8,269 research outputs found
Permanental Ideals
The principal result is a primary decomposition of ideals generated by the
(2x2)-subpermanents of a generic matrix. These permanental ideals almost always
have embedded components and their minimal primes are of three distinct
heights. Thus the permanental ideals are almost never Cohen-Macaulay, in
contrast with determinantal ideals.Comment: 13 page
\u3ci\u3eLycaeides Melissa Samuelis\u3c/i\u3e (Lepidoptera: Lycaenidae) Response to an Aggregation of \u3ci\u3eLytta Sayi\u3c/i\u3e (Coleoptera: Meloidae) on \u3ci\u3eLupinus Perennis\u3c/i\u3e (Fabaceae
Lycaeides melissa samuelis Nabokov, frequently called the Karner blue butterfly, is a Federally endangered species found in savanna/barren type ecosystems of New England and the Great Lakes region of North America. We observed sporadic and localized feeding aggregations of Lytta sayi LeConte (Coleoptera: Meloidae) on Lupinus perennis L. (Fabaceae) occupied by L. m. samuelis during the summers of 2000-2004, in Eau Claire County, Wisconsin. In 2004, we quantified the phenology and behavior of an aggregation (\u3e 900 beetles) within a 1,020 m2 stand of lupine and measured its effect upon adult L. m. samuelis behavior. The L. sayi aggregation formed and dispersed within 11 days with three beetles observed on day one and a maximum of 951 beetles on day seven. By the eighth day of the aggregation, the beetles had consumed 100% of the lupine flowers, 2% of lupine seeds and no lupine leaves. In comparisons of L. m. samuelis activity before and during the beetle aggregation, L. m. samuelis males spent significantly less time perching on Potentilla simplex Michaux (Rosaceae) and more time flying during the beetle aggregation. L. m. samuelis females spent significantly less time under lupine leaves during the beetle aggregation. Distribution of L. m. samuelis larval feeding damage suggests adult females avoided ovipositing in areas containing large numbers of beetles
Radiation counting technique allows density measurement of metals in high-pressure/ high-temperature environment
Radioactive tracers induced by neutron irradiation provide a gamma ray flux proportional to the density of a metal, allowing density measurement of these metals in extreme high-temperature and high-pressure environments. This concept is applicable to most metals, as well as other substances
Inflation Assisted by Heterotic Axions
We explore the possibility of obtaining inflation in weakly coupled heterotic
string theory, where the model dependent axions are responsible for driving
inflation. This model can be considered as a certain extrapolation of
-inflation, and is an attempt to explicitly realize the so
called N-flation proposal in string theory. The instanton generated potential
for the axions essentially has two parameters; a natural mass scale and the
string coupling . For isotropic compactifications leading to of order
axions in the four dimensional spectrum we find that with
the observed temperature fluctuations in the
CMB are correctly reproduced. We assume an initially random distribution for
the vevs of the axions. The spectral index, , is generically more red
than for -inflation. The greater the vevs, the more red the
spectral index becomes. Allowing for a wide range of vevs 55 -foldings from
the end of inflation, we find . The
tensor-to-scalar ratio, , is more sensitive to the vevs, but typically
smaller than in -inflation. Furthermore, in the regime where the
leading order theory is valid, is bounded by . The spectral index
and the tensor-to-scalar ratio are correlated. For example,
corresponds to .Comment: 1+21 pages, 2 figures, v2: Typos corrected, v3: Typos, very minor
corrections, reference added, to appear in JCA
Weak Convergence of the Scaled Median of Independent Brownian Motions
We consider the median of n independent Brownian motions, and show that this
process, when properly scaled, converges weakly to a centered Gaussian process.
The chief difficulty is establishing tightness, which is proved through direct
estimates on the increments of the median process. An explicit formula is given
for the covariance function of the limit process. The limit process is also
shown to be Holder continuous with exponent gamma for all gamma < 1/4.Comment: to appear in Probability Theory and Related Field
A Pilot Study on the Use of Lecture Tools to Enhance the Teaching of Pharmacokinetics and Pharmacodynamics
Pharmacokinetics and pharmacodynamics are essential topics contained within the medical curriculum and are highly amenable to active-learning approaches. In this pilot study, we incorporated Lecture Tools, a cloud-based audience response system, into a lecture-based graduate course. Lecture Tools was used by both the instructors and the students during peer presentations. Advantages noted by the instructors include the versatility of the questions that can be presented and the ease with which student assessment can be conducted. Student surveys revealed that, overall, the use of Lecture Tools enhanced student attentiveness and engagement and facilitated student participation in questions and answers. Some disadvantages were observed and include the increased time required for lecture presentations. In summary, our results indicate that Lecture Tools can be effectively used in a medical education setting
Physics Opportunities with Meson Beams
Over the past two decades, meson photo- and electro-production data of
unprecedented quality and quantity have been measured at electromagnetic
facilities worldwide. By contrast, the meson-beam data for the same hadronic
final states are mostly outdated and largely of poor quality, or even
nonexistent, and thus provide inadequate input to help interpret, analyze, and
exploit the full potential of the new electromagnetic data. To reap the full
benefit of the high-precision electromagnetic data, new high-statistics data
from measurements with meson beams, with good angle and energy coverage for a
wide range of reactions, are critically needed to advance our knowledge in
baryon and meson spectroscopy and other related areas of hadron physics. To
address this situation, a state of-the-art meson-beam facility needs to be
constructed. The present paper summarizes unresolved issues in hadron physics
and outlines the vast opportunities and advances that only become possible with
such a facility.Comment: 46 pages, 10 figures, 4 table
Multibreather and vortex breather stability in Klein--Gordon lattices: Equivalence between two different approaches
In this work, we revisit the question of stability of multibreather
configurations, i.e., discrete breathers with multiple excited sites at the
anti-continuum limit of uncoupled oscillators. We present two methods that
yield quantitative predictions about the Floquet multipliers of the linear
stability analysis around such exponentially localized in space, time-periodic
orbits, based on the Aubry band method and the MacKay effective Hamiltonian
method and prove that their conclusions are equivalent. Subsequently, we
showcase the usefulness of the methods by a series of case examples including
one-dimensional multi-breathers, and two-dimensional vortex breathers in the
case of a lattice of linearly coupled oscillators with the Morse potential and
in that of the discrete model
Life prediction and constitutive models for engine hot section anisotropic materials program
This report presents the results of the first year of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and/or fatigue data, tests were conducted on coated and uncoated PWA 1480 specimens tensilely loaded in the 100 , 110 , 111 , and 123 directions. A literature survey of constitutive models was completed for both single crystal alloys and metallic coating materials; candidate models were selected. One constitutive model under consideration for single crystal alloys applies Walker's micromechanical viscoplastic formulation to all slip systems participating in the single crystal deformation. The constitutive models for the overlay coating correlate the viscoplastic data well. For the aluminide coating, a unique test method is under development. LCF and TMF tests are underway. The two coatings caused a significant drop in fatigue life, and each produced a much different failure mechanism
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