12,135 research outputs found
Freshwater immersion as a method to remove Urosalpinx cinerea and Ocinebrellus inornatus from mussel seed
A simple experiment to test whether immersion in freshwater for â€24 hours would kill two oyster drills, Urosalpinx cinerea and Ocinebrellus inornatus was conducted to test the proposal of using freshwater to rid mussel seed of the drills before translocation from the Oosterschelde to the Wadden Sea. Freshwater failed to kill any individuals of either species, but did cause them to detach from the substratum for the entire time of immersion. Immersion in freshwater is therefore not recommended as a method to control the drills. Rinsing in freshwater may be an option to remove the drills without killing them, but has no guarantee of 100 % success. Further investigation may result in the development of other treatment options
A Nonlinear Coupling Network to Simulate the Development of the r-mode Instablility in Neutron Stars I. Construction
R-modes of a rotating neutron star are unstable because of the emission of
gravitational radiation. We explore the saturation amplitudes of these modes
determined by nonlinear mode-mode coupling. Modelling the star as
incompressible allows the analytic computation of the coupling coefficients.
All couplings up to n=30 are obtained, and analytic values for the shear
damping and mode normalization are presented. In a subsequent paper we perform
numerical simulations of a large set of coupled modes.Comment: 15 pages 3 figure
Non conventional screening of the Coulomb interaction in low dimensional and finite size system
We study the screening of the Coulomb interaction in non polar systems by
polarizable atoms. We show that in low dimensions and small finite size systems
this screening deviates strongly from that conventionally assumed. In fact in
one dimension the short range interaction is strongly screened and the long
range interaction is anti-screened thereby strongly reducing the gradient of
the Coulomb interaction and therefore the correlation effects. We argue that
this effect explains the success of mean field single particle theories for
large molecules.Comment: 4 pages, 5 figure
How massless are massless fields in
Massless fields of generic Young symmetry type in space are analyzed.
It is demonstrated that in contrast to massless fields in Minkowski space whose
physical degrees of freedom transform in irreps of algebra,
massless mixed symmetry fields reduce to a number of irreps of
algebra. From the field theory perspective this means that not every massless
field in flat space admits a deformation to with the same number of
degrees of freedom, because it is impossible to keep all of the flat space
gauge symmetries unbroken in the AdS space. An equivalent statement is that,
generic irreducible AdS massless fields reduce to certain reducible sets of
massless fields in the flat limit. A conjecture on the general pattern of the
flat space limit of a general massless field is made. The example of
the three-cell ``hook'' Young diagram is discussed in detail. In particular, it
is shown that only a combination of the three-cell flat-space field with a
graviton-like field admits a smooth deformation to .Comment: 23 pages, LaTeX, a few typos correcte
Supertraces on the algebra of observables of the rational Calogero model based on the classical root system
A complete set of supertraces on the algebras of observables of the rational
Calogero models with harmonic interaction based on the classical root systems
of B_N, C_N and D_N types is found. These results extend the results known for
the case A_N. It is shown that there exist Q independent supertraces where
Q(B_N)=Q(C_N) is a number of partitions of N into a sum of positive integers
and Q(D_N) is a number of partitions of N into a sum of positive integers with
even number of even integers.Comment: 10 pages, LATE
Nonlinear Couplings of R-modes: Energy Transfer and Saturation Amplitudes at Realistic Timescales
Non-linear interactions among the inertial modes of a rotating fluid can be
described by a network of coupled oscillators. We use such a description for an
incompressible fluid to study the development of the r-mode instability of
rotating neutron stars. A previous hydrodynamical simulation of the r-mode
reported the catastrophic decay of large amplitude r-modes. We explain the
dynamics and timescale of this decay analytically by means of a single three
mode coupling. We argue that at realistic driving and damping rates such large
amplitudes will never actually be reached. By numerically integrating a network
of nearly 5000 coupled modes, we find that the linear growth of the r-mode
ceases before it reaches an amplitude of around 10^(-4). The lowest parametric
instability thresholds for the r-mode are calculated and it is found that the
r-mode becomes unstable to modes with 13<n<15 if modes up to n=30 are included.
Using the network of coupled oscillators, integration times of 10^6 rotational
periods are attainable for realistic values of driving and damping rates.
Complicated dynamics of the modal amplitudes are observed. The initial
development is governed by the three mode coupling with the lowest parametric
instability. Subsequently a large number of modes are excited, which greatly
decreases the linear growth rate of the r-mode.Comment: 3 figures 4 pages Submitted to PR
Three-body model calculations for 16C nucleus
We apply a three-body model consisting of two valence neutrons and the core
nucleus C in order to investigate the ground state properties and the
electronic quadrupole transition of the C nucleus. The discretized
continuum spectrum within a large box is taken into account by using a
single-particle basis obtained from a Woods-Saxon potential. The calculated
B(E2) value from the first 2 state to the ground state shows good agreement
with the observed data with the core polarization charge which reproduces the
experimental B(E2) value for C. We also show that the present
calculation well accounts for the longitudinal momentum distribution of
C fragment from the breakup of C nucleus. We point out that the
dominant ( configuration in the ground state of C plays a
crucial role for these agreement.Comment: 5 pages, 3 figures, 3 table
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