Assessment of pseudarthrosis in pedicle screw fusion: a prospective study comparing plain radiographs, flexion/extension radiographs, CT scanning, and bone scintigraphy with operative findings

Tribal warfare is a way of life in the highlands of Papua New Guinea. In earlier times direct confrontation with bushknives and axes, and shooting with bows and arrows were common. In recent years there have not been as many instances of direct confrontation with bushknives and axes, but the use of bows and arrows is on the rise. Since 1993, guns have been increasingly used, with devastating results. In 1993, 18 deaths were reported from tribal warfare in one area of the Southern Highlands Province, especially from gunshots, while in 1994, 24 deaths were reported from another area. A five-year review of tribal fight admissions to Mendi Hospital, from 1990 to 1994, showed an increase in the number and proportion of gunshot wounds; there were none in 1990-1992 but they constituted 18% of tribal fight injuries in 1993 and 33% in 1994.     

Directed oxidation/nitridation of Al alloys: The orientation of the oxides/nitrides formed adjacent to Al2O3 or AlN reinforcement particles

Journal of Materials Science Letters -     

Characterization of ZrO2-Y2O3 thermal barrier coatings by Raman spectroscopy

Raman spectroscopy is shown to be a useful tool for the observation of phase transitions in Y₂O₃-stabilized ZrO₂ thermal barrier coatings. Data were collected in situ at temperatures up to 1050°C as a function of the Y₂O₃ content. Large hysteresis effects are observed in the phase transition temperatures.     

Formation of Al2O3/Metal Composites by the Directed Oxidation of Molten Aluminum-Magnesium-Silicon Alloys: Part I, Microstructural Development

The growth of α-Al₂O₃/metal composites by the directed oxidation of molten Al-Mg-Si alloys proceeds through four distinct stages. The first stage encompasses the early heating of the alloy ingot, melting, and continued heating to between 1123 and 1173 K. In this latter temperature range, the molten alloy surface rapidly oxidizes to form a MgO-covered MgAl₂O₄ layer. During further heating and initial soak at the composite growth temperature (1373 to 1573 K), the duplex layer slowly thickens (second stage). The start of the third stage, growth initiation, is marked by the spread of a metal-rich zone over the duplex layer; this metal-rich zone is believed to be connected to the molten alloy through microcracks in the thickened MgO/MgAl₂O₄ layer. Small nodules of the oxide/metal composite nucleate from the metal-rich layer. During the final rapid growth stage, the small composite nodules grow and coalesce to form a macroscopically planar growth front, which persists until growth is complete. Throughout the growth process, the external surface of the α-Al₂O₃/metal composite is covered by a thin MgO layer. Immediately under this external layer and separating it from the α-Al₂O₃ is a thin layer of molten metal.     

Pedicle screw fixation for arthrodesis of the lumbosacral spine in the elderly. An outcome study

STUDY DESIGN: An analysis of the outcome and effectiveness of instrumented arthrodesis of the lumbosacral spine in elderly patients conducted using a review of records, assessment of fusion via plain radiographs, and a two-part questionnaire. OBJECTIVE: To ascertain the outcome and efficacy of instrumented arthrodesis of the lumbosacral spine in patients 60 years of age and older. BACKGROUND DATA: From 1987 to 1991, 38 patients of at least 60 years of age underwent instrumented arthrodesis of the lumbosacral spine using the Wiltse or Selby pedicle screw fixation system (Advanced Spine Fixation Systems, Inc., Irvine, CA). Patients were considered for surgery only after attempts at conservative management, including physical therapy, medication, injection blocks, and home exercises, had proven unsuccessful. METHODS: Follow-up examinations were performed 3 months, 6 months, 1 year, and 2 years after surgery. Fusion was assessed using plain radiographs, including flexion-extension films. Inpatient and outpatient records were reviewed, and a two-part questionnaire was used to establish the effect of surgery on function and lifestyle. Thirty patients responded to the questionnaire. Follow-up observation of the patients ranged from 25 to 56 months. The mean age was 73.8 years (range, 60-90 years). RESULTS: The mean co-morbidity was 1.7. Based on the authors' method of evaluation of fusion, the fusion rate was 92%. Fifty-seven percent of the patients reported excellent or good results, 26% reported fair results, and 17% reported poor results. Functional gains of 50% or more were reported by 71% of the respondents. Female patients had significantly more complications than male patients, but reported comparable outcomes. CONCLUSION: Despite the increase in age, co-morbidity, and associated risk of perioperative complications inherent in this population, an outcome comparable with that of younger patients is reported.     

Kinetics of Formation of a Platelet-Reinforced Ceramic Composite Prepared by the Directed Reaction of Zirconium with Boron Carbide

The kinetics of formation of a new class of ceramic composite material, zirconium diboride platelet-reinforced zirconium carbides, are discussed. These materials are prepared by the directed reaction of molten zirconium with boron carbide to form a ceramic material composed of zirconium carbide matrix containing a controlled amount of residual zirconium metal. Results from interrupted growth studies, differential thermal analysis, adiabatic reaction temperature calculations, and kinetic measurements have been used to study the kinetics of the process. The reaction is very fast and proceeds parabolic ally with time with a rate constant between 1.6 X 10^-2 and 3.9 X 10^-2 cm²/_s. The proposed mechanism suggests that when molten zirconium contacts boron carbide, the molten zirconium exothermically reacts with the boron carbide to form a boron-rich liquid. Further reaction is sustained by the continuous dissolution of the boron carbide as the boron-rich liquid is drawn into the boron carbide. The product is a zirconium carbiride/zirconium carbide/zirconium composite which homogenizes quickly at the reaction temperature to yield a uniform product microstructure throughout the composite. Two alternative rate-limiting steps are discussed and the implications of each are explored.     

Bulimia?=?bulimarexia?=?bulimia nervosa.

S. Cullari and W. K. Redmon (see record 1984-04326-001) suggested that bulimarexia and bulimia nervosa are similar to one another but different from bulimia. The present author argues that given the current state of knowledge, it is conceptually incorrect to consider bulimia and bulimiarexia as separate eating disorders and that such a distinction may lead to serious problems in both clinical research and practice. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxidation of titanium modified type 310 stainless steel in low oxygen partial pressure atmospheres

A series of modified type 310 stainless steels containing 3 wt.% titanium were oxidized in a low oxygen partial pressure atmosphere ( 3.8× 10 ^–15 atm) at 1255 K (1800°F). The scale morphologies and growth rates were similar to those observed on the same alloys in coal gasification atmospheres. The presence of sulfur (as H ₂ S) in the gasification atmosphere apparently has a minimal effect on the corrosion scale formed. The growth rate and phase transformations of the external titanium-rich layer indicate that both titanium and manganese can readily permeate through the apparently compact Cr ₂ O ₃ layer.     

Formation of Al2O3/Metal Composites by the Directed Oxidation of Molten Aluminum-Magnesium-Silicon Alloys: Part II, Growth Kinetics

The growth kinetics of an Al₂O₃/metal composite by the directed oxidation of an aluminum alloy (10 wt% Si, 3 wt% Mg, balance Al) have been measured as a function of temperature (1398 to 1548 K) and oxygen partial pressure in O₂/Ar gas mixtures. The growth rate exhibited an activation energy of ∼370 kJ/mol and a dependence on oxygen partial pressure consistent with a P _o^1/4₂ relationship. A dissolution-precipitation growth mechanism is proposed in which the growth rate is controlled by the electronic conductivity of an external Al₂O₃-doped MgO surface layer in conjunction with grain boundary diffusion of magnesium.