Strained silacycles in organic synthesis: the tandem aldol-allylation reaction

Allyl(crotyl)enolsilanes, when constrained in a five-membered ring with a 1,2-diol, react with aldehydes in a tandem aldol-allylation reaction to give polyketide fragments. These experimentally trivial and efficient reactions establish two new carbon-carbon bonds and up to four new stereocenters. The silane reagents, which owe their reactivity to strain release Lewis acidity, are easily prepared and stable to storage.     

铁电阴极相对论行波管初步研究

 研究了铁电材料的电子发射特性,根据实验和数值模拟结果给出了铁电发射特性的定性解释,并指出目前的几种铁电发射理论都不足以完备地解释各种实验现象。设计了Pierce型铁电阴极电子枪,实现了束流的二级压缩,其总束流大于100 A。在此基础上,分析和设计了具有盘荷波导慢波结构的相对论行波管,得到了带宽500 MHz,增益约25 dB的X波段行波放大输出。     

Some aspects of single-grain luminescence dating

Single-grain methods of luminescence dating have been developed in order to circumvent problems of variability among aliquots of the sample being dated. Sufficient single grains must be separated in order to make an appropriate interpretation of the variability among such grains. We describe an automated apparatus for sorting grains for routine age determinations by green light stimulation. The sorted grains are then available for study of their collective luminescence physics characteristics. Examples are given of statistical frequency functions of grain brightness obtained with the apparatus and their interpretation. These frequency functions are lognormal or similar, covering up to four orders of magnitude, with consequent implications for luminescence dating application.     

Appendix addendum to ‘Congruence Normality’ of Alan Day

This work was partially supported by NSF Grant 87-03540.     

Small non-Arguesian lattices

Presented by R. McKenzie.