855 research outputs found
Explosions inside Ejecta and Most Luminous Supernovae
The extremely luminous supernova SN2006gy is explained in the same way as
other SNIIn events: light is produced by a radiative shock propagating in a
dense circumstellar envelope formed by a previous weak explosion. The problems
in the theory and observations of multiple-explosion SNe IIn are briefly
reviewed.Comment: 9 pages, 6 figures, LateX aipproc.cls. A bit more details and color
added to Fig.3. The 10th International Symposium on Origin of Matter and
Evolution of Galaxies (OMEG07), Sapporo, Japan, December 200
Analytical Study on the Sunyaev-Zeldovich Effect for Clusters of Galaxies. II. comparison of covariant formalisms
We study a covariant formalism for the Sunyaev-Zeldovich effects developed in
the previous papers by the present authors, and derive analytic expressions for
the redistribution functions in the Thomson approximation. We also explore
another covariant formalism recently developed by Poutanen and Vurm. We show
that the two formalisms are mathematically equivalent in the Thomson
approximation which is fully valid for the cosmic microwave background photon
energies. The present finding will establish a theoretical foundation for the
analysis of the Sunyaev-Zeldovich effects for the clusters of galaxies.Comment: Accepted version, 7 pages, 1 figure, accepted by Physical Review D
for publicatio
Mesoscale observations of Joule heating near an auroral arc and ion-neutral collision frequency in the polar cap E region
We report on the first mesoscale combined ionospheric and thermospheric observations, partly in the vicinity of an auroral arc, from Svalbard in the polar cap on 2 February 2010. The EISCAT Svalbard radar employed a novel scanning mode in order to obtain F and E region ion flows over an annular region centered on the radar. Simultaneously, a colocated Scanning Doppler Imager observed the E region neutral winds and temperatures around 110 km altitude using the 557.7 nm auroral optical emission. Combining the ion and neutral data permits the E region Joule heating to be estimated with an azimuthal spatial resolution of ∼64 km at a radius of ∼163 km from the radar. The spatial distribution of Joule heating shows significant mesoscale variation. The ion-neutral collision frequency is measured in the E region by combining all the data over the entire field of view with only weak aurora present. The estimated ion-neutral collision frequency at ∼113 km altitude is in good agreement with the MSIS atmospheric model
Actinomycosis complicating sigmoid diverticular disease: a case report
A 63-year-old Caucasian woman was admitted to hospital as hypotensive with abdominal tenderness and vaginal discharge. Laboratory investigations showed microcytic anaemia, low albumin and high white cell count. Computerised tomography scans revealed small bowel dilatation, sigmoid diverticula, ascites and pelvic fluid. The endometrial pipelle was positive and vaginal swab was negative for actinomyces. Post mortem examination revealed widespread sigmoid diverticular disease and bowel perforation with an intense inflammation. Actinomycotic granules were noted in the diverticular inflammatory debris, pelvic abscess and lung sections. Clinical course and histomorphological findings favour the perforating sigmoid diverticular actinomycosis as an origin of the systemic infection
Mind the buffering capacity of citric acid
Many microbial cultures are buffered with citric acid over a pH range of 2.5 to 7.0 since the pKa values for this triprotic acid are 3.13, 4.76 and 6.40, as shown in The Merck Index (pp 330-331, 10th Edition, Martha Windholz, ed.). However, the information about the buffering range of this weak acid is controvertial since the pKa3 value may be 5.40, as specified in Day and Underwood (Quantitative Analysis, 6th Edition, 1991, p. 662. New Jersey: Prentice Hall). With this in mind, we determined the pKa values of citric acid at concentrations ranging from 5 mM to 50 mM, concentrations which are the most employed in buffers for the culture of many microorganisms
Coupled-Map Modeling of One-Dimensional Traffic Flow
We propose a new model of one-dimensional traffic flow using a coupled map
lattice. In the model, each vehicle is assigned a map and changes its velocity
according to it. A single map is designed so as to represent the motion of a
vehicle properly, and the maps are coupled to each other through the headway
distance. By simulating the model, we obtain a plot of the flow against the
concentration similar to the observed data in real traffic flows. Realistic
traffic jam regions are observed in space-time trajectories.Comment: 5 postscript figures available upon reques
Photometric Evolution of SNe Ib/c 2004ao, 2004gk and 2006gi
Photometric observations of three core collapse supernovae (SNe 2004ao,
2004gk and 2006gi), covering about 200 days of evolution are presented and
analyzed. The photometric behaviour of the three objects is consistent with
their membership of the envelope-stripped type Ib/c class. Pseudo-bolometric
light curves are constructed. The corresponding measured -folding times are
