Effect of different concentrations of sulfuric acid on leaching of radionuclide isotopes in sedimentary rock samples,Sinai, Egypt

Journal of Radioanalytical and Nuclear Chemistry - This research focused on studying the effect of sulfuric acid concentrations on the leaching of different radionuclides (238U and 235U series) in...     

Influence of yttrium doping on the photocatalytic activity of bismuth oxybromide for ciprofloxacin degradation using indoor fluorescent light illumination

Research on Chemical Intermediates - In this work, a series of Y-doped BiOBr photocatalysts with different yttrium contents were successfully synthesized through a facile ethylene glycol-assisted...     

SPEEK-zirconium hydrogen phosphate composite membranes with low methanol permeability prepared by electro-migration and in situ precipitation

Sulfonated poly(ether ether ketone) (SPK)-zirconium hydrogen phosphate (ZrP) composite membranes were prepared by electro-driven migration of Zr(4+) and simultaneous in situ precipitation of ZrP using phosphoric acid under different electrical gradient, in order to avoid loss in its mechanical stability. Degree of sulfonation was estimated from (1)H NMR and ion-exchange capacity study that was found to be 61% and 57%, respectively. In this method Zr(4+) and HPO(4)(2-) were allowed to diffuse within the pores/channels of the preformed SPK membrane under given electrical gradient and ZrP was precipitated within the membrane matrix. ZrP loading density was measured as a function of applied electrical gradient for a definite reaction time (4 h) and electrolytic environment. Membranes with varied ZrP loading densities were characterized for their thermal and mechanical stabilities, physicochemical and electrochemical properties using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), water content, proton conductivity and methanol permeability. No loss in thermal and mechanical stability of membranes was observed due to incorporation of inorganic component (ZrP) in the membrane matrix. Although the composite membranes exhibited low proton conductivity in comparison to SPK membrane at room temperature, but the presence of the inorganic particles led to an improvement in high temperature conductivity. Selectivity parameter of these composite membranes was estimated at two temperatures namely 30 and 70 degrees C, in latter case it was found significantly higher than that for Nafion membrane (0.79 x 10(5) S s cm(-3)) under similar experimental conditions.     

Effective one-dimensional equation of motion for nuclear fission

An approach for describing the dynamics of nuclear fission in the framework of generalized quantum mechanics is discussed. The collective kinetic energy is assumed to be two dimensional, and the reduced mass is allowed to vary with the coordinates. The generalized calculus of variation is employed for minimizing the action after being properly quantized as required by Hamilton's principle, employing a curvilinear coordinate system. The corresponding Euler Lagrange equation is identified as the required generalized equation of motion. The proposed generalized two-dimensional equation of motion is separated into a vibrational eigenvalue equation and a set of coupled-channel one-dimensional equations which describe the translational motion, by exploiting the completeness of the vibrational eigenfunctions. Such a system of coupled equations can be decoupled by replacing the coupling matrix elements by a nonlocal interaction, which can be rendered local after employing the effective mass approximation. As a consequence this differential equation is provided with an effective mass, an effective potential barrier, and a differential boundary term which is responsible for restoring the self-adjointness of the kinetic energy differential operator.     

Hollow spherical supramolecular dendrimers

The synthesis of a library containing 12 conical dendrons that self-assemble into hollow spherical supramolecular dendrimers is reported. The design principles for this library were accessed by development of a method that allows the identification of hollow spheres, followed by structural and retrostructural analysis of their Pm3n cubic lattice. The first hollow spherical supramolecular dendrimer was made by replacing the tapered dendron, from the previously reported tapered dendritic dipeptide that self-assembled into helical pores, with its constitutional isomeric conical dendron. This strategy generated a conical dendritic dipeptide that self-assembled into a hollow spherical supramolecular dendrimer that self-organizes in a Pm3n cubic lattice. Other examples of hollow spheres were assembled from conical dendrons without a dipeptide at their apex. These are conical dendrons originated from tapered dendrons containing additional benzyl ether groups at their apex. The inner part of the hollow sphere assembled from the dipeptide resembles the path of a spherical helix or loxodrome and, therefore, is chiral. The spheres assembled from other conical dendrons are nonhelical, even when they contain stereocenters on the alkyl groups from their periphery. Functionalization of the apex of the conical dendrons with diethylene glycol allowed the encapsulation of LiOTf and RbOTf in the center of the hollow sphere. These experiments showed that hollow spheres function as supramolecular dendritic capsules and therefore are expected to display functions complementary to those of other related molecular and supramolecular structures.     

