1,838 research outputs found
Fully automated segmentation and tracking of the intima media thickness in ultrasound video sequences of the common carotid artery
Abstract—The robust identification and measurement of the intima media thickness (IMT) has a high clinical relevance because it represents one of the most precise predictors used in the assessment of potential future cardiovascular events. To facilitate the analysis of arterial wall thickening in serial clinical investigations, in this paper we have developed a novel fully automatic algorithm for the segmentation, measurement, and tracking of the intima media complex (IMC) in B-mode ultrasound video sequences. The proposed algorithm entails a two-stage image analysis process that initially addresses the segmentation of the IMC in the first frame of the ultrasound video sequence using a model-based approach; in the second step, a novel customized tracking procedure is applied to robustly detect the IMC in the subsequent frames. For the video tracking procedure, we introduce a spatially coherent algorithm called adaptive normalized correlation that prevents the tracking process from converging to wrong arterial interfaces. This represents the main contribution of this paper and was developed to deal with inconsistencies in the appearance of the IMC over the cardiac cycle. The quantitative evaluation has been carried out on 40 ultrasound video sequences of the common carotid artery (CCA) by comparing the results returned by the developed algorithm with respect to ground truth data that has been manually annotated by clinical experts. The measured IMTmean ± standard deviation recorded by the proposed algorithm is 0.60 mm ± 0.10, with a mean coefficient of variation (CV) of 2.05%, whereas the corresponding result obtained for the manually annotated ground truth data is 0.60 mm ± 0.11 with a mean CV equal to 5.60%. The numerical results reported in this paper indicate that the proposed algorithm is able to correctly segment and track the IMC in ultrasound CCA video sequences, and we were encouraged by the stability of our technique when applied to data captured under different imaging conditions. Future clinical studies will focus on the evaluation of patients that are affected by advanced cardiovascular conditions such as focal thickening and arterial plaques
XMM-Newton study of 30 Dor C and a newly identified MCSNR J0536-6913 in the Large Magellanic Cloud
Aims: We present a study of the superbubble (SB) 30 Dor C and the newly
identified MCSNR J0536-6913 in the LMC. Methods: All available XMM-Newton data
(exposure times of 420 ks EPIC-pn, 556 ks EPIC-MOS1, 614 ks EPIC-MOS2) were
used to characterise the thermal X-ray emission in the region. An analysis of
the non-thermal X-rays is also presented and discussed in the context of
emission mechanisms previously suggested in the literature. These data are
supplemented by X-ray data from Chandra, optical data from the MCELS, and radio
data from ATCA and MOST. Results: The brightest thermal emission was found to
be associated with a new supernova remnant, MCSNR J0536-6913. X-ray spectral
analysis of MCSNR J0536-6913 suggested an ejecta-dominated remnant with lines
of O, Ne, Mg, and Si, and a total 0.3-10 keV luminosity of ~8E+34 erg/s. Based
on derived ejecta abundance ratios, we determined the mass of the stellar
progenitor to be either ~18 M_sun or as high as >40 M_sun, though the spectral
fits were subject to assumptions (e.g., uniform temperature and well-mixed
ejecta). The thermal emission from the SB exhibited enrichment by alpha-process
elements, evidence for a recent core-collapse SNR interaction with the SB
shell. We detected non-thermal X-ray emission throughout 30 Dor C, with the
brightest regions being highly correlated with the H-alpha and radio shells. We
created a non-thermal spectral energy distribution for the north-eastern shell
of 30 Dor C which was best-fit with an exponentially cut-off synchrotron model.
Conclusions: Thermal X-ray emission from 30 Dor C is very complex, consisting
of a large scale SB emission at the eastern shell wall with the brightest
emission due to MCSNR J0536-6913. The fact that the non-thermal spectral energy
distribution of the SB shell was observed to roll-off is further evidence that
the non-thermal X-rays from 30 Dor C are synchrotron in origin.Comment: 22 pages, 21 figures, accepted for publication in Astronomy and
Astrophysic
XMM-Newton observation of SNR J0533-7202 in the Large Magellanic Cloud
Aims. We present an X-ray study of the supernova remnant SNR J0533-7202 in
the Large Magellanic Cloud (LMC) and determine its physical characteristics
based on its X-ray emission. Methods. We observed SNR J0533-7202 with
XMM-Newton (flare-filtered exposure times of 18 ks EPIC-pn and 31 ks
EPIC-MOS1/MOS2). We produced X-ray images of the SNR, performed an X-ray
spectral analysis, and compared the results to multi-wavelength studies.
