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Estimation of porosity at a millimeter scale would be an order of magnitude finer resolution than traditional logging techniques. This enables proper description of reservoirs with thin layers and fine scale heterogeneities. To achieve this, we propose an end-to-end convolutional neural network (CNN) regression model that automatically predicts continuous porosity at a millimeter scale resolution using two-dimensional whole core CT scan images. More specifically, a CNN regression model is trained to learn from routine core analysis (RCA) porosity measurements. To characterize the performance of such approach, we compare the performance of this model with two linear regression models trained to learn the relationship between the average attenuation and standard deviation of the same two-dimensional images and RCA porosity. Our investigations reveal that the linear models are outperformed by the CNN, indicating the capability of the CNN model in extracting textures that are important for porosity estimations. We compare the predicted porosity results against the total porosity logs calculated from the density log. The obtained results show that the predicted porosity values using the proposed CNN method are well correlated with the core plug measurements and the porosity log. More importantly, the proposed approach can provide accurate millimeter scale porosity estimations, while the total porosity log is averaged over an interval and thus do not show such fine scale variations. Thus, the proposed method can be employed to calibrate the porosity logs, thereby reducing the uncertainties associated with indirect calculations of the porosity from such logs.

Introduction The aim of this study was to evaluate the impact of the contouring methods on dose metrics and their predictive value on tumor control and survival, in both situations of pre-treatment and post-treatment dosimetry, for patients with advanced HCC treated with SIRT. Methods Forty-eight patients who underwent SIRT between 2012 and 2020 were retrospectively included in this study. Target volumes were delineated using two methods: MRI-based contours manually drawn by a radiologist and then registered on SPECT/CT and PET/CT via deformable registration (Pre-CMRI and Post-CMRI), 99mTc-MAA-SPECT and 90Y-microspheres-PET 10% threshold contouring (Pre-CSPECT and Post-CPET). The mean absorbed dose (Dm) and the minimal absorbed dose delivered to 70% of the tumor volume (D70) were evaluated with both contouring methods; the tumor-to-normal liver uptake ratio (TNR) was evaluated with MRI-based contours only. Tumor response was assessed using the mRECIST criteria on the follow-up MRIs. Results No significant differences were found for Dm and TNR between pre- and post-treatment. TNR evaluated with radiologic contours (Pre-CMRI and Post-CMRI) were predictive of tumor control at 6 months on pre- and post-treatment dosimetry (OR 5.9 and 7.1, respectively; p = 0.02 and 0.01). All dose metrics determined with both methods were predictive of overall survival (OS) on pre-treatment dosimetry, but only Dm with MRI-based contours was predictive of OS on post-treatment images with a median of 23 months for patients with a supramedian Dm versus 14 months for the others (p = 0.04). Conclusion In advanced HCC treated with SIRT, Dm and TNR determined with radiologic contours were predictive of tumor control and OS. This study shows that a rigorous clinical workflow (radiologic contours + registration on scintigraphic images) is feasible and should be prospectively considered for improving therapeutic strategy.

In this work, a new dual modality monitoring technique is presented to demonstrate its interest to investigate the salt precipitation dynamics induced by gas flow-through drying. It consists of imaging simultaneously a core flood using both Neutron and X-ray beams. A method to calibrate and process the two signals is presented. It takes advantage of the difference in attenuation between the two ionizing radiations to quantify the different phase saturations and compositions as well as the reduction of porosity caused by salt precipitation. A set of experiments has been conducted at the NeXT-Grenoble beamline of the Institute Laue-Langevin facilities (ILL, France). Experiments were conducted on a homogeneous rock sample of Bentheimer sandstone using dry nitrogen and a 100 g/L KBr brine. The two first experiments aimed to calibrate the dual modality for the different phases. The last two experiments have been conducted with a brine capillary contact maintained at the gas outlet. Experimental data have given new insights into the organization of the three phases (the brine, the gas, and the precipitated salt) when a salt bank is formed in the sample. These quantities computed using dual-modality imaging show great similarities with published work. The salt accumulation was used to estimate the flow rate of brine pumped through the capillary contact to compensate for the brine evaporation in the gas phase. Observations have shown that a reduction of the initial porosity in some sections of the sample by 12–14% was enough to trigger a gas draw-down characterized by the migration of the salt toward the gas inlet. In some conditions (low gas inlet pressure for example), the rise of the water could be fast enough to form a second salt bank higher in the sample. It has been observed that the formation of the second salt bank could spread the precipitated salt in a less damaging configuration for the gas flow, triggering a phase of gas build-up characterized by the withdrawal of the water. These phases of gas draw-down and build-up could alternate until the sample clogs.

