15,243 research outputs found
Local-Aggregate Modeling for Big-Data via Distributed Optimization: Applications to Neuroimaging
Technological advances have led to a proliferation of structured big data
that have matrix-valued covariates. We are specifically motivated to build
predictive models for multi-subject neuroimaging data based on each subject's
brain imaging scans. This is an ultra-high-dimensional problem that consists of
a matrix of covariates (brain locations by time points) for each subject; few
methods currently exist to fit supervised models directly to this tensor data.
We propose a novel modeling and algorithmic strategy to apply generalized
linear models (GLMs) to this massive tensor data in which one set of variables
is associated with locations. Our method begins by fitting GLMs to each
location separately, and then builds an ensemble by blending information across
locations through regularization with what we term an aggregating penalty. Our
so called, Local-Aggregate Model, can be fit in a completely distributed manner
over the locations using an Alternating Direction Method of Multipliers (ADMM)
strategy, and thus greatly reduces the computational burden. Furthermore, we
propose to select the appropriate model through a novel sequence of faster
algorithmic solutions that is similar to regularization paths. We will
demonstrate both the computational and predictive modeling advantages of our
methods via simulations and an EEG classification problem.Comment: 41 pages, 5 figures and 3 table
Linear Convergence of a Frank-Wolfe Type Algorithm over Trace-Norm Balls
We propose a rank- variant of the classical Frank-Wolfe algorithm to solve
convex optimization over a trace-norm ball. Our algorithm replaces the top
singular-vector computation (-SVD) in Frank-Wolfe with a top-
singular-vector computation (-SVD), which can be done by repeatedly applying
-SVD times. Alternatively, our algorithm can be viewed as a rank-
restricted version of projected gradient descent. We show that our algorithm
has a linear convergence rate when the objective function is smooth and
strongly convex, and the optimal solution has rank at most . This improves
the convergence rate and the total time complexity of the Frank-Wolfe method
and its variants.Comment: In NIPS 201
Neutrino mass limits from SDSS, 2dFGRS and WMAP
We investigate whether cosmological data suggest the need for massive
neutrinos. We employ galaxy power spectrum measurements from the Sloan Digital
Sky Survey (SDSS) and the Two Degree Field Galaxy Redshift Survey (2dFGRS),
along with cosmic microwave background (CMB) data from the Wilkinson Microwave
Anisotropy Probe (WMAP) and 27 other CMB experiments. We also use the
measurement of the Hubble parameter from the Hubble Space Telescope (HST) Key
Project. We find the sum of the neutrino masses to be smaller than 0.75 eV at
2\sigma (1.1 eV at 3\sigma).Comment: 4 pages, 2 figures. Only unconstrained bias fit included. References
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Angular momentum exchange between coherent light and matter fields
Full, three dimensional, time-dependent simulations are presented
demonstrating the quantized transfer of angular momentum to a Bose-Einstein
condensate from a laser carrying orbital angular momentum in a
Laguerre-Gaussian mode. The process is described in terms of coherent Bragg
scattering of atoms from a chiral optical lattice. The transfer efficiency and
the angular momentum content of the output coupled vortex state are analyzed
and compared with a recent experiment.Comment: 4 pages, 4 figure
In-vivo pan/tilt endoscope with integrated light source
Endoscopic imaging is still dominated by the paradigm of pushing long sticks into small openings. This approach has a number of limitations for minimal access surgery, such as narrow angle imaging, limited workspace, counter-intuitive motions and additional incisions for the endoscpic instruments. Our intent is to go beyond this paradigm, and remotize sensors and effectors directly into the body cavity. To this end, we have developed a prototype of a novel insertable pan/tilt endoscopic camera with an integrated light source. The package has a size of 110 mm in length and 10 mm in diameter and can be inserted into the abdomen through a standard trocar and then anchored onto the abdominal wall, leaving the incision port open for access. The camera package contains three parts: an imaging module, an illumination module, and a pan/tilt motion platform. The imaging module includes a lens and CCD imaging sensor. The illumination module attaches to the imaging module and has an array of LED light sources. The pan/tilt platform provides the imaging module with pan of 120 degrees and tilt motion of 90 degrees using small servo motors. A fixing mechanism is designed to hold the device in the cavity. A standard joy stick can be used to control the motion of the camera in a natural way. The design allows for multiple camera packages to be inserted through a single incision as well
