755,258 research outputs found
Dependence of nuclear binding on hadronic mass variation
We examine how the binding of light () nuclei depends on possible
variations of hadronic masses, including meson, nucleon, and nucleon-resonance
masses. Small variations in hadronic masses may have occurred over time; the
present results can help evaluate the consequences for big bang
nucleosynthesis. Larger variations may be relevant to current attempts to
extrapolate properties of nucleon-nucleon interactions from lattice QCD
calculations. Results are presented as derivatives of the energy with respect
to the different masses so they can be combined with different predictions of
the hadronic mass-dependence on the underlying current-quark mass . As an
example, we employ a particular set of relations obtained from a study of
hadron masses and sigma terms based on Dyson-Schwinger equations and a
Poincar\'{e}-covariant Faddeev equation for confined quarks and diquarks. We
find that nuclear binding decreases moderately rapidly as the quark mass
increases, with the deuteron becoming unbound when the pion mass is increased
by 60% (corresponding to an increase in of 2.5).
In the other direction, the dineutron becomes bound if the pion mass is
decreased by 15% (corresponding to a reduction of by 30%). If
we interpret the disagreement between big bang nucleosynthesis calculations and
measurements to be the result of variation in , we obtain an estimate
where (the expected
accuracy in is about a factor of 2). The result is dominated by Li
data.Comment: 28 pages including 3 figures v2:additional citations/acknowledgments
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Unitary interpolants and factorization indices of matrix functions
For an bounded matrix function we study unitary
interpolants , i.e., unitary-valued functions such that , . We are looking for unitary interpolants for which
the Toeplitz operator is Fredholm. We give a new approach based on
superoptimal singular values and thematic factorizations. We describe
Wiener--Hopf factorization indices of in terms of superoptimal singular
values of and thematic indices of , where is a superoptimal
approximation of by bounded analytic matrix functions. The approach
essentially relies on the notion of a monotone thematic factorization
introduced in [AP]. In the last section we discuss hereditary properties of
unitary interpolants. In particular, for matrix functions of class
H^\be+C we study unitary interpolants of class .Comment: 20 page
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Rabbit behaviour research in Australia and its relevance in control operations
Research in Australia on the behaviour of wild rabbits has provided a basis for improvements in the tactics and strategy of control. As the warren is a central focus for growth and survival of a population, a program for effective control or eradication should aim at making the warren unavailable to rabbits. Enclosure studies of behaviour suggested that poisoning would be much more effective when carried out in the non-breeding season. This has been confirmed in field trials. The behavioural importance of the odour-producing inguinal, submandibular, and anal glands is emphasized. It is suggested that further studies of these glands may provide insights for the development of repellents or attractants
Computer circuit card puller
The invention generally relates to hand tools, and more particularly to an improved device for facilitating removal of printed circuit cards from a card rack characterized by longitudinal side rails arranged in a mutually spaced parallelism and a plurality of printed circuit cards extended between the rails of the rack
Magnetic and magnetoelectric studies in pure and cation doped BiFeO3
We report magnetic and magnetoelectric studies on BiFeO3 and divalent cation
(A) suvtitute Bi0.7A0.3FeO3 (A = Sr,Ba, and Sr0.5Ba0.5). It is shown that the
rapid increase of magnetization at the Neel temperature (TN = 642 K) is
suppressed in the co-doped compound A = Sr0.5Ba0.5. All the divalent subtituted
compounds show enhanced magnetization and hysteresis loop. Both longitudinal
and transverse magnetoelectric coefficients were measured using the dynamical
lock-in technique. The co-doped compound shows the highest magnetoelectric
coefficient at room temperature although it is not the compound with the
highest saturation magnetization. It is found that as the size of the A-site
cation increses, the transverse magnetoelectric coeffient increases and exceeds
the longitudinal magnetoelectric coefficient. It is suggested that changes in
magnetic domain structure and magnetostriction are possible reasons for the
observed changes in the magnetoelectric coefficients.Comment: 16 pages, 6 figur
Electrical, magnetic, magnetodielectric and magnetoabsorption studies in multiferroic GaFeO3
We report electrical, magnetic, magnetodielectric and magnetoabsorption
properties of a polycrystalline GaFeO3. The resistivity measurement shows that
the sample is highly insulating below 200 K and the resistivity above 200 K
obey the Arrhenius law with an activation energy of Ea = 0.67 eV. An anomaly
occurs in the temperature dependence of permittivity (e) near the ferrimagnetic
transition temperature (TC = 228 K) in a zero magnetic field and it is
suppressed under H = 60 mT which indicates a possible magnetoelectric coupling
in GaFeO3 with a fractional change of de/e = -1.8% at 60 mT around TC. The
coercivity (HC) of the sample increases dramatically with lowering temperature
below 200 K from 0.1 T at 200 K to 0.9 T at 5 K. Magnetoabsorption was studied
with a LC resonance technique and we found a close correlation between the
shift in the resonance frequency due to applied magnetic field and the coercive
field measured using dc magnetization measurements. Our results obtained with
multiple techniques suggest that GaFeO3 is an interesting ferrimagnet with
potential applications in future multiferroic devices.Comment: 22 pages, 6 figures. submitted to J. Appl. Phy
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