5,098 research outputs found
Wakefields Generated by Electron Beams Passing Through a Waveguide Loaded With an Active Medium
The wakefields of a relativistic electron beam passing through a waveguide
loaded with an active medium with weak resonant dispersion have been
considered. For the calculations in this paper the parameters of the medium are
those of a solution of fullerene (C60) in a nematic liquid crystal that
exhibits activity in the X-band. It was shown that several of the TM
accelerating modes can be amplified for the geometries under consideration;
structures in which higher order modes are amplified exhibit essential
advantages as PASERs. In particular, the amplification of the highest mode
occurs in a structure loaded with a rather thick active medium layer that
maximizes the energy stored by the active medium.Comment: 7 pages, 6 figures, submitted to 2006 Advanced Accelerator Concept
Named Entity Recognition in Electronic Health Records Using Transfer Learning Bootstrapped Neural Networks
Neural networks (NNs) have become the state of the art in many machine
learning applications, especially in image and sound processing [1]. The same,
although to a lesser extent [2,3], could be said in natural language processing
(NLP) tasks, such as named entity recognition. However, the success of NNs
remains dependent on the availability of large labelled datasets, which is a
significant hurdle in many important applications. One such case are electronic
health records (EHRs), which are arguably the largest source of medical data,
most of which lies hidden in natural text [4,5]. Data access is difficult due
to data privacy concerns, and therefore annotated datasets are scarce. With
scarce data, NNs will likely not be able to extract this hidden information
with practical accuracy. In our study, we develop an approach that solves these
problems for named entity recognition, obtaining 94.6 F1 score in I2B2 2009
Medical Extraction Challenge [6], 4.3 above the architecture that won the
competition. Beyond the official I2B2 challenge, we further achieve 82.4 F1 on
extracting relationships between medical terms. To reach this state-of-the-art
accuracy, our approach applies transfer learning to leverage on datasets
annotated for other I2B2 tasks, and designs and trains embeddings that
specially benefit from such transfer.Comment: 11 pages, 4 figures, 8 table
Pot, atom and step economic (PASE) synthesis of highly functionalized piperidines: a five-component condensation
The diastereoselective pot, atom and step economic (PASE) synthesis of highly functionalized piperidines has been realized. The procedure simply involves mixing methyl acetoacetate, 2 equiv of aldehyde and 2 equiv of aniline together in the presence of InCl3. In most cases the piperidine precipitates out of solution. (c) 2007 Elsevier Ltd. All rights reserved
Antimatter interferometry for gravity measurements
We describe a light-pulse atom interferometer that is suitable for any
species of atom and even for electrons and protons as well as their
antiparticles, in particular for testing the Einstein equivalence principle
with antihydrogen. The design obviates the need for resonant lasers through
far-off resonant Bragg beam splitters and makes efficient use of scarce atoms
by magnetic confinement and atom recycling. We expect to reach an initial
accuracy of better than 1% for the acceleration of free fall of antihydrogen,
which can be improved to the part-per million level.Comment: 5 pages, 4 figures. Minor changes, accepted for PR
On the massive young stellar object AFGL4176: High-spatial-resolution multi-wavelength observations and modeling
Deeply embedded and at distances of several kiloparsecs, massive young
stellar objects (MYSOs) present numerous challenges for observation and study.
In this work, we present spatially-resolved observations of one MYSO, AFGL
4176, together with survey and literature data, ranging from interferometric
observations with VLTI/MIDI in the mid-infrared, to single-dish Herschel
measurements in the far-infrared, and sub-millimeter data from APEX. We
consider this spatially-resolved, multi-wavelength data set in terms of both
radiative transfer and geometric models. We find that the observations are well
described by one-dimensional models overall, but there are also substantial
deviations from spherical symmetry at scales of tens to hundreds of
astronomical units, which are revealed by the mid-infrared interferometric
measurements. We use a multiple-component, geometric modeling approach to
explain the mid-infrared emission on scales of tens to hundreds of astronomical
units, and find the MIDI measurements are well described by a model consisting
of a one-dimensional Gaussian halo and an inclined (\theta=60 deg)
circumstellar disk extending out to several hundred astronomical units along a
position angle of 160 deg. Finally, we compare our results both with previous
models of this source, and with those of other MYSOs, and discuss the present
situation with mid-infrared interferometric observations of massive stars.Comment: 15 pages, 14 figures. Accepted to Astronomy and Astrophysic
Detecting early signs of depressive and manic episodes in patients with bipolar disorder using the signature-based model
Recurrent major mood episodes and subsyndromal mood instability cause
substantial disability in patients with bipolar disorder. Early identification
of mood episodes enabling timely mood stabilisation is an important clinical
goal. Recent technological advances allow the prospective reporting of mood in
real time enabling more accurate, efficient data capture. The complex nature of
these data streams in combination with challenge of deriving meaning from
missing data mean pose a significant analytic challenge. The signature method
is derived from stochastic analysis and has the ability to capture important
properties of complex ordered time series data. To explore whether the onset of
episodes of mania and depression can be identified using self-reported mood
data.Comment: 12 pages, 3 tables, 10 figure
Carbon Cycle Science Data and Services at the Goddard Earth Sciences Data Information and Services Center (GES DISC)
The Goddard Earth Sciences Data Information and Services Center (GES DISC) archives and distributes a number of observational and model carbon cycle science data sets. We also provide services that facilitate data discovery, intercomparison, and visualization of these heterogeneous datasets for both research and applications users, such as subsetting, format conversion, How-To documentation, and the Help Desk
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