3,769 research outputs found
Ground state of a confined Yukawa plasma
The ground state of an externally confined one-component Yukawa plasma is
derived analytically. In particular, the radial density profile is computed.
The results agree very well with computer simulations on three-dimensional
spherical Coulomb crystals. We conclude in presenting an exact equation for the
density distribution for a confinement potential of arbitrary geometry.Comment: 5 pages, 4 figure
Harvesting Entities from the Web Using Unique Identifiers -- IBEX
In this paper we study the prevalence of unique entity identifiers on the
Web. These are, e.g., ISBNs (for books), GTINs (for commercial products), DOIs
(for documents), email addresses, and others. We show how these identifiers can
be harvested systematically from Web pages, and how they can be associated with
human-readable names for the entities at large scale.
Starting with a simple extraction of identifiers and names from Web pages, we
show how we can use the properties of unique identifiers to filter out noise
and clean up the extraction result on the entire corpus. The end result is a
database of millions of uniquely identified entities of different types, with
an accuracy of 73--96% and a very high coverage compared to existing knowledge
bases. We use this database to compute novel statistics on the presence of
products, people, and other entities on the Web.Comment: 30 pages, 5 figures, 9 tables. Complete technical report for A.
Talaika, J. A. Biega, A. Amarilli, and F. M. Suchanek. IBEX: Harvesting
Entities from the Web Using Unique Identifiers. WebDB workshop, 201
Modeling Quantum Optical Components, Pulses and Fiber Channels Using OMNeT++
Quantum Key Distribution (QKD) is an innovative technology which exploits the
laws of quantum mechanics to generate and distribute unconditionally secure
cryptographic keys. While QKD offers the promise of unconditionally secure key
distribution, real world systems are built from non-ideal components which
necessitates the need to model and understand the impact these non-idealities
have on system performance and security. OMNeT++ has been used as a basis to
develop a simulation framework to support this endeavor. This framework,
referred to as "qkdX" extends OMNeT++'s module and message abstractions to
efficiently model optical components, optical pulses, operating protocols and
processes. This paper presents the design of this framework including how
OMNeT++'s abstractions have been utilized to model quantum optical components,
optical pulses, fiber and free space channels. Furthermore, from our toolbox of
created components, we present various notional and real QKD systems, which
have been studied and analyzed.Comment: Published in: A. F\"orster, C. Minkenberg, G. R. Herrera, M. Kirsche
(Eds.), Proc. of the 2nd OMNeT++ Community Summit, IBM Research - Zurich,
Switzerland, September 3-4, 201
Endovascular Treatment of Renal Artery Bifurcation Stenoses with Branched Balloon Angioplasty
An 85-year-old man with left sided single kidney presented with end-stage renal failure after an acute intestinal bleeding. A complex bifurcational stenoses distally to a 6 months previously implanted ostial stent in the left renal artery was found on duplex imaging and angiogram. These two de-novo stenoses in the distal main renal artery and the proximal segment of the lower branch were simultaneously treated with a ultra-low profile, monorail bifurcation balloon catheter system (Avion Bifurcation RX2™, Invatec, Italy) that consists of a main vessel balloon (20/3.5mm) and a side vessel balloon (20/2.75mm). One day and three months postinterventionally, duplex ultrasound demonstrated no recurrent stenoses. Bifurcation balloon catheter systems for complex renal artery stenosis are discussed
Local electrical tuning of the nonlocal signals in a Cooper pair splitter
A Cooper pair splitter consists of a central superconducting contact, S, from
which electrons are injected into two parallel, spatially separated quantum
dots (QDs). This geometry and electron interactions can lead to correlated
electrical currents due to the spatial separation of spin-singlet Cooper pairs
from S. We present experiments on such a device with a series of bottom gates,
which allows for spatially resolved tuning of the tunnel couplings between the
QDs and the electrical contacts and between the QDs. Our main findings are
gate-induced transitions between positive conductance correlation in the QDs
due to Cooper pair splitting and negative correlations due to QD dynamics.
