380 research outputs found
Interaction of the NO 3pπ (C 2Π) Rydberg state with RG (RG = Ne, Kr, and Xe): potential energy surfaces and spectroscopy
We present new potential energy surfaces for the interaction of NO(C 2Π) with each of Ne, Kr, and Xe. The potential energy surfaces have been calculated using second order Møller-Plesset perturbation theory, exploiting a procedure to converge the reference Hartree-Fock wavefunction for the excited states: the maximum overlap method. The bound rovibrational states obtained from the surfaces are used to simulate the electronic spectra and their appearance is in good agreement with available (2+1) REMPI spectra. We discuss the assignment and appearance of these spectra, comparing to that of NO-Ar
Ab Initio Calculations of the Walls Shear Strength of Carbon Nanotubes
The dependence of the energy of interwall interaction in double-walled carbon
nanotubes (DWNT) on the relative position of walls has been calculated using
the density functional method. This dependence is used to evaluate forces that
are necessary for the relative telescopic motion of walls and to calculate the
shear strength of DWNT for the relative sliding of walls along the nanotube
axis and for their relative rotation about this axis. The possibility of
experimental verification of the obtained results is discussed.Comment: 4 pages, 1 figur
Coulomb excitation of exotic nuclei at the R3B-LAND setup
Exotic Ni isotopes have been measured at the R3B-LAND setup at GSI in
Darmstadt, using Coulomb excitation in inverse kinematics at beam energies
around 500 MeV/u. As the experimental setup allows kinematically complete
measurements, the excitation energy was reconstructed using the invariant mass
method. The GDR and additional low-lying strength have been observed in 68Ni,
the latter exhausting 4.1(1.9)% of the E1 energy-weighted sum rule. Also, the
branching ratio for the non-statistical decay of the excited 68Ni nuclei was
measured and amounts to 24(4)%.Comment: 11 pages, 7 figures. Invited Talk given at the 11th International
Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA,
May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of
Physics: Conference Series (JPCS
Coulomb breakup of neutron-rich Na isotopes near the island of inversion
First results are reported on the ground state configurations of the
neutron-rich Na isotopes, obtained via Coulomb dissociation (CD)
measurements as a method of the direct probe. The invariant mass spectra of
those nuclei have been obtained through measurement of the four-momentum of all
decay products after Coulomb excitation on a target at energies of
400-430 MeV/nucleon using FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated
Coulomb-dissociation cross-sections (CD) of 89 mb and 167 mb up to
excitation energy of 10 MeV for one neutron removal from Na and
Na respectively, have been extracted. The major part of one neutron
removal, CD cross-sections of those nuclei populate core, in its' ground state.
A comparison with the direct breakup model, suggests the predominant occupation
of the valence neutron in the ground state of Na and
Na is the orbital with small contribution in the
-orbital which are coupled with ground state of the core. The ground state
configurations of these nuclei are as Na_{gs (1^+)\otimes\nu_{s,d} and
Na, respectively. The ground state spin
and parity of these nuclei, obtained from this experiment are in agreement with
earlier reported values. The spectroscopic factors for the valence neutron
occupying the and orbitals for these nuclei in the ground state have
been extracted and reported for the first time. A comparison of the
experimental findings with the shell model calculation using MCSM suggests a
lower limit of around 4.3 MeV of the sd-pf shell gap in Na.Comment: Modified version of the manuscript is accepted for publication in
Journal of Physics G, Jan., 201
A density functional theory based analysis of photoinduced electron transfer in a triazacryptand based K+ sensor
The electronic structure and photoinduced electron transfer processes in a K+ fluorescent sensor that comprises a 4-amino-naphthalimide derived fluorophore with a triazacryptand lig- and is investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) in order to rationalise the function of the sensor. The absorption and emission energies of the intense electronic excitation localised on the fluorophore are accurately described using a ∆SCF Kohn-Sham DFT approach, which gives excitation energies closer to experiment than TDDFT. Analysis of the molecular orbital diagram arising from DFT calculations for the isolated molecule or with implicit solvent cannot account for the function of the sensor and it is necessary to consider the relative energies of the electronic states formed from the local excitation on the fluorophore and the lowest fluorophore→chelator charge transfer state. The inclusion of solvent in these calculations is critical since the strong interaction of the charge transfer state with the solvent lowers it energy below the local fluorophore excited state making a reductive photoinduced electron transfer possible in the absence of K+, while no such process is possible when the sensor is bound to K+. The rate of electron transfer is quantified using Marcus theory, which gives a rate of electron transfer of k_ET=5.98 x 10^6 s−1
Measurements of proton-induced reactions on ruthenium-96 in the ESR at GSI
8th International Conference on Nuclear Physics at Storage Rings Stori11, October 9-14, 2011 Laboratori Nazionale di Frascati, Italy.
