Contamination of Clams with Human Norovirus and a Novel Hepatitis A Virus in Cameroon

Food and Environmental Virology - Shellfish constitute an important protein source but may be contaminated by viruses from various origins. A study performed on clams collected in Cameroon showed a...     

BETR global--a geographically-explicit global-scale multimedia contaminant fate model

We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15° × 15° grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5).     

Population dynamics during startup of thermophilic anaerobic digesters: The mixing factor

Two thermophilic digesters were inoculated with manure and started-up under mixed and stagnant conditions. The Archaea in the mixed digester (A) were dominated by hydrogenotrophic Methanobateriaceae (61%) with most of the methane being produced via syntrophic pathways. Methanosarcinales (35%) were the only acetoclastic methanogens present. Acetate dissipation seems to depend on balanced hydrogenotrophic-to-acetotrophic abundance, which in turn was statistically correlated to free ammonia levels. Relative abundance of bacterial community was associated with the loading rate. However, in the absence of mixing (digester B), the relationship between microbial composition and operating parameters was not discernible. This was attributed to the development of microenvironments where environmental conditions are significantly different from average measured parameters. The impact of microenvironments was accentuated by the use of a non-acclimated seed that lacks adequate propionate degraders. Failure to disperse the accumulated propionate, and other organics, created high concentration niches where competitive and inhibiting conditions developed and favored undesired genera, such as Halobacteria (65% in B). As a result, digester B experienced higher acid levels and lower allowable loading rate. Mixing was found necessary to dissipate potential inhibitors, and improve stability and loading capacity, particularly when a non-acclimated seed, often lacking balanced thermophilic microflora, is used.     

Effect of Accelerated Weathering on Biocomposites Processed by SMC and Compression Molding

The durability of biocomposites utilized for building components has been a subject of recent concern and questioning. To address these concerns, the long-term effects of weathering on biocomposites used as building components were evaluated using an accelerated weatherometer. The biocomposite samples were processed by sheet molding compounding (SMC) panel processing and/or compression molding. The accelerated weatherometer served to expose the samples to ultraviolet radiation (UV), condensation, and water spray at levels pertinent to actual conditions: 48 cycles of UV (340 nm) treatment at 60 °C for 2.5 h was followed by water spray for 0.5 h, and then condensation at 45 °C for 24 h. Twelve cycles were repeated in each test, and the total duration for the complete test was 2016 h. Measurements for color, surface roughness test weight change, and dynamical mechanical analysis were taken at regular intervals of time. It was found that the surface roughness increased, as the color changed, and storage modulus decreased with increases in the exposure time of the samples to accelerated weathering conditions, compared to their properties at the beginning of the test.     

A note on the sufficiency of low resolution ecosystem models

Analysis of a system of non-linear differential equations illustrates the effects of interactions between biotic and abiotic components of a complex aquatic ecosystem model. A stochastic analysis shows that the variance of the abiotic variables is related in a simple manner to the autocorrelation function of the biotic variables. The results suggest that for oligotrophic and eutrophic conditions, relatively simple ecosystem models may be sufficient for studies of an aquatic environment. Under mesotrophic conditions, the high state variable resolution of a complex model may be necessary.     

Intrauterine brain teratoma: a case report of imaging (US,MRI) with neuropathologic correlations

Fetal brain tumors are rare and teratoma is considered as the most common. Fetal MR Imaging is currently used to evaluate cases of ventricular dilatation. We report a case of cerebral immature teratoma detected by ultrasonography because of ventricular dilatation at 24 gestational weeks. MRI was the more accurate imaging method in depicting the tumor and its consequences on brain development as well as in taking a decision with regard to the management of pregnancy. Copyright © 2003 John Wiley & Sons, Ltd.     

产奶量增多的基因选择与奶牛福利:是否需要新的育种目标?

在许多欧洲国家,平均每头奶牛的产奶量比40年前翻了一番.但随之而来的是奶牛生殖能力的降低,健康问题的增多以及寿命的减少.为了提高产奶量和利润,基因选择得到广泛应用.但人们认为这是以牺牲奶牛的福利为代价换来的.乳制品业的经济前景是与公众对育种方式的接受程度和生产方式直接相关的.对乳业来说,在遭到公众更广泛的对繁殖和管理的谴责之前,很好地解决奶牛的福利问题是很重要的.为了阻止奶牛生命质量的下降或使之提高,需要制定新的育种目标,以改善健康和对代谢压力的耐力.