3,709 research outputs found
Warm and dense stellar matter under strong magnetic fields
We investigate the effects of strong magnetic fields on the equation of state
of warm stellar matter as it may occur in a protoneutron star. Both neutrino
free and neutrino trapped matter at a fixed entropy per baryon are analyzed. A
relativistic mean field nuclear model, including the possibility of hyperon
formation, is considered. A density dependent magnetic field with the magnitude
G at the surface and not more than G at the center
is considered. The magnetic field gives rise to a neutrino suppression, mainly
at low densities, in matter with trapped neutrinos. It is shown that an hybrid
protoneutron star will not evolve to a low mass blackhole if the magnetic field
is strong enough and the magnetic field does not decay. However, the decay of
the magnetic field after cooling may give rise to the formation of a low mass
blackhole.Comment: 17 pages, 10 figures, 3 tables, submitted to Phys. Rev.
Probing the superconducting ground state of ZrIrSi: A SR study
The superconducting ground state of newly reported ZrIrSi is probed by means
of SR technique along with resistivity measurement. The occurrence of
superconductivity at = 1.7 K is confirmed by resistivity
measurement. ZF-SR study revealed that below , there is no
spontaneous magnetic field in the superconducting state, indicates TRS is
preserved in case of ZrIrSi. From TF-SR measurement, we have estimated the
superfluid density as a function of temperature, which is described by an
isotropic wave model with a superconducting gap
= 5.1, indicates the presence of strong
spin-orbit coupling. {\it Ab-initio} electronic structure calculation indicates
that there are four bands passing through the Fermi level, forming four Fermi
surface pockets. We find that the low-energy bands are dominated by the
-orbitals of transition metal Zr, with substantially lesser weight from the
-orbitals of the Ir-atoms.Comment: 6 pages, 4 figure
Investigation of Superconducting Gap Structure in HfIrSi using muon spin relaxation/rotation
Appearance of strong spin-orbit coupling (SOC) is apparent in ternary
equiatomic compounds with 5-electrons due to the large atomic radii of
transition metals. SOC plays a significant role in the emergence of
unconventional superconductivity. Here we examined the superconducting state of
HfIrSi using magnetization, specific heat, zero and transverse-field (ZF/TF)
muon spin relaxation/rotation (SR) measurements. Superconductivity is
observed at = 3.6 K as revealed by specific heat and
magnetization measurements. From the TFSR analysis it is clear that
superfluid density well described by an isotropic BCS type -wave gap
structure. Furthermore, from TFSR data we have also estimated the
superconducting carrier density = 6.6 10m,
London penetration depth = 259.59 nm and effective mass
= 1.57 . Our zero-field muon spin relaxation data indicate no
clear sign of spontaneous internal field below , which implies
that the time-reversal symmetry is preserved in HfIrSi. Theoretical
investigation suggests Hf and Ir atoms hybridize strongly along the -axis of
the lattice, which is responsible for the strong three-dimensionality of this
system which screens the Coulomb interaction. As a result despite the presence
of correlated -electrons in this system, the correlation effect is weakened,
promoting electron-phonon coupling to gain importance.Comment: 8 pages, 4 figure
Effect of Plastic Deformation on the Magnetic Properties 304 Stainless Steel During Tensile Loading
The present investigation addresses effect of tensile deformation on the magnetic properties of virgin 304SS as well as cold rolled samples containing a low
volume fraction of 12% and 17% martensite. In-situ Non-destructive evaluation (NDE) techniques by magnetic Barkhausen emission (MBE) and magnetic
hysteresis loop (MHL) measurement were used for evaluation of plastic deformation during tensile loading. Both the techniques indicated different stages of variation in
magnetic properties with progressive plastic deformation. The trend of coercivity and Barkhausen measurements also throw light on the ductile and brittle fracture occurring in virgin and cold worked samples with validation using SEM
fractography
Self-consistent quantum effects in the quark meson coupling model
We derive the equation of state of nuclear matter including vacuum
polarization effects arising from the nucleons and the sigma mesons in the
quark-meson coupling model which incorporates explicitly quark degrees of
freedom with quark coupled to the scalar and vector mesons. This leads to a
softer equation of state for nuclear matter giving a lower value of
incompressibility than would be reached without quantum effects. The {\it
in-medium} nucleon and sigma meson masses are also calculated in a
self-consistent manner.Comment: 10 pages, latex, 5 figure
Bio-oxidation of a low grade chalcopyrite ore by mixed culture of acidophilic bacteria
A study on the extent of biooxidation of a low grade Chalcopyrite ore using a mixed acidophilic bacterial consortium predominantly of the Acidithiobacillus ferrooxidans strain has been carried out. The influence of additive and pH on the bio-oxidation of the ore has been examined. The results of the investigations showed that bio-oxidation was enhanced by the addition of nutrient broth at lower pH. The enhancement in biooxidation of a chalcopyrite ore was 54% and 19% with and without addition of broth in 10 days incubation time, respectively. The study showed that at a lower pH (≤ 4.0), the biooxidation of the ore was higher in presence of broth. Consequently, in presence of nutrient broth, the concentration of Fe and Cu leached were 1200 mg/L and 350 mg/L; and without nutrient broth yielded 580 mg/L and 220 mg/L, respectively within 10 days of incubation and decreases afterwards
Ballistic Applications of Glass and Kevlar Fibre Vinylester Composites
Void-free E-glass and Kevlar-49 fibre reinforced vinylester laminates prepared under compression moulding were found to have Charpy impact strength of 576 KJlm2 and 304 KJlm2, respectively. Ballistic immunisation tests carried out on the glass reinforced vinylester laminates with thickness ranging from 12 mm to 54 mm against 7.62 mm rifle bullets produced an exponential relationship between the per cent attenuation in bullet velocity and the areal density of the laminates; whereas the relationship was linear for 9 mm carbine fire with laminate thicknessvarying from 5.5 mm to 12 mm
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