22,951 research outputs found
Parasitism of Early Instar Jack Pine Budworm (Lepidoptera: Tortricidae) by Apanteles Spp. (Hymenoptera: Braconidae) and Glypta Fumiferanae (Hymenoptera: Ichneumonidae)
Glypta fumiferanae and two species of Apanteles parasitized 1st-4th instar jack pine bud worm (Choristoneura pinus). Apparent parasitism of budworm in four Michigan populations ranged from 10.6 to 30.9% for A. fumiferanae, 4.3-16.4% for A. morrisi, and 2.1-9.1 % for G.fumiferanae. A. morrisi probably parasitized 3rd-4th instar jack pine bud worm. Based on the results obtained, it is suggested that sampling overwintering budworm larvae is appropriate for estimating apparent parasitism by A. fumiferanae and G. fumiferanae. Sampling budworm larvae at ca. 500 degree-days (base 8.9°C) is appropriate for estimating apparent parasitism by A. morrisi
The ordered K-theory of a full extension
Let A be a C*-algebra with real rank zero which has the stable weak
cancellation property. Let I be an ideal of A such that I is stable and
satisfies the corona factorization property. We prove that 0->I->A->A/I->0 is a
full extension if and only if the extension is stenotic and K-lexicographic. As
an immediate application, we extend the classification result for graph
C*-algebras obtained by Tomforde and the first named author to the general
non-unital case. In combination with recent results by Katsura, Tomforde, West
and the first author, our result may also be used to give a purely
K-theoretical description of when an essential extension of two simple and
stable graph C*-algebras is again a graph C*-algebra.Comment: Version IV: No changes to the text. We only report that Theorem 4.9
is not correct as stated. See arXiv:1505.05951 for more details. Since
Theorem 4.9 is an application to the main results of the paper, the main
results of this paper are not affected by the error. Version III comments:
Some typos and errors corrected. Some references adde
Modelling cell motility and chemotaxis with evolving surface finite elements
We present a mathematical and a computational framework for the modelling of cell motility. The cell membrane is represented by an evolving surface, with the movement of the cell determined by the interaction of various forces that act normal to the surface. We consider external forces such as those that may arise owing to inhomogeneities in the medium and a pressure that constrains the enclosed volume, as well as internal forces that arise from the reaction of the cells' surface to stretching and bending. We also consider a protrusive force associated with a reaction-diffusion system (RDS) posed on the cell membrane, with cell polarization modelled by this surface RDS. The computational method is based on an evolving surface finite-element method. The general method can account for the large deformations that arise in cell motility and allows the simulation of cell migration in three dimensions. We illustrate applications of the proposed modelling framework and numerical method by reporting on numerical simulations of a model for eukaryotic chemotaxis and a model for the persistent movement of keratocytes in two and three space dimensions. Movies of the simulated cells can be obtained from http://homepages.warwick.ac.uk/maskae/CV_Warwick/Chemotaxis.html
A Descriptive Study of the Population Dynamics of Adult \u3ci\u3eDiabrotica Virgifera Virgifera\u3c/i\u3e (Coleoptera: Chrysomelidae) in Artificially Infested Corn Fields
The influence of corn plant phenology on the dynamics of adult western corn rootworm, Diabrotica virgifera virgifera, populations was studied during 1988 and 1989 in com fields artificially infested with eggs. Fifty percent of adult emergence from the soil occurred by day 194 in 1988 and day 203 in 1989. In both years, adult emergence was synchronized with corn flowering, eggs were recovered in soil samples approximately four days after reproductive females were first observed in the population, and oviposition was essentially complete about 25 days after it began. The number of reproductive female beetle-days accumulating per m2 was similar in both years. Approximately two times as many eggs were laid in 1988 (1239 eggs 1m2) as in 1989 (590 eggs 1m2). The difference in egg density may have been caused by differences among years in the temporal synchrony of reproductive beetles with flowering corn. Daily survival rates of adults were high while corn was flowering; exhibited a gradual decline during grain filling; and decreased rapidly during the grain drying stage
Genetic Differentiation Among Three Species of \u3ci\u3eParadosa\u3c/i\u3e (Arachnida: Lycosidae)
