Publications (3)4.08 Total impact
Article: Potential industrial applications of Al-based quasicrystals: plasma sprayed vs. HVOF sprayed coatings[show abstract] [hide abstract]
ABSTRACT: Quasicrystalline coatings with various aluminum based systems were deposited onto 304 stainless steel substrates using two thermal spraying techniques; plasma spraying and high velocity oxy-fuel spraying. The friction and wear performances of the coatings were evaluated using two different testing devices, varying testing conditions and counterpart materials. Values of the friction coefficient were found to be strongly dependent on the testing devices and the counterpart materials, with values ranging from 0.15 to 0.4. In testing conditions corresponding to high sliding velocity, this study showed that the contact problem was posed over a third body system due to the formation of an intermediate layer. Values of the coefficient of friction were found to be approximately the same for all coating layers regardless of the thermal spraying techniques used, however, larger differences were obtained in the wear performance. The tribological properties were also evaluated at high temperature. It is noted that quasicrystal coating layers exhibit better friction and wear performances at 450oC than at room temperature. In comparison to potential coating candidate such as Cr2O3 for piston rings in automotive engines, tribological property of quasicrystalline coating layers seems to be promising one, however, wear performance need to be improved.MRS Proceedings. 12/1999; 643.
Article: 4-Chloro-7-Trifluoromethyl-10H- Benzo[4,5]furo[3,2-b]Indole-1-Carboxylic Acid (TBIC), a Putative BKCa Channel Opener with Uterine Relaxant Activities[show abstract] [hide abstract]
ABSTRACT: In the present study, we examined the uterine relaxant activity of 4-chloro-7-trifluoromethyl-10H-benzo[4,5]furo[3,2-b]indole-1-carboxylic acid (TBIC), a putative opener of the large conductance Ca2+-activated K+ (BKCa) channel. TBIC concentration-dependently inhibited spontaneous uterine contractions (EC50 = 4.63 µmol/l; Emax = 94.85 ± 1.85%; 100 µmol/l, n = 6). It also reduced contractions induced by oxytocin (EC50 = 4.10 µmol/l; Emax = 84.3 ± 3.83%; 100 µmol/l, n = 6), prostaglandin F2α (EC50 = 2.14 µmol/l; Emax = 73.70 ± 5.21%; 100 µmol/l, n = 6) and acetylcholine (EC50 = 4.37 µmol/l; Emax = 83.67 ± 4.82; 100 µmol/l, n = 6). TBIC decreased KCl (20 mmol/l) -induced contractions (EC50 = 3.04 µmol/l; Emax = 94.0 ± 3.12%; 100 µmol/l, n = 6) indicating its K+ channel opening activity. BKCa channel blockers penitrem A (100 nmol/l) and tetraethylammonium chloride (1 mmol/l) attenuated the inhibitory activities of TBIC (p < 0.001) but not other K+ channel blockers such as barium chloride and glibenclamide (KIR and KATP channel blockers, respectively). These results demonstrate the uterine relaxant effects of TBIC in a mechanism of action largely referable to the potentiation of the BKCa channels. We have provided evidence for the potential use of TBIC as a tocolytic agent and support for the utility of BKCa channel openers in pathophysiologic conditions involving smooth muscle hyperactivity.Pharmacology 08/1970; 87(5-6):331-340. · 1.79 Impact Factor
Article: Comparative study of the tribological behavior of thermal sprayed quasicrystalline coating layers[show abstract] [hide abstract]
ABSTRACT: To investigate the role of tribological reactions on the friction and wear of quasicrystalline materials, coatings with two alloy compositions have been prepared by plasma and HVOF spraying techniques. The tribolayers were characterized by the formation of a transfer film on the counterface and densification of the coating subsurfaces. It was observed that the thickness of the transfer film and pore-free region were dependent on the composition and process used for the deposition of the coatings as well as the sliding velocity. As the sliding velocity increased, the growth rate of the transfer film decreased, resulting in a decrease of the coefficient of friction. On the other hand, the wear rate appeared to be controlled by the thickness of the pore-free region formed within the coating surface zone.Journal of Alloys and Compounds 342:321-325. · 2.29 Impact Factor