Fabrication of TiN Particle-Dispersed Al2O3 Composites Utilizing High N2-Pressure SHS

Fabrication of fine TiN particle-dispersed dense Al2O3 composites with the compositions of Al2O3/TiN=100/0~90/10 vol% has been conducted from Al2O3/(Ti,TiN0.3) mixed powder compacts by capsule-free hot isostatic pressing (HIP) utilizing high-pressure N2 SHS. Fine Ti powders (φ ~ 0.3 μm) with TiN0.3 phase were prepared by thermal decomposition of planetary ball-milled fine TiH2 powders at 400 °C (673 K) for 1 h in a vacuum, followed by heating in N2 at 200°C (473 K) for 2 h. The Al2O3 powder compacts (relative densities of 57.2-57.8%) with homogeneously dispersed (Ti,TiN0.3) particles were prepared. The mixed powder compacts were hot isostatically pressed (HIPed) under the conditions of 1350 °C (1623 K) at 7 MPa N2 for 1 h, followed by the heating at the same temperature for 2 h under 196 MPa-N2. At the first stage of heating [1350°C (1623K)/7MPa/1h], solid/gas reaction of SHS between (Ti,TiN0.3) and N2 was introduced to form TiN and densification of the Al2O3 powder compacts up to the relative density of 92-93% with closed pores was performed. And at the sequent second stage [1350 °C (1623K)/196MPa/2h], densification of the most of pre-sintered composites consisting of Al2O3 and TiN reached higher relative densities than 98.5%. Dispersion of TiN particles (~φ 0.30 μm) in the composites suppressed the grain growth of Al2O3 during HIP-sintering. Mechanical properties, such as bending strength (σb), Vickers hardness (HV), fracture toughness (K1C), and electrical resistivity (ρ) of the composites were evaluated as a function of TiN content; the maximum values of σb=640 MPa, HV=19.5 GPa, and KIC=4.5 MPa・m1/2 were obtained in the Al2O3/TiN=97/3~95/5 vol% composites. Among the composites, the lowest ρ value of 2.6×103 Ω・m was attained at Al2O3/TiN=90/10 vol% composite

Neurofeedback Using Real-Time Near-Infrared Spectroscopy Enhances Motor Imagery Related Cortical Activation

Accumulating evidence indicates that motor imagery and motor execution share common neural networks. Accordingly, mental practices in the form of motor imagery have been implemented in rehabilitation regimes of stroke patients with favorable results. Because direct monitoring of motor imagery is difficult, feedback of cortical activities related to motor imagery (neurofeedback) could help to enhance efficacy of mental practice with motor imagery. To determine the feasibility and efficacy of a real-time neurofeedback system mediated by near-infrared spectroscopy (NIRS), two separate experiments were performed. Experiment 1 was used in five subjects to evaluate whether real-time cortical oxygenated hemoglobin signal feedback during a motor execution task correlated with reference hemoglobin signals computed off-line. Results demonstrated that the NIRS-mediated neurofeedback system reliably detected oxygenated hemoglobin signal changes in real-time. In Experiment 2, 21 subjects performed motor imagery of finger movements with feedback from relevant cortical signals and irrelevant sham signals. Real neurofeedback induced significantly greater activation of the contralateral premotor cortex and greater self-assessment scores for kinesthetic motor imagery compared with sham feedback. These findings suggested the feasibility and potential effectiveness of a NIRS-mediated real-time neurofeedback system on performance of kinesthetic motor imagery. However, these results warrant further clinical trials to determine whether this system could enhance the effects of mental practice in stroke patients

Valid and reliable instruments for arm-hand assessment at ICF activity level in persons with hemiplegia: a systematic review

Contains fulltext : 110141.pdf (publisher's version ) (Open Access)BACKGROUND: Loss of arm-hand performance due to a hemiparesis as a result of stroke or cerebral palsy (CP), leads to large problems in daily life of these patients. Assessment of arm-hand performance is important in both clinical practice and research. To gain more insight in e.g. effectiveness of common therapies for different patient populations with similar clinical characteristics, consensus regarding the choice and use of outcome measures is paramount. To guide this choice, an overview of available instruments is necessary. The aim of this systematic review is to identify, evaluate and categorize instruments, reported to be valid and reliable, assessing arm-hand performance at the ICF activity level in patients with stroke or cerebral palsy. METHODS: A systematic literature search was performed to identify articles containing instruments assessing arm-hand skilled performance in patients with stroke or cerebral palsy. Instruments were identified and divided into the categories capacity, perceived performance and actual performance. A second search was performed to obtain information on their content and psychometrics. RESULTS: Regarding capacity, perceived performance and actual performance, 18, 9 and 3 instruments were included respectively. Only 3 of all included instruments were used and tested in both patient populations. The content of the instruments differed widely regarding the ICF levels measured, assessment of the amount of use versus the quality of use, the inclusion of unimanual and/or bimanual tasks and the inclusion of basic and/or extended tasks. CONCLUSIONS: Although many instruments assess capacity and perceived performance, a dearth exists of instruments assessing actual performance. In addition, instruments appropriate for more than one patient population are sparse. For actual performance, new instruments have to be developed, with specific focus on the usability in different patient populations and the assessment of quality of use as well as amount of use. Also, consensus about the choice and use of instruments within and across populations is needed

Tyrosine phosphorylation of guanosine triphosphatase activating protein by activation via surface IgG in human B cells

Abstract In this study, we analyzed tyrosine phosphorylation of guanosine triphosphatase (GTPase) activating protein in human B cells stimulated through surface IgG, using Western blot and immunoprecipitation. Stimulation through surface IgG induced the tyrosine phosphorylation of GTPase-activating protein (GAP) and two associated proteins, a 190-Kd protein and a 62-Kd protein, within 1 minute and in a dose-dependent manner. This tyrosine phosphorylation was blocked by Genistein (Extrasynthese, Genay, France). These data suggest that GTPase- activating protein is involved in a signal transduction pathway initiated from surface IgG in human B cells