457 research outputs found
Contextual-based Image Inpainting: Infer, Match, and Translate
We study the task of image inpainting, which is to fill in the missing region
of an incomplete image with plausible contents. To this end, we propose a
learning-based approach to generate visually coherent completion given a
high-resolution image with missing components. In order to overcome the
difficulty to directly learn the distribution of high-dimensional image data,
we divide the task into inference and translation as two separate steps and
model each step with a deep neural network. We also use simple heuristics to
guide the propagation of local textures from the boundary to the hole. We show
that, by using such techniques, inpainting reduces to the problem of learning
two image-feature translation functions in much smaller space and hence easier
to train. We evaluate our method on several public datasets and show that we
generate results of better visual quality than previous state-of-the-art
methods.Comment: ECCV 2018 camera read
Studies of multiple stellar systems - IV. The triple-lined spectroscopic system Gliese 644
We present a radial-velocity study of the triple-lined system Gliese 644 and
derive spectroscopic elements for the inner and outer orbits with periods of
2.9655 and 627 days. We also utilize old visual data, as well as modern speckle
and adaptive optics observations, to derive a new astrometric solution for the
outer orbit. These two orbits together allow us to derive masses for each of
the three components in the system: M_A = 0.410 +/- 0.028 (6.9%), M_Ba = 0.336
+/- 0.016 (4.7%), and $M_Bb = 0.304 +/- 0.014 (4.7%) M_solar. We suggest that
the relative inclination of the two orbits is very small. Our individual masses
and spectroscopic light ratios for the three M stars in the Gliese 644 system
provide three points for the mass-luminosity relation near the bottom of the
Main Sequence, where the relation is poorly determined. These three points
agree well with theoretical models for solar metallicity and an age of 5 Gyr.
Our radial velocities for Gliese 643 and vB 8, two common-proper-motion
companions of Gliese 644, support the interpretation that all five M stars are
moving together in a physically bound group. We discuss possible scenarios for
the formation and evolution of this configuration, such as the formation of all
five stars in a sequence of fragmentation events leading directly to the
hierarchical configuration now observed, versus formation in a small N cluster
with subsequent dynamical evolution into the present hierarchical
configuration.Comment: 17 pages, 9 figures, Accepted for publication in MNRA
In Brain Multi-Photon Imaging of Vaterite Drug Delivery Cargoes loaded with Carbon Dots
Biocompatible fluorescent agents, such as phenylenediamine carbon dots (CDs),
are key contributors to the theragnostic paradigm, enabling real-time in vivo
imaging of drug delivery cargoes. This study explores the optical properties of
these CDs, demonstrating their potential for two-photon fluorescence imaging in
brain vessels. Using an open aperture z-scan technique, we measured the
wavelength-dependent nonlinear absorption cross-section of the CDs, achieving a
peak value near 50 GM. This suggests the potential use of phenylenediamine CDs
for efficient multiphoton excitation in the 775 - 895 nm spectral range.
Mesoporous vaterite nanoparticles were loaded with fluorescent CDs to examine
the possibility of a simultaneous imaging and drug delivery platform. Efficient
one and two-photon imaging of the CD-vaterite composites, uptaken by macrophage
and genetically engineered C6-Glioma cells, was demonstrated. For an in vivo
scenario, vaterite nanoparticles loaded with CDs were directly injected into
the brain of a living mouse, and their flow was monitored in real-time within
the blood vessels. The facile synthesis of phenylenediamine carbon dots, their
significant nonlinear responses, and biological compatibility show a viable
route for implementing drug tracking and sensing platforms in living systems
Necessary and sufficient conditions of solution uniqueness in minimization
This paper shows that the solutions to various convex minimization
problems are \emph{unique} if and only if a common set of conditions are
satisfied. This result applies broadly to the basis pursuit model, basis
pursuit denoising model, Lasso model, as well as other models that
either minimize or impose the constraint , where
is a strictly convex function. For these models, this paper proves that,
given a solution and defining I=\supp(x^*) and s=\sign(x^*_I),
is the unique solution if and only if has full column rank and there
exists such that and for . This
condition is previously known to be sufficient for the basis pursuit model to
have a unique solution supported on . Indeed, it is also necessary, and
applies to a variety of other models. The paper also discusses ways to
recognize unique solutions and verify the uniqueness conditions numerically.Comment: 6 pages; revised version; submitte
Fully Automatic Expression-Invariant Face Correspondence
We consider the problem of computing accurate point-to-point correspondences
among a set of human face scans with varying expressions. Our fully automatic
approach does not require any manually placed markers on the scan. Instead, the
approach learns the locations of a set of landmarks present in a database and
uses this knowledge to automatically predict the locations of these landmarks
on a newly available scan. The predicted landmarks are then used to compute
point-to-point correspondences between a template model and the newly available
scan. To accurately fit the expression of the template to the expression of the
scan, we use as template a blendshape model. Our algorithm was tested on a
database of human faces of different ethnic groups with strongly varying
expressions. Experimental results show that the obtained point-to-point
correspondence is both highly accurate and consistent for most of the tested 3D
face models
Weak pairwise correlations imply strongly correlated network states in a neural population
Biological networks have so many possible states that exhaustive sampling is
impossible. Successful analysis thus depends on simplifying hypotheses, but
experiments on many systems hint that complicated, higher order interactions
among large groups of elements play an important role. In the vertebrate
retina, we show that weak correlations between pairs of neurons coexist with
strongly collective behavior in the responses of ten or more neurons.
