牧压对天山北坡山地草甸植物养分含量的影响

探讨不同放牧强度下山地草甸植物营养成分的变化,并从牧草营养变化角度寻找最佳放牧组合方式。按照零放牧、适度放牧和重度放牧三个梯度进行试验设计,在放牧前和放牧结束时测定草地植物粗蛋白质、粗脂肪、NDF、ADF、Ca、P。试验结果表明,放牧前各处理粗蛋白和粗脂肪均较放牧后粗蛋白和粗脂肪含量高,放牧结束后,适度放牧和重度放牧间差异显著(P<0.05),零放牧与适度放牧和重度放牧间差异极显著(P<0.01)。放牧前三个处理的NDF和ADF含量不在同一水平上,但仅表现在P<0.05水平上,放牧后,NDF和ADF在各处理下都略有增加,三个处理间表现出极显著差异(P<0.01)。放牧前,Ca和P含量在三个处理间差异不显著,放牧后,Ca含量在零放牧和适度放牧间差异显著(P<0.05),P含量在各处理间差异不显著。     

A note on motor laterality in plains zebras (Equus burchellii) and impalas (Aepyceros melampus)

This observational field study used intermittent still photography to examine the distribution of motor laterality in images of two African grazing quadruped species: plains zebras (Equus burchellii) and impalas (Aepyceros melampus). Zebra images (n=708) had a laterality index of ?6.21 and a Z-score of ?1.65 (p=.098). Impala images (n=318) had a laterality index of ?18.87 and a Z-score of ?3.36 (p=.0008). The weak left motor bias in zebras aligns with that reported in domestic horses using a related method.     

Evidence of sp2-like Hybridization of Silicon Valence Orbitals in Thin and Thick Si Grown on α-Phase Si(111)√3 × √3R30°-Bi

One-monolayer (ML) (thin) and 5-ML (thick) Si films were grown on the α-phase Si(111)√3 × √3R30°-Bi at a low substrate temperature of 200 °C. Si films have been studied in situ by reflection electron energy loss spectroscopy (REELS) and Auger electron spectroscopy, as a function of the electron beam incidence angle α and low-energy electron diffraction (LEED), as well as ex situ by grazing incidence X-ray diffraction (GIXRD). Scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS) were also reported. The REELS spectra, taken at the Si K absorption edge (~1.840 KeV), reveal the presence of two distinct loss structures attributed to transitions 1s→π* and 1s→σ* according to their intensity dependence on α, attesting to the sp²-like hybridization of the silicon valence orbitals in both thin and thick Si films. The synthesis of a silicon allotrope on the α-phase of Si(111)√3 × √3R30°-Bi substrate was demonstrated by LEED patterns and GIXRD that discloses the presence of a Si stack of 3.099 (3) Å and a √3 × √3 unit cell of 6.474 Å, typically seen for multilayer silicene. STM and STS measurements corroborated the findings. These measurements provided a platform for the new √3 × √3R30° Si allotrope on a Si(111)√3 × √3 R30°-Bi template, paving the way for realizing topological insulator heterostructures from different two-dimensional materials, Bi and Si.     

Side Chain Influence on the Mechanical Properties and Water Uptake of Confined Comb‐Shaped Cationic Polymer Thin Films

Water uptake is measured for ≈100 nm and ≈60 μm thick quaternized comb‐shaped poly(2,6‐dimethyl‐1,4‐phenylene oxide) (QA‐PPO) polymers with 0, 6, 10, and 16 carbon alkyl side chains to probe the influence of thin film confinement. The thin film modulus is measured to probe the effect of side chain length on the thin film modulus and the ensuing water uptake. Increasing the alkyl side chain length results in increased modulus, decreased swelling strain, and decreased water uptake due to the lengthening of the n‐alkyl side chains. Confinement effects on the comb‐shaped QA‐PPO water uptake are expressed through increased water uptake in the thin film compared to the bulk membrane. The thin films also exhibit a different water sorption mechanism consistent with two types of water compared to the bulk membranes that exhibit a single type of water sorption.

     

Trade patterns facilitating highly pathogenic avian influenza virus dissemination in the free‐grazing layer duck system in Vietnam

Highly pathogenic avian influenza (HPAI ) viruses continue to threaten smallholder poultry producers in several South‐east Asian countries, including Vietnam. In particular, the free‐grazing duck system has been repeatedly highlighted as a major risk factor for HPAI outbreaks. Free‐grazing ducks, which scavenge on rice paddies after the harvest, account for a large proportion of the duck population in Vietnam and the wider South‐east Asian region. However, the structure and dynamics of the free‐grazing duck production from farm to consumption has not been described for Vietnam. In this study, we used a value chain approach to provide a complete picture of the actors involved in the production and marketing of free‐grazing duck eggs and spent layer ducks, as well as to investigate the governance structure of this food system. Group interviews and key informant interviews were conducted in two provinces located in the Mekong River Delta (MRD) and the Red River Delta (RRD). The results presented here highlight similarities and differences in farming and trade practices between the two provinces. The trade of spent layer ducks involved large volumes of live ducks being sent to China and Cambodia for consumption, generating a substantial risk of transboundary spread of pathogens, including HPAI viruses. We describe the major role of “duck yards”, which act as hubs in the northbound trade of spent layer ducks. These yards should be considered as essential links in the value chain of spent layer ducks when considering HPAI surveillance and control. The veterinary authorities are only marginally involved in the value chain activities, and their influence could be strengthened by increasing surveillance activities for instance in duck yards. Last, we discuss the dynamics of the duck value chain and further implications for future HPAI management policies.     

