The molecular origins of second order nonlinear effects in type I collagen fibrils have been identified with sum-frequency generation vibrational spectroscopy. The dominant contributing molecular groups are: i) the methylene groups associated with a Fermi resonance between the fundamental symmetric stretch and the bending overtone of methylene, and ii) the carbonyl and peptide groups associated with the amide I band. The noncentrosymmetrically aligned methylene groups are characterized by a distinctive tilt relative to the axis perpendicular to the main axis of the collagen fiber, a conformationproducing a strong achiral contribution to the second order nonlineareffect. In contrast, the stretching vibration of the carbonyl groups associated with the amide I band results in a strong chiral contribution to the optical second order nonlinear effect. The length scale of these chiral effects ranges from the molecular to the supramolecular.
植物根系研究新技术Minirhizotron起源发展和应用.pdf;全球最著名的《科学》杂志(Science),于今年6月发表了--应用植物根系监测系统BTC-2研究植物根系行为的文章“Plants Integrate Information about Nutrients and Neighbors. ” BTC-2微根窗根系监测系统及BTC-100高倍微根窗根系监测系统由美国Bartz公司研制生产,是目前世界上唯一国际通用的微根窗技术,易科泰生态技术公司为其亚洲地区总代理和技术服务中心