3,064 research outputs found
Continuous-time quantum walks on dynamical percolation graphs
We address continuous-time quantum walks on graphs in the presence of time-
and space-dependent noise. Noise is modeled as generalized dynamical
percolation, i.e. classical time-dependent fluctuations affecting the tunneling
amplitudes of the walker. In order to illustrate the general features of the
model, we review recent results on two paradigmatic examples: the dynamics of
quantum walks on the line and the effects of noise on the performances of
quantum spatial search on the complete and the star graph. We also discuss
future perspectives, including extension to many-particle quantum walk, to
noise model for on-site energies and to the analysis of different noise
spectra. Finally, we address the use of quantum walks as a quantum probe to
characterize defects and perturbations occurring in complex, classical and
quantum, networks.Comment: 7 pages, 4 figures. Accepted for publication in EPL Perspective
Non-Markovianity by undersampling in quantum optical simulators
We unveil a novel source of non-Markovianity for the dynamics of quantum
systems, which appears when the system does not explore the full set of
dynamical trajectories in the interaction with its environment. We term this
effect non-Markovianity by undersampling and demonstrate its appearance in the
operation of an all-optical quantum simulator involving a polarization qubit
interacting with a dephasing fluctuating environment.Comment: Accepted versio
Cathepsin D and epidermal growth factor in human breast cyst fluid.
Cathespin D (Cath D) is a proteolytic enzyme secreted by human breast cancer cells with a growth promoting activity in vitro. In the present study, we measured Cath D and Epidermal Growth Factor/alpha Transforming Growth Factor (EGF/alpha-TGF) concentrations in the breast cyst fluid (BCF) of 43 patients with gross cystic disease of the breast. Both Cath D (median 2.45 pmoles mg-1 protein; range 0-4.84 vs 0.98 pmoles mg-1 protein; range 0-3.11) and EGF/alpha-TGF (28.71 ng mg-1 protein; range 7.05-50.63 vs 10.83 ng mg-1 protein; range 0.06-30.55) levels were higher in BCF of apocrine than flattened cysts (P less than 0.0005 and P less than 0.01, respectively). Premenopausal patients showed higher concentrations of Cath D (P less than 0.05) and EGF/alpha-TGF (P less than 0.05) than postmenopausal patients. A positive correlation was obtained between intracystic concentrations of Cath D and EGF/alpha-TGF (P less than 0.00001). The higher levels of Cath-D and EGF/alpha-TGF found in apocrine cysts could provide an explanation for the increased risk of subsequent breast cancer in women with this type of cyst
Results from the 2014 november 15th. multi-chord stellar occultation by the TNO (229762) 2007 UK126
Benedetti-Rossi, G. et. al.We present results derived from the first multi-chord stellar occultation by the trans-Neptunian object (229762) 2007 UK, observed on 2014 November 15. The event was observed by the Research and Education Collaborative Occultation Network project and International Occultation Timing Association collaborators throughout the United States. Use of two different data analysis methods obtain a satisfactory fit to seven chords, yielding an elliptical fit to the chords with an equatorial radius of R = 338 km and equivalent radius of R = 319 km. A circular fit also gives a radius of R = 324 km. Assuming that the object is a Maclaurin spheroid with indeterminate aspect angle, and using two published absolute magnitudes for the body, we derive possible ranges for geometric albedo between p = 0.159 and p = 0.189 , and for the body oblateness between â = 0.105 and â = 0.118 . For a nominal rotational period of 11.05 hr, an upper limit for density of Ï = 1740 kg m is estimated for the body.The RECON project would not be possible without all of the support from our community teams (teachers, students, and community members) and was funded by NSF grants AST-1212159, AST-1413287, and AST-1413072. Special thanks to Dean and Starizona for their support of RECON above and beyond the usual bounds of a commercial relationship.
Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ERC Grant Agreement n 669416 >LUCKY STAR>).
Funding from Spanish grant AYA-2014-56637-C2-1-P is acknowledged, as is the Proyecto de Excelencia de la Junta de Andaluca, J. A. 2012-FQM1776. R.D. acknowledges the support of MINECO for his Ramon y Cajal Contract. FEDER funds are also acknowledged.
A.D.O. is thankful for the support of the CAPES (BEX 9110/12-7) FAPERJ/PAPDRJ (E-26/200.464/2015) grants.
