研究和发展益生菌和益生元的前瞻

人体的结肠微生物区对健康有着极大的影响。自从引入益生菌和益生元的概念后,对人体肠微生物区组成的观点产生了极大的变化,详细研究复杂的细菌群落一直是个巨大的挑战。用抽样法研究肠微生物群将会更加成熟,并广泛应用于此项研究中。目前,以核酸为基础的分析方法是研究肠微生物区系的基本工具。应用先进的分子技术,使点查和鉴定结肠细菌的种类以及族系级别成为可能。目前正在对第二代益生元的概念展开广泛研究。了解内脏生态系统的作用机制以及处于内脏生态系统中的细菌的作用机制,对于益生菌和益生元将来的发展极为重要。     

The occurrence of primary burrowing crayfish in terrestrial habitat

A researcher’s perception of a target species’ landscape strongly influences the design of habitat studies conducted at broad spatial scales. Consequently, researcher-dependent perceptions may misguide conservation efforts. Although the life histories of some crayfish (i.e., primary burrowers) are centered on a fossorial existence independent of surface water, all North American crayfish are viewed in an aquatic context. This paradigm restricts the range of habitats that are typically sampled and managed for crayfish conservation. This study used presence/absence of the primary burrower Distocambarus crockeri at 137 locations within the Long Cane Ranger District of the Sumter National Forest, South Carolina, USA, to model the habitat association of the species across a GIS-based landscape. Logistic regression indicated that D. crockeri presence was most strongly associated with a terrestrial habitat defined by a set of morphologically similar soils located along ridge tops. Furthermore, the species was negatively associated with aquatic habitats such as streams and floodplains. The results indicate that D. crockeri is a terrestrial habitat specialist and should be modeled and managed at the landscape as a terrestrial organism. When viewed as a subset of the total United States cambarid fauna, primary burrowers are disproportionately imperiled. Primary burrowers comprise only 15% of the total crayfish fauna, while they account for 32% of those crayfish ranked critically imperiled. Habitat loss and an aquatic bias that restricted sampling to aquatic and semi-aquatic habitats might explain the group’s disproportionate imperilment.     

Electrodeposited ceramic superlattices

Ceramic superlattices have been produced by electrodeposition with modulation wavelengths in the range from 5 to 10 nanometers. The TlaPbbOc/TldPbeOf superlattices were deposited from a single aqueous solution at room temperature, and the layer thicknesses were galvanostatically controlled. The films showed strong preferred orientation and distinct first-order satellites around the Bragg reflections in the x-ray diffraction pattem. The modulation wavelengths calculated from the satellite spacings were in agreement with those calculated from Faraday's law. Because the modulation wavelengths are of electron mean free path dimensions, this dass of degenerate semiconductor metal-oxide superlattices may exhibit thickness-dependent quantum optical, electronic, or optoelectronic effects.     

Toxic and protective constituents in pet foods

An analytical survey of mutagens, nitrosamines, polychlorinated biphenyls, toxic elements, and gamma-emission, as well as the toxicologically protective constituents zinc, selenium, and vitamin C, in 48 pet foods was conducted. Aside from high concentrations of fluoride and iodide in some samples and the expectedly higher concentrations of mercury and selenium in certain cat foods containing fish, the samples were notably free of the other toxic constituents. Direct-acting and promutagens and nitrosamines were not detectable in any of the samples. gamma-Emission was very low in all of the foods. Polychlorinated biphenyls were only detected in one cat food.     

Host range of avian influenza virus in free-living birds

Isolation of avian influenza virus (AIV) has been reported from 12 orders and 88 species of free-living birds. Most isolations are reported from species in the orders Anseriformes and Charadriiformes and it is recognized that species in Anseriformes represent important reservoirs of AIV. Morbidity and mortality among free-living birds attributable to AIV infection are rare, but differences in prevalence of AIV occur within and between avian species. Seasonal variation has been reported from free-living and sentinel ducks with peak AIV infection occurring in late summer and early fall. Prevalence of AIV is age-related, with highest isolation rates reported from juvenile birds. Differences in susceptibility to AIV infection among species have been demonstrated under experimental conditions. The dynamics and epidemiology of species-related variation in populations of free-living birds require further study.     

疾病对世界家禽业的影响

疾病问题一直就是家禽业的一个部分。一些疾病很容易被控制，而另一些疾病应值得更多关注。家禽业的集约化看来正在付出代价。     

Residue retention mitigated short-term adverse effect of clear-cutting on soil carbon and nitrogen dynamics in subtropical Australia

Purpose

This study aimed to investigate the benefits of retaining harvest residues on the dynamics of soil C and N pools following clear-cut harvesting of a slash pine plantation in South East Queensland of subtropical Australia.

Materials and methods

Immediately following clear-cut harvesting, macro-plots (10?×?10 m) were established on a section of the plantation in a randomised complete block design with four blocks and three treatments: (1) residue removal (RR₀), (2) single level of residue retention (RR₁) and (3) double level of residue retention (RR₂). Soils were sampled at 0, 6, 12, 18 and 24 months following clear-cutting and analysed for total C and N, microbial biomass C (MBC) and N (MBN), hot water–extractable organic C (HWEOC), hot water–extractable organic N (HWEON), NH₄⁺–N and NO_x^?–N.

Results and discussion

The study showed that although soil total C decreased in the first 12 months following clear-cutting, harvest residue retention increased soil total C and N by 45% (p?<?0.001) and 32% (p?<?0.001), respectively, over the 12–24 months. NH₄⁺–N, HWEOC, HWEON and MBC showed initial surges in the first 6 months irrespective of residue management, which declined after the 6th month. However, residue retention significantly increased HWEOC and HWEON over the 12–24 months (p?<?0.001).

Conclusions

This study demonstrated that harvest residue retention during the inter-rotation period can minimise large changes in C and nutrient pools, and can even increase soil C and nutrient pools for the next plantation rotation.