Modelling and simulation of a gas–solids dispersion flow in a high-flux circulating fluidized bed (HFCFB) riser

Radial solids velocity profiles were computed on seven axial levels in the riser of a high-flux circulating fluidized bed (HFCFB) using a two-phase 3-D computational fluid dynamics model. The computed solids velocities were compared with experimental data on a riser with an internal diameter of 76 mm and a height of 10 m, at a high solids flux of 300 kg m⁻² s⁻¹ and a superficial velocity of 8 m s⁻¹. Several hundreds of experimental and numerical studies on CFBs have been carried out at low fluxes of less than 200 kg m⁻² s⁻¹, whereas only a few limited useful studies have dealt with high solids flux. The k– two-phase turbulence model was used to describe the gas–solids flow in an HFCFB. The model predicts a core–annulus flow in the dilute and developed flow regions similar to that found experimentally, but in the region of highest solids concentration it is somewhat overpredicted at the level close to the inlet.     

Diversity and antifungal susceptibility of yeasts from tropical freshwater environments in Southeastern Brazil

Yeast communities were isolated from water and sediment samples of two unpolluted natural lakes, located inside Rio Doce State Park, and two rivers located outside of this Park in Southeastern Brazil. A total of 134 yeast isolates were obtained and identified as belonging to 36 species. The numbers of fecal coliforms and yeast species were higher in rivers than in lakes. The genus Candida had the highest number of species with the presence of opportunistic pathogens such as Candida krusei, C. tropicalis, C. guilliermondii and C. parapsilosis. Yeasts able to grow at 37 degrees C were tested in relation to their susceptibility to common used antifungal drugs. Yeast isolates (13%) were susceptible to ketoconazole, 79% to fluconazole, 31% to terbinafine and 78% of the strains were susceptible to amphotericin B. Seven isolates from different Candida species were resistant to all antifungals tested. The high number of fecal coliforms found in these aquatic environments and the presence of resistant yeast strains to common used antifungal drugs suggest that these environments can pose potential health risks for people utilizing the contaminated waters.     

Prenatal exposure to mercury in a prospective mother-infant cohort study in a Mediterranean area, Valencia, Spain

BACKGROUND: Mercury (Hg) is a ubiquitous pollutant that negatively affects fetal and child neurodevelopment at accidental high-dose exposure. Some studies indicate that Mediterranean populations could be at risk of prenatal exposure to mercury through fish consumption. OBJECTIVES: To assess the prenatal exposure to total mercury (T-Hg), both inorganic and organic, in newborns by analyzing the T-Hg concentration in cord blood, and to evaluate the role of maternal fish consumption in this exposure. METHODS: In the context of a multi-center project (INMA project), a prospective birth cohort was set up in Valencia, Spain, from 2005 to 2006. A total of 253 newborns were included in this study. We compared cord blood T-Hg concentration by levels of fish intake assessed by a food frequency questionnaire completed at 28-32 weeks of gestation. Maternal covariates were obtained through a questionnaire. RESULTS: The geometric mean of T-Hg at birth was 9.9 microg/L (95% CI: 9.0, 10.8). Seventy five percent of cord blood samples were above the estimated level assumed to be without appreciable harm (5.8 microg/L). Women who consumed a portion of large oily fish, lean fish, or mixed fried fish two or more times per week had mean cord blood levels 1.6, 1.4 and 1.3 times higher, respectively, than those who rarely or never consumed fish. Other factors such as the mother's age, country of origin, smoking and season of delivery were also significantly and independently associated with cord blood T-Hg concentrations. CONCLUSIONS: Newborns from a Mediterranean area presented elevated levels of T-Hg in cord blood. Higher concentrations of T-Hg were related to maternal fish intake, particularly in the case of large oily fish species.     