The study’s purpose was to assess the safety, feasibility and efficiency of selective arterial embolization (SAE) using N-butyl cyanoacrylate (NBCA) glue before percutaneous cryoablation (PCA) of renal malignancies in patients whose tumor characteristics and/or comorbidities resulted in an unacceptable risk of bleeding. In this single-center retrospective study of 19 consecutive high-risk patients (median age, 74 years) with renal malignancies managed in 2017–2020 by SAE with NBCA followed by PCA, data about patients, tumor and procedures characteristics, complications, renal function and hemoglobin concentration before and after treatment, as well as recurrence were collected. Charlson comorbidity index was ≥4 in 89.5% of patients. Ten patients were treated by antiplatelet and/or anticoagulant therapy. Median tumor largest diameter was 3.75 cm (range, 1–6.5 cm) and R.E.N.A.L. nephrometry score was ≥7 in 80%, indicating substantial tumor complexity. No major complications were recorded and minor complications occurred in 7 patients. No residual tumor was found at 6-week imaging follow-up in 18/19 patients. Tumor recurrence was visible in 1/16 patients at 6-month imaging follow-up. No significant difference was found for renal function after treatment (p = 0.07), whereas significant decrease in hemoglobin concentration was noted (p = 0.00004), although it was relevant for only one patient who required only blood transfusion and no further intervention. SAE prior to PCA is safe and effective for managing renal malignancies in high-risk patients.

La revolution numerique a pour corollaire l’apparition de nouveaux risques. Face a la montee de la menace cyber, les contrats d’assurance representent un outil fondamental pour la resilience de nos societes. Si le marche de l’assurance cyber est en rapide expansion, la quantification des risques economiques associes est encore balbutiante. Elle necessite en effet la conception de modeles predictifs sophistiques – afin de traduire la complexite des phenomenes et leur grande volatilite, notamment le risque d’accumulation de sinistres – tout en tenant compte de la faiblesse des informations utilisees pour les calibrer. Dans cet article, nous mettons en evidence les difficultes rencontrees pour la collecte de donnees pertinentes, et l’impact des comportements des agents sur l’evaluation du risque. Nous exposons egalement un certain nombre de pistes methodologiques explorees pour surmonter ces difficultes. Classification JEL : G11, G22, O33.

International audience; We introduce so-called single-index copulas. They are semi-parametric conditional copulas whose parameter is an unknown link function of a univariate index only. We propose estimates of this link function and of the finite-dimensional unknown parameter. The asymptotic properties of the latter estimates are stated. Thanks to some properties of conditional Kendall's tau, we illustrate our technical conditions with several usual copula families.

This article provides an overview of the current state of digital rock technology, with emphasis on industrial applications. We show how imaging and image analysis can be applied for rock typing and modeling of end-point saturations. Different methods to obtain a digital model of the pore space from pore scale images are presented, and the strengths and weaknesses of the different methods are discussed. We also show how imaging bridges the different subjects of geology, petrophysics and reservoir simulations, by being a common denominator for results in all these subjects. Network modeling is compared to direct simulations on grid models, and their respective strengths are discussed. Finally we present an example of digital rock technology applied to a sandstone oil reservoir. Results from digital rock modeling are compared to results from traditional laboratory experiments. We highlight the mutual benefits from conducting both traditional experiments and digital rock modeling., Comment: 36 pages, 18 figures

In this paper, we consider nonparametric copula inference under bivariate censoring. Based on an estimator of the joint cumulative distribution function, we define a discrete and two smooth estimators of the copula. The construction that we propose is valid for a large number of estimators of the distribution function, and therefore for a large number of bivariate censoring frameworks. Under some conditions on the tails of the distributions, the weak convergence of the corresponding copula processes is obtained in $l^{\infty}([0,1]^2).$ We derive the uniform convergence rates of the copula density estimators deduced from our smooth copula estimators. Investigation on the practical behavior of our estimators is done through a simulation study and two real data applications, corresponding to different censoring settings. We use our nonparametric estimators to define a goodness-of-fit procedure for parametric copula models. A new bootstrap scheme is proposed to compute the critical values.

In this paper we provide a new nonparametric estimator of the joint distribution of two lifetimes under random right censoring and left truncation which can be seen as a bivariate extension of the Kaplan–Meier estimator. We derive asymptotic results for this estimator, including uniform n 1 / 2 -consistency, and develop a general methodology for bivariate lifetime modeling, a critical issue in studying reversion conditions that are commonplace in defined benefit pensions and private annuity contracts. An application to goodness-of-fit for survival copula models is discussed. We show that the procedures that we use are consistent, and propose a bootstrap procedure based on our estimator to compute the critical values. The new technique that we propose is tested on the Canadian dataset initially studied by Frees et al. (1996) .