Results. The distribution of X-ray emission is highly non-uniform, with the
south-west region brighter than the north-east. The X-ray emission is
correlated with the radio emission from the remnant. We determine that this
morphology is likely due to the SNR expanding into a non-uniform ambient medium
and not an absorption effect. We estimate the size to be 53.9 (\pm 3.4) x 43.6
(\pm 3.4) pc, with the major axis rotated ~64 degrees east of north. We find no
spectral signatures of ejecta and infer that the X-ray plasma is dominated by
swept-up interstellar medium. Using the spectral fit results and the Sedov
self-similar solution, we estimate an age of ~17-27 kyr, with an initial
explosion energy of (0.09-0.83) x 10^51 erg. We detected an X-ray source
located near the centre of the remnant, namely XMMU J053348.2-720233. The
source type could not be conclusively determined due to the lack of a
multi-wavelength counterpart and low X-ray counts. We find that it is likely
either a background active galactic nucleus or a low-mass X-ray binary in the
LMC. Conclusions. We detected bright thermal X-ray emission from SNR J0533-7202
and determined that the remnant is in the Sedov phase of its evolution. The
lack of ejecta emission prohibits us from typing the remnant with the X-ray
data. Therefore, the likely Type Ia classification based on the local stellar
population and star formation history reported in the literature cannot be
improved upon.Comment: 7 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
Deep XMM-Newton observations of the northern disc of M31. I. Source catalogue
We carried out new observations of two fields in the northern ring of M31
with XMM-Newton with two exposures of 100 ks each and obtained a complete list
of X-ray sources down to a sensitivity limit of ~7 x 10^34 erg s^-1 (0.5 - 2.0
keV). The major objective of the observing programme was the study of the hot
phase of the ISM in M31. The analysis of the diffuse emission and the study of
the ISM is presented in a separate paper. We analysed the spectral properties
of all detected sources using hardness ratios and spectra if the statistics
were high enough. We also checked for variability. We cross-correlated the
source list with the source catalogue of a new survey of the northern disc of
M31 carried out with Chandra and Hubble (Panchromatic Hubble Andromeda
Treasury, PHAT) as well as with other existing catalogues. We detected a total
of 389 sources, including 43 foreground stars and candidates and 50 background
sources. Based on the comparison to the Chandra/PHAT survey, we classify 24
hard X-ray sources as new candidates for X-ray binaries (XRBs). In total, we
identified 34 XRBs and candidates and 18 supernova remnants (SNRs) and
candidates. Three of the four brightest SNRs show emission mainly below 2 keV,
consistent with shocked ISM. The spectra of two of them also require an
additional component with a higher temperature. The SNR [SPH11] 1535 has a
harder spectrum and might suggest that there is a pulsar-wind nebula inside the
SNR. We find five new sources showing clear time variability. We also studied
the spectral properties of the transient source SWIFT J004420.1+413702, which
shows significant variation in flux over a period of seven months (June 2015 to
January 2016) and associated change in absorption. Based on the likely optical
counterpart detected in the Chandra/PHAT survey, the source is classified as a
low-mass X-ray binary.Comment: Accepted for publication in A&
Low-lying continuum structures in B8 and Li8 in a microscopic model
We search for low-lying resonances in the B8 and Li8 nuclei using a
microscopic cluster model and a variational scattering method, which is
analytically continued to complex energies. After fine-tuning the
nucleon-nucleon interaction to get the known 1+ state of B8 at the right
energy, we reproduce the known spectra of the studied nuclei. In addition, our
model predicts a 1+ state at 1.3 MeV in B8, relative to the Be7+p threshold,
whose corresponding pair is situated right at the Li7+n threshold in Li8.
Lacking any experimental evidence for the existence of such states, it is
presently uncertain whether these structures really exist or they are spurious
resonances in our model. We demonstrate that the predicted state in B8, if it
exists, would have important consequences for the understanding of the
astrophysically important Be7(p,gamma)B8 reaction.Comment: 6 pages with 1 figure. The postscript file and more information are
available at http://nova.elte.hu/~csot
The Impact of Thermal Degradation on Properties of Electrical Machine Winding Insulation Material
Inter-turn stator short circuits can develop quickly leading to serious damage of an electric machine. However, degradation mechanisms of winding insulation material are not yet fully understood. Therefore, the main contribution of this article is analysis of the impact of thermal ageing on the electrical properties of the thin film winding insulation. The insulation samples have been aged thermally at 200–275 °C and for 100–1600 hours. After ageing, impedance spectroscopy measurements were undertaken on the samples and equivalent circuit model (ECM) parameters fitted for each measurement. This allows the impact of thermal ageing on ECM parameters to be analysed, giving insight into the changes of the electrical properties of the insulation. Finally, high voltage was applied to the samples aiming to identify the breakdown voltage characteristics of the insulation material
The population of X-ray supernova remnants in the Large Magellanic Cloud
We present a comprehensive X-ray study of the population of supernova
remnants (SNRs) in the LMC. Using primarily XMM-Newton, we conduct a systematic
spectral analysis of LMC SNRs to gain new insights on their evolution and the
interplay with their host galaxy. We combined all the archival XMM observations
of the LMC with those of our Very Large Programme survey. We produced X-ray
images and spectra of 51 SNRs, out of a list of 59. Using a careful modelling
of the background, we consistently analysed all the X-ray spectra and measure
temperatures, luminosities, and chemical compositions. We investigated the
spatial distribution of SNRs in the LMC and the connection with their
environment, characterised by various SFHs. We tentatively typed all LMC SNRs
to constrain the ratio of core-collapse to type Ia SN rates in the LMC. We
compared the X-ray-derived column densities to HI maps to probe the
three-dimensional structure of the LMC. This work provides the first
homogeneous catalogue of X-ray spectral properties of LMC SNRs. It offers a
complete census of LMC SNRs exhibiting Fe K lines (13% of the sample), or
revealing contribution from hot SN ejecta (39%). Abundances in the LMC ISM are
found to be 0.2-0.5 solar, with a lower [/Fe] than in the Milky Way.
