Synthesis And Characterization Of Two New Antimony Phosphates Co0,5alsb(PO4)3 And Mg0,5fesb(PO4)3

Two new antimony phosphates Co0,5AlSb(PO4)3 and Mg0,5FeSb(PO4)3 were synthesized for the first time by the solid-state reaction method. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Co0,5AlSb(PO4)3 crystallizes in the space group R-3c (N°167) (ah = 8.23±0.01Ǻ, ch = 21.94±0.02Ǻ). Mg0,5FeSb(PO4)3 crystallizes in the monoclinic space group P21/n (N°14) (am =11.54 Ǻ, bm = 8.83± 0.02 Ǻ, cm = 8.39± 0.01 Ǻ, β = 96.67°± 0.09). Raman and infrared spectra were recorded and assignments of the stretching and bending vibrations of the PO43- tetrahedra were made. The number of the peaks observed is in good agreement with that predicted by the factor group analysis of the R-3c et P21/n space group respectively. Vibrational spectral studies of two antimony phosphates were collected in-situ at room-pressure and at elevated temperatures, up to 430 oC. At elevated temperatures in air, Mg0,5FeSb(PO4)3 seems to be stable, but Co0,5AlSb(PO4)3 show a transition at 380°C and decomposes at 930°C. This result has been confirmed by differential scanning calorimetric study (DSC).Two new antimony phosphates Co0,5AlSb(PO4)3 and Mg0,5FeSb(PO4)3 were synthesized for the first time by the solid-state reaction method. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Co0,5AlSb(PO4)3 crystallizes in the space group R-3c (N°167) (ah = 8.23±0.01Ǻ, ch = 21.94±0.02Ǻ). Mg0,5FeSb(PO4)3 crystallizes in the monoclinic space group P21/n (N°14) (am =11.54 Ǻ, bm = 8.83± 0.02 Ǻ, cm = 8.39± 0.01 Ǻ, β = 96.67°± 0.09). Raman and infrared spectra were recorded and assignments of the stretching and bending vibrations of the PO43- tetrahedra were made. The number of the peaks observed is in good agreement with that predicted by the factor group analysis of the R-3c et P21/n space group respectively. Vibrational spectral studies of two antimony phosphates were collected in-situ at room-pressure and at elevated temperatures, up to 430 oC. At elevated temperatures in air, Mg0,5FeSb(PO4)3 seems to be stable, but Co0,5AlSb(PO4)3 show a transition at 380°C and decomposes at 930°C. This result has been confirmed by differential scanning calorimetric study (DSC)

Ground State Study of a Double Core-Shell Dendrimer Nanostructure

Based on a dendrimer graph theory, we investigate the ground state phase diagrams of a nanostructure formed by three spin types

A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

A high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532~nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064~nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO$_{3}$ crystal. The maximum achieved green power at 5 W IR pump power is 1.74 W with a total conversion efficiency of 34.8\%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7~kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7\%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0\% precision in polarization measurements of an electron beam with energy and current of 1.0~GeV and 50~$\mu$A.Comment: 20 pages, 22 figures, revised version of arXiv:1601.00251v1, submitted to NIM

The effect of cation disorder on magnetic properties of new double perovskites La2NixCo1-xMnO6 (x = 0.2 - 0.8)

Solid solutions of new double perovskite oxides La2NixCo1-xMnO6 (x = 0.2, 0.25, 0.5, 0.75, 0.8) were synthesized by solid-state reaction method. The X-ray powder diffraction data show that all the compounds crystallize in the monoclinic structure with space group P21/n at room temperature. The elementary composition of the powders was determined by the electron Probe Microanalysis. Raman and IR spectra show strong bands at (520, 650 cm?1) and (426, 600 cm?1) respectively, attributed to the stretching vibration of Ni/Co-O and Mn-O bonds in the structure. The magnetic studies for all the compounds have been performed in both DC and AC magnetic fields in the temperature range from 2 to 300 K. All samples exhibit a main paramagnetic to ferromagnetic (PM-FM) transition between 232 K and 260 K, and their Curie temperature increases rapidly with increasing x values. Three samples with x = 0.2, 0.25 and 0.5 respectively display also a secondary PM-FM transition between 200 K and 208 K. The thermal variation of out of phase component of AC susceptibility presents also frequency-dependent transitions between 65 K and 110 K unfolding the existence of super-paramagnetic mono-domains in all samples. The band gap energy has been calculated and revealing semiconductor behavior for all samples

Precision measurements of A(1)(n) in the deep inelastic regime

We have performed precision measurements of the double-spin virtual-photon asymmetry A(1) on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized He-3 target. Our data cover a wide kinematic range 0.277 \u3c = x \u3c = 0.548 at an average Q(2) value of 3.078(GeV/c)(2), doubling the available high-precision neutron data in this xrange. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with a previous observation of an A(1)(n) zero crossing near x = 0.5. We find no evidence of a transition to a positive slope in (Delta d + Delta(d) over bar)/(d + (d) over bar) up to x = 0.548. (C) 2015 The Authors. Published by Elsevier B.V

Precision Measurement of the Neutron Twist-3 Matrix Element d(2)(n): Probing Color Forces

Double-spin asymmetries and absolute cross sections were measured at large Bjorken x (0.25 ≤ x ≤ 0.90), in both the deep-inelastic and resonance regions, by scattering longitudinally polarized electrons at beam energies of 4.7 and 5.9 GeV from a transversely and longitudinally polarized 3He target. In this dedicated experiment, the spin structure function g(2)(3He) was determined with precision at large x, and the neutron twist-3 matrix element d(2)(n) was measured at \u3c Q2\u3e of 3.21 and 4.32 GeV2/c2, with an absolute precision of about 10-5. Our results are found to be in agreement with lattice QCD calculations and resolve the disagreement found with previous data at \u3c Q2\u3e = 5 GeV2/c2. Combining d(2)(n) and a newly extracted twist-4 matrix element f(2)(n), the average neutron color electric and magnetic forces were extracted and found to be of opposite sign and about 30 MeV/fm in magnitude

Learning of chemistry of solution with help of computer simulation

Le présent article rend compte d'une expérimentation utilisant des simulations informatiques de titrages acide-base dans des situations didactiques d'apprentissage basées sur l'investigation et la participation de l'apprenant dans la construction de son savoir. Deux approches dans l'utilisation des simulations de titrages pH-métriques à l'aide du logiciel «SIMULTI2» sont mises en place et évaluées avec un groupe d'enseignants en formation continue et un groupe d'élèves-professeurs en formation initiale. On montre que les simulations informatiques créent un contexte pédagogique favorisant l'apprentissage par la découverte ou l'exploration basée sur les conflits cognitifs

Test of the CLAS12 RICH large scale prototype in the direct proximity focusing configuration

A large area ring-imaging Cherenkov detector has been designed to provide clean hadron identification capability in the momentum range from 3 GeV/c up to 8 GeV/c for the CLAS12 experiments at the upgraded 12 GeV continuous electron beam accelerator facility of Jefferson Laboratory. The adopted solution foresees a novel hybrid optics design based on aerogel radiator, composite mirrors and high-packed and high-segmented photon detectors. Cherenkov light will either be imaged directly (forward tracks) or after two mirror reflections (large angle tracks). We report here the results of the tests of a large scale prototype of the RICH detector performed with the hadron beam of the CERN T9 experimental hall for the direct detection configuration. The tests demonstrated that the proposed design provides the required pion-to-kaon rejection factor of 1:500 in the whole momentum range.Comment: 15 pages, 23 figures, to appear on EPJ