The effect of thallium addition on differential thermal analysis of glassy selenium. Part 1

The effect of thallium on the phenomena accompanying the thermally induced structural changes in different compositions of the chalcogenide system Tl _x Se_1–x, withx = 0.0 to 0.9, has been investigated using differential thermal analysis measurements. It is possible to prepare massive homogeneous glassy samples with thallium contents up to 10 at %. Glasses with some embedded crystallites are obtained up to 40 at % Tl. The coefficient of the glass-forming tendency (K _gl) increases with increasing selenium content. In the binary system Tl-Se, one (or more) of the phases are likely to be more unstable with respect to crystallization than was the initially homogeneous system. The activation energy of crystallization for the glasses fromx = 0.0 to 0.3, varies from 1.0 to 4.5 eV for the low-temperature phase and from 1.7 to 2.5 eV for the high-temperature phase.     

Optical properties of amorphous Ge28-xSe72Sbx thin films

Bulk glasses of formal composition Ge_28−xSe₇₂Sb_x with 0≤x≤28 were prepared by applying the quench technique. The optical transmission spectra—using a melt were measured in the range from 200 to 1200 nm for Ge_28−xSe₇₂Sb_x films which are prepared by thermal evaporation technique. A simple, straightforward procedure suggested by Swanepoel, which is based on the use of interference fringes, has been applied to calculate the film thickness. On other hand the driving absorption coefficient (α), consequently the band tail width E_e and the optical band gap have been estimated. The real (ε′) and imaginary parts (ε″) of the dielectric constant have been determined and the optical band gap can also be calculated as a function of imaginary part (ε″). The dispersion parameters such as E₀(single-oscillator energy), E_d (dispersive energy) and M₋₁, M₋₃ (moments) were discussed in terms of the single-oscillator Wemple–DiDomenico model.     

Electrical properties and phase transition of Ge1−x Sn x Se2.5 thin films

The Ge_1–x Sn _x Se_2.5 system was prepared by melting the correct ratio of high purity elements in quartz evacuated ampoules followed by quenching in ice. It was found that, within the Ge_1–x Sn _x Se_2.5 system, a glassy state can be formed when 0 x 0.4. On increasing x to 0.6 a glassy state could not be obtained, as is confirmed by X-ray diffraction. Differential thermal analysis (DTA) was carried out to study the effect of composition on the stability of amorphous phase. Ge_1–x Sn _x Se_2.5 (where 0 x 0.6) thin films have been prepared by the thermal evaporation technique. The electrical conductivity of the thin films have been studied as a function of composition and film thickness.     

Optical parameter studies of thermally evaporated As-Se-Sn glassy system

The optical properties of As₃₀Se_70-xSn_x with (x = 0, 1, 2 and 3 at Sn %) thin films have been investigated. The films used in these studies were thermally evaporated. The structural characterization revealed that the as-deposited films were amorphous in nature. The spectral and optical parameters have been investigated using spectrophotometric measurements of transmittance in the wavelength range (200–1100 nm). The optical constants were determined from the interference maxima and minima using the Swanepole method. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-Didomenico model. The optical-absorption edge and the optical band gap are calculated from the absorption coefficient values using the non direct transition model proposed by Tauc’s extrapolation procedure. The relation between the optical gap and chemical composition in As-Se-Sn glassy system is discussed in terms of the average heat of atomization H_s and the average coordination number N_c.     

Characterization of short-range order in an amorphous Cd–Se–Te system by wide angle X-ray scattering(WAXS)

Short-range orders of Cd_xSe_70−xTe₃₀ amorphous alloys of a chalcogenide system with 2≤x≤10 have been studied by wide-angle X-ray scattering (WAXS). Once the hypotheses on the local order of the alloy had been formulated, the radial distribution function (RDF) analysis have make it possible to evaluate them referring specifically to the coordination of the atoms. The structural parameters such as atomic distance between the different possible pairs of atoms in each element J(r), the structure factor F(q), the pair distribution function G(r) and the coordination numbers for amorphous samples have been discussed. Moreover, in our system, under study, the average coordination numbers of the three different atoms involved and their distance to the first coordination sphere have been determined. However, the extraction of the inverse Fourier transforms to generated atomic distribution function has led us to a simulated reduced interference function Q(q).     

