8,560 research outputs found
Semirelativistic stability of N-boson systems bound by 1/r pair potentials
We analyze a system of self-gravitating identical bosons by means of a
semirelativistic Hamiltonian comprising the relativistic kinetic energies of
the involved particles and added (instantaneous) Newtonian gravitational pair
potentials. With the help of an improved lower bound to the bottom of the
spectrum of this Hamiltonian, we are able to enlarge the known region for
relativistic stability for such boson systems against gravitational collapse
and to sharpen the predictions for their maximum stable mass.Comment: 11 pages, considerably enlarged introduction and motivation,
remainder of the paper unchange
Global transposable characteristics in the yeast complete DNA sequence
Global transposable characteristics in the complete DNA sequence of the
Saccharomyces cevevisiae yeast is determined by using the metric representation
and recurrence plot methods. In the form of the correlation distance of
nucleotide strings, 16 chromosome sequences of the yeast, which are divided
into 5 groups, display 4 kinds of the fundamental transposable characteristics:
a short period increasing, a long quasi-period increasing, a long major value
and hardly relevant.Comment: 19 pages, 5 figures, 5 table
The Constitutive Relations and the Magnetoelectric Effect for Moving Media
In this paper the constitutive relations for moving media with homogeneous
and isotropic electric and magnetic properties are presented as the connections
between the generalized magnetization-polarization bivector and
the electromagnetic field F. Using the decompositions of F and ,
it is shown how the polarization vector P(x) and the magnetization vector M(x)
depend on E, B and two different velocity vectors, u - the bulk velocity vector
of the medium, and v - the velocity vector of the observers who measure E and B
fields. These constitutive relations with four-dimensional geometric
quantities, which correctly transform under the Lorentz transformations (LT),
are compared with Minkowski's constitutive relations with the 3-vectors and
several essential differences are pointed out. They are caused by the fact
that, contrary to the general opinion, the usual transformations of the
3-vectors , , , , etc. are
not the LT. The physical explanation is presented for the existence of the
magnetoelectric effect in moving media that essentially differs from the
traditional one.Comment: 18 pages, In Ref. [10] here, which corresponds to Ref. [18] in the
published paper in IJMPB, Z. Oziewicz's published paper is added. arXiv admin
note: text overlap with arXiv:1101.329
Corrections to Sirlin's Theorem in Chiral Perturbation Theory
We present the results of the first two-loop calculation of a form factor in
full Chiral Perturbation Theory. We choose a specific
linear combination of and form factors (the one
appearing in Sirlin's theorem) which does not get contributions from order
operators with unknown constants. For the charge radii, the correction to
the previous one-loop result turns out to be significant, but still there is no
agreement with the present data due to large experimental uncertainties in the
kaon charge radii.Comment: 6 pages, Latex, 2 LaTeX figure
Magnetization and magnetoresistance in insulating phases of SrFeO3-d
We report the synthesis and properties of two new insulating phases of
SrFeO3-d with introduction of oxygen deficiencies in metallic SrFeO3 ; one with
0.15 < d < 0.19 (sample A)and the other above d = 0.19 (sample B). Sample A
shows large negative magnetoresistance around the charged ordering (CO)
temperature with magnetic anomalies seen in the temperature dependent
resistivity,magnetization and M-H hysteresis loops. Sample B shows a smooth
insulating behavior with no thermal hysteresis in the resistivity and with a
small positive magnetoresistance. cac and cdc show multiple features associated
with a frustrated magnetic order (helical) due to competing ferro- and
antiferromagnetic interactions. The competing effects of ferro- and
antiferromagnetic phases extend up to T ~ 230 K revealing a new high
temperature scale in this system. These observations are discussed in the
context of magnetic interactions associated with the varying Fe4+/Fe3+ ratio.Comment: 11 pages, 4 figure
A general approximation of quantum graph vertex couplings by scaled Schroedinger operators on thin branched manifolds
We demonstrate that any self-adjoint coupling in a quantum graph vertex can
be approximated by a family of magnetic Schroedinger operators on a tubular
network built over the graph. If such a manifold has a boundary, Neumann
conditions are imposed at it. The procedure involves a local change of graph
topology in the vicinity of the vertex; the approximation scheme constructed on
the graph is subsequently `lifted' to the manifold. For the corresponding
operator a norm-resolvent convergence is proved, with the natural
identification map, as the tube diameters tend to zero.Comment: 19 pages, one figure; introduction amended and some references added,
to appear in CM
Measurement Properties of the Full and Brief Version of the Work Rehabilitation Questionnaire in Persons with Physical Disabilities
Purpose The Work Rehabilitation Questionnaire (WORQ) is a self-report vocational rehabilitation assessment. A comprehensive (WORQ-FULL) and a brief version (WORQ-BRIEF) are available. The purpose of this study was to investigate measurement properties of both versions in persons with physical disabilities. Methods Cross sectional and test-retest design. Adults with physical disabilities in vocational rehabilitation were included. Internal consistency (Cronbach's alpha), test-retest reliability (intra-class correlation; ICC), agreement between sessions (Bland-Altman Plots), criterion validity (ICC and agreement with Bland-Altman Plots between WORQ-FULL and WORQ-BRIEF) and convergent validity with the Work Ability Index -Single item (WAS) and the EuroQOL 5D-5L were analyzed. Results Out of the 91 individuals who agreed to participate, 74 (81%) returned questionnaire T1 and 49 (54%) participants returned questionnaire T2 within the maximum time interval (= 27 days). At T2, 28 (57%) participants reported no medical changes compared to T1. Median age was 49 (IQR 40-60), 57% were male, 47% had experienced a stroke and 27% a spinal cord injury (n = 49). Internal consistency was good: 0.95/0.95/0.94 for the WORQ-FULL and 0.88/0.89/0.85 for the WORQ-BRIEF (n = 74/n = 48/n = 28, respectively). Test-retest reliabilitywas good: ICC = 0.86/0.85 for the WORQ-FULL and ICC = 0.87/0.86 for the WORQ-BRIEF (n = 49/ n = 28). Bland Altman plots suggested a higher score at T1. As for criterion validity of the WORQ-FULL versus the WORQ-BRIEF, ICC was good (ICC = 0.84; n = 74), however Bland Altman plots indicated potential bias. Correlations with the WAS/EuroQOL 5D-5L were variable: r = -0.24/r = -0.57 (WORQ-FULL) and r = -0.28/-0.65 (WORQ-BRIEF). Conclusions The WORQ showed good internal consistency and test-retest reliability. Agreement demonstrated large score differences are needed to indicate change beyond random chance at individual level, whereas small changes are sufficient at group level. Criterion validity of the WORQ-FULL versus the WORQ-BRIEF was supported, however, agreement demonstrated moderate to large score differences are needed to indicate change beyond random chance at individual level, whereas small changes are sufficient at group level. This indicates the WORQ-FULL and WORQ-BRIEF are better not used interchangeably. Correlation analyses provided better insight in the validity of the WORQ. Convergent validity was supported for the WORQ-BRIEF with the EuroQoL 5D-5L (r = -0.65)
Third-order superintegrable systems separable in parabolic coordinates
In this paper, we investigate superintegrable systems which separate in
parabolic coordinates and admit a third-order integral of motion. We give the
corresponding determining equations and show that all such systems are
multi-separable and so admit two second-order integrals. The third-order
integral is their Lie or Poisson commutator. We discuss how this situation is
different from the Cartesian and polar cases where new potentials were
discovered which are not multi-separable and which are expressed in terms of
Painlev\'e transcendents or elliptic functions
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