He++N2 Charge Transfer Reaction: An Ab initio Analysis

An ab initio analysis on the involved potential energy surfaces is presented for the investigation of the charge transfer mechanism for the He⁺+N₂ system. At high collision energy, as many as seven low-lying electronic states are observed to be involved in the charge transfer mechanism. Potential energy surfaces for these low-lying electronic states have been computed in the Jacobi scattering coordinates, applying multireference configuration interaction level of theory and aug-cc-pVQZ basis sets. Asymptotes for the ground and various excited states are assigned to mark the entrance (He⁺+N₂) and charge transfer channels (He+N₂⁺). Nonadiabatic coupling matrix elements and quasi-diabatic potential energy surfaces have been computed for all seven states to rationalize the available experimental data on the charge transfer processes and to facilitate dynamics studies.     

The restricted active space followed by second-order perturbation theory method: theory and application to the study of CuO2 and Cu2O2 systems

A multireference second-order perturbation theory using a restricted active space self-consistent field wave function as reference (RASPT2/RASSCF) is described. This model is particularly effective for cases where a chemical system requires a balanced orbital active space that is too large to be addressed by the complete active space self-consistent field model with or without second-order perturbation theory (CASPT2 or CASSCF, respectively). Rather than permitting all possible electronic configurations of the electrons in the active space to appear in the reference wave function, certain orbitals are sequestered into two subspaces that permit a maximum number of occupations or holes, respectively, in any given configuration, thereby reducing the total number of possible configurations. Subsequent second-order perturbation theory captures additional dynamical correlation effects. Applications of the theory to the electronic structure of complexes involved in the activation of molecular oxygen by mono- and binuclear copper complexes are presented. In the mononuclear case, RASPT2 and CASPT2 provide very similar results. In the binuclear cases, however, only RASPT2 proves quantitatively useful, owing to the very large size of the necessary active space.     

Relativistic symmetry of position-dependent mass particles in a Coulomb field including tensor interaction

The spatially-dependent mass Dirac equation is solved exactly for attractive scalar and repulsive vector Coulomb potentials,including a tensor interaction under the spin and pseudospin symmetric limits.Closed forms of the energy eigenvalue equation and wave functions are obtained for arbitrary spin-orbit quantum number κ.Some numerical results are also given,and the effect of tensor interaction on the bound states is presented.It is shown that tensor interaction removes the degeneracy between two states in the spin doublets.We also investigate the effects of the spatially-dependent mass on the bound states under spin symmetric limit conditions in the absence of tensor interaction.     

Comparative studies on performance of radiation-induced and thermal cross-linked ion-exchange membrane for water electrolysis

Radiation-induced and thermal cross-linked sulfonated poly(ether sulfone) (SPS)–sulfonated poly(ether ether ketone) (SPK) composite ion-exchange membranes (SPS/SPK(γ) and SPS/SPK(T), respectively) were prepared. Their performances for water electrolysis were comparatively assessed. Thermal cross-linked membrane (SPS/SPK(T)) showed cross-linking of part functional groups (–SO₃H) and thus deterioration in membrane conductivity. While, radiation-induced cross-linked membrane (SPS/SPK(γ)) avoided any cross-linking between functional groups and thus conductivity. Electrolysis performances of these membranes were evaluated in comparison with Nafion117 membrane. Relatively low current efficiency (CE) for SPS/SPK and SPS/SPK(T) membranes was due to their high mass transfer (water) via electro-osmotic drag, which was negligible for SPS/SPK(γ) membrane. SPS/SPK(γ) membrane exhibited comparable stabilities and water splitting performance with Nafion117 membrane, which revealed its suitability as substitute for electrochemical applications.     

Synthesis,characterization and hydrogen sorption studies of mixed sodium‐potassium alanate

The aim of the present investigation is to synthesize mixed sodium potassium alanate (K₂NaAlH₆) and to explore its hydrogen sorption characteristics. K₂NaAlH₆ is synthesized through ball milling of KH and NaAlH₄ in the molar ratio 2:1 under hydrogen pressure of 10 bar. The temperature programmed desorption experiment shows that the synthesized K₂NaAlH₆ has peak desorption temperature of ∼352°C and reveals appreciable rehydrogenation kinetics under 6 bar hydrogen pressure at 300°C. The investigations are also focused on the catalytic effect of carbon nanostructures (CNS) namely, the graphene sheet (GS) and single wall carbon nanotube (SWCNT) and titanium halides (TiCl₃ and TiF₃) on K₂NaAlH₆. In the case of graphene and SWCNT catalyzed K₂NaAlH₆, the peak desorption temperature gets reduced to ∼347°C and ∼341°C respectively. The catalytic effects of CNS and titanium halide on K₂NaAlH₆ are also compared in the investigation. Between the two types of catalysts, halides are found to be better than CNS and out of the two halides, TiF₃ is found to be the best catalyst for hydrogen sorption in K₂NaAlH₆. The peak desorption temperature decreases significantly from 352°C to ∼324°C for TiF₃ catalyzed K₂NaAlH₆. Thus, the desorption activation energy reduces drastically from 124.43 kJ/mol (synthesized K₂NaAlH₆) to 88.05 kJ/mol for TiF₃ catalyzed K₂NaAlH₆.