Synthesis,structural, dielectric and magnetic properties of spinel structure of Ca2+ substitute in Cobalt ferrites (Co1−xCaxFe2O4)

Non magnetic material Ca²⁺ as a substitute in Cobalt ferrite (Co_1?xCa_xFe₂O₄x?=?0.00, 0.05, 0.10 & 0.15) is prepared by self auto combustion method. The synthesized samples were carried out for various characterizations such as X-ray diffraction, Field emission scanning electron microscope (FE-SEM), Dielectric measurement and Magnetic property. X-ray diffraction reveals the values of crystalline size, lattice parameter and x-ray density by using the standard formula. The saturation magnetization (M_s) decreases from 63.92 to 43.17 emu/g for x?=?0.00 to 0.15 and the coercivity (H_c) increases gradually from 819.85 to 1312.32?Oe with the increase in Ca²⁺ concentration. The dielectric properties of synthesized nano materials were carried out at room temperature. The dielectric parameters such as tangent loss, Cole–Cole plot (Impedance, Modulus), and AC Conductivity were determined for various Ca²⁺ concentration. The frequency dependent dielectric dispersion behaviour of all the samples can be explained by the Maxwell–Wagner two-layer model along with Koop's phenomenological theory. As a result, Ca²⁺ substituted Cobalt ferrite is enhanced with their dielectric and magnetic property which is suitable for a memory device, recording media application and high frequency device.     

Preliminary results of the cross-section measurement of e<Superscript>+</Superscript>e<Superscript>−</Superscript> → φ(1020)η process with the CMD-3 detector at VEPP-2000 collider

We report preliminary results on the cross section of the process e⁺e^? → φ(1020)η measured at 30 center-of-mass energy points in the range from 1.59 up to 2.0 GeV. Data analysis is based on the integrated luminosity of 22 pb^?1 collected with the CMD-3 detector in 2011–2012. The obtained cross section agrees with the BaBar measurement and has better statistical accuracy.     

Strain-induced interaction of interstitials in IVA group hcp metals

Strain-induced (elastic) interactions of oxygen, nitrogen and carbon atoms in IVA group metals, α-Ti, Zr, and -Hf, are calculated in the framework of the microscopic Krivoglaz-Kanzaki-Khachaturyan theory. The experimental elastic constants, lattice spacing of the host metal, and concentration expansion coefficients are used as the input numerical parameters. The resulting interactions are stronger in α-Ti than in α-Zr and α-Hf. A comparative analysis of interactions in the hcp IVA group metals with those in bcc and fcc solid solutions reveals the crystal structure effect. In general, the strain-induced interactions of O, N, and C in hcp IVA group metals are weaker than in bcc solid solutions and are stronger than in fcc solid solutions.     

Application of the Monte Carlo method to the problem of surface segregation simulation

A generalization of the Monte Carlo method to the case of grand canonical ensemble allowing the elimination of the problem of determination of the chemical potential of alloy components was proposed. The method is particularly convenient for the calculations of surface segregations because it excludes time-consuming calculation of the temperature-dependent bulk chemical potential μ(T). The new method was used for calculating segregations at the (100), (110), and (111) surfaces of the Ni₅₀Pd₅₀ alloy using the Ising model with ab initio effective interatomic interaction potentials.     

Synthesis and structure of [2-oxo(thioxo)tetrahydropyrimidin-4-yl]calix[4]arenes

Cone-shaped di- and tetrapropoxycalix[4]arenes functionalized at the upper rim with one or two 2-oxo(thioxo)tetrahydropyrimidine residues were synthesized by the Biginelli reaction of formylcalixarenes with urea (thiourea) and methyl acetoacetate. The steric structure of the products was studied by NMR and X-ray diffraction. The Biginelli reaction with dipropoxyformylcalixarene was diastereoselective, and it quantitatively produced the corresponding meso form. Tetrapropoxydiformylcalixarenes under analogous conditions gave rise to equimolar mixtures of racemic and meso compounds. The macrocyclic skeleton of the synthesized pyrimidine-containing calixarenes in crystal and in solution has a flattened cone conformation. (5-Methoxycarbonyl-2-oxotetrahydropyrimidin-4-yl)calixarene molecules in crystal undergo self-organization to form infinite chains via repeated inclusion of the methoxy group into the cavity of the neighboring macrocycle. Selforganization of bis(5-methoxycarbonyl-2-oxotetrahydropyrimidin-4-yl)calixarene with formation of analogous chains involves intermolecular hydrogen bonding NH ... O=C.     

Discrete Vortices in Systems of Coupled Nonlinear Oscillators: Numerical Results for an Electric Model

JETP Letters - Vortex coherent structures on arrays of nonlinear oscillators joined by weak links into topologically nontrivial two-dimensional discrete manifolds have been theoretically studied. A...     

Magnetic and dielectric response of M-type barium hexaferrite

Barium hexaferrite (BaFe₁₂O₁₉) is a promising candidate for ceramics, microwave devices and numerous applications. Barium hexaferrite was synthesised via the sol-gel auto-combustion technique using glycine fuel. The X-ray diffraction technique confirmed the hexagonal structure of the particles with space group P63/mmc. The morphological analysis was performed using the field-emission scanning microscope, and the images displayed the plate-like particle formation. Transmission electron microscopy was employed to determine the average particle size of the sample, which was estimated to be 155.93 nm. The magnetic studies were taken through the vibrating sample magnetometer (VSM) at 300 K, with which the saturation magnetization (M_s), coercivity (H_c), squareness ratio (M_r/M_s), and energy product (BH_max) was calculated, and the particles were validated to be in single domain arrangement. The dielectric properties were investigated through the LCR meter. Koop and Maxwell-Wagner's model was used to interpret charge conduction and the occurrence of relaxations in the system.     

Extended molecular connectivity: Prediction of boiling points of alkanes

It is shown that extended molecular connectivity may be used for “structure-property” studies. The statistical parameters of the correlation relations of boiling points with extended molecular connectivity indices found for a sample of alkanes (n = 74) are the following: the best two-parameter correlation r = 0.9948, s = 4.7; the best three-parameter correlation r = 0.9971, s = 3.5. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1154–1159, November–December, 1997.     

TEMPERATURE DEPENDENCE OF CHLOROPHYLL FLUORESCENCE FROM THE LIGHT HARVESTING COMPLEX II OF HIGHER PLANTS

Abstract— Chlorophyll fluorescence spectra of LCHII, the light harvesting complex of photosystem II, have been recorded in the aggregated and trimeric forms for a range of temperatures from 293 to 4 K. At least five long-wavelength emitters in the 682–702 nm region with different temperature dependencies were found in the spectra of the aggregates. At 293 K the yield of LCHII trimers was higher than aggregates by a factor of 4, but, upon lowering the temperature, a fluorescence rise was observed which was much stronger for LCHII aggregates than for LCHII trimers, so that at 4 K their yields were comparable. The implications of these data in terms of the function of LCHII are discussed.