New homochiral binaphthol-modified organolanthanide reagents for the enantioselective addition to aldehydes

Optically active secondary alcohols were obtained in high chemical yield and optical purity (up to 85% ee) from the lanthanide-mediated enantioselective addition of alkyl nucleophiles to aromatic aldehydes.     

Concentration at a radius for Hardy class functions

In this paper we establish the fundamental properties of concentration at a radius for functions in the classical Hardy space on the unit disk. For f(z) which is not identically zero and given r, 0<r<1, the concentration is defined via the ratio of the norm of f(rz) to the norm of f(z). Using the Mahler measure of f(z), we obtain information on the distribution of the zeros of f(z) in terms of the concentration ratio. In the last section of the paper, we examine the sharpness of concentration estimates for the Blaschke factor.     

Nanopowder Characterization: Challenges and Future Directions

This article summarizes the conclusions of a workshop organized at the National Institute of Standards and nobreak Technology (NIST), Gaithersburg, October 4–5, 2001. The workshop was focused on the strengths and limitations of the techniques currently used for creating stable dispersions of nanoparticles and measuring the size distribution of powders in the nanosize range. Several emerging and alternative techniques with potential for use in particle size measurement in the nanometer range were advanced. Future needs for procedural and instrumental techniques and standards were identified.     

Accurate vocal compensation for sound intensity loss with increasing distance in natural environments

Human abilities to adjust vocal output to compensate for intensity losses due to sound propagation over distance were investigated. Ten normally hearing adult participants were able to compensate for propagation losses ranging from -1.8 to -6.4 dBdoubling source distance over a range of distances from 1 to 8 m. The compensation was performed to within 1.2 dB of accuracy on average across all participants, distances, and propagation loss conditions with no practice or explicit training. These results suggest that natural vocal communication processes of humans may incorporate tacit knowledge of physical sound propagation properties more sophisticated than previously supposed.     

Onset of quark-hadron duality in pion electroproduction

A large data set of charged-pion (pi+/-) electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark-->pion production mechanisms.     

Access to Nitriles from Aldehydes Mediated by an Oxoammonium Salt

A scalable, high yielding, rapid route to access an array of nitriles from aldehydes mediated by an oxoammonium salt (4‐acetylamino‐2,2,6,6‐tetramethylpiperidine‐1‐oxoammonium tetrafluoroborate) and hexamethyldisilazane (HMDS) as an ammonia surrogate has been developed. The reaction likely involves two distinct chemical transformations: reversible silyl‐imine formation between HMDS and an aldehyde, followed by oxidation mediated by the oxoammonium salt and desilylation to furnish a nitrile. The spent oxidant can be easily recovered and used to regenerate the oxoammonium salt oxidant.