625 research outputs found
Pauli-principle driven correlations in four-neutron nuclear decays
Mechanism of simultaneous non-sequential four-neutron () emission (or
`true' -decay) has been considered in phenomenological five-body approach.
This approach is analogous to the model of the direct decay to the continuum
often applied to - and -decays. It is demonstrated that -decay
fragments should have specific energy and angular correlations reflecting
strong spatial correlations of `valence' nucleons orbiting in their
-precursors. Due to the Pauli exclusion principle, the valence neutrons are
pushed to the symmetry-allowed configurations in the -precursor structure,
which causes a `Pauli focusing' effect. Prospects of the observation of the
Pauli focusing have been considered for the -precursors H and O.
Fingerprints of their nuclear structure or/and decay dynamics are predicted
Anomalous population of He states in reactions with Li
Structure with the lowest energy observed in the He spectrum populated
in the proton knockout reaction with Li beam has a peak at
MeV. This peak is usually interpreted as a resonant ground state of
He. Our theoretical calculations indicate that this peak is likely to be
a pileup of , , and excitations with very similar shapes. %We
predict a very specific nature of the excitation in He. Moreover,
the ``soft'' excitation appears to be the lowest one in energy. Such an
anomalous continuum response is traced to the halo structure of Li
providing extreme low energy shift to all the expected continuum excitations.
Competitions of the initial state structure (ISS) and the final state
interaction (FSI) effects on the spectrum and three-body correlations in
He are discussed. Analogous effect of the extreme low-energy shift could
also be expected in other cases of emitters populated in reactions with
halo nuclei. Simplified example of the He spectrum in knockout
from Be, is given. We also discuss limits on the properties of He
stemming from the observed He spectrum.Comment: 10 pages, 13 figure
Dephasing time and magnetoresistance of two-dimensional electron gas in spatially modulated magnetic fields
The effect of a spatially modulated magnetic field on the weak localization
phenomenon in two-dimensional electron gas (2DEG) is studied. Both the
dephasing time and magnetoresistance are shown to reveal a nontrivial
behavior as functions of the characteristics of magnetic field profiles. The
magnetic field profiles with rather small spatial scales and modulation
amplitudes such that are characterized by the
dephasing rate . The increase in the flux value
results in a crossover to a standard linear dependence
. Applying an external homogeneous magnetic field
one can vary the local dephasing time in the system and affect the resulting
average transport characteristics. We have investigated the dependence of the
average resistance vs the field for some generic systems and predict a
possibility to observe a positive magnetoresistance at not too large
values. The resulting dependence of the resistance vs should reveal a peak
at the field values .Comment: 12 pages, 5 figure
Incidence of "quasi-ditags" in catalogs generated by Serial Analysis of Gene Expression (SAGE)
BACKGROUND: Serial Analysis of Gene Expression (SAGE) is a functional genomic technique that quantitatively analyzes the cellular transcriptome. The analysis of SAGE libraries relies on the identification of ditags from sequencing files; however, the software used to examine SAGE libraries cannot distinguish between authentic versus false ditags ("quasi-ditags"). RESULTS: We provide examples of quasi-ditags that originate from cloning and sequencing artifacts (i.e. genomic contamination or random combinations of nucleotides) that are included in SAGE libraries. We have employed a mathematical model to predict the frequency of quasi-ditags in random nucleotide sequences, and our data show that clones containing less than or equal to 2 ditags (which include chromosomal cloning artifacts) should be excluded from the analysis of SAGE catalogs. CONCLUSIONS: Cloning and sequencing artifacts contaminating SAGE libraries could be eliminated using simple pre-screening procedure to increase the reliability of the data
Updated analysis of NN elastic scattering to 3 GeV
A partial-wave analysis of NN elastic scattering data has been updated to
include a number of recent measurements. Experiments carried out at the Cooler
Synchrotron (COSY) by the EDDA Collaboration have had a significant impact
above 1 GeV. Results are discussed in terms of the partial-wave and
direct-reconstruction amplitudes.Comment: 16 pages, 14 figures, 2 tables; Fig 10 error corrected; Accepted for
