2,118 research outputs found
New sub-millimeter heterodyne observations of CO and HCN in Titan's atmosphere with the APEX Swedish Heterodyne Facility Instrument
The origin of the atmosphere of the largest moon of Saturn, Titan, is poorly
understood and its chemistry is rather complicated. Ground-based
millimeter/sub-millimeter heterodyne spectroscopy resolves line shapes
sufficiently to determine information in Titan's atmospheric composition (on
vertical profiles and isotopic ratios). We test the capabilities of the Swedish
Heterodyne Facility Instrument (SHFI), Receiver APEX-1, together with the
Atacama Pathfinder EXperiment APEX 12-m telescope for Titan's atmospheric
observations. In particular we present sub-millimeter observations of the
CO(2-1) and HCN(3-2) lines of the Titan stratosphere with APEX, and with SHFI
taken during the Science Verification (SV) instrument phase on March and June
2008. With the help of appropriate radiative transfer calculations we
investigate the possibility to constrain the chemical concentrations and
optimize the performance of the APEX-1 instrument for inferring vertical
profiles of molecular components of the atmosphere of Titan.Comment: 13 pages, 5 figures, to appear in Advances in Geosciences (a refereed
publication of papers presented at Asia Oceanic Geophysical Society 6th
annual meeting 2009 in Singapore, a publication of World Scientific
Publication Company
Dipole excitation and geometry of borromean nuclei
We analyze the Coulomb breakup cross sections of Li and He nuclei
using a three-body model with a density-dependent contact interaction. We show
that the concentration of the B(E1) strength near the threshold can be well
reproduced with this model. With the help of the calculated B(E1) value, we
extract the root-mean-square (rms) distance between the core nucleus and the
center of mass of two valence neutrons without resorting to the sum rule, which
may suffer from unphysical Pauli forbidden transitions. Together with the
empirical rms distance between the neutrons obtained from the matter radius
study and also from the three-body correlation study in the break-up reaction,
we convert these rms distances to the mean opening angle between the valence
neutrons from the core nucleus. We find that the obtained mean opening angles
in Li and He agree with the three-body model predictions.Comment: 4 pages, 4 eps figure
Three-body model calculations for 16C nucleus
We apply a three-body model consisting of two valence neutrons and the core
nucleus C in order to investigate the ground state properties and the
electronic quadrupole transition of the C nucleus. The discretized
continuum spectrum within a large box is taken into account by using a
single-particle basis obtained from a Woods-Saxon potential. The calculated
B(E2) value from the first 2 state to the ground state shows good agreement
with the observed data with the core polarization charge which reproduces the
experimental B(E2) value for C. We also show that the present
calculation well accounts for the longitudinal momentum distribution of
C fragment from the breakup of C nucleus. We point out that the
dominant ( configuration in the ground state of C plays a
crucial role for these agreement.Comment: 5 pages, 3 figures, 3 table
Strong dineutron correlation in 8He and 18C
We study the spatial structure of four valence neutrons in the ground state
of He and C nuclei using a core+4 model. For this purpose, we
employ a density-dependent contact interaction among the valence neutrons, and
solve the five-body Hamiltonian in the Hartree-Fock-Bogoliubov (HFB)
approximation. We show that two neutrons with the coupled spin of =0 exhibit
a strong dineutron correlation around the surface of these nuclei, whereas the
correlation between the two dineutrons is much weaker. Our calculation
indicates that the probability of the (1p and [(1p
(p] configurations in the ground state wave function of He
nucleus is 34.9% and 23.7%, respectively. This is consistent with the recent
experimental finding with the He(He reaction, that is, the ground
state wave function of He deviates significantly from the pure
(1p structure.Comment: 10 pages, 9 figures, 3 table
Designing optimal discrete-feedback thermodynamic engines
Feedback can be utilized to convert information into useful work, making it
an effective tool for increasing the performance of thermodynamic engines.
Using feedback reversibility as a guiding principle, we devise a method for
designing optimal feedback protocols for thermodynamic engines that extract all
the information gained during feedback as work. Our method is based on the
observation that in a feedback-reversible process the measurement and the
time-reversal of the ensuing protocol both prepare the system in the same
probabilistic state. We illustrate the utility of our method with two examples
of the multi-particle Szilard engine.Comment: 15 pages, 5 figures, submitted to New J. Phy
Generalized Jarzynski Equality under Nonequilibrium Feedback Control
The Jarzynski equality is generalized to situations in which nonequilibrium
systems are subject to a feedback control. The new terms that arise as a
consequence of the feedback describe the mutual information content obtained by
measurement and the efficacy of the feedback control. Our results lead to a
generalized fluctuation-dissipation theorem that reflects the readout
information, and can be experimentally tested using small thermodynamic
systems. We illustrate our general results by an introducing "information
ratchet," which can transport a Brownian particle in one direction and extract
a positive work from the particle
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