Retrieving parameters of the anisotropic refractive index fluctuations spectrum in the stratosphere from balloon-borne observations of stellar scintillation

Scintillation effects are not negligible in the stratosphere. We present a model based on a 3D model of anisotropic and isotropic refractive index fluctuations spectra that predicts scintillation rates within the so-called small perturbation approximation. Atmospheric observations of stellar scintillation made from the AMON-RA (AMON, Absorption par les Minoritaires Ozone et NO(x); RA, rapid) balloon-borne spectrometer allows us to remotely probe wave-turbulence characteristics in the stratosphere. Data reduction from these observations brings out values of the inner scale of the anisotropic spectrum. We find metric values of the inner scale that are compatible with space-based measurements. We find a major contribution of the anisotropic spectrum relative to the isotropic contribution. When the sight line plunges into the atmosphere, strong scintillation occurs as well as coupled chromatic refraction effects.     

Co-tunneling enhancement of the electrical response of nanoparticle networks

A co-tunneling charge-transfer process dominates the electrical properties of a nanometer-sized "slice" in a nanoparticle network, which results in universal scaling of the conductance with temperature and bias voltage, as well as enhanced spintronics properties. By designing two large (10 μm) electrodes with short (60 nm) separation, access is obtained to transport dominated by charge transfer involving "nanoslices" made of three nanoparticles only. Magnetic iron oxide nanoparticle networks exhibit a magnetoresistance ratio that is not reachable by tunneling or hopping processes, thereby illustrating how such a size-matched planar device with dominant co-tunneling charge-transfer process is optimal for realizing multifunctional devices with enhanced change of conductance under external stimulus.     

Numerical Implementation and Application of an Extended Model for Diffusion and Precipitation of Chemical Elements in Metallic Matrices

A model for simultaneous and coupled diffusion and precipitation of chemical elements in metallic matrices is proposed, together with a scheme for its numerical solution and some applications to problems of internal oxidation. This model extends over a previous one of the authors, which itself stood as a generalization of many earlier ones. It includes the possibility that precipitates may be present in large fractions; if so, they may affect diffusion in the matrix phase by acting as “barriers”, and/or by distorting this matrix. The possible re-dissolution of some or all precipitates may also be prohibited for kinetic reasons. A simple but robust numerical scheme based on 1D finite differences in space coupled with explicit integration in time is proposed to solve the equations of the problem. This scheme notably contains an efficient Newton–Raphson algorithm used to solve the laws of mass action. Numerical simulations of internal oxidation processes close to those encountered in actual industrial practice are finally presented. It is first shown that in simple cases, the simulations reproduce Wagner’s classical analytical solution and related ones. More complex cases not amenable to analytic solutions are then envisaged.     

三轴感应电阻率测井新技术

一种新型感应电阻率测井仪器能够提供远离井筒地层的三维信息,提高斜井和倾斜地层的电阻率测量精度,而且不需要接触井壁就能够直接测量地层倾角大小和方位。采用这种高精度三轴电阻率测井仪器可以减少漏掉油气层的机会,加强对储层的认识。     

An improved compact model for CMOS cross-shaped Hall-effect sensor including offset and temperature effects

A compact model of a cross-shaped horizontal integrated Hall-effect sensor is presented in this paper. Compared to existing models, reliability is improved, especially to simulate systems in which biasing and measurement circuits are not independent. The Hall device model core, already published, is based on a network of six non-linear resistances and four Hall voltage sources, and includes only 11 physical parameters. In this paper, in order to improve model predictivity, four additional parameters have been added to take the offset issue into account. In addition, variations of parameters with temperature are also addressed. The model is implemented in Verilog-A and has been validated through experiments carried out on Hall devices designed in a CMOS 0.35??m technology. The parameters extraction procedure is detailed and the maximum error between simulations and experimental data is less than 1?% for a wide range of biasing currents and temperatures.     

Endothelial Colony-Forming Cells Dysfunctions Are Associated with Arterial Hypertension in a Rat Model of Intrauterine Growth Restriction

Infants born after intrauterine growth restriction (IUGR) are at risk of developing arterial hypertension at adulthood. The endothelium plays a major role in the pathogenesis of hypertension. Endothelial colony-forming cells (ECFCs), critical circulating components of the endothelium, are involved in vasculo-and angiogenesis and in endothelium repair. We previously described impaired functionality of ECFCs in cord blood of low-birth-weight newborns. However, whether early ECFC alterations persist thereafter and could be associated with hypertension in individuals born after IUGR remains unknown. A rat model of IUGR was induced by a maternal low-protein diet during gestation versus a control (CTRL) diet. In six-month-old offspring, only IUGR males have increased systolic blood pressure (tail-cuff plethysmography) and microvascular rarefaction (immunofluorescence). ECFCs isolated from bone marrow of IUGR versus CTRL males displayed a decreased proportion of CD31+ versus CD146+ staining on CD45− cells, CD34 expression (flow cytometry, immunofluorescence), reduced proliferation (BrdU incorporation), and an impaired capacity to form capillary-like structures (Matrigel test), associated with an impaired angiogenic profile (immunofluorescence). These dysfunctions were associated with oxidative stress (increased superoxide anion levels (fluorescent dye), decreased superoxide dismutase protein expression, increased DNA damage (immunofluorescence), and stress-induced premature senescence (SIPS; increased beta-galactosidase activity, increased p16^INK4a, and decreased sirtuin-1 protein expression). This study demonstrated an impaired functionality of ECFCs at adulthood associated with arterial hypertension in individuals born after IUGR.     

