5,133 research outputs found
A NuSTAR observation of the fast symbiotic nova V745 Sco in outburst
The fast recurrent nova V745 Sco was observed in the 3-79 keV X-rays band
with NuSTAR 10 days after the optical discovery. The measured X-ray emission is
consistent with a collisionally ionized optically thin plasma at temperature of
about 2.7 keV. A prominent iron line observed at 6.7 keV does not require
enhanced iron in the ejecta. We attribute the X-ray flux to shocked
circumstellar material. No X-ray emission was observed at energies above 20
keV, and the flux in the 3-20 keV range was about 1.6 10 erg
cm s. The emission measure indicates an average electron density
of order of 10 cm.
The X-ray flux in the 0.3-10 keV band almost simultaneously measured with
Swift was about 40 times larger, mainly due to the luminous central supersoft
source emitting at energy below 1 keV. The fact that the NuSTAR spectrum cannot
be fitted with a power law, and the lack of hard X-ray emission, allow us to
rule out Comptonized gamma rays, and to place an upper limit of the order of
10 erg cm s on the gamma-ray flux of the nova on the
tenth day of the outburst.Comment: in press in Monthly Notices of the Royal Astronomical Society, 201
Split (n + t)-color partitions and 2-color F-partitions
Andrews [Generalized Frobenius partitions. Memoirs of the American Math. Soc., 301:1{44, 1984] defined the two classes of generalized F-partitions: F-partitions and k-color F-partitions. For many q-series and Rogers-Ramanujan type identities, the bijections are established between F-partitions and (n + t)-color partitions. Recently (n + t)-color partitions have been extended to split (n+t)-color partitions by Agarwal and Sood [Split (n+t)-color partitions and Gordon-McIntosh eight order mock theta functions. Electron. J. Comb., 21(2):#P2.46, 2014]. The purpose of this paper is to study the k-color F-partitions as a combinatorial tool. The paper includes combinatorial proofs and bijections between split (n + t)-color partitions and 2-color F-partitions for some generalized q-series. Our results further give rise to innate three-way combinatorial identities in conjunction with some Rogers-Ramanujan type identities for some particular cases
Comparison of hot-electron transmission in ferromagnetic Ni on epitaxial and polycrystalline Schottky interfaces
The hot-electron attenuation length in Ni is measured as a function of energy
across two different Schottky interfaces viz. a polycrystalline Si(111)/Au and
an epitaxial Si(111)/NiSi_2 interface using ballistic electron emission
microscopy (BEEM). For similarly prepared Si(111) substrates and identical Ni
thickness, the BEEM transmission is found to be lower for the polycrystalline
interface than for the epitaxial interface. However, in both cases, the
hot-electron attenuation length in Ni is found to be the same. This is
elucidated by the temperature-independent inelastic scattering, transmission
probabilities across the Schottky interface, and scattering at dissimilar
interfaces.Comment: 5 pages, 5 figure
LMS Based Adaptive Channel Estimation for LTE Uplink
In this paper, a variable step size based least mean squares (LMS) channel estimation (CE) algorithm is presented for a single carrier frequency division multiple access(SC-FDMA) system under the umbrella of the long term evolution (LTE). This unbiased CE method can automatically adapts the weighting coefficients on the channel condition. Therefore, it does not require knowledge of channel,and noise statistics. Furthermore, it uses a phase weighting scheme to eliminate the signal fluctuations due to noise and decision errors. Such approaches can guarantee the convergence towards the true channel coefficient. The mean and mean square behaviors of the proposed CE algorithm are also analyzed. With the help of theoretical analysis and simulation results, we prove that the proposed algorithm outperforms the existing algorithms in terms of mean square error (MSE) and bit error rate (BER) by more than around 2.5dB
Chiral constituent quark model and the coupling strength of eta'
Using the latest data pertaining to \bar u-\bar d asymmetry and the spin
