Subject-specific computer simulation model for determining elbow loading in one-handed tennis backhand groundstrokes

A subject-specific angle-driven computer model of a tennis player, combined with a forward dynamics, equipment-specific computer model of tennis ball-racket impacts, was developed to determine the effect of ball-racket impacts on loading at the elbow for one-handed backhand groundstrokes. Matching subject-specific computer simulations of a typical topspin/slice one-handed backhand groundstroke performed by an elite tennis player were done with root mean square differences between performance and matching simulations of < 0.5 degrees over a 50 ms period starting from ball impact. Simulation results suggest that for similar ball-racket impact conditions, the difference in elbow loading for a topspin and slice one-handed backhand groundstroke is relatively small. In this study, the relatively small differences in elbow loading may be due to comparable angle-time histories at the wrist and elbow joints with the major kinematic differences occurring at the shoulder. Using a subject-specific angle-driven computer model combined with a forward dynamics, equipment-specific computer model of tennis ball-racket impacts allows peak internal loading, net impulse, and shock due to ball-racket impact to be calculated which would not otherwise be possible without impractical invasive techniques. This study provides a basis for further investigation of the factors that may increase elbow loading during tennis strokes.     

Amplitude-modulated sinusoidal microchannels for observing adaptability in C. elegans locomotion

In this paper, we present a movement-based assay to observe adaptability in Caenorhabditis elegans locomotion behavior. The assay comprises a series of sinusoidal microchannels with a fixed wavelength and modulating (increasing or decreasing) amplitude. The channel width is comparable to the body diameter of the organism. Worms are allowed to enter the channel from the input port and migrate toward the output port. Within channel sections that closely match the worm's natural undulations, the worm movement is relatively quick and steady. As the channel amplitude increases or decreases along the device, the worm faces difficulty in generating the propulsive thrust, begins to slow down and eventually fails to move forward. A set of locomotion parameters (i.e., average forward velocity, number and duration of stops, range of contact angle, and cut-off region) is defined for worm locomotion in modulated sinusoidal channels and extracted from the recorded videos. The device is tested on wild-type C. elegans (N2) and two mutants (lev-8 and unc-38). We anticipate this passive, movement-based assay can be used to screen nematodes showing difference in locomotion phenotype.     

Higher prevalence of childhood sexual abuse among Latino men who have sex with men than non-Latino men who have sex with men: data from the Urban Men's Health Study

OBJECTIVE: The prevalence of childhood sexual abuse among Latino adult men who have sex with men who live in the US was estimated because a history of childhood sexual abuse increases HIV sexual risk behaviors and other negative health outcomes in adulthood. METHOD: The Urban Men's Health Study is a random-digit telephone probability survey of 2881 adult men who have sex with men (MSM) aged 18 years or older residing in San Francisco, New York, Los Angeles, and Chicago. Self-reported history of childhood sexual abuse was the main outcome measure gathered from 2692 MSM. RESULTS: A significantly higher proportion of Latino MSM reported sexual abuse before age 13 (22%) than did non-Latino MSM (11%). CONCLUSIONS: Latino MSM are twice as likely to report a history of childhood sexual abuse than are non-Latino MSM. Given the association between childhood sexual abuse and increased risk for HIV and other negative health outcomes, health providers must remain vigilant to the possibility of childhood sexual abuse histories among their Latino patients.     

Intra-task variability of trunk coordination during a rate-controlled bipedal dance jump

In this study, we investigated trunk coordination during rate-controlled bipedal vertical dance jumps. The aims of the study were to investigate the pattern of coordination and the magnitude of coordination variability within jump phases and relative to phase-defining events during the jump. Lumbar and thoracic kinematics were collected from seven dancers during a series of jumps at 95 beats per minute. The vector coding technique was used to quantify the pattern and variability of trunk coordination. Coordination was predominantly anti-phase during propulsion and landing. Mean coordination variability peaked just before the landing phase and at the transition from landing to propulsion phases, and was lowest during the propulsion phase just before toe-off. The results indicate that peaks in variability could be explained by task and phase-specific biomechanical demands.     

Home birth: the wave of the future?

A childbirth educator expresses frustration with a medical system that does not work for women or for many maternity care providers. She suggests out-of-hospital birth as an alternative. This column explores the safety of home birth, women's experiences of home birth, and the issues related to home birth once again being the standard. Childbirth educators are encouraged to present home birth as a viable choice.     

A ramble through the cell: how can we clear such a complicated trail?

The arrangement of course information in a logical sequence for molecular life science (MLS) courses remains a matter of some controversy, even within a single subdiscipline such as biochemistry. This is due to the explosion of knowledge, the latest bioinformatic revelations, and the observation that new discoveries sometimes reveal specific connections between previously disparate topics. However, the general outlines of biomedical information are in place, at least the knowledge that should be conveyed to undergraduates taking cell and molecular biology and biochemistry. Despite the increasing amount and complexity of the information to be presented, integration and unification are possible because the molecular reactions and interactions that underlie all life processes are coming into view: they are common to all cellular structural rearrangements, nucleic acid functions, and biochemical reactions, whether of plant or animal origin. Also, it is no longer possible to draw clear boundaries between cell biology, biochemistry, and molecular biology that would not violate the fundamental unity of our understanding. Therefore, an arrangement of content is proposed for a two-semester course that aims to present a unified portrait of upper-division undergraduate MLS.