Modeling the thermal inactivation kinetics of heat-resistant Salmonella Enteritidis and Oranienburg in 10 percent salted liquid egg yolk

There is no suitable model for predicting thermal inactivation kinetics of Salmonella spp. for many types of liquid egg products, including salted liquid egg yolk, for use in updating U.S. Department of Agriculture (USDA) pasteurization guidelines. This is because, in part, of the variations in Salmonella strains and the changes in the processing of liquid egg products over the past 40 years. The objectives of the present study were to determine the thermal inactivation kinetics and to create a general thermal inactivation kinetics model that can be used for estimating log reductions of salmonellae in 10% salted liquid egg yolk for temperatures between 62.2 and 69°C. This model can be used by processors to help ensure adequate pasteurization. This was accomplished by studying the inactivation kinetics of a three-strain composite of heat-resistant Salmonella serovars Enteritidis and Oranienburg, inoculated into commercially processed 10% salted liquid egg yolk. The survival curves were convex, with asymptotic D-values. From these curves, a general model was developed to predict log reductions for given times at specified temperatures. For example, at a temperature of 67.3°C (153.1°F) for 3.5 min, our model predicts a 5-log reduction would be obtained, whereas with the current USDA minimum required pasteurization regimen (63.33°C [146°F] for 3.5 min), our model predicts that a reduction of only 2.7 log would be obtained. The results of this study provide information that can be used by processors to aid in producing safe, pasteurized egg yolk products, and for satisfying USDA pasteurization performance standards and developing industry guidance.     

The relationship between compliance with lens replacement and contact lens-related problems in silicone hydrogel wearers

Purpose

To evaluate the relationship between compliance with replacement frequency (RF) and contact lens (CL)-related problems in silicone hydrogel (SiHy) wearers.

Methods

501 SiHy wearers from seven optometry offices completed surveys regarding their lens wear and any CL related problems which they may have experienced in the preceding 12 months. File review was subsequently conducted at their optometry offices to confirm the information provided.

Results

49% of respondents were wearing 2-week replacement (2WR) and 51% 1-month replacement (1MR) SiHy lenses. 67% wore their lenses for longer than the manufacturers’ recommended RF (MRRF) and 60% for longer than their optometrist's recommended RF (ORRF). The mean RF was 2.6× the MRRF for 2WR and 1.5× for 1MR wearers (p < 0.001) with median values of 31 and 37 days, respectively. Twenty-three percent reported signs or symptoms consistent with potential complications relating to CL wear. This rate was significantly higher for wearers who were non-compliant with the ORRF than compliant wearers (26% versus 18%, p = 0.028). It was also higher for those multipurpose solution users who reported never/almost never rubbing and rinsing their lenses when compared with those who did this every night (29% versus 17%, p = 0.007).

Conclusions

Two thirds of the SiHy wearers did not comply with the MRRF and 2WR wearers stretched the replacement interval of their lenses to a greater degree than 1MR wearers. Failing to replace lenses when recommended and failing to rub and rinse lenses were associated with a higher rate of patient-reported CL problems.     

A comparison between the finite element and frequency response methods in the assessment of thermal striping damage

When incompletely mixed, hot and cold fluid streams pass adjacent to the surface of a component or structure, and cause thermal striping on the surface. The existing methods of assessment of the consequent thermal fatigue damage have been implemented in the computer codes CLOUDBURST, TBL and STRIPE, and these have been shown to be in good agreement. Analysis of temporally random striping is possible in two of the methods, whereas use of the finite element method in such a fatigue analysis may lead to impractically long run times. However, for the special case of sinusoidal patterns of striping, comparison is made in this paper between TBL and the finite element method for the assessment of thermal striping damage.

A fully restrained, single edge cracked plate and a circumferentially cracked cylinder, axially restrained and unrestrained, have been subjected to sinusoidal surface striping for various representative temporal frequencies. The resulting stress intensity factor fluctuations have been determined for various crack depths using the finite element computer code ABAQUS and the analytical code TBL. Good comparisons have been obtained in all cases.     

