Concentrated solar radiation-assisted one-pot/multicomponent synthesis of pyranopyrazole derivatives under neat condition

Research on Chemical Intermediates - Concentrated solar radiation (CSR)-assisted synthesis of pyranopyrazole derivatives under solvent and catalyst-free condition has been reported in the present...     

The effects of sample preparation methods on the variability of the electrospray ionization response for model drug compounds

A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd.     

Phase formation and crystallization in Bi-Sr-Ca-Cu-O thick films

Thick films of Bi₂Sr₂CaCu₂O_x superconducting at 84 K have been prepared on polycrystalline MgO substrates. The effect of heat treatment on phases formed at various stages of the film preparation is studied. Investigations show that a thin layer at the top is highly oriented while the bulk of the 212 phase material beneath it consists of randomly oriented grains. This appears to be the main reason for the low critical current densities obtained in practice.     

α-Particle induced reactions on rhodium

Excitation functions for¹⁰³Rh (α,xn);x = 1–4 and¹⁰³Rh (α,αxn);x = 1–3 reactions were measured up to 50 MeV bombarding energy using stacked foil activation technique and high purity germanium (HPGe) γ-ray spectroscopy method. The experimental results were compared with calculations considering equilibrium as well as pre-equilibrium hybrid model of Blann (ALICE/90). It is found that the initial exciton configurationn ₀ = 4(4p0h) gives fairly good agreements for (α,xn) reactions. There seems to be indication of direct inelastic scattering effects in (α,αxn)-type of reactions.     

Magnetic properties of rare earth ion (Sm) added nanocrystalline Mg-Cd ferrites, prepared by oxalate co-precipitation method

Nanocrystalline ferrite powder having the general formula Mg_1−xCd_xFe₂O₄+5% Sm³⁺ (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by chemical oxalate co-precipitation technique. The synthesized powder was characterized by X-ray, IR and SEM techniques. The XRD analysis confirms cubic spinel phase with orthoferrite secondary phase. The lattice constant increases with increase in Cd²⁺ content (x). It is smaller than that for pure Mg-Cd ferrites. The average crystallite size lies in the range 28.69-32.66 nm. Saturation magnetization and magnetic moment increase with cadmium content up to x=0.4 and decrease thereafter. This is attributed to the existence of localized canted spin. The decrease in saturation magnetization and magnetic moment beyond x=0.4 is due to the presence of triangular spin arrangement on B-site. Coercivity and remanent magnetization decrease while Y-K angles increase with Cd²⁺ content. The Sm³⁺ addition improves the magnetic properties.     

On the preparation and the characterization of superconducting thin films of YBa2Cu3O7−x

The results of our initial efforts to deposit thin films of YBa₂Cu₃O_7−x system on sapphire substrate are described. The deposited films are shiny black in appearance and are of quite uniform chemical composition. The annealed films exhibit zero resistance superconducting transition temperatureT _c(R=0) ranging between 23 K and 30 K.     

Improvement of the scintillation properties of Gd3Ga3Al2O12:Ce,B single crystals having tailored defect structure

A novel approach is reported to minimize various defect centers in Ce doped Gd₃Ga₃Al₂O₁₂ single crystals to improve the scintillation properties. The crystals of Gd₃Ga₃Al₂O₁₂ codoped with 0.2 at% Ce and B (GGAG:Ce,B) have been grown in air and argon ambient using the Czochralski technique. The scintillation light output of crystals grown in Ar ambient was significantly increased after annealing the crystals in air. The measured light output of 60000 ph/MeV for annealed crystals is the highest value reported among this class of materials. As a consequence, the energy resolution at 662 keV gamma‐rays from a ¹³⁷Cs source was improved from 8% for the crystals grown in air to 6% for crystals grown in Ar and subsequently annealed in air. Further, the thermal quenching energy of photoluminescence (PL) emission was increased to be 470 meV for the annealed crystals. The thermoluminescence (TL) measurements suggest that the crystals grown in Ar ambient and post‐growth annealed in air may have a lesser concentration of trap centers which subsequently lead to the improvement in optical and scintillation properties leading to a superior detector performance. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

关于单位园周上阶梯函数的性质

Ｔ．Ｓｈｅｉｌ－Ｓｍａｌｌ［１］讨论了阶梯函数的Ｆｏｕｒｉｅｒ级数。本文对［１］中所涉及到一些阶梯函数的性质进行了详细讨论，并给出了详细证明。     

Luminescence properties of Eu3+ doped CaMoO4 nanoparticles

When Eu(3+) ions occupy Ca(2+) sites of CaMoO(4), which has a body centered tetragonal structure with inversion symmetry, only the magnetic dipole transition ((5)D(0)→(7)F(1)) should be allowed according to Judd-Ofelt theory. Even if there are a few distortions in the Eu(3+) environment, its intensity should be more than that of the electric dipole transition ((5)D(0)→(7)F(2)). We report here the opposite effect experimentally and ascribe this to the polarizability effect of the MoO(4) tetrahedron, which is neighboring to EuO(8) (symmetric environment). The contribution of the energy transfer process from the Mo-O charge transfer band to Eu(3+) and the role of Eu(3+) over the surface of the particle could be distinguished when luminescence decay processes were measured at two different excitations (250 and 398 nm). Further, the luminescence intensities and lifetimes increase significantly with increasing heat-treatment temperature of the doped samples. This is attributed to the reduction of H(2)O from the surface of the particles and a non-radiative process after heat treatment.