Eine Analyse von mononitriertem Toluol und von Toluidin

Ohne Zusammenfassung     

A comparative study of the optical properties of Fe3+ in ordered LiGa5O8 and LiAl5O8

Measurements are reported on the fluorescence and excitation spectra of Fe³⁺-doped LiGa₅O₈ in the ordered phase. Spectral determinations were made with powder samples containing 0.01 to 1% atomic weight of Fe³⁺, within the temperature range 300 K to 25 K. A comparison is presented between the optical properties of trivalent iron in lithium gallate and in lithium aluminate, LiAl₅O₈, both in their ordered phases. The best fit with crystal field parameters B, C, and Dq, yields the following values for these parameters: Dq = 906 cm^-1, B = 594 cm^-1, and C = 3 737 cm^-1. As is the case with LiAl₅O₈:Fe³⁺, the Stokes shift in LiGa₅O₈:Fe³⁺ is very large, 3 624 cm^-1, although somewhat smaller than the 4 300 cm^-1 seen in LiAl₅O₈:Fe³⁺.     

Integral and asymptotic representations of geo-stable densities

The fact that geo-stable distributions do not have an explicit representation causes severe difficulties in empirical work. Here, we provide representations for geometric-stable probability densities in terms of fast converging integrals.     

Mercury methylation in a tropical macrophyte: influence of abiotic parameters

Sediment has been considered to be one of the most important mercury methylation sites, but recent studies have demonstrated a new site that is relevant, i.e. the roots of floating aquatic macrophytes, where high methylation is observed. The effects of temperature, pH and electric conductivity on net mercury methylation were studied in the roots of the water‐hyacinth Eichhornia crassipes of a freshwater coastal lagoon (Lagoinha, RJ, Brazil). Root samples were incubated, over three days, with ²⁰³HgCl₂ addition, at different temperatures (10–90 °C), pH values (3–8) and different electrolytic solutions (KClO₄, KCl and CaCl₂, at 1, 5, 10, 25 and 50 mM , ranging between 18 and 760 µS cm⁻¹). ²⁰³Hg‐labeled methylmercury (Me²⁰³Hg) was extracted in toluene, after acid leaching, and measured by β‐counting. Up to 35% of mercury added was converted to MeHg Methylation increased from 10 to 35 °C, and decreased thereafter. The process was completely inhibited at 90 °C. At pH values of 6 and 7 methylation was stimulated and a significant decrease was verified at pH 8. Increasing KClO₄ concentrations led to a significant decrease in the methylation rates, while for KCl and CaCl₂ solutions only a slight decrease was observed. Copyright © 1999 John Wiley & Sons, Ltd.     

Stability of characterization of exponential distribution by the discretization property

The relationship is studied between certain estimates of the distribution density, and also between problems of parametric estimation of the density and pointwise estimation of parametric functions.Translated from Problemy Ustoichivosti Stokhasticheskikh Modelei — Trudy Seminara, pp. 63–64, 1980.     

Analysis of a three node queueing network

The three node Jackson queueing network is the simplest acyclic network in which in equilibrium the sojourn times of a customer at each of the nodes are dependent. We show that assuming the individual sojourn times are independent provides a good approximation to the total sojourn time. This is done by simulating the network and showing that the sojourn times generally pass a Kolmogorov-Smirnov test as having come from the approximating distribution. Since the sum of dependent random variables may have the same distribution as the sum of independent random variables with the same marginal distributions, it is conceivable that our approximation is exact. However, we numerically compute upper and lower bounds for the distribution of the total sojourn time; these bounds are so close that the approximating distribution lies outside of the bounds. Thus, the bounds are accurate enough to distinguish between the two distributions even though the Kolmogorov-Smirnov test generally cannot.