468 research outputs found
Energy-based temporal neural networks for imputing missing values
Imputing missing values in high dimensional time series is a difficult problem. There have been some approaches to the problem [11,8] where neural architectures were trained as probabilistic models of the data. However, we argue that this approach is not optimal. We propose to view temporal neural networks with latent variables as energy-based models and train them for missing value recovery directly. In this paper we introduce two energy-based models. The first model is based on a one dimensional convolution and the second model utilizes a recurrent neural network. We demonstrate how ideas from the energy-based learning framework can be used to train these models to recover missing values. The models are evaluated on a motion capture dataset
Revisiting loss-specific training of filter-based MRFs for image restoration
It is now well known that Markov random fields (MRFs) are particularly
effective for modeling image priors in low-level vision. Recent years have seen
the emergence of two main approaches for learning the parameters in MRFs: (1)
probabilistic learning using sampling-based algorithms and (2) loss-specific
training based on MAP estimate. After investigating existing training
approaches, it turns out that the performance of the loss-specific training has
been significantly underestimated in existing work. In this paper, we revisit
this approach and use techniques from bi-level optimization to solve it. We
show that we can get a substantial gain in the final performance by solving the
lower-level problem in the bi-level framework with high accuracy using our
newly proposed algorithm. As a result, our trained model is on par with highly
specialized image denoising algorithms and clearly outperforms
probabilistically trained MRF models. Our findings suggest that for the
loss-specific training scheme, solving the lower-level problem with higher
accuracy is beneficial. Our trained model comes along with the additional
advantage, that inference is extremely efficient. Our GPU-based implementation
takes less than 1s to produce state-of-the-art performance.Comment: 10 pages, 2 figures, appear at 35th German Conference, GCPR 2013,
Saarbr\"ucken, Germany, September 3-6, 2013. Proceeding
On parameters related to strong and weak domination in graphs
AbstractLet G be a graph. Then ÎŒ(G)â©œ|V(G)|âÎŽ(G) where ÎŒ(G) denotes the weak or independent weak domination number of G and ÎŒ(G)â©œ|V(G)|âÎ(G) where ÎŒ(G) denotes the strong or independent strong domination number of G. We give necessary and sufficient conditions for equality to hold in each case and also describe specific classes of graphs for which equality holds. Finally, we show that the problems of computing iw and ist are NP-hard, even for bipartite graphs
Intermanifold similarities in partial photoionization cross sections of helium
Using the eigenchannel R-matrix method we calculate partial photoionization
cross sections from the ground state of the helium atom for incident photon
energies up to the N=9 manifold. The wide energy range covered by our
calculations permits a thorough investigation of general patterns in the cross
sections which were first discussed by Menzel and co-workers [Phys. Rev. A {\bf
54}, 2080 (1996)]. The existence of these patterns can easily be understood in
terms of propensity rules for autoionization. As the photon energy is increased
the regular patterns are locally interrupted by perturber states until they
fade out indicating the progressive break-down of the propensity rules and the
underlying approximate quantum numbers. We demonstrate that the destructive
influence of isolated perturbers can be compensated with an energy-dependent
quantum defect.Comment: 10 pages, 10 figures, replacement with some typos correcte
Probability Density Functions to Represent Magnetic Fields at the Solar Surface
Numerical simulations of magneto-convection and analysis of solar magnetogram
data provide empirical probability density functions (PDFs) for the
line-of-sight component of the magnetic field. In this paper, we theoretically
explore effects of several types of PDFs on polarized Zeeman line formation. We
also propose composite PDFs to account for randomness in both field strength
and orientation. Such PDFs can possibly mimic random fields at the solar
surface.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
Analytical and clinical evaluation of an electrochemiluminescence immunoassay for the determination of CA 125
The CA 125 II assay on the Elecsys(R) 2010 analyzer was evaluated in an
international multicenter trial. Imprecision studies yielded within-run
CVs of 0.8-3.3% and between-day CVs of 2.4-10.9%; CVs for total
imprecision in the manufacturer's laboratory were 2.4-7.8%. The linear
range of the assay extended to at least 4500 kilounits/L (three decades).
Interference from triglycerides (10.3 mmol/L), bilirubin (850 micromol/L),
hemoglobin (1.1 mmol/L), anticoagulants (plasma), and several widely used
drugs was undetectable. Method comparisons with five other CA 125 II
assays showed good correlation but differences in standardization. A 95th
percentile cutoff value of 35 kilounits/L was calculated from values
measured in 593 apparently healthy (pre- and postmenopausal) women. In 95%
of patients with benign gynecological diseases CA 125 was </=190
kilounits/L; 63% of patients with newly diagnosed ovarian carcinoma had
values >190 kilounits/L. A comparison of CA 125 values obtained with the
Elecsys test and with other common CA 125 tests in monitored patients
being treated for ovarian cancer showed identical patterns. In conclusion,
the Elecsys CA 125 II assay is linear over a broad range, yields precise
and accurate results, is free from interferences, and compares well with
other assays
Atomic Force Microscopy of height fluctuations of fibroblast cells
We investigated the nanometer scale height fluctuations of 3T3 fibroblast
cells with the atomic force microscope (AFM) under physiological conditions.
Correlation between these fluctuations and lateral cellular motility can be
observed. Fluctuations measured on leading edges appear to be predominantly
related to actin polymerization-depolymerization processes. We found fast (5
Hz) pulsatory behavior with 1--2 nm amplitude on a cell with low motility
showing emphasized structure of stress fibres. Myosin driven contractions of
stress fibres are thought to induce this pulsation.Comment: 6 pages, 5 figures, 1 tabl
FACT -- the First Cherenkov Telescope using a G-APD Camera for TeV Gamma-ray Astronomy (HEAD 2010)
Geiger-mode Avalanche Photodiodes (G-APD) bear the potential to significantly
improve the sensitivity of Imaging Air Cherenkov Telescopes (IACT). We are
currently building the First G-APD Cherenkov Telescope (FACT) by refurbishing
an old IACT with a mirror area of 9.5 square meters and construct a new, fine
pixelized camera using novel G-APDs. The main goal is to evaluate the
performance of a complete system by observing very high energy gamma-rays from
the Crab Nebula. This is an important field test to check the feasibility of
G-APD-based cameras to replace at some time the PMT-based cameras of planned
future IACTs like AGIS and CTA. In this article, we present the basic design of
such a camera as well as some important details to be taken into account.Comment: Poster shown at HEAD 2010, Big Island, Hawaii, March 1-4, 201
Resonance structure in the Li^- photodetachment cross section
We report on the first observation of resonance structure in the total cross
section for the photodetachment of Li^-. The structure arises from the
autodetaching decay of doubly excited ^1P states of Li^- that are bound with
respect to the 3p state of the Li atom. Calculations have been performed for
both Li^- and H^- to assist in the identification of these resonances. The
lowest lying resonance is a symmetrically excited intrashell resonance. Higher
lying asymmetrically excited intershell states are observed which converge on
the Li(3p) limit.Comment: 4 pages, 2 figure, 19 references, RevTeX, figures in ep
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