707 research outputs found
High abundance of a single taxon (amphipods) predicts aquatic macrophyte biodiversity in prairie wetlands
Conservation programs often aim to protect the abundance of individual species and biodiversity simultaneously. We quantified relations between amphipod densities and aquatic macrophyte (large plants and algae) diversity to test a hypothesis that biodiversity can support high abundance of a single taxonomic group. Amphipods (Gammarus lacustris and Hyalella azteca) are key forage for waterfowl and are declining in the Prairie Pothole Region of North America. We sampled a large gradient of amphipod densities (0–7050 amphipods/m3) in 49 semi-permanent wetlands, and 50% of the study wetlands had high amphipod densities (\u3e 500 amphipods/m3). Generalized linear models revealed G. lacustris and H. azteca densities increased exponentially with macrophyte diversity indices. Further, H. azteca densities were greatest at moderate levels of submersed vegetation biomass. Community analyses showed both amphipod species were positively associated with diverse macrophyte assemblages and negatively associated with high coverage of cattails (Typha spp.), a taxon that creates monotypic stands, as well as bladderwort (Utricularia spp.), a carnivorous plant. Our results indicate that amphipods could be used as an umbrella species for protecting diverse macrophyte communities in semi-permanent and permanent wetlands of North America’s Prairie Pothole Region
Remarks on Limits on String Scale from Proton Decay and Low-Energy amplitudes in Braneworld Scenario
We discuss IR limit of four-fermion scattering amplitudes in braneworld
models including intersecting-branes and SUSY SU(5) GUT version of it. With
certain compactification where instanton effect is negligible, grand
unification condition in D6-D6 intersecting-branes scenario subject to
experimental constraint on proton decay provides possibility for upper limit on
the string scale, , through relationship between the string coupling,
, and the string scale. We discuss how IR divergence is related to number
of twisted fields we have to introduce into intersection region and how it can
change IR behaviour of tree-level amplitudes in various intersecting-branes
models. Using number of twisted fields, we identify some intersecting-branes
models whose tree-level amplitudes are purely stringy in nature and
automatically proportional to at low energy. They are
consequently suppressed by the string scale. For comparison, we also derive
limit on the lower bound of the string scale from experimental constraint on
proton decay induced from purely stringy contribution in the coincident-branes
model, the limit is about TeV.Comment: 14 page
Noncommutative Inspired Black Holes in Extra Dimensions
In a recent string theory motivated paper, Nicolini, Smailagic and Spallucci
(NSS) presented an interesting model for a noncommutative inspired,
Schwarzschild-like black hole solution in 4-dimensions. The essential effect of
having noncommutative co-ordinates in this approach is to smear out matter
distributions on a scale associated with the turn-on of noncommutativity which
was taken to be near the 4-d Planck mass. In particular, NSS took this smearing
to be essentially Gaussian. This energy scale is sufficiently large that in 4-d
such effects may remain invisible indefinitely. Extra dimensional models which
attempt to address the gauge hierarchy problem, however, allow for the
possibility that the effective fundamental scale may not be far from 1
TeV, an energy regime that will soon be probed by experiments at both the LHC
and ILC. In this paper we generalize the NSS model to the case where flat,
toroidally compactified extra dimensions are accessible at the Terascale and
examine the resulting modifications in black hole properties due to the
existence of noncommutativity. We show that while many of the
noncommutativity-induced black hole features found in 4-d by NSS persist, in
some cases there can be significant modifications due the presence of extra
dimensions. We also demonstrate that the essential features of this approach
are not particularly sensitive to the Gaussian nature of the smearing employed
by NSS.Comment: 30 pages, 12 figures; slight text modifications and references adde
The critical exponents of the two-dimensional Ising spin glass revisited: Exact Ground State Calculations and Monte Carlo Simulations
The critical exponents for of the two-dimensional Ising spin glass
