Nanocomposites from Untreated Clay : A Myth ?

Polyamide 6 and pristine montmorillonite have been melt blended in an extruder and water was injected into the melt in order to produce nanocomposites. The pristine clay was found to be exfoliated and dispersed homogenously in the nanocomposites. A mechanism explaining the formation of such nanocomposites is presented.     

Global Continuous Riemann Solver for Nonlinear Elasticity

We consider in this paper an isothermal model of nonlinear elasticity. This model is described by two conservation laws that define a problem of mixed type, both elliptic and hyperbolic. We restrict ourselves to the linearly degenerate case, and consider Riemann data that lies in the hyperbolic regions. The lack of uniqueness of the Riemann problem is solved by the introduction of a so-called kinetic relation, used to narrow the set of admissible subsonic phase transitions. In this situation, we consider the Riemann problem for any data lying in the hyperbolic region, using either explicit computations or geometric arguments. This construction allows us to give sufficient conditions on the kinetic relation in order that the generated Riemann solver possesses properties of uniqueness, globality, and continuous dependence on the initial data in the L ¹ distance. Accepted October 1, 2000?Published online January 22, 2001     

The Pathophysiology of Long COVID throughout the Renin-Angiotensin System

COVID-19 has expanded across the world since its discovery in Wuhan (China) and has had a significant impact on people’s lives and health. Long COVID is a term coined by the World Health Organization (WHO) to describe a variety of persistent symptoms after acute SARS-CoV-2 infection. Long COVID has been demonstrated to affect various SARS-CoV-2-infected persons, independently of the acute disease severity. The symptoms of long COVID, like acute COVID-19, consist in the set of damage to various organs and systems such as the respiratory, cardiovascular, neurological, endocrine, urinary, and immune systems. Fatigue, dyspnea, cardiac abnormalities, cognitive and attention impairments, sleep disturbances, post-traumatic stress disorder, muscle pain, concentration problems, and headache were all reported as symptoms of long COVID. At the molecular level, the renin-angiotensin system (RAS) is heavily involved in the pathogenesis of this illness, much as it is in the acute phase of the viral infection. In this review, we summarize the impact of long COVID on several organs and tissues, with a special focus on the significance of the RAS in the disease pathogenesis. Long COVID risk factors and potential therapy approaches are also explored.     

Full-Atom Model of the Agonist LPS-Bound Toll-like Receptor 4 Dimer in a Membrane Environment

The Toll-like receptor 4 (TLR4)/myeloid differentiation factor 2 (MD-2) innate immunity system is a membrane receptor of paramount importance as therapeutic target. Its assembly, upon binding of Gram-negative bacteria lipopolysaccharide (LPS), and also dependent on the membrane composition, finally triggers the immune response cascade. We have combined ab-initio calculations, molecular docking, all-atom molecular dynamics simulations, and thermodynamics calculations to provide the most realistic and complete 3D models of the active full TLR4 complex embedded into a realistic membrane to date. Our studies give functional and structural insights into the transmembrane domain behavior in different membrane environments, the ectodomain bouncing movement, and the dimerization patterns of the intracellular Toll/Interleukin-1 receptor domain. Our work provides TLR4 models as reasonable 3D structures for the (TLR4/MD-2/LPS)₂ architecture accounting for the active (agonist) state of the TLR4, and pointing to a signal transduction mechanism across cell membrane. These observations unveil relevant molecular aspects involved in the TLR4 innate immune pathways and will promote the discovery of new TLR4 modulators.     

Synthesis of pyranoid δ-sugar amino acids and their oligomers from per-benzylated β-C-vinyl glucoside

Two pyranoid δ-sugar amino acids were prepared from the common per-benzylated β-C-vinyl glucoside and easily oligomerised using solution-phase coupling methodology.     

New progress in the cobalt-catalysed synthesis of aromatic organozinc compounds by reduction of aromatic halides by zinc dust

The experimental conditions of the cobalt-catalysed synthesis of aromatic organozinc species from the corresponding bromides have been optimised. The preparation of numerous aromatic organozinc reagents under these optimised conditions is reported, with yields between 67 and 99%.     

Asymptotic Poisson Character of Extremes in Non-Stationary Gaussian Models

Let X be a non-stationary Gaussian process, asymptotically centered with constant variance. Let u be a positive real. Define R_u(t) as the number of upcrossings of level u by the process X on the interval (0, t]. Under some conditions we prove that the sequence of point processes (R_u)_u>0 converges weakly, after normalization, to a standard Poisson process as u tends to infinity. In consequence of this study we obtain the weak convergence of the normalized supremum to a Gumbel distribution.AMS 2000 Subject Classifications Primary—60G70, 60G15     

An ordinal sorting method for group decision-making

Several group decision-making methods were proposed with the aim to establish, from individual opinions, a collective one. However, the literature review of such methods show that, until now, few of them accept individual preferences expressed in partial pre-orders or, more generally, in preferences relational systems (p.r.s.). In addition, the majority of these methods produce a ranking on the alternative set, i.e. they concern the ranking decision-making problematic. In fact, the efforts provided to develop methods which treat, for example, the sorting problematic, remain insufficient. For these reasons, we propose in this paper an ordinal sorting method which determines, from individual p.r.s., at least one collective assignment which takes into account the relative importance of the members. If there is more than one collective assignment, an interactive procedure to reach a consensus assignment is proposed.     

Numerical simulations of gas-particle flows with combustion

This work is devoted to the numerical modelling of a reactive gas-particle flow that arises in internal ballistic. The model, proposed by Gough [2], takes into account complex physical phenomena such as mass transfer, drag force or intra granular stress. A non-conservative finite volume approach adapted from [11] is applied in order to simulate the model. After an academic validation test case of the scheme, the combustion propagation ignited by a cylindrical perforated primer is then simulated and compared with experiments.