12,622 research outputs found
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
Primordial magnetic field limits from cosmological data
We study limits on a primordial magnetic field arising from cosmological
data, including that from big bang nucleosynthesis, cosmic microwave background
polarization plane Faraday rotation limits, and large-scale structure
formation. We show that the physically-relevant quantity is the value of the
effective magnetic field, and limits on it are independent of how the magnetic
field was generated.Comment: 7 pages, 6 figure
Energy and momentum of Bianchi Type VI_h Universes
We obtain the energy and momentum of the Bianchi type VI_h universes using
different prescriptions for the energy-momentum complexes in the framework of
general relativity. The energy and momentum of the Bianchi VI_h universe are
found to be zero for the parameter h = -1 of the metric. The vanishing of these
results support the conjecture of Tryon that Universe must have a zero net
value for all conserved quantities.This also supports the work of Nathan Rosen
with the Robertson-Walker metric. Moreover, it raises an interesting question:
"Why h=-1 case is so special?
Broad Band Optical Polarimetric Study of IC 1805
We present the BVR broad band polarimetric observations of 51 stars belonging
to the young open cluster IC 1805. Along with the photometric data from the
literature we have modeled and subtracted the foreground dust contribution from
the maximum polarization (P_{max}) and colour excess (E_{B-V}). The mean value
of the P_max for intracluster medium and the foreground are found to be 5.008
+/-0.005 % and 4.865 +/-0.022 % respectively. Moreover, the mean value of the
wavelength of maximum polarization (lambda_{max}) for intracluster medium is
0.541 +/- 0.003 micro m, which is quite similar as the general interstellar
medium (ISM). The resulting intracluster dust component is found to have
negligible polarization efficiency as compared to interstellar dust. Some of
the observed stars in IC 1805 have shown the indication of intrinsic
polarization in their measurements.Comment: 8 pages, 7 figures, Accepted for publication in MNRA
A Study of starless dark cloud LDN 1570: Distance, Dust properties and Magnetic field geometry
We wish to map the magnetic field geometry and to study the dust properties
of the starless cloud, L1570, using multi-wavelength optical polarimetry and
photometry of the stars projected on the cloud. We made R-band imaging
polarimetry of the stars projected on a cloud, L1570, to trace the magnetic
field orientation. We also made multi-wavelength polarimetric and photometric
observations to constrain the properties of dust in L1570. We estimated a
distance of 394 +/- 70 pc to the cloud using 2MASS JHKs colours. Using the
values of the Serkowski parameters namely , ,
{\lambda}max and the position of the stars on near infrared color-color
diagram, we identified 13 stars that could possibly have intrinsic polarization
and/or rotation in their polarization angles. One star, 2MASS
J06075075+1934177, which is a B4Ve spectral type, show the presence of diffuse
interstellar bands in the spectrum apart from showing H{\alpha} line in
emission. There is an indication for the presence of slightly bigger dust
grains towards L1570 on the basis of the dust grain size-indicators such as
{\lambda}max and Rv values. The magnetic field lines are found to be parallel
to the cloud structures seen in the 250{\mu}m images (also in 8{\mu}m and
12{\mu}m shadow images) of L1570. Based on the magnetic field geometry, the
cloud structure and the complex velocity structure, we believe that L1570 is in
the process of formation due to the converging flow material mediated by the
magnetic field lines. Structure function analysis showed that in the L1570
cloud region the large scale magnetic fields are stronger when compared with
the turbulent component of magnetic fields. The estimated magnetic field
strengths suggest that the L1570 cloud region is sub-critical and hence could
be strongly supported by the magnetic field lines.Comment: 26 pages, 22 figures, and 7 tables; Accepted for its publication in
A&
Star formation in young star cluster NGC 1893
We present a comprehensive multi-wavelength study of the star-forming region
NGC 1893 to explore the effects of massive stars on low-mass star formation.
Using near-infrared colours, slitless spectroscopy and narrow-band
photometry in the cluster region we have identified candidate young stellar
objects (YSOs) distributed in a pattern from the cluster to one of the nearby
nebulae Sim 129. The colour-magnitude diagram of the YSOs indicates
that majority of these objects have ages between 1 to 5 Myr. The spread in the
ages of the YSOs may indicate a non-coeval star formation in the cluster. The
slope of the KLF for the cluster is estimated to be , which agrees
well with the average value () reported for young clusters. For the
entire observed mass range the value of the slope of
the initial mass function, ', comes out to be , which is
in agreement with the Salpeter value of -1.35 in the solar neighborhood.
However, the value of ' for PMS phase stars (mass range ) is found to be which is shallower than the
value () obtained for MS stars having mass range indicating a break in the slope of the mass function at . Estimated ' values indicate an effect of mass segregation
for main-sequence stars, in the sense that massive stars are preferentially
located towards the cluster center. The estimated dynamical evolution time is
found to be greater than the age of the cluster, therefore the observed mass
segregation in the cluster may be the imprint of the star formation process.
There is evidence for triggered star formation in the region, which seems to
govern initial morphology of the cluster.Comment: Accepted for the publication in MNRAS, 21 pages, 26 figures, 10
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GENERAL SOLUTION TO A CLASS OF UNSTEADY HEAT CONDUCTION PROBLEMS IN A SOLID CYLINDER WITH THE CONVECTIVE TYPE OF TIME-DEPENDENT BOUNDARY CONDITIONS
Chemotaxis of Burkholderia sp. Strain SJ98 towards chloronitroaromatic compounds that it can metabolise
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