publication in Physical Review
TO THE QUESTION OF THE INFLUENCE OF A SILANOL COVER ON THE PROTOLYTIC PROPERTIES OF AMINOPROPYL SILICA GELS
A method for describing and predicting protolytic and complex-forming properties of the surface of functionalized sorbents based on silica gels with grafted nitrogen-containing groups is proposed. The method is considered on the example of protonation of aminopropyl silica. Received curves of potentiometric titration of aminopropyl silica gels with hydrochloric acid
Variable Star Candidates in an ACS Field of M31
A search for variable stars is performed using two epochs of Hubble Space
Telescope (HST) Advanced Camera for Surveys (ACS) imaging data for a 9.28
square arcminute portion of M31. This data set reveals 254 sources that vary by
at least 4-sigma between epochs. The positions and 2-epoch B-band (equivalent)
photometry of these sources are presented. The photometry suggests that this
catalog includes most of the RR Lyrae population of this portion of M31.Comment: 22 pages, 3 tables, 5 figures, accepted for publication in A
HETEROGENEOUS LITHOSPHERIC STRUCTURE OF THE FENNOSCANDIAN SHIELD: SEISMIC DATA
A generalization has been obtained based on the data for deep seismic studies on longitudinal DSS profiles (explosion seismology) and seismological evidence found for local and distant earthquakes (earthquake seismology) in the Fennoscandian Shield over the past 40 years. This provided an opportunity to obtaine quantitative data on the horizontal and vertical heterogeneities of the lithosphere. 3D seismological models were first constructed for the individual parts of the Fennoscandian Shield which show that the crystalline crust structure acquires a block hierarchy pattern, with no persistent seismic boundaries found within the entire shield. The upper crust is characterized by the local occurrence of both waveguides and high-velocity zones correlated with geological bodies. The structural plans of the velocity isolines of various deep sections were found to be inconsistent. It has been proved that major geotectonic provinces have a thick crust and that the Early Proterozoic volcanogenic belts are characterized by elevated velocities and a large crustal thickness. In the upper mantle of the Fennoscandian Shield there were identified the layers with anomalously high velocities. No robust evidence was found for a waveguide, which is sometimes related to the concept of the lithosphere
Hadronic Regge Trajectories: Problems and Approaches
We scrutinized hadronic Regge trajectories in a framework of two different
models --- string and potential. Our results are compared with broad spectrum
of existing theoretical quark models and all experimental data from PDG98. It
was recognized that Regge trajectories for mesons and baryons are not straight
and parallel lines in general in the current resonance region both
experimentally and theoretically, but very often have appreciable curvature,
which is flavor-dependent. For a set of baryon Regge trajectories this fact is
well described in the considered potential model. The standard string models
predict linear trajectories at high angular momenta J with some form of
nonlinearity at low J.Comment: 15 pages, 9 figures, LaTe
The relationship of time perspective and subjective perceptions of students as the empirical base for individualization of the educational path
The significance of the investigated problem is stipulated by the need in practicing individualization of vocational educational process in the continuing education and lack of scientific and methodological support of its accompaniment. The purpose of the article is to substantiate the subjective perceptions and temporal perspective as the empirical bases of individualization of vocational and educational process. The leading method of research of this problem is a questionnaire that allows to identify the level of demonstration time perspectives (adapted technique ZTPI) and differentiate subjective judgments about the system of vocational education, professional self-determination process (questionnaire). The results of empirical study of time perspective, the subjective perception of vocational education and retrospective-prospective (forward-looking) aspects of professional self-determination, as well as their relationship with students are presented and discussed in the article. The results can be taken into account in the scientific and methodological support of individualization of vocational and educational process and in applied methods of formation of individual educational paths in vocational education. © 2016 Zavodchikov et al
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