Influence of the corrosion products of copper on its atmospheric corrosion kinetics in tropical climate

In the present paper, the identification of the corrosion product phases formed on copper under different atmospheres of Cuban tropical climate is reported. Cuprite (Cu₂O), paratacamite (Cu₂Cl(OH)₃), posnjakite (Cu₄SO₄(OH)₆ · 2H₂O) and brochantite (Cu₄SO₄(OH)₆) were the main phases identified by X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FTIR).Copper corrosion products are known to have a protective effect against corrosion. However, a different behaviour was obtained under sheltered coastal conditions. This can be due to the corrosion products morphology and degree of crystallisation, rather than their phase composition. A higher time of wetness and the accumulation of pollutants not washed away from the metal surface can also play an important role.     

On the regional incidence of highway investments in the USA

The objective of this paper was to investigate the regional incidence of the aggregate effects of investment in highways in the US taking into consideration the presence of regional spillovers. The empirical results are based on VAR estimates at both the aggregate and state levels using output, employment, and investment, as well as different measures of highway investments. Empirical results allow us to establish several stylized facts. First, investment in highways affects private sector variables positively at the aggregate level as well as in most states. Second, the regional spillover effects are very significant for all private sector variables. Third, these spillovers have a clear geographical pattern in that they tend to be more important in western states and the corridor between the Great Lakes and the Gulf Coast.     

Large-scale load capacity tests on a geosynthetic encased column

Stone columns have been used to minimize the settlement of embankments on soft soils but their use in very soft soils can become challenging, partly because of the low confinement provided by the surrounding soil. Geosynthetic encased columns (GECs) have been successfully used to enhance to reduce settlements of embankments on soft soils. This paper describes an investigation on the performance of encased columns constructed on a very soft soil using different types of encasement (three woven geotextiles with different values of tensile stiffness) and different column fill materials (sand, gravel and recycled construction and demolition waste, RCDW). The results of load capacity tests conducted on large-scale models constructed to simulate the different types of GECs indicate that the displacement method adopted during column installation can lead to an enhanced shear strength in the smear zone that develops within the very soft soil. In addition, breakage of the column fill material was found to affect the load-settlement response of gravel and RCDW columns. Furthermore, the excess pore water pressure generated in the surrounding soil during installation, was found to remain limited to radial distances smaller than three times the GEC diameter.     

Quo vadis source tracking? Towards a strategic framework for environmental monitoring of fecal pollution

Advances in microbial source tracking (MST) have largely been driven by the need to comply with water quality standards based on traditional indicator bacteria. Recently, a number of culture-independent, and library-independent methods based on polymerase chain reaction (PCR) have been gaining popularity among source trackers. However, only a limited number of these methods have been successfully used in field applications, primarily due to the fact that many of them are still being developed. In this critical outlook, we examine different viewpoints associated with the practical use of MST to identify critical research gaps, propose a priority-based timeline to address them, and outline emerging technologies that will likely impact the future of source tracking. We propose that it is necessary to consider each of these aspects in order to advance towards a unifying framework in source identification, so that fecal pollution monitoring can be reliably used for comprehensive environmental microbial monitoring, to develop risk assessment models, and to implement and validate adequate management practices.     

试验室研究一种新型透水性混凝土路面砖的块型设计过程

本文介绍一种专门为城市透水性路面而设计的混凝土路面砖的块型.Cantabria大学与当地一家生产企业合作,并得到地方政府的支持,其目的是在西班牙北部应用透水型路面砖作为城市可持续性排水系统.在提出多个不同外形和尺寸的块型设计方案后,根据路面开孔率、砖连锁咬合接触面和美学角度,先从理论上进行初步对比,选择一种块型--有四种不同形状的透水槽沟:然后在Cantabia大学公路试验室里进行测试,检测不同形状的开孔对路面透水性能的影响.共进行两组测试,第一组假设路面开孔存在不同堵塞状况和坡度,以确定最佳的开孔形状;第二组用选定的混凝土路面砖,分析透水性路面的水径流.根据初步试验结果,生产企业订制模型、生产了第一批新型混凝土路面砖,并已着手推向市场.新型透水性混凝土路面砖的设计研究过程经历了无数次成功和失败,本文仅为丰富技术探讨内容,无意使其成为技术导则.     

Trihalomethanes in the drinking water of Concepción and Talcahuano,Chile

Formation of trihalomethanes (THMs) during water disinfection has been related to several health problems, although the magnitude of these effects is under discussion. This paper quantifies the THMs in drinking water from the Bío‐Bío Region of central Chile, the first since the modification of the national reference value (Nch 409/05) to include maximal values for THMs. THMs were quantified using a solid phase micro‐extraction (SPME) method and GC‐MS. The concentration ranges were 9.7–111.6, 0.1–1.0 and 0.9–25.5 μg/L for chloroform (CHCl₃), and dibromochloromethane (CHClBr₂) and bromodichloromethane (CHCl₂Br), respectively. Bromoform was not detected in any sample. There were good correlations (R²=0.91–0.98, P<0.001) between the THMs and the residence time of the water, the distance from the treatment plant and an inverse correlation to free chlorine in the water. The Additive Toxicity Index Value (0.07–1.00) showed that all samples were within the Chilean reference value for THMs in drinking water. However, several values were close to exceeding the maximum permitted concentration (200, 100, 100 and 60 μg/L for CHCl₃, CHBr₃, CHClBr₂ and CHCl₂Br, respectively), which may occur when the water demand is low and thus residence times are longer.     