In a regression model with univariate censored responses, a new estimator of the joint distribution function of the covariates and response is proposed, under the assumption that the response and the censoring variable are independent conditionally to the covariates. This estimator is based on the conditional Kaplan-Meier estimator of Beran (1981), and happens to be an extension of the multivariate empirical distribution function used in the uncensored case. We derive asymptotic i.i.d. representations for the integrals with respect to the measure defined by this estimated distribution function. These representations hold even in the case where the covariates are multidimensional under some additional assumption on the censoring. Applications to censored regression and to density estimation are considered.

We report on a fully bi-directional 680~km fiber link connecting two cities for which the equipment, the set up and the characterization are managed for the first time by an industrial consortium. The link uses an active telecommunication fiber network with parallel data traffic and is equipped with three repeater laser stations and four remote double bi-directional Erbium-doped fiber amplifiers. We report a short term stability at 1~s integration time of $5.4\times 10^{-16}$ in 0.5~Hz bandwidth and a long term stability of $1.7\times10^{-20}$ at 65\,000 s of integration time. The accuracy of the frequency transfer is evaluated as $3\times 10^{-20}$. No shift is observed within the statistical uncertainty. We show a continuous operation over 5 days with an uptime of 99.93$\%$. This performance is comparable with the state of the art coherent links established between National Metrology Institutes in Europe. It is a first step in the construction of an optical fiber network for metrology in France, which will give access to an ultra-high performance frequency standard to a wide community of scientific users., 16 pages, 7 figures

In this article, we describe an experiment performed at the Laboratoire de physique des lasers and dedicated to an optical measurement of the Boltzmann constant k B . With the proposed innovative technique, determining k B comes down to an ordinary frequency measurement. The method consists in measuring as accurately as possible the Doppler absorption profile of a rovibrational line of ammonia in thermal equilibrium. This profile is related to the Maxwell–Boltzmann molecular velocity distribution along the laser beam. A fit of the absorption line shape leads to a determination of the Doppler width proportional to k B T and thus to a determination of the Boltzmann constant. The laser source is an ultra-stable CO2 laser with a wavelength λ ≈ 10 μm . The absorption cell is placed in a thermostat, keeping the temperature at 273.15 K within 1.4 mK. We were able to measure k B with a relative uncertainty as small as 3.8 × 10 − 5 , which represents an improvement of an order of magnitude for an integration time comparable to our previous measurement published in 2007. To cite this article: K. Djerroud et al., C. R. Physique 10 (2009).

In this article, we propose some new generalizations of M-estimation procedures for single-index regression models in presence of randomly right-censored responses. We derive consistency and asymptotic normality of our estimates. The results are proved in order to be adapted to a wide range of techniques used in a censored regression framework (e.g. synthetic data or weighted least squares). As in the uncensored case, the estimator of the single-index parameter is seen to have the same asymptotic behavior as in a fully parametric scheme. We compare these new estimators with those based on the average derivative technique of Lu and Burke [2005. Censored multiple regression by the method of average derivatives. J. Multivariate Anal. 95, 182–205] through a simulation study.

The composition of carbonate minerals formed in past and present oceans is assumed to be significantly controlled by temperature and seawater composition. To determine if and how temperature is kinetically responsible for the amount of Mg incorporated in calcite, we quantified the influence of temperature and specific dissolved components on the complex mechanism of calcite precipitation in seawater. A kinetic study was carried out in artificial seawater and NaCl–CaCl 2 solutions, each having a total ionic strength of 0.7 M. The constant addition technique was used to maintain [Ca 2+ ] at 10.5 mmol kg −1 while [ CO 3 2 - ] was varied to isolate the role of this variable on the precipitation rate of calcite. Our results show that the overall reaction of calcite precipitation in both seawater and NaCl–CaCl 2 solutions is dominated by the following reaction: Ca 2 + + CO 3 2 - ↔ k b , k f Ca CO 3 where k f and k b are the forward and backward reaction rate constants, respectively, while the net precipitation rate R, can be described at any temperature by R = k f a Ca 2 + n 1 a CO 3 2 - n 2 - k b or in its logarithmic form Log (R + k b ) = Log K f + n 2 Log [ CO 3 2 - ] where n i are the partial reaction orders with respect to the participating ions, a the ion activity, γ the activity coefficients, and K f = k f ( a Ca 2 + ) n 1 ( γ CO 3 2 - ) n 2 is a constant at a given temperature. We find that, irrespective of the presence of Mg, SO 4 , and other specific seawater components known calcite reaction rate inhibitors, the partial reaction order with respect to carbonate ion concentration changes from 2 to 5 while the rate constant K f , increases by 3–4 orders of magnitude when temperature varies from 5 to 70 °C. The observed variations of the kinetic mechanism resulting from the temperature changes are correlated with the variable amount of Mg incorporated in the formed calcites. Moreover, at a given temperature, the increase in the saturation state enhances the rate of calcite precipitation without influencing the reaction mechanism and without changing the amount of Mg incorporated in the growing lattice. Thus, the results of this experimental study are consistent with present-day abiotic marine carbonates where low-Mg calcite cements are mainly associated with cool water while high-Mg carbonates are dominantly found in warm-water environments. This suggests that the apparent inverse relationship between the global average paleo-temperature and the Mg/Ca ratio in past formed marine carbonate may correspond to major changes in seawater saturation state or (Mg/Ca) ratios that in turn should reflect significant changes in the relative seawater geochemical cycles of these cations.

