92,828 research outputs found
Social reference: Aggregating online usage of scientific literature in CiteULike for clustering academic resources
Citation-based methods have been widely studied and employed for clustering academic resources and mapping science. Although effective, these methods suffer from citation delay. In this study, we extend reference and citation analysis to a broader notion from social perspective. We coin the term "social reference" to refer to the references of literatures in social academic web environment. We propose clustering methods using social reference information from CiteULike. We experiment for journal clustering and author clustering using social reference and compare with citation-based methods. Our experiments indicate: first, social reference implies connections among literatures which are as effective as citation in clustering academic resources; second, in practical settings, social reference-based clustering methods are not as effective as citation-based ones due to the sparseness of social reference data, but they can outperform in clustering new resources that have few citation. © 2011 Authors
Security-oriented data grids for microarray expression profiles
Microarray experiments are one of the key ways in which gene activity can be identified and measured thereby shedding light and understanding for example on biological processes. The BBSRC funded Grid enabled Microarray Expression Profile Search (GEMEPS) project has developed an infrastructure which allows post-genomic life science researchers to ask and answer the following questions: who has undertaken microarray experiments that are in some way similar or relevant to mine; and how similar were these relevant experiments? Given that microarray experiments are expensive to undertake and may possess crucial information for future exploitation (both academically and commercially), scientists are wary of allowing unrestricted access to their data by the wider community until fully exploited locally. A key requirement is thus to have fine grained security that is easy to establish and simple (or ideally transparent) to use across inter-institutional virtual organisations. In this paper we present an enhanced security-oriented data Grid infrastructure that supports the definition of these kinds of queries and the analysis and comparison of microarray experiment results
Systematic Effective Field Theory Investigation of Spiral Phases in Hole-Doped Antiferromagnets on the Honeycomb Lattice
Motivated by possible applications to the antiferromagnetic precursor of the
high-temperature superconductor NaCoOyHO, we use a systematic
low-energy effective field theory for magnons and holes to study different
phases of doped antiferromagnets on the honeycomb lattice. The effective action
contains a leading single-derivative term, similar to the Shraiman-Siggia term
in the square lattice case, which gives rise to spirals in the staggered
magnetization. Depending on the values of the low-energy parameters, either a
homogeneous phase with four or a spiral phase with two filled hole pockets is
energetically favored. Unlike in the square lattice case, at leading order the
effective action has an accidental continuous spatial rotation symmetry.
Consequently, the spiral may point in any direction and is not necessarily
aligned with a lattice direction.Comment: 10 pages, 6 figure
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A micro-electro-mechanical-system-based thermal shear-stress sensor with self-frequency compensation
By applying the micro-electro-mechanical-system (MEMS) fabrication technology, we developed a micro-thermal sensor to measure surface shear stress. The heat transfer from a polysilicon heater depends on the normal velocity gradient and thus provides the surface shear stress. However, the sensitivity of the shear-stress measurements in air is less than desirable due to the low heat capacity of air. A unique feature of this micro-sensor is that the heating element, a film 1 µm thick, is separated from the substrate by a vacuum cavity 2 µm thick. The vacuum cavity prevents the conduction of heat to the substrate and therefore improves the sensitivity by an order of magnitude. Owing to the low thermal inertia of the miniature sensing element, this shear-stress micro-sensor can provide instantaneous measurements of small-scale turbulence. Furthermore, MEMS technology allows us make multiple sensors on a single chip so that we can perform distributed measurements. In this study, we use multiple polysilicon sensor elements to improve the dynamic performance of the sensor itself. It is demonstrated that the frequency-response range of a constant-current sensor can be extended from the order of 100 Hz to 100 kHz
Possible TeV Source Candidates In The Unidentified EGRET Sources
We study the -ray emission from the pulsar magnetosphere based on
outer gap models, and the TeV radiation from pulsar wind nebulae (PWNe) through
inverse Compton scattering using a one-zone model. We showed previously that
GeV radiation from the magnetosphere of mature pulsars with ages of years old can contribute to the high latitude unidentified EGRET
sources. We carry out Monte Carlo simulations of -ray pulsars in the
Galaxy and the Gould Belt, assuming the pulsar birth rate, initial position,
proper motion velocity, period, and magnetic field distribution and evolution
based on observational statistics. We select from the simulation a sample of
mature pulsars in the Galactic plane () and in the high
latitude () which could be detected by EGRET. The TeV flux from
the pulsar wind nebulae of our simulated sample through the inverse Compton
scattering by relativistic electrons on the microwave cosmic background and
synchrotron seed photons are calculated. The predicted fluxes are consistent
with the present observational constraints. We suggest that strong EGRET
sources can be potential TeV source candidates for present and future
ground-based TeV telescopes.Comment: Minor changes, MNRAS in pres
Constraint Effective Potential of the Staggered Magnetization in an Antiferromagnet
We employ an improved estimator to calculate the constraint effective
potential of the staggered magnetization in the spin quantum
Heisenberg model using a loop-cluster algorithm. The first and second moment of
the probability distribution of the staggered magnetization are in excellent
agreement with the predictions of the systematic low-energy magnon effective
field theory. We also compare the Monte Carlo data with the universal shape of
the constraint effective potential of the staggered magnetization and study its
approach to the convex effective potential in the infinite volume limit. In
this way the higher-order low-energy parameter is determined from a fit
to the numerical data
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