2,086 research outputs found
Morphometry of the Dugong Dugon (Muller, 1776) skeleton based on Indian Museum specimens, Kolkata, India
817-821The present study discussed about detailed examination of skeleton characters of four dugong specimens received from Indian Museum. The specimens were deposited and preserved in the National Zoological Collection (ZSI/27608; ZSI/27609; ZSI/27610; ZSI/27611) of The Mammal and Osteological Section, Zoological Survey of India, Kolkata
Relativistic spin precession in the binary PSR J11416545
PSR J11416545 is a precessing binary pulsar that has the rare potential to
reveal the two-dimensional structure of a non-recycled pulsar emission cone. It
has undergone of relativistic spin precession in the
years since its discovery. In this paper, we present a detailed Bayesian
analysis of the precessional evolution of the width of the total intensity
profile, to understand the changes to the line-of-sight impact angle ()
of the pulsar using four different physically motivated prior distribution
models. Although we cannot statistically differentiate between the models with
confidence, the temporal evolution of the linear and circular polarisations
strongly argue that our line-of-sight crossed the magnetic pole around MJD
54000 and that only two models remain viable. For both these models, it appears
likely that the pulsar will precess out of our line-of-sight in the next
years, assuming a simple beam geometry. Marginalising over suggests
that the pulsar is a near-orthogonal rotator and provides the first
polarization-independent estimate of the scale factor () that
relates the pulsar beam opening angle () to its rotational period ()
as : we find it to be at 1.4
GHz with 99\% confidence. If all pulsars emit from opposite poles of a dipolar
magnetic field with comparable brightness, we might expect to see evidence of
an interpulse arising in PSR J11416545, unless the emission is patchy.Comment: Accepted for publication in Astrophysical Journal Letter
A modelling study of the latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum
International audienceLatitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum have been examined by using values modelled by SUPIM (Sheffield University Plasmasphere Ionosphere Model) and observations made by the DMSP F10 satellite at 21.00 LT near 800 km altitude. The modelled values confirm that the crests observed near 15° latitude in the winter hemisphere are due to adiabatic heating and the troughs observed near the magnetic equator are due to adiabatic cooling as plasma is transported along the magnetic field lines from the summer hemisphere to the winter hemisphere. The modelled values also confirm that the interhemispheric plasma transport needed to produce the required adiabatic heating/cooling can be induced by F-region neutral winds. It is shown that the longitudinal variations in the observed troughs and crests arise mainly from the longitudinal variations in the magnetic meridional wind. At longitudes where the magnetic declination angle is positive the eastward geographic zonal wind combines with the northward (summer hemisphere to winter hemisphere) geographic meridional wind to enhance the northward magnetic meridional wind. This leads to deeper troughs and enhanced crests. At longitudes where the magnetic declination angle is negative the eastward geographic zonal wind opposes the northward geographic meridional wind and the trough depth and crest values are reduced. The characteristic features of the troughs and crests depend, in a complicated manner, on the field-aligned flow of plasma, thermal conduction, and inter-gas heat transfer. At the latitudes of the troughs/crests, the low/high plasma temperatures lead to increased/decreased plasma concentrations.Key words: Ionosphere (equatorial ionosphere; ionosphere-atmosphere interactions
Automated Analysis of Fluorescence Microscopy Images to Identify Protein-Protein Interactions
The identification of protein interactions is important for elucidating biological networks. One obstacle in comprehensive interaction studies is the analyses of large datasets, particularly those containing images. Development of an automated system to analyze an image-based protein interaction dataset is needed. Such an analysis system is described here, to automatically extract features from fluorescence microscopy images obtained from a bacterial protein interaction assay. These features are used to relay quantitative values that aid in the automated scoring of positive interactions. Experimental observations indicate that identifying at least 50% positive cells in an image is sufficient to detect a protein interaction. Based on this criterion, the automated system presents 100% accuracy in detecting positive interactions for a dataset of 16 images. Algorithms were implemented using MATLAB and the software developed is available on request from the authors
Static conductivity of charged domain wall in uniaxial ferroelectric-semiconductors
Using Landau-Ginzburg-Devonshire theory we calculated numerically the static
conductivity of both inclined and counter domain walls in the uniaxial
ferroelectrics-semiconductors of n-type. We used the effective mass
approximation for the electron and holes density of states, which is valid at
arbitrary distance from the domain wall. Due to the electrons accumulation, the
static conductivity drastically increases at the inclined head-to-head wall by
1 order of magnitude for small incline angles theta pi/40 by up 3 orders of
magnitude for the counter domain wall (theta=pi/2). Two separate regions of the
space charge accumulation exist across an inclined tail-to-tail wall: the thin
region in the immediate vicinity of the wall with accumulated mobile holes and
the much wider region with ionized donors. The conductivity across the
tail-to-tail wall is at least an order of magnitude smaller than the one of the
head-to-head wall due to the low mobility of holes, which are improper carries.
