Current and emerging molecular diagnostic technologies applicable to bacterial food safety

There is an increasing need for rapid test methods to certify the quality and safety of food products. Current tests applied for the microbiological assessment of food products are based on standard approved culture-based isolation methods and can take several days to yield results. Nucleic acid diagnostic (NAD) tests for the identification of bacterial foodborne pathogens employing in vitro amplification technologies are capable of sensitive and specific detection of single or multiple pathogens in foods in a shorter timeframe than traditional methods. New developments in molecular biosensors have the potential to provide at-line bioanalysis, whereas microarray-based technologies may in the future be the NAD platforms of choice for multiple pathogen detection and identification. This article reviews current and emerging NAD platforms for foodborne bacterial pathogens that have the potential to impact food safety.     

Practical Estimation of Seepage Losses Along Earthen Canals in Egypt

Seepage from open channels is one of the major problems involved in the design of irrigation networks. However the advantage of conserving water is necessary as water is becoming a scarce commodity. As the suspended solid materials in water became less than 100 ppm after the construction of the High Aswan Dam (HAD) in Egypt, unfortunately few previous practical formulas for estimating seepage losses along earthen Egyptian canals are applicable and new design equations are needed. Through the present paper, extensive field data measurements have been carried out on carrier irrigation canals for seepage analysis. Regression equations were developed for relating seepage losses to the flow and geometrical canal parameters. These deduced equations are based on the inflow-outflow procedure and the boundary materials, and are valid for earthen canals having discharges ranging between 2 and 20 m³/sec.     

Combining Expert Systems and Cad Techniques

Drawings provide a medium for communicating design decisions. The dtask of preparing and changing design drawings has been simplified by various packages available for computer aided drafting (CAD). Recently, expert-systems techniques are being used to aid the design process by monitoring and refining design decisions. Combining expert systems and CAD techniques raises issues concerning representation of the design. An expert system for evaluation of the design. An expert system for evaluation of preliminary structural designs has been implemented using an expert system shell and a CAD package. This and other similar implementations illustrate different approaces to the integration problems     

Deterioration of Fresh-Water Whitefish Muscle During Frozen Storage at −10°C

SUMMARY— Organoleptic and chemical deterioration of freshwater whitefish muscle frozen at −10°C for periods up to 16 weeks was assessed. As frozen storage of muscle progressed, the toughness and rancidity of baked muscle increased. The solubility of the myofibrillar protein fraction, "actomyosin," dropped from about 72 to 22% over the 16 week storage period of whitefish muscle. No change in the solubility of sarcoplasmic protein in frozen stored muscle was observed. However, with polyacrylamide disc electrophoresis, two new sarcoplasmic protein bands were detected after 16 weeks of storage. With storage of frozen muscle, water-binding capacity diminished. Although the total lipid and cholesterol contents of muscle remained constant throughout frozen storage, the phospholipid content decreased as the free fatty acid content increased. Oxidative deterioration of lipid in frozen muscle was estimated.     

厌氧内循环反应器的结构、应用与优化

厌氧内循环（IC）反应器是第三代厌氧反应器的典型代表之一,具有容积效能高、节省能源、占地面积小、高径比大等特点,近年来逐渐在我国高浓度有机废水处理领域崭露头角。本文阐述了IC反应器的结构原理和水力特性,其结构相当于两个升流式污泥床（UASB）反应器串联,并具有内循环结构,水力特性包括升流速度和系统压降两个重要参数;概述了IC反应器的启动,其启动周期一般为3~6个月,增加污泥浓度可实现快速启动;介绍了IC反应器的底物抑制特性,其表现出一定氨氮耐受性;综述了该反应器的工程应用,论述了其在畜禽类高氨氮废水的处理潜力,并提出了IC反应器结构与工艺的优化方向。     

