•Bayesian methods are derived to estimate point-like groundwater pollution sources.•Positivity is imposed to source parameters through using truncated-Gaussian priors.•Inhomogeneity is introduced on ...data noise using different variances for the sensors.•Iterative MCMC and VB provide different approximations for the same posterior density.•MCMC is asymptotically more accurate and VB is broadly computationally more efficient.
This paper considers the problem of estimating point-like pollution sources of groundwater layers. To cope with the ill-posed character of this problem, a parametric Bayesian framework has been recently established. In this framework, where the priors for the source parameters are either uniform or Gaussian and the observation noise is homogeneous, a stochastic Markov Chain Monte Carlo (MCMC) algorithm has been proposed to compute the posterior distribution of both source parameters and noise variance. Here, we consider a more general model with truncated-Gaussian priors for pollution quantity and spreading time parameter, which gathers advantages of uniform and Gaussian choices, and an inhomogeneous noise, which accounts for the spatial diversity among sensors. For this model, we extend the existing stochastic algorithm, then propose a concurrent deterministic algorithm based on the variational Bayesian (VB) approach. This approach designs an approximation of the posterior law based on a separable from. The proposed MCMC and VB algorithms target the exact posterior and the approximated posterior, respectively. It is further shown that the former is more accurate, while the latter is computationally more efficient. Results of numerical experiments conducted using an experimental platform to compare the performances of the proposed schemes are presented.
(Ca
1-x
Fe
x
)
3
Co
4
O
9
polycrystalline samples (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1 and 0.2) have been prepared by solid state reaction and sintered by spark plasma sintering. Their ...thermoelectric properties have been studied between 323 and 1000 K. The substitution limit is low (< 3%). For higher iron contents, formation of Co
3
O
4
, Ca
2
FeCoO
5
and a calcium ferrite compound occurs. Concerning electrical conductivity and power factor, an optimum value exists for x = 0.03 substitution. This optimum power factor is circa 10% higher than the one of the unsubstituted sample. The optimum thermal diffusivity is measured for the sample with x = 0.02 and is circa 9% lower than the one of the unsubstituted sample. Therefore, the dimensionless figure of merit ZT is finally increased by 14% for the (Ca
0.98
Fe
0.02
)
3
Co
4
O
9
and (Ca
0.97
Fe
0.03
)
3
Co
4
O
9
compositions.
This paper is devoted to the problem of sampling Gaussian distributions in high dimension. Solutions exist for two specific structures of inverse covariance: sparse and circulant. The proposed ...algorithm is valid in a more general case especially as it emerges in linear inverse problems as well as in some hierarchical or latent Gaussian models. It relies on a perturbation-optimization principle: adequate stochastic perturbation of a criterion and optimization of the perturbed criterion. It is proved that the criterion optimizer is a sample of the target distribution. The main motivation is in inverse problems related to general (nonconvolutive) linear observation models and their solution in a Bayesian framework implemented through sampling algorithms when existing samplers are infeasible. It finds a direct application in myopic/unsupervised inversion methods as well as in some non-Gaussian inversion methods. An illustration focused on hyperparameter estimation for super-resolution method shows the interest and the feasibility of the proposed algorithm.
Al-doped ZnO particles were obtained by a simple route: soda addition in aqueous cationic solution. The effects of temperature, hydrolysis duration, reagent concentration and time were investigated. ...A non-topotactic reaction mechanism, involving firstly the precipitation of various hydroxide compounds depending on the route (low or high pH), followed by the dissolution–recrystallization of the hydroxide species into ZnO was demonstrated. The Al concentration in the final ZnO nanopowders did not exceed 0.3at.% which correspond to the solubility limit of Al in ZnO. The different experimental conditions allow the morphology of ZnO particles to be controlled from isotropic nanoparticles of several tens of nanometers, platelets of several hundreds of nanometers or agglomerates of needle like particles.
SEM image of Al doped ZnO. Display omitted
•Al-doped ZnO nanoparticles have been synthesized with a simple precipitation process.•Various hydroxide compounds are intermediary phases.•Various morphologies and sizes have been obtained.
Layered cobalt oxides have shown high thermoelectric properties. The n=1 member of the Ban+1ConO3n+3(Co8O8) family, Ba2Co9O14, a new layered cobalt oxides family with Co(II) and Co(III) in the CdI2 ...layers, has been synthesized by solid state reaction and sintered as dense ceramics (relative density∼93%) by Spark Plasma Sintering. It presents promising p-type thermoelectric properties at high temperature. The dimensionless figure of merit ZT is 0.032 at 660K and 0.04 at 1000K, which is about one quarter to one third of the ZT value of Ca3Co4O9 ceramics.
(1−x)Ca3Co4O9/xCo3O4 composites samples with x=0, 10, 20 and 50vol% have been prepared by solid state reaction and sintered by spark plasma sintering. Their thermoelectric properties have been ...studied in the range 323–1000K. No reaction occurs between Co3O4 and Ca3Co4O9 particles during the high temperature treatment. The addition of Co3O4 particles within a Ca3Co4O9 matrix strongly influences the thermoelectric properties. The powerfactor decreases as the Co3O4 content increases. As the thermal conductivity increases, this leads to lower ZT values. These modifications of the thermoelectric properties are consistent with the compressive strain on Ca3Co4O9 originating from the mismatch of thermal expansion coefficients of Ca3Co4O9 and Co3O4.
