Effect of Boron Addition on the Thermal Properties of Diamond-Particle-Dispersed Cu-Matrix Composites Fabricated by SPS

Abstract Diamond particle dispersed copper (Cu) matrix composites were fabricated from the powder mixture composed of diamond, pure-Cu and boron (B) by spark plasma sintering (SPS). The composites were consolidated at 1173 K for 600 s by SPS. The reaction between the diamond particle and the Cu matrix in the composite was not confirmed by SEM observation and X-ray diffraction (XRD) analysis. The relative packing density of the Cu/diamond composites increased with B addition and attained 93.2% -95.8% at the B content range between 1.8 vol.% and 13.8 vol.%. The thermal conductivity of the diamond-dispersed Cu composite drastically increased with B addition and reached the maximum value of 689 W/mK at 7.2 vol% B. Numerous transgranular fractures of diamond particles were observed on bending fracture surfaces of Cu-B/diamond composites. This indicates strong bonding between the diamond particle and the Cu matrix in the composite. The coefficient of thermal expansion of the composite falls in the upper line of Kerner's model

Neuroprotective effects of edaravone-administration on 6-OHDA-treated dopaminergic neurons

<p>Abstract</p> <p>Background</p> <p>Parkinson's disease (PD) is a neurological disorder characterized by the degeneration of nigrostriatal dopaminergic systems. Free radicals induced by oxidative stress are involved in the mechanisms of cell death in PD. This study clarifies the neuroprotective effects of edaravone (MCI-186, 3-methyl-1-phenyl-2-pyrazolin-5-one), which has already been used for the treatment of cerebral ischemia in Japan, on TH-positive dopaminergic neurons using PD model both <it>in vitro </it>and <it>in vivo</it>. 6-hydroxydopamine (6-OHDA), a neurotoxin for dopaminergic neurons, was added to cultured dopaminergic neurons derived from murine embryonal ventral mesencephalon with subsequet administration of edaravone or saline. The number of surviving TH-positive neurons and the degree of cell damage induced by free radicals were analyzed. In parallel, edaravone or saline was intravenously administered for PD model of rats receiving intrastriatal 6-OHDA lesion with subsequent behavioral and histological analyses.</p> <p>Results</p> <p><it>In vitro </it>study showed that edaravone significantly ameliorated the survival of TH-positive neurons in a dose-responsive manner. The number of apoptotic cells and HEt-positive cells significantly decreased, thus indicating that the neuroprotective effects of edaravone might be mediated by anti-apoptotic effects through the suppression of free radicals by edaravone. <it>In vivo </it>study demonstrated that edaravone-administration at 30 minutes after 6-OHDA lesion reduced the number of amphetamine-induced rotations significantly than edaravone-administration at 24 hours. Tyrosine hydroxylase (TH) staining of the striatum and substantia nigra pars compacta revealed that edaravone might exert neuroprotective effects on nigrostriatal dopaminergic systems. The neuroprotective effects were prominent when edaravone was administered early and in high concentration. TUNEL, HEt and Iba-1 staining <it>in vivo </it>might demonstrate the involvement of anti-apoptotic, anti-oxidative and anti-inflammatory effects of edaravone-administration.</p> <p>Conclusion</p> <p>Edaravone exerts neuroprotective effects on PD model both <it>in vitro and in vivo</it>. The underlying mechanisms might be involved in the anti-apoptotic effects, anti-oxidative effects, and/or anti-inflammatory effects of edaravone. Edaravone might be a hopeful therapeutic option for PD, although the high therapeutic dosage remains to be solved for the clinical application.</p

Controlled bulk polymerization of L-lactide and lactones by dual activation with organo-catalytic systems

The acid-base catalytic system based on N,N-dimethyl-4-aminopyridine (DMAP) and a protic acid that has already been revealed to be efficient for the ring-opening polymerization (ROP) of L-lactide in solution at room temperature was tested for the same polymerization in bulk at 100 degrees C. As observed in solution, the presence of the DMAP center dot HX (X Cl, CH3SO3, CF3 SO3) salt enhanced yields. Linear and star-like polylactides with 3 and 4 branches were prepared. Polylactides were thus easily prepared reaching high molar masses (up to 75 000 g mol(-1) for linear PLLA and 140 000 g mol(-1) for star-like PLLA) with good control in less than 1 h. In all cases, the appearance of transesterification reactions was shown to occur only at very high yield. The ROP of lactones (epsilon-caprolactone and delta-valerolactone) was also investigated with the same catalytic systems in bulk conditions. In contrast to lactide polymerization, only the DMAP/DMAP center dot HOTf allowed lactone polymerization with a slower rate. However, the control over the molar masses remained very good. Block copolymers were also synthesized