Non-local Conservation Law from Stochastic Particle Systems

We consider an interacting particle system in \(\mathbb {R}^d\) modelled as a system of N stochastic differential equations. The limiting behaviour as the size N grows to infinity is achieved as a law of large numbers for the empirical density process associated with the interacting particle system.     

Assessment of absolute blood volume in carcinoma by USPIO contrast-enhanced MRI

OBJECTIVES: The characterization of tumor vasculature is essential in studying tumor physiology. The aim of this study was to develop a new method - based on water proton MR density measurements, in combination with ultrasmall superparamagnetic iron oxide (USPIO) administration - to measure absolute blood volume (BV) in murine colon carcinoma. MATERIALS AND METHODS: MRI experiments were performed at 7 T. CPMG imaging was performed on subcutaneous murine colon carcinoma in six mice before and after administration of an USPIO blood-pool contrast agent. Density maps were obtained from the signal amplitude at TE=0 of the CPMG decay fit. Post-USPIO density maps were subtracted from pre-USPIO density maps to quantitatively yield absolute tumor BV maps. In a separate group of mice (n=6), the relative vascular area (RVA) of tumors was determined by immunohistochemistry. RESULTS: Ultrasmall superparamagnetic iron oxide administration resulted in a small decrease in the water proton MR density. The BV averaged over the six tumors was 4.6+/-1.6%. The value of the RVA measured by immunohistochemical staining was equal to 3.9+/-2.2%. CONCLUSIONS: After administration of an USPIO blood-pool agent (T(2) relaxivity > 100 mM(-1) s(-1)), the blood water protons become MRI invisible, and pixel-by-pixel BV map can be obtained by subtracting the calculated post-USPIO density map from the pre-USPIO density map. The value of absolute BV obtained with this novel MR approach is in good agreement with the value of the relative vascular measured by immunohistochemical staining.     

Contribution of an interlaboratory comparison to the certification of the STAM/IRMM-0243 243Am reference material

Following the expression of the need for an americium (Am) standard and particularly for one with a certified americium-243 (²⁴³Am) content, the Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA)/Direction de l’Energie Nucléaire of Marcoule and the European Commission Joint Research Center in Geel carried out a collaborative project for the production of a certified reference material enriched in ²⁴³Am. CEA’s Commission d’ETAblissement des Méthodes d’Analyse organized an interlaboratory comparison on this material prior to the issuing of its certificate. The usefulness of an interlaboratory comparison to assess the measurement capabilities in the field and to confirm the provisional certified values for the amount contents of ²⁴³Am, ²⁴¹Am, total Am, the isotopic composition and the molar mass of Am has been demonstrated. Furthermore this interlaboratory comparison enabled to derive an indicative value for the n(^242mAm)/n(²⁴³Am) isotope amount ratio.

     

EQRAIN: uranium and plutonium interlaboratory exercises from 1997 to 2016—comparison to ITVs-2010

Since 1987, the CEA’s Committee for the establishment of analysis methods (CETAMA) has regularly implemented interlaboratory comparisons, entitled “evaluation of the quality results of analysis in the nuclear industry” (EQRAIN). Notably, the EQRAIN U and EQRAIN Pu interlaboratory comparisons assess proficiency in measuring a mass content of uranium or plutonium in reference solutions. This paper presents the results of measurement uncertainty assessments from EQRAIN U and EQRAIN Pu comparisons over 20 years of exercises (1997–2016). The mathematical approach developed in this work allowed to estimate the impact of short-term systematic and random errors to the overall uncertainty of each analytical method used in the interlaboratory comparison program. This statistical analysis shows a good consistency between measurement uncertainty values from EQRAINs and the measurement uncertainty target values established by the International Atomic Energy Agency for nuclear material balances (ITVs-2010).

     

Cucurbit[7]uril: a very effective host for viologens and their cation radicals

[reaction: see text] The host cucurbit[7]uril (CB7) forms very stable inclusion complexes with simple 4,4'-bipyridinium (viologen) dication guests in aqueous solution. The binding constants were measured by electronic absorption spectroscopy and found to be as high as 1 x 10(5) L/mol. One-electron reduction of the viologen guest results in a modest 2-fold decrease of the binding constant. The rate of the heterogeneous electron-transfer reaction between the complexed viologen dication and cation radical remained fast in the voltammetric time scale.     

Layered Monophosphate Tungsten Bronzes [Ba(PO4)2]WmO3m−3: 2D Metals with Locked Charge-Density-Wave Instabilities

Phosphate tungsten and molybenum bronzes represent an outstanding class of materials displaying textbook examples of charge-density-wave (CDW) physics among other fundamental properties. Here we report on the existence of a novel structural branch with the general formula [Ba(PO₄)₂][W_mO_3m−3] (m=3, 4 and 5) denominated ′layered monophosphate tungsten bronzes′ (L-MPTB). It results from thick [Ba(PO₄)₂]⁴⁻ spacer layers disrupting the cationic metal-oxide 2D units and enforcing an overall trigonal structure. Their symmetries are preserved down to 1.8 K and the compounds show metallic behaviour with no clear anomaly as a function of temperature. However, their electronic structure displays the characteristic Fermi surface of previous bronzes derived from 5d W states with hidden nesting properties. By analogy with previous bronzes, such a Fermi surface should result into CDW order. Evidence of CDW order was only indirectly observed in the low-temperature specific heat, giving an exotic context at the crossover between stable 2D metals and CDW order.     

Permeation of CO2 and N2 through glassy poly(dimethyl phenylene) oxide under steady- and presteady-state conditions

Glassy polymers are often used for gas separations because of their high selectivity. Although the dual-mode permeation model correctly fits their sorption and permeation isotherms, its physical interpretation is disputed, and it does not describe permeation far from steady state, a condition expected when separations involve intermittent renewable energy sources. To develop a more comprehensive permeation model, we combine experiment, molecular dynamics, and multiscale reaction–diffusion modeling to characterize the time-dependent permeation of N₂ and CO₂ through a glassy poly(dimethyl phenylene oxide) membrane, a model system. Simulations of experimental time-dependent permeation data for both gases in the presteady-state and steady-state regimes show that both single- and dual-mode reaction–diffusion models reproduce the experimental observations, and that sorbed gas concentrations lag the external pressure rise. The results point to environment-sensitive diffusion coefficients as a vital characteristic of transport in glassy polymers.