Foods and weights of the Rock Ptarmigan on Amchitka, Aleutian Islands, Alaska

We examined the crop contents from 129 Rock Ptarmigan ( Lagopus mutus ) collected between 1967 and1971 on Amchitka, Aleutian Islands, Alaska. On a yearly basis two plant species, Empetrum nigrum and Equisetum arvense , made up 87% of the diet. Only in July and August were they less than 90% of the diet, and in those months they constituted 65% of the diet. During the warmer months (May-October) when a variety of plant species were available, the Amchitka ptarmigan fed upon growth forms of plants high in nutritive value (particularly Equisetum strobili ). Its main winter food was the vegetative portions of Empetrum , one of the few abundant evergreen vascular plants on the island.     

A common sex-dependent mutation in a RET enhancer underlies Hirschsprung disease risk

The identification of common variants that contribute to the genesis of human inherited disorders remains a significant challenge. Hirschsprung disease (HSCR) is a multifactorial, non-mendelian disorder in which rare high-penetrance coding sequence mutations in the receptor tyrosine kinase RET contribute to risk in combination with mutations at other genes. We have used family-based association studies to identify a disease interval, and integrated this with comparative and functional genomic analysis to prioritize conserved and functional elements within which mutations can be sought. We now show that a common non-coding RET variant within a conserved enhancer-like sequence in intron 1 is significantly associated with HSCR susceptibility and makes a 20-fold greater contribution to risk than rare alleles do. This mutation reduces in vitro enhancer activity markedly, has low penetrance, has different genetic effects in males and females, and explains several features of the complex inheritance pattern of HSCR. Thus, common low-penetrance variants, identified by association studies, can underlie both common and rare diseases.     

管状曲面的奇点

研究管状曲面和它的平行曲面的奇点问题.所谓管状曲面,是沿着E3里一条曲线的双参数空间运动产生的.选定曲线的Frenet向量T作为旋转轴,用不同的方法得到了运动管状曲面的特征.然后,给出管状曲面奇点的一些定理和结果.