Storage rings offer the possibility of measuring proton- and alpha-induced reactions in inverse kinematics. The combination of this approachwith a radioactive beamfacility allows, in principle, the determination of the respective cross sections for radioactive isotopes. Such data are highly desired for a better understanding of astrophysical nucleosynthesis processes like the p-process. A pioneering experiment has been performed at the Experimental Storage Ring (ESR) at GSI using a stable 96Ru beam at 9-11 AMeV and a hydrogen target. Monte-Carlo simulations of the experiment were made using the Geant4 code. In these simulations, the experimental setup is described in detail and all reaction channels can be investigated. Based on the Geant4 simulations, a prediction of the shape of different spectral components can be performed. A comparison of simulated predictions with the experimental results shows a good agreement and allows the extraction of the cross section
Measurement of the 92,93,94,100Mo(γ,n) reactions by Coulomb Dissociation
The Coulomb Dissociation (CD) cross sections of the stable isotopes 92,94,100Mo and of the unstable isotope 93Mo were measured at the LAND/R3B setup at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Experimental data on these isotopes may help to explain the problem of the underproduction of 92,94Mo and 96,98Ru in the models of p-process nucleosynthesis. The CD cross sections obtained for the stable Mo isotopes are in good agreement with experiments performed with real photons, thus validating the method of Coulomb Dissociation. The result for the reaction 93Mo(γ,n) is especially important since the corresponding cross section has not been measured before. A preliminary integral Coulomb Dissociation cross section of the 94Mo(γ,n) reaction is presented. Further analysis will complete the experimental database for the (γ,n) production chain of the p-isotopes of molybdenum
Epidemiology of drug-resistant tuberculosis among children and adolescents in South Africa, 2005-2010
OBJECTIVE : To describe the demographic and clinical characteristics of children and adolescents diagnosed with resistance to any anti-tuberculosis drug (drug-resistant tuberculosis; DR-TB) in South Africa. DESIGN : We retrospectively reviewed medical records of all children (<13 years) and adolescents (13 to <18 years) with DR-TB at specialty hospitals in four South African provinces from 2005 to 2010. RESULTS : During the review period, 774 children and adolescents (median age 11.3 years) were diagnosed with DR-TB at selected facilities. A high proportion of patients had a history of previous TB treatment (285/631; 45.2%), human immunodeficiency virus (HIV) infection (375/685; 54.7%), contact with a TB case (347/454; 76.4%), and smear-positive (443/729; 60.8%), cavitary (253/680, 38.7%) disease. Eighty-two per cent of patients with HIV infection received antiretroviral therapy. Of 626 patients diagnosed with multidrug-resistant TB (MDR-TB), 561 (89.6%) received a regimen consistent with national guidelines; the median length of treatment was 22 months (IQR 16-25). Among 400 patients with any DR-TB and a known outcome, 20.3% died during treatment. CONCLUSION : Pediatric DR-TB in these provinces is characterized by complex clinical features at diagnosis, with one in five children dying during treatment. History of previous treatment and contact with a TB patient indicate opportunities for earlier diagnosis and treatment to improve outcomes.U.S. Agency for International Development and U.S. Centers for Disease Control and Prevention, with additional support from the South Africa National Institute for Communicable Diseases and the South African Medical Research Council.http://www.ingentaconnect.comcontent/iuatld/ijtld2015-12-01hb201
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