Asymptotic normality and efficiency of the maximum likelihood estimator for the parameter of a ballistic random walk in a random environment

We consider a one-dimensional ballistic random walk evolving in a parametric independent and identically distributed random environment. We study the asymptotic properties of the maximum likelihood estimator of the parameter based on a single observation of the path till the time it reaches a distant site. We prove asymptotic normality for this consistent estimator as the distant site tends to infinity and establish that it achieves the Cramér-Rao bound. We also explore in a simulation setting the numerical behavior of asymptotic confidence regions for the parameter value.     

Conformal dimension and canonical splittings of hyperbolic groups

We prove a general criterion for a metric space to have conformal dimension one. The conditions are stated in terms of the existence of enough local cut points in the space. We then apply this criterion to the boundaries of hyperbolic groups and show an interesting relationship between conformal dimension and some canonical splittings of the group.     

Restricted rotations and stereodynamics of aziridine-2-methanol derivatives

‘Gear-like’ rotations of simple C-C bonds have been observed in some aziridine methanol derivatives. These restricted rotations have been studied by dynamic and multinuclear magnetic resonance experiments, and the barrier for rotations of Csp³-Csp³ and Csp³-Csp² bonds have been calculated. The role of an intramolecular hydrogen bond on the stereodynamics has also been demonstrated.     

Pt-Cu / ZSM-5 for removal of nitrates from drinking water

Removal of nitrates from drinking water by catalytic hydrogenation over ZSM-5 supported Pt-Cu catalysts was studied. Bimetallics Pt-Cu were prepared by ion exchange of copper on a parent monometallic platinum catalyst. Monometallic platinum catalysts are inactive for nitrate reduction, while Pt-Cu bimetallic catalysts are active for nitrate removal. In the bimetallic catalyst, the role of copper is probably to reduce nitrate according to a redox reaction. The addition of copper to Pt catalysts decreases the production of ammonium ions     

Recent Emission Channeling Studies in Wide Band Gap Semiconductors

We present results of recent emission channeling experiments on the lattice location of implanted Fe and rare earths in wurtzite GaN and ZnO. In both cases the majority of implanted atoms are found on substitutional cation sites. The root mean square displacements from the ideal substitutional Ga and Zn sites are given and the stability of the Fe and rare earth lattice location against thermal annealing is discussed.     

Michael additions catalyzed by phosphines. An overlooked synthetic method

Triphenylphosphine and tributylphosphine are excellent catalysts for Michael additions. Many β-dicarbonyl compounds and electron-poor olefins, including sterically demanding partners, react successfully. The Michael addition catalyzed by phosphines deserves attention in its own right as a useful synthetic method.     

A new synthesis of flavonoids via Heck reaction

Several naturally occurring flavonoids have been synthesised following a new proposed method based on the use of the Heck reaction. The key step involves the coupling of an aryl vinyl ketone with an aryl iodide. This procedure affords the flavonoid moiety in a single step.