Evolution of the microstructure of unconsolidated geopolymers by thermoporometry

This paper studies the evolution of the pore size distribution of a fresh unconsolidated geopolymer paste between one day and a week, using thermoporometry. This was made possible by following a careful protocol for sample preparation and for analysis by differential scanning calorimetry. In contrast with nitrogen gas adsorption, this method quantifies directly the amount of water in pores. It also does not require heat and vacuum drying, thus maintaining the fragile pore structure of the unconsolidated paste. Moreover, it was found that, in a typical metakaolin-based sodium geopolymer with a 10 to 20 hours workability period, the porosity gradually refines during the first week while the mesoporous volume is cut in half. This is probably due to the fact that the geopolymer network was still actively condensing from the activation solution. Part of the pore water never froze and, from mass balance, this residual water was attributed to the water bound in the hydration shell of the sodium counter ions. Only a minor occurrence of covalently bound protons as silanol groups was observed. The results presented here usefully complement data obtained by conventional techniques at later ages on consolidated geopolymers. It supports the growing body of literature on the structural evolution of geopolymers with time.     

Crack kinking from an initially closed, ordinary or interface crack, in the presence of friction

One theoretically studies crack kinking from an ordinary crack (in some homogeneous solid) or an interface crack (between two dissimilar materials), in the situation where this crack is closed prior to kinking but open after it. This problem was recently considered by the authors with the simplifying, but physically quite unrealistic hypothesis of absence of friction between the crack lips. Their work is extended here to account for possible friction governed by Coulomb’s law. Problems of elastic fracture mechanics with unilateral contact and friction between the crack lips being not only non-linear, but incremental in nature, the theoretical treatment becomes notably more involved than without friction. It is still based, however, on the same basic ingredients, namely “homogeneity” properties of the type of problems considered, changes of scale and some reasonable hypotheses. It is shown that whatever the geometry of the body and the crack and whatever the loading, the asymptotic expression of the stress intensity factors (SIF) at the tip of a vanishingly small kinked crack extension depends solely upon the initial (mode II) SIF prior to kinking, the kink angle, Dundurs’s famous parameters α and β and the friction coefficient. The (history-independent) functions involved in the general formulae established are determined numerically through finite element computations. From there, using Goldstein and Salganik’s famous principle of local symmetry to predict the crack path, one derives a theoretical value for the kink angle. This value depends upon the loading only through the sign of the initial stress intensity factor; it also depends on the mismatch of elastic properties and the friction coefficient. However, its range of variation is numerically found to be rather narrow. Experiments conducted by various authors seem to confirm these theoretical predictions.     

Friable rock embedding in methyl methacrylate for thin-sectioning in geological preparations

In most cases, technical problems prevent the production of good geological thin-slabs from friable rocks such as muds, sands or decomposed granites. Usual impregnation methods using Araldite or epoxies lead to incompletely impregnated blocks. Furthermore the excessive heat occurring during polymerization alters the micromorphology of heat sensitive minerals. Methyl methacrylate (MMA) is a widely used plastic for bone embedding. We have developed a new procedure using vacuum infiltration with MMA in a cold environment. Wafers from friable rocks are easily obtained and can be processed in the same way as those of firm and coherent rocks, without grain loss nor mineral heat alterations.     

Driver–vehicle cooperation: a hierarchical cooperative control architecture for automated driving systems

The concept of automated driving changes the way humans interact with their cars. However, how humans should interact with automated driving systems remains an open question. Cooperation between a driver and an automated driving system—they exert control jointly to facilitate a common driving task for each other—is expected to be a promising interaction paradigm that can address human factors issues caused by driving automation. Nevertheless, the complex nature of automated driving functions makes it very challenging to apply the state-of-the-art frameworks of driver–vehicle cooperation to automated driving systems. To meet this challenge, we propose a hierarchical cooperative control architecture which is derived from the existing architectures of automated driving systems. Throughout this architecture, we discuss how to adapt system functions to realize different forms of cooperation in the framework of driver–vehicle cooperation. We also provide a case study to illustrate the use of this architecture in the design of a cooperative control system for automated driving. By examining the concepts behind this architecture, we highlight that the correspondence between several concepts of planning and control originated from the fields of robotics and automation and the ergonomic frameworks of human cognition and control offers a new opportunity for designing driver–vehicle cooperation.