The relation between the concentration of testosterone in seminal plasma and certain indicators of reproduction in roosters

Testosterone concentrations in the semen plasma of the cocks of the laying type were analyzed. The levels in semen plasma were substantially lower than in peripheral blood and were found at the interval of 1.58 to 13.30 nmol . 1(-1), the average values amounted to 5.5 nmol . 1(-1). At the repeated samplings of the same animals, considerable variability of hormone levels was observed, which suggested a possibility of the pulsation character of the changes in the androgen also in this biological material. The correlation coefficients between the testosterone levels in semen plasma and ejaculate volume, as well as between the sperm concentration were positive, however, statistically insignificant. The relation between testosterone and the weight of testes was at the significance limit.     

Defusing the childhood vocabulary explosion

During the second year of life, the rate at which children acquire new words accelerates dramatically. This has led the field of language acquisition to posit specialized mechanisms that leverage the few words learned in the initial slow phase for faster vocabulary growth later. Simulations and mathematical analysis demonstrate that specialized cognitive changes are unnecessary. The acceleration in lexical acquisition is a necessary by-product of learning if (i) multiple words are learned in parallel and (ii) words are distributed such that there are few words that can be acquired quickly and many difficult ones.     

中国成为美国进口木地板的主要来源

近年来中国已经成为美国木地板市场的主要供应商。美国从中国进口木地板的总量(包括硬木地板,软木地板和镶木地板)从1998年不足600万美元到2003年增加超过4100万美元．仅2004年上半年进口量就增加到3700万美元．比2003年上半年增加141％。