Currently, magnetic resonance imaging is the most sensitive imaging technique for detecting cancer processes in early stages. Regarding breast cancer, due to the characteristics of the tissue as it ...is formed by ducts (tubular structure), anisotropic diffusion should be considered instead of general isotropic Diffusion Weighted Imaging (DWI). Anisotropic diffusion is studied by applying a technique called Diffusion Tensor Imaging (DTI), where the diffusion gradient is applied with several different directions, calculated by Ordinary Least Squares (OLS) in clinical practice. In this paper, we propose a new DTI calculation method based on Partial Least Squares (PLS), which has some advantages over the traditional OLS calculation: i) the PLS model provides valid biomarkers (non-negative eigenvalues) in a larger percentage of pixels, improving the traditional OLS calculation and reducing the effect of noisier images; ii) OLS tensors are calculated pixel-by-pixel, whereas the PLS method calculates only one model taking advantage of the correlation structure between pixels with similar characteristics, obtaining more reliable estimations; iii) PLS performance is quite reliable when lowering the number of directions of the magnetic field, while this is not the case of OLS. PLS keeps providing a good solution even with low functional resolution equipment, reducing costs and acquisition times, which is an important advantage for its widespread use in value-based medicine-oriented clinical practice.
•A PLS-based approach is proposed for the calculation of the DTI with the objective of better assessing breast cancer.•The eigenvalues and the proposed biomarkers: dmax and 1-Rmax have been proved as helpful parameters for identifying tumors.•PLS outperforms OLS when the number of gradient directions is low (6). OLS cannot perform properly in these conditions.
Context.
The observations of global stellar oscillations of post-main-sequence stars by space-based photometry missions have allowed us to directly determine their internal rotation. These ...constraints have pointed towards the existence of angular momentum transport processes not accounted for in theoretical models. Constraining the properties of their internal rotation thus appears to be the golden path to determine the physical nature of these missing dynamical processes.
Aims.
Our aim is to determine the robustness of a new approach to study the internal rotation of post-main-sequence stars, using parametric rotation profiles coupled to a global optimization technique.
Methods.
We tested our methodology on Kepler-56, a red giant observed by the
Kepler
mission. First, we carried out an extensive modelling of the star using global and local minimizations techniques, and seismic inversions. Then, using our best model, we study in details its internal rotation profile, we adopted a Bayesian approach to constrain stellar parametric predetermined rotation profiles using a Markov chain Monte Carlo analysis of the rotational splittings of mixed modes.
Results.
Our Markov chain Monte Carlo analysis of the rotational splittings allows us to determine the core and envelope rotation of Kepler-56 and gives us hints about the location of the transition between the slowly rotating envelope and the fast-rotating core. We are able to discard a rigid rotation profile in the radiative regions followed by a power law in the convective zone, and we show that the data favours a transition located in the radiative region, as predicted by processes originating from a turbulent nature such as for example magnetic instabilities.
Conclusions.
Our new approach to studying the internal rotation of red giants constitutes a viable option to analyse
Kepler
targets and allows us to put stringent constraints on the properties of the missing angular momentum transport process acting in post-main-sequence stars. Our analysis of Kepler-56 indicates that turbulent processes whose transport efficiency is reduced by chemical gradients are favoured, while large-scale fossil magnetic fields are disfavoured as a solution to the missing angular momentum transport.
We present a seismic study of the β Cephei star θ Ophiuchi. Our analysis is based on the observation of one radial mode, one rotationally split ℓ= 1 triplet and three components of a rotationally ...split ℓ= 2 quintuplet for which the m values were well identified by spectroscopy. We identify the radial mode as fundamental, the triplet as p1 and the quintuplet as g1. Our non‐local thermodynamic equilibrium abundance analysis results in a metallicity and CNO abundances in full agreement with the most recent updated solar values. With X∈0.71, 0.7211 and Z∈0.009, 0.015, and using the Asplund et al. mixture but with a Ne abundance about 0.3 dex larger, the matching of the three independent modes enables us to deduce constrained ranges for the mass (M= 8.2 ± 0.3 M⊙) and central hydrogen abundance (Xc= 0.38 ± 0.02) of θ Oph and to prove the occurrence of core overshooting (αov= 0.44 ± 0.07). We also derive an equatorial rotation velocity of 29 ± 7 km s−1. Moreover, we show that the observed non‐equidistance of the ℓ= 1 triplet can be reproduced by the second‐order effects of rotation. Finally, we show that the observed rotational splitting of two modes cannot rule out a rigid rotation model.
