Molecular aromaticity in the linear polyacenes is investigated using an atoms in molecules based six center index (SCI-AIM) which measures the electron delocalization. SCI-AIM values for the linear polyacenes indicate decreasing aromaticity going from outer to inner rings in the polyacene series. The SCI-AIM approach is compared to a Mulliken-like approach, and a critical comparison to the PDI index is made.

Study Design:Comparative study of differences in functional control during ankle supination in the standing position in matched stable and unstable ankles (ex post facto design). Objectives: To document acceleration and deceleration during ankle supination in the standing position and to determine differences in control of supination perturbation between stable and unstable ankles. Background: Repetitive ankle sprain can be explained by mechanical instability only in a minority of cases. Exercise therapy for ankle instability is based on clinical experience. Joint stability has not yet been measured in dynamic situations that are similar to the situations leading to a traumatic sprain. The process of motor control during accelerating ankle supination has not been adequately addressed in the literature. Methods and Measures: Pdtients with complaints of ankle instability (16 unstable ankles) and nonimpaired controls (18 stable ankles) were examined (N = 17 subjects, 10 women and 7 men). The average age was 23.7 2 5.0 years (range, 20-41 y). Control of supination speed was studied during 50" of ankle supination in the standing position using accelerometry (total supination time and deceleration times) and electromyography (latency time). Timing of motor response was estimated by measuring electromechanical delay. Results: The presence of an early, sudden, and presumably passive slowdown of ankle supination in the standing position was observed. Peroneal muscle motor response was detected before the end of the supination. Unstable ankles showed significantly shorter total supination time (109.3 ms versus 124.1 ms) and significantly longer latency time (58.9 ms versus 47.7 ms). Conclusions: Functional control in unstable ankles is less efficient in decelerating the ankle during the supination test procedures used in our study. Our conclusions are based on significantly faster total supination and significantly slower electromyogram response in unstable ankles. The results support the hypothesis that both decelerating the total supination movement during balance disturbance and enhancing the speed of evertor activation through exercise can be specific therapy goals. I Orthop Sports Phys J%er ,?OOl;3l:74l-752.