15,471 research outputs found
Recommended from our members
Designing graduate training programs in conservation medicine-producing the right professionals with the right tools.
New challenges to human, animal, and ecosystem health demand novel solutions: New diseases are emerging from new configurations of humans, their domestic animals and wildlife; new pressures on once robust and resilient ecosystems are compromising their integrity; synthetic compounds and engineered organisms, new to the natural world, are spreading unpredictably around the globe. Globalization provides opportunities for infectious organisms to gain access to new hosts, changing in distribution and virulence. What type of training should be developed to provide professionals with the right tools to meet these challenges? In this article, we offer recommendations for developing academic programs in conservation medicine. We discuss the need for, and the advantages to, using a conservation medicine approach to address real world situations and present illustrations of how this is applied today. We suggest a core set of skills that are needed in a conservation medicine practitioner, and recommend key considerations for designing new conservation medicine training programs. We review existing programs that offer conservation medicine content, and provide examples of where opportunities exist for those interested in pursuing a conservation medicine career
Plant Disease Outlook for 1969
Knowledge of carryover inoculum is by itself insufficient to predict this year\u27s disease attacks. Two botanists and plant pathologists analyze a number of environmental factors in recommending preventive control measures for 1969
Dutch Elm Disease in Iowa
Where does DED come from? How bad is it in Iowa? Here are some answers and some ways of beating this destructive disease
Relating on-shell and off-shell formalism in perturbative quantum field theory
In the on-shell formalism (mostly used in perturbative quantum field theory)
the entries of the time ordered product T are on-shell fields (i.e. the basic
fields satisfy the free field equations). With that, (multi)linearity of T is
incompatible with the Action Ward identity. This can be circumvented by using
the off-shell formalism in which the entries of T are off-shell fields. To
relate on- and off-shell formalism correctly, a map sigma from on-shell fields
to off-shell fields was introduced axiomatically by Duetsch and Fredenhagen. In
that paper it was shown that, in the case of one real scalar field in N=4
dimensional Minkowski space, these axioms have a unique solution. However, this
solution was given there only recursively. We solve this recurrence relation
and give a fully explicit expression for sigma in the cases of the scalar,
Dirac and gauge fields for arbitrary values of the dimension N.Comment: The case of gauge fields was added. 16 page
Causal perturbation theory in terms of retarded products, and a proof of the Action Ward Identity
In the framework of perturbative algebraic quantum field theory a local
construction of interacting fields in terms of retarded products is performed,
based on earlier work of Steinmann. In our formalism the entries of the
retarded products are local functionals of the off shell classical fields, and
we prove that the interacting fields depend only on the action and not on terms
in the Lagrangian which are total derivatives, thus providing a proof of
Stora's 'Action Ward Identity'. The theory depends on free parameters which
flow under the renormalization group. This flow can be derived in our local
framework independently of the infrared behavior, as was first established by
Hollands and Wald. We explicitly compute non-trivial examples for the
renormalization of the interaction and the field.Comment: 76 pages, to appear in Rev. Math. Phy
Limit cycles in the presence of convection, a travelling wave analysis
We consider a diffusion model with limit cycle reaction functions, in the
presence of convection. We select a set of functions derived from a realistic
reaction model: the Schnakenberg equations. This resultant form is
unsymmetrical. We find a transformation which maps the irregular equations into
model form. Next we transform the dependent variables into polar form. From
here, a travelling wave analysis is performed on the radial variable. Results
are complex, but we make some simple estimates.
We carry out numerical experiments to test our analysis. An initial `knock'
starts the propagation of pattern. The speed of the travelling wave is not
quite as expected. We investigate further. The system demonstrates distinctly
different behaviour to the left and the right. We explain how this phenomenon
occurs by examining the underlying behaviour.Comment: 20 pages, 5 figure
Noble gases in diamonds: Occurrences of solarlike helium and neon
We have measured noble gases in 17 diamond samples, mostly inclusion free, from diverse, known locations. The ^3He/^4He ratios are characterized by a large spread (10^4), ranging from values below atmospheric to close to the solar ratio. Highest ratios were seen for an Australian colorless diamond composite and an Arkansas diamond. These samples also have imprecise but intriguing neon isotopic ratios, which are close to the solar value. An origin for the solarlike He and Ne in the diamond samples is unlikely to be accounted for by the presence of nucleogenic or spallogenic components. For single diamond stones a positive correlation is found between ^3He/^4He and ^(13)C/^(12)C, possibly indicating that heavy carbon is accompanied by primordial helium. However, the He result for the Australian colorless diamond composite with low δ^(13)C value requires another explanation, possibly sedimentary carbon contaminated with cosmic dust. The wide variation in ^4He/^(40)_*Ar ratios observed from diamond samples suggests a complex history for the source regions and the diamond crystallization processes. Results for two Australian diamond composites (colorless and colored), which came from the same kimberlite pipe, are especially notable: the colorless stones contain no radiogenic components but solarlike He and Ne isotopic ratios, whereas the colored stones are enriched in radiogenic and fissiogenic components. Seemingly the Australian diamonds crystallized in a heterogeneous environment in the mantle source region. A pair of Arkansas diamonds, believed to be from a single pipe, exhibits similar anomalies
Nonaxisymmetric Magnetorotational Instability in Proto-Neutron Stars
We investigate the stability of differentially rotating proto-neutron stars
(PNSs) with a toroidal magnetic field. Stability criteria for nonaxisymmetric
MHD instabilities are derived using a local linear analysis. PNSs are expected
to have much stronger radial shear in the rotation velocity compared to normal
stars. We find that nonaxisymmetric magnetorotational instability (NMRI) with a
large azimuthal wavenumber is dominant over the kink mode () in
differentially rotating PNSs. The growth rate of the NMRI is of the order of
the angular velocity which is faster than that of the kink-type
instability by several orders of magnitude. The stability criteria are
analogous to those of the axisymmetric magnetorotational instability with a
poloidal field, although the effects of leptonic gradients are considered in
our analysis. The NMRI can grow even in convectively stable layers if the
wavevectors of unstable modes are parallel to the restoring force by the
Brunt-V\"ais\"al\"a oscillation. The nonlinear evolution of NMRI could amplify
the magnetic fields and drive MHD turbulence in PNSs, which may lead to
enhancement of the neutrino luminosity.Comment: 24pages, 7figures, Accepted for publication in the Astrophysical
Journal (December 12, 2005
Expanding direction of the period doubling operator
We prove that the period doubling operator has an expanding direction at the
fixed point. We use the induced operator, a ``Perron-Frobenius type operator'',
to study the linearization of the period doubling operator at its fixed point.
We then use a sequence of linear operators with finite ranks to study this
induced operator. The proof is constructive. One can calculate the expanding
direction and the rate of expansion of the period doubling operator at the
fixed point
- …