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H Concentration (h + concentration)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Influence of laser crystallization on hydrogen bonding in poly-Si

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2008
N. H. Nickel
Abstract We investigate the influence of the hydrogen content in the amorphous starting material on hydrogen bonding and defect passivation in laser crystallized poly-Si using electron-spin-resonance and hydrogen effusion measurements. After laser dehydrogenation and crystallization the specimens contain a residual H concentration of 8×1021 cm,3 to 1.5×1022 cm,3. During a vacuum anneal at least 1.5×1021 cm,3 H atoms are mobile in the lattice, however, only about 3.7×1018 cm,3 H atoms passivate Si dangling-bonds. Our results show that the annealing treatment can cause the vast majority of H atoms to accumulate in H stabilized platelets. Since defect passivation preferentially occurs at grain boundaries and platelet nucleation and growth is confined to the interior of single crystal grains, H equilibration is governed by two spatially separated processes. Moreover, our data demonstrate that the hydrogen density-of-states distribution derived from H effusion data is dynamic and changes in response to experimental parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Microstructure of diamond-like carbon films prepared using acetylene and toluene by bipolar-type plasma based ion implantation

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2008
S. Nakao
Abstract Diamond-like carbon (DLC) films are deposited on Si substrates using acetylene (C2H2), toluene (C7H8) and their mixed gas, and the microstructures are examined by micro-Raman spectroscopy, Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) analysis as a function of negatively pulsed voltages (Vn). It is found that the formation of graphite-like structure (aromatic ring clustering) is enhanced with increasing Vn. In addition, the density of the films is increased up to approximately 2.0 g/cm3 and the H concentration is decreased with increasing Vn. The use of C2H2 has much effect on the formation of graphite-like structure and the reduction of H concentration in the films at high Vn as compared with others. The deposition rate of the films is increased with increasing Vn. Relatively high deposition rate is obtained when using C7H8. In the case of the mixed gas, the deposition rate is found to be close to that of C7H8. These results suggest that C7H8 is dominant to the deposition process when using the mixture of C2H2 + C7H8. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Malonate induces cell death via mitochondrial potential collapse and delayed swelling through an ROS-dependent pathway

BRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2005
Francisco J Fernandez-Gomez
1Herein we study the effects of the mitochondrial complex II inhibitor malonate on its primary target, the mitochondrion. 2Malonate induces mitochondrial potential collapse, mitochondrial swelling, cytochrome c (Cyt c) release and depletes glutathione (GSH) and nicotinamide adenine dinucleotide coenzyme (NAD(P)H) stores in brain-isolated mitochondria. 3Although, mitochondrial potential collapse was almost immediate after malonate addition, mitochondrial swelling was not evident before 15 min of drug presence. This latter effect was blocked by cyclosporin A (CSA), Ruthenium Red (RR), magnesium, catalase, GSH and vitamin E. 4Malonate added to SH-SY5Y cell cultures produced a marked loss of cell viability together with the release of Cyt c and depletion of GSH and NAD(P)H concentrations. All these effects were not apparent in SH-SY5Y cells overexpressing Bcl-xL. 5When GSH concentrations were lowered with buthionine sulphoximine, cytoprotection afforded by Bcl-xL overexpression was not evident anymore. 6Taken together, all these data suggest that malonate causes a rapid mitochondrial potential collapse and reactive oxygen species production that overwhelms mitochondrial antioxidant capacity and leads to mitochondrial swelling. Further permeability transition pore opening and the subsequent release of proapoptotic factors such as Cyt c could therefore be, at least in part, responsible for malonate-induced toxicity. British Journal of Pharmacology (2005) 144, 528,537. doi:10.1038/sj.bjp.0706069 [source]

Pharmacokinetics of clarithromycin in Helicobacter pylori eradication therapy in patients with liver cirrhosis

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2000
T. Azuma
Summary Background: Proton pump inhibitor triple therapy with clarithromycin and metronidazole has been widely used for Helicobacter pylori eradication. However, the efficacy and the safety of this therapy in patients with liver cirrhosis have not been established. Aim: To evaluate the effect of hepatic dysfunction on metabolism of clarithromycin as it is used for H. pylori eradication therapy in patients with liver cirrhosis, and the efficacy of eradication therapy in those patients. Methods: Serum levels of clarithromycin and its meta-bolite, 14-(R)-hydroxyclarithromycin, were examined in 18 subjects (five normal controls and 13 hospitalized patients with liver cirrhosis) on a selected day between days 7 and 10 of a 2-week course of eradication therapy. This therapy consisted of lansoprazole (30 mg, once a day) together with clarithromycin (200 mg, twice a day) and metronidazole (250 mg, twice a day). In addition, 118 H. pylori -positive out-patients, 88 with peptic ulcer and 30 with liver cirrhosis, underwent the same eradication therapy. Results: Values for the area under the 0,6 h concentration,time curve (AUC) for clarithromycin were not significantly different among the groups. However, the AUC (0,6 h) values of 14-(R)-hydroxyclarithromycin were significantly lower in the Child-Pugh C group than in either the normal controls or the Child-Pugh A/B group. The cure rate for the peptic ulcer patients was 84% on a per protocol analysis (95% CI: 80%,88%) and 81% on an intention-to-treat analysis (95% CI: 77%,85%), while in the liver cirrhosis patients it was 89% in a per protocol analysis (95% CI: 78%,99%) and 83% in an intention-to-treat analysis (95% CI: 70%,97%). Mild adverse effects were observed in 10% of the peptic ulcer patients and 13% of the liver cirrhosis patients, with none leading to premature withdrawal from the study. Conclusion: The 2-week low-dose lansoprazole-based triple therapy tested is a simple, effective and well-tolerated regimen for H. pylori eradication in patients with liver cirrhosis. [source]