69 research outputs found
Emergency Mosquito Control on a Selected Area in Eastern North Carolina After Hurricane Irene
Natural disasters such as hurricanes may contribute to mosquito abundance and, consequently, arbovirus transmission risk. In 2011, flooding from Hurricane Irene in eastern North Carolina (NC) resulted in increased mosquito populations that hindered recovery efforts. Budget shortfalls in NC have reduced the functionality of long-term mosquito surveillance and control programs; hence, many counties rely on the Federal Emergency Management Agency for post-disaster mosquito control. This pilot study examines mosquito abundance pre- and post-aerial insecticide spraying at eight study sites in Washington and Tyrrell Counties in rural eastern NC after Hurricane Irene. Percent change was calculated and compared for traps in areas that received aerial pesticide application and those that did not. Traps in spray zones show decreases in mosquito abundance when compared to control traps (treatment: −52.93%; control: 3.55%), although no significant differences (P = 0.286) were found in mosquito abundance between groups. Implications of reactive rather than proactive mosquito control responses are discussed
A variational formulation of anisotropic geometric evolution equations in higher dimensions
Accepted versio
Staggered dimer order in S=1/2 quantum spin ladder system with four spin exchange
We study the S=1/2 quantum spin ladder system with the four-spin exchange,
using density matrix renormalization group method and an exact diagonalization
method. Recently, the phase transition in this system and its universality
class are studied. But there remain controversies whether the phase transition
is second order type or the other type and the nature of order parameter. There
are arguments that the massless phase appears. But this does not agree with our
previous result. Analyzing DMRG data, we try a new approach in order to
determine a phase which appears after the phase transition. We find that the
edge state appears in the open boundary condition, investigating excitation
energies of states with higher magnetizations.Comment: Submitted to Phys. Rev. B, (REVTeX4
Schwinger boson theory of anisotropic ferromagnetic ultrathin films
Ferromagnetic thin films with magnetic single-ion anisotropies are studied
within the framework of Schwinger bosonization of a quantum Heisenberg model.
Two alternative bosonizations are discussed. We show that qualitatively correct
results are obtained even at the mean-field level of the theory, similar to
Schwinger boson results for other magnetic systems. In particular, the
Mermin-Wagner theorem is satisfied: a spontaneous magnetization at finite
temperatures is not found if the ground state of the anisotropic system
exhibits a continuous degeneracy. We calculate the magnetization and effective
anisotropies as functions of exchange interaction, magnetic anisotropies,
external magnetic field, and temperature for arbitrary values of the spin
quantum number. Magnetic reorientation transitions and effective anisotropies
are discussed. The results obtained by Schwinger boson mean-field theory are
compared with the many-body Green's function technique.Comment: 14 pages, including 7 EPS figures, minor changes, final version as
publishe
Monte Carlo Methods for Estimating Interfacial Free Energies and Line Tensions
Excess contributions to the free energy due to interfaces occur for many
problems encountered in the statistical physics of condensed matter when
coexistence between different phases is possible (e.g. wetting phenomena,
nucleation, crystal growth, etc.). This article reviews two methods to estimate
both interfacial free energies and line tensions by Monte Carlo simulations of
simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid
exhibiting a miscibility gap, and a simple Lennard-Jones fluid). One method is
based on thermodynamic integration. This method is useful to study flat and
inclined interfaces for Ising lattices, allowing also the estimation of line
tensions of three-phase contact lines, when the interfaces meet walls (where
"surface fields" may act). A generalization to off-lattice systems is described
as well.
The second method is based on the sampling of the order parameter
distribution of the system throughout the two-phase coexistence region of the
model. Both the interface free energies of flat interfaces and of (spherical or
cylindrical) droplets (or bubbles) can be estimated, including also systems
with walls, where sphere-cap shaped wall-attached droplets occur. The
curvature-dependence of the interfacial free energy is discussed, and estimates
for the line tensions are compared to results from the thermodynamic
integration method. Basic limitations of all these methods are critically
discussed, and an outlook on other approaches is given
Severe diarrhea outbreak in beef calves (Bos indicus) caused by G6P[11], an emergent genotype of bovine rotavirus group A
Molecular characterization of group A bovine rotavirus in southeastern and central-western Brazil, 2009-2010
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