Mytilus galloprovincialis filter feeding on the bacterial community in a Mediterranean coastal area (Northern Ionian Sea, Italy)

This study was carried out seasonally, throughout a year, to evaluate the filtering activity on bacteria of Mytilus galloprovincialis. Six microbiological parameters were researched in the water and mussels samples collected along the coastal area of the Northern Ionian Sea in three stations, S. Vito, Lido Gandoli and Lido Silvana. We detected the densities of culturable heterotrophic bacteria by spread plate on Marine Agar, total culturable bacteria at 37 degrees C on Plate Count Agar and vibrios abundance on thiosulphate-citrate-bile-sucrose-salt (TCBS) agar. Total and fecal coliforms as well as fecal streptococci were determined by the Most Probable Number. Bacterial concentrations at 20 and 37 degrees C as well as vibrios concentrations were higher in the mussel samples compared to the corresponding seawater throughout the year. The results obtained could contribute to improve the information relatively either to the natural processes existing between bacteria and mussels or to the risk of human infections related to the consumption of mussels.     

Silsesquioxane functionalized with methacrylate and amine groups as a crosslinker/co-initiator for the synthesis of hydrogels by visible-light photopolymerization

A silsesquioxane bearing methacrylate and amine groups was synthesized by reacting half of the NH groups of N-[3-(trimethoxysilyl)-propyl]ethylene diamine with glycidyl methacrylate, followed by the hydrolytic condensation of methoxysilane groups. This led to a water-soluble silsesquioxane functionalized with methacrylate and amine groups (SFMA) that was characterized by UV-MALDI TOF MS. A formulation containing safranine-O as sensitizer and SFMA as co-initiator (electron donor)/crosslinker was used for the visible-light photopolymerization of water solutions of 2-hydroxyethylmethacrylate (HEMA) and acrylamide (AAm). Without SFMA addition no reaction was observed while in the presence of 0.8 wt% SFMA with respect to monomers, crosslinked polymers (hydrogels) were obtained. Swelling of the resulting hydrogels in a broad pH range was investigated.     

UV-photopolymerisation of poly(methyl methacrylate)-based inorganic-organic hybrid coatings and bulk samples reinforced with methacrylate-modified zirconium oxocluster

In this work, we developed and optimised a synthetic route which enables to produce by spray-coating hard, transparent and stable inorganic-organic hybrid coatings for a wide variety of different substrates (e.g. stone, stainless steel, polymethylmethacrylate, polyethylene, wood, anodized aluminum). Chemically and thermally stable acrylate-based hybrid materials embedding the zirconium oxocluster Zr₄O₂(OMc)₁₂, OMc(CH₂C(CH₃)C(O)O) were prepared and UV-cured.The coatings of different compositions on different substrates were characterized by numerous analytical and spectroscopic methods such as FT-IR spectroscopy, Angle Resolved-XPS (AR-XPS), Secondary Ion Mass Spectrometry (SIMS), X-ray Absorption Spectroscopy (XAS), Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-ray analysis (EDX). Bulk samples were also prepared for additional characterizations. The bulk samples were analysed by FT-IR, whereas the cross-linking degree was qualitatively evaluated by swelling experiments. As far as the mechanical properties are concerned, the shear storage modulus (G′) and loss modulus (G″) were measured by Dynamical Mechanical Thermal Analysis (DMTA) technique. Moreover, the best conditions for the curing and cross-linking processes of the hybrid materials were studied up to 200 °C by using Differential Scanning Calorimetry (DSC). The thermal stability of the hybrid samples was evaluated by Thermogravimetric Analysis (TGA).     

Influence of Past Mining on the Quality of Surface Waters at Funtana Raminosa (Sardinia)

Cu–Pb deposits at Funtana Raminosa in Central Sardinia were intensively exploited, mostly underground, from 1917 until 1983. Flotation tailings were dumped near the mine plant. A hydrogeochemical survey carried out in 2004 showed that mine drainage collected from several galleries was circumneutral, due to the availability of carbonate minerals that buffer the acidity produced by the oxidation of Fe-bearing sulphides. The mine waters contained higher concentrations of dissolved SO₄, F, Zn, Cd, Pb, Mn, and Mo than was observed in uncontaminated spring and stream waters in the area. Drainage from the oldest flotation tailings showed much lower concentrations of Zn, Cd, and Pb than those generally observed in mine waters. In contrast, drainage from the recent flotation tailings had the highest levels of dissolved SO₄, Zn, and Cd (1,600, 30, and 0.8 mg/L, respectively) when sampled in the dry season; these were two orders of magnitude lower in the rainy season under high flow condition. Pb was ≈ 5 μg/L under different flow conditions. Water in the Rio Saraxinus, a stream that drains the entire mining area, had a relatively low level of contamination (170 μg/L Zn, 7 μg/L Cd, and 0.9 μg/L Pb).     

