979 research outputs found
An automatic deep learning approach for coronary artery calcium segmentation
Coronary artery calcium (CAC) is a significant marker of atherosclerosis and
cardiovascular events. In this work we present a system for the automatic
quantification of calcium score in ECG-triggered non-contrast enhanced cardiac
computed tomography (CT) images. The proposed system uses a supervised deep
learning algorithm, i.e. convolutional neural network (CNN) for the
segmentation and classification of candidate lesions as coronary or not,
previously extracted in the region of the heart using a cardiac atlas. We
trained our network with 45 CT volumes; 18 volumes were used to validate the
model and 56 to test it. Individual lesions were detected with a sensitivity of
91.24%, a specificity of 95.37% and a positive predicted value (PPV) of 90.5%;
comparing calcium score obtained by the system and calcium score manually
evaluated by an expert operator, a Pearson coefficient of 0.983 was obtained. A
high agreement (Cohen's k = 0.879) between manual and automatic risk prediction
was also observed. These results demonstrated that convolutional neural
networks can be effectively applied for the automatic segmentation and
classification of coronary calcifications
Sub-Doppler laser cooling of potassium atoms
We investigate sub-Doppler laser cooling of bosonic potassium isotopes, whose
small hyperfine splitting has so far prevented cooling below the Doppler
temperature. We find instead that the combination of a dark optical molasses
scheme that naturally arises in this kind of systems and an adiabatic ramping
of the laser parameters allows to reach sub-Doppler temperatures for small
laser detunings. We demonstrate temperatures as low as 25(3)microK and
47(5)microK in high-density samples of the two isotopes 39K and 41K,
respectively. Our findings will find application to other atomic systems.Comment: 7 pages, 9 figure
Continuing data analysis of the AS/E grazing incidence X-ray telescope experiment on the OSO-4 satellite
The work to correct and extend the calculation of the theoretical solar X-ray spectrum produced during earlier OSO-4 data analysis is reported along with the work to formulate models of active regions, and compare these models with the experimental values. An atlas of solar X-ray photographs is included, and solar X-ray observations are correlated with the solar wind
Ontological Levels in Histological Imaging
Paper presented at the 9th edition of the Formal Ontology in Information Systems conference, FOIS 2016, July 6–9, 2016, Annecy, FranceThis is the author accepted manuscript. The final version is available from IOS Press via the DOI in this record.In this paper we present an ontological perspective on ongoing work in histological and histopathological imaging involving the quantitative and algorithmic analysis of digitised images of cells and tissues. We present the derivation of consistent histological models from initially captured images of prepared tissue samples as a progression through a number of ontological levels, each populated by its distinctive classes of entities related in systematic ways to entities at other levels. We see this work as contributing to ongoing efforts to provide a consistent and widely accepted suite of ontological resources such as those currently constituting the OBO Foundry, and where possible we draw links between our work and existing ontologies within that suite.This research is supported by EPSRC through funding under grant EP/M023869/1 “Novel context-based segmentation algorithms for intelligent microscopy”
Making the corona and the fast solar wind: a self-consistent simulation for the low-frequency Alfven waves from photosphere to 0.3AU
We show that the coronal heating and the fast solar wind acceleration in the
coronal holes are natural consequence of the footpoint fluctuations of the
magnetic fields at the photosphere, by performing one-dimensional
magnetohydrodynamical simulation with radiative cooling and thermal conduction.
We initially set up a static open flux tube with temperature 10^4K rooted at
the photosphere. We impose transverse photospheric motions corresponding to the
granulations with velocity = 0.7km/s and period between 20 seconds and 30
minutes, which generate outgoing Alfven waves. We self-consistently treat these
waves and the plasma heating. After attenuation in the chromosphere by ~85% of
the initial energy flux, the outgoing Alfven waves enter the corona and
contribute to the heating and acceleration of the plasma mainly by the
nonlinear generation of the compressive waves and shocks. Our result clearly
shows that the initial cool and static atmosphere is naturally heated up to
10^6K and accelerated to 800km/s.Comment: 4 pages, 3 figures, ApJL, 632, L49, corrections of mistypes in
eqs.(3) & (5), Mpeg movie for fig.1 (simulation result) is available at
http://www-tap.scphys.kyoto-u.ac.jp/~stakeru/research/suzuki_200506.mp
Lapex: A Phoswich balloon experiment for hard X-ray astronomy
Satellite and balloon observations have shown that several classes of celestial objects are hard ( 15 keV) energy band with a sensitivity of approx 10 mCrab has been performed with the UCSD/MIT instrument (A4) on board the HEAO 1 satellite. About 70 X-ray sources were detected, including galactic and extragalactic objects. Hard X-ray emission has been detected in the Galaxy from X-ray pulsars. Extragalactic sources of hard X-ray emission include clusters of galaxies, QSOs, BL Lac objects, Seyfert galaxies. The essential characteristics of the Large Area Phoswich Experiment (LAPEX) for crowded sky field observations are described. It has: (1) a broad energy band of operation (20-300 keV); (2) a 3 sigma sensitivity of about 1 mCrab in 10,000 s of live observing time; and (3) imaging capabilities with an angular resolution of about 20'
Time-Dependent Ionization in Radiatively Cooling Gas
We present new computations of the equilibrium and non-equilibrium cooling
efficiencies and ionization states for low-density radiatively cooling gas
containing cosmic abundances of the elements H, He, C, N, O, Ne, Mg, Si, S, and
Fe. We present results for gas temperatures between 1e4 and 1e8 K, assuming
dust-free and optically thin conditions, and no external radiation. For
non-equilibrium cooling we solve the coupled time-dependent ionization and
energy loss equations for a radiating gas cooling from an initially hot, >5e6K
equilibrium state, down to 1e4K. We present results for heavy element
compositions ranging from 1e-3 to 2 times the elemental abundances in the Sun.
