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Influence of cooking method on arsenic retention in cooked rice related to dietary exposure 总被引:1,自引:0,他引:1
Rahman MA Hasegawa H Rahman MA Rahman MM Miah MA 《The Science of the total environment》2006,370(1):51-60
Arsenic concentration in raw rice is not only the determinant in actual dietary exposure. Though there have been many reports on arsenic content in raw rice and different tissues of rice plant, little is known about arsenic content retained in cooked rice after being cooked following the traditional cooking methods employed by the people of arsenic epidemic areas. A field level experiment was conducted in Bangladesh to investigate the influence of cooking methods on arsenic retention in cooked rice. Rice samples were collected directly from a severely arsenic affected area and also from an unaffected area, to compare the results. Rice was cooked according to the traditional methods employed by the population of subjected areas. Arsenic concentrations were 0.40+/-0.03 and 0.58+/-0.12 mg/kg in parboiled rice of arsenic affected area, cooked with excess water and 1.35+/-0.04 and 1.59+/-0.07 mg/kg in gruel for BRRI dhan28 and BRRI hybrid dhan1, respectively. In non-parboiled rice, arsenic concentrations were 0.39+/-0.04 and 0.44+/-0.03 mg/kg in rice cooked with excess water and 1.62+/-0.07 and 1.74+/-0.05 mg/kg in gruel for BRRI dhan28 and BRRI hybrid dhan1, respectively. Total arsenic content in rice, cooked with limited water (therefore gruel was absorbed completely by rice) were 0.89+/-0.07 and 1.08+/-0.06 mg/kg (parboiled) and 0.75+/-0.04 and 1.09+/-0.06 mg/kg (non-parboiled) for BRRI dhan28 and BRRI hybrid dhan1, respectively. Water used for cooking rice contained 0.13 and 0.01 mg of As/l for contaminated and non-contaminated areas, respectively. Arsenic concentrations in cooked parboiled and non-parboiled rice and gruel of non-contaminated area were significantly lower (p<0.01) than that of contaminated area. The results imply that cooking of arsenic contaminated rice with arsenic contaminated water increases its concentration in cooked rice. 相似文献
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The focus of this paper is to determine flammability characteristics of rubber materials that are common to vehicle tires, conveyor belts, and electrical power cable insulation and to compare the thermal magnitude of cargo quantities of these materials to other fuels that are publicly transported. Although a literature review was performed, very little data was found on this topic. Standard flammability test procedures were used to measure the critical flux for ignition, critical ignition temperature, and heat release rates (HRR) of rubber compounds common to tire tread materials and conveyor belt covers. Both the intermediate scale calorimeter: ISO 14696, ASTM E-1623 (ICAL) and the cone calorimeter: ISO E-5660, ASTM 1354 (Cone) provided the bulk of the data. Critical ignition flux and vertical flame spread data for rubber based electrical insulations were determined using a radiant panel from a modified ASTM flame spread apparatus: ASTM E-162. thermogravimetric analysis was also used to evaluate thermal decomposition progression of selected test materials. Further, suppression tests were conducted on tire piles to evaluate agents to extinguish and control tire fires. Also, the HRR of the tire piles were measured and compared to work performed by others. Results confirm that the area heat release rate of rubber materials is directly proportional to exposure flux intensity. The critical exposure flux for ignition of a variety of rubber-based materials is approximately 20 kW/m2 to 30 kW/m2 and the critical temperature for piloted and non-piloted ignition were independent of exposure intensity at ~400°C and ~600°C respectively. In large quantities, rubber tire loads have total HRR comparable to the heat released from similar areas of liquid hydrocarbon spills. 相似文献
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Masatoshi Hasegawa Masahito Horiuchi Kyoko Kumakura Junko Koyama 《Polymer International》2014,63(3):486-500
Alkyl‐substituted cyclobutanetetracarboxylic dianhydrides (CBDAs) were synthesized by photo‐dimerization of alkyl‐substituted maleic anhydrides to obtain novel colorless polyimides (PIs). Dimethyl‐substituted CBDA (DM‐CBDA) showed much higher polymerizability with various diamines than conventional cycloaliphatic tetracarboxylic dianhydrides and led to high molecular weights of PI precursors. Polyaddition of non‐substituted CBDA and trans‐1,4‐cyclohexanediamine (t‐CHDA) was completely inhibited by salt formation in the initial reaction stage. The use of DM‐CBDA allowed the formation of a homogeneous/viscous PI precursor solution by overcoming the salt formation problem. The prominent substituent effect probably reflects how the methyl substituents of DM‐CBDA contributed to increasing the salt solubility. Some of the thermally imidized DM‐CBDA‐based systems simultaneously possessed non‐coloration, low coefficient of thermal expansion (CTE), very high Tg exceeding 300 °C and very low dielectric constant. Copolymerization was very effective for improving the solubility of DM‐CBDA‐based PIs. The copolyimide cast films prepared via chemical imidization displayed a further decreased CTE without sacrificing other target properties, suggesting that the present materials can be useful as plastic substrates in display devices. The mechanism of self‐chain orientation behavior during solution casting is also discussed. A potential application of the copolyimide systems as optical compensation film materials in liquid crystal displays is proposed. © 2013 Society of Chemical Industry . 相似文献
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Masatoshi Hasegawa Mari Fujii Junichi Ishii Shinya Yamaguchi Eiichiro Takezawa Takashi Kagayama Atsushi Ishikawa 《Polymer》2014
A novel cycloaliphatic monomer for polyimides (PI), 1S,2S,4R,5R-cyclohexanetetracarboxylic dianhydride (H′-PMDA) is proposed in this work. H′-PMDA shows high polymerizability with various diamines in contrast to its isomer, i.e., conventional hydrogenated pyromellitic dianhydride (H-PMDA) and leads to highly flexible and colorless PI films with very high Tg's. In particular, the combinations with rigid structures of diamines give rise to PIs with significantly decreased coefficients of thermal expansion (CTE) owing to high extents of in-plane chain orientation induced by thermal imidization, whereas the H-PMDA-based counterparts do not. The decreased CTE reflects structural rigidity/linearity of the H′-PMDA-based diimide units as supported by liquid crystallinity observed in the corresponding model compound. Solution casting of a chemically imidized PI derived from H′-PMDA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) results in a lower CTE than that of the thermally imidized counterpart, suggesting the presence of a self-orientation phenomenon during solvent evaporation. The mechanism is proposed in this work. H′-PMDA/TFMB and its copolymer systems can be useful as plastic substrates in image display devices and/or novel coating-type optical compensation films. 相似文献