MC1R Gene Polymorphism Affects Skin Color and Phenotypic Features Related to Sun Sensitivity in a Population of French Adult Women

The melanocortin-1 receptor ( MC1R ) gene is known to play a major role in skin and hair pigmentation and to be highly polymorphic in Caucasians. This study was performed to investigate the relationships between MC1R gene polymorphisms and skin color in a large sample of French middle-aged Caucasian women. The codons 60 to 265 and the codon 294 of the MC1R gene were sequenced in 488 women. The skin color was measured on the inner side of the forearm using a spectrophotometric instrument. Fifteen variants were identified: Arg151Cys, Arg160Trp, Arg142His, Asp294His, Ile155Thr, Asp84Glu, Val60Leu, Val92Met, Arg163Gln, Ser83Pro, Thr95Met, Pro256Ser, Val265Ile, Ala166Ala and Gln233Gln. Women carrying Arg151Cys, Asp294His, Arg160Trp and Asp84Glu variants had a significantly higher reflectance in the red region, which indicates a lower level of functional melanin. This association was the most pronounced for women carrying Asp84Glu. In contrast, no significant difference was observed for other variants. Moreover, associations between MC1R polymorphisms and the risks of experiencing sunburn and of having freckles were found independently of skin color. Our findings support the hypothesis that MC1R polymorphisms do not necessarily alter the skin color but should sensitize the skin to UV-induced DNA damage.     

Novel Octahedral Bis[2‐(1‐aziridinyl)ethanol‐κ2N,O] Complexes of Cobalt(II)

The synthesis and molecular structure of trans‐{bis[(acetato‐κO)‐(2‐(1‐aziridinyl)ethanol‐κ²N,O)]}cobalt(II) ( 4 ) and cis‐{bis[chlorido‐(2‐(1‐aziridinyl)ethanol‐κ²N,O)]}cobalt(II) ( 5 ) is reported. Both neutral chelate complexes are prepared from the corresponding Co^II salt [CoX₂; X = OAc ( 1 ), Cl ( 2 )] and 2‐(1‐aziridinyl)ethanol (azolH, 3 ) in dry dichloromethane. A third, ionic complex, cis‐{bis[aqua‐(2‐(1‐aziridinyl)ethanol‐κ²N,O)]}cobalt(II) diacetate ( 6 ) is formed from 4 in the presence of water and could be crystallized from aqueous dichloromethane. In all cases, 2‐(1‐aziridinyl)ethanol is coordinating as bidentate chelate ligand by the nitrogen and oxygen atom of the aziridinyl and hydroxy moiety. After purification, the compounds have been fully characterized using IR spectroscopy and FAB⁺‐MS. The single‐crystal X‐ray structure analysis revealed a distorted octahedral geometry for all complexes with either trans ( 4 ) or cis ( 5 , 6 ) configuration.     

Polyhedral oligomeric silsesquioxane as flame retardant for thermoplastic polyurethane

In this work, the reaction to fire of thermoplastic polyurethane (TPU) containing polyhedral oligomeric silsesquioxanes (or POSSs) was investigated by mass loss calorimetry. This composite exhibits a large reduction of peak of heat release rate (PHRR) compared to virgin TPU. The protection occurs via an intumescent mechanism. Mechanism of protection is examined in chemical and physical ways. Solid state NMR of carbon and silicon on heat-treated materials reveals that there is no significant chemical interaction between TPU and POSS. Nevertheless the intumescent char is characterized as ceramified char made of silicon network in a polyaromatic structure. The expansion occurs because of the partial volatilization of the organic part of POSS and because of the evolving degrading products of TPU. The formation of this intumescent structure makes an efficient insulating material at the surface of the substrate limiting heat and mass transfer and then decreasing heat release rate.     

The extent to which subsets are additively closed

Given a finite abelian group G (written additively), and a subset S of G, the size r(S) of the set may range between 0 and ²|S|, with the extremal values of r(S) corresponding to sum-free subsets and subgroups of G. In this paper, we consider the intermediate values which r(S) may take, particularly in the setting where G is Z/pZ under addition (p prime). We obtain various bounds and results. In the Z/pZ setting, this work may be viewed as a subset generalization of the Cauchy-Davenport Theorem.     

Estimation de la densité dans un espace de dimension infinie : Application aux diffusionsDensity estimation in an infinite dimensional space: Application to diffusion processes

This Note presents a nonparametric density function estimator in an infinite dimensional space. We consider two estimators of the density. Asymptotic results are stated. Finally we give a rate of convergence in the case of a diffusion process's density relative to a Wiener's measure. To cite this article: S. Dabo-Niang, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 213–216.     

Penning ionization electron spectroscopy of molecular adsorbates on Pd and Cu surfaces

The electronic properties of CO, PF₃, NH₃, C₂H₂ and C₆H₆ adsorbed on Pd(111), Pd(110), and Cu(110) surfaces were studied by Auger deexcitation (AD) of metastable noble gas atoms (Penning ionization) and by ultraviolet photoelectron spectroscopy (UPS). Electron emission via AD is restricted to the outmost levels localized at the adsorbed particles. The AD process competes with reasonance ionization of the metastable atoms, and its probability depends on the geometry of the adsorbed species and on its adsorption sites as well as on coverage. The differences in kinetic energy of electrons emitted by AD or by photons reflect modifications of the electron affinities of the adsorbed molecules. The extreme surface sensitivity of AD spectroscopy allows in particular to probe the local density of states at the adsorbate in the energy range close to the Fermi level which arises from π “back donation” as well as σ antibonding contributions.     

Low temperature formation of benzene from acetylene on a Pd(111) surface

Experiments with UPS, metastable noble gas deexcitation spectroscopy (MDS) and thermal desorption demonstrated that C₂H₂ adsorbed on Pd(111) at 140 K undergoes cyclotrimerisation to C₆H₆ after higher (? 100 L) exposures. If the surface is intermediately warmed up to 300 K, the low temperature state of adsorbed acetylene transforms irreversibly into another species which is unreactive. The surface species formed by reaction was identified by comparison with the electron spectroscopic data of C₆H₆ adsorbed from the gas phase as well as with those of free C₆H₆. The molecules are only weaky held on the surface and start to desorb already at about 150 K.     

Reactive scattering of H and D atoms. II. isotope effect on the angular distribution of H,D + NO2

The chemical reactions of hydrogen and deuterium atoms with nitrogendioxide (NO₂) have been studied with crossed molecular beams. Angular and velocity distributions have been measured. The angular distribution peaks at small angles and shows a pronounced isotope effect; only 2̃4% of the available energy goes into translation. Al-though four very deep potential wells (2.1 eV) exist in the potential hypersurface no statistical complex is formed. The reaction can probably be described as intermediate between direct and complex scattering.