We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30 minute ...sampling, reveal clear oscillations in a large sample of G and K giants, extending in luminosity from the red clump down to the bottom of the giant branch. We confirm a strong correlation between the large separation of the oscillations (Δν) and the frequency of maximum power (νmax). We focus on a sample of 50 low-luminosity stars (νmax > 100 μHz, L <~ 30 L sun) having high signal-to-noise ratios and showing the unambiguous signature of solar-like oscillations. These are H-shell-burning stars, whose oscillations should be valuable for testing models of stellar evolution and for constraining the star formation rate in the local disk. We use a new technique to compare stars on a single échelle diagram by scaling their frequencies and find well-defined ridges corresponding to radial and non-radial oscillations, including clear evidence for modes with angular degree l = 3. Measuring the small separation between l = 0 and l = 2 allows us to plot the so-called C-D diagram of δν02 versus Δν. The small separation δν01 of l = 1 from the midpoint of adjacent l = 0 modes is negative, contrary to the Sun and solar-type stars. The ridge for l = 1 is notably broadened, which we attribute to mixed modes, confirming theoretical predictions for low-luminosity giants. Overall, the results demonstrate the tremendous potential of Kepler data for asteroseismology of red giants.
•We improve Multivariate Image Analysis for defect detection and location.•We compare the statistical properties of the detection performance capability.•We discuss the differences and advantages of ...our methodology.
The monitoring, fault detection and visualization of defects are a strategic issue for product quality. This paper presents a novel methodology based on the integration of textural Multivariate Image Analysis (MIA) and multivariate statistical process control (MSPC) for process monitoring. The proposed approach combines MIA and p-control charts, as well as T2 and RSS images for defect location and visualization. Simulated images of steel plates are used to illustrate the monitoring performance of it. Both approaches are also applied on real clover images.
The clear detection with CoRoT and KEPLER of radial and non-radial solar-like oscillations in many red giants paves the way for seismic inferences on the structure of such stars. We present an ...overview of the properties of the adiabatic frequencies and frequency separations of radial and non-radial oscillation modes for an extended grid of models. We highlight how their detection allows a deeper insight into the internal structure and evolutionary state of red giants. In particular, we find that the properties of dipole modes constitute a promising seismic diagnostic tool of the evolutionary state of red giant stars. We compare our theoretical predictions with the first 34 days of KEPLER data and predict the frequency diagram expected for red giants in the CoRoT exofield in the galactic center direction.
Uncertainties on central mixing in main-sequence (MS) and core He-burning (He-B) phases affect key predictions of stellar evolution such as late evolutionary phases, chemical enrichment, ages, etc. ...We propose a test of the extension of extra-mixing in two relevant evolutionary phases based on period spacing ( Delta P) of solar-like oscillating giants. From stellar models and their corresponding adiabatic frequencies (respectively, computed with ATON and LOSC codes), we provide the first predictions of the observable Delta P for stars in the red giant branch and in the red clump (RC). We find (1) a clear correlation between Delta P and the mass of the helium core (M sub(He)); the latter in intermediate-mass stars depends on the MS overshooting, and hence it can be used to set constraints on extra-mixing during MS when coupled with chemical composition; and (2) a linear dependence of the average value of the asymptotic period spacing (left angle bracket Delta Pright angle bracketa) on the size of the convective core during the He-B phase. A first comparison with the inferred asymptotic period spacing for Kepler RC stars also suggests the need for extra-mixing during this phase, as evinced from other observational facts.
