ABSTRACT
The origin of the seed magnetic field that is amplified by the galactic dynamo is an open question in plasma astrophysics. Aside from primordial sources and the Biermann battery mechanism, plasma instabilities have also been proposed as a possible source of seed magnetic fields. Among them, thermal Weibel instability driven by temperature anisotropy has attracted broad interests due to its ubiquity in both laboratory and astrophysical plasmas. However, this instability has been challenging to measure in a stationary terrestrial plasma because of the difficulty in preparing such a velocity distribution. Here, we use picosecond laser ionization of hydrogen gas to initialize such an electron distribution function. We record the 2D evolution of the magnetic field associated with the Weibel instability by imaging the deflections of a relativistic electron beam with a picosecond temporal duration and show that the measured [Formula: see text]-resolved growth rates of the instability validate kinetic theory. Concurrently, self-organization of microscopic plasma currents is observed to amplify the current modulation magnitude that converts up to ~1% of the plasma thermal energy into magnetic energy, thus supporting the notion that the magnetic field induced by the Weibel instability may be able to provide a seed for the galactic dynamo.
ABSTRACT
Historically, the published literature on "terrible triad" injuries has shown a high rate of unacceptable results. The use of systematic treatment protocols may improve functional outcome. The authors performed a retrospective study of all patients aged 18 years or older who underwent surgical treatment for "terrible triad" elbow fracture dislocation at their institution over a period 7 years. Surgical treatment involved fixation or replacement of the radial head, repair of the anterior capsule or coronoid fracture in most cases, and repair of the lateral collateral ligament. Outcomes included grip strength, range of motion, Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire score, and a visual analog score for pain as well as radiographic assessment of arthritis, maintenance of reduction, and development of heterotopic ossification. Eighteen patients were identified and 11 enrolled. Seven patients had suture fixation of the coronoid fragment and anterior capsule, 2 had screw fixation, and 2 had no repair of the coronoid. The radial head was replaced in 9 patients and repaired in 1, and a fracture fragment was excised in another. The average follow-up was 38 months. The average arc of motion of the injured elbow was 112° and that of the contralateral elbow was 142°. The average DASH score was 19.7 (scale, 0-100). The average visual analog score for pain was 2.2 (scale, 0-10). No patients had recurrent elbow instability. Three patients underwent further surgical procedures, all for loss of motion. The authors concluded that a systematic approach to the fixation of "terrible triad" elbow fracture dislocations can provide predictable elbow stability and functional range of motion in the medium term.
