3,203 research outputs found
Non-Weyl Resonance Asymptotics for Quantum Graphs
We consider the resonances of a quantum graph that consists of a
compact part with one or more infinite leads attached to it. We discuss the
leading term of the asymptotics of the number of resonances of in
a disc of a large radius. We call a \emph{Weyl graph} if the
coefficient in front of this leading term coincides with the volume of the
compact part of . We give an explicit topological criterion for a
graph to be Weyl. In the final section we analyze a particular example in some
detail to explain how the transition from the Weyl to the non-Weyl case occurs.Comment: 29 pages, 2 figure
Discrete Nodal Domain Theorems
We give a detailed proof for two discrete analogues of Courant's Nodal Domain
Theorem
Non-Weyl asymptotics for quantum graphs with general coupling conditions
Inspired by a recent result of Davies and Pushnitski, we study resonance
asymptotics of quantum graphs with general coupling conditions at the vertices.
We derive a criterion for the asymptotics to be of a non-Weyl character. We
show that for balanced vertices with permutation-invariant couplings the
asymptotics is non-Weyl only in case of Kirchhoff or anti-Kirchhoff conditions,
while for graphs without permutation numerous examples of non-Weyl behaviour
can be constructed. Furthermore, we present an insight helping to understand
what makes the Kirchhoff/anti-Kirchhoff coupling particular from the resonance
point of view. Finally, we demonstrate a generalization to quantum graphs with
nonequal edge weights.Comment: minor changes, to appear in Pierre Duclos memorial issue of J. Phys.
A: Math. Theo
-Spectral theory of locally symmetric spaces with -rank one
We study the -spectrum of the Laplace-Beltrami operator on certain
complete locally symmetric spaces with finite volume and
arithmetic fundamental group whose universal covering is a
symmetric space of non-compact type. We also show, how the obtained results for
locally symmetric spaces can be generalized to manifolds with cusps of rank
one
Surge in Expression of Carboxylesterase 1 During the Post-neonatal Stage Enables a Rapid Gain of the Capacity to Activate the Anti-influenza Prodrug Oseltamivir
Background. Oseltamivir, a widely used anti-influenza drug, is hydrolytically activated by carboxylesterase 1 (CES1). The expression of this carboxylesterase is developmentally regulated. This study was performed to determine when after birth infants acquire competence of activating this prodrug. Methods. Liver tissue samples were collected and divided into 5 age groups: group 1 (1-31 d old), group 2 (35-70 d old), group 3 (89-119 d old), group 4 (123-198 d old), and group 5 (>18 years of age). These samples were analyzed for oseltamivir hydrolysis and CES1 expression. Results. Liver samples in group 1 expressed the lowest level of CES1 with the lowest hydrolytic activity toward oseltamivir. A 4-7-fold increase between groups 1 and 2 (1-31 vs 35-70 d of age) was detected in the hydrolysis and expression analyses, respectively. Liver samples in the other 3 pediatric groups (35-198 d of age) exhibited similar expression and hydrolysis levels. Overall, liver samples in group 1 had CES1 expression and hydrolysis levels that were 10% of those of adults, whereas liver samples in the other 3 pediatric groups had levels that were ∼50% of adult levels. Conclusions. The post-neonatal surge in CES1 expression ensures the hydrolytic capacity to be gained rapidly after birth in infants, but the larger variability during this period suggests that caution should be exercised on the extrapolated dosing regimens of ester drugs from other age group
Probing the Inner Disk Emission of the Herbig Ae Stars HD 163296 and HD 190073
The physical processes occurring within the inner few astronomical units of
proto-planetary disks surrounding Herbig Ae stars are crucial to setting the
environment in which the outer planet-forming disk evolves and put critical
constraints on the processes of accretion and planet migration. We present the
most complete published sample of high angular resolution H- and K-band
observations of the stars HD 163296 and HD 190073, including 30 previously
unpublished nights of observations of the former and 45 nights of the latter
with the CHARA long-baseline interferometer, in addition to archival VLTI data.
We confirm previous observations suggesting significant near-infrared emission
originates within the putative dust evaporation front of HD 163296 and show
this is the case for HD 190073 as well. The H- and K-band sizes are the same
within for HD 163296 and within for HD 190073. The
radial surface brightness profiles for both disks are remarkably Gaussian-like
with little or no sign of the sharp edge expected for a dust evaporation front.
Coupled with spectral energy distribution analysis, our direct measurements of
the stellar flux component at H and K bands suggest that HD 190073 is much
younger (<400 kyr) and more massive (~5.6 M) than previously thought,
mainly as a consequence of the new Gaia distance (891 pc).Comment: 19 pages, 6 figure
Preliminary imaging results from the second Mercury encounter
The second Mercury encounter has resulted in the acquisition of about 360 pictures of the south polar regions which provide a reliable cartographic and geologic tie between the two sides of the planet photographed on the first encounter. Stereoscopic coverage of large areas of the southern hemisphere was obtained by combining Mercury 1 and 2 pictures taken at different viewing angles. The south polar regions consist of heavily cratered terrain and intercrater plains interspersed with patches of smooth plains. No large areas of smooth plains similar to those surrounding Caloris occur in the south polar regions. No new types of terrain have been recognized, but lobate scarps are common. The second largest basin seen by Mariner 10 (∼600-km diameter) has been confirmed on the new photography. At high solar elevations the surface displays an abundance of rays and rayed craters
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