10,689 research outputs found
On the particle paths and the stagnation points in small-amplitude deep-water waves
In order to obtain quite precise information about the shape of the particle
paths below small-amplitude gravity waves travelling on irrotational deep
water, analytic solutions of the nonlinear differential equation system
describing the particle motion are provided. All these solutions are not closed
curves. Some particle trajectories are peakon-like, others can be expressed
with the aid of the Jacobi elliptic functions or with the aid of the
hyperelliptic functions. Remarks on the stagnation points of the
small-amplitude irrotational deep-water waves are also made.Comment: to appear in J. Math. Fluid Mech. arXiv admin note: text overlap with
arXiv:1106.382
Variational derivation of two-component Camassa-Holm shallow water system
By a variational approach in the Lagrangian formalism, we derive the
nonlinear integrable two-component Camassa-Holm system (1). We show that the
two-component Camassa-Holm system (1) with the plus sign arises as an
approximation to the Euler equations of hydrodynamics for propagation of
irrotational shallow water waves over a flat bed. The Lagrangian used in the
variational derivation is not a metric.Comment: to appear in Appl. Ana
Vaccination against Actinobacillus pleuropneumoniae as an alternative strategy to antimicrobial use in Danish pig herds
In this study the objective was to determine whether use of vaccination against Actinobacillus pleuropneumoniae (APP) had an effect on the antimicrobial consumption in finisher pigs, when compared to herds without vaccination. Based on observational data, we found that the change in antimicrobial consumption after vaccination was initiated was significant associated with the baseline antimicrobial use before vaccination. The decrease in antimicrobial used was more pronounced in vaccinated herds (N=101) when compared to herds without vaccination (N=320), indicating an effect of vaccination against APP on the antimicrobial consumption level
Breeding Yellow-flowered Alfalfa for Combined Wildlife Habitat and Forage Purposes
The objectives of our research were to: • evaluate a wide array of alfalfa germplasm containing varied levels of M. sativa ssp. falcata for traits related to suitability for stockpiling and nesting cover for game birds, •compare yellow-flowered cultivars and germplasms to conventional hay- and pasture-type cultivars for forage yield and quality in a delayed single-harvest / production system, and • develop, by phenotypic selection, one or more synthetic cultivars of yellow-flowered alfalfa that would have high forage yield, tolerance to potato leafhopper yellowing, prolonged flowering, and good leaf retention under a stockpiling management system until mid-July
Prey Coat Color Selection and Bioenergetics of Captive Screech Owls
Author Institution: The Institute of Environmental Sciences and Department of Zoology, Miami Universit
Ab-initio shell model with a core
We construct effective 2- and 3-body Hamiltonians for the p-shell by
performing 12\hbar\Omega ab initio no-core shell model (NCSM) calculations for
A=6 and 7 nuclei and explicitly projecting the many-body Hamiltonians onto the
0\hbar\Omega space. We then separate these effective Hamiltonians into 0-, 1-
and 2-body contributions (also 3-body for A=7) and analyze the systematic
behavior of these different parts as a function of the mass number A and size
of the NCSM basis space. The role of effective 3- and higher-body interactions
for A>6 is investigated and discussed
Requirements for contractility in disordered cytoskeletal bundles
Actomyosin contractility is essential for biological force generation, and is
well understood in highly organized structures such as striated muscle.
Additionally, actomyosin bundles devoid of this organization are known to
contract both in vivo and in vitro, which cannot be described by standard
muscle models. To narrow down the search for possible contraction mechanisms in
these systems, we investigate their microscopic symmetries. We show that
contractile behavior requires non-identical motors that generate large enough
forces to probe the nonlinear elastic behavior of F-actin. This suggests a role
for filament buckling in the contraction of these bundles, consistent with
recent experimental results on reconstituted actomyosin bundles.Comment: 10 pages, 6 figures; text shortene
Self-organization and Mechanical Properties of Active Filament Bundles
A phenomenological description for active bundles of polar filaments is
presented. The activity of the bundle results from crosslinks, that induce
relative displacements between the aligned filaments. Our generic description
is based on momentum conservation within the bundle. By specifying the internal
forces, a simple minimal model for the bundle dynamics is obtained, capturing
generic dynamic behaviors. In particular, contracted states as well as solitary
and oscillatory waves appear through dynamic instabilities. The introduction of
filament adhesion leads to self-organized persistent filament transport.
Furthermore, calculating the tension, homogeneous bundles are shown to be able
to actively contract and to perform work against external forces. Our
description is motivated by dynamic phenomena in the cytoskeleton and could
apply to stress-fibers and self-organization phenomena during cell-locomotion.Comment: 19 pages, 10 figure
Effective operators from exact many-body renormalization
We construct effective two-body Hamiltonians and E2 operators for the p-shell
by performing ab initio no-core shell model (NCSM) calculations
for A=5 and A=6 nuclei and explicitly projecting the many-body Hamiltonians and
E2 operator onto the space. We then separate the effective E2
operator into one-body and two-body contributions employing the two-body
valence cluster approximation. We analyze the convergence of proton and neutron
valence one-body contributions with increasing model space size and explore the
role of valence two-body contributions. We show that the constructed effective
E2 operator can be parametrized in terms of one-body effective charges giving a
good estimate of the NCSM result for heavier p-shell nuclei.Comment: 9 pages, 8 figure
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