Ion Heating and Flow Driven by an Instability Found in Plasma Couette Flow.

We present the first observation of instability in weakly magnetized, pressure dominated plasma Couette flow firmly in the Hall regime. Strong Hall currents couple to a low frequency electromagnetic mode that is driven by high-ß (>1) pressure profiles. Spectroscopic measurements show heating (factor of 3) of the cold, unmagnetized ions via a resonant Landau damping process. A linear theory of this instability is derived that predicts positive growth rates at finite ß and shows the stabilizing effect of very large ß, in line with observations.

Weakly Magnetized, Hall Dominated Plasma Couette Flow.

A novel plasma equilibrium in the high-ß, Hall regime that produces centrally peaked, high Mach number Couette flow is described. Flow is driven using a weak, uniform magnetic field and large, cross field currents. Large magnetic field amplification (factor 20) due to the Hall effect is observed when electrons are flowing radially inward, and near perfect field expulsion is observed when the flow is reversed. A dynamic equilibrium is reached between the amplified (removed) field and extended density gradients.

Experimental Demonstration of the Collisionless Plasmoid Instability below the Ion Kinetic Scale during Magnetic Reconnection.

The spontaneous formation of magnetic islands is observed in driven, antiparallel magnetic reconnection on the Terrestrial Reconnection Experiment. We here provide direct experimental evidence that the plasmoid instability is active at the electron scale inside the ion diffusion region in a low collisional regime. The experiments show the island formation occurs at a smaller system size than predicted by extended magnetohydrodynamics or fully collisionless simulations. This more effective seeding of magnetic islands emphasizes their importance to reconnection in naturally occurring 3D plasmas.

Adhesive capsulitis of the hip after bilateral adhesive capsulitis of the shoulder.

Adhesive capsulitis of the hip is a not a common clinical presentation. We report a case of adhesive capsulitis of the hip in a patient with hypothyroidism and previous adhesive capsulitis of the shoulder who was receiving thyroid-hormone replacement. The adhesive capsulitis of both hip and shoulder were treated successfully with physical therapy. Orthopedic surgeons should be aware of this diagnosis and its association with shoulder adhesive capsulitis and thyroid dysfunction, to allow them to recognize it and intervene early.

Shift of the posteroinferior aspect of the capsule for recurrent posterior glenohumeral instability.

Thirty-five shoulders in thirty-four patients were treated with a superior shift of the posteroinferior aspect of the capsule because of recurrent posterior glenohumeral subluxation and dislocation. The physical examination revealed three types of posterior instability in these patients preoperatively: unidirectional (six shoulders), bidirectional (posterior and inferior) (seven shoulders), and multidirectional (posterior and inferior dislocation with anterior subluxation) (twenty-two shoulders). Eleven shoulders had had previous operative procedures. At the time of the index operation, the most common abnormal findings in these shoulders were capsular redundancy and excessive volume of the glenohumeral joint. Complete detachment of the posterior aspect of the labrum was found in only four shoulders. There was no excessive glenoid retroversion in these patients. All thirty-four patients were available for follow-up at an average of five years (range, two to twelve and a half years) postoperatively. Over-all, the result for seventeen of the thirty-five shoulders was rated as excellent; eleven, as good; one, as fair; and six, as poor. Four shoulders became unstable again. Six of the seven unsatisfactory results were in shoulders that had had previous attempts at stabilization. A successful result was achieved in twenty-three of the twenty-four shoulders in which the superior shift of the posteroinferior aspect of the capsule was the initial repair.

Treatment of tibial defects and nonunions using ipsilateral vascularized fibular transposition.

Eight patients had nine ipsilateral vascularized fibular transpositions (IVFTs) in the period 1978-1987. The procedure, which involves no microvascular anastomosis, was done for difficult problems of the tibia including two long-standing posttraumatic nonunions, three allograft nonunions after tumor surgery, and four segmental tibial defects also after tumor surgery. The average duration of problems before surgery was 3.5 years, and the patients averaged 3.1 procedures before IVFT. The patients were followed for an average of 52.4 months. The average time to union was 4.2 months, and in all patients the grafts healed within six months. Late fracture of the graft developed in two patients after fixation removal; one required an additional procedure, and both eventually healed. Ipsilateral vascularized fibular grafting is a useful alternative to conventional, nonvascularized grafts for difficult tibial nonunions and segmental defects. It offers the advantages of a vascularized graft (early healing and hypertrophy), yet avoids the time-consuming microvascular anastomosis and distant donor site morbidity of free fibular grafts.

[Plate osteosynthesis in humeral shaft fractures. Indications and results]. / Plattenosteosynthese bei Humerusschaftfrakturen. Indikationen und Resultate.

Non operative management of humeral shaft fractures is well recognized as the standard of care for uncomplicated injuries. Operative treatment of humeral fractures may be performed when limited indications are present as in patients with multiple trauma including ipsilateral forearm injuries, arterial injury or primary radial nerve palsy. 18 patients with humeral shaft fractures underwent open reduction and internal fixation (ORIF) using the AO plating technique at the Kantonsspital Chur from 1980 to 1986. Follow-up was available for 17 patients of whom 16 suffered from multiple injury trauma. The broad DC plate combined with lag screws was used in most cases. Two brachial artery transections were repaired at the time of primary osteosynthesis by the same surgeons with full functional recovery. Concomitant nerve injuries were repaired primarily in one case and postprimarily in 3 more cases. The overall result was excellent in 9 patients, good in 5 patients, fair in 2 patients and poor in one patient with complete brachial plexus injury. Bone healing was uneventful in all 17 patients. No infection and no delayed union or pseudarthrosis has been observed.