Changes produced in etching parameters of CR-39 by high-dose pre- and post-γ irradiation

The effect of post- and pre-high doses of γ–radiation in CR-39 plastic detectors has been studied in the dose range of 3×10¹?10⁶ Gy. Some properties like bulk-etch rate (V _B), track-etch rate (V _T), sensitivity (V _T/V _B) and efficiency have been found out for different gamma doses from a ⁶⁰Co source in CR-39. It is found that V _B and V _T remain almost invariant up to gamma doses of 10⁴ Gy. Then they start increasing slowly till 10⁵ Gy. Between 10⁵ Gy and 10⁶ Gy there is a sharp increase of V _B and V _T values for pre- and post-gamma exposed samples. The present data are compared with the previous literature.     

Operator inequalities related to the Corach–Porta–Recht inequality

We prove some refinements of an inequality due to X. Zhan in an arbitrary complex Hilbert space by using some results on the Heinz inequality. We present several related inequalities as well as new variants of the Corach–Porta–Recht inequality. We also characterize the class of operators satisfying $6{\mathit{SXS}}^{-1}+S^{-1}\mathit{XS}+\mathit{kX}6?(k+2)6X6$ under certain conditions.     

Determination of thorium and uranium contents in soil samples using SSNTD’s passive method

Thorium-to-uranium ratios have been determined in different soil samples using CR-39 and LR-115-II solid-state nuclear track detectors (SSNTDs). A calibration method based on determination of SSNTD registration sensitivity ratio for α-particles of thorium and uranium series has been developed. Thorium and uranium contents of the standard soil samples have been determined and compared with its known values. There is a good agreement between the results of this method and the values of standard samples. The method is simple, inexpensive, non-destructive and has a wide range of applications in environment, building materials and petroleum fields.     

First principle studies on structural,electronic, elastic,optical, and thermoelectric properties of XGeCl3 (X = Rb/Cs): Promising compounds for green energy application

This study employed density functional theory (DFT) embedded in Wien2K code to evaluate the physical features of the XGeCl₃ (X = Rb/Cs) cubic halide perovskites. The structural optimization has been performed considering generalized gradient approximation (GGA) and electronic properties have been computed considering modified Becke-Johnson potential (mBJ). The formation energy and phonon dispersion analysis establish the stability of the investigated compounds. Mechanical stability is further confirmed by the computed diverse elastic coefficients. It has been discovered that the examined substances are naturally ductile. The refractive index, reflectivity, and absorption coefficient, are among the optical parameters that have been estimated and analyzed. Interesting results have been obtained for the transport properties of XGeCl₃ (X = Rb/Cs). The XGeCl₃ (X = Rb/Cs) exhibits a high Seebeck coefficient (X = Rb/Cs) and the largest figure of merit (about 0.99), indicating significant potential for thermoelectric applications.     

Rank one operators and norm of elementary operators

Let A be a standard operator algebra acting on a (real or complex) normed space E. For two n-tuples A = (A₁, … , A_n) and B = (B₁, … , B_n) of elements in A, we define the elementary operator R_A,B on A by the relation for all X in A. For a single operator A∈A, we define the two particular elementary operators L_A and R_A on A by L_A(X) = AX and R_A(X) = XA, for every X in A. We denote by d(R_A,B) the supremum of the norm of R_A,B(X) over all unit rank one operators on E. In this note, we shall characterize: (i) the supremun d(R_A,B), (ii) the relation , (iii) the relation d(L_A − R_B) = ∥A∥ + ∥B∥, (iv) the relation d(L_AR_B − L_BR_A) = 2∥A∥ + ∥B∥. Moreover, we shall show the lower estimate d(L_A − R_B) ? max{sup_λ∈V(B)∥A − λI∥, sup_λ∈V(A)∥B − λI∥} (where V(X) is the algebraic numerical range of X in A).     

Effective permittivity of periodic composite materials: Numerical modeling by the finite element method

The effective properties of composite materials are closely related to the composition and arrangement of its constituents. Many studies and articles are actively studying the dielectric properties of heterogeneous structures with random and periodic arrangement. In the quasistatic limit, we use the finite element method as a numerical tool to evaluate the effective permittivity of two and three component composites. Two heterostructures are investigated; the first is formed by crossed dielectric cylinders in permanent contact and arranged in three layers. The cylinders are immersed in a dielectric host medium. The second structure is similar to the first except that the tubes are covered by an interphase layer. The numerical tool used to extract the exact value of the effective permittivity takes into account all internal multipolar interactions which contribute to the polarization of the material medium. The impacts of the relative permittivity and volume fraction of cylinders, the thickness of interphase and its dielectric constant are reported. The Maxwell–Garnett theory fails to predict the effective permittivity of the studied structures for high volume fraction and permittivity contrast. To overcome this problem, an amendment was made to the McLachlan equation McQ also termed the Two Exponent Single Percolation Equation TESPE. The first exponent t is held equal to 1 and the other exponent s is depending on the volume fraction. s is calculated so that the whole values of the effective permittivity obtained by the McQ rule are exactly the same values obtained by the simulations. Finally, we obtained a chart and a model to find the values of s, a fast way that is very useful for practitioners and design engineers of composite materials.     

Optical properties of a magneto-donor in a quantum dot

The temperature-dependent magnetoresistance effect is investigated in a magnetically modulated two-dimensional (2D) electron gas (2DEG) which can be realized by depositing two parallel ferromagnets on top of a 2DEG electron gas. In the resonant tunnelling regime the transmission for the parallel and antiparallel magnetization configurations shows a quite distinct dependence on the longitudinal wave vector of the incident electrons. This leads to a very large magneto resistance ratio with a strong temperature dependence.     

Direct determination of bulk etching rate for LR-115-II solid state nuclear track detectors

The thickness of the removed layer of the LR-115-II solid state nuclear track detector during etching is measured directly with a rather precise instrument. Dependence of bulk etching rate on temperature of the etching solution is investigated. It has been found that the bulk etching rate is 3.2 μm/h at 60°C in 2.5 N NaOH of water solution. It is also found that the track density in detectors exposed to soil samples increases linearly with the removed layer.     

Synthesis of Cyclophosphazenes with P-CAR Bonds for Supramolecular Chemistry

Abstract

We describe the synthesis of new cyclotritphosphazenes in which the phosphorus substituents are either free-rotating or rigid planar heterocyclic groups, through phosphorus-carbon bonds.