Molecular characterization of Escherichia coli O157 contamination routes in a cattle slaughterhouse

In a cattle slaughterhouse, sampling was performed over a 1-week period to examine the prevalence and possible contamination routes of Escherichia coli O157. Each sampling day, swab samples were collected from the slaughterhouse environment before onset of slaughter, from the slaughterline, and from 20 successively slaughtered animals. Isolation of E. coli O157 consisted of a 6-hour enrichment followed by immunomagnetic separation and selective plating. From the 394 samples taken, 84 (21%) were positive for E. coli O157. Pulsed-field gel electrophoresis (PFGE) of collected isolates produced 26 different profiles, from which 5 PFGE profiles carried two or more Stx genes. The combination of PFGE profiles and Stx types resulted in 32 different E. coli O157 types. E. coli O157 was found in the slaughterhouse environment before the onset of slaughter. The first two sampling days, feces and carcasses were found negative. On the third sampling day, five fecal samples and four carcasses from animals negative in the feces were positive. Hide of the anal region and the shoulder were found positive every sampling day. The shoulder hide was more than twice as contaminated as the anal region hide. Typing of different isolates from a sample showed that frequently different E. coli O157 types were presented. On sampling days 1 and 2, types present in the environment and on the hides of the slaughtered animals differed. On the third sampling day, two dominant types were found in the environment (even before the onset of slaughter), as well as on the hides, feces, and carcasses. Although examined animals originated from different farms, one (two on day 3) dominant E. coli O157 type was present on their hides each sampling day. These data indicated that (i) the progress of contamination can differ from day to day within a slaughterhouse and (ii) contact between animals after the departure from the farm can have a large effect on the spread of E. coli O157 hide contamination.     

Efficacy of enrichment broths in the recovery of freeze-injured Escherichia coli O157:H7 in inoculated ground beef by PCR

Escherichia coli O157:H7 strains ATCC 35150 and ATCC 43894 and five pooled isolates from beef and pork freeze injured at -25 degrees C in beef infusion were used to inoculate ground beef. Samples (25 g each) were added to 225 ml of buffered peptone water with vancomycin, cefsulodin, and cefixime (BPW-VCC), 225 ml of modified EC broth plus novobiocin (mEC+n), and 225 ml of R&F enrichment broth (R&F-EB) and aerobically incubated at 41 to 42 degrees C. After 6, 7, 8, and 24 h of incubation, levels of E. coli O157:H7 recovered from each broth by a PCR assay with the BAX automated system as well as by conventional enrichment with the use of nonaerated mEC+n incubated at 35 degrees C for 24 h were compared with levels recovered by cultural isolation with immunomagnetic separation and plating on BCM E. coli O157:H7 chromogenic agar. For ground beef inoculated with a mean of 4.23 +/- 1.00 total cells (74% freeze injured) per 25 g, after 6 h the PCR assay identified 72.7, 57.6, and 66% of the samples for R&F-EB, BPW-VCC, and mEC+n, respectively, as presumptive positive, whereas the recovery rates after 7 and 8 h exceeded 90%, with the rate for R&F-EB being 100%. For ground beef inoculated with a mean of 1.50 +/- 0.56 total cells (80% freeze injured) per 25 g, after 6 h the PCR assay identified 47.6, 19.1, and 9.5% of the samples for R&F-EB, BPW-VCC, and mEC+n, respectively, as presumptive positive. These values increased to 81.0, 61.9, and 52.4% after 7 h and to 95.2, 61.9, and 71.4% after 8 h. After 24 h, only 55 to 60% of the samples at both inoculum levels tested positive by PCR with conventional enrichment and incubation, whereas >95% of the samples tested positive with R&F-EB aerated at 41 to 42 degrees C. Culture results for R&F-EB and mEC+n after 7 and 8 h of incubation were closely correlated with presumptive positive PCR results.     

Ventilation effects on air quality and on the yield and quality of ewe milk in winter