International audience; We develop two kernel smoothing based tests of a parametric mean-regression model against a nonparametric alternative when the response variable is right-censored. The new test statistics are inspired by the synthetic data and the weighted least squares approaches for estimating the parameters of a (non)linear regression model under censoring. The asymptotic critical values of our tests are given by the quantiles of the standard normal law. The tests are consistent against fixed alternatives, local Pitman alternatives and uniformly over alternatives in H\"{o}lder classes of functions of known regularity.

We have developed a narrow-band controller in the MHz range, based on a field-programmable gate array. It is used to control the probe beam intensity in frequency-modulated spectroscopy experiments with an acoustooptic modulator. The residual amplitude modulation at the modulation frequency (2.5 MHz) is reduced by 50 dB. The first-harmonic detection of the signals is operated in saturation spectroscopy of I/sub 2/ at 514.5 nm and 501.7 nm. A reduction of the background noise and a large increase in the signal-to-noise ratio are obtained.

A narrow-band controller is described, based on an FPGA device for the stabilisation of laser beam intensity at 2.5 MHz. 70 dB rejection of the amplitude modulation of a laser beam is obtained. The noise rejection near 2.5 MHz is also studied.

We present petrophysical data derived from pore-network modelling of CO2-brine pore systems from the Krechba CO2 Storage Site (part of the In Salah Gas Joint Venture project operated by BP, Sonatrach and Statoil). The Carboniferous sandstone reservoir formation has relatively low permeability (c. 10 mD) and is characterized by abundant and variable cementation–mainly quartz, patchy carbonates, grain-coating chlorites and pyrite. These petrographic characteristics make obtaining measurements and estimation of single and multiphase flow properties challenging. Pore-scale modelling is an important new tool which can supplement special core analysis measurements by providing single and two phase flow functions for a range of rock and pore types. CO2/water relative permeability measurements have been carried out on four composite core plugs at reservoir conditions (95°C and 180 bars pore pressure). We have reviewed these experimental data and compared them to new predictions from several pore-scale reconstructions of the matching rock samples. First porosity, absolute permeability and formation factor were calculated and compared experimental data. Pore-networks were then extracted from the rock models and used as inputs to the simulation of CO2/water displacements. Primary drainage and waterflooding sequences were simulated to establish end-point saturations (i.e. Swi and trapped CO2 saturation), capillary pressure and relative permeability curves. Very good agreement was found between the experimental results and those derived from calculations of petrophysical parameters on rock models and multiphase flow simulations through their respective pore-networks. Calculated permeability and porosity match the values estimated from the available logs, and the calculated average cementation exponent (m) for the three reconstructed samples is 2.05, comparable with the experimental value of 1.98. Swi values obtained from the simulations range from 0.29 to 0.34, similar but slightly lower than those obtained from the steady-state experimental study–0.39 to 0.44. The simulated residual CO2 saturation ranges from 36% to 44%. The capillary trapping ensures that part of the injected CO2 will stay disconnected as isolated CO2 clusters in the pore space. These values are comparable to the residual gas saturation estimated from the experiments (from 15 to 40 %). Differences between experiments and models can be related to differences in pore types which are better defined in the pore-network models. We conclude that pore-scale modelling is able to reproduce and supplement special core analysis experiments, even when the simulations are based on relatively simple assumptions, such as non-reactive and immiscible fluids. In addition, pore-scale modelling allows the correlation of end-points with the geometry, topology and morphology of the pore space of the rock, allowing us to improve the basic understanding of CO2 trapping mechanisms in heterogeneous formations.