A Comparison of Lower Extremity Joint Work and Initial Loading Rates among Four Different Running Styles

The annual injury incidence rate among the 36 million runners in the United States is approximately 50%. The majority of those injuries occur at the knee joint. The purpose of this study was to measure lower extremity eccentric work and average vertical loading rates among four groups of runners. Seventy-four healthy runners volunteered for this study. The four groups of runners consisted of traditional shoe wearing rearfoot strikers (TSR), minimalist shoe wearing anterior footstrikers (MSA), certified Chi runners (Chi), and minimalist shoe wearing rearfoot strikers (MSR). Study variables were ankle dorsiflexion eccentric work (ADEW), ankle plantarflexion eccentric work (APEW), knee extension eccentric work (KEEW), and average vertical ground reaction force loading rates (VALR). Volunteers ran for five minutes at a self-selected speed on a Bertec instrumented treadmill with Vicon Nexus 3D motion capture. Eccentric joint work was obtained by integrating the negative portion of the joint power curves. VALR was defined as the slope of the vertical ground reaction force curve. TSR runners demonstrated greater ADEW, greater KEEW, and greater VALR than anterior footstriking runners. MSA runners demonstrated the greatest APEW with reduced ADEW, reduced VALR, and reduced KEEW compared to TSR runners. Chi runners demonstrated the least VALR, no ADEW, no significant additional APEW, and reduced KEEW compared to TSR runners. MSR runners demonstrated the greatest and potentially injurious VALR. The mere existence of the group of 17 MSR runners was an unexpected development. The prevailing thinking has been that runners who wore minimalist running shoes would automatically transition to using an anterior footstrike pattern. To our knowledge, this is the first biomechanical evaluation of Chi runners. These findings suggest Chi running may be a desirable alternative running style for a runner with a history of lower extremity overuse injuries or someone who desires to reduce potentially injurious forces on the lower extremity. Running with a rearfoot strike pattern in minimalist shoes may produce vertical ground reaction force loading rates that have been associated with injury. Clinicians should not assume that a runner who wears minimalist shoes uses an anterior footstrike pattern. Clinical evaluation and runner education are imperative.Doctor of Philosoph

The Linear Polarization of Sagittarius A* I. VLA Spectro-polarimetry at 4.8 and 8.4 GHz

Synchrotron radiation from active galactic nuclei (AGN) is often highly polarized. We present a search for linear polarization with the Very Large Array (VLA) at 4.8 GHz and 8.4 GHz from the nearest AGN, Sagittarius A*. As a part of this study we used spectro-polarimetric data that were sensitive to a rotation measure (RM) as large as 3.5 x 10^6 rad m^-2 at 4.8 GHz and 1.5 x 10^7 rad m^-2 at 8.4 GHz. The upper limit to the linear polarization of Sgr A* over a broad range of RM is 0.2% at both frequencies. We also present continuum observations with the VLA at 4.8 GHz which give an upper limit of 0.1% for RMs less than 10^4 rad m^-2. We conclude that depolarization is unlikely to occur in the Galacter Center scattering medium. However, it is possible for depolarization to occur in the accretion region of Sgr A* if the outer scale of turbulence is small enough. We also consider the implications of a very low intrinsic polarization for Sgr A*.Comment: 16 pages, 3 figures, accepted for publication in the Astrophysical Journal, August 20, 1999, Vol 521 #

A Radio Transient 0.1 pc from Sagittarius A*

We report the discovery of a transient radio source 2.7 arcsec (0.1 pc projected distance) South of the Galactic Center massive black hole, Sagittarius A*. The source flared with a peak of at least 80 mJy in March 2004. The source was resolved by the Very Large Array into two components with a separation of ~0.7 arcsec and characteristic sizes of ~0.2 arcsec. The two components of the source faded with a power-law index of 1.1 +/- 0.1. We detect an upper limit to the proper motion of the Eastern component of ~3 x 10^3 km s^-1 relative to Sgr A*. We detect a proper motion of ~10^4 km s^-1 for the Western component relative to Sgr A*. The transient was also detected at X-ray wavelengths with the Chandra X-ray Observatory and the XMM-Newton telescope and given the designation CXOGC J174540.0-290031. The X-ray source falls in between the two radio components. The maximum luminosity of the X-ray source is ~10^36 erg s^-1, significantly sub-Eddington. The radio jet flux density predicted by the X-ray/radio correlation for X-ray binaries is orders of magnitude less than the measured flux density. We conclude that the radio transient is the result of a bipolar jet originating in a single impulsive event from the X-ray source and interacting with the dense interstellar medium of the Galactic Center.Comment: accepted in ApJ; 24 pages; 8 figure