Allozymic variation in nine protein producing loci was examined in three species of Pardosa using starch gel electrophoresis. Allozyme frequencies showed a high degree of geographic uniformity among conspecific populations. Estimated heterozygosities for the three species ranged from 0.05 to 0.15. Rogers\u27 coefficients of genetic similarity based on allozyme frequencies averaged over conspecific populations ranged from 0.16 to 0.37 fo rthe three species
Immersion microscopy based on photonic crystal materials
Theoretical model of the enhanced optical resolution of the surface plasmon
immersion microscope is developed, which is based on the optics of surface
plasmon Bloch waves in the tightly bound approximation. It is shown that a
similar resolution enhancement may occur in a more general case of an immersion
microscope based on photonic crystal materials with either positive or negative
effective refractive index. Both signs of the effective refractive index have
been observed in our experiments with surface plasmon immersion microscope,
which is also shown to be capable of individual virus imaging.Comment: 23 pages, 10 figure
Search for associations containing young stars (SACY). V. Is multiplicity universal? Tight multiple systems
Context: Dynamically undisrupted, young populations of stars are crucial to
study the role of multiplicity in relation to star formation. Loose nearby
associations provide us with a great sample of close (150 pc) Pre-Main
Sequence (PMS) stars across the very important age range (5-70 Myr) to
conduct such research.
Aims: We characterize the short period multiplicity fraction of the SACY
(Search for Associations Containing Young stars) accounting for any
identifiable bias in our techniques and present the role of multiplicity
fractions of the SACY sample in the context of star formation.
Methods: Using the cross-correlation technique we identified double-lined
spectroscopic systems (SB2), in addition to this we computed Radial Velocity
(RV) values for our subsample of SACY targets using several epochs of FEROS and
UVES data. These values were used to revise the membership of each association
then combined with archival data to determine significant RV variations across
different data epochs characteristic of multiplicity; single-lined multiple
systems (SB1).
Results: We identified 7 new multiple systems (SB1s: 5, SB2s: 2). We find no
significant difference between the short period multiplicity fraction
() of the SACY sample and that of nearby star forming regions
(1-2 Myr) and the field (10%) both as a function of
age and as a function of primary mass, , in the ranges [1:200 day] and
[0.08 -].
Conclusions: Our results are consistent with the picture of universal star
formation, when compared to the field and nearby star forming regions (SFRs).
We comment on the implications of the relationship between increasing
multiplicity fraction with primary mass, within the close companion range, in
relation to star formation.Comment: 14 pages, 18 figures, published, A&A
http://dx.doi.org/10.1051/0004-6361/20142385
Bubbles and Filaments: Stirring a Cahn-Hilliard Fluid
The advective Cahn-Hilliard equation describes the competing processes of
stirring and separation in a two-phase fluid. Intuition suggests that bubbles
will form on a certain scale, and previous studies of Cahn-Hilliard dynamics
seem to suggest the presence of one dominant length scale. However, the
Cahn-Hilliard phase-separation mechanism contains a hyperdiffusion term and we
show that, by stirring the mixture at a sufficiently large amplitude, we excite
the diffusion and overwhelm the segregation to create a homogeneous liquid. At
intermediate amplitudes we see regions of bubbles coexisting with regions of
hyperdiffusive filaments. Thus, the problem possesses two dominant length
scales, associated with the bubbles and filaments. For simplicity, we use use a
chaotic flow that mimics turbulent stirring at large Prandtl number. We compare
our results with the case of variable mobility, in which growth of bubble size
is dominated by interfacial rather than bulk effects, and find qualitatively
similar results.Comment: 20 pages, 27 figures. RevTeX
Paspalum grass
Originally native to Uruguay and Argentina, Paspalum dilatatum was introduced into the U.S.A. about the middle of the 19th century and is now firmly established and cultivated in the Gulf States where it is known as Dallis erass after A. T. Dallis of La Grange, Georgia. It was introduced into Australia by Baron von Mueller about 1880 and since 1898 its cultivation has steadily increased
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