The effects of ventilation on air quality, and on the welfare and production performance of dairy ewes were assessed in a 6-wk trial conducted during the winter of 2002. Thirty-six midlactation Comisana ewes were divided into three groups of 12, which were randomly balanced for parity, time of lambing, and number of lambs suckled. Treatments were low (LOV), moderate (MOV), and programmed ventilation regimen (PROV). In LOV and MOV rooms, fans provided 10 ventilation cycles of 40 min each at a fan speed of 1 and 2 m/s, respectively. In the PROV room, the fan was programmed to maintain a 70% relative humidity. Mean ventilation rates were 23, 47, and 73 m3/h per ewe in LOV, MOV, and PROV rooms, respectively. Air concentrations of microorganisms and dust, and of gaseous pollutants were measured twice weekly. Cell-mediated immune response to phytohemagglutinin at d 1, 21 and 42, and humoral response to chicken egg albumin at d 11, 21, 30, and 40 were determined. At d 39, ewes were injected with 2 IU of porcine adreno-corticotropic-hormone/kg body weight(0.75), and subjected to blood sampling for evaluation of cortisol concentrations immediately before and 1, 2, and 4 h after adreno-corticotrophic-hormone injection. Milk yield was recorded daily. Individual milk samples were analyzed weekly for composition, renneting parameters, and somatic cell count. The LOV treatment resulted in higher air concentrations of NH3 and CO2 than the MOV and PROV treatments. Greater amounts of total and respirable dust were found in the PROV room than in the LOV and the MOV rooms. The LOV ewes had lower milk yield than the PROV ewes, lower milk casein content, and higher rate of clot formation than the MOV and PROV ewes. The ventilation regimen did not affect the immune and endocrine responses of the ewes. Results suggest that an intermittent ventilation regimen, providing a mean ventilation rate of 47 m3/h per ewe at a fan speed of 2 m/s, is required to sustain the yield and cheese-making ability of ewe milk during the winter season.     

两种大孔径预裂爆破新技术

人们已经认识到,采用预裂爆破这种特殊的爆破技术,可以明显地降低炮孔内炸药爆轰对孔壁产生的压力,从而达到避免岩体过度破坏的目的。其具体的技术途径有2种,一是采用低密度炸药,二是采用径向不偶合装药。本文分别介绍了这2种方法在大直径深孔条件下的应用情况,并根据预裂面的质量对这2种方法进行了分析和评估。第一种方法使用的炸药其密度极低,仅为02g/cm3。首先在地表对这种炸药进行了无约束条件下的性能试验,然后在一大型露天煤矿进行了现场工业应用试验。现场试验炮孔为直径311mm、深45m的垂直孔。孔内爆速平均为2200m/s。与采用常规炸药的相邻区段相比,预裂面半壁孔率由32%提高到62%,表明采用这种方法的大孔径预裂爆破是成功的。在另一大型露天煤矿的预裂爆破中采用径向不偶合装药的方法,炮孔直径为270mm、最大深度达70m的倾斜孔,孔内水深最大达60m。药包直径150mm,长度6m。使用的炸药为常规散装乳化炸药,其密度为12g/cm3,孔内爆速平均5800m/s。采用此种方法,所形成的边坡平整度明显好于采用常规装药结构的相邻区域,说明这种方法同样能够获得良好的预裂爆破效果。     

Size and location of ice crystals in pork frozen by high-pressure-assisted freezing as compared to classical methods

In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to - 20 °C without ice formation then pressure is released (0.1 MPa) and the high super-cooling reached (approx. 20 °C), promotes uniform and rapid ice nucleation. The size and location of ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared to those obtained by air-blast and liquid N(2). Samples from the surface and centre of the frozen muscle were histologically analysed using an indirect technique (isothermal-freeze fixation). Air-blast and cryogenic fluid freezing, having thermal gradients, showed non-uniform ice crystal distributions. High-pressure-assisted frozen samples, both at the surface and at the central zones, showed similar, small-sized ice crystals. This technique is particularly useful for freezing large pieces of food when uniform ice crystal sizes are required.     

Anticorrosive properties of extracts from waste of rice processing

The application of corrosion inhibitors for metal protection is one of the most si mple and accessiblemethod.Different classes of organic substances areinvestigated as corrosioninhibitors,unfortunately,onlya feworganic substances possess a unique combination of the physical,chemical and toxicological proper-ties,allowing to use themas effective and environmentally safe inhibitors for mild steel corrosion.In thisconnection search of new,cheap and ecologically safe corrosion inhibitors is an act…     

在赤铁矿-石英浮选体系中疏水细菌的作用

最近报道的文献表明，微生物有可能作为浮选药剂。本研究将非病源性疏水暗红球细菌(Rhodococcus opacus，缩写为R．opacus)作为赤铁矿-石英体系中的浮选药剂。对经微生物预处理前后的矿物进行了电泳迁移率测定、接触角测定、扫描电镜分析和微量浮选试验。微生物与矿物的相互作用使得矿物表面化学性质发生明显变化。赤铁矿与石英混合物的微量浮选试验表明。通过生物预处理，浮选赤铁矿颗粒和抑制石英颗粒是可能的。在所测定的pH范围内，可用DLVO理论解释与生物作用后石英颗粒Zeta电位、接触角和浮选行为的变化。对于赤铁矿，该理论仅适于预测在有限的pH范围内的吸附现象。     