model with Gaussian couplings are determined with the help of exact ground
states for system sizes up to and by a Monte Carlo study of a
pseudo-ferromagnetic order parameter. We obtain: for the stiffness exponent
, for the magnetic exponent
and for the chaos exponent . From Monte Carlo simulations we
get the thermal exponent . The scaling prediction is
fulfilled within the error bars, whereas there is a disagreement with the
relation .Comment: 8 pages RevTeX, 7 eps-figures include
Dynamics of Collapse of flexible Polyelectrolytes and Polyampholytes
We provide a theory for the dynamics of collapse of strongly charged
polyelectrolytes (PEs) and flexible polyampholytes (PAs) using Langevin
equation. After the initial stage, in which counterions condense onto PE, the
mechanism of approach to the globular state is similar for PE and PA. In both
instances, metastable pearl-necklace structures form in characteristic time
scale that is proportional to N^{4/5} where N is the number of monomers. The
late stage of collapse occurs by merger of clusters with the largest one
growing at the expense of smaller ones (Lifshitz- Slyozov mechanism). The time
scale for this process T_{COLL} N. Simulations are used to support the proposed
collapse mechanism for PA and PE.Comment: 14 pages, 2 figure
Supersymmetry Without Prejudice
We begin an exploration of the physics associated with the general
CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY
breaking parameters in this scenario are chosen so as to satisfy all existing
experimental and theoretical constraints assuming that the WIMP is a
conventional thermal relic, ie, the lightest neutralino. We scan this parameter
space twice using both flat and log priors for the soft SUSY breaking mass
parameters and compare the results which yield similar conclusions. Detailed
constraints from both LEP and the Tevatron searches play a particularly
important role in obtaining our final model samples. We find that the pMSSM
leads to a much broader set of predictions for the properties of the SUSY
partners as well as for a number of experimental observables than those found
in any of the conventional SUSY breaking scenarios such as mSUGRA. This set of
models can easily lead to atypical expectations for SUSY signals at the LHC.Comment: 61 pages, 24 figs. Refs., figs, and text added, typos fixed; This
version has reduced/bitmapped figs. For a version with better figs please go
to http://www.slac.stanford.edu/~rizz
Our friend in the north: the origins, evolution and appeal of the cult of St Duthac of Tain in later Middle Ages
St Duthac of Tain was one of the most popular Scottish saints of the later middle ages. From the late fourteenth century until the reformation devotion to Duthac outstripped that of Andrew, Columba, Margaret and Mungo, and Duthac's shrine in Easter Ross became a regular haunt of James IV (1488-1513) and James V (1513-42). Hitherto historians have tacitly accepted the view of David McRoberts that Duthac was one of several local saints whose emergence and popularity in the fifteenth century was part of a wider self-consciously nationalist trend in Scottish religious practice. This study looks beyond the paradigm of nationalism to trace and explain the popularity of St Duthac from the shadowy origins of the cult to its heyday in the early sixteenth century
O PERFIL DA COMPOSIÇÃO DOS GRUPOS DE PESQUISA NA UFSC
Com a reforma universitária ocorrida na década de 60, a universidade foi reorganizada, tendo como base a modernização, para atender as mudanças que o Brasil vinha sofrendo na época do governo de Jucelino Kubichek. Entre as várias alterações que a reformar promoveu na universidade, destaca-se a indivisibilidade entre ensino, pesquisa e extensão. Também nesta mesma época houve a institucionalização da pesquisa. Assim, para promover um fluxo continuou de pesquisas foram criados os grupos de pesquisas. Com este artigo, tem-se como objetivo principal analisar o perfil da composição dos grupos de pesquisa, para tanto, foram analisados os grupos de pesquisas certificados da Universidade Federal de Santa Catariana. Os resultados da pesquisa evidenciam que o número de grupos de pesquisa na UFSC vem crescendo a cada ano, e que a maioria dos participantes dos grupos de pesquisas são classificados como pesquisadores, que podem ser professores, alunos ou técnicos e em sua grande maioria são doutores
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