Home About us Contact
|
Home About us Contact | ||
|
|
||
Mixed Gases (mixed + gase)
Selected AbstractsIntensified spin-dependent-transport and localized-spin freezing in magnetite sinter made from low size-dispersion hematite nanoparticles with low temperature calcinationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2006H. Kobori Abstract The spin-dependent-transport (SDT) has been studied for magnetite (Fe3O4) nano-particle sinter (MNPS) made from low size-dispersion hematite (,-Fe2O3) nanoparticles (LSDHN's) with low temperature calcination. Two kinds of LSDHN's are grown by the hydrothermal synthesis. The average sizes of them are 30 nm and 60 nm. The MNPS is produced by calcining the LSDHN's at 500 °C for 5 hours in the atmosphere of Ar(90%)/H2(10%) mixed gases. As compared with a bulk single crystal, the considerable intensification of negative-differential-magnetoresistance (ND-MR) has been observed for the MNPS. We have not observed abrupt change of the electrical resistivity in the vicinity of the temperature of the Verwey transition (which is the metal-insulator transition) appeared for a bulk single crystal. The ND-MR for 30 nm shows larger values than that of 60 nm on the temperature dependence. From the X-ray diffraction experiment, the MNPS is found to include crystalline magnetite regions. We consider that the MNPS is composed of large amorphous-like grain-boundaries and small crystalline grains. The electrical current is inferred to flow in grain-boundary regions. In grain-boundary regions, since the localized spins are relatively random distributed, the spin-polarized conduction electrons show the SDT. Below the Verwey temperature, we have observed the magnetization difference between zero-field cooling (ZFC) and field-cooling (FC). This phenomenon indicates that the localized spins in the amorphous-like grain-boundaries are frozen in some degree. Above the Verwey temperature, the magnetoresistance is well fitted by the square of the Langevin function. We consider that the localized spins in the amorphous-like grain-boundaries do not form perfectly random configuration and are somewhat ordered in a short range region. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reversal magnetoresistance and unusual localized-spin freezing in magnetite sinter made from low size-dispersion hematite nano-particles with high temperature calcinationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2006H. Kobori Abstract The magneto-resistance and magnetization have been studied for magnetite (Fe3O4) sinter made from low size-dispersion hematite (,-Fe2O3) nanoparticles (LSDHN's) with high temperature calcination. Two kinds of LSDHN's were grown by the hydrothermal synthesis. The average particle sizes of them are 30 nm and 60 nm. The magnetite sinter was produced by calcining the LSDHN's at 800 °C for 5 hours in the atmosphere of Ar(90%)/H2(10%) mixed gases. We have observed an abrupt change of the electrical resistivity by one order of magnitude in the vicinity of the Verwey temperature (123 K) of a bulk single crystal. From the X-ray diffraction experiment, we have found that the magnetite sinter includes crystalline region. The magnetite sinter is considered to be composed of relatively narrow grain-boundary regions of amorphous-like magnetite and large grain regions of crystalline magnetite. It is regarded that the grain-boundary-conduction is dominant below the Verwey temperature and the inter-grain-conduction is dominant above the Verwey temperature. We have observed the positive differential magnetoresistance (PD-MR) in low temperature regions and the negative differential magnetoresistance (ND-MR) in high temperature regions. The ND-MR is an ordinary phenomenon for magnetite, but the PD-MR is a peculiar one. In addition, an unusual localized-spin-freezing phenomenon has been also observed. Below the Verwey temperature, the magnetization difference between zero-field-cooling and field-cooling has been observed. The magnetization difference shows a sudden change in the vicinity of the Verwey temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Evaluation of transcutaneous CO2 responses following acute changes in PaCO2 in healthy subjectsRESPIROLOGY, Issue 3 2009Satoshi FUKE ABSTRACT Background and objective: Transcutaneous blood gas-monitoring systems with miniaturized SpO2 (peripheral blood oxygen saturation)/PCO2 combined sensors (TOSCATM) have been widely used. There are no reports of the inter- and intra-individual variability in transcutaneous measurements