Measurement of phenols dearomatization via electrolysis: The UV-Vis solid phase extraction method

Dearomatization levels during electrochemical oxidation of p-methoxyphenol (PMP) and p-nitrophenol (PNP) have been determined through UV-Vis spectroscopy using solid phase extraction (UV-Vis/SPE). The results show that the method is satisfactory to determine the ratio between aromatic compounds and aliphatic acids and reaction kinetics parameters during treatment of wastewater, in agreement with results obtained from numerical deconvolution of UV-Vis spectra. Analysis of solutions obtained from electrolysis of substituted phenols on antimony-doped tin oxide (SnO₂Sb) showed that an electron acceptor substituting group favored the aromatic ring opening reaction, preventing formation of intermediate quinone during oxidation.     

Influence of added concrete compressive strength on adhesion to an existing concrete substrate

An experimental study was performed to evaluate the bond strength between two concrete layers of different ages, considering different mixtures of added concrete, with different strengths. The specimens first had the roughness of the substrate surface increased by sand blasting. Later, the new concrete was added. Afterwards, slant shear tests were performed to quantify the bond strength in shear. These tests indicated that increasing the compressive strength of the added concrete relative to the compressive strength of the substrate concrete improves the bond strength and changes the rupture mode from adhesive to monolithic. A finite element analysis showed that, increasing the difference between the compressive strengths of the added concrete and the substrate concrete, higher values of normal stress are present in the interface, for the same level of shear stress. The study presented in this paper reveals that the added concrete, normally with higher compressive strength than the substrate concrete, may possibly have an influence on concrete-to-concrete bond strength. Therefore, design of shear at the interface between concrete cast at different ages, according to Eurocode 2, could be improved, since here only the lowest strength concrete is considered.     

Public investment in transportation infrastructures and regional asymmetries in Portugal

The objective of this paper is to investigate the regional incidence of the effects of public investment in transportation infrastructures in Portugal. Our methodological approach consists of estimating vector autoregressive (VAR) models for the national economy as well as for each of the five administrative regions in the country. In the regional models, both public investment in transportation infrastructures in the region and public investment in transportation infrastructures elsewhere are considered, thereby taking into consideration the potential existence of regional spillovers. Empirical results suggest that although public investment in transportation infrastructures has been a powerful instrument to promote long-term growth, it does so in a way that is rather unbalanced across regions. We show that public investment in transportation infrastructures has markedly contributed to the concentration of economic activity in Lisbon, the largest region in the country, and therefore has contributed markedly to the macrocephaly of the country.

Identification of chicken-specific fecal microbial sequences using a metagenomic approach

In this study, we applied a genome fragment enrichment (GFE) method to select for genomic regions that differ among different fecal metagenomes. Competitive DNA hybridizations were performed between chicken fecal DNA and pig fecal DNA (CP) and between chicken fecal DNA and an avian DNA composite consisting of turkey, goose, and seagull fecal DNA extracts (CB) to enrich for chicken-specific DNA fragments. A total of 471 non-redundant chicken metagenomic sequences were retrieved and analyzed. All of the clone sequences were similar to prokaryotic genes, of which more than 60% could not be assigned to previously characterized functional roles. In general terms, sequences assigned characterized functional roles were associated with cellular processes (11.7%), metabolism (11.0%) and information storage and processing (13.4%). Approximately 53% of the non-redundant sequences are similar to genes present in intestinal bacteria belonging to Clostridia (20.9%), Bacteroidetes (15.0%), and Bacilli (17.3%). Twenty-five sequences from the CP and CB clone libraries were selected to develop chicken fecal-specific PCR assays. These assays were challenged against fecal DNA extracted from 21 different animal species, including mammals and birds. The results from the host-specificity studies showed that 12 of the assays had a high degree of specificity to chicken feces. In addition, three assays were specific to chicken and turkey while another four assays tested positive to more than two avian species, suggesting a broader distribution of some of the enriched gene fragments among different avian fecal microbial communities. Fecal pollution signals were detected using chicken-specific assays in contaminated water samples, although the PCR assays showed different detection limits. These results indicate the need for multiple assays to detect poultry fecal sources of pollution. The competitive DNA hybridization approach used in this study can rapidly select for numerous chicken fecal metagenomic regions that can be used as potential genetic markers for fecal source tracking.