Seasonal abundance of non-commercial demersal fish in the eastern Mediterranean Sea in relation to hydrographic and sediment characteristics

Fish-habitat associations were investigated for twenty-five non-commercial demersal species in the Aegean Sea (eastern Mediterranean) using Generalized Additive Modeling techniques. Fishery related abundance indices, derived from experimental bottom trawl surveys, were linked to various habitat variables: substrate characteristics, area, season, depth, temperature and salinity. Depth was the most important factor for all species. Eleven species showed decreasing abundance with depth, while the remaining species were more abundant in specific depth zones either on the continental shelf or in the upper continental slope. Most species were associated with specific substratum characteristics such as the dry weight percentage of sand-gravel and the carbonate content. The dry weight percentage of sand-gravel in the sediments was selected as a predictor of the relative abundance of most (twenty three) species. Seasonal patterns in the relative abundance of species were observed, related in most cases to the seasonal differentiation of temperature. The effect of temperature was more pronounced in summer and autumn, when a marked thermocline is observed, while it was much less intense in winter. For most of the species, the preferable habitat was identified, that contributes valuable information for the successful implementation of an ecosystem approach to fisheries management.     

Spatial patterns of biodiversity in the Black Sea: An assessment using benthic polychaetes

The current study broadens the biodiversity information available for the Black Sea and neighbouring regions and improves our knowledge about the polychaete biogeographic patterns to be discerned in them. There appears to be a well-defined zoogeocline from the Marmara Sea and Bosphorus Strait to the inner parts of the region (Azov Sea), depicted both as a multivariate pattern and in terms of species (or taxa) numbers. The emergent multivariate pattern complies, to a certain extent, with Jakubova’s (1935) views: three main sectors can be defined in the basin: (a) Prebosphoric, (b) the Black Sea and, (c) the Azov Sea, whereas the Bosphorus Strait and Marmara Sea show less faunal affinities with the afore-mentioned sectors. Patterns derived both from the cosmopolitan and Atlanto-Mediterranean species closely follow the one coming from the polychaete species and genera inventories. As a general trend, species numbers decrease along with the decrease in salinity towards the inner parts of the region. The trend is homologous to that seen in the benthic invertebrate inventories of all the major European semi-enclosed regional seas. Salinity and food availability appear to be the dominant abiotic factors correlated, though weakly, with the various patterns deriving from the taxonomic/zoogeographic categories. With the exception of the Anatolia, polychaete inventories from all sectors appear to be random samples of the total inventory of the region, in terms of taxonomic distinctness values. Therefore, these sectoral inventories can be used for future biodiversity/environmental impact assessment studies. A massive invasion of Mediterranean species after the opening of the Black Sea, in the lower Quaternary period, appears to be the likely biogeographic mechanism through which the old Sarmatic fauna was almost completely replaced by species of marine origin.     

中国鲤科鱼类游泳能力综合分析和应用

该研究利用学术论文数据库筛选出中国鲤科鱼类游泳能力相关论文115篇,并用Origin软件进行了数据统计分析,旨在归纳和分析中国鲤科鱼类游泳能力并建立估算方法,可为正处于规划阶段和可行性研究阶段的过鱼设施流速设计提供依据.结果表明：(1)鱼类游泳速度与鱼体长度具有显著的非线性相关关系,据此建立了一系列幂函数经验公式,可为游泳能力和过鱼设施研究及设计提供依据.(2)依据所得到的经验公式和协方差分析可知,喜流水型鲤科鱼类的游泳能力>广适型>喜静水型.根据该研究得到的经验公式并结合行业规范和文献资料,对正处于规划阶段和可行性研究阶段过鱼设施流速设计的建议如下：西南地区以裂腹鱼成鱼为主要过鱼对象的过鱼设施进鱼口吸引流速范围为0.61～0.76m/s,通道内最高流速阈值为1.28 m/s;长江中下游以四大家鱼成鱼为主要过鱼对象的进鱼口吸引流速范围为0.76～0.93m/s,通道内最高流速阈值为1.49 m/s,以四大家鱼幼鱼为主要过鱼对象的进鱼口吸引流速范围为0.42～0.62 m/s,通道内最高流速阈值可为0.82 m/s.     

A comparative mineralogical study of Te-rich magmatic-hydrothermal systems in northeastern Greece

Summary Several magmatic-hydrothermal systems in northeastern Greece (western Thrace and Limnos Island) are highly enriched in tellurides which, in addition to native gold and electrum, represent major carriers of precious metals in the ore. Deposition near the porphyry-epithermal transition for several systems is indicated by field relations and by the presence of key minerals (Pb- and Ag-rich tellurides, Bi-sulfosalts and Bi-tellurides/tellurosulfides). Hessite, stützite, sylvanite, petzite, coloradoite, altaite, unnamed Ag-sulfotelluride, native tellurium and electrum are abundant in intermediate sulfidation quartz-carbonate veins together with zincian tetrahedrite-group minerals, chalcopyrite and galena. The presence of hessite, goldfieldite, native gold and enargite or famatinite suggests deposition at a high sulfidation state. The main stage of telluride deposition took place at ∼275 °C at log fTe₂ values of −8.5 to −7.1 and log fS₂ values of −10.8 to −9.0, based on the Fe-content in sphalerite and the sulfide-telluride mineralogy. The close spatial association of telluride mineralization with intrusive centers of intermediate composition, the base metal enrichment and the trace element signature involving Au, Ag, Te, Bi, Sn and Mo suggest that ore-forming components were introduced at the porphyry-epithermal transition. Potential sources of tellurium are the high-K calc-alkaline (western Thrace) to shoshonitic (Limnos) intrusive rocks.     