Using a semi-classical rate equation model we show that the experimental
findings are consistent with in-situ electrical tuning of the local and
nonlocal quantum transport processes. In particular, we illustrate how the
competition between Cooper pair splitting and local processes can be optimized
in such hybrid nanostructures.Comment: 9 pages, 6 figures, 2 table
Betanidin pKa prediction using DFT methods
Betalains can be used in food, drugs, and cosmetic industries and have shown their bioactive potential. These properties are strongly influenced by pH and other physicochemical conditions. The pKa values for the polyprotic Betanidin (Bd) molecule are unknown, and they are crucial to elucidate the oxidation mechanism in which its pigment is involved. In the present study, the values of pKa for all protic groups of Bd were analyzed using five hybrid density functionals (B3LYP, B3PW91, ωB97XD, PBE0, and M06-2X), five basis sets (6-31+G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d,p), and 6-311++G(d,p)) and the solvation model based on density (SMD) implicit solvation model. Moreover, one and three explicit water molecules were added to improve the solvation free energy values. Furthermore, the values of pKa of betanin, betalamic acid, and cyclo-dihydroxyphenylalanine (DOPA) were studied. Based on these analyses, we propose the acid-base behavior of Bd in water and develop new tools to understand their chemical reactivity.Fil: Rodriguez, Sergio A.. Universidad Nacional de Santiago del Estero. Facultad de AgronomĂa y Agroindustrias. Instituto de Ciencias QuĂmicas; ArgentinaFil: Baumgartner, Maria Teresa del V.. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Departamento de QuĂmica Orgánica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; Argentin
Multi-Channel Calibration for Airborne PostDoppler Space-Time Adaptive Processing
This paper presents a fast and efficient multichannel calibration algorithm for along-track systems, which in particular is evaluated for the post-Doppler space-time adaptive processing (PD STAP) technique. The calibration algorithm corrects the phase and magnitude offsets among the receiving channels, estimates and compensates the Doppler centroid variation caused by atmospheric turbulences by using the attitude angles of the antenna array. Important parameters and offsets are estimated directly from the radar rangecompressed data. The proposed algorithm is compared with the state-of-the-art Digital Channel Balancing technique based on real multi-channel X-band data acquired by the DLR’s airborne system F-SAR. The experimental results are shown and discussed in the frame of traffic monitoring applications
Long-term variability of AGN at hard X-rays
Variability at all observed wavelengths is a distinctive property of AGN.
Hard X-rays provide us with a view of the innermost regions of AGN, mostly
unbiased by absorption along the line of sight. Swift/BAT offers the unique
opportunity to follow, on time scales of days to years and with a regular
sampling, the 14-195 keV emission of the largest AGN sample available up to
date for this kind of investigation. We study the amplitude of the variations,
and their dependence on sub-class and on energy, for a sample of 110 radio
quiet and radio loud AGN selected from the BAT 58-month survey. About 80% of
the AGN in the sample are found to exhibit significant variability on months to
years time scales, radio loud sources being the most variable. The amplitude of
the variations and their energy dependence are incompatible with variability
being driven at hard X-rays by changes of the absorption column density. In
general, the variations in the 14-24 and 35-100 keV bands are well correlated,
suggesting a common origin of the variability across the BAT energy band.
However, radio quiet AGN display on average 10% larger variations at 14-24 keV
than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert
galaxies with detectable spectral variability on month time scale. In addition,
sources with harder spectra are found to be more variable than softer ones.
These properties are generally consistent with a variable power law continuum,
in flux and shape, pivoting at energies >~ 50 keV, to which a constant
reflection component is superposed. When the same time scales are considered,
the timing properties of AGN at hard X-rays are comparable to those at lower
energies, with at least some of the differences possibly ascribable to
components contributing differently in the two energy domains (e.g.,
reflection, absorption).Comment: 17 pages, 11 figures, accepted for publication in A&
- …