G.B.R. is thankful for the support of CAPES/Brazil and FAPERJ (Grant E-01/2015/209545).
J.I.B.C. acknowledges CNPq for a PQ2 fellowship (process number 308489/2013-6).
L.G. thanks the support from CONACYT through grant 167236.
M.A. thanks the CNPq (Grants 473002/2013-2 and 308721/2011-0) and FAPERJ (Grant E-26/111.488/2013).
P.S.-S. acknowledges that part of the research leading to these results has received funding from the European Unions Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378.
R.V.M. acknowledges the following grants: CNPq-306885/2013, CAPES/Cofecub-2506/2015, FAPERJ/PAPDRJ-45/2013, FAPERJ/CNE/05-2015.Peer Reviewe
Orbit determination of Transneptunian objects and Centaurs for the prediction of stellar occultations
The prediction of stellar occultations by Transneptunian objects and Centaurs
is a difficult challenge that requires accuracy both in the occulted star
position as for the object ephemeris. Until now, the most used method of
prediction involving tens of TNOs/Centaurs was to consider a constant offset
for the right ascension and for the declination with respect to a reference
ephemeris. This offset is determined as the difference between the most recent
observations of the TNO and the reference ephemeris. This method can be
successfully applied when the offset remains constant with time. This paper
presents an alternative method of prediction based on a new accurate orbit
determination procedure, which uses all the available positions of the TNO from
the Minor Planet Center database plus sets of new astrometric positions from
unpublished observations. The orbit determination is performed through a
numerical integration procedure (NIMA), in which we develop a specific
weighting scheme. The NIMA method was applied for 51 selected TNOs/Centaurs.
For this purpose, we have performed about 2900 new observations during
2007-2014. Using NIMA, we succeed in predicting the stellar occultations of 10
TNOs and 3 Centaurs between 2013 and 2015. By comparing the NIMA and JPL
ephemerides, we highlighted the variation of the offset between them with time.
Giving examples, we show that the constant offset method could not accurately
predict 6 out of the 13 observed positive occultations successfully predicted
by NIMA. The results indicate that NIMA is capable of efficiently refine the
orbits of these bodies. Finally, we show that the astrometric positions given
by positive occultations can help to further refine the orbit of the TNO and
consequently the future predictions. We also provide the unpublished
observations of the 51 selected TNOs and their ephemeris in a usable format by
the SPICE library.Comment: 12 pages, 9 figures, accepted in A&
Astrometry of the main satellites of Uranus: 18 years of observations
We determine accurate positions of the main satellites of Uranus: Miranda,
Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those
of these satellites, are also determined. The observational period spans from
1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil.
We used the software called Platform for Reduction of Astronomical Images
Automatically (PRAIA) to minimise (digital coronography) the influence of the
scattered light of Uranus on the astrometric measurements and to determine
accurate positions of the main satellites. The positions of Uranus were then
indirectly determined by computing the mean differences between the observed
and ephemeris positions of these satellites. A series of numerical filters was
applied to filter out spurious data. These filters are mostly based on the
comparison between the positions of Oberon with those of the other satellites
and on the offsets as given by the differences between the observed and
ephemeris positions of all satellites.
We have, for the overall offsets of the five satellites, -29 (+/-63) mas in
right ascension and -27 (+/-46) mas in declination. For the overall difference
between the offsets of Oberon and those of the other satellites, we have +3
(+/-30) mas in right ascension and -2 (+/-28) mas in declination. Ephemeris
positions for the satellites were determined from DE432+ura111. Comparisons
using other modern ephemerides for the solar system -INPOP13c- and for the
motion of the satellites -NOE-7-2013- were also made. They confirm that the
largest contribution to the offsets we find comes from the motion of the
barycenter of the Uranus system around the barycenter of the solar system, as
given by the planetary ephemerides. Catalogues with the observed positions are
provided.Comment: 13 pages, 21 figure
Multi-GeV Electron Spectrometer
The advance in laser plasma acceleration techniques pushes the regime of the
resulting accelerated particles to higher energies and intensities. In
particular the upcoming experiments with the FLAME laser at LNF will enter the
GeV regime with almost 1pC of electrons. From the current status of
understanding of the acceleration mechanism, relatively large angular and
energy spreads are expected. There is therefore the need to develop a device
capable to measure the energy of electrons over three orders of magnitude (few
MeV to few GeV) under still unknown angular divergences. Within the PlasmonX
experiment at LNF a spectrometer is being constructed to perform these
measurements. It is made of an electro-magnet and a screen made of
scintillating fibers for the measurement of the trajectories of the particles.
