Processing, Microstructures, and Properties of Cr-Cr3Si, Nb-Nb3Si, and V-V3Si Eutectics

The present paper examines the potential of refractory metal-A15 silicide composites as structural materials for high temperature applications. Three eutectic systems are considered, Cr-Cr₃Si, Nb-Nb₃Si, and V-V3Si, since they all have melting points above 1700°C and densities lower than Ni-based superalloys. Eutectic compositions were selected because directional solidification of eutectics can be used to generate aligned composite microstructures. The present paper describes processing, microstructures and properties of directional ly solidified Cr-Cr₃Si, Nb-Nb₃Si, and V-V₃Si. Based on microstructural and chemical analyses, some phase diagram modifications are suggested. The orientation relationships between the refractory metal and A15-silicide phases were characterized using transmission electron microscopy. In the Cr-Cr₃Si eutectic a strong orientation relationship was observed; there was excellent lattice matching of the (110) in Cr and (210) in Cr₃Si. Room temperature and elevated temperature microhard-ness and fracture toughness are also reported; these indicate good strength retention in Nb-Nb₃Si at elevated temperatures.     

Noninvasive assessment of regional ventilation in the human lung using oxygen-enhanced magnetic resonance imaging

The imaging of regional ventilation in the lungs is essential for the evaluation of a variety of pathological conditions, such as emphysema, pneumonia and pulmonary embolism. We propose a novel approach for ventilation scanning, using magnetic resonance imaging (MRI) and inhaled molecular oxygen as a contrast agent, that directly depicts transfer of oxygen across the alveolus into the pulmonary vasculature. Molecular oxygen is only weakly paramagnetic but produces substantial signal changes in the lungs because of their large surface area. Ventilation defects were shown in a patient with bullous emphysema, and ventilation-perfusion mismatches were shown in two patients with pulmonary embolism.     

Implanted functional electrical stimulation hand system in adolescents with spinal injuries: an evaluation

OBJECTIVE: To study the utility and functional benefits of an implanted functional electrical stimulation (FES) system for hand grasp and release in adolescents with tetraplegia secondary to spinal cord injuries. DESIGN: Intervention study with before-after trial measurement with each subject as his or her own control. SETTING: Nonprofit pediatric orthopedic rehabilitation facility specializing in spinal cord injury. PARTICIPANTS: A convenience sample of five adolescents between 16 and 18 years of age with C5 or C6 level tetraplegia at least 1 year after traumatic spinal cord injury. Key muscles for palmar and lateral grasp and release were excitable by electrical stimulation. INTERVENTIONS: A multichannel stimulator/receiver and eight electrodes were surgically implanted to provide stimulated palmar and lateral grasp and release. In conjunction with implantation of the FES hand system, surgical reconstruction in the form of tendon transfers, tendon lengthenings and releases, and joint arthrodeses was performed to augment stimulated hand function. Rehabilitation of the tendon transfers and training in the use of the FES hand system were provided. MAIN OUTCOME MEASURES: Measurements of pinch and grasp force, the Grasp and Release Test (GRT), and an assessment of six activities of daily living (ADL) were administered before implantation of the FES hand system and at regular follow-up intervals. Results of the stimulated response of individual muscles and surgical reconstruction were evaluated using standard and stimulated muscle testing techniques and standard assessment of joint range of motion. All subjects completed followup testing. RESULTS: Lateral and palmar forces were significantly greater than baseline forces (p = .043). Heavy objects on the GRT could only be manipulated with FES, and FES increased the level of independence in 25 of 30 ADL comparisons (5 subjects, 6 activities) as compared to baseline. After training, FES was preferred in 21 of 30 comparisons over the typical means of task completion. Of the 40 electrodes implanted, 37 continue to provide excellent stimulated responses and all of the implanted stimulators have functioned without problems. The surgical reconstruction procedures greatly enhanced FES hand function by either expanding the workspace in which to utilize FES (deltoid to triceps transfer), stabilizing the wrist (brachioradialis to wrist extensor transfer), or stabilizing joints (intrinsic tenodesis transfer, FPL split transfer). CONCLUSION: For five adolescents with tetraplegia, the combination of FES and surgical reconstruction provided active palmar and lateral grasp and release. Laboratory-based assessments demonstrated that the FES system increased pinch force, improved the manipulation of objects, and typically increased independence in six standard ADL as compared to pre-FES hand function. The study also showed that the five adolescents generally preferred FES for most of the ADL tested. Data on the benefits of the implanted FES hand system outside of the laboratory are needed to understand the full potential of FES.     

