1,926 research outputs found
Gamow-Teller strength distributions for double-beta-decaying nuclei within continuum-QRPA
A version of the pn-continuum-QRPA is outlined and applied to describe the
Gamow-Teller strength distributions for -decaying open-shell
nuclei. The calculation results obtained for the pairs of nuclei Cd-Sn
and Te-Xe are compared with available experimental data.Comment: 8 pages, 3 figures, To appear in the proceedings of "Nucleus-2007:
Fundamental problems of nuclear physics, atomic power engineering and nuclear
technologies" Voronezh, Russia, June 25-29, 200
Seasonal Water "Pump" in the Atmosphere of Mars: Vertical Transport to the Thermosphere
We present results of simulations with the Max Planck Institute general
circulation model (MPI-MGCM) implementing a hydrological cycle scheme. The
simulations reveal a seasonal water "pump" mechanism responsible for the upward
transport of water vapor. This mechanism occurs in high latitudes above
60 of the southern hemisphere at perihelion, when the upward branch of
the meridional circulation is particularly strong. A combination of the mean
vertical flux with variations induced by solar tides facilitates penetration of
water across the "bottleneck" at approximately 60 km. The meridional
circulation then transports water across the globe to the northern hemisphere.
Since the intensity of the meridional cell is tightly controlled by airborne
dust, the water abundance in the thermosphere strongly increases during dust
storms.Comment: 15 pages, 4 figure
Evaluation of the mean intensity of the P-odd mixing of nuclear compound states
A temperature version of the shell-optical-model approach for describing the
low-energy compound-to-compound transitions induced by external single-particle
fields is given. The approach is applied to evaluate the mean intensity of the
P-odd mixing of nuclear compound states. Unified description for the mixing and
electromagnetic transitions allows one to evaluate the mean intensity without
the use of free parameters. The valence-mechanism contribution to the mentioned
intensity is also evaluated. Calculation results are compared with the data
deduced from cross sections of relevant neutron-induced reactions.Comment: LaTeX, 10 page
Semimicroscopical description of the simplest photonuclear reactions accompanied by excitation of the giant dipole resonance in medium-heavy mass nuclei
A semimicroscopical approach is applied to describe photoabsorption and
partial photonucleon reactions accompanied by the excitation of the giant
dipole resonance (GDR). The approach is based on the continuum-RPA (CRPA) with
a phenomenological description for the spreading effect. The phenomenological
isoscalar part of the nuclear mean field, momentum-independent Landau-Migdal
particle-hole interaction, and separable momentum-dependent forces are used as
input quantities for the CRPA calculations. The experimental photoabsorption
and partial -reaction cross sections in the vicinity of the GDR are
satisfactorily described for Y, Ce and Pb target nuclei.
The total direct-neutron-decay branching ratio for the GDR in Ca and
Pb is also evaluated.Comment: 19 pages, 5 eps figure
Dynamic avalanche breakdown of a p-n junction: deterministic triggering of a plane streamer front
We discuss the dynamic impact ionization breakdown of high voltage p-n
junction which occurs when the electric field is increased above the threshold
of avalanche impact ionization on a time scale smaller than the inverse
thermogeneration rate. The avalanche-to-streamer transition characterized by
generation of dense electron-hole plasma capable to screen the applied external
electric field occurs in such regimes. We argue that the experimentally
observed deterministic triggering of the plane streamer front at the electric
field strength above the threshold of avalanche impact ionization but yet below
the threshold of band-to-band tunneling is generally caused by field-enhanced
ionization of deep-level centers. We suggest that the process-induced sulfur
centers and native defects such as EL2, HB2, HB5 centers initiate the front in
Si and GaAs structures, respectively. In deep-level free structures the plane
streamer front is triggered by Zener band-to-band tunneling.Comment: 4 pages, 2 figure
On Properties of the Isoscalar Giant Dipole Resonance
Main properties (strength function, energy-dependent transition density,
branching ratios for direct nucleon decay) of the isoscalar giant dipole
resonance in several medium-heavy mass spherical nuclei are described within a
continuum-RPA approach, taking into account the smearing effect. All model
parameters used in the calculations are taken from independent data.
Calculation results are compared with available experimental data.Comment: 12 pages, 2 figure
Inviting end-of-life talk in initial CALM therapy sessions: A conversation analytic study
OBJECTIVE: To examine how end-of-life talk is initiated in CALM therapy sessions with advanced cancer patients. METHODS: Conversation analysis was used to systematically examine the sequences where talk about death was raised in the first sessions of ten patients. RESULTS: Open questions about the patients' experiences, feelings or understanding in the context of talk about their troubles, were found to regularly elicit talk concerning end-of-life. These questions were designed in ways that invite patients to discuss troubling aspects of their cancer journey, without making discussion of this topic an interactional requirement. That is, the interactional work required to not engage in such talk is minimised. This choice is provided through the open question design, the degree to which negative feeling descriptors are specified, and the sequential context of the question. CONCLUSION: The analysis shows that therapists provide patients with the opportunity to talk about end-of-life in a way that is supportive of the therapeutic relationship. The readiness of patients to engage in end-of-life talk displays the salience of this topic, as well as the reflective space provided by CALM therapy. PRACTICE IMPLICATIONS: The results provide important insight into the process of CALM therapy, which can be used to guide training
Generating and sustaining long-lived spin states in 15N,15N′-azobenzene
Long-Lived spin States (LLSs) hold a great promise for sustaining non-thermal spin order and investigating various slow processes by Nuclear Magnetic Resonance (NMR) spectroscopy. Of special interest for such application are molecules containing nearly equivalent magnetic nuclei, which possess LLSs even at high magnetic fields. In this work, we report an LLS in trans-15N,15N′-azobenzene. The singlet state of the 15N spin pair exhibits a long-lived character. We solve the challenging problem of generating and detecting this LLS and further increase the LLS population by converting the much higher magnetization of protons into the 15N singlet spin order. As far as the longevity of this spin order is concerned, various schemes have been tested for sustaining the LLS. Lifetimes of 17 minutes have been achieved at 16.4 T, a value about 250 times longer than the longitudinal relaxation time of 15N in this magnetic field. We believe that such extended relaxation times, along with the photochromic properties of azobenzene, which changes conformation upon light irradiation and can be hyperpolarized by using parahydrogen, are promising for designing new experiments with photo-switchable long-lived hyperpolarization
The gamma-ray telescope Gamma-1
French and Soviet specialists have designed and built the gamma-ray telescope GAMMA-1 to detect cosmic gamma rays above 50 MeV. The sensitive area of the detector is 1400 sq cm, energy resolution is 30% at 300 MeV, and angular resolution 1.2 deg at 300 MeV (and less than 20' arc when a coded aperture mask is used). Results on calibration of the qualification model and Monte-Carlo calculations are presented
Structure and magnetic properties of mechanically alloyed Fe3-xAlCrx powders
Mixtures of elemental powders of Fe3-xAlCrx composition, where x ∈ (0.8 -1.2) were mechanically alloyed in the AGO-2U planetary ball mill. Obtained powders consist of particles with median size of 0.5-1.6 µm; increase in the Cr content results in the decrease in the size of particles. According to the X-ray data, all of the as-milled alloys possess a single-phase disordered b.c.c. structure. Increase in Cr content results in the decrease in the grain size of alloys, whereas the dependence of the lattice parameter on the chemical composition is not conclusive. Mössbauer spectra for most of the alloys shows that iron atoms in this alloys, in spite of the fact that only one phase was detected using the X-ray diffraction, exist both in ferromagnetic and non-ferromagnetic conditions
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