polarization functions, detailed implications of the possible values of the
coupling strength of the singlet Goldstone boson \eta' have been investigated
in the \chiCQM with configuration mixing. Using \Delta u, \Delta_3, \bar u-\bar
d and \bar u/\bar d, the possible ranges of the coupling parameters a, \alpha^
2, \beta^ 2 and \zeta^ 2, representing respectively the probabilities of
fluctuations to pions, K, \eta and \eta^{'}, are shown to be 0.10 \lesssim a
\lesssim 0.14, 0.2\lesssim \alpha \lesssim 0.5, 0.2\lesssim \beta \lesssim 0.7
and 0.10 lesssim |\zeta| \lesssim 0.70. To constrain the coupling strength of
\eta', detailed fits have been obtained for spin polarization functions, quark
distribution functions and baryon octet magnetic moments corresponding to the
following sets of parameters: a=0.1, \alpha=0.4, \beta=0.7, |\zeta|=0.65 (Case
I); a=0.1, \alpha=0.4, \beta=0.6, |\zeta|=0.70 (Case II); a=0.14, \alpha=0.4,
\beta=0.2, \zeta=0 (Case III) and a=0.13, \alpha=\beta=0.45, |\zeta|=0.10 (Case
IV). Case I represents the calculations where a is fixed to be 0.1, in
accordance with earlier calculations, whereas other parameters are treated free
and the Case IV represents our best fit. The fits clearly establish that a
small non-zero value of the coupling of \eta' is preferred over the higher
values of \eta' as well as when \zeta=0, the latter implying the absence of
\eta' from the dynamics of \chiCQM. Our best fit achieves an overall excellent
fit to the data, in particular the fit for \Delta u, \Delta d, \Delta_8 as well
as the magnetic moments \mu_{n}, \mu_{\Sigma^-}, \mu_{\Sigma^+} and \mu_{\Xi^-}
is almost perfect, the \mu_{\Xi^-} being a difficult case for most of the
similar calculations.Comment: 8 RevTeX pages, 2 Tables, Revised version to appear in Int.J.Mod.Phys
Primary cerebral angitis of the central nervous system: case report
We report a case of a 28 year old female who presented with variedly progressive stroke like illness and raised intracranial pressure. Brain MRI scans revealed pericallosal and periventricular hyperintensities with oedema. Various medications like intravenous immunoglobulin, antibiotics, acyclovir, methyl prednisolone and management for raised intracranial pressure were instituted. She rapidly deteroriated and died on tenth hospital day. Only at autopsy was the diagnosis of primary angitis of central nervous system established
Standardisation of a Vapour Generator for Calibration of Environmental Monitoring Instruments
Very low vapour pressure of 2,4,6 trinitrotoulene (TNT) yields extremely low vapour concentrations at different flow rates in the air, yet considerable quantity of vapours and TNTdust during handling may be present at the workplace environment which is harmful to the health of the personnel working there. The explosive vapours, such as TNT, 2,6-dinitrotoluene (DNT), etc., though harmful to the health of the personnel, are not covered either in the emission standards or in the ambient air quality standards. Presently, no instrument is available for air monitoring of TNT vapours. These vapours need to be collected on-site to estimate TNT concentration. Realising the need for real-time air monitoring of TNT, efforts have been made to understand and device an instrument for on-site determination of TNT vapours parts per billiion (ppb) range. Low-level TNT vapours and TNT buried in the soil in military operations are required to be detected. The instruments for this require careful calibration to yield accurate and reliable results. Hence, an effort has been made to develop a trace-level ppb vapour generator. The vapour generator of a spiral glass column of length 170 cm and inner diameter 4 mm 2 0.5 mm has been used. An activated charcoal glass tube has been used for sampling TNT vapours. The adsorbed TNT vapours were desorbed and analysed using high performance liquid chromatography. Thesolid support used has been studied. These vapours generated at different flow rates have been evaluated. The calibrated instrument can be used for in situ and on-site analysis of samples of TNT and also for samples collected
- …