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Hydrothermal synthesis of BaTi03 at 240 °C in the presence of chloride ions leads to the formation of the tetragonal polymorph upon cooling through the Curie temperature. In the absence of Cl-, the metastable cubic structure is formed. Though the exact role of Cl" is not clear, it appears that it leads to formation of larger (~1 pm) crystals as compared to smaller crystals (~0.2 /rm) in its absence. Combination of diffraction and calorimetry provides unambiguous support for the presence of the tetragonal form.

The purpose of this study was to evaluate anterior cruciate ligament reconstructions performed in adolescents with open physes and a skeletal age of at least 14 years. At one center, from 1992 to 1996, 19 adolescents (ages, 11 to 15 years) with open physes and a skeletal age of at least 14 years underwent arthroscopic anterior cruciate ligament reconstruction using an Achilles tendon allograft placed through drill holes across the open physes in both the distal femur and proximal tibia. Fifteen patients returned for reevaluation at an average of 25 months postoperatively (range, 12 to 60 months); the remaining four patients were interviewed by telephone. There were no significant leg-length discrepancies or angular deformities as determined by scanograms and anteroposterior and lateral radiographs of the femur and tibia. The mean Lysholm knee score was 97 (range, 94 to 100) and the mean KT-1000 arthrometer side-to-side difference at 20 pounds of anterior force was 1.7 mm (range, 0.0 to 3.0). All patients were satisfied with the results of surgery, and 16 of 19 patients returned to the same sport they were participating in before the injury. This study demonstrates that anterior cruciate ligament reconstruction using an Achilles tendon allograft is a viable treatment option for skeletally immature patients with a skeletal age of 14 years who have sustained midsubstance tears of the anterior cruciate ligament.

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Twelve consecutive patients (average age 10.6 years) with 14 dislocated hips underwent one-stage hip reconstruction between 1973 and 1981. The procedure consisted of (1) adductor myotomy and anterior obturator neurectomy, (2) circumferential capsulotomy, iliopsoas and external rotator tenotomies, and ligamentum teres and pulvinar excision, (3) shortening femoral varus derotational osteotomy, (4) acetabuloplasty, and (5) spica immobilization for 4 weeks. All patients were followed clinically and radiographically at an average of 16.7 (range 12.4-19.5) years. No patients were lost to follow-up. Long-term results revealed complete stability in 13 of 14 hips, with no redislocations or subluxations. The one patient with "instability" had undergone bilateral proximal femoral resections for severe arthritis 12 years after left hip reconstruction; at the time of resection, the left hip was stable and reduced. Pain was absent in 13 of 14 hips. There were no problems with perineal care, decubitus formation, or sitting tolerance. Extension and abduction improved an average of 23 degrees and 10 degrees, respectively. Two patients' ambulatory status improved; none deteriorated. The mean center-edge angle was 35 degrees (range 22-50 degrees), and the mean migration percentage was 10.6% (range 0-31%). Complications included one case of degenerative arthritis, one case of painless coxa vara, and three episodes of supracondylar femur fractures. None of these patients developed radiographic evidence of avascular necrosis. In the authors' experience, one-stage hip reconstruction consisting of soft tissue lengthening, open reduction, femoral osteotomy, and pericapsular acetabuloplasty results in a painless, mobile, and stable hip at long-term follow-up that greatly improves the patient's quality of life.

Two contrasting mechanisms have been proposed for the establishment of the prestalk‐prespore pattern in the multicellular aggregate of the simple eukaryote Dictyostelium discoideum. One involves intermingled, non‐position‐dependent cell differentiation followed by sorting out which produces the pattern of prestalk cells in the anterior region and prespore cells posteriorly. The second mechanism involves patterning according to the position of cells within the aggregate, in which case intermingled cell types are not expected. Here we use a monoclonal antibody (MUD1), recognising a prespore cell surface antigen, to study the initial appearance of prespore cells in aggregates. Quantitative studies were made with a flow cytometer and frozen sections were used to localise the cells expressing the prespore antigen. This antigen first appeared at the onset of tip formation in the centre of aggregates in a position‐dependent fashion. The prespore antigen was not detected in the tip region or in streams of cells entering the aggregate. We re‐examined the evidence on which the non‐position‐dependent differentiation model is based. Our results support the positional model for pattern formation.