Glass formation, optical properties and local atomic arrangement of chalcogenide systems GeTe-Cu and GeTe-In

Glass-forming regions of ternary Ge-Te-Cu and Ge-Te-In chalcogenide glasses are examined by differential scanning calorimeter and by X-ray diffraction. Glass transition and crystallization temperatures are about 120 °C To 260 °C, respectively higher than those of binary Ge-Te glass [T. Katsuyama and M. Matsumura, Infrared Optical Fibres (Adam Hilger, London, 1989) p. 212]. Only a small range of compositions after quenching the melting alloy is characterized by disordered state, but this range of composition is widened when using a vapor deposition technique. These compositions have two glass transition temperatures, showing the existence of phases in the sample. Both the Kissinger equation and modified Kissinger kinetic analysis were adopted to estimate activation energy and the reaction order of the process. Ge-Te-Cu and Ge-Te-In crystallized in two stages, nucleation and crystal growth. These two processes can be distinguished by exothermal crystallization patterns. An atomic radial distribution analysis has been made on bulk Ge₁Te₄In _x and Ge₁Te₄Cu _x with x = 0.1 by X-ray diffraction techniques. The radial distribution function (RDF) is discussed in terms of the structure factor F(s). Thin films of Ge-Te-Cu and Ge-Te-In are deposited on silicate glass and silicon wafer substrates by vacuum evaporation. The optical energy E _opt are determined from transmission and reflection data of a deposited films. The value of E _opt decreased by increasing metal additive such as Cu or In and discussed as a function of the conditions of their preparation such as substrate type.     

Fuzzy Numbers in Cost Range Estimating

Range estimating is a simple form of simulating a project estimate by breaking the project into work packages and approximating the variables in each package using statistical distributions. This paper explores an alternate approach to range estimating that is grounded in fuzzy set theory. The approach addresses two shortcomings of Monte Carlo simulation. The first is related to the analytical difficulty associated with fitting statistical distributions to subjective data, and the second relates to the required number of simulation runs to establish a meaningful estimate of a given parameter at the end of the simulation. For applications in cost estimating, the paper demonstrates that comparable results to Monte Carlo simulation can be achieved using the fuzzy set theory approach. It presents a methodology for extracting fuzzy numbers from experts and processing the information in fuzzy range estimating analysis. It is of relevance to industry and practitioners as it provides an approach to range estimating that more closely resembles the way in which experts express themselves, making it practically easy to apply an approach.     

Lipidemic effect of methanol

The effect of methanol on some of the lipid components in serum was studied in rats. Methanol was administered by stomach tube in doses of 2 and 6 ml/kg b.wt daily for 21 and 6 days, respectively. Methanol was found to accumulate lipids; thus, cholesterol, phospholipids and triglycerides increased significantly. Concurrently, modification of the lipoid content of organs has been considered. It was concluded that methanol and not only formate, is toxic to rats, inspite of the alleged difference in routes of its metabolism in primates and rodents.     

Entphosphorung beim Einblasen von Kalkstaub mit Sauerstoff in flüssigen Stahl

Möglichkeiten zur Verbesserung der Entphosphorung bei den Sauerstoffaufblas-Verfahren. Versuche zum Einblasen von Kalkstaub mit Sauerstoff in das Bad. Schnelles Erreichen des Phosphorgleichgewichts beim Einblasen von Kalkstaub.     

Recovery and susceptibility patterns of faecal streptococci bacteriophages

The occurrence of faecal streptococci and their phages was investigated in 20 fresh sewage samples. By using two primary enrichment media bearing MgSO₄ and l-tryptophan for phage recovery, 19 out of 20 sewage samples yielded at least one phage type. Furthermore, host range studies for 16 phage types showed that phages attacked Str. faecalis and its two variants did not attack Str. faecium, Str. bovis and Str. equinus. In addition, the relationship between atypical and typical species was recorded on the basis of phage typing.