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Traumatic brain injury (TBI) has become a signature injury of current military conflicts, with debilitating, costly, and long-lasting effects. Although mechanisms by which head impacts cause TBI have been well researched, the mechanisms by which blasts cause TBI are not understood. From numerical hydrodynamic simulations, we have discovered that nonlethal(More)
Two questions about the solar magnetic field might be answered together once their connection is identified. The first is important for large scale dynamo theory: what prevents the magnetic backreaction forces from shutting down the dynamo cycle? The second question is: what determines the handedness of twist and writhe in magnetized coronal ejecta?(More)
The dramatic decay of dipole geomagnetic field intensity during the last 160 years coincides with changes in Southern Hemisphere (SH) field morphology and has motivated speculation of an impending reversal. Understanding these changes, however, has been limited by the lack of longer-term SH observations. Here we report the first archaeomagnetic curve from(More)
The acknowledgement of risks for traumatic brain injury in American football players has prompted studies for sideline concussion diagnosis and testing for neurological deficits. While concussions are recognized etiological factors for a spectrum of neurological sequelae, the consequences of sub-concussive events are unclear. We tested the hypothesis that(More)
INTRODUCTION Repetitive head impacts (RHI) sustained in contact sports are thought to be necessary for the long-term development of chronic traumatic encephalopathy (CTE). Our objectives were to: 1) characterize the magnitude and persistence of RHI-induced white matter (WM) changes; 2) determine their relationship to kinematic measures of RHI; and 3)(More)
We consider the back reaction of the mean magnetic field on the magnitude of the dynamo helicity coefficient α and obtain upper limits on its magnitude from the equation of magnetic helicity evolution. When gradients in the mean magnetic field vanish, the magnitude of the turbulent EMF, and thus the dynamo coefficient α, has a stringent upper limit that(More)
Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a(More)
MHD winds can emanate from both stars and surrounding disks. When the two systems are coupled by accretion, it is of interest to know which (if either) of the two dominates the outflow power. Recent observations lead us to consider how such coupled MHD winds may be operating in planetary nebulae (PN). In this context, we calculate the MHD wind power from a(More)
We report VLA 1σ upper limits of 1.5% and 3% on the intrinsic circular and linear fractional polarizations, respectively, of the water vapor maser emission 0.2 pc from the central engine of NGC 4258. A corresponding 0.5% upper limit on any Zeeman-splitting-induced circular polarization translates to a 1σ upper limit on the parallel, or toroidal, component(More)