Large eddy simulation of dispersion around an isolated cubic building: evaluation of localized dynamic k_\mathrm{SGS}-equation sub-grid scale model

In the present study, the prediction accuracy of a dynamic one-equation sub-grid scale model for the large eddy simulation of dispersion around an isolated cubic building is investigated. For this purpose, the localized dynamic $k_\mathrm{SGS} $ -equation model (LDKM) is employed and the results are compared with the available experimental data and two other classic sub-grid scale models, namely, standard Smagorinsky–Lilly model (SSLM) and dynamic Smagorinsky–Lilly model (DSLM). It is shown that the three SGS models give results in good agreement with experiment. However, near the ground level of the leeward wall, dimensionless time-averaged concentration, $\langle K\rangle $ , profile is not quite similar to the experimental data. It is also demonstrated that the LDKM predicts the values of $\langle K\rangle $ on the roof, leeward and side walls more acceptably than the SSLM and DSLM. Whereas, the streamwise elongation of time-averaged structures of the plume shape is more over-estimated with the LDKM than with the other two SGS models. In terms of numerical difficulty, the LDKM is found to be stable and computationally reasonable. In addition, it does not suffer from a flow dependent constant such as the Smagorinsky coefficient employed in the SSLM model.     

Prevalence of anaemia among children living in five communities in and near Karachi,Pakistan

The primary objectives of this research were to estimate the prevalence of anaemia and low haematocrit among preschool children living in Karachi. Through a geographically stratified design, 349 children aged 36–60 months were selected, from five communities in and near Karachi. Blood samples were drawn from children and a questionnaire was administered to evaluate various demographic and socioeconomic characteristics. Chi-square test and multiple logistic regression procedures were used to compare the prevalence of anaemia and low haematocrit among various strata. The overall prevalence of anaemia and low haematocrit were 55.9 and 48.4%, respectively. Children living in the rural community had the highest prevalence of anaemia (78.7%) and low haematocrit (63.8%). Children aged 36–48 months had also higher prevalence of anaemia and low haematocrit. Children's nutritional status was significantly associated with both anaemia and low haematocrit. We recommend appropriate interventions to reduce the burden of these conditions in Pakistan.     

Adsorption of methylene blue from aqueous solution by chemically treated water hyacinth

Water hyacinth (WH), an aquatic plant macrophyte, was investigated for its ability to perform as a suitable adsorbent for methylene blue (MB) from aqueous solution. The non-living biomass of WH was subjected to several chemical treatments, namely, washing with hot water, washing with hot dilute HCl, soaking in NaOH, soaking in HNO₃, and sulfonation. The system variables studied also include pH and MB concentration. The Langmuir isotherm was found to represent the measured adsorption data well except for WH soaked in NaOH, which was found to be better represented by the Freundlich isotherm. Values of the dimensionless separation factor, K _R, indicated that the adsorption systems in this study are all favorable. Values of the first layer of adsorption were calculated by the non-linear multilayer adsorption model, and the specific surface area values were found to be high and comparable to commercially activated carbons.     

Sonocatalytic degradation of tetracycline antibiotic in aqueous solution by sonocatalysis

Tetracycline (TC), one of the most common antibiotics, is often poorly bio-degraded in conventional wastewater treatment plants. In this study, the sonocatalytic degradation of TC was investigated using TiO₂ nano-particles as catalyst. The effect of pH, initial TC concentrations, reaction times, and H₂O₂ concentrations were evaluated. The efficacy of ultrasonic irradiation alone in the removal of this pollutant was negligible but removal efficiency increased upon addition of TiO₂ up to 250 mg L^?1; increase of pH and initial TC concentration attenuated TC degradation. Addition of H₂O₂ raised the removal efficiency so that complete removal of TC was achieved within 75 min.     

The Toxicology of Silica Nanoparticles: A Review

Silica nanoparticles are increasingly used in industrial, cosmetics, and medical applications. Workers in nanosilica production industries, laboratory personnel in drug production industries, patients taking drugs with nanosilica in its formulations, and everyone in society who uses cosmetics are potentially at risk to health effects induced by silica nanoparticles. Like other nanomaterials, nanosilica has unique physical and chemical properties that modify its toxic effects compared to bulk silica or microparticles of silica. Nanosilica toxicology has been studied by various in vitro and in vivo protocols and on humans, studies which are collected and summarized in the present publication. The toxic effects are outlined based on the type of body compartment, viz. cardiovascular, dermal, respiratory, neural, hepatic, genetic, immune, reproductive, and renal system. Further information, especially the experimental protocols and toxicological endpoints, are summarized in tables.     

