2,577 research outputs found
Estimating the Explosion Time of Core-Collapse Supernovae from Their Optical Light Curves
Core-collapse supernovae are among the prime candidate sources of high energy
neutrinos. Accordingly, the IceCube collaboration has started a program to
search for such a signal. IceCube operates an online search for neutrino
bursts, forwarding the directions of candidate events to a network of optical
telescopes for immediate follow-up observations. If a supernova is identified
from the optical observations, in addition to a directional coincidence a
temporal photon-neutrino coincidence also needs to be established. To achieve
this, we present a method for estimating the supernova explosion time from its
light curve using a simple model. We test the model with supernova light curve
data from SN1987A, SN2006aj and SN2008D and show that the explosion times can
be determined with an accuracy of better than a few hours.Comment: Version accepted for publication by Astroparticle Physics; 13 pages,
5 figure
Observation of the Cabibbo-suppressed charmed baryon decay Λ_c^+→pφ
We report the observation of the Cabibbo-suppressed decays Λ_c^+→pK^-K^+ and Λ_c^+→pφ using data collected with the CLEO II detector at CESR. The latter mode, observed for the first time with significant statistics, is of interest as a test of color suppression in charm decays. We have determined the branching ratios for these modes relative to Λ_c^+→pK^-π^+ and compared our results with theory
Vertex-Coloring with Star-Defects
Defective coloring is a variant of traditional vertex-coloring, according to
which adjacent vertices are allowed to have the same color, as long as the
monochromatic components induced by the corresponding edges have a certain
structure. Due to its important applications, as for example in the
bipartisation of graphs, this type of coloring has been extensively studied,
mainly with respect to the size, degree, and acyclicity of the monochromatic
components.
In this paper we focus on defective colorings in which the monochromatic
components are acyclic and have small diameter, namely, they form stars. For
outerplanar graphs, we give a linear-time algorithm to decide if such a
defective coloring exists with two colors and, in the positive case, to
construct one. Also, we prove that an outerpath (i.e., an outerplanar graph
whose weak-dual is a path) always admits such a two-coloring. Finally, we
present NP-completeness results for non-planar and planar graphs of bounded
degree for the cases of two and three colors
Further investigations on the proliferative response of mouse bladder epithelium to 4-ethyl-sulphonylnaphthalene-1-sulphonamide.
4-ETHYLSULPHONYLNAPHTHALENE-1-SULPHONAMIDE (ENS*) induces hyperplasia of the bladder epithelium on administration to rats (Paget, 1958) and mice (Sen Gupta, 1962). Bladder tumours result from prolonged feeding of ENS to mice (Clayson and Bonser, 1965; Clayson, Pringle and Bonser, 1967). Hyperplasia is more severe and tumcours are more frequent in female than in male mice. The acute response to a single oral dose of ENS has been studied in some detail (Clayson et al., 1967; Lawson, Dzhioev, Lewis and Clayson, 1968; Levi, Cowen and Cooper, 1969). An increase in DNA synthesis, in the normally quiescent bladder epithelium, is induced at about 16 hours after the administration of the chemical, rises to a maximum at 30-36 hours and thereafter slowly declines. RNA synthesis, necessary for the increase in enzymes for DNA synthesis, occurs during the lag phase. Detailed histopathological, autoradiographic and stathmokinetic investigations show that DNA synthesis and subsequent mitosis occur in every cell layer and involve cells of all ploidies in this epithelium, in contradistinction to the behaviour of other multilayered epithelia in which DNA synthesis and mitosis i
Hsp21potentiates antifungal drug tolerance in Candida albicans
Peer reviewedPublisher PD
Swift follow-up of IceCube triggers, and implications for the Advanced-LIGO era
Between 2011 March and 2014 August Swift responded to 20 triggers from the
IceCube neutrino observatory, observing the IceCube 50% confidence error circle
in X-rays, typically within 5 hours of the trigger. No confirmed counterpart
has been detected. We describe the Swift follow up strategy and data analysis
and present the results of the campaign. We discuss the challenges of
distinguishing the X-ray counterpart to a neutrino trigger from serendipitous
uncatalogued X-ray sources in the error circle, and consider the implications
of our results for future strategies for multi-messenger astronomy, with
particular reference to the follow up of gravitational wave triggers from the
advanced-era detectors.Comment: Accepted for publication in MNRAS. 18 pages, including 8 figures and
4 tables; two of which are landscape-oriente
The Physical Conditions and Dynamics of the Interstellar Medium in the Nucleus of M83: Observations of CO and CI
This paper presents CI, CO J=4-3, and CO J=3-2 maps of the barred spiral
galaxy M83 taken at the James Clerk Maxwell Telescope. Observations indicate a
double peaked structure which is consistent with gas inflow along the bar
collecting at the inner Lindblad resonance. This structure suggests that
nuclear starbursts can occur even in galaxies where this inflow/collection
occurs, in contrast to previous studies of barred spiral galaxies. However, the
observations also suggest that the double peaked emission may be the result of
a rotating molecular ring oriented nearly perpendicular to the main disk of the
galaxy. The CO J=4-3 data indicate the presence of warm gas in the nucleus that
is not apparent in the lower-J CO observations, which suggests that CO J=1-0
emission may not be a reliable tracer of molecular gas in starburst galaxies.
The twelve CI/CO J=4-3 line ratios in the inner 24'' x 24'' are uniform at the
2 sigma level, which indicates that the CO J=4-3 emission is originating in the
same hot photon-dominated regions as the CI emission. The CO J=4-3/J=3-2 line
ratios vary significantly within the nucleus with the higher line ratios
occurring away from peaks of emission along an arc of active star forming
regions. These high line ratios (>1) likely indicate optically thin gas created
by the high temperatures caused by star forming regions in the nucleus of this
starburst galaxy.Comment: 15 pages with 10 figures. To appear in the August 10 1998 issue of
The Astrophysical Journa
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