The mechanically induced structural disorder in barium hexaferrite, BaFe12O19, and its impact on magnetism.

The response of the structure of the M-type barium hexaferrite (BaFe12O19) to mechanical action through high-energy milling and its impact on the magnetic behaviour of the ferrite are investigated. Due to the ability of the (57)Fe Mössbauer spectroscopic technique to probe the environment of the Fe nuclei, a valuable insight on a local atomic scale into the mechanically induced changes in the hexagonal structure of the material is obtained. It is revealed that the milling of BaFe12O19 results in the deformation of its constituent polyhedra (FeO6 octahedra, FeO4 tetrahedra and FeO5 triangular bi-pyramids) as well as in the mechanically triggered transition of the Fe(3+) cations from the regular 12k octahedral sites into the interstitial positions provided by the magnetoplumbite structure. The response of the hexaferrite to the mechanical treatment is found to be accompanied by the formation of a non-uniform nanostructure consisting of an ordered crystallite surrounded/separated by a structurally disordered surface shell/interface region. The distorted polyhedra and the non-equilibrium cation distribution are found to be confined to the amorphous near-surface layers of the ferrite nanoparticles with the thickness extending up to about 2 nm. The information on the mechanically induced short-range structural disorder in BaFe12O19 is complemented by an investigation of its magnetic behaviour on a macroscopic scale. It is demonstrated that the milled ferrite nanoparticles exhibit a pure superparamagnetism at room temperature. As a consequence of the far-from-equilibrium structural disorder in the surface shell of the nanoparticles, the mechanically treated BaFe12O19 exhibits a reduced magnetization and an enhanced coercivity.

A comparison of flap vascular anatomy in three rhytidectomy techniques.

The purpose of this study was to examine differences in blood supply to facial flaps created by three rhyditectomy techniques. The techniques chosen for comparison included a two-layer technique, consisting of separate subcutaneous and extended submuscular aponeurotic system (SMAS) dissections, the Composite dissections as described by Hamra, and a subperiosteal dissection. Six cadavers were injected with lead oxide before dissection, and eight were injected after dissection. After allowing the lead oxide to set, the soft tissues were removed from the face. Vascular patterns of the face were interpreted from x-rays taken of the specimens. Results of the injections performed before dissection confirmed contributions of previously described arteries, including the transverse facial, facial, infra-orbital and terminal branches of the ophthalmic. In addition, there are numerous branches that connect these vessels to each other. The most consistent of these include the masseteric, jugal, submental, labial, angular and nasal arteries. The patterns of communications between these vessels allow for the visualization of three vertically oriented vascular zones, each connected to the next by choke zones where anastomoses occur. Dissections performed before injection reveal increased filling of the vessels through more of the flap on the Composite side when compared with the two-layered dissection, absence of vessels in the SMAS, and filling across all three zones on the subperiosteal side. We conclude that there are vascular regions in the face connected by anastomotic choke zones. Separate subcutaneous and sub-SMAS dissections interrupt the vascular connection between zones. Arterial continuity is better-maintained in the Composite lift and is literally undisturbed in the subperiosteal lift.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast reconstruction in women treated with radiation therapy for breast cancer: cosmesis, complications, and tumor control.

The records of 55 patients who had breast cancer treated by mastectomy, irradiation, and breast reconstruction were reviewed for cosmetic outcome, complications, and tumor control. Median follow-up was 35 months. Local control rates were 95 percent in patients treated for high risk factors or breast conservation and 85 percent in patients treated for recurrent breast cancer. Acceptable cosmetic results were obtained in only 42 percent of patients. The incidence of complications was 55 percent. Transverse rectus abdominis muscle (TRAM) reconstructions gave superior cosmetic results compared with all other types of reconstructions. The timing of reconstruction in relation to mastectomy or radiation therapy did not significantly influence cosmetic outcome, although other factors suggest that delayed reconstruction may give better results. A majority of patients were satisfied with cosmetic outcome.

Intracerebral hematoma complicating split calvarial bone-graft harvesting.

A case is reported of an intracerebral hematoma following the harvest of split calvarial bone. Full recovery by the patient occurred. Complications following calvarial bone graft harvest are reviewed. Potential devastating complications warrant serious consideration of alternative sources of bone, especially in the purely elective surgical candidate.

The use of tissue expanders in immediate breast reconstruction following mastectomy for cancer.

From April 1985 to March 1987, 50 women had 56 mastectomies for documented cancer. A tissue expander was used for immediate reconstruction in each case. The patient records were used to determine morbidity and mortality, as well as to examine the effect of reconstruction on adjuvant therapy, cancer surveillance, adequacy of cancer surgery and patient satisfaction. The patients were followed up for an average of 13 months. Fifty-two of 56 expanders were successfully replaced with a permanent prosthesis. Forty-seven women remain alive. Local or regional recurrence did not occur in any women within the study period. Complications, of which superficial skin necrosis was most common, occurred in 35% of reconstructions and were investigated critically. Patient satisfaction was high. Dissatisfaction was not related to the incidence of complications but rather appeared to reflect the success of the patient's cancer treatment.

Lekking behavior in kafue lechwe.

The Kafue lechwe (Kobus leche kafuensis) exhibits lekking behavior in which a number of males occupy small territories clustered together in discrete areas where females go for mating. Similar behavior in antelope is known only in the Uganda kob (Kobus kob thomasi). Lechwe lekking occurs only during a main rutting season although some breeding occurs throughout the year.