Global properties of invariant measures

We study global regularity properties of invariant measures associated with second order differential operators in R^N. Under suitable conditions, we prove global boundedness of the density, Sobolev regularity, a Harnack inequality and pointwise upper and lower bounds.     

Radical Reactions in an X-Irradiated Phosphaalkene: A single-crystal ESR study

Single crystals of 1-[2,4,6-tri(tert-butyl)phenyl]-2-phenylphosphaethene ( PPPE ) and of ²D- and ¹³C-enriched PPPE were studied by ESR after X-ray irradiation. Two phosphorus-centered radicals were trapped in the crystals. The first one was characterized by its ³¹P, ¹H-, and ¹³C-hyperfine tensors, the second one exhibited coupling with ³¹P only. Comparison of these parameters with those predicted by ab initio calculations on some phosphinyl species indicates that these two radicals probably result, on the one hand, from an addition of a H-atom to the C-atom of the P?C bond and, on the other, from a cyclization of the parent molecule. The proposed mechanisms are consistent with the mutual orientations of the hyperfine eigenvectors and bond directions in the undamaged molecule. A C-centered radical which results from an addition of a H-atom to the P-atom of the phosphaethylene bond is also detected.     

Crystal structure of mixed rubidium–ammonium hydrogen sulfate Rb0.7(NH4)0.3HSO4 at room temperature

The structure of Rb_0.7(NH₄)_0.3HSO₄ has been determined by X-ray analysis. The mixed compound crystallizes in the monoclinic space group P2₁/n with unit cell parameters a = 14.374(6) Å, b = 4.618(6) Å, c = 14.412(2) Å, = 118.03(2)°, V = 844.4(4) ų, and D _cal = 1.536 g cm^–3 for Z = 8. The mixed compound Rb_0.7(NH₄)_0.3HSO₄ is a chain-based structure. The Rb⁺ and NH₄ ⁺ cations are intercalated between chains, formed of HSO₄ ^- groups linked with OHO hydrogen-bonding. Rb_0.7(NH₄)_0.3HSO₄ presents a new type of structural arrangement different from those of pure RbHSO₄ and NH₄HSO₄.     

NH<Subscript>3</Subscript>(CH<Subscript>2</Subscript>)<Subscript>5</Subscript>NH<Subscript>3</Subscript>BiCl<Subscript>5</Subscript>: an efficient and recyclable catalyst for the synthesis of benzoxazole,benzimidazole and benzothiazole heterocycles

In this work, the condensation of aromatic aldehydes with different two-substituted aniline catalyzed by NH₃(CH₂)₅NH₃BiCl₅ as heterogeneous and recyclable catalyst was reported. It was demonstrated that NH₃(CH₂)₅NH₃BiCl₅ can act as an efficient and active catalyst and is reusable for six runs without a significant loss of their catalytic activity. Simple preparation of the catalyst, high catalytic activity and good reusability are noteworthy advantages of this catalytic system in the synthesis of benzoxazole, benzimidazole and benzothiazole heterocycles at room temperature under solvent-free conditions.     

The role of nonbonded sulfur-oxygen interaction in the dissociative electron transfer to nitro-substituted arenesulfenyl chlorides

The electrochemical reduction of p-nitrophenyl sulfenyl chloride, o-nitrophenyl sulfenyl chloride as well as bis(4-nitrophenyl) disulfide and bis(2-dinitrophenyl) disulfide was investigated in acetonitrile at an inert electrode. Reduction standard potentials as well standard heterogeneous electron-transfer rate constants have been determined using convolution analysis. An unexpected big difference in the thermodynamics and kinetics of the initial electron-transfer process as well as a striking change in the reductive cleavage mechanism of the S-Cl bond as a function of the nitro group position on the aryl ring of the aryl sulfenyl chloride is observed. A computational study at the B3LYP level shows that this difference in behavior is due to the through-space nonbonded S...O interaction in the o-nitrophenyl sulfenyl chloride.     

A model for gas–liquid slug flow in downwardly inclined ductsUn modèle pour les écoulements gaz–liquide à bouchons en conduite inclinée

A simple theoretical model is proposed in order to represent gas–liquid slug flows in inclined ducts of arbitrary shape. To cite this article: A. Dyment, A. Boudlal, C. R. Mecanique 332 (2004).     

Discovery and preliminary SAR of 5-arylidene-2,2-dimethyl-1,3-dioxane- 4,6-diones as platelet aggregation inhibitors

We herein document the discovery of 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones as a novel family of platelet aggregation inhibitors. The preliminary optimization study enabled us to establish the most salient features of the structure-activity relationships in this series as well as to identify novel derivatives that are upto 60 times more potent than the hit structure 1 and slightly superior to the reference drug Milrinone.     

Two new alkaloids from Narcissus serotinus L

The Amaryllidaceae family is well known for the presence of an exclusive group of alkaloids with a wide range of biological activities. Narcissus serotinus L. is a plant belonging to this family and its geographical distribution is mainly located along the Mediterranean coast. In the present work, specimens collected near Casablanca (Morocco) were used to study the alkaloid content of this species. Starting with 350 g of the whole plant we used standard extraction and purification procedures to obtain fractions and compounds for GC-MS and NMR analysis. As well as five known alkaloids, we isolated two new compounds: 1-O-(3′-acetoxybutanoyl)lycorine and narseronine. The latter has been previously published, but with an erroneous structure.     

Physical structure of standing-up aromatic SAMs revealed by scanning tunneling microscopy

Long-range-ordered aromatic SAMs are formed on Au(111) using 4-nitrophenyl sulfenyl chloride as a precursor. Although the main structure is a √3 × √3 with a molecular density similar to that usually found for aliphatic SAMs, particular spots presenting specific shapes are also observed by STM. These include hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules. These molecular arrangements are reversible as they form and dissociate or "vanish" in various areas on the surface. STM shows that these particular structures provide some order to their surrounding because areas void of these structures look less ordered. More interestingly, STM shows submolecular details of the molecules involved in forming these structures, hence providing direct experimental evidence for the ability of the STM to provide physical structure information of standing up SAMs. This is indeed a heavily debated question, and this work reports the first experimental example where submolecular physical structure is revealed by STM for standing-up SAMs.