家牦牛与野牦牛混群放牧杂交育种初步试验

本试验选择健康达标的家养母牦牛,经过适应性培育后,在发情季节与野牦牛混群放牧,采用自然交配手段导血培育半野血牦牛探索,成功获得了39头半野血牦牛(23公,16母),为今后在混群放牧条件下获得半野血牦牛积累了经验。     

Association between eating frequency, weight, and health

There is speculation amongst health professionals, the media, and the public regarding eating frequency (EF) and its impact on weight and health. Nutritional weight-loss and -maintenance interventions of longer than 1 week's duration were reviewed for associations between EF and weight and health. Of the 176 studies identified, 25 relevant studies matched the criteria and only 10 of these were weight-loss interventions. Generally, sample sizes were small, interventions were short-term, and a wide array of definitions was used to define an eating occasion. Several key outcomes such as physical activity, adherence to assigned EF, and hunger were often not measured. The limited evidence available suggests there is no association between EF and weight or health in either weight-loss or -maintenance interventions, with a possible inverse association between EF and lipids in weight-maintenance interventions. Longer term, larger studies that include important weight and health outcomes are needed.     

Significance of Viral Activity for Regulating Heterotrophic Prokaryote Community Dynamics along a Meridional Gradient of Stratification in the Northeast Atlantic Ocean

How microbial populations interact influences the availability and flux of organic carbon in the ocean. Understanding how these interactions vary over broad spatial scales is therefore a fundamental aim of microbial oceanography. In this study, we assessed variations in the abundances, production, virus and grazing induced mortality of heterotrophic prokaryotes during summer along a meridional gradient in stratification in the North Atlantic Ocean. Heterotrophic prokaryote abundance and activity varied with phytoplankton biomass, while the relative distribution of prokaryotic subpopulations (ratio of high nucleic acid fluorescent (HNA) and low nucleic acid fluorescent (LNA) cells) was significantly correlated to phytoplankton mortality mode (i.e., viral lysis to grazing rate ratio). Virus-mediate morality was the primary loss process regulating the heterotrophic prokaryotic communities (average 55% of the total mortality), which may be attributed to the strong top-down regulation of the bacterivorous protozoans. Host availability, encounter rate, and HNA:LNA were important factors regulating viral dynamics. Conversely, the abundance and activity of bacterivorous protozoans were largely regulated by temperature and turbulence. The ratio of total microbial mediated mortality to total available prokaryote carbon reveals that over the latitudinal gradient the heterotrophic prokaryote community gradually moved from a near steady state system regulated by high turnover in subtropical region to net heterotrophic production in the temperate region.     

Organized Silica Films Generated by Evaporation-Induced Self-Assembly as Hosts for Iron Oxide Nanoparticles

In this work, we prepared oriented mesoporous thin films of silica on various solid substrates using the pluronic block copolymer P123 as a template. We attempted to insert guest iron oxide (Fe_xO_y) nanoparticles into these films by two different methods: (a) by co-precipitation—where iron precursors are introduced in the synthesis sol before deposition of the silica film—and subsequent oxide production during the film calcination step; (b) by preparing and calcining the silica films first then impregnating them with the iron precursor, obtaining the iron oxide nanoparticles by a second calcination step. We have examined the structural effects of the guest nanoparticles on the silica film structures using grazing incidence X-ray scattering (GISAXS), high-resolution transmission electron spectroscopy (HRTEM), spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and Raman microscopy. Formation of nanoparticles by co-precipitation may induce substantial changes in the film structure leading, in our adopted process, to the appearance of lamellar ordering in the calcination stage. On the contrary, impregnation-based approaches perturb the film structures much more weakly, but are also less efficient in filling the pores with nanoparticles.     

Pinus halepensis invasion in mountain pampean grassland: effects of feral horses grazing on seedling establishment

We evaluated the mechanisms that determine the increasing abundance of Pinus halepensis in mountain pampean grasslands in Argentina that is associated with the continuous presence of feral horses. We hypothesized that direct and indirect effects of feral horse grazing on grassland may affect the establishment of P. halepensis. We conducted a field experiment to evaluate this hypothesis, studying the response of seedling emergence, survival and growth to herbaceous vegetation defoliation and soil disturbance in sites with contrasting grazing histories. We also evaluated the composition and structure of plant communities of each experimental site. Direct effects such as heavily defoliated perennial grasses and indirect effects such as reduced specific and functional richness, diversity and evenness enhanced the emergence, survival and early growth of the seedlings. High bare ground percentage and low grass biomass also positively affected seedling establishment. The experimental evidence demonstrates that the combination of invasional meltdown hypothesis and weakened biotic resistance are the mechanisms involved in P. halepensis invasion.