1,223 research outputs found
Lithiation of InSb and CuSb : A Theoretical Investigation
In this work the mechanism of Li insertion/intercalation in the anode
materials InSb and CuSb is investigated by means of the first principles
total energy calculations. The total charge densities for the lithiated
products of the two compounds are presented. Based on these results the change
in the bonding character on lithiation is discussed. Further, the isomer shift
for InSb and CuSb and there various lithiated products is reported. The
average insertion/intercalation voltage and volume expansion for transitions
from InSb to LiInSb and CuSb to LiCuSb are calculated and found to
be in good agreement with the experimental values. These findings help to
resolve the controversy regarding the lithiation mechanism in InSb.Comment: 5 pages 3 figure
Effects of nonorthogonality in the time-dependent current through tunnel junctions
A theoretical technique which allows to include contributions from
non-orthogonality of the electron states in the leads connected to a tunneling
junction is derived. The theory is applied to a single barrier tunneling
structure and a simple expression for the time-dependent tunneling current is
derived showing explicit dependence of the overlap. The overlap proves to be
necessary for a better quantitative description of the tunneling current, and
our theory reproduces experimental results substantially better compared to
standard approaches.Comment: 4 pages, 1 table, 1 figur
Modeling the Radio and X-ray Emission of SN 1993J and SN 2002ap
Modeling of radio and X-ray observations of supernovae interacting with their
circumstellar media are discussed, with special application to SN 1993J and SN
2002ap. We emphasize the importance of including all relevant physical
mechanisms, especially for the modeling of the radio light curves. The
different conclusions for the absorption mechanism (free-free or synchrotron
self-absorption), as well as departures from an CSM, as
inferred by some authors, are discussed in detail. We conclude that the
evidence for a variation in the mass loss rate with time is very weak. The
results regarding the efficiencies of magnetic field generation and
relativistic particle acceleration are summarized.Comment: 10 pages, 2 figures. Uses svmult.cls. To appear in proceedings of IAU
Colloquium 192 "Supernovae (10 years of SN 1993J)", April 2003, Valencia,
Spain, eds. J. M. Marcaide and K. W. Weile
The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads
We analyze numerically the spin-dependent transport through coherent chains
of three coupled quantum dots weakly connected to external magnetic leads. In
particular, using the diagrammatic technique on the Keldysh contour, we
calculate the conductance, shot noise and tunnel magnetoresistance (TMR) in the
sequential and cotunneling regimes. We show that transport characteristics
greatly depend on the strength of the interdot Coulomb correlations, which
determines the spacial distribution of electron wave function in the chain.
When the correlations are relatively strong, depending on the transport regime,
we find both negative TMR as well as TMR enhanced above the Julliere value,
accompanied with negative differential conductance (NDC) and super-Poissonian
shot noise. This nontrivial behavior of tunnel magnetoresistance is associated
with selection rules that govern tunneling processes and various high-spin
states of the chain that are relevant for transport. For weak interdot
correlations, on the other hand, the TMR is always positive and not larger than
the Julliere TMR, although super-Poissonian shot noise and NDC can still be
observed
Constraints on the luminosity of the stellar remnant in SNR1987A
We obtain photometric constraints on the luminosity of the stellar remnant in
SNR1987A using XMM-Newton and INTEGRAL data. The upper limit in the 2--10 keV
band based on the XMM-Newton data is L<5*10^{34}erg/s. We note, however, that
the optical depth of the envelope is still high in the XMM-Newton band,
therefore, this upper limit does not constrain the true unabsorbed luminosity
of the central source. The optical depth is expected to be small in the hard
X-ray band of the IBIS telescope aboard the INTEGRAL observatory, therefore it
provides an unobscured look at the stellar remnant. We did not detect
statistically significant emission from SN1987A in the 20-60 keV band with the
upper limit of L<1.1*10^{36}erg/s. We also obtained an upper limit on the mass
of radioactive 44Ti M(44Ti)<10^{-3}Msun.Comment: 5 pages, 3 figures, accepted for publication in Astronomy Letter
425 Pain Representation In Fibromyalgia Patients And Healthy Controls Using Event‐Related Fmri
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90315/1/S1090-3801_06_60428-X.pd
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Preface
Preface - The second International Conference on Mathematical Modeling in Physical Sciences (IC-MSQUARE) took place at Prague, Czech Republic, from Sunday 1 September to Thursday 5 September 2013
Observing Supernova 1987A with the Refurbished Hubble Space Telescope
Observations with the Hubble Space Telescope (HST), conducted since 1990, now
offer an unprecedented glimpse into fast astrophysical shocks in the young
remnant of supernova 1987A. Comparing observations taken in 2010 using the
refurbished instruments on HST with data taken in 2004, just before the Space
Telescope Imaging Spectrograph failed, we find that the Ly-a and H-a lines from
shock emission continue to brighten, while their maximum velocities continue to
decrease. We observe broad blueshifted Ly-a, which we attribute to resonant
scattering of photons emitted from hotspots on the equatorial ring. We also
detect NV~\lambda\lambda 1239,1243 A line emission, but only to the red of
Ly-A. The profiles of the NV lines differ markedly from that of H-a, suggesting
that the N^{4+} ions are scattered and accelerated by turbulent electromagnetic
fields that isotropize the ions in the collisionless shock.Comment: Science, accepted. Science Express, 02 Sept 2010. 5 figures.
Supporting online material can be found at
http://www.sciencemag.org/cgi/content/full/sci;science.1192134/DC
A Decade of SN1993J: Discovery of Wavelength Effects in the Expansion Rate
We have studied the growth of the shell-like radio structure of supernova
SN1993J in M81 from September 1993 through October 2003 with very-long-baseline
interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18cm. For
this purpose, we have developed a method to accurately determine the outer
radius (R) of any circularly symmetric compact radio structure like SN1993J.
The source structure of SN1993J remains circularly symmetric (with deviations
from circularity under 2%) over almost 4000 days. We characterize the
decelerated expansion of SN 1993J through approximately day 1500 after
explosion with an expansion parameter ().
However, from that day onwards the expansion is different when observed at 6
and 18cm. Indeed, at 18cm, the expansion can be well characterized by the same
as before day 1500, while at 6cm the expansion appears more decelerated,
and is characterized by another expansion parameter, .
Therefore, since about day 1500 on, the radio source size has been
progressively smaller at 6cm than at 18cm. These findings are in stark contrast
to previous reports by other authors on the details of the expansion. In our
interpretation the supernova expands with a single expansion parameter, , and the 6cm results beyond day 1500 are due to physical
effects, perhaps also coupled to instrumental limitations. Two physical effects
may be involved: (a) a changing opacity of the ejecta to the 6cm radiation, and
(b) a radial decrease of the magnetic field in the emitting region.
(Long abstract cut. Please, read full abstract in manuscript).Comment: 21 pages, 19 figures, accepted in A&
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