The large range of operation, the huge number of particles and the need to
focus the divergence present unprecedented challenges in the design and
construction of such a device. We will present the design considerations for
this spectrometer and the first results from a prototype.Comment: 7 pages, 6 figures, submitted to NIM
Astrometric positions for 18 irregular satellites of giant planets from 23 years of observations
The irregular satellites of the giant planets are believed to have been
captured during the evolution of the solar system. Knowing their physical
parameters, such as size, density, and albedo is important for constraining
where they came from and how they were captured. The best way to obtain these
parameters are observations in situ by spacecrafts or from stellar occultations
by the objects. Both techniques demand that the orbits are well known. We aimed
to obtain good astrometric positions of irregular satellites to improve their
orbits and ephemeris. We identified and reduced observations of several
irregular satellites from three databases containing more than 8000 images
obtained between 1992 and 2014 at three sites (Observat\'orio do Pico dos Dias,
Observatoire de Haute-Provence, and European Southern Observatory - La Silla).
We used the software PRAIA (Platform for Reduction of Astronomical Images
Automatically) to make the astrometric reduction of the CCD frames. The UCAC4
catalog represented the International Celestial Reference System in the
reductions. Identification of the satellites in the frames was done through
their ephemerides as determined from the SPICE/NAIF kernels. Some procedures
were followed to overcome missing or incomplete information (coordinates,
date), mostly for the older images. We managed to obtain more than 6000
positions for 18 irregular satellites: 12 of Jupiter, 4 of Saturn, 1 of Uranus
(Sycorax), and 1 of Neptune (Nereid). For some satellites the number of
obtained positions is more than 50\% of what was used in earlier orbital
numerical integrations. Comparison of our positions with recent JPL ephemeris
suggests there are systematic errors in the orbits for some of the irregular
satellites. The most evident case was an error in the inclination of Carme.Comment: 9 pages, with 3 being online materia
Very Efficient Spin Polarization Analysis (VESPA) : New Exchange Scattering-based Setup for Spin-resolved ARPES at APE-NFFA Beamline at Elettra
Complete photoemission experiments, enabling measurement of the full quantum set of the photoelectron final state, are in high demand for studying materials and nanostructures whose properties are determined by strong electron and spin correlations. Here the implementation of the new spin polarimeter VESPA (Very Efficient Spin Polarization Analysis) at the APE-NFFA beamline at Elettra is reported, which is based on the exchange coupling between the photoelectron spin and a ferromagnetic surface in a reflectometry setup. The system was designed to be integrated with a dedicated Scienta-Omicron DA30 electron energy analyzer allowing for two simultaneous reflectometry measurements, along perpendicular axes, that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the spin polarization to be performed while operating the DA30 in high-resolution mode. VESPA represents the very first installation for spin-resolved ARPES (SPARPES) at the Elettra synchrotron in Trieste, and is being heavily exploited by SPARPES users since autumn 2015
An integrated ultra-high vacuum apparatus for growth and in situ characterization of complex materials
Here we present an integrated ultra-high vacuum apparatus \u2013 named MBE-Cluster \u2013 dedicated to the growth
and in situ structural, spectroscopic and magnetic characterization of complex materials. Molecular Beam
Epitaxy (MBE) growth of metal oxides, e.g. manganites, and deposition of patterned metallic layers can be
fabricated and in situ characterized by reflection high-energy electron diffraction (RHEED), low-energy
electron diffraction (LEED) - Auger Electron Spectroscopy, X-ray photoemission spectroscopy (PES) and
azimuthal longitudinal magneto-optic Kerr effect (MOKE). The temperature can be controlled in the range
from 5 to 580 K, with the possibility of application of magnetic fields H up to \ub17 kOe and electric fields E for
voltages up to \ub1500 V. The MBE-Cluster operates for in-house research as well as user facility in combination
with the APE beamlines at Sincrotrone-Trieste and the high harmonic generator (HHG) facility for timeresolved
spectroscopy
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