Crystallization kinetics of chalcogenide glass Se0.8 Te0.2

The crystallization kinetics of the chalcogenide glass Se_0.8Te_0.2 was studied by means of differential scanning calorimetry. The variation in partial area (X) with temperature (T) revealed that the transition from the amorphous to the crystalline phase occurs in two dimensions.Activation energies were determined for both the glass transition (E _t) and the crystallization (E _c).E _t was calculated from the variation inT _g with the heating rate (a).E _c was determined by three different methods: (i) variation inX withT, (ii) variation inT _p witha, and (iii) variation inT _c witha.E _t andE _c have values of 161.01±2.75 and 84.75 ±8.21 kJ/mol, respectively.

---

Zusammenfassung Mittels DSC wurde die Kristallisierungskinetik des Chalkogenidglases Se_0.8Te_0.2 untersucht. Eine Änderung partieller Gebiete (X) mit der Temperatur (T) zeigte, daß der Übergang von der amorphen zur kristallinen Phase zweidimensional verläuft.Es wurde die Aktivierungsenergie sowohl für den Glasübergang (E _t) als auch für die Kristallisierung (E _c) bestimmt.E _t wurde mittels der Abhängigkeit vonT _g von der Aufheizgeschwindigkeit (a) ermittelt.E _c wurde auf drei verschiedene Wege bestimmt: (i) Änderung vonX in Abhängigkeit vonT, (ii) Änderung vonT _p in Abhängigkeit vona und (iii) Änderung vonT _c in Abhängigkeit vona. Die Werte vonE _t undE _c betragen 161.01±2.75 bzw. 84.75±8.21 kJ/mol.

---

---

This work was partly supported by a Grant-in-Aid for Scientific Research from the GTZ GmbH and DAAD, W. Germany.     

Large-scale simulations of a-Si:H: the origin of midgap states revisited

Large-scale classical and quantum simulations are used to generate a-Si:H structures. The bond-resolved density of the occupied electron states discloses the nature of microscopic defects responsible for levels in the gap. Highly strained bonds give rise to band tails and midgap states. The latter originate mainly from stretched bonds, in addition to dangling bonds, and can act as hole traps. This study provides strong evidence for photoinduced degradation (Staebler-Wronski effect) driven by strain, thus supporting recent work on a-Si, and sheds light on the role of hydrogen.     

MHD free convective flow and mass transfer over a stretching sheet with chemical reaction

The effect of chemical reaction on free convective flow and mass transfer of a viscous, incompressible and electrically conducting fluid over a stretching surface is investigated in the presence of a constant transverse magnetic field. The non-linear boundary layer equations with the boundary conditions are transferred by a similarity transformation into a system of non-linear ordinary differential equations with the appropriate boundary conditions. Furthermore, the similarity equations are solved numerically by using a fourth order Runge-Kutta scheme with the shooting method. Numerical results of the skin friction coefficient, the local Nusselt number Nu, the local Sherwood number Sh, as will as the velocity, temperature and concentration profiles are presented for gases with a Prandtl number of 0.71 for various values of chemical reaction parameter, order of reaction, magnetic parameter and Schmidt number.     

Isotopic effect in extended x-ray-absorption fine structure of germanium

Extended x-ray absorption fine structure has been measured on two powdered samples of (70)Ge and (76)Ge as a function of temperature from 20 to 300 K. The effect of isotopic mass difference on the amplitude of relative atomic vibrations is neatly evidenced by the temperature dependence of the difference of Debye-Waller factors. The isotopic effect is also detected on the difference of nearest-neighbor average ineratomic distances, thanks to a resolution better than 10 fm.     