Context. We develop models for time lag between the maxima of the source brightness in different wavelengths during a transient flash of luminosity that is connected with a short-period increase of ...the mass flux onto the central compact object. Aims. We derive a simple formula for finding the time delay among events in different wavelengths which is valid in general for all disk-accreting cosmic sources. We quantitatively also discuss a model for time-lag formation in active galactic nuclei (AGNs). Methods. In close binaries with accretion disks, the time lag is connected with effects of viscosity that define a radial motion of matter in the accretion disk. In AGN flashes, the infalling matter has a low angular momentum, and the time lag is defined by the free-fall time to the gravitating center. Results. We show the validity of these models by means of several examples of galactic and extragalactic accreting sources.
In healthy subjects (HS), transcranial magnetic stimulation (TMS) applied during ‘linguistic’ tasks discloses excitability changes in the dominant hemisphere primary motor cortex (M1). We ...investigated ‘linguistic’ task‐related cortical excitability modulation in patients with adductor‐type spasmodic dysphonia (ASD), a speech‐related focal dystonia. We studied 10 ASD patients and 10 HS. Speech examination included voice cepstral analysis. We investigated the dominant/non‐dominant M1 excitability at baseline, during ‘linguistic’ (reading aloud/silent reading/producing simple phonation) and ‘non‐linguistic’ tasks (looking at non‐letter strings/producing oral movements). Motor evoked potentials (MEPs) were recorded from the contralateral hand muscles. We measured the cortical silent period (CSP) length and tested MEPs in HS and patients performing the ‘linguistic’ tasks with different voice intensities. We also examined MEPs in HS and ASD during hand‐related ‘action‐verb’ observation. Patients were studied under and not‐under botulinum neurotoxin‐type A (BoNT‐A). In HS, TMS over the dominant M1 elicited larger MEPs during ‘reading aloud’ than during the other ‘linguistic’/‘non‐linguistic’ tasks. Conversely, in ASD, TMS over the dominant M1 elicited increased‐amplitude MEPs during ‘reading aloud’ and ‘syllabic phonation’ tasks. CSP length was shorter in ASD than in HS and remained unchanged in both groups performing ‘linguistic’/‘non‐linguistic’ tasks. In HS and ASD, ‘linguistic’ task‐related excitability changes were present regardless of the different voice intensities. During hand‐related ‘action‐verb’ observation, MEPs decreased in HS, whereas in ASD they increased. In ASD, BoNT‐A improved speech, as demonstrated by cepstral analysis and restored the TMS abnormalities. ASD reflects dominant hemisphere excitability changes related to ‘linguistic’ tasks; BoNT‐A returns these excitability changes to normal.
In healthy subjects, magnetic stimulation over dominant primary motor area elicited larger MEPs during loud reading compared to other linguistic and non linguistic tasks, while in spasmodic dysphonia (ASD) it elicited MEPs of increased amplitude also during syllabic phonation. In ASD, BoNT‐A improved speech as demonstrated by cepstral analysis and restored the TMS abnormalities. We conclude that spasmodic dysphonia is characterized by abnormal dominant speech‐related network activation.
Background and purpose
To identify adverse events (AEs) significantly associated with perampanel treatment in double‐blind clinical studies (RCTs). Serious AEs, study withdrawals due to AEs and ...dose–effect responses of individual AEs were also investigated.
Methods
All placebo controlled, double‐blind RCTs investigating therapeutic effects of oral perampanel were searched. AEs were assessed for their association with perampanel after exclusion of synonyms, rare AEs and non‐assessable AEs. Risk difference (RD) was used to evaluate the association of any AE (99% confidence intervals) and withdrawals or serious AEs (95% confidence intervals) with perampanel.
Results
Nine RCTs (five in pharmacoresistant epilepsy and four in Parkinson's disease) were included in our study. Almost 4000 patients had been recruited, 2627 of whom were randomized to perampanel and treated with drug doses of 0.5 mg/day (n = 68), 1 mg/day (n = 65), 2 mg/day (n = 753), 4 mg/day (n = 1017), 8 mg/day (n = 431) or 12 mg/day (n = 293). Serious AEs were not significantly associated with perampanel treatment. The experimental drug was significantly associated with an increased risk of AE‐related study withdrawals at 4 mg/day RD (95% confidence interval) 0.03 (0.00, 0.06) and 12 mg/day RD (95% confidence interval) 0.13 (0.07, 0.18). Of 15 identified AEs, five (dizziness, ataxia, somnolence, irritability and weight increase) were found to be significantly associated with perampanel and one (seizure worsening) was significantly associated with placebo.
Conclusions
Vestibulocerebellar AEs (dizziness, ataxia), sedative effects (somnolence), irritability and weight increase were significantly associated with perampanel treatment.
The paper deals with the construction of images from visibilities acquired using aperture synthesis instruments: Fourier synthesis, deconvolution, and spectral interpolation/extrapolation. Its ...intended application is to specific situations in which the imaged object possesses two superimposed components: (i) an extended component together with (ii) a set of point sources. It is also specifically designed to the case of positive maps, and accounts for a known support. Its originality lies within joint estimation of the two components, coherently with data, properties of each component, positivity and possible support. We approach the subject as an inverse problem within a regularization framework: a regularized least-squares criterion is specifically proposed and the estimated maps are defined as its minimizer. We have investigated several options for the numerical minimization and we propose a new efficient algorithm based on augmented Lagrangian. Evaluation is carried out using simulated and real data (from radio interferometry) demonstrating the capability to accurately separate the two components.
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