Relative effects of bacterial and protozoan predators on survival of Escherichia coli in estuarine water samples

The relative effect of protozoan and bacterial predators on the survival of Escherichia coli in estuarine water samples was examined. Predacious protozoa exerted their major influence on E. coli destruction during the first 2 days of a 10-day-decline period. Inhibition of protozoa after day 2 had little effect on E. coli survival. Bacterial predators also contributed to E. coli destruction but in natural estuarine water samples were maintained at lower levels due to "grazing" by predacious protozoa.     

Studies on the ultrastructure, histochemistry and cytochemistry of the uninfected digestive gland of Bithynia tentaculata (Mollusca: Gastropoda) and on the ultrastructure of this host organ in snails infected with larval digeneans

The structure and function of the digestive gland of the gastropod mollusc, Bithynia tentaculata, was investigated using ultrastructural, histochemical, and cytochemical techniques. The digestive gland was shown to be composed of two main cell types, the "digestive" cells and "secretory" cells. The digestive cells appeared to be concerned with the absorption and digestion of nutrients, while secretory cells produced digestive enzymes and calcareous concretions. Undifferentiated cells were scattered between these two main cell types. The pathological effects of larval digeneans on the digestive gland were also investigated, at the ultrastructural level. In such infected snails the digestive gland appeared to be degenerating. The significance of this tissue destruction was briefly discussed.     

PDF417二维条码肖像图片压缩编码的优化算法研究

针对PDF417二维条码存储空间有限的问题，提出了一种基于小波变换的有损图像压缩算法，通过这个算法，可以将静态图片信息加入PDF417条码中，并能够满足在指定字节数情况下保证高质量地压缩图像，该文在分析小波变换等算法理论的基础上，详细介绍了PDF417二维条码肖像图片压缩编码的优化算法及该算法的实验结果与美国Symbol公司的PC2VQ算法结果对比。     

Analysis of the mechanical performance of a cardiovascular stent design based on micromechanical modelling

Stents are very commonly used in the treatment of coronary heart disease. They are permanent vascular support structures that offer a preferred alternative to bypass surgery in certain situations. The purpose of this work is to examine the mechanical behaviour of a stainless steel balloon expandable stent design using computational micromechanics in the context of the finite element method. Deployment and cardiac pulsing loading conditions are considered. Classical phenomenological plasticity theory (J₂ flow theory) and physically based crystal plasticity theory are used to describe the stent material behaviour. Parametric studies are carried out using both constitutive theories with a view to determining important stent deployment characteristics such as recoil and foreshortening. Comparisons of the results obtained using both theories illustrate differences, with the crystal plasticity theory models showing closer agreement to published performance data. The implications of this for stent design are discussed.     

Apple,Carrot, and Hibiscus Edible Films Containing the Plant Antimicrobials Carvacrol and Cinnamaldehyde Inactivate Salmonella Newport on Organic Leafy Greens in Sealed Plastic Bags

The objective of this study was to investigate the antimicrobial effects of carvacrol and cinnamaldehyde incorporated into apple, carrot, and hibiscus‐based edible films against Salmonella Newport in bagged organic leafy greens. The leafy greens tested included organic Romaine and Iceberg lettuce, and mature and baby spinach. Each leafy green sample was washed, dip inoculated with S. Newport (10⁷ CFU/mL), and dried. Each sample was put into a Ziploc® bag. Edible films pieces were put into the Ziploc bag and mixed well. The bags were sealed and stored at 4 °C. Samples were taken at days 0, 3, and 7 for enumeration of survivors. On all leafy greens, 3% carvacrol films showed the best bactericidal effects against Salmonella. All 3 types of 3% carvacrol films reduced the Salmonella population by 5 log₁₀ CFU/g at day 0 and 1.5% carvacrol films reduced Salmonella by 1 to 4 log₁₀ CFU/g at day 7. The films with 3% cinnamaldehyde showed 0.5 to 3 log reductions on different leafy greens at day 7. The films with 0.5% and 1.5% cinnamaldehyde and 0.5% carvacrol also showed varied reductions on different types of leafy greens. Edible films were the most effective against Salmonella on Iceberg lettuce. This study demonstrates the potential of edible films incorporated with carvacrol and cinnamaldehyde to inactivate S. Newport on organic leafy greens.     

