6,911 research outputs found
Lack of correlation between constitutive and induced resistance to a herbivore in crucifer plants: real or flawed by experimental methods?
The correlation between constitutive and induced resistance to herbivores in plants has long been of interest to evolutionary biologists, and various approaches to determining levels of resistance have been used in this field of research. In this study, we examined the relationship between constitutive and induced resistance to the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), in 11 closely related species of wild crucifers. We assessed the survival, development, and reproduction of the test insects and calculated their intrinsic rate of increase as an indicator of constitutive and induced resistance for the plants. We used larvae of P. xylostella and jasmonic acid as elicitors of the induced response. We failed to find a correlation between constitutive and induced resistance in these crucifer plants when the induction of resistance was initiated by either herbivory or jasmonic acid application. Analysis of the results suggests that the failure to detect a relationship between the two types of resistance could be caused by flaws in measuring constitutive resistance, which was apparently confounded with induced resistance. We discuss the difficulties and pitfalls in measuring constitutive resistance and ways to improve the methodology in investigating the relationships between constitutive and induced resistance in plant
Calculating the I=2 Pion Scattering Length Using Tadpole Improved Clover Wilson Action on Coarse Anisotropic Lattices
In an exploratory study, using the tadpole improved clover Wilson quark
action on small, coarse and anisotropic lattices, the scattering
length in the I=2 channel is calculated within quenched approximation. A new
method is proposed which enables us to make chiral extrapolation of our lattice
results without calculating the decay constant on the lattice. Finite volume
and finite lattice spacing errors are analyzed and the results are extrapolated
towards the infinite volume and continuum limit. Comparisons of our lattice
results with the new experiment and the results from Chiral Perturbation Theory
are made. Good agreements are found.Comment: 21 pages, 8 figures, latex file typeset with elsart.cls, minor
change
Politics, geological past, and the future of earth
From the 1940s, new technologies, like carbon dating, ice- and sea-core drilling, and pollen analysis not only vastly expanded time horizons in geophysical and climatological research, but also pinpointed past events on a newly historical timescale. Using natural proxy indicators, these studies brought to light a series of globally disruptive events in geological time, for example, volcanic eruptions of previously unknown scale and types that had also an impact on the Earth’s climate. The past became discrete. Knowing more about the past also meant knowing more about possible futures, given that some catastrophic events have occurred repeatedly or have become increasingly predictable with the help of computer modeling. This meant that scientists' claims about the future of the earth increasingly came to interfere with politics and with traditional economic planning. The paper argues that the “new” past has come to weigh in two ways on the present and the future. First, it dwarfed the human time scale, thus in-creasing the challenge of dealing with heterogeneous time scales. Second, prehis-toric past events came to take on political significance. The deep past became part of political history, and thus of politics
CP Test in the W Pair Production via Photon Fusion at NLC
We study the possibility to test CP invariance in the production via
photon fusion at NLC. The predictions of the CP violation effects are made
within two Higgs doublet extensions of the minimal standard model, where CP
violation is introduced by a neutral Higgs exchange in s channel in our case.
The width effect in the Higgs propagator on the CP violation effects is studied
in detail. The CP violation effects can be measured in some parameter region of
the extensions.Comment: 11 pages, Tex, UM-P-93/16, OZ-93/6 One figure not include
Towards Supergravity Duals of Chiral Symmetry Breaking in Sasaki-Einstein Cascading Quiver Theories
We construct a first order deformation of the complex structure of the cone
over Sasaki-Einstein spaces Y^{p,q} and check supersymmetry explicitly. This
space is a central element in the holographic dual of chiral symmetry breaking
for a large class of cascading quiver theories. We discuss a solution
describing a stack of N D3 branes and M fractional D3 branes at the tip of the
deformed spaces.Comment: 28 pages, no figures. v2: typos, references and a note adde
Exact soliton solution and inelastic two-soliton collision in spin chain driven by a time-dependent magnetic field
We investigate dynamics of exact N-soliton trains in spin chain driven by a
time-dependent magnetic field by means of an inverse scattering transformation.