Surprisingly, we find that this collective behavior is described quantitatively
by models that capture the observed pairwise correlations but assume no higher
order interactions. These maximum entropy models are equivalent to Ising
models, and predict that larger networks are completely dominated by
correlation effects. This suggests that the neural code has associative or
error-correcting properties, and we provide preliminary evidence for such
behavior. As a first test for the generality of these ideas, we show that
similar results are obtained from networks of cultured cortical neurons.Comment: Full account of work presented at the conference on Computational and
Systems Neuroscience (COSYNE), 17-20 March 2005, in Salt Lake City, Utah
(http://cosyne.org
Stimulus-dependent maximum entropy models of neural population codes
Neural populations encode information about their stimulus in a collective
fashion, by joint activity patterns of spiking and silence. A full account of
this mapping from stimulus to neural activity is given by the conditional
probability distribution over neural codewords given the sensory input. To be
able to infer a model for this distribution from large-scale neural recordings,
we introduce a stimulus-dependent maximum entropy (SDME) model---a minimal
extension of the canonical linear-nonlinear model of a single neuron, to a
pairwise-coupled neural population. The model is able to capture the
single-cell response properties as well as the correlations in neural spiking
due to shared stimulus and due to effective neuron-to-neuron connections. Here
we show that in a population of 100 retinal ganglion cells in the salamander
retina responding to temporal white-noise stimuli, dependencies between cells
play an important encoding role. As a result, the SDME model gives a more
accurate account of single cell responses and in particular outperforms
uncoupled models in reproducing the distributions of codewords emitted in
response to a stimulus. We show how the SDME model, in conjunction with static
maximum entropy models of population vocabulary, can be used to estimate
information-theoretic quantities like surprise and information transmission in
a neural population.Comment: 11 pages, 7 figure
End-to-end Interpretable Learning of Non-blind Image Deblurring
Non-blind image deblurring is typically formulated as a linear least-squares
problem regularized by natural priors on the corresponding sharp picture's
gradients, which can be solved, for example, using a half-quadratic splitting
method with Richardson fixed-point iterations for its least-squares updates and
a proximal operator for the auxiliary variable updates. We propose to
precondition the Richardson solver using approximate inverse filters of the
(known) blur and natural image prior kernels. Using convolutions instead of a
generic linear preconditioner allows extremely efficient parameter sharing
across the image, and leads to significant gains in accuracy and/or speed
compared to classical FFT and conjugate-gradient methods. More importantly, the
proposed architecture is easily adapted to learning both the preconditioner and
the proximal operator using CNN embeddings. This yields a simple and efficient
algorithm for non-blind image deblurring which is fully interpretable, can be
learned end to end, and whose accuracy matches or exceeds the state of the art,
quite significantly, in the non-uniform case.Comment: Accepted at ECCV2020 (poster
Frame Theory for Signal Processing in Psychoacoustics
This review chapter aims to strengthen the link between frame theory and
signal processing tasks in psychoacoustics. On the one side, the basic concepts
of frame theory are presented and some proofs are provided to explain those
concepts in some detail. The goal is to reveal to hearing scientists how this
mathematical theory could be relevant for their research. In particular, we
focus on frame theory in a filter bank approach, which is probably the most
relevant view-point for audio signal processing. On the other side, basic
psychoacoustic concepts are presented to stimulate mathematicians to apply
their knowledge in this field
H-Ras Nanocluster Stability Regulates the Magnitude of MAPK Signal Output
H-Ras is a binary switch that is activated by multiple co-factors and triggers several key cellular pathways one of which is MAPK. The specificity and magnitude of downstream activation is achieved by the spatio-temporal organization of the active H-Ras in the plasma membrane. Upon activation, the GTP bound H-Ras binds to Galectin-1 (Gal-1) and becomes transiently immobilized in short-lived nanoclusters on the plasma membrane from which the signal is propagated to Raf. In the current study we show that stabilizing the H-Ras-Gal-1 interaction, using bimolecular fluorescence complementation (BiFC), leads to prolonged immobilization of H-Ras.GTP in the plasma membrane which was measured by fluorescence recovery after photobleaching (FRAP), and increased signal out-put to the MAPK module. EM measurements of Raf recruitment to the H-Ras.GTP nanoclusters demonstrated that the enhanced signaling observed in the BiFC stabilized H-Ras.GTP nanocluster was attributed to increased H-Ras immobilization rather than to an increase in Raf recruitment. Taken together these data demonstrate that the magnitude of the signal output from a GTP-bound H-Ras nanocluster is proportional to its stability
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