1,171 research outputs found
A family of charged compact objects with anisotropic pressure
Utilizing an ansatz developed by Maurya and co-workers we present a class of
exact solutions of the Einstein-Maxwell field equations describing a
spherically symmetric compact object. A detailed physical analysis of these
solutions in terms of stability, compactness and regularity indicate that these
solutions may be used to model strange star candidates. In particular, we model
the strange star candidate Her X-1 and show that our solution conforms to
observational data to an excellent degree of accuracy. An interesting and novel
phenomenon which arises in this model is the fact that the relative difference
between the electromagnetic force and the force due to pressure anisotropy
changes sign within the stellar interior. This may be a an additional mechanism
required for stability against cracking of the stellar object
Effect of Thermal Annealing on Boron Diffusion, Micro-structural, Electrical and Magnetic properties of Laser Ablated CoFeB Thin Films
We report on Boron diffusion and subsequent crystallization of
CoFeB (CoFeB) thin films on SiO/Si(001) substrate
using pulsed laser deposition. Secondary ion mass spectroscopy reveals Boron
diffusion at the interface in both amorphous and crystalline phase of CoFeB.
High-resolution transmission electron microscopy reveals a small fraction of
nano-crystallites embedded in the amorphous matrix of CoFeB. However, annealing
at 400C results in crystallization of CoFe with \textit{bcc} structure
along (110) orientation. As-deposited films are non-metallic in nature with the
coercivity (H) of 5Oe while the films annealed at 400C are metallic
with a H of 135Oe.Comment: 16 pages, 6 figure
Effect of Multiple Stresses (Thermal, Nutritional, and Walking Stress) on the Reproductive Performance of Malpura Ewes
A study was conducted to assess the effect of multiple stresses (thermal, nutritional, and walking stress) on the reproductive performance of Malpura ewes. The study was conducted for a period of 35 days covering two estrous cycles during summer season (April-May). The ewes were randomly allocated into two groups of twelve animals each namely, GI (n=12; Control), and GII (n=1 2; Multiple stresses). GI ewes were maintained in the shed, while GII ewes were subjected to multiple stresses (thermal, nutritional, and walking stress). The estrus % differed significantly (P< 0.05) between the groups. Estrus duration also showed similar trend to that of estrus %. Both conception and lambing rate also differed significantly (P< 0.05) between the control and multiple-stress group. In addition plasma estradiol and progesterone also showed significant difference between the groups. The study proved the detrimental effects of multiple-stresses on various reproductive parameters studied. Hence it is very pertinent to conclude that when two or more than two stressors occur simultaneously, the total impact may be severe on reproductive functions of the animals
Tetramer Orbital-Ordering induced Lattice-Chirality in Ferrimagnetic, Polar MnTi2O4
Using density-functional theory calculations and experimental investigations
on structural, magnetic and dielectric properties, we have elucidated a unique
tetragonal ground state for MnTi2O4, a Ti^{3+} (3d^1)-ion containing
spinel-oxide. With lowering of temperature around 164 K, cubic MnTi2O4
undergoes a structural transition into a polar P4_1 tetragonal structure and at
further lower temperatures, around 45 K, the system undergoes a paramagnetic to
ferrimagnetic transition. Magnetic superexchange interactions involving Mn and
Ti spins and minimization of strain energy associated with co-operative
Jahn-Teller distortions plays a critical role in stabilization of the unique
tetramer-orbital ordered ground state which further gives rise to lattice
chirality through subtle Ti-Ti bond-length modulations
Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target
Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500-750 degrees C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 degrees C to 600 degrees C and the value further decreased with increase of growth temperature up to 720 degrees C. A highly c-axis oriented GaN epitaxial film was obtained at 720 degrees C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 degrees C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 degrees C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE
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