There is an increased interest in measuring naturally occurring radioactive materials (NORM) like coal, fly ash considering health hazards caused by naturally occurring radionuclides. This paper presents activity concentration (AC) of 226Ra, 228Ra, 232Th, 238U and 40K in feed coal, bottom and fly ash samples from Philippines coal-fired thermal power plants using inductively coupled plasma mass spectrometry (ICP-MS) and high-purity germanium gamma spectroscopy (HPGe γ-spectroscopy). Coal, bottom and fly ash samples were digested using a microwave oven with a mixture of HNO3, HClO4 and HF. Uranium (238U) and thorium (232Th) ACs were also analyzed from samples using ICP-MS. A good correlation was found for the measurement of U and Th using both techniques (R2 = 0.97 and 0.94 respectively). ICP-MS measurements showed the highest AC of 232Th and 238U in fly ash and lowest for feed coal samples. With HPGe γ-spectroscopy measurements, highest AC (in Bq kg− 1) of 226Ra, 228Ra, 228Th and 40K, were noticed in fly ash followed by bottom ash and feed coal. ICP-MS method is rapid for the measurement of uranium and thorium in comparison to γ-spectroscopy as secular equilibrium is not required. Activity concentrations of bottom and fly ash samples were found to be within the reported values worldwide and below the International Atomic Energy Agency recommended values for regulatory control. 相似文献
In situ mixtures of CdCl2?TMEDA (0.5 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine) or InCl3 (0.33 equiv) with [Li(tmp)] (tmp=2,2,6,6‐tetramethylpiperidino; 1.5 or 1.3 equiv, respectively) were compared with the previously described mixture of ZnCl2?TMEDA (0.5 equiv) and [Li(tmp)] (1.5 equiv) for their ability to deprotonate anisole, benzothiazole, and pyrimidine. [(tmp)3CdLi] proved to be the best base when used in tetrahydrofuran at room temperature, as demonstrated by subsequent trapping with iodine. The Cd–Li base then proved suitable for the metalation of a large range of aromatics including benzenes bearing reactive functional groups (CONEt2, CO2Me, CN, COPh) or heavy halogens (Br, I), and heterocycles (from the furan, thiophene, pyrrole, oxazole, thiazole, pyridine, and diazine series). Five‐membered heterocycles benefiting from doubly activated positions were similarly dideprotonated at room temperature. The aromatic lithium cadmates thus obtained were involved in palladium‐catalyzed cross‐coupling reactions or simply quenched with acid chlorides. 相似文献
Water pump : Polyion complex (PIC) vesicles are spontaneously formed from PIC microdroplets, which are formed by mixing cationic and anionic polymers (see picture). The formation process can be reversibly controlled by local heating with a focused infrared laser that triggers microphase separation and subsequent water influx. The size of the resulting giant unilamellar vesicles is determined by the initial size of the PIC droplets.
Further study of our aerobic intermolecular cyclization of acrylic acid with 1-octene to afford α-methylene-γ-butyrolactones, catalyzed by the Pd(OCOCF(3))(2)/Cu(OAc)(2)?H(2)O system, has clarified that the accumulation of water generated from oxygen during the reaction causes deactivation of the Cu cocatalyst. This prevents regeneration of the active Pd catalyst and, thus, has a harmful influence on the progress of the cyclization. As a result, both the substrate conversion and product yield are efficiently improved by continuous removal of water from the reaction mixture. Detailed analysis of the kinetic and spectroscopic measurements performed under the condition of continuous water removal demonstrates that the cyclization proceeds in four steps: 1)?equilibrium coordination of 1-octene to the Pd acrylate species, 2)?Markovnikov-type acryloxy palladation of 1-octene (1,2-addition), 3)?intramolecular carbopalladation, and 4)?β-hydride elimination. Byproduct 2-acryloxy-1-octene is formed by β-hydride elimination after step 2). These cyclization steps fit the Michaelis-Menten equation well and β-hydride elimination is considered to be a rate-limiting step in the formation of the products. Spectroscopic data agree sufficiently with the existence of the intermediates bearing acrylate (Pd-O bond), η(3)-C(8)H(15) (Pd-C bond), or C(11)H(19)O(2) (Pd-C bond) moieties on the Pd center as the resting-state compounds. Furthermore, not only Cu(II), but also Cu(I), species are observed during the reaction time of 2-8?h when the reaction proceeds efficiently. This result suggests that the Cu(II) species is partially reduced to the Cu(I) species when the active Pd catalytic species are regenerated. 相似文献
An indirect method for the determination of antimony(III) is described. Antimony(III) is oxidized to antimony(V) by chromium(VI) and the excess of chromium(VI) is then determined spectrophotometrically with diphenylcarbazide. Optimal conditions were established for both the determination of antimony(III) and the elimination or reduction of interferences. Antimony(III) can be determined quickly and easily in the range 0.05–5 mg l?1; the relative standard deviation is 2% for 1.0 mg l?1 antimony(III). The method is applicable to marine sediments and geothermal waters. 相似文献
A kinetic-spectrophotometric method for the determination of bromide (0.004–0.3 mg l?1) based on its catalysis of the oxidation of pyrocatechol violet by hydrogen peroxide in HCl/H2SO4 is described. The effect of bromide is greatly increased in the presence of large amounts of chloride. The relative standard deviations are 6.4 and 13% for 0.034 and 0.010 mg l?1 bromide, respectively (n = 10). Most ions commonly occurring in natural waters do not interfere except for iodide. 相似文献
A stereospecific synthesis of acetyl--valyl-detoxininolactone has been performed and the absolute stereochemistry of detoxinine has been revised to (2, 3, 1′)-2-(2′-carboxy-1′-hydroxyethyl)-3-hydroxypyrrolidine. 相似文献