Heavy-ion reactions at forward angles with CMS (LHC)

Reactions seen only in cosmic rays will be studied by three forward angle, θ<5.7° (|η|>3), detectors at CMS. These detectors look at ?erenkov radiation from quartz fibers embedded in a heavy-metal matrix to deal with the exceptionally large particle fluxes.     

Tetragonal SrTiO3 revisited: The effect of impurities on the Raman spectrum

We report an exhaustive study of the tetragonal phase of SrTiO₃ by Raman scattering. This work is compared with the results of neutron inelastic scattering, infrared, and electric field induced Raman scattering experiments to give a coherent picture of the zone centre phonon frequencies. The results of Raman scattering from isomorphous compounds confirm this picture.     

On the asymptotic power of some k-sample statistics based on the multivariate empirical process

Some k-sample Kolmogorov-Smirnov and Cramér-von Mises-type statistics, based on the multivariate empirical process, are studied. Expressions for their asymptotic power are obtained against various classes of alternative distribution functions.     

Correlations between electron and positron workfunctions on copper surfaces

We have performed contact potential difference measurements on low-index faces of copper in ultrahigh vacuum using positrons as positive test particles in a retarding field analyzer. For negative positron affinity surfaces bombarded with keV positrons we also measured energy distributions of reemitted slow positrons and found them to sharply peaked in energy about a value which we label ?φ⁺. Both adsorbing sulfur on a Cu(111) sample and raising its temperature cause changes in φ⁺ which are equal and opposite to the contact potential change of the sample, i.e. the electron workfunction change. This result is in complete accordance with φ⁺ being a measure of the negative positron workfunction of the sample and high temperature or adsorbates inducing a change only in the electrostatic surface dipole layer.     

The coulomb condensate of the nonlinear Poisson-Boltzmann equation: A unified theory

A general form of the one-dimensional nonlinear Poisson-Boltzmann (PB) equation for a simple electrolyte is studied, namely r^?m(d/dr{r^mdψ^(m)/dr} = sinh ψ^(m), where r and ψ^(m) are dimensionless distance and potential respectively, and m = 2, 1 and 0 correspond to the spherical, cylindrical and planar equations respectively. Since analytic solutions are not available for this general PB equation, its properties are here studied via suitable upper bounds, both relative and absolute, on its solutions. When the final results are specialized to the sphere (m = 2) and cylinder (m = 1) cases, there are recovered the σ-funcfion condensate theorems for a point charge and line charge respectively, previously proven by the author. Since the point-charge and line-charge condensates are hereby shown to have a common origin, it is suggested that they both be called simply “Coulomb condensates”, in recognition of their physical origin.     

Simple n-protecting groups for β-lactam synthesis

Allyl and 2,2-diethoxyethyl groups on β-lactam nitrogen can be removed via the enol acetate to give N-unsubstituted β-lactam under mild conditions.     

Does antiaromaticity imply net destabilization?

An analysis is presented of the results of earlier ab initio computational studies of cyclobutadiene, cyclooctatetraene, and 1,4-dihydropyrazine. The first and third of these are normally categorized as antiaromatic. All three molecules are polyenes, even when the last two are forced into planar conformations. There is no driving force for extensive π delocalization, even when it would appear to have been facilitated. Calculated isodesmic energies show a net destabilization only in the case of cyclobutadiene, which we attribute to strain and repulsion between the π electrons of the C?C double bonds. The other two molecules have negative isodesmic energies, indicative of net stabilizing effects. We conclude that the concept of antiaromaticity is useful for identifying molecules that resist the apparent opportunity for extensive © delocalization, but that it does not intrinsically imply net destabilization. © 1994 John Wiley & Sons, Inc.