236 research outputs found
Synthesis of SmFeAsO by an Easy and Versatile Route and its Physical Property Characterization
We report synthesis, structure, electrical transport and heat capacity of
SmFeAsO. The title compound is synthesized by one-step encapsulation of
stoichiometric FeAs, Sm, and Sm2O3 in an evacuated (10-5 Torr) quartz tube by
prolong (72 hours) annealing at 1100oC. The as synthesized compound is
crystallized in tetragonal structure with P4/nmm space group having lattice
parameters a = 3.93726(33) A and c = 8.49802(07) A. The resistance (R-T)
measurements on the compound exhibited ground state spin-density-wave
(SDW)-like metallic steps below 140 K. Heat capacity CP(T) measurements on the
title compound, showed an anomaly at around 140 K, which is reminiscent of the
SDW ordering of the compound. At lower temperatures the CP(T) shows a clear
peak at around 4.5 K. At lower temperature below 20 K, Cp(T) is also measured
under an applied field of 7 Tesla. It is concluded that the CP(T) peak at 4.5 K
is due to the anti-ferromagnetic(AFM) ordering of Sm3+ spins. These results are
in confirmation with ordering of Sm in Sm2-xCexCuO4.Comment: 9 pages Text + Figs Contact Author ([email protected]
Evidence of a Sub-Saturn around EPIC~211945201
We report here strong evidence for a sub-Saturn around EPIC~211945201 and
confirm its planetary nature. EPIC~211945201b was found to be a planetary
candidate from {\it K2} photometry in Campaigns 5 \& 16, transiting a bright
star (, G0 spectral type) in a 19.492 day orbit. However,
the photometric data combined with false positive probability calculations
using VESPA was not sufficient to confirm the planetary scenario. Here we
present high-resolution spectroscopic follow-up of the target using the PARAS
spectrograph (19 radial velocity observations) over a time-baseline of 420
days. We conclusively rule out the possibility of an eclipsing binary system
and confirm the 2- detection of a sub-Saturn planet. The confirmed
planet has a radius of 6.12, and a mass of
~. We also place an upper limit on the mass
(within the 3- confidence interval) at 42~ above the
nominal value. This results in the Saturn-like density of
g~cm. Based on the mass and radius, we provide a
preliminary model-dependent estimate that the heavy element content is 60-70 \%
of the total mass. This detection is important as it adds to a sparse catalog
of confirmed exoplanets with masses between 10-70 and radii
between 4-8 , whose masses and radii are measured to a precision of
50\% or better (only 23 including this work).Comment: Accepted for publication in The Astronomical Journal, 17 pages, 8
figure
High Field Performance of Nano-Diamond Doped MgB2 Superconductor
Polycrystalline MgB2-nDx (x= 0 to 0.1) samples are synthesized by solid-state
route with ingredients of Mg, B and n-Diamond. The results from
magneto-transport and magnetization of nano-diamond doped MgB2-nDx are
reported. Superconducting transition temperature (Tc) is not affected
significantly by x up to x = 0.05 and latter decreases slightly for higher x >
0.05. R(T) vs H measurements show higher Tc values under same applied magnetic
fields for the nano-diamond added samples, resulting in higher estimated Hc2
values. From the magnetization measurements it was found that irreversibility
field value Hirr for the pristine sample is 7.5 Tesla at 4 K and the same is
increased to 13.5 Tesla for 3-wt% nD added sample at the same temperature. The
Jc(H) plots at all temperatures show that Jc value is lowest at all applied
fields for pristine MgB2 and the sample doped with 3-wt% nD gives the best Jc
values at all fields. For the pure sample the value of Jc is of the order of
105 A/cm2 at lower fields but it decreases very fast as the magnetic field is
applied and becomes negligible above 7 Tesla. The Jc is 40 times higher than
pure MgB2 at 10 K at 6 Tesla field in case of 3%nD doped sample and its value
is still of the order of 103 A/cm2 at 10 Tesla for the same sample. On the
other hand at 20K the 5%nD sample shows the best performance at higher fields.
These results are discussed in terms of extrinsic pinning due to dispersed
n-Diamond in the host MgB2 matrix along with the intrinsic pinning due to
possible substitution of C at Boron site and increased inter-band scattering
for highly doped samples resulting in extraordinary performance of the doped
system.Comment: 12 PAGES (TEXT+FIGS). ACCEPTED: J. APPL.PHYS. (MMM-2007 Proceedings
Suppression of power-broadening in strong-coupling photoassociation in the presence of a Feshbach resonance
Photoassociation (PA) spectrum in the presence of a magnetic Feshbach
resonance is analyzed. Nonperturbative solution of the problem yields
analytical expressions for PA linewidth and shift which are applicable for
arbitrary PA laser intensity and magnetic field tuning of Feshbach Resonance.
We show that by tuning magnetic field close to Fano minimum, it is possible to
suppress power broadening at increased laser intensities. This occurs due to
quantum interference of PA transitions from unperturbed and perturbed
continuum. Line narrowing at high laser intensities is accompanied by large
spectral shifts. We briefly discuss important consequences of line narrowing in
cold collisions.Comment: 12 pages, 5 figure
Study of disparate sectors in fisheries
Fisheries employ a number of people and fisheries industry is truly an
amalgamation of various disparate sectors. Fisheries play an important role
in Indian economy and it provides employment to a number of people. For
planning of integrated development of fisheries industry and resource
management, a considerable amount of information is required. In this paper
a study of the disparate sectors with regards to the nature of work, number
of workers, sex-wise participation, earning type and earning in Indian Rupees
in the year 1991-92,1992-93,1993-94a nd 1999-2000h as been done in a selected
fishing village. The geographical locale where the study has been done is
Versova fishing village which is a major fish landing centre in Mumbai. The
study has revealed that there are a number of disparate sectors in fisheries
and in thsi fishing village on an average, a boat owner provided employment
to 30.60 people in the year 1994 and to 19.25 people in 1999
Genetic analysis of HIV-1 Circulating Recombinant Form 02_AG, B and C subtype-specific envelope sequences from Northern India and their predicted co-receptor usage
HIV-1 epidemic in India is largely driven by subtype C but other subtypes or recombinants have also been reported from several states of India. This is mainly due to the co-circulation of other genetic subtypes that potentially can recombine to generate recombinant/mosaic genomes. In this study, we report detail genetic characterization of HIV-1 envelope sequences from North India (Delhi and neighboring regions). Six of 13 were related to subtype C, one B and the rest six showed relatedness with CRF02_AG strain. The subtype C possessed the highly conserved GPGQ motif but subtype B possessed the GPGR motif in the V3 loop as observed earlier. While most of the sequences suggested CCR5 co-receptor usage, one subtype C sample clearly indicated CXCR4 usage. A successful mother to child transmission was established in two pairs. Thus, co-circulation of multiple subtypes (B and C) and the recombinant CRF02_AG strains in North India suggests a rapidly evolving scenario of HIV-1 epidemic in this region with impact on vaccine formulation. Since this is the first report of CRF02_AG envelope from India, it will be important to monitor the spread of this strain and its impact on HIV-1 transmission in India
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