Distribution pattern of eight heavy metals in the outer and inner tissues of ten commonly used vegetables

This study reports the distribution of eight heavy metals (Cd, Co, Cr, Cu, Hg, Mn, Ni, and Pb) in the outer and inner tissues of ten different vegetables from the Qassim region of Saudi Arabia. The oven-dried (65°C, 48 h) vegetable samples were subjected to microwave acid digestion before heavy metals analysis using inductively coupled plasma optical emission spectrometry. The results showed that Co, Cd, and Pb were absent in the outer tissues of all the vegetables, whereas these elements were detected in the inner tissues of some vegetables in the ranges of 0.01–0.23 mg/kg wet weight, 0.03–0.42 mg/kg, and 0.02–3.44 mg/kg, respectively. The traces of Hg (1.83–3.59 μg/kg) were noticed in the outer tissues of all the samples; however, it was not detected in the inner tissues of vegetables. The variable distribution of heavy metals in different vegetables is influenced by several factors, including exposure route, physicochemical properties of heavy metals, species of crops, cultivation strategy, soil type, and growing conditions. In conclusion, although the representative samples of vegetables used in this study contained safe levels of Cd, Co, Ni, and Pb, higher than recommended upper limits of Cr, Cu, and Mn were observed in some vegetables. These findings suggested that regular monitoring of heavy metals in vegetables is important to safeguard consumers.     

Characterization of the Evolution and Properties of Silicon Carbide Derived From a Preceramic Polymer Precursor

This study reports on the fabrication and characterization of polymer‐derived amorphous and nano‐grained SiC, by controlled pyrolysis of allylhydridopolycarbosilane (AHPCS) under inert atmosphere. Processing temperatures and hold times at final temperatures are varied to study the influence of processing parameters on the structure and resulting properties. Chemical changes, phase transformations, and microstructural changes occurring during the pyrolysis process are studied. Polymer cross‐linking and polymer to ceramic conversion is studied using infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are performed to monitor the mass loss and phase change as a function of temperature. X‐ray diffraction studies are performed to study the intermediate phases and microstructural changes. Hardness and modulus measurements are carried out using instrumented nanoindentation to establish processing‐property‐structure relationship for SiC derived from the polymer precursor. It is seen that the presence of nanocrystalline domains in amorphous SiC significantly influences the modulus and hardness. A nonlinear relationship is observed in these properties with optimal mechanical properties observed for SiC processed to 1150°C for 1 h hold duration, having average grain size of 3 nm. In addition, bulk mechanical characterization, in terms of biaxial flexure strength, is done for SiC–SiC particulate composites purely derived from the polymer precursor.     

MRT Letter: High resolution SEM imaging of nano‐architecture of cured urea‐formaldehyde resin using plasma coating of osmium

Nanoarchitecture of cured urea‐formaldehyde (UF) resins was examined with a field‐emission scanning electron microscope (FE‐SEM) after coating samples with osmium, which is considered to produce particles of considerably smaller size compared to other metal coatings used in SEM studies. This method enabled comparison of the nanoarchitecture of UF resins of low (1.0) and high (1.6) formaldehyde/urea (F/U) mole ratios to be made, based on imaging of extremely small size particles as part of UF resin architecture, not described before. Imaging revealed presence of relatively large globular particles (148.084–703.983 nm size range) as well as smaller substructures (28.004–39.604 nm size range) as part of the architecture of 1.0‐mole UF resin. Globular particles were also present in 1.6 mole UF resin, but of considerably smaller size (14.760–50.269 nm). The work presented demonstrates usefulness of osmium coating in unraveling the intricacies of the nanostructural organization of cured UF resins, prompting wider application of this immensely useful but grossly underutilized metal coating type in high resolution SEM examination of biological and materials samples. Microsc. Res. Tech. 76:1108–1111, 2013. © 2013 Wiley Periodicals, Inc.     

Performance assessment of an internal combustion engine at varying dead (reference) state temperatures

This study deals with investigating the effect of varying dead state temperatures on exergy efficiency of a high-oleic methyl ester (HOME) fueled internal combustion engine (ICE). This engine is a 4.5L, four-stroke, four-cylinder, turbocharged, 66.5 kW maximum power capacity John Deere 4045T diesel engine run with HOME, which is genetically modified with a high-oleic soybean oil methyl ester. The test speed is 1400 min⁻¹ at a full load. In the analysis, actual operational data obtained from a study conducted by one of the co-authors at Iowa State University, USA are used. Exergy efficiency values at various dead state temperatures are calculated for comparison purposes since these types of engines may be operated under different outdoor air conditions. The results obtained are discussed from the exergetic point of view. It was found that exergetic efficiency increased as dead state temperature decreased. As a result, exergy efficiency values ranged from 29.78% to 34.93% based on dead state temperatures between −5 °C and 30 °C.     

