A simple way of avoiding feed wastage in European seabass,Dicentrarchus labrax,under self-feeding conditions

Self-feeding systems allow fish to freely express feeding activity. A simple rod at the water surface can act as a trigger and provide fish with a way of obtaining pellets from a feeder. Such a rod presented to experienced European seabass, Dicentrarchus labrax, may lead to feed wastage, probably as a result of unintentional fish contacts with the trigger. Trigger protection screens have been designed to prevent fish contacting the trigger by chance, and the efficacy of such screens was tested. Nocturnal and diurnal feed delivery and feed wasted were compared under conditions where the rod was unprotected or protected by semi-cylindrical or cylindrical screens. Tests were conducted using an unrestricted self-feeding regime (reward: 0.2 g pellet per kg of body weight and per fish contact) in juvenile seabass (57 g body weight) fed for 28 days at 21.3 °C. Fish were subjected to a 4-h L:20-h D (light:dark) photoperiod. The daily feed demand pattern and the nocturnal and diurnal feed wastage were recorded. Fish activated the trigger predominantly at night, except in the case of one group exposed to a trigger protected by a semi-cylindrical screen. In the latter, triggering activity was progressively distributed throughout the light:dark cycle. The cylindrical screens markedly reduced feed wastage and seabass were able to locate and activate the trigger (even in total darkness) to obtain a reward.     

Ethylenediurea(EDU) effects on Japanese larch: an one growing season experiment with simulated regenerating communities and a four growing season application to individual saplings

J apanese larch(La rix kaempferi(Lamb.) Carr.)and its hybrid are economically important coniferous trees widely grown in the Northern Hemisphere.Ground-level ozone(O_3) concentrations have increased since the preindustrial era,and research projects showed that Japanese larch is susceptible to elevated O_3 exposures.Therefore,methodologies are needed to(1) protect Japanese larch against O_3 damage and(2) conduct biomonitoring of O_3 in Japanese larch forests and,thus,monitor O_3 risks to Japanese larch.For the first time,this study evaluates whether the synthetic chemical ethylenediurea(EDU) can protect Japanese larch against O_3 damage,in two independent experiments.In the first experiment,seedling communities,simulating natural regeneration,were treated with EDU(0,100,200,and 400 mg L~(-1)) and exposed to either ambient or elevated O_3 in a growing season.In the second experiment,individually-grown saplings were treated with EDU(0,200 and 400 mg L~(-1)) and exposed to ambient O_3 in two growing seasons and to elevated O_3 in the succeeding two growing seasons.The two experiments revealed that EDU concentrations of 200-400 mg L~(-1) could protect Japanese larch seedling communities and individual saplings against O_3-induced inhibition of growth and productivity.However,EDU concentrations ≤200 mg L~(-1) did offer only partial protection when seedling communities were coping with higher level of O_3-induced stress,and only 400 mg EDU L~(-1) fully protected communities under higher stress.Therefore,we conclude that among the concentrations tested the concentration offering maximum protection to Japanese larch plants under high competition and O_3-induced stress is that of 400 mg EDU L~(-1).The results of this study can provide a valuable resource of information for applied forestry in an O_3-polluted world.     

风沙区高等级公路设施与路基高度耦合对气流动力学和蚀积特征的影响

[目的] 揭示风沙地区不同高度高等级公路附属设施对过境风沙流的扰动效应,分析不同高度与公路设施影响下的公路路面积沙程度,为公路工程设计和穿沙公路防护措施的制定提供理论依据。 [方法] 采用了计算流体力学(CFD)数值模拟方法,将普通公路作为对照,对比分析不同路基高度和公路设施组合对近地表过境气流的影响,并通过野外实测数据进行验证。 [结果] 公路设施显著影响了路基过境气流,导致公路形成减速区,不同高度路基产生多样性的水平气流速度变化。当路基高度在1～2 m之间时,气流扰动较弱,有助于断面输沙;当路基高度在3 m高度时,气流扰动较强,不利于断面输沙。气流穿过护栏和中央隔离带时,气流从护栏下方经过,风速增加,护栏背风侧最大风速的距离随着路基高度的增加呈现先增加再减小的变化趋势,路基高度在0,1,2,3 m时,最大风速距离分别为10,20,25,20 cm。随后在护栏背风侧与上层气流合并,尾流持续扩散,形成减速区,过境气流在该区域发生衰减,沙粒颗粒产生沉积,最高积沙高度11.5 cm,积沙宽度4～4.5 m。 [结论] 路基高度和公路附属设施是影响公路沿线沙害的主要因素。路基高度对气流到达路基上方的风速产生显著影响,而护栏和防眩网的存在可能在背风侧形成弱风区,从而导致公路上的沙堆积,存在潜在危险。     

