Do Mining Activities Significantly Affect Feeding Behavior of Freshwater Benthic Macroinvertebrates? A Case Study in South Sardinia (Italy)

We investigated the cascading effects of chemical contaminants on alder leaf detritus quality and the exploitation of this feeding resource by benthic macroinvertebrates (isopods, gastropods, and mayfly nymphs). Trophic behavior and energetics of benthic macroinvertebrates were used to evaluate the effects of contaminants on detritus exploitation. A two-way factorial nested experimental design was used to statistically quantify how leaf detritus origin (polluted and unpolluted streams) and the pollution level of the site selected for microbial conditioning of the detritus could affect the feeding resource quality for aquatic benthic macroinvertebrates, as measured by their trophic behavior (i.e. food selection) and exploitation (i.e. food ingestion). Alder leaves collected from a polluted stream in a former mining area (South-Sardinia, Italy) had Cd, Pb, and Zn concentrations up to 10 times that of leaves collected from an unpolluted stream. When benthic macroinvertebrates were given the option to choose, they all selected leaves from the unpolluted stream and/or those conditioned in the unpolluted stream. Ingestion rates were also significantly affected by both considered factors: leaf origin and conditioning. In addition, synergistic effects strongly increased the chemical contaminant stress on the leaf detritus quality. These results show that the terrestrial component of land–water ecotones affected by mining can be a relevant indirect pathway of chemical stress to benthic macroinvertebrate species.     

Balancing–sequencing procedure for a mixed model assembly system in case of finite buffer capacity

In the last decades, the necessity to make production more versatile and flexible has forced assembly line production systems to change from fixed assembly lines to mixed model assembly lines, where the output products are variations of the same base product and only differ in specific customizable attributes. Such assembly lines allow reduced setup time, since products can be jointly manufactured in intermixed sequences (Boysen, Flieder, Scholl. Jena Research Papers in Business and Economics, Friedrich-Schiller-Universitat Jena, 1;1–11, 2007a; Boysen, Flieder, Scholl. Jena Research Papers in Business and Economics, Friedrich-Schiller-Universitat Jena, 2;1–33, 2007b). Unfortunately, the installation of customization options typically leads to variations in process times, and when the cycle is exceeded within a certain station, an overload is created, forcing other stations to wait and idle. Normally, process time variation in an un-paced line are absorbed by buffers, but in some industrial application the buffer dimensions are critical not only for the reduction of work in progress but also in reducing other constrains (space, technology, model dimensions, etc.). The problem of balancing mixed model assembly lines (MALBP), in the long term, and that of sequencing mixed model assembly lines (MMS), in the short term (Merengo, Nava, Pozetti. Int J Prod Res 37:2835–2860, 1999), are the two major problems to solve. The object of this paper is to illustrate an innovative balancing–sequencing step-by-step procedure that aims to optimize the assembly line performance and at the same time contain the buffer dimensions in function of different market demand and production mix. The model is validated using a simulation software and an industrial application is presented.     

Five year water and nitrogen balance for a constructed surface flow wetland treating agricultural drainage waters

The performance of a constructed surface flow wetland in reducing diffuse N pollution coming from croplands is being investigated in an ongoing experiment, begun in 1998 in NE Italy. The 0.32 ha wetland is vegetated with Phragmites australis (Cav.) Trin. and Typha latifolia (L.). It receives drainage water from 6 ha of land managed for an experiment on drainage systems, where maize, sugarbeet, winter wheat and soybean are cultivated. During the period 1998-2002, the wetland received from 4698 to 8412 mm of water per year (on average, about 9 times the environmental rainfall); its water regimen was discontinuous and flooding occurred on a variable number of days per year (from 13 to 126). Nitric nitrogen was the most important form of element load. Its concentration in the inflow water over time was rather discontinuous, with median values ranging from 0.2 (in 2001) to 4.5 (in 2000) mg L(-1). Inflow nitric N concentrations were occasionally in the 5-15 mg L(-1) range. Concentrations reduced passing through the wetland, with a more evident effect in the last year. Over 5 years, the wetland received slightly more than 2000 kg ha(-1) of nitrogen, 87% in nitric form mostly from farmland drainage. The remaining 13% of N was applied as organic slurry directly onto the wetland, with 5 distributions during 1998 to assess wetland performance in treating occasional organic loads. Field drainage loads had a discontinuous time pattern and occurred mostly during autumn-winter, with the exception of the 2001-2002 season which was a very dry. The wetland discharged 206 kg ha(-1) of N, over the 5-year period, with an apparent removal efficiency of about 90%. The disappearance was mostly due to plant uptake (1110 kg ha(-1)) and soil accumulation (570 kg ha(-1)), with the contribution of denitrification being estimated at around 7%.     

比例·韵律·形体——比萨奇迹广场建筑群与洗礼堂的构成分析

许多现代建筑的先驱者都曾特别关注比萨奇迹广场建筑群,由于它完美协调了各单体建筑之间,单体建筑与整体群组之间的比例关系,奇迹广场一直作为一个重要的实例被反复提及。在对这些思想进行简要回顾后,文章着重介绍了协调主教堂与洗礼堂建筑关系的模数系统,同时更进一步分析了洗礼堂建筑各个体块与构韵律之间微妙的组合关系。对洗礼堂建筑构成方法的分析,充分显示了建筑既符合西方中世纪建筑的和谱准则,又符合外表相似且带有复杂立面部件的建筑之间比例协调的原则。     

Performance of geosynthetic-reinforced flexible pavements in full-scale field trials

The paper presents the results of a series of full-scale trials carried out in Thailand examining the performance of geosynthetics as reinforcement for flexible pavements. The geosynthetics were embedded at different pavement depths and the structural response was monitored across four test sections by means of strain gauges, pressure sensors, deflection points and deflection plates. The results show that all reinforcement configurations helped reduce the vertical static stresses developed at the base of the pavement by up to 66% and by up to 72% for dynamic stresses. The performance enhancement expected to prolong the lifespan of the base layers. The reinforcement layers closer to the base experienced the highest lateral strains of up to 0.13%, providing evidence that geosynthetics can also effectively reduce lateral spreading. All reinforcement configurations helped enhance rut resistance with maximum traffic benefit ratio (TBR) of 13.70, effectiveness ratio (EF) of 12.70 and minimum rutting reduction ratio (RRR) of 0.74. The best configuration included a geotextile within the asphalt concrete layer and a geogrid under the base layer. Non-linear finite element analyses of the test sections predicted very well the strains and stresses in the pavement. The study provides a benchmark for future studies in this field and concludes that geosynthetics can help increase maintenance periods and extend the lifetime of flexible pavements.     

Shape-memory polymer networks from sol–gel cross-linked alkoxysilane-terminated poly(ε-caprolactone)

A novel type of covalently cross-linked semi-crystalline polymer with shape-memory and biocompatibility properties was prepared from alkoxysilane-terminated poly(ε-caprolactone) (PCL) by sol–gel process that allowed the generation of silica-like cross-linking points. A fine tuning of the cross-linking density and thermal properties (melting temperature) of the materials was obtained by controlling the molecular weight of the PCL precursor (and thus the molecular structure of the resulting network) and the curing conditions. The shape-memory behaviour was investigated with bending tests. Recovery times of less than one second were observed in water depending on the temperature, and a linear correlation of the recovery time with cross-linking density and molecular weight of PCL network precursor was observed.