Optimum seismic design of reinforced concrete frames according to Eurocode 8 and fib Model Code 2010

Traditional seismic design, like the one adopted in Eurocode 8 (EC8), is force‐based and examining a single level of seismic action. In order to provide improved control of structural damage for different levels of seismic action, the new fib Model Code 2010 (MC2010) includes a fully fledged displacement‐based and performance‐based seismic design methodology. However, the level of complexity and computational effort of the MC2010 methodology is significantly increased. Hence, the use of automated optimization techniques for obtaining cost‐effective design solutions becomes appealing if not necessary. This study employs genetic algorithms to derive and compare optimum seismic design solutions of reinforced concrete frames according to EC8 and MC2010. This is important because MC2010 is meant to serve as a basis for future seismic design codes. It is found that MC2010 drives to more cost‐effective solutions than EC8 for regions of low seismicity and better or similar costs for regions of moderate seismicity. For high‐seismicity regions, MC2010 may yield similar or increased structural costs. This depends strongly on the provisions adopted for selecting the set of ground motions. In all cases, MC2010 provides enhanced control of structural damage. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrical resistivity tomography mapping of beachrocks: application to the island of Thassos (N. Greece)

Electrical resistivity tomography (ERT) technique is widely used in mapping subsurface electrical properties. In this study, ERT was used to map a beachrock outcrop, extended both inland, under beach sediments, and seawards, on and under seafloor sediments. Mapping of beachrock is considered important because it can help evaluate the lateral and vertical extend of the formation. Fast and reliable mapping of beachrocks may contribute in several applications like engineering and construction, coastal management, recreational reformation as well as scientific approaches like coastal evolution research, and palaeo-environmental studies. The outcome of the survey was the mapping of the formation with centimeter precision, especially towards the sea. Special processing was applied to the data in order to constrain the inversion procedure to include the known sea water layer.     

A Timoshenko finite element straight beam with internal degrees of freedom

We present hereafter the formulation of a Timoshenko finite element straight beam with internal degrees of freedom, suitable for nonlinear material problems in geomechanics (e.g., beam type structures and deep pile foundations). Cubic shape functions are used for the transverse displacements and quadratic for the rotations. The element is free of shear locking, and we prove that one element is able to predict the exact tip displacements for any complex distributed loadings and any suitable boundary conditions. After the presentation of the virtual power and the weak form formulations, the construction of the elementary stiffness matrix is detailed. The analytical results of the static condensation method are provided. It is also proven that the element introduced by Friedman and Kosmatka in 1 , with shape functions depending on material properties, is derived from the new beam element. Validation is provided using linear and material nonlinear applications (reinforced concrete column under cyclic loading) in the context of a multifiber beam formulation. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of the SAR TT-OSL procedure for dating Middle Pleistocene dune and shallow marine deposits along the southern Cape coast of South Africa

Optically stimulated luminescence (OSL) dating is now commonly used to estimate the depositional age of Quaternary landforms along the southern Cape coast of South Africa. Due to the early onset of dose saturation in the quartz-rich sediments from this region, determining the age of deposits much older than the last three glacio-eustatic sea-level high stands has been a challenge. In this study, we explored the feasibility of using the thermally-transferred OSL (TT-OSL) dating method to obtain ages for aeolian and shallow marine deposits at three different localities that hold promise to further illuminate the long and complex Late Quaternary sea-level history of this region. The bleachability and behaviour of both the recuperated OSL (ReOSL) and the basic-transferred OSL (BT-OSL) signals were investigated, and used as independent chronometers to infer (a) the degree of bleaching of the sediments and (b) the stability of the ReOSL signal for dating of older samples. We examined the sensitivity of both signals to varying preheat temperatures and further developed the single-aliquot regenerative-dose procedure for TT-OSL dating of our samples. To verify our procedures, and to understand some of the underlying mechanisms responsible for the problems we observed, modern analogues and known-age Marine Isotope Sub-stage (MIS) 5e samples from the same localities were also measured. The Middle Pleistocene deposits investigated in this study produced statistically consistent ReOSL and BT-OSL ages compatible with sea-level high stands during Marine Isotope Stage 11. This result is of considerable significance, as it may yield new insights into maximum sea-level heights during this period, which is widely considered an appropriate analogue for future environmental conditions.     

Time-harmonic boussinesq problem for a continuously non-homogeneous soil

An analytical solution is presented for the response of a non-homogeneous, compressible, elastic half-space to a time-harmonic vertical point load on its surface. The shear modulus is assumed to increase continuously with depth. The model is chosen so as to describe uniformly deposited cohesionless soils. Expressions for displacements and stresses in the interior of the half-space medium are derived by means of Hankel transforms and contour integration. Selected numerical results are presented to demonstrate the influence of non-homogeneity. Finally, some effects are pointed out to be used in connection with vibration tests for subsoil investigation.