The Planning Management Experience and Enlightenment of the Cityscape Inheritance of the Ancient City of Yangzhou

China is currently facing the problem of large-scale destruction of the overall cityscape brought about by the rapid development of the city. The optimization of urban stocks and the improvement of urban quality have become the necessary paths for major cities to improve their urban soft power and obtain secondary economic growth. At present, most cities in China are still in the exploratory period of the protection of the cityscape, facing the dilemma of various ways but poor effects. Since the 1990 s, Yangzhou has begun to protect and inherit the cityscape, accumulating systematic protection methods and retaining the complete cityscape. This paper analyzed the characteristic cityscape of the ancient city of Yangzhou, sorted out its strategic methods in the planning management, and summarized the local experience in the inheritance of the characteristic cityscape, in order to provide a reference for China's future cityscape protection work.     

内蒙古自治区城市土地承载力与城镇化水平的协同关系分析

为探寻城市土地承载力与城镇化水平之间的协同关系,以内蒙古自治区为案例区,采用TOPS1S模型对城市土地承载力与城镇化水平进行测度;在相关性分析的基础上,基于Tapio脱钩模型分析2001-2018年城市土地承载力和城镇化水平之间的协同关系.结果表明:1)2018年内蒙古自治区城市土地承载力均值为0.268,呼和浩特市、...     

Audio-visual interaction and visitor characteristics affect perceived soundscape restorativeness: Case study in five parks in China

The capacity of urban parks to contribute to soundscape restorativeness, understood here as contributions to people’s recovery from attentional fatigue and reflection on life issues, is receiving increased interest in research and policy. However, scientific understanding of the influential mechanism of perceived soundscape restorativeness is still not clear. This paper aims to explore the effects of audio-visual interaction on perceived soundscape restorativeness (PSR) of urban parks, considering visitors of different social and demographic characteristics. The research design comprises a survey of 419 visitors to five urban parks in Fuzhou, China, general structure equation modeling, and multi-group model analysis. The results show a substantial dependence of visitors’ PSR values on respective perceptions of soundscape pleasantness and eventfulness, especially soundscape pleasantness. Visual landscape characteristics showed mediating effects on the influence of soundscape pleasantness and eventfulness on the perceived soundscape restorativeness (19.3 % and 28.3 % of the total effect, respectively). Age was the most influential social and demographic characteristic affecting the PSR, followed by gender, while occupation and educational background showed only limited effects. Future development of urban parks should strongly integrate soundscape design considerations to enhance positive PSR effects for visitors.     

Radon profiles in the Indonesian archipelago

A series of near-bottom excess radon profiles was measured in the Indonesian archipelago during the Snellius-II Expedition. The results show considerable variations in structure, ²²²Rn concentrations and integrated excess ²²²Rn inventory in the water column. Near-bottom vertical eddy diffusion coefficients vary from 46.4 to 63.6 cm²·s⁻¹ in the basins; they are in general much higher on slopes and sills. The standing crop (the integrated amount of excess ²²²Rn) ranges from 0.9 to 49.6 dpm·cm⁻². ²²⁶Radium supported ²²²Rn concentrations range from 9 to 3888·10⁻² dpm·kg⁻¹ Compared to mid-ocean basins the vertical mixing processes of near-bottom water masses in the Indonesian archipelago is fast, especially in the water layer from 50 to 200 m above the bottom, with diffusion coefficients in the order of 10 times higher than in the Pacific Ocean. With the exception of two stations standing crop values were comparable with those found in the Pacific Ocean but higher than those from the Atlantic Ocean. ²¹⁰Pb analyses show high sedimentation rates, up to 75 cm·10⁻³·a⁻¹. This does not agree with related standing crops. One explanation can be that erosion plays an important role on the sills and slopes.