A new calculational method adapted to the experimental conditions for determining thorium and uranium contents in geological samples

The thorium to uranium ratio has been determined in different geological samples by using a new theoretical method based on calculating the probability for an emitted -particle to reach and be registered on a solid state nuclear track detector (SSNTD). Thorium as well as uranium contents of the samples studied have been determined by exploiting the track densities, due to the -particles of the thorium and uranium series, registered on the CR-39 and LR-115 SSNTD. Results obtained by this calculational method which does not need any calibration were compared to data obtained by isotope dilution mass spectrometry. The influence of the granulation on the uranium content in sedimentary phosphate samples has also been investigated.     

Effect of calcination temperature on the structure of vanadium phosphorus oxide materials and their catalytic activity in the decomposition of 2-propanol

The synthesis of vanadyl phosphate by reaction of an alcoholic solution of V₂O₅ and o-H₃PO₄ has been studied. The solids obtained were investigated by various physico-chemical techniques as in situ X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) under inert atmosphere. The compounds have been further characterized by infrared and UV–Visible spectroscopies. The isopropanol conversion is carried out to evaluate the catalytic activity of the samples. The isopropanol conversion increases with the reaction temperature from 433 to 503 K for vanadyl phosphorus oxides calcined at a different temperature. However, the conversion attains 100% at 503 K, and the solid calcined at 973 K exhibits high selectivity towards propene (100% at 503 K).     

The magnetic entropy change in the double perovskite La2NiMnO6 with strong spin–phonon coupling

The magnetocaloric effect and the critical behavior of La₂NiMnO₆ are investigated by measurement of the magnetization around $T_C$. The magnetic entropy change $\left|\Delta S\right|$ of La₂NiMnO₆ for a field change of 0–45 kOe near the Curie temperature is about 5% of the theoretical expectation. The critical behavior of the La₂NiMnO₆ deviates from the mean field theory. These abnormal phenomena are understood in the context of the strong spin–phonon coupling in La₂NiMnO₆. It is suggested that a method of modulating this coupling would enhance the magnetic entropy change greatly, which makes the La₂NiMnO₆ a promising candidate for room-temperature magnetic refrigeration.     

Controllable Goos-Hänchen shift in graphene triangular double barrier

We study the Goos-Hänchen (GH) shifts for Dirac fermions in graphene scattered by a triangular double barrier potential. The massless Dirac-like equation was used to describe the scattered fermions by such potential configuration. Our results show that the GH shifts is affected by the geometrical structure of the double barrier. In particular the GH shifts change sign at the transmission zero energies and exhibit enhanced peaks at each bound state associated with the double barrier when the incident angle is less than the critical angle associated with total reflection.     

Microbial Reduction of Lepidocrocite γ-FeOOH by Shewanella putrefaciens; The Formation of Green Rust

Dissimilatory iron-reducing bacteria (DIRB) couple the oxidation of organic matter or H₂ to the reduction of iron oxides. The bacterial reduction of a most common well-crystallised ferric oxyhydroxide, -FeOOH was investigated using DIRB Shewanella putrefaciens, strain CIP 8040. Experiments were conducted in the presence of neither organic buffer nor phosphate, with formate as electron donor, bicarbonate, and anthraquinone-2,6-disulfonate (AQDS, a humic acid analogue) that influenced the extent of ferric oxide bioreduction. The production of Fe²⁺ was followed with time. The solid phases obtained after bacterial iron reduction were analysed by transmission Mössbauer spectroscopy (TMS) and X-ray diffraction (XRD). Biogenic formation of green rust 1 compound, which contains carbonate anions, [Fe^II ₂Fe^III ₂(OH)₈]²⁺[CO₃ ^2–]^2– was observed. TMS was used to follow the evolution of the green rust abundance during the bacterial culture.     

Extended Weyl-Heisenberg algebra, phase operator, unitary depolarizers and generalized Bell states

Finite dimensional representations of extended Weyl-Heisenberg algebra are studied both from mathematical and applied viewpoints. They are used to define unitary phase operator and the corresponding eigenstates (phase states). It is also shown that the unitary depolarizers can be constructed in a general setting in terms of phase operators. Generation of generalized Bell states using the phase operator is presented and their expressions in terms of the elements of mutually unbiased bases are given.     

Electrical relaxation studies of olivine type nanocrystalline LiMPO4 (M=Ni,Mn and Co) materials

The olivine type LiMPO₄ (M=Ni, Mn and Co) materials were synthesized by solution combustion technique using glycine as fuel. The structural characterizations were explored to confirm the phase formation of materials. The scanning electron microscope was used to identify the morphology of olivine materials. The local structure and chemical bonding between MO₆ octahedral and (PO₄)^3- tetrahedral groups were probed by Raman spectroscopy. Grain and grain boundaries were contributed for ion relaxation and dc conduction in olivine materials. Two orders of enhancement in ionic conductivity was observed in these olivine materials than the reported value. Among all the explored olivine samples, LiMnPO₄ showed highest enhancement in conductivity due to weak Li–O bonding and largest unit cell volume.