用孔隙度截止值评价有效产层的统计方法

许多储层评价研究都需要确定有效产层。通常是用孔隙度一渗透率交会图和回归线确定的截止孔隙度来预测有效产层。我们研究了精确地求取截止孔隙度的统计方法。对于有效产层的校准，本文没有从地质和工程方面考虑，而是研究了渗透率下限值。 我们认为确定有效产层和估算有效产层／总产层比时。这两项工作都要求规定的两个不同的孔隙度截止值的误差尽可能小。从样本数据中，我们发现：对孔隙度和渗透率值用最小二乘线性回归得到的截止值，通常和最佳估计截止值相差1或者2个孔隙度单位。线性回归估计的截止值误差比最佳估计截止值大2％到10％。我们提出一种方法。用来计算线性回归和最佳估计截止值的差别，但是实践显示不乐观。我们的方法假设测量无误差，但估算截止值时，讨论步骤包含误差。 假设渗透率和孔隙度之间是正态分布的，通过分析我们发现确定有效产层的孔隙度截止值和估算有效产层／总产层比的孔隙度截止值是不同的。我们发现确定有效产层／总产层比的孔隙度截止值时需用最佳主轴线。而有效产层的孔隙度截止值需要Y—X回归线。 在使用孔隙度预测有效产层的统计过程中，误差不可能完全消除。孔隙度一渗透率交会图能得到更多的信息来获得更准确的截止值。这种方法符合“适用”的原则，能尽最大可能地利用已有的数据。     

Petrophysical and capillary pressure properties of the upper Triassic Xujiahe Formation tight gas sandstones in western Sichuan, China

The tight sandstones of the Upper Triassic Xujiahe Formation（T₃x） constitute important gas reservoirs in western Sichuan.The Xujiahe sandstones are characterized by low to very low porosity （av.5.22%and 3.62%） for the T₃x⁴ and T₃x² sandstones,respectively),extremely low permeability（av. 0.060 mD and 0.058 mD for the T₃x⁴ and T₃x² sandstones,respectively）,strong heterogeneity,micronano pore throat,and poor pore throat sorting.As a result of complex pore structure and the occurrence of fractures,weak correlations exist between petrophysical properties and pore throat size,demonstrating that porosity or pore throat size alone does not serve as a good permeability predictor.Much improved correlations can be obtained between permeability and porosity when pore throat radii are incorporated. Correlations between porosity,permeability,and pore throat radii corresponding to different saturations of mercury were established,showing that the pore throat radius at 20%mercury saturation(R₂₀) is the best permeability predictor.Multivariate regression analysis and artificial neural network（ANN） methods were used to establish permeability prediction models and the unique characteristics of neural networks enable them to be more successful in predicting permeability than the multivariate regression model.In addition, four petrophysical rock types can be identified based on the distributions of R₂₀,each exhibiting distinct petrophysical properties and corresponding to different flow units.     

Anatomical and histological changes in the oviducts of Japanese quail, Coturnix japonica, after embryonic exposure to ethynyloestradiol

Oestrogen is needed for normal oviductal development in female birds, but excessive early exposure to oestrogen can cause oviductal abnormalities and impair egg-laying ability. In this study, the anatomical and histological effects of in ovo exposure to the synthetic oestrogen ethynyloestradiol on the oviducts of immature and adult female Japanese quail, Coturnix japonica, were investigated. A series of abnormalities was observed after injection of ethynyloestradiol (2 or 20 ng g(-1) egg) into the yolk on day 3 of incubation. Ethynyloestradiol induced precocious differentiation of the luminal epithelium and tubular glands in immature chicks. Right-side oviduct retention occurred at all the ages studied, whereas certain other effects were not evident until sexual maturity. The left oviduct was reduced in size and tubular gland density in the uterus (shell gland) was reduced in sexually mature birds that had been treated with ethynyloestradiol. The utero-vaginal junction was longer than in control birds and had a higher tubular gland density. The epithelial cells in the magnum were taller in birds treated with ethynyloestradiol. Embryonic exposure to the environmental contaminant ethynyloestradiol may cause persisting structural malformations in oviducts of quails, which can impair fertility. As oviductal malformations are indicative of embryonic exposure to exogenous oestrogen, they are potentially useful as biomarkers of xenooestrogen exposure in wild bird populations.