3,560 research outputs found
Provable Self-Representation Based Outlier Detection in a Union of Subspaces
Many computer vision tasks involve processing large amounts of data
contaminated by outliers, which need to be detected and rejected. While outlier
detection methods based on robust statistics have existed for decades, only
recently have methods based on sparse and low-rank representation been
developed along with guarantees of correct outlier detection when the inliers
lie in one or more low-dimensional subspaces. This paper proposes a new outlier
detection method that combines tools from sparse representation with random
walks on a graph. By exploiting the property that data points can be expressed
as sparse linear combinations of each other, we obtain an asymmetric affinity
matrix among data points, which we use to construct a weighted directed graph.
By defining a suitable Markov Chain from this graph, we establish a connection
between inliers/outliers and essential/inessential states of the Markov chain,
which allows us to detect outliers by using random walks. We provide a
theoretical analysis that justifies the correctness of our method under
geometric and connectivity assumptions. Experimental results on image databases
demonstrate its superiority with respect to state-of-the-art sparse and
low-rank outlier detection methods.Comment: 16 pages. CVPR 2017 spotlight oral presentatio
Superfluidity of Interacting Bosonic Mixtures in Optical Lattices
We report the observation of many-body interaction effects for a homonuclear
bosonic mixture in a three-dimensional optical lattice with variable state
dependence along one axis. Near the superfluid-to-Mott insulator transition for
one component, we find that the presence of a second component can reduce the
apparent superfluid coherence, most significantly when it either experiences a
strongly localizing lattice potential or none at all. We examine this effect by
varying the relative populations and lattice depths, and discuss the observed
behavior in view of recent proposals for scattering from impurities and of
atom-phonon coupling for atoms immersed in a superfluid.Comment: 4 pages, 3 figure
The Suborbital Particle Aggregation and Collision Experiment (SPACE): Studying the Collision Behavior of Submillimeter-Sized Dust Aggregates on the Suborbital Rocket Flight REXUS 12
The Suborbital Particle Aggregation and Collision Experiment (SPACE) is a
novel approach to study the collision properties of submillimeter-sized, highly
porous dust aggregates. The experiment was designed, built and carried out to
increase our knowledge about the processes dominating the first phase of planet
formation. During this phase, the growth of planetary precursors occurs by
agglomeration of micrometer-sized dust grains into aggregates of at least
millimeters to centimeters in size. However, the formation of larger bodies
from the so-formed building blocks is not yet fully understood. Recent
numerical models on dust growth lack a particular support by experimental
studies in the size range of submillimeters, because these particles are
predicted to collide at very gentle relative velocities of below 1 cm/s that
can only be achieved in a reduced-gravity environment.
The SPACE experiment investigates the collision behavior of an ensemble of
silicate-dust aggregates inside several evacuated glass containers which are
being agitated by a shaker to induce the desired collisions at chosen
velocities. The dust aggregates are being observed by a high-speed camera,
allowing for the determination of the collision properties of the
protoplanetary dust analog material. The data obtained from the suborbital
flight with the REXUS (Rocket Experiments for University Students) 12 rocket
will be directly implemented into a state-of-the-art dust growth and collision
model
PISCO2: the new speckle camera of the Nice 76-cm refractor
We present the new speckle camera PISCO2 made in 2010-2012, for the 76-cm
refractor of C\^ote d'Azur Observatory. It is a focal instrument dedicated to
the observation of visual binary stars using high angular resolution speckle
interferometry techniques to partly overcome the degradation caused by the
atmospheric turbulence. Fitted with an EMCCD detector, PISCO2 allows the
acquisition of short exposure images that are processed in real time by our
specially designed software. Two Risley prisms are used for correcting the
atmospheric dispersion. All optical settings are remotely controlled. We have
already been able to observe faint, close binary stars with angular separations
as small as 0".16, and visual magnitudes of about 16. We also have measured
some particularly difficult systems with a magnitude difference between the two
components of about 4 magnitudes. This level of performance is very promising
for the detection and study of large sets of yet unknown (or partly measured)
binaries with close separation and/or large magnitude difference.Comment: 13 pages, 12 figure
The origin of asymmetry : early polarisation of the Drosophila germline cyst and oocyte.
The anterior-posterior axis of Drosophila is established before fertilisation when the oocyte becomes polarised to direct the localisation of bicoid and oskarmRNAs to opposite poles of the egg. Here we review recent results that reveal that the oocyte acquires polarity much earlier than previously thought, at the time when it acquires its fate. The oocyte arises from a 16 cell germline cyst, and its selection and the initial cue for its polarisation are controlled by the asymmetric segregation of a germline specific organelle called the fusome. Several different downstream pathways then interpret this asymmetry to restrict distinct aspects of oocyte identity to this cell. Mutations in any of the 6 conserved PAR proteins disrupt the early polarisation of the oocyte and lead to a failure to maintain its identity. Surprisingly, mutations affecting the control of the mitotic or meiotic cell cycle also lead to a failure to maintain the oocyte fate, indicating crosstalk between the nuclear and cytoplasmic events of oocyte differentiation. The early polarity of the oocyte initiates a series of reciprocal signalling events between the oocyte and the somatic follicle cells that lead to a reversal of oocyte polarity later in oogenesis, which defines the anterior-posterior axis of the embryo
Le réseau des mesures de Météo-France en Franche-Comté
Au cours des tout derniers jours de décembre 1999, deux dépressions très creuses ont balayé la France d'ouest en est. Les tempêtes ont frappé la Franche-Comté de plein fouet. Des vents à plus de 150 km/h (le maximum fut de 151 km/h à Métabief dans le Doubs) ont été mesurés par endroit‑! Il est probable qu'une telle puissance n'avait jamais été atteinte sous nos contrées dites " tempérées ". Les dégâts ont été considérables : toits arrachés sur tout le territoire, lignes électriques et téléphoniques coupées, forêts dévastées (on parle de plus de 2 millions de m3 de bois abattus)
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