We consider gas cooling at constant density (isochoric) and at constant
pressure (isobaric). We calculate the critical column densities and
temperatures at which radiatively cooling clouds make the dynamical transition
from isobaric to isochoric evolution. We construct ion ratio diagnostics for
the temperature and metallicity in radiatively cooling gas. We provide
numerical estimates for the maximal cloud column densities for which the gas
remains optically thin to the cooling radiation. We present our computational
results in convenient on-line figures and tables (see
http://wise-obs.tau.ac.il/~orlyg/cooling/).Comment: 20 pages, 12 figures. ApJS in press. Electronic data available at
http://wise-obs.tau.ac.il/~orlyg/cooling
Temperature and Emission-Measure Profiles Along Long-Lived Solar Coronal Loops Observed with TRACE
We report an initial study of temperature and emission measure distributions
along four steady loops observed with the Transition Region and Coronal
Explorer (TRACE) at the limb of the Sun. The temperature diagnostic is the
filter ratio of the extreme-ultraviolet 171-angstrom and 195-angstrom
passbands. The emission measure diagnostic is the count rate in the
171-angstrom passband. We find essentially no temperature variation along the
loops. We compare the observed loop structure with theoretical isothermal and
nonisothermal static loop structure.Comment: 10 pages, 3 postscript figures (LaTeX, uses aaspp4.sty). Accepted by
ApJ Letter
Improving plastic management by means of people awareness
In past decades the usage of plastic has seen a tremendous increment. This raise is mainly caused by industrial development and by the spread of this material in every aspect of people life, from food package to aerospace application. For sure plastic has a key role in society and it is not possible to erase, nevertheless its overuse has a serious impact on the environment as well know. In particular, just a few percentage of the total amount of plastic is recycled, the rest has to be landfilled or burnt causing serious pollution side effect. This poor circularity in plastic value chain is mainly caused by difficulties in sorting processes and expensiveness of recycling. By the way a great part of plastic applications could be avoided without implying a reduction in life quality for the people. In addition, a better education in plastic objects shopping and plastic waste management could decrease the difficulties in sorting and recycling. One of the crucial reason why these applications and incorrect behaviour are still present is that the information on alternatives are not present or very hard to be found. In the present paper a novel platform to enhance a more plastic-free life is presented. First a detailed description of the problem is stated, then the process to achieve the proposed solution is described. Finally the platform prototype is analysed in details among its functionalities
Numerical simulations of light scattering in soft anisotropic fibrous structures and validation of a novel optical setup from fibrous media characterization
The insight of biological microstructures is at the basis of understanding the mechanical features and the potential pathologies of tissues, like the blood vessels. Different techniques are available for this purpose, like the Small Angle Light Scattering (SALS) approach. The SALS method has the advantage of being fast and non-destructive, however investigation of its physical principles is still required. Within this work, a numerical study for SALS irradiation of soft biological fibrous tissues was carried out through in-silico simulations based on a Monte Carlo approach to evaluate the effect of the thickness of the specimen. Additionally, the numerical results were validated with an optical setup based on SALS technique for the characterization of fibrous samples with dedicated tests on four 3D-printed specimens with different fibers architectures. The simulations revealed two main regions of interest according to the thickness (thk) of the analyzed media: a Fraunhofer region (thk < 0.6 mm) and a Multiple Scattering region (thk > 1 mm). Semi-quantitative information about the tissue anisotropy was successfully gathered by analyzing the scattered light spot. Moreover, the numerical results revealed a remarkable coherence with the experimental data, both in terms of mean orientation and dispersion of fibers
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