Rebound at Pb-Zn Mines Hosted in Carbonate Aquifers: Influence on the Chemistry of Ground Water

Abstract  Closure of Pb-Zn mines in the Iglesiente district (SW Sardinia, Italy) caused the cessation of pumping in 1997 at Monteponi, and in 1998 at San Giovanni. Consequent flooding of underground workings occurred in the district and also involved Campo Pisano. In June 1998, as the water table rose from 160 to 20 m below sea level, the deep saline water mixed with the shallow ground water at Monteponi and nearby mines. In the same period, an increase in dissolved metals (especially Zn, Cd, and Pb) was observed under near-neutral pH conditions. Following peak concentrations, a marked decrease of Zn, Cd, and Hg occurred. Dissolved Pb showed fluctuating concentrations over the monitoring period (1996-2005). In January 2000, when the water table rose to 20 m above sea level, the salinity of ground water decreased significantly at all of the mines. Stratification caused the more saline water at depth to settle three years after rebound started. Depth profiles carried out in 2005 at Monteponi, San Giovanni, and Campo Pisano showed an increase in conductivity and dissolved metals in ground water at deeper levels, especially at depths below sea level.After eight years of rebound, a marine component was still present at depth in ground water at San Giovanni (about 2%), and to a lesser extent at Monteponi (about 0.4%).     

一个由LabVIEW编写的扫描探针显微镜控制程序

本文的主要目的是通过具体示例的详细讲解,来降低自制扫描探针显微镜的门槛.本文用简约易懂的 LabVIEW编程实现了复杂的扫描探针显微镜的控制与图像处理的功能.本控制程序由三大模块用顺序结构完成.它们分别是设备初始化模块、扫描控制与显像模块和设备安全关机模块.控制程序中最复杂、最关键的扫描控制与显像模块采用完全并行处理的方式实现.这种模块化设计,使主控程序简单明了;既方便修改又方便维护.并行处理模块主要有扫描区域调整与像素调整模块、Y方向扫描控制模块、X方向扫描控制与图像传输模块、扫描过程中参数再调整模块、扫描中断与紧急停机模块等组成.FPGA模块的主要功能是完成控制信号的输出与Z方向的实时反馈控制,在主控程序发出紧急停机命令时,FPGA 模块将消除系统可能的振荡,把扫描探针恢复到初始位置以及关闭高压控制信号等等.文章最后,介绍了如何使用该控制器.杂乱无章、横七竖八的连线是 LabVIEW编程中的最大的诟病.当程序复杂时,这一问题更加严重.本文向读者展示了用 LabVIEW实现完全结构化与并行编程的方法;读者可以按照本文描述的编程技巧,用简单、易懂、易维护的模块化程序实现复杂的虚拟仪器应用.     

Advanced homogeneous-heterogeneous immunosensing format employing restricted access supports

A rapid immunosensing methodology that employs the so-called homogeneous-heterogeneous assay mode is presented. The immunosensor is based on the homogeneous competition among the analyte, a fluorescent tracer, and the antibody, followed by separation of free and bound species by means of a restricted access alkyl-diol silica C18 reversed-phase chromatographic support. In order to develop a general labeling methodology, fluorescent tracers are synthesized from oligonucleotides covalently bound to the hapten in 3' position and the marker in 5'. The immunosensor principle is demonstrated by determining atrazine in a completely automated manner at 2 min/sample without regeneration of the support and a limit of detection of 1.0 microg/L with the optimized system. Preliminary assays employing multilabeled tracers indicate that sensitivity can be improved. Organic solvents 2-propanol and acetonitrile up to 15% (v/v) are well tolerated, while methanol can be added to 50%. The sensor capabilities are demonstrated through the analysis of natural waters.