Effects of stocking density on the growth and immunity of Atlantic salmon salmo salar reared in recirculating aquaculture system(RAS)

Atlantic salmon reared in recirculating aquaculture system(RAS) may lead to inappropriately high stocking density, because ?sh live in a limited space. Finding the suitable stocking density of Atlantic salmon reared in RAS is very important for RAS industry. In this paper, the in?uence of stocking density on growth and some stress related physiological factors were investigated to evaluate the ef fects of stocking density. The ?sh were reared for 220 days at ?ve densities(A: 24 kg/m^3; B: 21 kg/m^3; C: 15 kg/m^3; D: 9 kg/m^3 and E: 6 kg/m^3). The results show that 30 kg/m^3 might be the maximum density which RAS can af ford in China. The stocking densities under 30 kg/m^3 have no ef fect on mortality of Atlantic salmon reared in RAS. However, the speci?c growth rate(SGR), ?nal weight and weight gain in the high density group were signi?cantly lower than the lower density groups and middle density groups. Moreover, feed conversion rate(FCR) had a negative correlation with density. Plasma hormone T_3 and GH showed signi?cant decrease with the increase of the stocking density of the experiment. Furthermore, thyroid hormone(T 3), GH(growth hormone) activities were decreased with stocking density increase. However, plasma cortisol, GOT(glutamic oxalacetic transaminase) and GPT(glutamic pyruvic transaminase) activities were increase with stocking density increase. And the stocking density has no ef fects on plasma lysozyme of Atlantic salmon reared in RAS. These investigations would also help devise effcient ways to rear adult Atlantic salmon in China and may, in a way, help spread salmon mariculture in China.     

大西洋上四个爆发性气旋的云微物理参量垂直分布特征分析

利用CloudSat卫星数据处理中心(CloudSat Data Processing Center,CloudSat DPC)提供的CloudSat卫星数据、欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)提供的ERA5再分析资料和美国国家航空航天局(National Aeronautics and Space Administration,NASA)提供的Aqua卫星可见光云图,对冬春季发生在大西洋上四个爆发性气旋个例的云微物理参量垂直分布特征进行了分析。结果表明:爆发性气旋中心云系多为层积云或积云,中心外围云系以雨层云为主,雨层云外部往往伴随着相似高度的高层云,气旋冷锋云带内以雨层云、高层云和高积云为主,冰粒子出现的最低高度与0℃等温线高度几乎重合;冰粒子有效半径随高度的增加而减小,而冰粒子数浓度随高度增加而增大;冰水含量大值区主要位于雨层云中部;液态水主要分布在高层云和层积云底部,冬季爆发性气旋个例内的液态水含量大于春季。     

A photometric and spectroscopic study of the brightest northern Cepheids — II. Fundamental physical parameters

We present a new Cepheid reddening and effective temperature scale based on the uvby photometry published in the first paper of this series. Using all available information about the companion stars in Cepheids with bright blue secondaries, we remove their light from the observed light and colour curves. The resulting corrections are as large as 0.05–0.15 mag in several cases for different colour indices. A new photometric approach based on the ( b  −  y ) versus ( B  − V ) two-colour diagram is tested with three other previous calibrations taken from the literature. Two uvby relations in earlier studies turn out to be the most reliable and consistent, and so they are used in deriving colour excesses. We determine systematically higher reddenings for Cepheids with a significant secondary light correction. The dereddened Stro¨mgren colours are calibrated in terms of T _eff and log  g using the most recent synthetic colour grids. Our temperature scale is very close to that of Kraft, which is supported by other recent temperature determinations using the infrared flux method or Geneva photometry. The photometric gravities fit some of the earlier theoretical and observational (mainly spectroscopic) results very well.     

Signals from the epoch of cosmological recombination – Karl Schwarzschild Award Lecture 2008

The physical ingredients to describe the epoch of cosmological recombination are amazingly simple and well‐understood. This fact allows us to take into account a very large variety of physical processes, still finding potentially measurable consequences for the energy spectrum and temperature anisotropies of the Cosmic Microwave Background (CMB). In this contribution we provide a short historical overview in connection with the cosmological recombination epoch and its connection to the CMB. Also we highlight some of the detailed physics that were studied over the past few years in the context of the cosmological recombination of hydrogen and helium. The impact of these considerations is two‐fold: (i) The associated release of photons during this epoch leads to interesting and unique deviations of the CosmicMicrowave Background (CMB) energy spectrum from a perfect blackbody, which, in particular at decimeter wavelength and the Wien part of the CMB spectrum, may become observable in the near future. Despite the fact that the abundance of helium is rather small, it still contributes a sizeable amount of photons to the full recombination spectrum, leading to additional distinct spectral features. Observing the spectral distortions from the epochs of hydrogen and helium recombination, in principle would provide an additional way to determine some of the key parameters of the Universe (e.g. the specific entropy, the CMB monopole temperature and the pre‐stellar abundance of helium). Also it permits us to confront our detailed understanding of the recombination process with direct observational evidence. In this contribution we illustrate how the theoretical spectral template of the cosmological recombination spectrum may be utilized for this purpose. We also show that because hydrogen and helium recombine at very different epochs it is possible to address questions related to the thermal history of our Universe. In particular the cosmological recombination radiation may allow us to distinguish between Compton y ‐distortions that were created by energy release before or after the recombination of the Universe finished. (ii) With the advent of high precision CMB data, e.g. as will be available using the PLANCK Surveyor or CMBPOL, a very accurate theoretical understanding of the ionization history of the Universe becomes necessary for the interpretation of the CMB temperature and polarization anisotropies. Here we show that the uncertainty in the ionization history due to several processes, which until now were not taken in to account in the standard recombination code RECFAST, reaches the percent level. In particular He II → He I recombination occurs significantly faster because of the presence of a tiny fraction of neutral hydrogen at z ∼ 2400. Also recently it was demonstrated that in the case of H I Lyman α photons the timedependence of the emission process and the asymmetry between the emission and absorption profile cannot be ignored. However, it is indeed surprising how inert the cosmological recombination history is even at percent‐level accuracy. Observing the cosmological recombination spectrum should in principle allow us to directly check this conclusion, which until now is purely theoretical. Also it may allow to reconstruct the ionization history using observational data (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)