5,762 research outputs found
Diagnostic Efficacy of Morphological Characters of Larval \u3ci\u3eTramea Lacerata\u3c/i\u3e Hagen and \u3ci\u3eTramea Onusta\u3c/i\u3e Hagen (Odonata: Libellulidae) in the Prairie Region of Missouri
Distinguishing among species of larvae of the dragonfly genus Tramea historically has been problematic, largely due to conflicting characterizations of the larvae of T. lacerata Hagen and T. onusta Hagen (Odonata: Libellulidae) in the literature. The various systematic treatments usually focused on relative lengths of morphological characters to distinguish the species, but often contradicted one another and themselves as to what the diagnostic values actually were. We traced much of the confusion back to errors in the original larval description of T. onusta. We used morphometric analyses to determine the efficacy of previously published characterizations to distinguish between the larvae of T. lacerata and T. onusta. Previous characterizations, especially those involving relative lengths of the caudal appendages, were generally found to be inadequate for distinguishing larvae of the two species. The most reliable characteristic for distinguishing the two species was found to be the length of the epiproct relative to the length of the paraprocts
Evaporation of a Kerr black hole by emission of scalar and higher spin particles
We study the evolution of an evaporating rotating black hole, described by
the Kerr metric, which is emitting either solely massless scalar particles or a
mixture of massless scalar and nonzero spin particles. Allowing the hole to
radiate scalar particles increases the mass loss rate and decreases the angular
momentum loss rate relative to a black hole which is radiating nonzero spin
particles. The presence of scalar radiation can cause the evaporating hole to
asymptotically approach a state which is described by a nonzero value of . This is contrary to the conventional view of black hole
evaporation, wherein all black holes spin down more rapidly than they lose
mass. A hole emitting solely scalar radiation will approach a final asymptotic
state described by . A black hole that is emitting scalar
particles and a canonical set of nonzero spin particles (3 species of
neutrinos, a single photon species, and a single graviton species) will
asymptotically approach a nonzero value of only if there are at least 32
massless scalar fields. We also calculate the lifetime of a primordial black
hole that formed with a value of the rotation parameter , the minimum
initial mass of a primordial black hole that is seen today with a rotation
parameter , and the entropy of a black hole that is emitting scalar or
higher spin particles.Comment: 22 pages, 13 figures, RevTeX format; added clearer descriptions for
variables, added journal referenc
Accurate molecular energies by extrapolation of atomic energies using an analytic quantum mechanical model
Using a new analytic quantum mechanical method based on Slater's Xalpha
method, we show that a fairly accurate estimate of the total energy of a
molecule can be obtained from the exact energies of its constituent atoms. The
mean absolute error in the total energies thus determined for the G2 set of 56
molecules is about 16 kcal/mol, comparable to or better than some popular pure
and hybrid density functional models.Comment: 5 pages, REVTE
South Carolina Department of Transportation and the United States Department of Agriculture, Partnering for Success in Migratory Bird Treaty Act Compliance: A Case Study
The South Carolina Department of Transportation (SCDOT) is responsible for maintaining over 8,400 bridges statewide and several species of migratory birds use these structures as nesting locations. These birds, including their nests and eggs, are protected under the Migratory Bird Treaty Act (MBTA). During a review of MBTA compliance in 2014, SCDOT concluded that they had no procedures in place to allow take to occur when active migratory bird nests were found within project limits. Project delays were the only management method available when active nests were found. SCDOT entered a Cooperative Service Agreement with USDA Wildlife Services (WS) in 2016 to address MBTA compliance on SCDOT projects. The agreement called for WS to manage migratory birds at bridge projects to prevent project delays. WS would repeatedly visit bridge projects, survey the bridges for nests, and remove the nests before they became active. Since 2016, WS has inspected 233 bridges and migratory birds were present at approximately 66% of those bridges with a total of 9,250 inactive nests being removed using a variety of methods. Since the partnership’s inception, construction delays due to migratory birds have been completely avoided with an average cost per project of $1,525. With the passage of a new motor fuel user fee in South Carolina, SCDOT plans to replace 465 bridges over the next 10 years. This increase in work will require continued development and implementation of the partnership to effectively meet the rapidly growing transportation needs while minimizing impacts to species protected under the MBTA
Duality of Bures and Shape Distances with Implications for Comparing Neural Representations
A multitude of (dis)similarity measures between neural network
representations have been proposed, resulting in a fragmented research
landscape. Most of these measures fall into one of two categories.
