Intake characteristics of perennial ryegrass varieties when grazed by sheep under continuous stocking management

Fifteen intermediate-heading varieties of perennial rye grass were continuously-stocked with sheep during two years and sward surface height was maintained in the range of 4 to 5 cm. Large differences in daily dry matter intake ewe^-1 were observed between the varieties suggesting that there is considerable scope for breeding improved varieties for grazing. Compared with the mean in each year, the ranges in values were proportionately 0.81 to 1.24 in 1998and 0.80 to 1.19 in 1999. Highest intakes were measured for sheep grazing 2 tetraploid hybrid varieties which also had markedly higher live weight gains ewe^-1 and ha^-1 compared with those grazing the 9 diploid and 4 tetraploid varieties examined. Daily intakes were not correlated with eating time but were correlated with intake rate min^-1eating (r = 0.73 and 0.88 in 1998 and 1999,respectively). Animals appeared unable to compensate fully for low intake rate by increasing eating time. Intake rates were not correlated with green leaf mass, the number of grass tillers m^-2 or water soluble carbohydrate concentrations in grass snips from the grazed horizon. High intake rates were achieved not only by sheep grazing highly-tillered diploid varieties but also by those grazing tetraploid hybrids with fewer tillers m^-2. Other plant morphological and chemical attributes need to be explored to determine what factors might influence the intake characteristics of varieties destined for grazing so that new target traits can be identified and improved methods can be developed to screen rapidly for these traits during breeding programmes and during variety evaluation. This revised version was published online in July 2006 with corrections to the Cover Date.     

我国禽用活疫苗生产SPF化势在必行

改革开放以来,随着我国畜牧业持续、健康和稳定的发展,畜产品质量与产量显著提高.据统计,2006年畜牧业总产值约1.4万亿元,占农业总产值的34%.肉、蛋、奶产量分别达到7 980、2 940和3 290万吨,比2000年分别增长58.8%、25.8%和193%,我国肉、蛋总产量已名列世界首位,奶产量跃居世界第五位.畜牧业的成就与我国畜禽疫病防治水平的提高密不可分,由于我国养殖业的生物安全管理比较差,主要靠疫苗免疫接种防控畜禽疫病.免疫接种安全、高效的疫苗是防控家禽疫病的关键,而实行禽用活疫苗的SPF化生产是保证疫苗纯净安全、有效的重要手段.……     

Optimizing Electrical Activation of Porcine Oocytes by Adjusting Pre‐ and Post‐Activation Mannitol Exposure Times

Modifying electrical activation conditions have been used to improve in vitro embryo production and development in pigs. However, there is insufficient information about correlations of porcine embryo development with oocyte pre‐ and post‐activation conditions. The purpose of this study was to compare the developmental rates of porcine oocytes subjected to different mannitol exposure times, either pre‐ or post‐electrical activation, and to elucidate the reason for the optimal mannitol exposure time. Mannitol exposure times around activation were adjusted as 0, 1, 2 or 3 min. Blastocyst development were checked on day 7. Exposure of oocytes to mannitol for 1 or 2 min before electrical activation produced significantly higher blastocyst rates than exposure for 0 or 3 min. There was no significant difference in blastocyst rates when activated oocytes were exposed to mannitol for 0, 1, 2 or 3 min after electrical activation. While exposure of oocytes to mannitol for 1 min pre‐ and 3 min post‐activation showed significantly higher blastocyst development than 0 min pre‐ and 0 min post‐activation. It also showed higher maintenance of normal oocyte morphology than exposure for 0 min pre‐ and 0 min post‐activation. In conclusion, exposure of oocytes to mannitol for 1 min pre‐ and 3 min post‐activation seems to be optimal for producing higher in vitro blastocyst development of porcine parthenogenetic embryos. The higher blastocyst development is correlated with higher maintenance of normal morphology in oocytes exposed to mannitol for 1 min pre‐ and 3 min post‐activation.     

Entangling macroscopic diamonds at room temperature

Quantum entanglement in the motion of macroscopic solid bodies has implications both for quantum technologies and foundational studies of the boundary between the quantum and classical worlds. Entanglement is usually fragile in room-temperature solids, owing to strong interactions both internally and with the noisy environment. We generated motional entanglement between vibrational states of two spatially separated, millimeter-sized diamonds at room temperature. By measuring strong nonclassical correlations between Raman-scattered photons, we showed that the quantum state of the diamonds has positive concurrence with 98% probability. Our results show that entanglement can persist in the classical context of moving macroscopic solids in ambient conditions.     

Rotational and translational mobility of small molecules in sucrose plus polysaccharide solutions

The effect of different polysaccharides on the rotational (D(rot)) and translational diffusion (D(trans)) coefficients of small molecules in concentrated systems (sucrose solutions) was investigated. Dextran (1 or 10% w/w) with different molecular masses (from 10(4) to 2 x 10(6) Da), gum arabic, or pullulan was added to solutions of sucrose (57.5% w/w). Viscosity measurements of the diffusion medium studied (sucrose and sucrose plus polysaccharide) were made using a Rheometric Scientific viscometer in a temperature range from 20 to -10 degrees C. The rotational mobility of nitroxide radicals (Tempol) dispersed in the concentrated systems was measured by electron spin resonance. The translational diffusion coefficient of fluorescein was determined by the fluorescence recovery after photobleaching method. The studied temperature range for the latter two techniques was from 20 to -16 degrees C. For these conditions of concentration and temperature, there was no ice formation in the samples. No effect of the molecular mass of dextran on D(rot) and D(trans) was observed when solutions with the same dry matter content were compared. Only pullulan and gum arabic, at 10%, had a significant effect on D(trans)( )()of fluorescein. Temperature and total dry matter content were observed to be the most important factors controlling D(rot) and D(trans) in these concentrated systems.     

Aroma volatility from aqueous sucrose solutions at low and subzero temperatures

The gas-liquid partition coefficients of ethyl acetate and ethyl hexanoate have been measured in water and aqueous sucrose solutions from 25 to -10 degrees C by dynamic headspace. Experiments were carried out on sucrose solutions at temperatures where no ice formation was possible. Results showed that when sucrose concentration increased, aroma volatility increased except for ethyl hexanoate and in the highest sucrose concentration solution (57.5%). A quasi-linear temperature decrease on aroma volatility was observed in sucrose solutions from 25 to around 4 and 0 degrees C. Then, from 0 to -10 degrees C, aroma volatility did not decrease: ethyl acetate volatility remained constant but that of ethyl hexanoate increased. Enthalpy of vaporization and activity coefficients of the aroma compounds were calculated.     

Colliding beam fusion reactor

Recent results with Tokamak experiments provide insights into the problem of magnetic confinement. They demonstrate how to avoid anomalous transport and thus solve the major problems of Tokamak reactors: size, the production of 14-megaelectron volt neutrons, and maintenance. An alternate confinement system, the field-reversed configuration, confines beams of protons and boron-11. For the proton-boron-11 fusion reaction, the fusion products are all charged particles for which direct conversion is feasible and neutron flux is negligible.     

Complex Shear Wave Velocity Structure Imaged Beneath Africa and Iceland

A model of three-dimensional shear wave velocity variations in the mantle reveals a tilted low velocity anomaly extending from the core-mantle boundary (CMB) region beneath the southeastern Atlantic Ocean into the upper mantle beneath eastern Africa. This anomaly suggests that Cenozoic flood basalt volcanism in the Afar region and active rifting beneath the East African Rift is linked to an extensive thermal anomaly at the CMB more than 45 degrees away. In contrast, a low velocity anomaly beneath Iceland is confined to the upper mantle.