342 research outputs found
Surface Polymer Network Model and Effective Membrane Curvature Elasticity
A microscopic model of a surface polymer network - membrane system is
introduced, with contact polymer surface interactions that can be either
repulsive or attractive and sliplinks of functionality four randomly
distributed over the supporting membrane surface anchoring the polymers to it.
For the supporting surface perturbed from a planar configuration and a small
relative number of surface sliplinks, we investigate an expansion of the free
energy in terms of the local curvatures of the surface and the surface density
of sliplinks, obtained through the application of the Balian - Bloch -
Duplantier multiple surface scattering method. As a result, the dependence of
the curvature elastic modulus, the Gaussian modulus as well as of the
spontaneous curvature of the "dressed" membrane, ~{\sl i.e.} polymer network
plus membrane matrix, is obtained on the mean polymer bulk end to end
separation and the surface density of sliplinks.Comment: 15 pages with one included compressed uuencoded figure
Atlas of the shallow-water benthic habitats of Majuro Atoll, Republic of the Marshall Islands
Digital maps of the shallow (<~30m deep) coral reef ecosystems of Majuro Atoll, Republic of the Marshall Islands, were created through visual interpretation of remote sensing imagery acquired between 2004 and 2006. Reef ecosystem features were digitized directly into a Geographic Information System. Benthic features were categorized according to a classification scheme with attributes including zone (location such as lagoon or forereef, etc.), structure (bottom type such as sand or patch reef, etc.) and percent hard bottom. This atlas consists of 27 detailed maps displaying reef zone and structure of coral ecosystems around Majuro. Adjacent maps in the atlas overlap slightly to ensure complete coverage. Maps and associated products can be used to support science and management activities on Majuro reef ecosystems including inventory, monitoring, conservation, and sustainable development applications. Maps are not to be used for navigation
Screening of Hydrodynamic Interactions in Semidilute Polymer Solutions: A Computer Simulation Study
We study single-chain motion in semidilute solutions of polymers of length N
= 1000 with excluded-volume and hydrodynamic interactions by a novel algorithm.
The crossover length of the transition from Zimm (short lengths and times) to
Rouse dynamics (larger scales) is proportional to the static screening length.
The crossover time is the corresponding Zimm time. Our data indicate Zimm
behavior at large lengths but short times. There is no hydrodynamic screening
until the chains feel constraints, after which they resist the flow:
"Incomplete screening" occurs in the time domain.Comment: 3 figure
Roper Resonance and S_{11}(1535) from Lattice QCD
Using the constrained curve fitting method and overlap fermions with the
lowest pion mass at , we observe that the masses of the first
positive and negative parity excited states of the nucleon tend to cross over
as the quark masses are taken to the chiral limit. Both results at the physical
pion mass agree with the experimental values of the Roper resonance
() and (). This is seen for the first
time in a lattice QCD calculation. These results are obtained on a quenched
Iwasaki lattice with . We also extract the
ghost states (a quenched artifact) which are shown to decouple from
the nucleon interpolation field above . From the
quark mass dependence of these states in the chiral region, we conclude that
spontaneously broken chiral symmetry dictates the dynamics of light quarks in
the nucleon.Comment: 10 pages, 5 figures, revised version to appear in PL
Charmonium Spectrum from Quenched QCD with Overlap Fermions
We present preliminary results using overlap fermions for the charmonium
spectrum, in particular for hyperfine splitting. Simulations are performed on
lattices, with Wilson gauge action at .
Depending on how the scale is set, we obtain 104(5) MeV (using
) or 88(4) MeV (using =0.5 fm) for the hyperfine
splitting.Comment: 3 pages, 5 fiugres. Talk presented at Lattice 2004 (heavy
Bcc He as a Coherent Quantum Solid
In this work we investigate implications of the quantum nature of bcc %
He. We show that it is a unique solid phase with both a lattice structure and
an Off-Diagonal Long Range Order of coherently oscillating local electric
dipole moments. These dipoles arise from the local motion of the atoms in the
crystal potential well, and oscillate in synchrony to reduce the dipolar
interaction energy. The dipolar ground-state is therefore found to be a
coherent state with a well defined global phase and a three-component complex
order parameter. The condensation energy of the dipoles in the bcc phase
stabilizes it over the hcp phase at finite temperatures. We further show that
there can be fermionic excitations of this ground-state and predict that they
form an optical-like branch in the (110) direction. A comparison with
'super-solid' models is also discussed.Comment: 12 pages, 8 figure
The Australian dingo is an early offshoot of modern breed dogs
Dogs are uniquely associated with human dispersal and bring transformational insight into the domestication process. Dingoes represent an intriguing case within canine evolution being geographically isolated for thousands of years. Here, we present a high-quality de novo assembly of a pure dingo (CanFam_DDS). We identified large chromosomal differences relative to the current dog reference (CanFam3.1) and confirmed no expanded pancreatic amylase gene as found in breed dogs. Phylogenetic analyses using variant pairwise matrices show that the dingo is distinct from five breed dogs with 100% bootstrap support when using Greenland wolf as the outgroup. Functionally, we observe differences in methylation patterns between the dingo and German shepherd dog genomes and differences in serum biochemistry and microbiome makeup. Our results suggest that distinct demographic and environmental conditions have shaped the dingo genome. In contrast, artificial human selection has likely shaped the genomes of domestic breed dogs after divergence from the dingo
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Critical aspects of three-dimensional anisotropic spin-glass models
We study the three-dimensional Ising model with a longitudinal
anisotropic bond randomness on the simple cubic lattice. The random exchange
interaction is applied only in the direction, whereas in the other two
directions, - planes, we consider ferromagnetic exchange. By implementing
an effective parallel tempering scheme, we outline the phase diagram of the
model and compare it to the corresponding isotropic one, as well as to a
previously studied anisotropic (transverse) case. We present a detailed
finite-size scaling analysis of the ferromagnetic - paramagnetic and spin glass
- paramagnetic transition lines, and we also discuss the ferromagnetic - spin
glass transition regime. We conclude that the present model shares the same
universality classes with the isotropic model, but at the symmetric point has a
considerably higher transition temperature from the spin-glass state to the
paramagnetic phase. Our data for the ferromagnetic - spin glass transition line
are supporting a forward behavior in contrast to the reentrant behavior of the
isotropic model.Comment: 10 pages, 9 eps figures, 1 table, corrected symbolis
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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