1,986 research outputs found
Description of rotating nuclei in terms of isovector pairing
A systematic investigation of the rotating even-even nuclei in the mass
region has been performed within the frameworks of the Cranked
Relativistic Mean field, Cranked Relativistic Hartree Bogoliubov theories and
cranked Nilsson-Strutinsky approach. Most of the experimental data is well
accounted for in the calculations. The present study suggests that there is
strong isovector -pair field at low spin, the strength of which is defined
by the isospin symmetry. At high spin, the isovector pair field is destroyed
and the data are well described by the calculations assuming zero pairing. No
clear evidence for the existence of the isoscalar -pairing has been
obtained in the present investigation.Comment: 20 pages + 19 figures, submitted to Phys. Rev.
Dichotomous Hamiltonians with Unbounded Entries and Solutions of Riccati Equations
An operator Riccati equation from systems theory is considered in the case
that all entries of the associated Hamiltonian are unbounded. Using a certain
dichotomy property of the Hamiltonian and its symmetry with respect to two
different indefinite inner products, we prove the existence of nonnegative and
nonpositive solutions of the Riccati equation. Moreover, conditions for the
boundedness and uniqueness of these solutions are established.Comment: 31 pages, 3 figures; proof of uniqueness of solutions added; to
appear in Journal of Evolution Equation
Molecular structure of highly-excited resonant states in Mg and the corresponding Be+O and C+C decays
Exotic Be and C decays from high-lying resonances in Mg are
analyzed in terms of a cluster model. The calculated quantities agree well with
the corresponding experimental data. It is found that the calculated decay
widths are very sensitive to the angular momentum carried by the outgoing
cluster. It is shown that this property makes cluster decay a powerful tool to
determine the spin as well as the molecular structures of the resonances.Comment: 17 pages, no figur
Averaging techniques for steady and unsteady calculations of a transonic fan stage
It is often desirable to characterize a turbomachinery flow field with a few lumped parameters such as total pressure ratio or stage efficiency. Various averaging schemes may be used to compute these parameters. The momentum, energy, and area averaging schemes are described and compared. The schemes were compared for two computed solutions of the midspan section of a transonic fan stage: a steady averaging-plane solution in which average rotor outflow conditions were used as stator inflow conditions, and an unsteady rotor-stator interaction solution. The solutions were computed on identical grids using similar Navier-Stokes codes and an algebraic turbulence model. The unsteady solution is described, some unsteady flow phenomena are discussed, and the steady pressure distributions are compared. Despite large unsteady pressure fluctuations on the stator surface, the steady pressure distribution matched the average unsteady distribution almost exactly. Stator wake profiles, stator loss coefficient, and stage efficiency were computed for the two solutions with the three averaging schemes and are compared. In general, the energy averaging scheme gave good agreement between the averaging-plane solution and the time-averaged unsteady solution, even though certain phenomena due to unsteady wake migration were neglected
Spontaneous Cdc42 polarization independent of GDI-mediated extraction and actin-based trafficking.
The small Rho-family GTPase Cdc42 is critical for cell polarization and polarizes spontaneously in absence of upstream spatial cues. Spontaneous polarization is thought to require dynamic Cdc42 recycling through Guanine nucleotide Dissociation Inhibitor (GDI)-mediated membrane extraction and vesicle trafficking. Here, we describe a functional fluorescent Cdc42 allele in fission yeast, which demonstrates Cdc42 dynamics and polarization independent of these pathways. Furthermore, an engineered Cdc42 allele targeted to the membrane independently of these recycling pathways by an amphipathic helix is viable and polarizes spontaneously to multiple sites in fission and budding yeasts. We show that Cdc42 is highly mobile at the membrane and accumulates at sites of activity, where it displays slower mobility. By contrast, a near-immobile transmembrane domain-containing Cdc42 allele supports viability and polarized activity, but does not accumulate at sites of activity. We propose that Cdc42 activation, enhanced by positive feedback, leads to its local accumulation by capture of fast-diffusing inactive molecules
Glasslike Arrest in Spinodal Decomposition as a Route to Colloidal Gelation
Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich
and colloid-poor regions. Gelation results when interconnected colloid-rich
regions solidify. We show that this occurs when these regions undergo a glass
transition, leading to dynamic arrest of the spinodal decomposition. The
characteristic length scale of the gel decreases with increasing quench depth,
and the nonergodicity parameter exhibits a pronounced dependence on scattering
vector. Mode coupling theory gives a good description of the dynamics, provided
we use the full static structure as input.Comment: 14 pages, 4 figures; replaced with published versio
A note on the uniqueness of D=4 N=1 Supergravity
We investigate in 4 spacetime dimensions, all the consistent deformations of
the lagrangian , which is the sum of the
Pauli-Fierz lagrangian for a free massless spin 2 field and the
Rarita-Schwinger lagrangian for a free massless spin 3/2
field. Using BRST cohomogical techniques, we show, under the assumptions of
locality, Poincar\'e invariance, conservation of the number of gauge symmetries
and the number of derivatives on each fields, that N=1 D=4 supergravity is the
only consistent interaction between a massless spin 2 and a massless spin 3/2
field. We do not assume general covariance. This follows automatically, as does
supersymmetry invariance. Various cohomologies related to conservations laws
are also given.Comment: 22+1 pages, LaTeX. References adde
The Borrego Mountain, California, earthquake of 9 April 1968: A preliminary report
The largest earthquake to hit California in more than 15 years occurred at
02:28:58.9 GCT on 9 April 1968 near Borrego Mountain, on the western edge of
the Imperial Valley. The Seismological Laboratory at Pasadena has tentatively
assigned the shock a magnitude of 6.5, an epicentral location of 33 ° 08.8' N, 116 °
07.5' W, and a focal depth of 20 km. The earthquake was felt throughout most
of southern California and adjacent areas, but the absence of severe damage and
casualties was in large part due to the relatively undeveloped nature of the epicentral
region. Indeed, it would have been difficult to pick a location in the southernmost
part of the State more remote from centers of population
A hybrid version of the tilted axis cranking model and its application to ^{128}Ba
A hybrid version the deformed nuclear potential is suggested, which combines
a spherical Woods Saxon potential with a deformed Nilsson potential. It removes
the problems of the conventional Nilsson potential in the mass 130 region.
Based on the hybrid potential, tilted axis cranking calculations are carried
out for the magnetic dipole band in ^{128}Ba.Comment: 10 pages 6 figure
Linear Relaxation Processes Governed by Fractional Symmetric Kinetic Equations
We get fractional symmetric Fokker - Planck and Einstein - Smoluchowski
kinetic equations, which describe evolution of the systems influenced by
stochastic forces distributed with stable probability laws. These equations
generalize known kinetic equations of the Brownian motion theory and contain
symmetric fractional derivatives over velocity and space, respectively. With
the help of these equations we study analytically the processes of linear
relaxation in a force - free case and for linear oscillator. For a weakly
damped oscillator we also get kinetic equation for the distribution in slow
variables. Linear relaxation processes are also studied numerically by solving
corresponding Langevin equations with the source which is a discrete - time
approximation to a white Levy noise. Numerical and analytical results agree
quantitatively.Comment: 30 pages, LaTeX, 13 figures PostScrip
- …