Search results for "Faces"
showing 10 items of 3167 documents
Discovery of new G-quadruplex binding chemotypes
2013
We report here on the discovery and preliminary evaluation of a novel non-macrocyclic low molecular weight quadruplex-stabilizing chemotype. The lead compounds, based on a furan core, show high G-quadruplex stabilisation and selectivity as well as potent in vitro anti-proliferative activity.
Nanoscale Mapping of the Physical Surface Properties of Human Buccal Cells and Changes Induced by Saliva
2019
International audience; The mucosal pellicle, also called salivary pellicle, is a thin biological layer made of salivary and epithelial constituents, lining oral mucosae. It contributes to their protection against microbiological, chemical, or mechanical insults. Pellicle formation depends on the cells’ surface properties, and in turn the pellicle deeply modifies such properties. It has been reported that the expression of the transmembrane mucin MUC1 in oral epithelial cells improves the formation of the mucosal pellicle. Here, we describe an approach combining classical and functionalized tip atomic force microscopy and scanning microwave microscopy to characterize how MUC1 induces change…
Design of enzyme-mediated controlled release systems based on silica mesoporous supports capped with ester-glycol groups
2012
[EN] An ethylene glycol-capped hybrid material for the controlled release of molecules in the presence of esterase enzyme has been prepared. The final organic-inorganic hybrid solid S1 was synthesized by a two-step procedure. In the first step, the pores of an inorganic MCM-41 support (in the form of nanoparticles) were loaded with [Ru(bipy) 3]Cl 2 complex, and then, in the second step, the pore outlets were functionalized with ester glycol moieties that acted as molecular caps. In the absence of an enzyme, release of the complex from aqueous suspensions of S1 at pH 8.0 is inhibited due to the steric hindrance imposed by the bulky ester glycol moieties. Upon addition of esterase enzyme, del…
Electrokinetic Properties which Control the Coagulation of Silicate Cement Suspensions during Early Age Hydration
1998
The coagulation of cement particles during early age hydration has been previously identified as the first step of the setting and hardening of cement pastes. By hydrating Ca3SiO5and a silicate-rich clinker under controlled conditions, a correlation between the coagulation of the suspensions and the electrokinetic properties of particles is established. The zeta potential, and hence the surface charge, of particles in suspension depends on the calcium content of the medium. At low concentrations of Ca2+, the zeta potential of Ca3SiO5particles, calcium silicate hydrate (C–S–H), and clinker is negative (<−30 mV) and the suspensions are well dispersed. A strong coagulation occurs at intermedia…
Surface Relaxivity of Cement Hydrates
2014
Numerous aspects of the physical chemistry of colloidal systems are conditioned by the solid–liquid interface, and this is also the case for hydrated cement systems. Estimating the surface area is thus essential for studying the kinetics of cement hydration and admixture adsorption. Proton nuclear magnetic resonance (NMR) relaxation techniques have already proven useful for this objective, but, for hydrating cements at early ages, it is necessary to know the surface relaxivities of all of the individual phases present to correctly interpret the relaxation data. This paper reports the results of a comparison of NMR relaxometry and Brunauer–Emmett–Teller gas adsorption measurements on various…
Correlation between surface forces and surface reactivity in the setting of plaster by atomic force microscopy
2000
Abstract The setting of mineral binders (cement, plaster, etc.) arises as a direct consequence of surface reactivity by a process of dissociation and rehydration. This transformation induces a complete change of surface forces, of which the nature remains still unknown. The general process of the setting has been studied by means of plaster (CaSO 4 ·0.5H 2 O) crystals, chosen for an experimental convenience. The surface alteration (growth, dissolution, atomic resolution) of the plaster crystal with respect to the introduction of the calcium sulfate solution has been followed by using atomic force microscopy (AFM. Alternatively, this apparatus has been adapted by gluing a plaster microcrysta…
Formation of the C−S−H Layer during Early Hydration of Tricalcium Silicate Grains with Different Sizes
2005
Portland cement is a mixture of solid phases which all react with water. Tricalcium silicate (Ca3SiO5) is its main component and is often used in model systems to study cement hydration. It is generally recognized that setting and hardening of cement are due to the formation, by a dissolution-precipitation process, of a calcium silicate hydrate (C-S-H) on anhydrous grains during Ca3SiO5 hydration. The purpose of this paper is to study the effect of Ca3SiO5 particle size on the nucleation-growth process of C-S-H. An experimental study of the rate of hydration by using different grain sizes under controlled conditions has been performed. The experimental data have been compared with results o…
Intrinsic Acidity of Surface Sites in Calcium Silicate Hydrates and Its Implication to Their Electrokinetic Properties
2014
Calcium Silicate Hydrates (C–S–H) are the major hydration products of portland cement paste. The accurate description of acid–base reactions at the surface of C–S–H particles is essential for both understanding the ion sorption equilibrium in cement and prediction of mechanical properties of the hardened cement paste. Ab initio molecular dynamics simulations at the density functional level of theory were applied to calculate intrinsic acidity constants (pKa’s) of the relevant ≡SiOH and ≡CaOH2 groups on the C–S–H surfaces using a thermodynamic integration technique. Ion sorption equilibrium in C–S–H was modeled applying ab initio calculated pKa’s in titrating Grand Canonical Monte Carlo simu…
Peritumoral Edema in Meningiomas
1994
Although generally benign tumors, meningiomas may be associated with extensive peritumoral brain edema as seen on computed tomographic scans. Fifty-two patients with intracranial meningiomas were studied, and the hypodense areas on computed tomographic scans were related to the intraoperative microsurgical findings and to the sizes of the tumors. We have identified three kinds of tumor-brain interfaces characterized by different difficulties in microsurgical dissection: smooth type, transitional type, and invasive type. These different microsurgical interfaces seem to correlate very precisely with computed tomographic images of halo-like and finger-like hypodense areas, allowing prediction …
XPS study of supported gold catalysts:the role of Au0 and Au+? species as active sites.
2006
Gold nanoparticles supported on different oxides (SiO2, CeO2 and TiO2) were prepared by the SMAD (solvated metal atom dispersion) and deposition–precipitation (DP) techniques. The physical and chemical characterization of the catalysts was performed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the catalytic activity was tested during the reaction of low temperature CO oxidation. The structural and surface analyses evidenced the presence of small gold crystallites (cluster size ∼2–5 nm) in all the SMAD-prepared samples and oxidized gold species in the case of the DP catalysts. A different surface distribution of ionic gold species was found on the different suppo…