determine the amount of protein-derived products arised from heat treatments or to evaluate the extent of thermal denaturation of milk proteins. Lately, a new analytical strategy has been developed according to the occurrence of three major whey proteins, namely bovine serum albumin (BSA), beta-lactoglobulin (βlg) and alfa-lactalbumin (αla), normally soluble at pH 4.6 in raw milk, in the pH 4.6 insoluble protein fraction recovered from heat-treated milk. The results have shown that pH 4.6 insoluble BSA, βlg and αla, as detected by ELISA in milk, can be regarded as thermal markers suited for either dairy process control or regulation purposes.     

Multiplex PCR system to track authorized and unauthorized genetically modified soybean events in food and feed

A diverse range of genetic elements has been used to develop genetically modified organisms (GMOs) over the last 18 years. Screening methods that target few elements, such as the Cauliflower Mosaic Virus 35S promoter (P-35S) and Agrobacterium tumefaciens nopaline terminator (T-nos), are not sufficient to screen GMOs. In the present study, a multiplex PCR system for all globally commercialized GM soybean events was developed to easily trace the events. For this purpose, screening elements of 24 GM soybean events were investigated and 9 screening targets were selected and divided into three individual triplex PCR systems: P-35S, ribulose-1,5-bisphosphate carboxylase small subunit promoter of Arabidopsis thaliana, T-nos, T-35S, pea E9 terminator, open reading frame 23 terminator of A. tumefaciens, proteinase inhibitor II terminator of potato, acetohydroxy acid synthase large subunit terminator of A. thaliana, and the revealed 3′ flanking sequences of DP-305423-1. The specificity of the assays was confirmed using thirteen GM soybean events as the respective positive/negative controls. The limit of detection of each multiplex set, as determined using certified reference materials of specific GM events, ranged from 0.03 to 0.5%, depending upon target. Furthermore, 26 food samples that contained soybean ingredients, which were purchased from the USA, China, Japan, and Korea, were analyzed, 17 of which contained one or more GM soybean events. These results suggest that the developed screening method can be used to efficiently track and identify 24 GM soybean events in food and feed.     

川东开江古隆起区石炭系气藏成藏机理剖析

川东地区是四川盆地稳定地块中的相对构造活动带,区内发育10排高陡构造带,其中主要的含气构造带位于开江古隆起区。川东获得天然气探明储量占全川近60%,使川东尤其是开江古隆起区成为四川乃至全国天然气的主产区。文中着重剖析了形成于开江古隆起区的3类石炭系成组气藏的成藏机理,指出开江古隆起的早期成藏及石炭系丰富的气源为现今大气田和成组气藏的形成奠定了坚实基础;位于开江古隆起顶部的大天池为最有利的富气构造带;继承非均质成组气藏为主要的富气类型。     

S型焊接金属波纹管波片波形优化设计

S型焊接金属波纹管的波片波形结构对波纹管性能影响较大,目前尚无准确表达波形结构对波纹管性能影响的具体设计公式及理论。利用ANSYS Workbench软件建立了直边波形及斜边45°波形这2种S型焊接金属波纹管波片的二维模型,以提高波片压力刚度为优化设计目标,对模型进行静力学分析,确定了需要优化的波形结构参数及其取值范围。调用ANSYS Workbench响应面优化模块,设置优化参数与目标函数,求解得到优化设计后的波片波形结构参数数值。优化设计前后波纹管波片的应力分布和压力刚度对比表明,优化设计后的波片具有更高的压力刚度及更小的应力,优化后的斜边45°波形波片的力学性能更优。     

应力敏感性对低渗透气井产能的影响

我国低渗透气藏资源丰富,是今后天然气开发的重要领域。然而,低渗透气藏在开发中具有较强的应力敏感性,影响气藏的产能建设,因此,认清应力敏感性对低渗透气藏产能的影响是开发的基础。文中在对低渗透气藏岩心进行应力敏感伤害实验研究的基础上,考虑气藏含气饱和度为100%和不同含水饱和度的情况,模拟分析了在低渗透气藏开发过程中应力敏感性所产生的渗透率变化规律,从而得出在不同应力敏感系数和不同渗透率情况下应力敏感性对气井产能的影响程度,为低渗透气藏合理开发提供依据。     

Common African cooking processes do not affect the aflatoxin binding efficacy of refined calcium montmorillonite clay

Aflatoxins are common contaminants of staple crops, such as corn and groundnuts, and a significant cause of concern for food safety and public health in developing countries. Aflatoxin B₁ (AFB₁) has been implicated in the etiology of acute and chronic disease in humans and animals, including growth stunting, liver cancer and death. Cost effective and culturally acceptable intervention strategies for the reduction of dietary AFB₁ exposure are of critical need in populations at high risk for aflatoxicosis. Fermented gruels consisting of cornmeal are a common source for such exposure and are consumed by both children and adults in many countries with a history of frequent, high-level aflatoxin exposure. One proposed method to reduce aflatoxins in the diet is to include a selective enterosorbent, Uniform Particle Size NovaSil (UPSN), as a food additive in contaminated foods. For UPSN to be effective in this capacity, it must be stable in complex, acidic mixtures that are often exposed to heat during the process of fermented gruel preparation. Therefore, the objective of the present study was to test the ability of UPSN to sorb aflatoxin while common cooking conditions were applied. The influence of fermentation, heat treatment, acidity, and processing time were investigated with and without UPSN. Analyses were performed using the field-practical Vicam assay with HPLC verification of trends. Our findings demonstrated that UPSN significantly reduced aflatoxin levels (47–100%) in cornmeal, regardless of processing conditions. Upon comparison of each element tested, time appeared to be the primary factor influencing UPSN efficacy. The greatest decreases in AFB₁ were reported in samples allowed to incubate (with or without fermentation) for 72 h. This data suggests that addition of UPSN to staple corn ingredients likely to contain aflatoxins would be a sustainable approach to reduce exposure.