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In-vivo pan/tilt endoscope with integrated light source
Endoscopic imaging is still dominated by the paradigm of pushing long sticks into small openings. This approach has a number of limitations for minimal access surgery, such as narrow angle imaging, limited workspace, counter-intuitive motions and additional incisions for the endoscpic instruments. Our intent is to go beyond this paradigm, and remotize sensors and effectors directly into the body cavity. To this end, we have developed a prototype of a novel insertable pan/tilt endoscopic camera with an integrated light source. The package has a size of 110 mm in length and 10 mm in diameter and can be inserted into the abdomen through a standard trocar and then anchored onto the abdominal wall, leaving the incision port open for access. The camera package contains three parts: an imaging module, an illumination module, and a pan/tilt motion platform. The imaging module includes a lens and CCD imaging sensor. The illumination module attaches to the imaging module and has an array of LED light sources. The pan/tilt platform provides the imaging module with pan of 120 degrees and tilt motion of 90 degrees using small servo motors. A fixing mechanism is designed to hold the device in the cavity. A standard joy stick can be used to control the motion of the camera in a natural way. The design allows for multiple camera packages to be inserted through a single incision as well
2-Chloro-5-nitropyridin-4-amine
The title molecule, C5H4ClN3O2, possesses mirror symmetry, with all of the atoms lying in the mirror plane. There is an intramolecular N—H⋯O hydrogen bond involving the adjacent –NO2 and –NH2 groups. A short C—H⋯O interaction is also observed. In the crystal, adjacent molecules are linked via N—H⋯Cl and N—H⋯N hydrogen bonds, forming chains propagating along [100]
CMB Anisotropy Induced by Cosmic Strings on Angular Scales
We have computed an estimate of the angular power spectrum of the Cosmic
Microwave Background (CMB) induced by cosmic strings on angular scales , using a numerical simulation of a cosmic string network; and decomposed
this pattern into scalar, vector, and tensor parts. We find no evidence for
strong acoustic oscillations in the scalar anisotropy but rather a broad peak.
The anisotropies from vector modes dominate except on very small angular scales
while the tensor anisotropies are sub-dominant on all angular scales. The
anisotropies generated after recombination are even more important than in
adiabatic models. We expect that these qualitative features are robust to the
varying of cosmological parameters, a study which has not yet been done.Comment: 4 pages, 2 figure
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EUS-guided portal pressure gradient measurement with a simple novel device: a human pilot study.
Background and aimsPortal hypertension is a serious adverse event of liver cirrhosis. Recently, we developed a simple novel technique for EUS-guided portal pressure gradient (PPG) measurement (PPGM). Our animal studies showed excellent correlation between EUS-PPGM and interventional radiology-acquired PPGM. In this video we demonstrate the results of the first human pilot study of EUS-PPGM in patients with liver disease.MethodsEUS-PPGM was performed by experienced endosonographers using a linear echoendoscope, a 25-gauge FNA needle, and a novel compact manometer. The portal vein and hepatic vein (or inferior vena cava) were targeted by use of a transgastric or transduodenal approach. Feasibility was defined as successful PPGM in each patient. Safety was based on adverse events captured in a postprocedural interview.ResultsTwenty-eight patients underwent EUS-PPGM with 100% technical success and no adverse events. PPG ranged from 1.5 to 19 mm Hg and had excellent correlation with clinical parameters of portal hypertension, including the presence of varices (P = .0002), PH gastropathy (P = .007), and thrombocytopenia (P = .036).ConclusionThis novel technique of EUS-PPGM using a 25-gauge needle and compact manometer is feasible and appears safe. Given the availability of EUS and the simplicity of the manometry setup, EUS-guided PPG may represent a promising breakthrough for procuring indispensable information in the management of patients with liver disease
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