273 research outputs found
High-accuracy Penning trap mass measurements with stored and cooled exotic ions
The technique of Penning trap mass spectrometry is briefly reviewed
particularly in view of precision experiments on unstable nuclei, performed at
different facilities worldwide. Selected examples of recent results emphasize
the importance of high-precision mass measurements in various fields of
physics
Constrained von Neumann inequalities
An equivalent formulation of the von Neumann inequality states that the
backward shift on is extremal, in the sense that if is a
Hilbert space contraction, then for each polynomial
. We discuss several results of the following type : if is a Hilbert
space contraction satisfying some constraints, then restricted to a
suitable invariant subspace is an extremal operator. Several operator radii are
used instead of the operator norm. Applications to inequalities of coefficients
of rational functions positive on the torus are given.Comment: Preprint versio
Shocked Minerals in NWA 5011 L6 Chondritic Meteorite.
第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日(金) 国立国語研究所 2階講
Local demands on sterile neutrinos
In a model independent manner, we explore the local implications of a single
neutrino oscillation measurement which cannot be reconciled within a
three-neutrino theory. We examine this inconsistency for a single region of
baseline to neutrino energy . Assuming that sterile neutrinos account for
the anomaly, we find that the {\it local} demands of this datum can require the
addition to the theory of one to three sterile neutrinos. We examine the
constraints which can be used to determine when more than one neutrino would be
required. The results apply only to a given region of . The question of
the adequacy of the sterile neutrinos to satisfy a global analysis is not
addressed here. Finally, using the results of a 3+2 analysis, we indicate
values for unknown mixing matrix elements which would require two sterile
neutrinos due to local demands only.Comment: 11 pages, 1 figure, discussion adde
GINA - A Polarized Neutron Reflectometer at the Budapest Neutron Centre
The setup, capabilities and operation parameters of the neutron reflectometer
GINA, the recently installed "Grazing Incidence Neutron Apparatus" at the
Budapest Neutron Centre, are introduced. GINA, a dance-floor-type,
constant-energy, angle-dispersive reflectometer is equipped with a 2D
position-sensitive detector to study specular and off-specular scattering.
Wavelength options between 3.2 and 5.7 {\AA} are available for unpolarized and
polarized neutrons. Spin polarization and analysis are achieved by magnetized
transmission supermirrors and radio-frequency adiabatic spin flippers. As a
result of vertical focusing by the five-element (pyrolytic graphite)
monochromator the reflected intensity from a 20x20 mm sample has doubled. GINA
is dedicated to studies of magnetic films and heterostructures, but unpolarized
options for non-magnetic films, membranes and other surfaces are also provided.
Shortly after its startup, reflectivity values as low as 3x10-5 have been
measured on the instrument. The facility is now open for the international user
community, but its development is continuing mainly to establish new sample
environment options, the spin analysis of off-specularly scattered radiation
and further decrease of the background
MODELLING THE ELECTRON WITH COSSERAT ELASTICITY
Interactions between a finite number of bodies and the surrounding fluid, in a channel for instance, are investigated theoretically. In the planar model here the bodies or modelled grains are thin solid bodies free to move in a nearly parallel formation within a quasi-inviscid fluid. The investigation involves numerical and analytical studies and comparisons. The three main features that appear are a linear instability about a state of uniform motion, a clashing of the bodies (or of a body with a side wall) within a finite scaled time when nonlinear interaction takes effect, and a continuum-limit description of the body–fluid interaction holding for the case of many bodies
Semidefinite Representation of the -Ellipse
The -ellipse is the plane algebraic curve consisting of all points whose
sum of distances from given points is a fixed number. The polynomial
equation defining the -ellipse has degree if is odd and degree
if is even. We express this polynomial equation as
the determinant of a symmetric matrix of linear polynomials. Our representation
extends to weighted -ellipses and -ellipsoids in arbitrary dimensions,
and it leads to new geometric applications of semidefinite programming.Comment: 16 pages, 5 figure
Myosin and tropomyosin stabilize the conformation of formin-nucleated actin filaments
The conformational elasticity of the actin cytoskeleton is
essential for its versatile biological functions. Increasing
evidence supports that the interplay between the structural and
functional properties of actin filaments is finely regulated by
actin-binding proteins, however, the underlying mechanisms and
biological consequences are not completely understood. Previous
studies showed that the binding of formins to the barbed end
induces conformational transitions in actin filaments by making
them more flexible through long-range allosteric interactions.
These conformational changes are accompanied by altered
functional properties of the filaments. To get insight into the
conformational regulation of formin-nucleated actin structures,
in the present work we investigated in detail how binding
partners of formin-generated actin structures, myosin and
tropomyosin, affect the conformation of the formin-nucleated
actin filaments, using fluorescence spectroscopic approaches.
Time-dependent fluorescence anisotropy and temperature-dependent
Forster-type resonance energy transfer measurements revealed
that heavy meromyosin, similarly to tropomyosin, restores the
formin-induced effects and stabilizes the conformation of actin
filaments. The stabilizing effect of heavy meromyosin is
cooperative. The kinetic analysis revealed that despite the
qualitatively similar effects of heavy meromyosin and
tropomyosin on the conformational dynamics of actin filaments,
the mechanisms of the conformational transition is different for
the two proteins. Heavy meromyosin stabilizes the formin-
nucleated actin filaments in an apparently single-step reaction
upon binding, while the stabilization by tropomyosin occurs
after complex formation. These observations support the idea
that actin-binding proteins are key elements of the molecular
mechanisms that regulate the conformational and functional
diversity of actin filaments in living cells
Some remarks on quasi-Hermitian operators
A quasi-Hermitian operator is an operator that is similar to its adjoint in
some sense, via a metric operator, i.e., a strictly positive self-adjoint
operator. Whereas those metric operators are in general assumed to be bounded,
we analyze the structure generated by unbounded metric operators in a Hilbert
space. Following our previous work, we introduce several generalizations of the
notion of similarity between operators. Then we explore systematically the
various types of quasi-Hermitian operators, bounded or not. Finally we discuss
their application in the so-called pseudo-Hermitian quantum mechanics.Comment: 18page
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