The ratio of CC/type Ia SN in the LMC is , lower than in local SN surveys and galaxy clusters.
Comparison of X-ray luminosity functions of SNRs in Local Group galaxies
reveals an intriguing excess of bright objects in the LMC. We confirm that 30
Doradus and the LMC Bar are offset from the main disc of the LMC, to the far
and near sides, respectively. (abridged)Comment: Accepted for publication in Astronomy and Astrophysics. 54 pages, 18
figures, 12 tables. The resolution of the figures has been reduced compared
to the journal version; v2: New title, minor text edits; v3: Correct version
Candida Urinary Tract Infection: Pathogenesis
Candida species are unusual causes of urinary tract infection (UTI) in healthy individuals, but common in the
hospital setting or among patients with predisposing diseases and structural abnormalities of the kidney and
collecting system. The urinary tract may be invaded in either an antegrade fashion from the bloodstream or
retrograde via the urethra and bladder. Candida species employ a repertoire of virulence factors, including
phenotypic switching, dimorphism, galvano - and thigmotropism, and hydrolytic enzymes, to colonize and then
invade the urinary tract. Antegrade infection occurs primarily among patients predisposed to candidemia. The
process of adherence to and invasion of the glomerulus, renal blood vessels, and renal tubules by Candida
species was elegantly described in early histopathologic studies. Armed with modern molecular biologic
techniques, the various virulence factors involved in bloodborne infection of the kidney are gradually being
elucidated. Disturbances of urine flow, whether congenital or acquired, instrumentation of the urinary tract,
diabetes mellitus, antimicrobial therapy, and immunosuppression underlie most instances of retrograde
Candida UTI. In addition, bacterial UTIs caused by Enterobacteriaceae may facilitate the initial step in the
process. Ascending infections generally do not result in candidemia in the absence of obstruction
Candida Urinary Tract Infection: Pathogenesis
Candida species are unusual causes of urinary tract infection (UTI) in healthy individuals, but common in the
hospital setting or among patients with predisposing diseases and structural abnormalities of the kidney and
collecting system. The urinary tract may be invaded in either an antegrade fashion from the bloodstream or
retrograde via the urethra and bladder. Candida species employ a repertoire of virulence factors, including
phenotypic switching, dimorphism, galvano - and thigmotropism, and hydrolytic enzymes, to colonize and then
invade the urinary tract. Antegrade infection occurs primarily among patients predisposed to candidemia. The
process of adherence to and invasion of the glomerulus, renal blood vessels, and renal tubules by Candida
species was elegantly described in early histopathologic studies. Armed with modern molecular biologic
techniques, the various virulence factors involved in bloodborne infection of the kidney are gradually being
elucidated. Disturbances of urine flow, whether congenital or acquired, instrumentation of the urinary tract,
diabetes mellitus, antimicrobial therapy, and immunosuppression underlie most instances of retrograde
Candida UTI. In addition, bacterial UTIs caused by Enterobacteriaceae may facilitate the initial step in the
process. Ascending infections generally do not result in candidemia in the absence of obstruction
Status of the Standard Solar Model Prediction of Solar Neutrino Fluxes
The Standard Solar Model (BP04) predicts a total 8B neutrino flux that is
17.2% larger than measured in the salt phase of the SNO detector (and if it
were significant it will indicate oscillation to sterile neutrinos). Hence it
is important to examine in details uncertainties (and values) of inputs to the
SSM. Currently, the largest fractional uncertainty is due to the new evaluation
of the surface composition of the sun. We examine the nuclear input on the
formation of solar 8B [S17(0)] and demonstrate that it is still quite uncertain
due to ill known slope of the measured astrophysical cross section factor and
thus ill defined extrapolation to zero energy. This yields an additional
reasonably estimated uncertainty due to extrapolation of +0.0 -3.0 eV-b (+0%
-14%). Since a large discrepancy exists among measured as well as among
predicted slopes, the value of S17(0) is dependent on the choice of data and
theory used to extrapolate S17(0). This situation must be alleviated by new
measurement(s). The "world average" is driven by the Seattle result due to the
very small quoted uncertainty, which we however demonstrate it to be an
over-estimated accuracy. We propose more realistic error bars for the Seattle
results based on the published Seattle data.Comment: Fifth International Conferenceon Non-Accelerator New Physics, Dubna,
June 20-25, 2005. Work Supported by USDOE Grant No. DE-FG02-94ER4087
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