of PaCO2 (PtcCO2) in response to acute progressive changes in PaCO2. This study examined inter- and intra-individual variability of PtcCO2 measurements under semi-steady-state conditions, and characterized the behaviour of PtcCO2 in response to acute progressive changes in PaCO2. Methods: Subjects breathed mixed gases through a mouthpiece connected to an automatic arterial blood gas controller. Using end-tidal PCO2 and PO2 as guides, PaCO2 was controlled to increase and/or decrease between baseline and , 60 mm Hg, in a stepwise (n = 9) or progressive fashion (n = 6). Arterial blood was sampled when needed. Results: Intra-individual correlation coefficients between PtcCO2 and PaCO2 were excellent in all subjects (0.971,0.989); however, the slope of the regression line varied among subjects (1.040,1.335). Bias and limits of agreement (± 2 SD from bias) between PtcCO2 and PaCO2 were ,1.8 mm Hg and ,7.7 to 4.1 mm Hg. Changes in PtcCO2 in response to acute progressive changes in PaCO2 also varied among subjects. Conclusion: The PtcCO2 measurement system allows reliable estimation of PaCO2 in a given subject. However, caution is needed when comparing absolute values between subjects or when acute changes in PaCO2 occur. [source] Geochemical Characteristics and Origin of Natural Gases in the Qaidam Basin, ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2003ZHANG Xiaobao Abstract, Sixty-five natural gas samples were collected from 19 oil-gasfields in the Qaidam basin, China. The chemical composition and carbon isotope values of the samples were measured, and the geochemical characteristics and origin of the natural gases were studied. The gases can be divided into biogenic gases, sapropelic oil-type gases, mixed type oil-type gases, coal-type gases and mixed gas. The ,13C1 values of the biogenic gases are very small and the C2+ contents of them are very low, ranging from ,68.2± to ,61.8± and 0.06% to 0.20% respectively. They have heavy ,D and ,13Cco2. showing a CO2 reduction pathway. They are distributed in the East depression region and derived from the Quaternary source rocks. The sapropelic oil-type gases have small ,13C2 values and high C2+ ranging from ,36.6± to ,28.6± and from 33.01% to 47.15% respectively. The mixed type oil-type gases have ,13C2 values and C2+ contents varying from ,28.6± to ,24.8± and from 4.81% to 26.06% respectively. Both sapropelic oil-type gases and mixed type oil-type gases are associated with oil-type oils, distributed in the West depression region and derived from the Tertiary saltwater lacustrine sapropelic source rocks and humic source rocks respectively. The ,13C2 values of the coal-type gases are extremely high and the C2+ contents are very low, changing from ,23.3± to ,12.5± and from 0.06% to 18.07% respectively. The coal-type gases in the Nanbaxian gasfield and the Lenghu oil-gasfields in the North fault block belt are derived from the Middle Jurassic coal-measures source rocks, whereas those in the West depression region are derived from the Tertiary saltwater lacustrine humic source rocks. Compared with some other basins in China, the natural gases there have obviously heavier ,13C due to the heavier ,13C of different types of kerogens of the Tertiary saltwater lacustrine source rocks in the West depression region of the basin. The mixing of natural gases is common in the West depression region, but the mixed gases are formed by sapropelic oil-type gases, mixed type oil-type gases or coal-type gases, respectively, of different levels of maturity. Most of the sapropelic oil-type gases and mixed type oil-type gases in the west part are thermally immature and low-mature, but the coal-type gases in the West depression region and the North fault block belt are mature and high- to over-mature. [source] Development and evaluation of a simple calorimeter for the measurement of resting metabolismCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue S4 2002Toshiyo Tamura Summary 1.,A simple calorimeter based on the measurement of oxygen uptake has been developed. 2.,A respiratory simulator was used to evaluate oxygen uptake at different flow rates. A known concentration of mixed gases flows into the calorimeter via the respiratory simulator. Oxygen concentration and flow rate were measured and stored to memory for further analysis. 3.,Results indicate that large errors occur at low flow rates, but that the error is less than 5% under normal conditions. 4.,This device can be used to measure oxygen uptake under resting conditions. [source] | ||||||||||