Temporal variations in road traffic fatalities in South Africa

The annual road traffic fatality (RTF) burden of 43 deaths per 100 000 inhabitants in South Africa (SA) is disproportionately high in comparison to the world average of 22 per 100 000 population. Recent research revealed strong geographical variations across district councils in the country, as well as a substantial peak in mortality occurring during December. In this study, the factors that explain temporal variations in RTFs in SA are examined. Using weekly data from the period 2002–2006 for the country's nine provinces, non-linear auto-regression exogenous (NARX) regression models were fitted to explain variations in RTFs and to assess the degree to which the variations between the provinces were associated with the temporal variations in risk factors. Results suggest that a proportion of the variations in weekly RTFs could be explained by factors other than the size of the province population, with both temporal and between-province residual variance remaining after accounting for the modelled risks. Policies directed at reducing the effects of the modifiable risks identified in our study will be important in reducing RTFs in SA.     

Rugged, portable tungsten coil atomic emission spectrometer

Tungsten coil atomic emission spectrometry is an ideal technique for field applications because of its simplicity, low cost, low power requirement, and independence from cooling systems. A new, portable, compact design is reported here. The tungsten coil is extracted from an inexpensive 24 V, 250 W commercial light bulb. The coil is housed in a small, aluminum cell. The emission signal exits from a small aperture in the cell, while the bulk of the blackbody emission from the tungsten coil is blocked. The resulting spectra exhibit extremely low background signals. The atomization cell, a single lens, and a hand-held charge coupled device (CCD) spectrometer are fixed on a 1 × 6 × 30 cm ceramic base. The resulting system is robust and easily transported. A programmable, miniature 400 W solid-state constant current power supply controls the temperature of the coil. Fifteen elements are determined with the system (Ba, Cs, Li, Rb, Cr, Sr, Eu, Yb, Mn, Fe, Cu, Mg, V, Al, and Ga). The precision ranges from 4.3% to 8.4% relative standard deviation for repetitive measurements of the same solution. Detection limits are in the 0.04 to 1500 μg/L range. Accuracy is tested using standard reference materials for polluted water, peach leaves, and tomato leaves. For those elements present above the detection limit, recoveries range from 72% to 147%.     

Compositional heterogeneity may limit the usefulness of some commercial naphthenic acids for toxicity assays

Naphthenic acids are considered variously as monocarboxylic acids fitting the formula C_nH_2n + zO₂ (where z is a zero or negative even integer), as only alicyclic (i.e. non-aromatic) monocarboxylic acids fitting this formula (z ≤ 0), or simply as those carboxylic acids occurring in petroleum products or crude oils that have been formed through biodegradation of hydrocarbons. Such acids are known constituents of the process-affected water associated with some expanding oil sands industries, of some immature and biodegraded crude oils, of produced water discharges from oil production platforms and are used as biocides and as components in the manufacture of steel radial tyres.As a result of these potential vectors of the acids into the environment, various naphthenic acid mixtures which are available commercially have been used for a range of toxicity studies. However, as some manufacturers make clear, but which is not often emphasised in the toxicity studies, a range of different quality naphthenic acids is produced commercially. It has been suggested previously, and we showed recently and elucidate further herein, that such commercial mixtures therefore sometimes contain toxic components other than carboxylic acids. For example, we identify herein by two-dimensional comprehensive gas chromatography-mass spectrometry, a range of C_0-6 alkylphenols in a batch of commercial naphthenic acids. Since these compounds are known toxicants, the contribution of such non-carboxylic acids, if any, to the toxicity attributed previously to the acids, should also be considered. This will be reflected in the concentrations and effective toxicities of such components. In order to establish the toxicity of the acids per se, assays of pure synthetic carboxylic acids of the type now known to be present in naphthenic acids from petroleum or oil sands may be more appropriate than tests of the toxicity of largely unknown, heterogeneous, mixtures.     

综合多种预测方案实现遮挡情况下的目标跟踪

由于采用了多种运动预测方案,本文提出的目标跟踪方法能选择最佳的观测结果,实现对非标定固定焦距的静止摄像机的单目图像序列中的目标跟踪.静态背景参考图像由混合模型法估计,在最简单的环境下,跟踪算法则采用匀加速运动模型对目标完成跟踪.本文主要贡献是采用了三个预测器和最小方差相关时选择目标最可能的位置.三个预测器分别是:-跟踪方案、卡尔曼滤波和区域分割匹配方案.本跟踪方案通过具有不同遮挡情况的序列图像得到了验证.