Microsoft robotics studio: A technical introduction

Microsoft robotics studio (MSRS) was publicly released in December 2006 with the explicit goal of providing an industry software standard for robot control. To become a viable standard, several technical challenges needed to be solved. In this article, we examine the composition of MSRS, looking generally at its architecture and specifically at its solutions for concurrency, distribution, abstraction, simulation, and programmer interaction. We also examine briefly the emerging industry and academic adoption of the robotics studio.     

Pentoxifylline therapy in human immunodeficiency virus-seropositive persons with tuberculosis: a randomized, controlled trial

Macrophage activation and tumor necrosis factor-alpha (TNF-alpha) production are critical in tuberculosis immunity but may result in increased human immunodeficiency virus (HIV) expression and accelerated HIV disease progression in HIV-infected persons. Pentoxifylline inhibits expression of TNF-alpha and HIV. A double-blind, placebo-controlled study of adjunctive therapy with pentoxifylline (1800 mg/day) as a timed-release formulation was done in Ugandan HIV-infected patients with pulmonary tuberculosis. Subjects had early HIV disease (mean CD4 cell count, 380/microL) and did not receive other antiretroviral drugs. Pentoxifylline resulted in decreased plasma HIV RNA and serum beta 2-microglobulin and, in a subset of moderately anemic patients, improved blood hemoglobin levels. Trends were noted toward reduced TNF-alpha production in vitro and improved performance scores, but these did not reach statistical significance. No effect was noted on body mass, CD4 cell count, or survival. Additional studies of more potent TNF-alpha inhibitors in HIV-positive subjects with tuberculosis are warranted.     

Management of lymphoproliferative disorders after cardiac transplantation

We conducted a retrospective study of 516 cardiac recipients who underwent transplantation between April 1983 and April 1992, 19 of whom had development of post-transplantation lymphoproliferative disorders (PTLDs). These 19 patients presented with involvement of lung (5), gastrointestinal tract (5), disseminated disease (6), and adenoids and lymph nodes (3). B-cell proliferations ranging from an atypical hyperplasia to malignant lymphoma developed in 18 patients, and mixed cellularity Hodgkin's disease developed in 1 patient. The 19 patients with PTLD displayed a predominance of both women and cardiomyopathy as the indication for transplantation when compared with two separate control populations. No correlation was found between demographic criteria analyzed and (1) early versus late diagnosis of PTLD after transplantation, (2) the site of PTLD involvement, or (3) the histopathologic category of the PTLD lesion. Patients with gastrointestinal tract and lung PTLD involvement enjoyed an improved survival after both transplantation and PTLD diagnosis when compared with patients with PTLD involvement of all other extranodal sites. We report a high incidence of PTLD involving the lung and gastrointestinal tract in our cohort study. These sites of involvement responded better to a reduction in immunosuppression than did the other extranodal sites of involvement.     

Disguise and the structured self-report assessment of psychopathology: I. An analogue investigation.

Explored the utility of disguise in structured self-report assessments of psychopathology in 3 experiments with 370 university students. Exp I used items from the Basic Personality Inventory (BPI); Exp II used the BPI, the Desirability scale of the Personality Research Form—Form E, and 4 criterion measures; and Exp III used 2 of the criterion measures and the BPI. Data indicate that under normal test-taking circumstances, the use of disguised test items was not advantageous. This relationship, however, was moderated by a number of dimensional parameters. When faking response sets in terms of desirability was induced, the use of disguised test item content was not useful. Data are interpreted in terms of the various strategies of test construction underlying the assessment of psychopathology. Results support a rational strategy of test construction emphasizing the use of relevant test item content. It is concluded that, in structured self-report assessments, the most valid results may be obtained through the use of direct questions with cooperative test respondents. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)