On the utility of S-mesitylsulfinimines for the stereoselective synthesis of chiral amines and aziridines

The synthetic utility of S-mesitylsulfinimines for the synthesis of chiral amines and aziridines was examined through their reactions with Grignard reagents, with the ylides derived from trimethylsulfonium iodide and S-allyl-tetrahydrothiophenium bromide and through an aza-Darzens manifold, affording convenient access to a diverse range of highly substituted chiral amines and aziridines in high yields and excellent stereoselectivities.     

High-power, low-threshold BH lasers operating at 1.52 ?m grown entirely by MOVPE

BH laser devices with efficient optical and current confinement have been grown using a new all-MOVPE growth technique. The devices produced operated with CW threshold currents as low as 14 mA and output powers of up to 28 mW at 20°C. In initial experiments, over 70% of the working devices tested had threshold currents of less than 30 mA, substantiating the view that MOVPE is a highly promising technique for the large-scale production of complex optoelectronic devices.     

High-performance, high-reliability buried heterostructure lasers byMOVPE

The authors report the first highly reliable all-MOVPE BH lasers. These devices have extremely low threshold currents (≃10 mA) and show excellent uniformity of device characteristics. Data are presented to show the high yields achieved and demonstrate the very low degradation rates achieved under accelerated aging     

Glaciers melt as mountains warm: a graphical case study

For the 2006 ASA Data Exposition we created graphics that, in the legacy of John Tukey, tried to “force the unexpected upon us” (Tukey in Proceedings of the 18th conference on design of experiments in Army research and development I, Washington, 1972). The data were geographic and meteorological measurements taken every month for 6 years on a coarse 24 by 24 grid covering Central America. Using conventional static graphics and some less conventional interactive graphics, we were able to find expected features in the data, such as seasonal patterns, spatial correlations, and El Niño events, as well as some more surprising results, several of which were corroborated by stories in the news.     

Irradiation-induced segregation and diffusion of manganese implants in nickel

The effects of radiation-induced solute redistribution and diffusion are studied for 30 keV Mn implants in nickel irradiated with 75 keV Ni⁺ ions at 500°C. The peak of the Mn implant profile is driven to greater depth with increasing irradiation dose until a steady-state solute profile is established. The rate of drift of Mn atoms and their diffusion coefficient is related to the distribution of point-defects in the nickel under irradiation.     

Facile Synthesis of Alkoxyalkyl Cyclopentadienes

Condensation of trimethylsilylcyclopentadiene with acetals, ketals, and some ortho esters in the presence of a catalytic amount of trimethylsilyltrifluoromethanesulfonate offers a new route to sensitive alkoxyalkyl substituted cyclopentadiene compounds.     

New developments in X-ray storage phosphors

We found a significant PSL effect in Eu²⁺-doped fluorozirconate glasses (ZBLAN) which were additionally doped with Br⁻ or Cl⁻ ions. The PSL is attributed to the characteristic emission of Eu²⁺ present in nano-crystallites of BaBr₂ or BaCl₂, which form in the glass upon annealing. The metastable hexagonal form of BaX₂ (X=Br,Cl) is always formed first before it is converted into the stable orthorhombic form. The particle size increases upon annealing and so does the PSL efficiency of the glass ceramic. However, there is a saturation of the PSL efficiency, which is for Br⁻ doping about 9% and for Cl⁻-doping about 80% of the Eu-doped BaFBr standard. The particle size was determined by transmission electron microscopy (TEM). The TEM results show a clear tendency for bigger particles for longer annealing at the expense of its number. The particle size for the most efficient phosphor is about 100 nm.     

Reprocessing of thermally oxidized aluminum arsenide (AlAs) in epitaxial multilayers without delamination

Annealing or processing of AlAs that has been subjected to a wet thermal oxidation process can result in severe delamination of material at the oxidation front. This paper reports a procedure for preventing this delamination and presents a possible cause for the delamination.