螺旋对称流厌氧反应器常温下的运行特性

螺旋对称流厌氧反应器（SSSAB）的最高有机负荷能在中温条件下（35℃）可达361.5kgCOD/（m³·d）,然而在常温条件下（10～30℃）其运行性能及污泥特征尚不明确,需进一步探究。以分段组合式厌氧反应器（TCAB）和升流式厌氧污泥床反应器（UASB）为参比,在常温下,以相同的操作条件研究了SSSAB的运行性能和污泥特征。实验结果表明：SSSAB的COD平均去除率（88%）高于TCAB和UASB（80%和78%）,SSSAB的一级反应动力学常数为5.4d^-1,高于TCAB的3.6d^-1和UASB的2.2d^-1。SSSAB内颗粒污泥宏观上相比于TCAB及UASB轮廓清晰、黑亮密实,且SSSAB颗粒污泥表面微观上较为粗糙,存在许多孔道。SSSAB颗粒污泥的胞外聚合物（EPS）总量高于TCAB及UASB,为底物的质量传递创造了条件,SSSAB颗粒污泥EPS的蛋白质（PN）/多糖（PS）较低,更有利于维持高污泥强度和优良的沉降性能。相比于UASB,SSSAB厌氧颗粒污泥凝聚性的分布更优,且其凝聚性波动更小。     

Two polymorphisms in methylenetetrahydrofolate reductase gene (C677T and A1298C) frequently associated with recurrent spontaneous abortion show no association in Saudi women

Methylenetetrahydrofolate reductase (MTHFR) deficiency is the most common genetic cause of hyperhomocysteinemia, which has been implicated in the etiology of recurrent spontaneous abortion (RSA). This study was designed to investigate the association between two single nucleotide polymorphisms (SNP) (rs1801133 [C677T] and rs1801131 [A1298C]) in the MTHFR gene and RSA, in Saudis. These two SNPs were selected as these polymorphisms have a different effect on the activity and stability of the enzyme, and significantly diverse effects have been reported in relation to the association with RSA. Ethical approval was acquired from the IRB at King Saud University (KKUH), Saudi Arabia, and written informed consent was obtained from each participant. The study group comprised of 100 Saudi women with unexplained RSA and 100 age-matched controls, both attending KKUH for a routine checkup. Blood was drawn in EDTA tubes, and DNA was extracted. Genotyping was conducted using TaqMan SNP genotyping assay kits. The frequency of the T allele of C677T was 0.165 in patients and 0.17 in controls. Genotype frequencies for CC, CT and TT genotypes were 70%, 27% and 3%, respectively in RSA, and 71%, 24% and 5%, respectively, in the controls (p > 0.05). For the A1298C polymorphism, the C allele frequencies were 0.345 in patients and 0.28 in controls, while genotype frequencies for AA, AC and CC genotypes were 44%, 43%, and 13%, respectively, in patients, and 54%, 36%, and 10%, respectively, in controls (p > 0.05). The frequency of CC genotype and C allele of A1298C were higher in the patients with RSA, but not significantly, while C677T genotypes and allele frequencies did not differ between patients and controls. The results suggested that MTHFR gene polymorphisms are population-specific and may not associate with RSA in Saudi women.     

A Practical Approach to Object-oriented State Modeling

A widely accepted approach in object-oriented methods is the early decomposition of the state-dependent behavior of the system between its objects and specifying it at the object or class level. In the flexible state modeling approach presented in this paper, analysis avoids strong mapping of statecharts to objects. The state-dependent behavior of the system is specified by a number of statecharts that can be at different levels of abstraction and detail. A statechart can be associated with a class or an object, but can also be of more ‘floating nature’, capturing aspects of the behavior that cut across objects and classes. Later in design, statecharts are refined by recognizing the two dimensions of how statecharts are integrated with objects, namely type (active or passive) and scope (shared, per class or per object). These are first illustrated by general examples and later by more specific examples. Pieces of source code are also provided to clarify some aspects. The flexible state modeling approach is more practical than the common approach because it enables a comprehensible specification of the state-dependent behavior without requiring object interactions to be specified for the purpose of accessing state information. ©1997 by John Wiley & Sons, Ltd.     

RISK ANALYSIS IN CONSTRUCTION NETWORKS USING A MODIFIED STOCHASTIC ASSIGNMENT MODEL

A review of construction network analysis indicates that new methods are needed for quantifying risks in project evaluation. The paper proposes a new analytical method, the Modified Stochastic Assignment Model (MSAM), for the prediction of project duration. The proposed method is inspired by a previous method used solely in traffic networks, the Stochastic Assignment Model (SAM). The MSAM method applies Clark's approximation to find the longest project duration. Two cases are used to demonstrate the validity and application of the MSAM in construction project evaluations. The accuracy of the MSAM is assessed by comparing it with the Monte Carlo Simulation (MCS). A comparison of the MSAM with other methods, such as PERT and PNET, has also been presented. It is found that the new method is an analytical counterpart of the MCS and is very efficient in saving computational time whilst taking full account of the correlations between paths.