632 research outputs found
Banner Advertisements Scheduling to Maximize Space Utilization
One of the commercial Internet applications is banner advertisement, which is also the major source of
income for portal websites. Limited research works address the issues of efficiently scheduling advertisement requests into
available advertisement banners in view of profitably. This paper proposes a new model for scheduling banner
advertisements that more closely resembles the Internet business world. In the proposed model, we apply a feasible time
window to each candidate order, and schedule advertisements into various predefined banner spaces on the webpage. This
approach allows different pricing strategies according to banner types and is contrary to previous research models that
schedule and price by banner space sharing. Each order for ad space will demand a certain frequency for each type of
banner. The goal is to select and schedule requests to achieve the maximum ad capacity utilization. We first give a
mathematical formulation to formally describe the problem. Due to the computational complexity of the studied problem,
we seek to produce approximate solutions in a reasonable time. A three-phase heuristic is developed to cope with this
problem. In addition, an upper bound on profits is developed. Computational experiments are designed to examine the
performance of the heuristic. Statistics from the experiments reveal that the heuristic can successfully fill up to 97% of ad
spaces
Peripheral fillings of relatively hyperbolic groups
A group theoretic version of Dehn surgery is studied. Starting with an
arbitrary relatively hyperbolic group we define a peripheral filling
procedure, which produces quotients of by imitating the effect of the Dehn
filling of a complete finite volume hyperbolic 3--manifold on the
fundamental group . The main result of the paper is an algebraic
counterpart of Thurston's hyperbolic Dehn surgery theorem. We also show that
peripheral subgroups of 'almost' have the Congruence Extension Property and
the group is approximated (in an algebraic sense) by its quotients obtained
by peripheral fillings. Various applications of these results are discussed.Comment: The difference with the previous version is that Proposition 3.2 is
proved for quasi--geodesics instead of geodesics. This allows to simplify the
exposition in the last section. To appear in Invent. Mat
GaN and InN nanowires grown by MBE: a comparison
Morphological, optical and transport properties of GaN and InN nanowires
grown by molecular beam epitaxy (MBE) have been studied. The differences
between the two materials in respect to growth parameters and optimization
procedure was stressed. The nanowires crystalline quality has been investigated
by means of their optical properties. A comparison of the transport
characteristics was given. For each material a band schema was shown, which
takes into account transport and optical features and is based on Fermi level
pinning at the surface.Comment: 5 pages, 5 figure
Sequence-dependent structure/function relationships of catalytic peptide-enabled gold nanoparticles generated under ambient synthetic conditions
YesPeptide-enabled nanoparticle (NP) synthesis routes can create and/or assemble functional nanomaterials under environmentally friendly conditions, with properties dictated by complex interactions at the biotic/abiotic interface. Manipulation of this interface through sequence modification can provide the capability for material properties to be tailored to create enhanced materials for energy, catalysis, and sensing applications. Fully realizing the potential of these materials requires a comprehensive understanding of sequence-dependent structure/function relationships that is presently lacking. In this work, the atomic-scale structures of a series of peptide-capped Au NPs are determined using a combination of atomic pair distribution function analysis of high-energy X-ray diffraction data and advanced molecular dynamics (MD) simulations. The Au NPs produced with different peptide sequences exhibit varying degrees of catalytic activity for the exemplar reaction 4-nitrophenol reduction. The experimentally derived atomic-scale NP configurations reveal sequence-dependent differences in structural order at the NP surface. Replica exchange with solute-tempering MD simulations are then used to predict the morphology of the peptide overlayer on these Au NPs and identify factors determining the structure/catalytic properties relationship. We show that the amount of exposed Au surface, the underlying surface structural disorder, and the interaction strength of the peptide with the Au surface all influence catalytic performance. A simplified computational prediction of catalytic performance is developed that can potentially serve as a screening tool for future studies. Our approach provides a platform for broadening the analysis of catalytic peptide-enabled metallic NP systems, potentially allowing for the development of rational design rules for property enhancemenAir Force Office for Scientific Research (Grant #FA9550-12-1-0226, RRN; AFOSR LRIR) and DOE-BES grant DE-SC0006877, fellowship support from the National Research Council Research Associateshi
Scaling predictions for radii of weakly bound triatomic molecules
The mean-square radii of the molecules He, HeLi,
HeLi and HeNa are calculated using a three-body model
with contact interactions. They are obtained from a universal scaling function
calculated within a renormalized scheme for three particles interacting through
pairwise Dirac-delta interaction. The root-mean-square distance between two
atoms of mass in a triatomic molecule are estimated to be of de order of
, where is the dimer and the
trimer binding energies, and is a constant (varying from
to ) that depends on the ratio between and . Considering
previous estimates for the trimer energies, we also predict the sizes of
Rubidium and Sodium trimers in atomic traps.Comment: 7 pages, 2 figure
Genes of the antioxidant system of the honey bee: annotation and phylogeny
Antioxidant enzymes perform a variety of vital functions including the reduction of life-shortening oxidative damage. We used the honey bee genome sequence to identify the major components of the honey bee antioxidant system. A comparative analysis of honey bee with Drosophila melanogaster and Anopheles gambiae shows that although the basic components of the antioxidant system are conserved, there are important species differences in the number of paralogs. These include the duplication of thioredoxin reductase and the expansion of the thioredoxin family in fly; lack of expansion of the Theta, Delta and Omega GST classes in bee and no expansion of the Sigma class in dipteran species. The differential expansion of antioxidant gene families among honey bees and dipteran species might reflect the marked differences in life history and ecological niches between social and solitary species
A preview of JWST metallicity studies at cosmic noon: the first detection of auroral [O II] emission at high redshift
Galaxie
Acoustic phonon exchange, attractive interactions, and the Wentzel-Bardeen singularity in single-wall nanotubes
We derive the effective low-energy theory for interacting electrons in
metallic single-wall carbon nanotubes taking into account acoustic phonon
exchange within a continuum elastic description. In many cases, the nanotube
can be described as a standard Luttinger liquid with possibly attractive
interactions. We predict surprisingly strong attractive interactions for thin
nanotubes. Once the tube radius reaches a critical value \AA, the Wentzel-Bardeen singularity is approached, accompanied by strong
superconducting fluctuations. The surprisingly large indicates that this
singularity could be reached experimentally. We also discuss the conditions for
a Peierls transition due to acoustic phonons.Comment: 11 pages, 2 figures, final version to be published in Phys. Rev.
The ^4He trimer as an Efimov system
We review the results obtained in the last four decades which demonstrate the
Efimov nature of the He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal
devoted to Efimov physic
Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV I: pion-induced results and hadronic parameters
We present a nucleon resonance analysis by simultaneously considering all
pion- and photon-induced experimental data on the final states gamma N, pi N, 2
pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass
up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the
resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The
omega N production mechanism is dominated by large P_{11}(1710) and
P_{13}(1900) contributions. In this first part, we present the results of the
pion-induced reactions and the extracted resonance and background properties
with emphasis on the difference between global and purely hadronic fits.Comment: 54 pages, 26 figures, discussion extended, typos corrected,
references updated, to appear in Phys. Rev.
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