30,451 research outputs found
Computation of epidemic final size distributions
We develop a new methodology for the efficient computation of epidemic final
size distributions for a broad class of Markovian models. We exploit a
particular representation of the stochastic epidemic process to derive a method
which is both computationally efficient and numerically stable. The algorithms
we present are also physically transparent and so allow us to extend this
method from the basic SIR model to a model with a phase-type infectious period
and another with waning immunity. The underlying theory is applicable to many
Markovian models where we wish to efficiently calculate hitting probabilities.Comment: final published versio
Introduction to Library Trends 56 (1) Summer 2007: Preserving Cultural Heritage
published or submitted for publicatio
Evaluating cultural competency and patient satisfaction in an urban dermatology clinic.
Cultural competency continues to gain increased attention in medicine. Not only does it play a significant role in the delivery of health care and patient outcomes, but it also remains a major determinant of patient satisfaction. This study investigated how patients in an urban dermatology clinic rated their satisfaction with cultural competency. Compared to White patients, satisfaction scores were greater for Hispanic or Latino patients and less for Asian patients, while there was no significant difference for Black or African American patients. There were clear differences in patient satisfaction rates of various dimensions of cultural competency. A follow-up study with a larger sample size is needed for closer examination into the conclusions
Probabilistic risk assessment of the environmental impacts of pesticides in the Crocodile (west) Marico catchment, North-West Province
External agricultural inputs, such as pesticides, may pose risks to aquatic ecosystems and affect aquatic populations, communities and ecosystems. To predict these risks, a tiered approach was followed, incorporating both the PRIMET and PERPEST models. The first-tier PRIMET model is designed to yield a relatively worst-case risk assessment requiring a minimum of input data, after which the effects of the risks can be refined using a higher tier PERPEST model. The risk assessment initially depends on data supplied from local landowners, pesticide characteristic, application scheme and physical scenario of the environment under question. Preliminary results are presented, together with ecotoxicological data on several frequently-used pesticides in a section of the Crocodile (west) Marico Water Management Area (WMA) in South Africa. This area is historically known to have a high pesticide usage, with deltamethrin, aldicarb, parathion, cypermethrin and dichlorvos being the main pesticides used. Deltamethrin was indicated as having the highest probability of risks to aquatic organisms occurring in the study area. Cypermethrin, parathion, dichlorvos, carbaryl, romoxynil, linuron, methomyl and aldicarb were all indicated as having possible risks (ETR 1-100) to the aquatic environment. Pesticides posing no risk included fenamiphos, abamectin, pendimethalin, captan, endosulfan, alachlor, bentazone and cyromazine (ET
Larval Ecology of Some Lower Michigan Black Flies (Diptera: Simuliidae) With Keys to the Immature Stages
The species composition, succession, and seasonal abundance of -immature simuliids ocmrrhg in the Rose Lake Wildlife Research Area in lower Michigan are presented. Selected physical and chemical characteristics of streams in the above area were examined and compared in relation to faunal distributions. Comparisons of species differences between permanent and temporary streams were made utilizing the functional group concept based on feeding mechanisms.
Keys and illustrations are presented for the identiiication of larvae and pupae of four genera (Prosimulium, Simulium, Stegopterna, Cnephia) and 19 species of Simuliidae known to occur in lower Michigan. Two species, Cnephia ornithophilia and Simulium vemum, were recorded for the first time in Michigan
Physics of relativistic shocks
Relativistic shocks are usually thought to occur in violent astrophysical
explosions. These collisionless shocks are mediated by a plasma kinetic
streaming instability, often loosely referred to as the Weibel instability,
which generates strong magnetic fields "from scratch" very efficiently. In this
review paper we discuss the shock micro-physics and present a recent model of
"pre-conditioning" of an initially unmagnetized upstream region via the
cosmic-ray-driven Weibel-type instability.Comment: Subm. to proceedings of the Annual International Astrophysics
Conference (AIAC-8), Hawaii, 200
One-dimensional in-plane edge domain walls in ultrathin ferromagnetic films
We study existence and properties of one-dimensional edge domain walls in
ultrathin ferromagnetic films with uniaxial in-plane magnetic anisotropy. In
these materials, the magnetization vector is constrained to lie entirely in the
film plane, with the preferred directions dictated by the magnetocrystalline
easy axis. We consider magnetization profiles in the vicinity of a straight
film edge oriented at an arbitrary angle with respect to the easy axis. To
minimize the micromagnetic energy, these profiles form transition layers in
which the magnetization vector rotates away from the direction of the easy axis
to align with the film edge. We prove existence of edge domain walls as
minimizers of the appropriate one-dimensional micromagnetic energy functional
and show that they are classical solutions of the associated Euler-Lagrange
equation with Dirichlet boundary condition at the edge. We also perform a
numerical study of these one-dimensional domain walls and uncover further
properties of these domain wall profiles
- …