15,437 research outputs found
3D high definition video coding on a GPU-based heterogeneous system
H.264/MVC is a standard for supporting the sensation of 3D, based on coding from 2 (stereo) to N views. H.264/MVC adopts many coding options inherited from single view H.264/AVC, and thus its complexity is even higher, mainly because the number of processing views is higher. In this manuscript, we aim at an efficient parallelization of the most computationally intensive video encoding module for stereo sequences. In particular, inter prediction and its collaborative execution on a heterogeneous platform. The proposal is based on an efficient dynamic load balancing algorithm and on breaking encoding dependencies. Experimental results demonstrate the proposed algorithm's ability to reduce the encoding time for different stereo high definition sequences. Speed-up values of up to 90× were obtained when compared with the reference encoder on the same platform. Moreover, the proposed algorithm also provides a more energy-efficient approach and hence requires less energy than the sequential reference algorith
A data relocation approach for terrain surface analysis on multi-GPU systems: a case study on the total viewshed problem
Digital Elevation Models (DEMs) are important datasets for modelling the line
of sight, such as radio signals, sound waves and human vision. These are
commonly analyzed using rotational sweep algorithms. However, such algorithms
require large numbers of memory accesses to 2D arrays which, despite being
regular, result in poor data locality in memory. Here, we propose a new
methodology called skewed Digital Elevation Model (sDEM), which substantially
improves the locality of memory accesses and increases the inherent parallelism
involved in the computation of rotational sweep-based algorithms. In
particular, sDEM applies a data restructuring technique before accessing the
memory and performing the computation. To demonstrate the high efficiency of
sDEM, we use the problem of total viewshed computation as a case study
considering different implementations for single-core, multi-core, single-GPU
and multi-GPU platforms. We conducted two experiments to compare sDEM with (i)
the most commonly used geographic information systems (GIS) software and (ii)
the state-of-the-art algorithm. In the first experiment, sDEM is on average
8.8x faster than current GIS software despite being able to consider only few
points because of their limitations. In the second experiment, sDEM is 827.3x
faster than the state-of-the-art algorithm in the best case
CHK1 expression in gastric cancer is modulated by p53 and RB1/E2F1: Implications in chemo/radiotherapy response
Radiation has a limited but relevant role in the adjuvant therapy of gastric cancer (GC) patients. Since Chk1 plays a critical function in cellular response to genotoxic agents, we aimed to analyze the role of Chk1 in GC as a biomarker for radiotherapy resistance. We analyzed Chk1 expression in AGS and MKN45 human GC cell lines by RT-QPCR and WB and in a small cohort of human patient’s samples. We demonstrated that Chk1 overexpression specifically increases resistance to radiation in GC cells. Accordingly, abrogation of Chk1 activity with UCN-01 and its expression with shChk1 increased sensitivity to bleomycin and radiation. Furthermore, when we assessed Chk1 expression in human samples, we found a correlation between nuclear Chk1 accumulation and a decrease in progression free survival. Moreover, using a luciferase assay we found that Chk1’s expression is controlled by p53 and RB/E2F1 at the transcriptional level. Additionally, we present preliminary data suggesting a posttranscriptional regulation mechanism, involving miR-195 and miR-503, which are inversely correlated with expression of Chk1 in radioresistant cells. In conclusion, Chk1/microRNA axis is involved in resistance to radiation in GC, and suggests Chk1 as a potential tool for optimal stratification of patients susceptible to receive adjuvant radiotherapy after surgeryThis work was supported by Instituto de Salud Carlos III–Fondo de Investigación Sanitaria (PS09/1988 to ISP; PI11-00949, pI014-1495 and Feder Funds to RP); Comunidad Autónoma de Madrid-Universidad Autónoma de Madrid (CCG10-UAM/BIO-5871 to ISP); Fundación Leticia Castillejo Castillo and Ministerio de Ciencia e Innovación (SAF2012-30862 to RSP), Spain
An XMM-Newton and INTEGRAL view on the hard state of EXO 1745-248 during its 2015 outburst
CONTEXT - Transient low-mass X-ray binaries (LMXBs) often show outbursts
lasting typically a few-weeks and characterized by a high X-ray luminosity
( erg/sec), while for most of the time they are
found in X-ray quiescence ( erg/sec). EXO 1745-248
is one of them. AIMS - The broad-band coverage, and the sensitivity of
instrument on board of {\xmm} and {\igr}, offers the opportunity to
characterize the hard X-ray spectrum during {\exo} outburst. METHODS - In this
paper we report on quasi-simultaneous {\xmm} and {\igr} observations of the
X-ray transient {\exo} located in the globular cluster Terzan 5, performed ten
days after the beginning of the outburst (on 2015 March 16th) shown by the
source between March and June 2015. The source was caught in a hard state,
emitting a 0.8-100 keV luminosity of ~{\lumcgs}. RESULTS - The
spectral continuum was dominated by thermal Comptonization of seed photons with
temperature keV, by a cloud with moderate optical depth
and electron temperature keV. A weaker soft
thermal component at temperature --0.7 keV and compatible
with a fraction of the neutron star radius was also detected. A rich emission
line spectrum was observed by the EPIC-pn on-board {\xmm}; features at energies
compatible with K- transitions of ionized sulfur, argon, calcium and
iron were detected, with a broadness compatible with either thermal Compton
broadening or Doppler broadening in the inner parts of an accretion disk
truncated at gravitational radii from the neutron star. Strikingly, at
least one narrow emission line ascribed to neutral or mildly ionized iron is
needed to model the prominent emission complex detected between 5.5 and 7.5
keV. (Abridged)Comment: 14 pages, 6 figure, 2 tables. Accepted for publication on A&A
(21/03/2017
Resolving galaxies in time and space: II: Uncertainties in the spectral synthesis of datacubes
In a companion paper we have presented many products derived from the
application of the spectral synthesis code STARLIGHT to datacubes from the
CALIFA survey, including 2D maps of stellar population properties and 1D
averages in the temporal and spatial dimensions. Here we evaluate the
uncertainties in these products. Uncertainties due to noise and spectral shape
calibration errors and to the synthesis method are investigated by means of a
suite of simulations based on 1638 CALIFA spectra for NGC 2916, with
perturbations amplitudes gauged in terms of the expected errors. A separate
study was conducted to assess uncertainties related to the choice of
evolutionary synthesis models. We compare results obtained with the Bruzual &
Charlot models, a preliminary update of them, and a combination of spectra
derived from the Granada and MILES models. About 100k CALIFA spectra are used
in this comparison.
Noise and shape-related errors at the level expected for CALIFA propagate to
0.10-0.15 dex uncertainties in stellar masses, mean ages and metallicities.
Uncertainties in A_V increase from 0.06 mag in the case of random noise to 0.16
mag for shape errors. Higher order products such as SFHs are more uncertain,
but still relatively stable. Due to the large number statistics of datacubes,
spatial averaging reduces uncertainties while preserving information on the
history and structure of stellar populations. Radial profiles of global
properties, as well as SFHs averaged over different regions are much more
stable than for individual spaxels. Uncertainties related to the choice of base
models are larger than those associated with data and method. Differences in
mean age, mass and metallicity are ~ 0.15 to 0.25 dex, and 0.1 mag in A_V.
Spectral residuals are ~ 1% on average, but with systematic features of up to
4%. The origin of these features is discussed. (Abridged)Comment: A&A, accepte
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