Randall D. Kamien Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 We present an alternative local definition of the writhe of a self-avoiding closed loop which differs from the traditional non-local definition by an integer. When studying dynamics this difference is immaterial. We employ a formula due to Aldinger, Klapper and Tabor for the change in writh...

Motivated by recent experiments on DNA torsion-force-extension characteristics we consider the writhing geometry of open stiff molecules. We exhibit a cyclic motion which allows arbitrarily large twisting of the end of a molecule via an activated process. This process is suppressed for forces larger than femto-Newtons which allows us to show that experiments are sensitive to a generalization of...

(3) first described a syndrome, commonly referred to as "writhing", which was induced in rodents by the intraperitoneal injection of various chemical agents. Collier et al. (4) have recently reported experiments on the abilities of various sub stances, including some occurring in tissues and causing pain in man, to induce abdominal construction in mice. Many investigators have described the non...

Antinociceptive actions and effects of intracerebroventricular (i.c.v.) dynorphin-(1-13) (DYN) on morphine (MOR) analgesia and acute tolerance were studied in male Sprague-Dawley rats. Antinociceptive effect against hind paw pressure was produced by 30 micrograms of DYN, but not by 0.5-10 micrograms. Acetic acid writhing was inhibited dose-dependently by DYN at the doses of 2-30 micrograms, and...