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981.
The colour reaction of Am(III) with Arsenazo III in several hydroorganic media has been examined systematically on the addition of certain polar water-miscible organic solvents in the course of a search for improved and simple spectrophotometric methods for the estimation of americium. Addition of these substances resulted in the stabilization of colour and brought about a drastic enhancement in the absorbance values. The organic additives studied include acetone, acetonitrile, dimethylformamide, dioxane and ethanol. Among the many solvents tested, alcohol and dioxane proved to be the most effective; highest sensitivity is obtained by using a 60% dioxane-ethanol (11) mixture. The apparent molar absorptivity based on Am content is 184616±9931 mol–1 cm–1 at 655 nm which is about 3 times that attained for the reaction in aqueous medium (65178±1243). Strikingly, this is the highest value reported as yet for its determination. Beer's law is obeyed both in mixed as well as aqueous media. The effects of some experimental variables on colour development have also been studied to optimize the conditions for the assay of Am. 相似文献
982.
983.
984.
Experimental parameters affecting the analytical response of arsenic in differential pulse anodic-stripping voltammetry (DPASV) have been examined. DPASV offers higher sensitivity than linear-scan anodic-stripping voltammetry for similar analysis times. Both techniques have been applied to the NBS Standard Reference Water (SRM 1643) and some polluted water samples. The results on polluted waters compared favourably with those obtained by graphite-furnace atomic-absorption spectroscopy. 相似文献
985.
986.
Subal Chandra Saha Sankar Sengupta 《Journal of Quantitative Spectroscopy & Radiative Transfer》1978,20(3):259-264
An analytic representation for the oscillator-strength sums S(k) for members of the He isoelectronic sequence is proposed. The expression holds for both positive and negative values of k. The values of the moments S(k) exhibit an interesting Z-dependence, where Z is the nuclear charge. This, together with some observations on H- and the mass polarization effect, are discussed. 相似文献
987.
B. N. Desai S. K. Subramanian T. M. Sambamoorthy 《Proceedings Mathematical Sciences》1975,82(1):31-35
Meteorological conditions prevailing over and west of Bombay on the four days on which Bhatet al. (1974) made measurements of radon concentration at different altitudes from the surface to 3·7 km and distances of 0–50 and 350–400 km west of Bombay, do not appear to support their conclusions about airmasses. 相似文献
988.
R. Nacasch Ch. Defoix L. Dobrzynski P.Ladron de Guevara R. Raghavan M. Aguilar-Benitez J. Diaz A. Ferrando E. Gil J.A. Rubio F. Barreiro A. Gurtu L. Montanet A.M. Cooper S.N. Ganguli P.K. Malhotra A. Subramanian 《Nuclear Physics B》1978,135(2):203-223
In this paper we have investigated the properties of the D(1285) and E(1420) meson resonances using the five-body annihilation channels obtained in a large statistics experiment (28 events/μb). The analysis favours the 1+ spin-parity assignment for the D(1285) meson. The dominant decay mode of the D(1285) into is found to be δ(970)π. The situation concerning the E(1420) meson remains confused although not inconsistent with previous analyses. Partial cross sections on resonance production are also presented. 相似文献
989.
Orugunty RS Wright DL Battiste MA Helmich RJ Abboud K 《The Journal of organic chemistry》2004,69(2):406-416
It has been known for several decades that a highly functionalized family of tetrahalobicyclo[3.2.1]octadienes are readily available through the cycloaddition of furan or cyclopentadiene with either tetrachloro- or tetrabromocyclopropene. However, the application of these highly functionalized building blocks in synthesis has remained relatively unexplored in relation to their better-known counterparts derived through oxyallyl cation additions. As a first step toward utilizing these highly versatile intermediates in synthesis, a study of the addition of various nucleophiles to the halogenated nucleus has been conducted. It has been found that these halogenated systems are amenable to a wide range of functionalizations in high yields and with good selectivities. 相似文献
990.
We consider the following system of integral equations $$u_i(t)=\int^1_0g_i(t,s)f(s,u_1(s),u_2(s),\cdots,u_n(s))ds,\quad t\in \lbrack 0,1\rbrack,1\leq i\leq n.$$ Our aim is to establish criteria such that the above system has a constant-sign solution (u1, u2, …, u n) ∈ (Lp[0, 1])n, where the integer 1 ≤ p < ∞ is fixed. We shall tackle the case when f is ‘nonnegative’ as well as the case when f is ‘semipositone’. The above problem is also extended to that on the half-line [0, ∞) $$u_i(t)=\int^1_0g_i(t,s)f(s,u_1(s),u_2(s),\cdots,u_n(s))ds,\quad t\in \lbrack 0,\infty ),1\leq i\leq n.$$ 相似文献