Synthesis and antithyroid activity of 6‐n‐propyl‐5‐arylazo‐2‐thiouracils †

The synthesis of several 6‐n‐propyl‐5‐arylazo‐2‐thiouracil derivatives was achieved. The antithyroid activity of these derivatives has been determined using iodine‐125‐thiocyanate discharge technique in rats, and 6‐n‐propyl‐2‐thiouracil (PTU) as a standard. None of the 5‐arylazo‐2‐thiouracil analogs showed antithyroid activity as compared to PTU. The structure‐activity relationships (SAR) of position 5 in the PTU molecule and the requirements for better binding to the proposed receptor are discussed.     

Experimental degradation of oil in permeable sand from the Gulf of Aqaba,Red Sea

Degradation rates of light and heavy oil in permeable carbonate sands from the Gulf of Aqaba were investigated to evaluate the ability of sediments to degrade oil compounds. Silicate sands that are less permeable and different properties from carbonate sands were used for comparison. Estimates of oil degradation rates were based on oxygen consumption rates, calculated by incubating natural carbonate sands with oil. The degradation rates of light oil were twofold higher than those of heavy oil, which may be attributed to the presence of a higher carbon number in heavy oil compared with light oil. Degradation rates of light oil in carbonate sands were twofold higher than in silicate sands. Oil degradation rates calculated using the bottle incubation technique were three- to fourfold higher than rates from chamber incubations, indicating the importance of adequate mixing between oil particles and sediments during degradation processes. This study suggests that permeable sands, through their chemical and physical properties, increase oil biodegradation rates by enhancing flow through sediment particles and positively impacting bioturbation processes.     

Heavy metals in water, sediments, plants and fish of Kali Nadi U.P. (India)

The distribution of heavy metals viz., Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the water, sediments, plants and fish samples collected from the Kali Nadi (India) have been determined. The studies have shown that there was considerable variation in the concentration of heavy metals from one sampling station to the other which may be due to the variation in the quality of industrial and sewage wastes being added to the river at different places. The orders of the concentration of heavy metals in water, sediments, plants (Eicchornia crassipes) and fish (Heteropnuestes fossilis) were Fe > Zn > Cu > Mn > Cr > Ni > Pb > Co > Cd; Fe > Zn > Mn > Ni > Cr > Co > Cu > Pb > Cd; Fe > Mn > Zn > Cu > Ni > Co > Pb > Cr > Cd and Fe > Zn > Mn > Ni > Pb > Co > Cr > Cu > Cd, respectively.     

Future production of rainfed wheat in Iran (Khorasan province): climate change scenario analysis

Projecting staple crop production including wheat under future climate plays a fundamental role in planning the required adaptation and mitigation strategies for climate change effects especially in developing countries. The main aim of this study was to investigate the direction and magnitude of climate change impacts on grain yield of rainfed wheat (Triticum aestivum L.) production and precipitation within growing season. This study was performed for various regions in Khorasan province which is located in northeast of Iran. Climate projections of two General Circulation Models (GCM) for four locations under three climate change scenarios were employed in this study for different future time periods. A stochastic weather generator (LARS-WG5) was used for downscaling to generate daily climate parameters from GCMs output. The Decision Support System for Agrotechnology Transfer (DSSAT) Version 4.5 was employed to evaluate rainfed wheat performance under future climate. Grain yield of rainfed wheat and precipitation during growth period considerably decreased under different scenarios in various time periods in contrast to baseline. Highest grain yield and precipitation during growth period was obtained under B1 scenario but A1B and A2 scenarios resulted in sharp decrease (by ?57 %) of grain yield. Climate change did not have marked effects on evapotranspiration during the rainfed wheat growth. A significant correlation was detected between grain yield, precipitation and evapotranspiration under climate change for both GCMs and under all study scenarios. It was concluded, that rainfed wheat production may decline during the next 80 years especially under A2 scenario. Therefore, planning the comprehensive adaptation and mitigation program is necessary for avoiding climate change negative impact on rainfed wheat production.