Improvement of the electrical properties of Se3Te1 thin films by In additions

The electronic and photoconductivity properties of semiconducting chalcogenide glasses have been largely stimulated by attractive micro-electronic device applications. The present paper aims to study the effect of In additions on the steady state and transient photoconductivity of amorphous In_x(Se₃Te₁)_100 ? x (0 ≤ x ≤ 10 at.%) chalcogenide films. It was found that, the Indium additions lead to the decrease of both the activation energies (ΔE_dc in the dark and ΔE_ph for the photoelectrical conduction) and the optical band gap E_g that improved the electrical properties of these films. The photoconductivity increases while photosensitivity changes from 8.73 to 7.18 with the increase of In content. The exponential dependence of photocurrent on the light intensity suggests that, the recombination mechanism in these films is due to bimolecular recombination. The transient photoconductivity measurements stated that, the carrier lifetime decreased by the increase of the light intensity and In content. The obtained results were discussed in terms of the width of localized states (Mott and Davis model) and the chemical-bond approach.     

A novel and facile reaction to N6‐alkylated adenosine via benzotriazole as a synthetic auxiliary

The reaction of benzotriazole with aliphatic, aromatic or heteroaromatic aldehyde and adenosine leads to a benzotriazole adduct which is reduced with sodium borohydride to the corresponding N⁶‐alkylated adenosine derivatives. This procedure is also utilized in a new route to N⁶‐(3‐iodobenzyl)adenosine‐5′‐N‐methyluronamide (IB‐MECA) which is considered an important adenosine agonist at A₃ adenosine receptors.     

Power-Modified Kies-Exponential Distribution: Properties,Classical and Bayesian Inference with an Application to Engineering Data

We introduce here a new distribution called the power-modified Kies-exponential (PMKE) distribution and derive some of its mathematical properties. Its hazard function can be bathtub-shaped, increasing, or decreasing. Its parameters are estimated by seven classical methods. Further, Bayesian estimation, under square error, general entropy, and Linex loss functions are adopted to estimate the parameters. Simulation results are provided to investigate the behavior of these estimators. The estimation methods are sorted, based on partial and overall ranks, to determine the best estimation approach for the model parameters. The proposed distribution can be used to model a real-life turbocharger dataset, as compared with 24 extensions of the exponential distribution.     

Bayesian and Classical Inference under Type-II Censored Samples of the Extended Inverse Gompertz Distribution with Engineering Applications

In this article, we introduce a new three-parameter distribution called the extended inverse-Gompertz (EIGo) distribution. The implementation of three parameters provides a good reconstruction for some applications. The EIGo distribution can be seen as an extension of the inverted exponential, inverse Gompertz, and generalized inverted exponential distributions. Its failure rate function has an upside-down bathtub shape. Various statistical and reliability properties of the EIGo distribution are discussed. The model parameters are estimated by the maximum-likelihood and Bayesian methods under Type-II censored samples, where the parameters are explained using gamma priors. The performance of the proposed approaches is examined using simulation results. Finally, two real-life engineering data sets are analyzed to illustrate the applicability of the EIGo distribution, showing that it provides better fits than competing inverted models such as inverse-Gompertz, inverse-Weibull, inverse-gamma, generalized inverse-Weibull, exponentiated inverted-Weibull, generalized inverted half-logistic, inverted-Kumaraswamy, inverted Nadarajah–Haghighi, and alpha-power inverse-Weibull distributions.     

Novel structural and magnetic properties of Mg doped copper nanoferrites prepared by conventional and wet methods

Nanoferrites of the general formula Cu_1−xMg_xFe₂O₄ with 0≤x≤0.6 were prepared by standard ceramic and wet methods. The structure was studied by X-ray diffraction and IR spectroscopy. The density and lattice constant were calculated and reported. The particle size of the prepared nanoferrites ranged from 8.7 to 41.1 nm. It was found that the lattice parameter decreases with increasing cation substitution of Mg²⁺ due to the difference of ionic radius and atomic mass. The dc magnetic susceptibility was measured out using Faraday's method. The magnetic hysteresis measurement was performed using a vibrating sample magnetometer. Magnetic constants such as Curie temperature, effective magnetic moment, saturation magnetization, remanent magnetization and corecivicty were obtained and reported. The magnetic constants decrease with increasing Mg²⁺, except the remanent magnetization which increased.