965 research outputs found
Intrinsic competition and its effects on the survival and development of three species of endoparasitoid wasps
In natural systems, pre-adult stages of some insect herbivores are known to be attacked by several species of parasitoids. Under certain conditions, hosts may be simultaneously parasitized by more than one parasitoid species (= multiparasitism), even though only one parasitoid species can successfully develop in an individual host. Here, we compared development, survival, and intrinsic competitive interactions among three species of solitary larval endoparasitoids, Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae), Microplitis demolitor Wilkinson, and Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), in singly parasitized and multiparasitized hosts. The three species differed in certain traits, such as in host usage strategies and adult body size. Campoletis sonorensis and M. demolitor survived equally well to eclosion in two host species that differed profoundly in size, Pseudoplusia includens (Walker) and the larger Heliothis virescens (Fabricius) (both Lepidoptera: Noctuidae). Egg-to-adult development time in C. sonorensis and M. demolitor also differed in the two hosts. Moreover, adult body mass in C. sonorensis (and not M. demolitor) was greater when developing in H. virescens larvae. We then monitored the outcome of competitive interactions in host larvae that were parasitized by one parasitoid species and subsequently multiparasitized by another species at various time intervals (0, 6, 24, and 48 h) after the initial parasitism. These experiments revealed that M. croceipes was generally a superior competitor to the other two species, whereas M. demolitor was the poorest competitor, with C. sonorensis being intermediate in this capacity. However, competition sometimes incurred fitness costs in M. croceipes and C. sonorensis, with longer development time and/or smaller adult mass observed in surviving wasps emerging from multiparasitized hosts. Our results suggest that rapid growth and large size relative to competitors of a similar age may be beneficial in aggressive intrinsic competitio
Quasi-localized states on noncommutative solitons
We consider noncommutative gauge theories which have zero mass states
propagating along both commutative and noncommutative dimensions. Solitons in
these theories generically carry U(m) gauge group on their world-volume. From
the point of view of string theory, these solitons correspond to
``branes within branes''. We show that once the world-volume U(m) gauge
theory is in the Higgs phase, light states become quasi-localized, rather than
strictly localized on the soliton, i.e. they mix with light bulk modes and have
finite widths to escape into the noncommutative dimensions. At small values of
U(m) symmetry breaking parameters, these widths are small compared to the
corresponding masses. Explicit examples considered are adjoint scalar field in
the background of a noncommutative vortex in U(1)-Higgs theory, and gauge
fields in instanton backgrounds in pure gauge noncommutative theories.Comment: 27 pages, references and comments added, final version to appear in
JHE
A Note on c=1 Virasoro Boundary States and Asymmetric Shift Orbifolds
We comment on the conformal boundary states of the c=1 free boson theory on a
circle which do not preserve the U(1) symmetry. We construct these Virasoro
boundary states at a generic radius by a simple asymmetric shift orbifold
acting on the fundamental boundary states at the self-dual radius. We further
calculate the boundary entropy and find that the Virasoro boundary states at
irrational radius have infinite boundary entropy. The corresponding open string
description of the asymmetric orbifold is given using the quotient algebra
construction. Moreover, we find that the quotient algebra associated with a
non-fundamental boundary state contains the noncommutative Weyl algebra.Comment: 21 pages, harvmac; v2: minor clarification in section 3.4; v3: a
discussion on cocycles added in section 2, and low energy limit mistake
removed and clarifications added in section 4.
Some Low Dimensional Evidence for the Weak Gravity Conjecture
We discuss a few examples in 2+1 dimensions and 1+1 dimensions supporting a
recent conjecture concerning the relation between the Planck scale and the
coupling strength of a non-gravitional interaction, unlike those examples in
3+1 dimensions, we do not have to resort to exotic physics such as small black
holes. However, the result concerning these low dimensional examples is a
direct consequence of the 3+1 dimensional conjecture.Comment: 7 pages, harvma
Generalised permutation branes
We propose a new class of non-factorising D-branes in the product group GxG
where the fluxes and metrics on the two factors do not necessarily coincide.
