2,143 research outputs found
Teaching a Large Field Course in the 21st Century
Recent enrollment increases have presented some interesting challenges in maintaining the quality of our summer field course for natural resource students. We will discuss the logistical challenges, content and structure of the course and recent improvements made to the curriculum
Integrated control of vector-borne diseases of livestock--pyrethroids: panacea or poison?
Tick- and tsetse-borne diseases cost Africa approximately US$4-5 billion per year in livestock production-associated losses. The use of pyrethroid-treated cattle to control ticks and tsetse promises to be an increasingly important tool to counter this loss. However, uncontrolled use of this technology might lead to environmental damage, acaricide resistance in tick populations and a possible exacerbation of tick-borne diseases. Recent research to identify, quantify and to develop strategies to avoid these effects are highlighted
The physiology and ecology of diapause under present and future climate conditions in the blow fly, Calliphora vicina
Virtually all temperate insects overwinter in diapause, a pre-emptive response to adverse environmental conditions and for many species a pre-requisite of winter survival. Increased global temperatures have the potential to disrupt the induction and maintenance of diapause.
In the first part of this thesis, a four year phenological study of the blow fly, , identifies that diapause is already being delayed due to high temperatures experienced by larvae within the soil layer. Laboratory studies identified that non-diapause life stages are capable of heightening cold tolerance through a rapid cold hardening ability, and winter acclimated adults maintain locomotion at lower temperatures than summer acclimated adults. A previously unrecognised threat, however, is that higher adult temperatures have the transgenerational effect of reducing the cold tolerance of diapausing progeny.
In the second part of this thesis, the relationship between diapause and cold hardiness was investigated. The amino acid, alanine, was up-regulated as part of the diapause programme. Non-diapause larvae developed on an alanine augmented-diet expressed cold tolerance phenotypes similar to those of their diapausing counterparts. This adds to a growing body of evidence to suggest that amino acids have a direct role in insect cold tolerance
Chapitre 18 - Trypanosomiase humaine et animale africaine
Introduction La gestion du risque de zoonoses résultant des interactions entre les animaux, les humains et l’environnement exige une action intégrée des secteurs de la santé humaine et animale, le soutien d’autres secteurs ou industries concernés par la gouvernance sanitaire et des apports clefs de la filière environnementale (Cook et al., 2004 ; Okello et al., 2011 ; Welburn, 2011 ; Zinsstag et al., 2012). Dans ..
Self-dual Maxwell Chern-Simons Solitons In 1+1 Dimensions
We study the domain wall soliton solutions in the relativistic self-dual
Maxwell Chern-Simons model in 1+1 dimensions obtained by the dimensional
reduction of the 2+1 model. Both topological and nontopological self-dual
solutions are found in this case. A la BPS dyons here the Bogomol'ny bound on
the energy is expressed in terms of two conserved quantities. We discuss the
underlying supersymmetry. Nonrelativistic limit of this model is also
considered and static, nonrelativistic self-dual soliton solutions are
obtained.Comment: 18 pages RevTex, 2 figures included, to appear in Phys. Rev.
Visions of a more precise soil biology
Includes bibliographical references (pages 389-390).Soils have often been viewed as a black box. Soil biology is difficult to study with the precision we would wish, due to the presence of considerable soil heterogeneity, a huge diversity of organisms, and a plethora of interacting processes taking place in a complex physical-chemical environment. We have isolated a tiny fraction of the known organisms, and the possible interactions of soil parent materials, landscape, land use, depth and time with the biota mean that we are to some extent still fumbling in the dark. There have been great advances, but we argue that the pace of advance could be faster. To progress, science needs new theory and concepts but also acceptable methodologies. Coherent and generally accepted theoretical knowledge exists in many areas, but there is a shortage of valid and exact methods to test new and sometimes even old hypotheses. New methods add knowledge, but they also can add to the confusion if they are not tied to the existing knowledge base. We speculate on how to improve soil biology through improving the way we perform and interpret research. Can we deal with soil variability? Can we measure the critical variables with adequate precision to test our hypotheses? Can we avoid reinventing the wheel? Can we find a balance between the freedom to test new and maybe even controversial ideas and the control and direction of research required by society?
The break up of heavy electrons at a quantum critical point
The point at absolute zero where matter becomes unstable to new forms of
order is called a quantum critical point (QCP). The quantum fluctuations
between order and disorder that develop at this point induce profound
transformations in the finite temperature electronic properties of the
material. Magnetic fields are ideal for tuning a material as close as possible
to a QCP, where the most intense effects of criticality can be studied. A
previous study on theheavy-electron material found that near a
field-induced quantum critical point electrons move ever more slowly and
scatter off one-another with ever increasing probability, as indicated by a
divergence to infinity of the electron effective mass and cross-section. These
studies could not shed light on whether these properties were an artifact of
the applied field, or a more general feature of field-free QCPs. Here we report
that when Germanium-doped is tuned away from a chemically induced
quantum critical point by magnetic fields there is a universal behavior in the
temperature dependence of the specific heat and resistivity: the characteristic
kinetic energy of electrons is directly proportional to the strength of the
applied field. We infer that all ballistic motion of electrons vanishes at a
QCP, forming a new class of conductor in which individual electrons decay into
collective current carrying motions of the electron fluid.Comment: Pdf files of article available at
http://www.physics.rutgers.edu/~coleman/online/breakup.pdf, pdf file of news
and views article available at
http://www.physics.rutgers.edu/~coleman/online/nvbreakup.pd
Conformal topological Yang-Mills theory and de Sitter holography
A new topological conformal field theory in four Euclidean dimensions is
constructed from N=4 super Yang-Mills theory by twisting the whole of the
conformal group with the whole of the R-symmetry group, resulting in a theory
that is conformally invariant and has two conformally invariant BRST operators.
A curved space generalisation is found on any Riemannian 4-fold. This
formulation has local Weyl invariance and two Weyl-invariant BRST symmetries,
with an action and energy-momentum tensor that are BRST-exact. This theory is
expected to have a holographic dual in 5-dimensional de Sitter space.Comment: 34 pages, AMSTex, Reference adde
Self-dual Vortices in the Generalized Abelian Higgs Model with Independent Chern-Simons Interaction
Self-dual vortex solutions are studied in detail in the generalized abelian
Higgs model with independent Chern-Simons interaction. For special choices of
couplings, it reduces to a Maxwell-Higgs model with two scalar fields, a
Chern-Simons-Higgs model with two scalar fields, or other new models. We
investigate the properties of the static solutions and perform detailed
numerical analyses. For the Chern-Simons-Higgs model with two scalar fields in
an asymmetric phase, we prove the existence of multisoliton solutions which can
be viewed as hybrids of Chern-Simons vortices and lumps. We also discuss
solutions in a symmetric phase with the help of the corresponding exact
solutions in its nonrelativistic limit. The model interpolating all three
models---Maxwell-Higgs, Chern-Simons-Higgs, and models--- is discussed
briefly. Finally we study the possibility of vortex solutions with half-integer
vorticity in the special case of the model. Numerical results are negative.Comment: 32 pages, LATEX, SNUTP 92-7
Dicyclic Horizontal Symmetry and Supersymmetric Grand Unification
It is shown how to use as horizontal symmetry the dicyclic group in a supersymmetric unification where
one acts on the first and second families, in a horizontal doublet, and
the other acts on the third. This can lead to acceptable quark masses and
mixings, with an economic choice of matter supermultiplets, and charged lepton
masses can be accommodated.Comment: 10 pages, LaTe
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