Direct observation of the alpha-epsilon transition in shock-compressed iron via nanosecond x-ray diffraction.

In situ x-ray diffraction studies of iron under shock conditions confirm unambiguously a phase change from the bcc (alpha) to hcp (epsilon) structure. Previous identification of this transition in shock-loaded iron has been inferred from the correlation between shock-wave-profile analyses and static high-pressure x-ray measurements. This correlation is intrinsically limited because dynamic loading can markedly affect the structural modifications of solids. The in situ measurements are consistent with a uniaxial collapse along the [001] direction and shuffling of alternate (110) planes of atoms, and are in good agreement with large-scale nonequilibrium molecular dynamics simulations.

Pain reduction in breast augmentation using methocarbamol.

Submuscular placement of breast implants produces significant postoperative pain and discomfort. The standard use of narcotics alone does not optimize pain reduction. Methocarbamol was used intraoperatively and postoperatively in 62 patients undergoing manipulation of the pectoralis major associated with breast implant surgery. Significant pain relief was achieved.

Explantation and mastopexy: the vertical mammaplasty technique to optimize breast shape.

Twenty-seven patients who requested removal of their breast implants underwent simultaneous explantation and mastopexy. The time from implantation to explantation ranged from 4 to 26 years. Follow-up after surgery ranged from 5 months to 3 years. The mastopexy procedure used is a modification of the vertical mammaplasty. The final form of the breast is dependent on parenchymal reshaping rather than the pattern shape of the skin brassiere. The technique produced satisfactory breast shape and projection while limiting the extent of skin scarring. Minimal complications were noted, and patient satisfaction remains high.

Comparison of rapid versus slow tissue expansion on skin-flap viability.

The effect of rapid versus slow tissue expansion on random-pattern skin-flap survival lengths was evaluated in two groups of pigs. Each group (group 1--slow; group 2--rapid) was further evaluated for the effect that delay (A), delay plus expansion (B), expansion only (C), and acute flap elevation (D) had on flap length viability. Intergroup and intragroup comparisons were made. In the slowly expanded group, significantly greater flap length viabilities were demonstrated in the slow expansion flaps as compared with the delay plus expander flaps and the delayed flaps, respectively. In the rapidly expanded group, the flap length viabilities of flaps C, B, and A were statistically equal. However, the flap length viability of the rapidly expanded flaps was statistically equal to that of the slowly expanded flaps (C1 = C2). The effect tissue expansion has on improving flap length viability as compared with the delay phenomenon may be related to the combination of a delay effect plus increased nutrient flow density that slow expansion produces. This combined metabolic enhancement is preserved with rapid tissue expansion.

Cementoma--presentation predicates approach.

Cementomas are benign jaw tumors that originate from periodontal ligament elements. Four classifications of cementomas are described: periapical fibrous dysplasia, benign cementoblastoma, cementifying fibroma, and florid osseous dysplasia. Usual treatment regimens vary from observation to limited surgical resection based upon tumor type and clinical characteristics. We present an unusual case report of an extensive cementifying fibroma that required mandibular and inferior alveolar nerve resection followed by osseous and neural reconstruction.

Large diameter therapeutic penetrating keratoplasties.

Fourteen penetrating keratoplasties were done on ten patients using 9.5 mm or larger diameter grafts. The causes for large grafts were perforation or impending perforation of large descemetoceles due to bacterial ulceration in five eyes, herpes simplex viral keratouveitis in three eyes, severe keratoconjunctivitis sicca with ulceration in four eyes, alkali burn and Mooren's ulcer in one eye each. The average duration of graft clarity was 67.2 days (range 14 days to 6 months). The best spectacle corrected visual acuity range was from l.p. to 20/40. Two patients had recurrent ulceration requiring two large diameter regrafts each. The average period of clarity in these repeated grafts was 26 days. A small graft placed inside of the failed large graft remained clear in 50% of the six eyes which were done for visual restoration. A large diameter penetrating keratoplasty may salvage an eye that might have otherwise been lost and in a few cases provide the opportunity for useful vision.

The tensiometric properties of expanded guinea pig skin.

Our purpose in this study was to evaluate the tensile properties of expanded skin. In five guinea pigs, 29-cc ovoid tissue expanders were placed and sequentially expanded every 4 days until maximum volume was achieved. Five control and five expanded skins were harvested. Using an Instron tensile testing apparatus, skins were evaluated for stress-strain, maximum stiffness, and tensile strength, and the results were statistically compared. Centrally located expanded specimens demonstrated significantly weaker stress-strain values: 9.51 in.lb/in3 for expanded versus 30.11 in.lb/in3 for control (p less than 0.001). Maximum stiffness was similarly reduced: 4.56 lb/mm2 for expanded vs. 12.98 lb/mm2 for control (p less than 0.001). This is a 67.4 and 64.9 percent reduction, respectively, for the stress-strain and maximum stiffness. No statistically significant difference was seen in peripherally located expanded specimens relative to the controls: stress-strain expanded, 28.7 in.lb/in3 (p greater than 0.5); maximum stiffness expanded, 12.84 lb/mm2 (p greater than 0.5). Expanded skin demonstrated an average 35 percent reduction in tensile strength. We conclude that the tensile properties of expanded skin are significantly less than unexpanded skin and are a function of the degree of expansion.