They generalise the maximally symmetric permutation branes which are known to
exist when the fluxes agree, but break the symmetry down to the diagonal
current algebra in the generic case. Evidence for the existence of these branes
comes from a Lagrangian description for the open string world-sheet and from
effective Dirac-Born-Infeld theory. We state the geometry, gauge fields and, in
the case of SU(2)xSU(2), tensions and partial results on the open string
spectrum. In the latter case the generalised permutation branes provide a
natural and complete explanation for the charges predicted by K-theory
including their torsion.Comment: 33 pages, 6 figures, v2: Extended discussion of K-theory
interpretation of our branes for products of higher rank groups in the
conclusions; v3: Correction of formula (35) and adjustment of the discussion
below equation (45) (no change of result). Footnote 9 points out a previously
unnoticed subtlety and provides a reference to a more detailed discussio
Non-BPS Solutions of the Noncommutative CP^1 Model in 2+1 Dimensions
We find non-BPS solutions of the noncommutative CP^1 model in 2+1 dimensions.
These solutions correspond to soliton anti-soliton configurations. We show that
the one-soliton one-anti-soliton solution is unstable when the distance between
the soliton and the anti-soliton is small. We also construct time-dependent
solutions and other types of solutions.Comment: 11 pages, minor correction
D1-D5 on ALE Space
We construct a two-dimensional N=(0,4) quiver gauge theory on D1-brane
probing D5-branes on ALE space, and study its IR behavior. This can be thought
of as a gauged linear sigma model for the NS5-branes on ALE space.Comment: 17 pages, 1 figure, lanlmac; v2: reference adde
Characterizing the metabolic effects of the selective inhibition of gut microbial β-glucuronidases in mice
The hydrolysis of xenobiotic glucuronides by gut bacterial glucuronidases reactivates previously detoxified compounds resulting in severe gut toxicity for the host. Selective bacterial β-glucuronidase inhibitors can mitigate this toxicity but their impact on wider host metabolic processes has not been studied. To investigate this the inhibitor 4-(8-(piperazin-1-yl)-1,2,3,4-tetrahydro-[1,2,3]triazino[4′,5′:4,5]thieno[2,3-c]isoquinolin-5-yl)morpholine (UNC10201652, Inh 9) was administered to mice to selectively inhibit a narrow range of bacterial β-glucuronidases in the gut. The metabolomic profiles of the intestinal contents, biofluids, and several tissues involved in the enterohepatic circulation were measured and compared to control animals. No biochemical perturbations were observed in the plasma, liver or gall bladder. In contrast, the metabolite profiles of urine, colon contents, feces and gut wall were altered compared to the controls. Changes were largely restricted to compounds derived from gut microbial metabolism. This work establishes that inhibitors targeted towards bacterial β-glucuronidases modulate the functionality of the intestinal microbiota without adversely impacting the host metabolic system
Ricci-flat deformation of orbifolds and localized tachyonic modes
We study Ricci-flat deformations of orbifolds in type II theory. We obtain a
simple formula for mass corrections to the twisted modes due to the
deformations, and apply it to originally tachyonic and massless states in
several examples. In the case of supersymmetric orbifolds, we find that
tachyonic states appear when the deformation breaks all the supersymmetries. We
also study nonsupersymmetric orbifolds C^2/Z_{2N(2N+1)}, which is T-dual to N
type 0 NS5-branes. For N>=2, we compute mass corrections for states, which have
string scale tachyonic masses. We find that the corrected masses coincide to
ones obtained by solving the wave equation for the tachyon field in the smeared
type 0 NS5-brane background geometry. For N=1, we show that the unstable mode
representing the bubble creation is the unique tachyonic mode.Comment: 20 pages, minor collection
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