In current radiology practice, multi-parametric magnetic resonance imaging (mpMRI) has recently become a key tool in diagnostic and therapeutic decisions. Although it is based on the subjective ...assessment of T2-weighted images, as well as perfusion-weighted and diffusion-weighted sequences, further quantitative parameters can also be derived from them for improving lesion phenotyping. Despite these parameters are usually exploited in a univariate way, ignoring the benefits of a real multivariate approach, still it is the gold standard imaging technique to assess prostate cancer location and probability of malignancy. In this paper, pharmacokinetic (perfusion) and exponential (diffusion) clinical models, as well as latent variable-based multivariate statistical models like multivariate curve resolution-alternating least squares (MCR-ALS), have been calculated and analyzed with sequential multi block-partial least squares discriminant analysis (SMB-PLS-DA) including technique-block differentiation, in order to better assess for cancer aggressiveness based on Gleason scales. The best prediction result was achieved by the ordered combination of diffusion blocks (MCR-ALS and exponential models) and normalized T2 values. The perfusion blocks did not improve the results obtained by diffusion and T2-weighted based parameters alone, so they can be removed from the SMB-PLS-DA model.
•The capability of MRI clinical and MCR-ALS models have been jointly studied in order to better assess cancer aggressiveness.•SMB-PLS-DA has been employed for selecting the best sources in order to discriminate aggressiveness based on Gleason scales.•Statistical significant results shows that perfusion models do not provide any additional relevant information.
With the advent of the space missions CoRoT and Kepler, it has recently become feasible to determine precise asteroseismic masses and relative ages for large samples of red giant stars. We present ...the CoRoGEE dataset, obtained from CoRoT light curves for 606 red giants in two fields of the Galactic disc that have been co-observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). We used the Bayesian parameter estimation code PARAM to calculate distances, extinctions, masses, and ages for these stars in a homogeneous analysis, resulting in relative statistical uncertainties of ≲2% in distance, ~4% in radius, ~9% in mass and ~25% in age. We also assessed systematic age uncertainties stemming from different input physics and mass loss. We discuss the correlation between ages and chemical abundance patterns of field stars over a broad radial range of the Milky Way disc (5 kpc <RGal< 14 kpc), focussing on the α/Fe-Fe/H-age plane in five radial bins of the Galactic disc. We find an overall agreement with the expectations of pure chemical-evolution models computed before the present data were available, especially for the outer regions. However, our data also indicate that a significant fraction of stars now observed near and beyond the solar neighbourhood migrated from inner regions. Mock CoRoGEE observations of a chemodynamical Milky Way disc model indicate that the number of high-metallicity stars in the outer disc is too high to be accounted for even by the strong radial mixing present in the model. The mock observations also show that the age distribution of the α/Fe-enhanced sequence in the CoRoGEE inner-disc field is much broader than expected from a combination of radial mixing and observational errors. We suggest that a thick-disc/bulge component that formed stars for more than 3 Gyr may account for these discrepancies. Our results are subject to future improvements due to (a) the still low statistics, because our sample had to be sliced into bins of Galactocentric distances and ages; (b) large uncertainties in proper motions (and therefore guiding radii); and (c) corrections to the asteroseismic mass-scaling relation. The situation will improve not only upon the upcoming Gaia data releases, but also with the foreseen increase in the number of stars with both seismic and spectroscopic information.
We report the discovery by the WASP transit survey of two new highly irradiated giant planets. WASP-64 b is slightly more massive (1.271 ± 0.068 MJup) and larger (1.271 ± 0.039 RJup) than Jupiter, ...and is in very-short (a = 0.02648 ± 0.00024 AU, P = 1.5732918 ± 0.0000015 days) circular orbit around a V = 12.3 G7-type dwarf (1.004 ± 0.028 M⊙, 1.058 ± 0.025 R⊙, Teff = 5500 ± 150 K). Its size is typical of hot Jupiters with similar masses. WASP-72 b has also a mass a bit higher than Jupiter’s (1.461-0.056+0.059 MJup) and orbits very close (0.03708 ± 0.00050 AU, P = 2.2167421 ± 0.0000081 days) to a bright (V = 9.6) and moderately evolved F7-type star (1.386 ± 0.055 M⊙, 1.98 ± 0.24 R⊙, Teff = 6250 ± 100 K). Despite its extreme irradiation (~5.5 × 109 erg s-1 cm-2), WASP-72 b has a moderate size (1.27 ± 0.20 RJup) that could suggest a significant enrichment in heavy elements. Nevertheless, the errors on its physical parameters are still too high to draw any strong inference on its internal structure or its possible peculiarity.
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