8,045 research outputs found
Node counting in wireless ad-hoc networks
We study wireless ad-hoc networks consisting of small microprocessors with
limited memory, where the wireless communication between the processors can be highly unreliable. For this setting, we propose a number of algorithms to estimate the number of nodes in the network, and the number of direct neighbors of each node. The algorithms are simulated, allowing comparison of their performance
Determination of confusion noise for far-infrared measurements
We present a detailed assessment of the far-infrared confusion noise imposed
on measurements with the ISOPHOT far-infrared detectors and cameras aboard the
ISO satellite. We provide confusion noise values for all measurement
configurations and observing modes of ISOPHOT in the 90<=lambda<=200um
wavelength range. Based on these results we also give estimates for cirrus
confusion noise levels at the resolution limits of current and future
instruments of infrared space telescopes: Spitzer/MIPS, ASTRO-F/FIS and
Herschel/PACS.Comment: A&A accepted; FITS files and appendices are available at:
http://www.konkoly.hu/staff/pkisscs/confnoise
The 106Cd(α, α)106Cd elastic scattering in a wide energy range for γ process studies
Date of Acceptance: 15/04/2015Alpha elastic scattering angular distributions of the 106Cd(α, α)106Cd reaction were measured at three energies around the Coulomb barrier to provide a sensitive test for the α + nucleus optical potential parameter sets. Furthermore, the new high precision angular distributions, together with the data available from the literature were used to study the energy dependence of the locally optimized α + nucleus optical potential in a wide energy region ranging from ELab=27.0MeV down to 16.1 MeV.The potentials under study are a basic prerequisite for the prediction of α-induced reaction cross sections and thus, for the calculation of stellar reaction rates used for the astrophysical γ process. Therefore, statistical model predictions using as input the optical potentials discussed in the present work are compared to the available 106Cd + alpha cross section data.Peer reviewe
Oscillations in Arcturus from WIRE photometry
Observations of the red giant Arcturus (Alpha Boo) obtained with the star
tracker on the Wide Field Infrared Explorer (WIRE) satellite during a baseline
of 19 successive days in 2000 July-August are analysed. The amplitude spectrum
has a significant excess of power at low-frequencies. The highest peak is at
about 4.1 micro-Hz (2.8 d), which is in agreement with previous ground-based
radial velocity studies. The variability of Arcturus can be explained by sound
waves, but it is not clear whether these are coherent p-mode oscillations or a
single mode with a short life-time.Comment: 6 pages, 1 Latex file, 4 .eps figures, 2 .sty files, ApJL, 591, L151
See erratum (astro-ph/0308424
A class of pairwise models for epidemic dynamics on weighted networks
In this paper, we study the (susceptible-infected-susceptible) and
(susceptible-infected-removed) epidemic models on undirected, weighted
networks by deriving pairwise-type approximate models coupled with
individual-based network simulation. Two different types of
theoretical/synthetic weighted network models are considered. Both models start
from non-weighted networks with fixed topology followed by the allocation of
link weights in either (i) random or (ii) fixed/deterministic way. The pairwise
models are formulated for a general discrete distribution of weights, and these
models are then used in conjunction with network simulation to evaluate the
impact of different weight distributions on epidemic threshold and dynamics in
general. For the dynamics, the basic reproductive ratio is
computed, and we show that (i) for both network models is maximised if
all weights are equal, and (ii) when the two models are equally matched, the
networks with a random weight distribution give rise to a higher value.
The models are also used to explore the agreement between the pairwise and
simulation models for different parameter combinations
A Generic Framework and Methodology for Implementing Science Gateways for Analysing Molecular Docking Results
Molecular docking and virtual screening experiments require large computational and data resources and high-level user interfaces in the form of science gateways. While science gateways supporting such experiments are relatively common, there is a clearly identified need to design and implement more complex environments for further analysis of docking results. This paper describes a generic framework and a related methodology that supports the efficient development of such environments. The framework is modular enabling the reuse of already existing components. The methodology is agile and encourages the input and participation of end-users. A prototype implementation, based on the framework and methodology, of a science-gateway-based molecular docking environment for recommending a ligand-protein pair for next docking experiment is also presented and evaluated
Determination of the cosmic far-infrared background level with the ISOPHOT instrument
The cosmic infrared background (CIRB) consists mainly of the integrated light
of distant galaxies. In the far-infrared the current estimates of its surface
brightness are based on the measurements of the COBE satellite. Independent
confirmation of these results is still needed from other instruments. In this
paper we derive estimates of the far-infrared CIRB using measurements made with
the ISOPHOT instrument aboard the ISO satellite. The results are used to seek
further confirmation of the CIRB levels that have been derived by various
groups using the COBE data. We study three regions of very low cirrus emission.
The surface brightness observed with the ISOPHOT instrument at 90, 150, and 180
um is correlated with hydrogen 21 cm line data from the Effelsberg radio
telescope. Extrapolation to zero hydrogen column density gives an estimate for
the sum of extragalactic signal plus zodiacal light. The zodiacal light is
subtracted using ISOPHOT data at shorter wavelengths. Thus, the resulting
estimate of the far-infrared CIRB is based on ISO measurements alone. In the
range 150 to 180 um, we obtain a CIRB value of 1.08+-0.32+-0.30 MJy/sr quoting
statistical and systematic errors separately. In the 90 um band, we obtain a
2-sigma upper limit of 2.3 MJy/sr. The estimates derived from ISOPHOT
far-infrared maps are consistent with the earlier COBE results.Comment: Accepted for publication in A&A, 17 page
Molecular docking with Raccoon2 on clouds: extending desktop applications with cloud computing
Molecular docking is a computer simulation that predicts the binding affinity between two molecules, a ligand and a receptor. Large-scale docking simulations, using one receptor and many ligands, are known as structure-based virtual screening. Often used in drug discovery, virtual screening can be very computationally demanding. This is why user-friendly domain-specific web or desktop applications that enable running simulations on powerful computing infrastructures have been created. Cloud computing provides on-demand availability, pay-per-use pricing, and great scalability which can improve the performance and efficiency of scientific applications. This paper investigates how domain-specific desktop applications can be extended to run scientific simulations on various clouds. A generic approach based on scientific workflows is proposed, and a proof of concept is implemented using the Raccoon2 desktop application for virtual screening, WS-PGRADE workflows, and gUSE services with the CloudBroker platform. The presented analysis illustrates that this approach of extending a domain-specific desktop application can run workflows on different types of clouds, and indeed makes use of the on-demand scalability provided by cloud computing. It also facilitates the execution of virtual screening simulations by life scientists without requiring them to abandon their favourite desktop environment and providing them resources without major capital investment
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