The Intrinsic Size of Sagittarius A* from 0.35 cm to 6 cm

We present new high-resolution observations of Sagittarius A* at wavelengths of 17.4 to 23.8 cm with the Very Large Array in A configuration with the Pie Town Very Long Baseline Array antenna. We use the measured sizes to calibrate the interstellar scattering law and find that the major axis size of the scattering law is smaller by ~6% than previous estimates. Using the new scattering law, we are able to determine the intrinsic size of Sgr A* at wavelengths from 0.35 cm to 6 cm using existing results from the VLBA. The new law increases the intrinsic size at 0.7 cm by ~20% and <5% at 0.35 cm. The intrinsic size is 13^{+7}_{-3} Schwarzschild radii at 0.35 cm and is proportional to lambda^gamma, where gamma is in the range 1.3 to 1.7.Comment: ApJL, in pres

Radio astronomy

The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations

Detection of the Intrinsic Size of Sagittarius A* through Closure Amplitude Imaging (includes Online Supporting Material)

We have detected the intrinsic size of Sagittarius A*, the Galactic Center radio source associated with a supermassive black hole, showing that the short-wavelength radio emission arises from very near the event horizon of the black hole. Radio observations with the Very Long Baseline Array show that the source has a size of $24 \pm 2$ Schwarzschild radii at 7 mm wavelength. In one of eight 7-mm epochs we also detect an increase in the intrinsic size of $60^{+25}_{-17}$%. These observations place a lower limit to the mass density of Sgr A* of $1.4\times10^{4}$ solar masses per cubic astronomical unit.Comment: Accepted for publication in Science. Includes the supporting online material that accompanies the main article, which describe further details of the analysis of this experimen

Study design considerations for the Standardized Treatment of Pulmonary Exacerbations 2 (STOP2): A trial to compare intravenous antibiotic treatment durations in CF

BACKGROUND: Pulmonary exacerbations (PEx) in cystic fibrosis (CF) are common and contribute to morbidity and mortality. Duration of IV antibiotic therapy to treat PEx varies widely in the US, and there are few data to guide treatment decisions. METHODS: We combined a survey of CF stakeholders with retrospective analyses of a recent observational study of CF PEx to design a multicenter, randomized, prospective study comparing the efficacy and safety of different durations of IV antibiotics for PEx to meet the needs of people with CF and their caregivers. RESULTS: IV antibiotic duration was cited as the most important PEx research question by responding CF physicians and top concern among surveyed CF patients/caregivers. During PEx, forced expiratory volume in 1s (FEV1% predicted) and symptom responses at 7-10days of IV antibiotics identified two distinct groups: early robust responders (ERR) who subsequently experienced greater FEV1 improvements compared to non-ERR (NERR). In addition to greater FEV1 and symptom responses, only 14% of ERR patients were treated with IV antibiotics for >15days, compared with 45% of NERR patients. CONCLUSIONS: A divergent trial design that evaluates subjects' interim improvement in FEV1 and symptoms to tailor randomization to IV treatment duration (10 vs. 14days for ERR, 14 vs. 21days for NERR) may alleviate physician and patient concerns about excess or inadequate treatment. Such a study has the potential to provide evidence necessary to standardize IV antibiotic duration in CF PEx care -a first step to conducting PEx research of other treatment features

Massive stars in the Cl 1813-178 Cluster. An episode of massive star formation in the W33 complex

Young massive (M >10^4 Msun) stellar clusters are a good laboratory to study the evolution of massive stars. Only a dozen of such clusters are known in the Galaxy. Here we report about a new young massive stellar cluster in the Milky Way. Near-infrared medium-resolution spectroscopy with UIST on the UKIRT telescope and NIRSPEC on the Keck telescope, and X-ray observations with the Chandra and XMM satellites, of the Cl 1813-178 cluster confirm a large number of massive stars. We detected 1 red supergiant, 2 Wolf-Rayet stars, 1 candidate luminous blue variable, 2 OIf, and 19 OB stars. Among the latter, twelve are likely supergiants, four giants, and the faintest three dwarf stars. We detected post-main sequence stars with masses between 25 and 100 Msun. A population with age of 4-4.5 Myr and a mass of ~10000 Msun can reproduce such a mixture of massive evolved stars. This massive stellar cluster is the first detection of a cluster in the W33 complex. Six supernova remnants and several other candidate clusters are found in the direction of the same complex.Comment: 11 Figures. Accepted for publication in Ap

Lower Extremity Biomechanics and Self-Reported Foot-Strike Patterns Among Runners in Traditional and Minimalist Shoes

The injury incidence rate among runners is approximately 50%. Some individuals have advocated using an anterior–foot-strike pattern to reduce ground reaction forces and injury rates that they attribute to a rear–foot-strike pattern. The proportion of minimalist shoe wearers who adopt an anterior–foot-strike pattern remains unclear

American Academy of Periodontology best evidence consensus statement on modifying periodontal phenotype in preparation for orthodontic and restorative treatment

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154649/1/jper10498.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154649/2/jper10498_am.pd