The results are in qualitative agreement with recent experimental data for
LiNbO3 doped with MgO.Comment: 20 pages, 6 figures, 1 appendi
The UTMOST pulsar timing programme I: overview and first results
We present an overview and the first results from a large-scale pulsar timing
programme that is part of the UTMOST project at the refurbished Molonglo
Observatory Synthesis Radio Telescope (MOST) near Canberra, Australia. We
currently observe more than 400 mainly bright southern radio pulsars with up to
daily cadences. For 205 (8 in binaries, 4 millisecond pulsars) we publish
updated timing models, together with their flux densities, flux density
variability, and pulse widths at 843 MHz, derived from observations spanning
between 1.4 and 3 yr. In comparison with the ATNF pulsar catalogue, we improve
the precision of the rotational and astrometric parameters for 123 pulsars, for
47 by at least an order of magnitude. The time spans between our measurements
and those in the literature are up to 48 yr, which allows us to investigate
their long-term spin-down history and to estimate proper motions for 60
pulsars, of which 24 are newly determined and most are major improvements. The
results are consistent with interferometric measurements from the literature. A
model with two Gaussian components centred at 139 and fits the transverse velocity distribution best. The pulse duty
cycle distributions at 50 and 10 per cent maximum are best described by
log-normal distributions with medians of 2.3 and 4.4 per cent, respectively. We
discuss two pulsars that exhibit spin-down rate changes and drifting subpulses.
Finally, we describe the autonomous observing system and the dynamic scheduler
that has increased the observing efficiency by a factor of 2-3 in comparison
with static scheduling.Comment: 31 pages, 14 figures, 6 tables, accepted for publication in MNRA
Five new real-time detections of Fast Radio Bursts with UTMOST
We detail a new fast radio burst (FRB) survey with the Molonglo Radio
Telescope, in which six FRBs were detected between June 2017 and December 2018.
By using a real-time FRB detection system, we captured raw voltages for five of
the six events, which allowed for coherent dedispersion and very high time
resolution (10.24 s) studies of the bursts. Five of the FRBs show temporal
broadening consistent with interstellar and/or intergalactic scattering, with
scattering timescales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows
remarkable temporal structure, with 3 peaks each separated by 1 ms. We searched
for phase-coherence between the leading and trailing peaks and found none,
ruling out lensing scenarios. Based on this survey, we calculate an all-sky
rate at 843 MHz of events sky day to a fluence
limit of 8 Jy-ms: a factor of 7 below the rates estimated from the Parkes and
ASKAP telescopes at 1.4 GHz assuming the ASKAP-derived spectral index
(). Our results suggest that FRB
spectra may turn over below 1 GHz. Optical, radio and X-ray followup has been
made for most of the reported bursts, with no associated transients found. No
repeat bursts were found in the survey.Comment: 13 pages, 11 figures, submitted to MNRA
Conductivity of twin walls - surface junctions in ferroelastics: interplay of deformation potential, octahedral rotations, improper ferroelectricity and flexoelectric coupling
Electronic and structural phenomena at the twin domain wall-surface junctions
in the ferroelastic materials are analyzed. Carriers accumulation caused by the
strain-induced band structure changes originated via the deformation potential
mechanism, structural order parameter gradient, rotostriction and flexoelectric
coupling is explored. Approximate analytical results show that inhomogeneous
elastic strains, which exist in the vicinity of the twin walls - surface
junctions due to the rotostriction coupling, decrease the local band gap via
the deformation potential and flexoelectric coupling mechanisms. This is the
direct mechanism of the twin walls static conductivity in ferroelastics and, by
extension, in multiferroics and ferroelectrics. On the other hand,
flexoelectric and rotostriction coupling leads to the appearance of the
improper polarization and electric fields proportional to the structural order
parameter gradient in the vicinity of the twin walls - surface junctions. The
"flexo-roto" fields leading to the carrier accumulation are considered as
indirect mechanism of the twin walls conductivity. Comparison of the direct and
indirect mechanisms illustrates complex range of phenomena directly responsible
for domain walls static conductivity in materials with multiple order
parameters.Comment: 35 pages, 11 figures, 3 table, 3 appendices Improved set of
rotostriction coefficients are used in calculation
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