RESUMEN
North American bison (Bovidae: Bison bison) incur blunt impacts to the interparietal and frontal bones when they engage in head-to-head fights. To investigate the impact mitigation of these bones, a finite element analysis (FEA) of the skull under loading conditions was performed. Based on anatomical and histological studies, the interparietal and frontal bones are both comprised of a combination of haversian and plexiform bone and are both underlain by bony septa. Additionally, the interparietal bone is thicker than the frontal bone. Data regarding the mechanical properties of bison bone are scarce, but the results of a phylogenetic analysis infer that the material properties of the closely related domestic cow bone are a suitable proxy for use in the FEA. Results of the FEA suggest that the thickness of the interparietal bone in conjunction with the bony septa may prevent fracture stresses by helping to absorb and disperse the blunt impact energy throughout the skull. Monotonic stress levels of 294â MPa, which are below the compressive strength of bone were exhibited in the simulated bison head impacts indicating no fracture of the bones.
Asunto(s)
Bison , Cráneo , Animales , Bison/fisiología , Cráneo/anatomía & histología , Análisis de Elementos Finitos , Fenómenos Biomecánicos , Modelos Teóricos , Filogenia , Estrés MecánicoAsunto(s)
Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/secundario , Continuidad de la Atención al Paciente , Servicio de Urgencia en Hospital/estadística & datos numéricos , Neoplasias Hepáticas/tratamiento farmacológico , Neoplasias Hepáticas/patología , Sistemas de Registros Médicos Computarizados , Adulto , Humanos , Imagen por Resonancia Magnética , Masculino , Reino UnidoRESUMEN
Native English speakers were trained to identify Japanese vowel length in three types of training differing in sentential speaking rate: slow-only, fast-only, and slow-fast. Following Pisoni and Lively's high phonetic variability hypothesis [Pisoni, D. B., and Lively, S. E., Speech Perception and Linguistic Experience, 433-459 (1995)], higher stimulus variability by means of training with two rates was hypothesized to aid learners in adapting to speech rate variation more effectively than training with only one rate. Trained participants identified the length of the second vowel of disyllables, short or long, embedded in a sentence of the respective rate, and received immediate feedback. The three trained groups' abilities before and after training were examined with tests containing sentences of slow, normal, and fast rates, and were compared with those of a control that was not trained. A robust effect of slow-fast training, a marginal effect of slow-only training, but no significant effect of fast-only training were found in the overall test scores. Slow-fast and slow-only training showed small advantages over fast-only training on the fast-rate test scores, while effects for all three training types were found on the slow- and normal-rate test scores. The degree to which the results support the high phonetic variability hypothesis is discussed.