Effect of seaweed proliferation on benthic habitat quality assessed by Sediment Profile Imaging

Changes in sediment quality, with special reference to benthic habitat conditions resulting from macroalgae overgrowth, were studied in the Venice Lagoon, Italy. Data were collected biweekly in spring and summer from 1993 to 1998 and from 2001 to 2002, as part of the macroalgae growth control strategies managed by the Venice Water Authority-Consorzio Venezia Nuova. Benthic habitat conditions were studied by means of Sediment Profile Imaging, which allowed the collection of several variables: aRPD (apparent redox potential discontinuity), prism penetration depth, presence of anoxia on the surface of the sediment, presence of reduced gas bubbles, stage of benthic colonization. All these variables led to the calculation of an environmental index (Organism–Sediment Index, OSI), which was then related to physical variables and macroalgae abundance. Until 1996, the overall benthic habitat of the Venice Lagoon showed almost stressed conditions; from 1997, the seaweed biomass rapidly declined and the OSI increased significantly. The OSI seemed to be affected by seaweed biomass, sediment compactness and water depth. Macroalgae biomass greater than 4.5 kg/m² led to the complete disappearance of stage III of benthic colonization; values as low as 0.70 kg m² already had a severe impact on recolonization. SPI attributes indicated the main mechanisms that could have contributed to the benthic quality: seaweed proliferation is often followed by rapid decay of macroalgae biomass, especially when present in large amounts. The decrease in seaweed biomass often results in oxygen depletion in the water column and thus in the sediment, preventing complete benthic colonization. This research confirms the importance of in situ rapid reconnaissance surveys to assess the impact of eutrophication on the benthic habitat.     

APPLICATION OF HMB－45 MONOCLONAL ANTIBODY AND S100 PROTEIN IN THE IMMUNOHISTOCHEMICAL DIAGNOSIS OF MELANOMA

ＡＰＰＬＩＣＡＴＩＯＮＯＦＨＭＢ－４５ＭＯＮＯＣＬＯＮＡＬＡＮＴＩＢＯＤＹＡＮＤＳ１００ＰＲＯＴＥＩＮＩＮＴＨＥＩＭＭＵＮＯＨＩＳＴＯＣＨＥＭＩＣＡＬＤＩＡＧＮＯＳＩＳＯＦＭＥＬＡＮＯＭＡＬｉｕＤａｎｙａ（刘丹亚）；ＳｕＢａｏｓｈａｎ（苏宝山）；Ｘｕ...     

振动压路机起振过程分析

运用机械系统虚拟样机软件ADAMS建立了振动压路机激振器的虚拟样机，并利用其进行了振动压路机起振过程的仿真研究，分析了液压系统压力对启动过程中档销受力及对动偏心块和固定偏心块运动学参数的影响。     

AMT换挡品质的研究

电控机械式自动变速器（AMT）具有传动效率高、结构紧凑及工作可靠等优点。介绍了AMT换挡品质的定义及其影响因素，分析了几种影响因素之间的内在关系，并在此理论基础上寻求一种可获得最佳AMT换挡品质的方法。AMT按照其对发动机控制方式的不同，可分为柔性控制和刚性控制结构。     

独墩单铰支座曲线梁桥通病分析及治理

针对目前独墩单铰支座曲线梁桥出现的通病 ,就温度对其梁体的变位影响以及预应力等因素对其支座支反力的作用进行了实例剖析。在此基础上探讨此类桥梁的支承体系的病害整治对策 ,并通过加固实例的监测结果予以验证     

海湾大桥北引道沥青混凝土罩面设计

结合广东省汕汾高速公路汕头海湾大桥北引道路面加铺工程,分析软基路段过渡性路面的病害,提出沥青混凝土路面罩面结构设计和施工中须注意的问题.     

水泥混凝土路面质量病害问题探讨

根据目前水泥混凝土路面建设比较普遍的情况,针对施工中出现比较多的质量病害进行了分析,分别从水泥混凝土路面的裂缝产生的过程,材料、配合比、水灰比、施工操作等对质量的影响,以及产生外观质量缺陷的原因进行了评述.     

桥梁加固技术概述

桥梁加固技术是目前桥梁工程的新热点,选择科学合理的加固方案是保证桥梁加固效果和质量的重要前提.本文结合当前桥梁加固的现状,阐述了桥梁常见病害及其成因、加固主要技术途径及加固方案的确定方法,为桥梁加固提供一些经验,对旧桥加固方法的选用具有一定的参考价值.     

Variational principles in water-wave problems (wave radiation conditions and their variational treatment)

To discuss water-wave problems in unlimited waters, it is important to know what type of wave radiation condition should be placed on a virtual surface corresponding to infinity. For this kind of problem, the Sommerfeld radiation condition is well known. In this article, the condition is extended to treat a case with an incident wave. Furthermore, a more general wave radiation condition is introduced from a different point of view. The above-mentioned wave radiation conditions are introduced into the variational principles of the Kelvin, Hellinnger–Reissner, and Dirichlet type. The Dirichlet-type variational principles are then used in numerical calculations for bending waves in a bar, and the effectiveness of the wave radiation conditions and the variational principles is shown. The numerical results for one-dimensional water-wave problems are then given. As expected, the region required for the numerical solution is reduced drastically compared with that required by the Sommerfeld-type formulation. Furthermore, the amplitude of the diverging wave is obtained in the process of reaching the variational solution. Finally, two-dimensional water-wave problems are briefly discussed. Received: August 9, 2001 / Accepted: September 17, 2001     

Dynamics of inorganic nutrient species in the Bohai seawaters

Within the frame of a Sino-German Joint Research Program, two cruises of “R/V Dong Fang Hong 2” were carried out in September–October 1998 and April–May 1999, respectively, to understand the dynamics of nutrients in the Bohai. Nutrient species (NO₃⁻, NO₂⁻, NH₄⁺, PO₄³⁻ and SiO₃²⁻) are determined colorimetrically on board for five anchor and 30 grid stations. In situ incubation experiments are performed to determine planktonic nutrient uptake and benthic exchange flux. Nutrient concentrations display short-term variability and seasonal change in the Bohai, with higher levels in shallow coastal waters than in the Central Bohai. The influence of riverine discharge on nutrient levels can be seen from salinity isopleths, nutrient distribution and species ratios. Near-bottom (nb) waters have similar nutrient concentrations as to the surface waters in the Central Bohai, whereas stratification takes place in the Bohai Strait and North Yellow Sea. In situ incubation experiments provide evidence that the uptake ratio (i.e. N, P) by phytoplankton is proportional to the ratios among nutrient species in ambient waters. Based on the data of this study and previously publications, a preliminary estimate of nutrient budgets via riverine input and atmospheric deposition is established. The results indicate that atmospheric deposition gains importance over rivers in delivering nutrients into the Bohai and sustain the new production, following recent decrease in riverine inflow caused by drought periods in North China and damming practices. A historical review of nutrient data indicates that concentrations of nitrogen increase and phosphorus and silica decrease in the Central Bohai over last 40 years. This potentially has an important influence on the health of ecosystem in Bohai (e.g. food web and community structure), though further study is needed to examine the scenario in more detail.