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61.
José A. Ferrari 《General Relativity and Gravitation》1990,22(1):19-32
In this paper we investigate the (static) solution of the Kaluza-Klein equations for a cylindrically symmetric current distribution. Specifically, we are interested in the fields generated by a long, cylindrical solenoid. We shall examine in some detail the concept of effective mass of a charged test particle. We shall show that, for a certain charge-to(rest)mass ratio of the test particle, the effective mass becomes imaginary at a certain distance from the axis of our solenoid. 相似文献
62.
Summary Bhattacharya, Chernoff and Yang (1983) proposed a nonparametric estimate for the slope of a regression lineY =
o
X + V subjected to the truncationYy
0. The estimate corresponds to the zero-crossing of a random functionS
n
(). In this paper an estimate for the asymptotic variance of the estimate of the slope is proposed and the rate of convergence is given. The proofs rest heavily on the local behavior ofS
n
() in the neighborhood of the true value o. 相似文献
63.
A critical review of known results about the permanence conditions for the null character of the solutions to the (vacuum) Maxwell equations, is presented. Concomitants of the electromagnetic field and the metric tensor are constructed, which give the principal directions of the field in covariant form. The known permanence conditions are generalized in order to includeall the (local) null fields; the above concomitants allow these conditions to be explicitly formulated in terms of the electromagnetic field.Supported in part by Conselleria de Cultura, Educació i Ciència de la Generalitat Valenciana. 相似文献
64.
Reproducibility for successive determinations with a hanging mercury drop electrode is assessed in relation to solution stirring, drop size and back-diffusion to the mercury thread. The effect of experimental parameters such as drop size, deposition time and gallium concentration on the observed stripping current is investigated. The interference of zinc present in a 0.5M NaSCN + 4.2M NaClO(4) supporting electrolyte on the gallium detection limit and calibration plots is described. Formation of an intermetallic compound with a Zn:Ga ratio of 2:3 and its destruction by co-deposition of zinc with Sb are reported. A detection limit of 10(-8)M gallium was obtained in the presence of 10(-5)M Sb(III). 相似文献
65.
66.
67.
68.
Summary The complexestrans-[Ru(NH3)4(H2O)PPh3](PF6)2 and [Ru(NH3)5L](PF6)2, (L=AsPh3 or SbPh3) have been isolated and characterized by microanalysis, cyclic voltammetry and ultraviolet-visible spectroscopy. The specific rate constants for the aquation of [Ru(NH3)5L]2+ totrans-[Ru(NH3)4L(H2O)]2+ are (2.5±0.1)×10–5s–1 and (1.8±0.1)×10–5s–1 for L=AsPh3 and SbPh3, respectively, at 25.0±0.1°C; =0.10 mol dm–3, NaO2CCF3. Under the same conditions, the second-order rate constants for the substitution of water intrans-[Ru(NH3)4(H2O)L]2+ by isonicotinamide (isn) are 1.2±0.1, (6.3±0.3)×10–2 and (3.8±0.2)×10–2
m
–1s–1 for L=PPh3, AsPh3, and SbPh3, respectively, suggesting that the order of decreasingtrans-effect is: PPh3AsPh3>SbPh3. The formation constants for thetrans-[Ru(NH3)4L(isn)]2+ complexes are 75±3, (1.40±0.01)×103 and (1.80±0.02)×103M–1 for L=PPh3, AsPh3, and SbPh3, respectively, suggesting that the order of increasingtrans-influence is: SbPh33PPh3. 相似文献
69.
70.
Comparison of different fibers for the solid-phase microextraction of phthalate esters from water 总被引:3,自引:0,他引:3
Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) has been applied to determine six phthalate esters and one adipate ester in water. The SPME parameters were optimized for several commercially available fibers. A 65-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) was the fiber selected and was applied to analysis of water from the Ebro river and the industrial port of Tarragona. The studied compounds were found at concentrations ranging from 0.4 microg l(-1) for di-n-butyl phthalate ester (DnBP) to 3.2 microg l(-1) for bis(2-ethylhexyl) phthalate ester (DEHP). The linear range for real samples was from 0.1 to 10 microg l(-1) for most phthalates, and the limits of detection of the method were between 3 and 30 ng l(-1). Repeatability and reproducibility between days (n = 5) for 1 microg l(-1) samples were below 13 and 18%, respectively. 相似文献