我国淡水红藻两新记录种

本文报道我国淡水红藻的两个新记录种,即弧形串珠藻Batrachospermum arcuatum Kylin emend.Vis et al.和细链珠藻Sirodotia tenuissima(Collins) Skuja ex Flint.标本均采自我国山西省。

Design of apochromatic telescope without anomalous dispersion glasses

A novel lens system with correction of secondary spectrum without using anomalous glasses is presented. The lens system comprises four separated lens components, with three of them being subapertures. Two examples of apochromatic telescope are presented, both with the use of typical normal glasses, namely crown K9 and flint F5 glasses, and low-cost slightly anomalous dispersion glasses. Secondary spectrum and other chromatic aberrations of the two design examples are corrected.