found to be faster compared to the Co decay (i.e. 111.3 d), suggesting
that a proportion of -rays increasing with time have escaped without
thermalization, owing to the low mass nature of the ejecta. SN 2006gi has
almost identical post maximum decline phase luminosities as SN 1999ex, and
found to be similar to both SNe 1999dn and 1999ex in terms of the
quasi-bolometric shape, placing it among the fast decliner Ib objects. SN
2004ao appears to fit within the slow decliner Ib SNe. SNe 2004ao and 2004gk
display almost identical luminosities in the [50-100] days time interval,
similar to SN 1993J. A preliminary simplified ray deposition model is
described and applied to the computed pseudo-bolometric light curves, allowing
one to find a range in the ejecta and Ni masses. The optical and
quasi-bolometric light curves, and the colour evolution of SN 2004gk are
found to show a sudden drop after day 150. Correlating this fact to dust
formation is premature and requires further observational evidence.Comment: Accepted for publication in The Astrophysical Journal; (11
two-columns Pages, 11 figures, 6 Tables; Scheduled for publication in April
2011
Properties of Newly Formed Dust Grains in The Luminous Type IIn Supernova 2010jl
Supernovae (SNe) have been proposed to be the main production sites of dust
grains in the Universe. Our knowledge on their importance to dust production
is, however, limited by observationally poor constraints on the nature and
amount of dust particles produced by individual SNe. In this paper, we present
a spectrum covering optical through near-Infrared (NIR) light of the luminous
Type IIn supernova (SN IIn) 2010jl around one and half years after the
explosion. This unique data set reveals multiple signatures of newly formed
dust particles. The NIR portion of the spectrum provides a rare example where
thermal emission from newly formed hot dust grains is clearly detected. We
determine the main population of the dust species to be carbon grains at a
temperature of ~1,350 - 1,450K at this epoch. The mass of the dust grains is
derived to be ~(7.5 - 8.5) x 10^{-4} Msun. Hydrogen emission lines show
wavelength-dependent absorption, which provides a good estimate on the typical
size of the newly formed dust grains (~0.1 micron, and most likely <~0.01
micron). We attribute the dust grains to have been formed in a dense cooling
shell as a result of a strong SN-circumstellar media (CSM) interaction. The
dust grains occupy ~10% of the emitting volume, suggesting an inhomogeneous,
clumpy structure. The average CSM density is required to be >~3 x 10^{7}
cm^{-3}, corresponding to a mass loss rate of >~0.02 Msun yr^{-1} (for a mass
loss wind velocity of ~100 km s^{-1}). This strongly supports a scenario that
SN 2010jl and probably other luminous SNe IIn are powered by strong
interactions within very dense CSM, perhaps created by Luminous Blue Variable
(LBV)-like eruptions within the last century before the explosion.Comment: 18 pages, 11 figures. Accepted by ApJ on 30 July 2013. The accepted
version was submitted on 8 July 2013, and the original version was submitted
on 3 March 201
Radiative heat transfer between nanostructures
We simplify the formalism of Polder and Van Hove [Phys.Rev.B {\bf 4},
3303(1971)], which was developed to calculate the heat transfer between
macroscopic and nanoscale bodies of arbitrary shape, dispersive and adsorptive
dielectric properties. In the non-retarded limit, at small distances between
the bodies, the problem is reduced to the solution of an electrostatic problem.
We apply the formalism to the study of the heat transfer between: (a) two
parallel semi-infinite bodies, (b) a semi-infinite body and a spherical body,
and (c) that two spherical bodies. We consider the dependence of the heat
transfer on the temperature , the shape and the separation . We determine
when retardation effects become important.Comment: 11 pages, 5 figure
Quasifree Pion Electroproduction from Nuclei in the Region
We present calculations of the reaction in the
distorted wave impulse approximation. The reaction allows for the study of the
production process in the nuclear medium without being obscured by the details
of nuclear transition densities. First, a pion electroproduction operator
suitable for nuclear calculations is obtained by extending the Blomqvist-Laget
photoproduction operator to the virtual photon case. The operator is gauge
invariant, unitary, reference frame independent, and describes the existing
data reasonably well. Then it is applied in nuclei to predict nuclear cross
sections under a variety of kinematic arrangements. Issues such as the effects
of gauge-fixing, the interference of the resonance with the
background, sensitivities to the quadrupole component of the
excitation and to the electromagnetic form factors, the role of final-state
interactions, are studied in detail. Methods on how to experimentally separate
the various pieces in the coincidence cross section are suggested. Finally, the
model is compared to a recent SLAC experiment.Comment: 27 pages in REVTEX, plus 22 PS figures embedded using psfig.sty
(included), uuencode
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