First, measures such as linear regression, canonical correlations analysis
(CCA), and shape distances, all learn explicit mappings between neural units to
quantify similarity while accounting for expected invariances. Second, measures
such as representational similarity analysis (RSA), centered kernel alignment
(CKA), and normalized Bures similarity (NBS) all quantify similarity in summary
statistics, such as stimulus-by-stimulus kernel matrices, which are already
invariant to expected symmetries. Here, we take steps towards unifying these
two broad categories of methods by observing that the cosine of the Riemannian
shape distance (from category 1) is equal to NBS (from category 2). We explore
how this connection leads to new interpretations of shape distances and NBS,
and draw contrasts of these measures with CKA, a popular similarity measure in
the deep learning literature
A Critical View of Current State of Phytotechnologies to Remediate Soils: Still a Promising Tool?
Phytotechnologies are often shown as an emerging tool to remediate contaminated soils. Research in this field has resulted in many important findings relating to plant and soil sciences. However, there have been scant private and public investments and little commercial success with this technology. Here, we investigate the barriers to the adoption of phytotechnologies and determine whether it is still a fertile area for future research. The terminology used in phytotechnologies includes a confusing mish-mash of terms relating to concepts and processes increasing the difficulty of developing a unique commercial image. We argue that the commercial success of phytotechnologies depends on the generation of valuable biomass on contaminated land, rather than a pure remediation technique that may not compare favourably with the costs of inaction or alternative technologies. Valuable biomass includes timber, bioenergy, feedstock for pyrolosis, biofortified products, or ecologically important species
Use of small specimen creep data in component life management: a review
Small specimen creep testing techniques are novel mechanical test techniques that have been developed over the past 25 years. They mainly include the sub-size uniaxial test, the small punch creep test, the impression creep test, the small ring creep test and the two-bar creep test. This paper outlines the current methods in practice for data interpretation as well as the state-of-the-art procedures for conducting the tests. Case studies for the use of impression creep testing and material strength ranking of creep resistant steels are reviewed along with the requirement for the standardisation of the impression creep test method. A database of small specimen creep testing is required to prove the validity of the tests
Spinning Down a Black Hole With Scalar Fields
We study the evolution of a Kerr black hole emitting scalar radiation via the
Hawking process. We show that the rate at which mass and angular momentum are
lost by the black hole leads to a final evolutionary state with nonzero angular
momentum, namely .Comment: 4 pages (including 3 postscript figures), Revtex, uses epsf.tex,
twocolumn.sty and header.sty (included). Submitted to Physical Review Letter
Dirac-Brueckner Hartree-Fock Approach: from Infinite Matter to Effective Lagrangians for Finite Systems
One of the open problems in nuclear structure is how to predict properties of
finite nuclei from the knowledge of a bare nucleon-nucleon interaction of the
meson-exchange type. We point out that a promising starting point consists in
Dirac-Brueckner-Hartree-Fock (DBHF) calculations us- ing realistic
nucleon-nucleon interactions like the Bonn potentials, which are able to
reproduce satisfactorily the properties of symmetric nuclear matter without the
need for 3-body forces, as is necessary in non-relativistic BHF calculations.
However, the DBHF formalism is still too com- plicated to be used directly for
finite nuclei. We argue that a possible route is to define effective
Lagrangians with density-dependent nucleon-meson coupling vertices, which can
be used in the Relativistic Hartree (or Relativistic Mean Field (RMF)) or
preferrably in the Relativistic Hartree- Fock (RHF) approach. The
density-dependence is matched to the nuclear matter DBHF results. We review the
present status of nuclear matter DBHF calculations and discuss the various
schemes to construct the self-energy, which lead to differences in the
predictions. We also discuss how effective Lagrangians have been constructed
and are used in actual calculations. We point out that completely consistent
calculations in this scheme still have to be performed.Comment: 16 pages, to be published in Journal of Physics G: Nuclear and
Particle Physics, special issue
How Birds Combat Ectoparasites
Birds are plagued by an impressive diversity of ectoparasites, ranging from feather-feeding lice, to feather-degrading bacteria. Many of these ectoparasites have severe negative effects on host fitness. It is therefore not surprising that selection on birds has favored a variety of possible adaptations for dealing with ectoparasites. The functional significance of some of these defenses has been well documented. Others have barely been studied, much less tested rigorously. In this article we review the evidence--or lack thereof--for many of the purported mechanisms birds have for dealing with ectoparasites. We concentrate on features of the plumage and its components, as well as anti-parasite behaviors. In some cases, we present original data from our own recent work. We make recommendations for future studies that could improve our understanding of this poorly known aspect of avian biology
- …