The one-soliton solution indicates obviously the spin precession around the
magnetic field and periodic shape-variation induced by the time varying field
as well. In terms of the general soliton solutions N-soliton interaction and
particularly various two-soliton collisions are analyzed. The inelastic
collision by which we mean the soliton shape change before and after collision
appears generally due to the time varying field. We, moreover, show that
complete inelastic collisions can be achieved by adjusting spectrum and field
parameters. This may lead a potential technique of shape control of soliton.Comment: 5 pages, 5 figure
Reliability-based code revision for design of pile foundations: Practice in Shanghai, China
AbstractThis paper describes how the code for the design of pile foundations in Shanghai, China is revised based on the reliability theory. With quality static load test data, both within-site and cross-site variabilities for design methods of piles in Shanghai are characterized. It is found that the amount of uncertainties associated with the design of piles in Shanghai is less than the typical values reported in the literature. With the partial factors specified in the previous design code, the reliability indexes of piles designed with empirical methods are in the range of 3.08–4.64, while those of piles designed with the load test-based method are in the range of 5.67–5.89. The load factors in the revised local design code have been reduced according to the national design code. As a result, the resistance factors have been increased in the revised code based on a combination of a reliability analysis and engineering judgment. In the revised design code, the reliability level of piles designed with the empirical methods is similar to that in the previous design code; the reliability level of piles designed with the load test-based method is lowered to achieve cost-effectiveness. Partial factors have been suggested for side and toe resistances based on the reliability theory considering their relative importance as well as the uncertainties involved
New supersymmetric solutions of N=2, D=5 gauged supergravity with hyperscalars
We construct new supersymmetric solutions, including AdS bubbles, in an N=2
truncation of five-dimensional N=8 gauged supergravity. This particular
truncation is given by N=2 gauged supergravity coupled to two vector multiples
and three incomplete hypermultiplets, and was originally investigated in the
context of obtaining regular AdS bubble geometries with multiple active
R-charges. We focus on cohomogeneity-one solutions corresponding to objects
with two equal angular momenta and up to three independent R-charges.
Curiously, we find a new set of zero and negative mass solitons asymptotic to
AdS_5/Z_k, for k \ge 3, which are everywhere regular without closed timelike
curves.Comment: Latex 3 times, 42 page
Low Temperature Measurements by Infrared Spectroscopy in CoFeO Ceramic
In this paper results of new far-infrared and middle-infrared measurements
(wavenumber range of 4000cm-1 - 100cm-1) in the range of the temperature from
300K to 8K of the CoFe2O4 ceramic are presented. The bands positions and their
shapes are the same in the wide temperature range. The quality of the sample
was investigated by X-ray, EDS and EPMA studies. The CoFe2O4 reveals the cubic
structure (Fd-3m) in the temperature range from 85K to 360 K without any traces
of distortion. On the current level of knowledge the polycrystalline CoFe2O4
does not exhibit phase transition in the temperature range from 8 K to 300 K.Comment: 10 pages, 6 figure
Supersymmetric Boost on Intersecting D-branes
We study the effect of the Born-Infeld electric field on the supersymmetric
configuration of various composite D-branes. We show that the generic values of
the electric field do not affect the supersymmetry but, as it approaches
keeping the magnetic field finite, various combinations of the
magnetic fields allow up to 8 supersymmetries. We also explore the unbroken
supersymmetries for two intersecting D-strings which are in uniform or relative
motion. For a finite uniform Lorentz boost, 16 supersymmetries are guaranteed
only when they are parallel. For an infinite one, 8 supersymmetries are
preserved only when both the D-strings are oriented to the forward or backward
direction of the boost. Under a finite relative boost, 8 supersymmetries are
preserved only when the intersecting angle is less than and the
intersecting point moves at the speed of light. As for an infinite relative
boost, 8 supersymmetries are preserved regardless of the values of the
intersecting angle.Comment: 27 pages using REVTeX4, 7 figure
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