Effects of material thickness and processing method on poly(lactic-co-glycolic acid) degradation and mechanical performance

In this study, the effects of material thickness and processing method on the degradation rate and the changes in the mechanical properties of poly(lactic-co-glycolic acid) material during simulated physiological degradation were investigated. Two types of poly(lactic-co-glycolic acid) materials were considered: 0.12?mm solvent-cast films and 1?mm compression-moulded plates. The experimental results presented in this study were compared to the experimental results of Shirazi et al. (Acta Biomaterialia 10(11):4695–703, 2014) for 0.25?mm solvent-cast films. These experimental observations were used to validate the computational modelling predictions of Shirazi et al. (J Mech Behav Biomed Mater 54: 48–59, 2016) on critical diffusion length scale and also to refine the model parameters. The specific material processing methods considered here did not have a significant effect on the degradation rate and the changes in mechanical properties during degradation; however, they influenced the initial molecular weight and they determined the stiffness and hardness of the poly(lactic-co-glycolic acid) material. The experimental observations strongly supported the computational modelling predictions that showed no significant difference in the degradation rate and the changes in the elastic modulus of poly(lactic-co-glycolic acid) films for thicknesses larger than 100?μm.     

化学合成制药综合废水的处理

本文介绍了化学合成制药废水的处理工艺、原理和运行效果,该工艺处理后的污水完全达到国家规定的污水排放标准。     

精炼工艺对椰子油品质的影响

研究了精炼工艺对椰子油品质的影响。分析了毛椰油、碱炼油、脱色油、脱臭油的理化指标、脂肪酸、甘油酯组成和脂肪伴随物(甾醇、生育酚、多酚)的变化情况。结果表明:精炼工艺使椰子油的酸值、过氧化值显著降低,脂肪酸和甘油酯组成无显著变化;总甾醇、总生育酚和多酚含量显著降低,损失率分别为63.77%、68.03%、71.20%。综上表明,精炼能够显著影响油脂品质,需注重油脂适度加工技术的应用。     

DEFECT CORRECTION WITH A FULLY COUPLED INEXACT NEWTON METHOD

Abstract

We examine the characteristics of a fully coupled inexact Newton method using defect correction to obtain high-order solutions for two problems: natural convection in a square cavity and mixed-convection flow over a backward step. Newton's method produces a linearized system with a Jacobian matrix and a residual vector, each of which can be formed using different discrete operators. Solution accuracy depends on the discretization used for the residuals. Defect correction employs low-order operators for the Jacobian but high-order operators for the residuals. We employ an O(h³) convection operator in the residual vector and upwinding in the Jacobian. We find that defect correction is an efficient and effective way to achieve high-order solutions.     

General method for plasmid construction using homologous recombination

We describe a general method for plasmid assembly that uses yeast and extends beyond yeast-specific research applications. This technology exploits the homologous recombination, double-stranded break repair pathway in Saccharomyces cerevisiae to join DNA fragments. Synthetic, double-stranded "recombination linkers" were used to "subclone" a DNA fragment into a plasmid with > 80% efficiency. Quantitative data on the influence of DNA concentration and overlap length on the efficiency of recombination are presented. Using a simple procedure, plasmids were shuttled from yeast into E. coli for subsequent screening and large-scale plasmid preps. This simple method for plasmid construction has several advantages. (i) It bypasses the need for extensive PCR amplification and for purification, modification and/or ligation techniques routinely used for plasmid constructions. (ii) The method does not rely on available restriction sites, thus fragment and vector DNA can be joined within any DNA sequence. This enables the use of multifunctional cloning vectors for protein expression in mammalian cells, other yeast species, E. coli and other expression systems as discussed. (iii) Finally, the technology exploits yeast strains, plasmids and microbial techniques that are inexpensive and readily available.