VARIATION OF PRESSURE WITH RAM SPEED AND DIE PROFILE IN HOT EXTRUSION OF ALUMINUM-6063

Prediction of extrusion pressure, especially in the case of complex die geometries, is an area of continued research interest. Die complexity, usually defined by “shape factor” (the ratio of the perimeter to the cross-sectional area of the profile), critically affects the flow of metal and the pressure required to extrude a given product. Applied strain rate (related directly to the ram speed of the extrusion press) also alters the product quality significantly. The current paper presents results of an ongoing study about effects of ram speed and die profile on extrusion pressure. Experiments were conducted using dies of different complexity to track the effects of ram speed variation and changing die profiles on extrusion pressure. Al-6063, the most popular commercial variety of structural aluminum, was used as the billet material for all experiments.     

Photocatalytic degradation of Basic Red 46 and Basic Yellow 28 in single and binary mixture by UV/TiO2/periodate system

The present study deals with the investigation of photocatalytic degradation and mineralization of C.I. Basic Red 46 (BR46) and C.I. Basic Yellow 28 (BY28) dyes in single and binary solutions as a function of periodate ion concentration (IO(4)(-)), irradiation time, initial pH and initial dye concentrations. First order derivative spectrophotometric method was used for to simultaneous analysis of BY28 and BR46 in binary mixtures. Langmuir-Hinshelwood kinetic model was applied to experimental data and apparent reaction rate constant values were calculated. The apparent degradation rate constant values of BR46 were higher than those of BY28 for all experiments in single dye solutions. On the other hand, the significant reductions were observed for the apparent degradation rate constant values of the BR46 in the presence of BY28 in binary solutions whereas TOC removal efficiency slightly enhanced in binary system. The highest TOC removal efficiency was obtained at pH 3.0 by adding 5mM periodate ion in to the solution in the presence of 1g/L TiO(2) for both dye solutions. After 3h illumination, 68, 76 and 75% mineralization were found for 100mg/L BY28, 100mg/L BR46 and 50+50mg/L mixed solutions, respectively.     

Biomass-based hydrogen production: A review and analysis

In this study, various processes for conversion of biomass into hydrogen gas are comprehensively reviewed in terms of two main groups, namely (i) thermo-chemical processes (pyrolysis, conventional gasification, supercritical water gasification (SCWG)), and (ii) biological conversions (fermentative hydrogen production, photosynthesis, biological water gas shift reactions (BWGS)). Biomass-based hydrogen production systems are discussed in terms of their energetic and exergetic aspects. Literature studies and potential methods are then summarized for comparison purposes. In addition, a biomass gasification process via oxygen and steam in a downdraft gasifier is exergetically studied for performance assessment as a case study. The operating conditions and strategies are really important for better performance of the system for hydrogen production. A distinct range of temperatures and pressures is used, such as that the temperatures may vary from 480 to 1400 °C, while the pressures are in the range of 0.1–50 MPa in various thermo-chemical processes reviewed. For the operating conditions considered the data for steam biomass ratio (SBR) and equivalence ratio (ER) range from 0.6 to 10 and 0.1 to 0.4, respectively. In the study considered, steam is used as the gasifying agent with a product gas heating value of about 10–15 MJ/Nm³, compared to an air gasification of biomass process with 3–6 MJ/Nm³. The exergy efficiency value for the case study system is calculated to be 56.8%, while irreversibility and improvement potential rates are found to be 670.43 and 288.28 kW, respectively. Also, exergetic fuel and product rates of the downdraft gasifier are calculated as 1572.08 and 901.64 kW, while fuel depletion and productivity lack ratios are 43% and 74.3%, respectively.     

Performance assessment of a geothermally heated building

This study deals with an exergetic performance evaluation of a geothermally heated building. This building used in the analysis has a volume of 1147.03 m³ and a net floor area of 95.59 m², while indoor and exterior air temperatures are 20 and 0 °C, respectively. The geothermal heating system used for the heat production was constructed in the Ozkilcik heating center, Izmir, Turkey. Thermal water has a pressure of 6.8 bar, a temperature of 122 °C and a mass flow rate of 54.73 kg/s, while it is reinjected at 3.2 bar and 72 °C. The system investigated feeds three regions. Among these, the Ozkanlar region has supply/return pressure and temperature values of 4.6/3 bar and 80/60 °C, respectively. Energy and exergy flows are studied to quantify and illustrate exergy destructions in the overall system. Total exergy input rate to the system is found to be 9.92 kW and the largest exergy destruction rate occurs in the primary energy transformation at 3.85 kW.