scholarly journals U-loss associated with laser-heating of hematite and goethite in vacuum during (U–Th)/He dating and prevention using high O2 partial pressure

2020 ◽  
Vol 532 ◽  
pp. 119350 ◽  
Author(s):  
Florian Hofmann ◽  
Jonathan Treffkorn ◽  
Kenneth A. Farley
Keyword(s):  
Partial Pressure ◽  
Laser Heating ◽  
O2 Partial Pressure ◽  
High O2

Development of Reactive Ceramics for Conversion of Concentrated Solar Heat Into Solar Hydrogen With Two-Step Water-Splitting Reaction

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
H. Kaneko ◽  
S. Taku ◽  
Y. Naganuma ◽  
T. Ishihara ◽  
N. Hasegawa ◽  
...  
Keyword(s):  
Solid Solution ◽  
Partial Pressure ◽  
Water Splitting ◽  
Thermal Energy ◽  
Rapid Heating ◽  
Nonequilibrium State ◽  
Solar Thermal Energy ◽  
O2 Partial Pressure ◽  
High O2 ◽  
Institute Of Technology

The reactive ceramics suitable for the rotary-type solar reactor (proposed by Tokyo Institute of Technology, Tokyo) with two-step water-splitting reaction were developed. It is confirmed that O2 gas is evolved in the two-step water-splitting reaction with the reactive ceramics vigorously by rapid heating (α-O2-releasing reaction). The α-O2-releasing reaction is due to the formation of interstitial defect and the conversion of lattice oxygen into O2 gas at a nonequilibrium state. Reactive ceramics (NiFe2O4 and yttria stabilized zirconia (YSZ)-NiFe2O4 solid solution) can absorb solar thermal energy and convert thermal energy into chemical energy under high O2 partial pressure atmosphere in the α-O2-releasing reaction. Repetitive evolutions of O2 gas were observed in the two-step water-splitting reaction with YSZ-Fe3O4 solid solution and cerium based metal oxides (CeO2–NiO, CeO2–ZrO2, and CeO2–Ta2O5) at high O2 partial pressure. The CeO2–Ta2O5(Ce:Ta=90:10) released a large amount of O2 gas (3.95 cm3/g) in the α-O2 releasing reaction in the flow of air.

Fabrication of Pt-IrOx and Au-V2O5 Thin Films

2007 ◽  
Vol 345-346 ◽  
pp. 735-740 ◽  
Author(s):  
Richard P. Vinci ◽  
T. Bannuru ◽  
Seung Min Hyun ◽  
Walter L. Brown
Keyword(s):  
Thin Films ◽  
Partial Pressure ◽  
Oxygen Affinity ◽  
Thermodynamic Characteristics ◽  
Oxide Dispersion Strengthened ◽  
Oxygen Solubility ◽  
Post Annealing ◽  
O2 Partial Pressure ◽  
High O2 ◽  
Equilibrium Oxygen

Pt-IrOx and Au-V2O5 thin films were created by magnetron co-sputtering from multiple targets in an Ar-O2 mixture. Successful Pt-IrOx production required high O2 partial pressure and slow deposition rate followed by post-annealing in pure O2. In contrast, deposition of Au-V2O5 films required relatively low O2 partial pressure, and did not need any post-anneal. These different strategies for forming oxide dispersion strengthened films in a multi-target reactive sputtering configuration are directly related to the thermodynamic characteristics of the two materials systems. The most important characteristics are the low equilibrium oxygen solubility in Pt and Au, and the different degrees of oxygen affinity by Ir and V.

Separation of carotid body chemoreceptor responses to O2 and CO2 by oligomycin and by antimycin A

1982 ◽  
Vol 242 (3) ◽  
pp. C200-C206 ◽  
Author(s):  
E. Mulligan ◽  
S. Lahiri
Keyword(s):  
Steady State ◽  
Carbonic Anhydrase ◽  
Partial Pressure ◽  
Carotid Body ◽  
Body Tissue ◽  
Antimycin A ◽  
Tissue Ph ◽  
Co2 Partial Pressure ◽  
O2 Partial Pressure ◽  
Metabolic Hypothesis

The cat carotid chemoreceptor O2 and CO2 responses can be separated by oligomycin and by antimycin A. Both of these agents greatly diminish or abolish the chemoreceptor O2 response but not the nicotine or CO2 responses. After either oligomycin or antimycin, the responses to increases and decreases in arterial CO2 partial pressure (PaCO2) consisted of increases and decreases in activity characterized respectively by exaggerated overshoots and undershoots. These were eliminated by the carbonic anhydrase inhibitor, acetazolamide, suggesting that they resulted from changes in carotid body tissue pH. The steady-state PaCO2 response remaining after oligomycin was no longer dependent on arterial O2 partial pressure (PaO2). All effects of antimycin were readily reversible in about 20 min. The separation of the responses to O2 and CO2 indicates that there may be at least partially separate pathways of chemoreception for these two stimuli. The similarity of the oligomycin and antimycin results supports the metabolic hypothesis of chemoreception.

Interaction of hypoxia and hypercapnia on cerebral hemodynamics and brain electrical activity in dogs

1987 ◽  
Vol 253 (4) ◽  
pp. H890-H897 ◽  
Author(s):  
R. W. McPherson ◽  
D. Eimerl ◽  
R. J. Traystman
Keyword(s):  
Partial Pressure ◽  
Elevated Level ◽  
Severe Hypoxia ◽  
O2 Uptake ◽  
Animal Group ◽  
Moderate Hypoxia ◽  
Co2 Partial Pressure ◽  
Arterial Blood ◽  
O2 Partial Pressure ◽  
O2 Delivery

The interaction of hypoxic hypoxia, hypercapnia, and mean arterial blood pressure (MABP) was studied in 15 pentobarbital-anesthetized ventilated dogs. In one group of animals (n = 5) hypercapnia [arterial CO2 partial pressure (PaCO2) approximately 50 Torr] was added to both moderate hypoxia and severe hypoxia. Moderate hypoxia [arterial O2 partial pressure (PaO2) = 36 mmHg] increased MABP and cerebral blood flow (CBF) without changes in cerebral O2 uptake (CMRO2). Superimposed hypercapnia increased CBF and MABP further with no change in CMRO2. In another group of animals (n = 5), a MABP increase of approximately 40 mmHg during moderate hypoxia without hypercapnia did not further increase CBF, suggesting intact autoregulation. Thus, during moderate hypoxia, hypercapnia is capable of increasing CBF. Severe hypoxia (PaO2 = 22 mmHg) increased CBF, but MABP and CMRO2 declined. Superimposed hypercapnia further decreased MABP and decreased CBF from its elevated level and further decreased CMRO2. Raising MABP under these circumstances in another animal group (n = 5) increased CBF above the level present during severe hypoxia alone and increased CMRO2. The change in CBF and CMRO2 during severe hypoxia plus hypercapnia with MABP elevation were not different from that severe hypoxia alone. We conclude that, during hypoxia sufficiently severe to impair CMRO2, superimposed hypercapnia has a detrimental influence due to decreased MABP, which causes a decrease in CBF and cerebral O2 delivery.

scholarly journals Maximal exercise at extreme altitudes on Mount Everest

1983 ◽  
Vol 55 (3) ◽  
pp. 688-698 ◽  
Author(s):  
J. B. West ◽  
S. J. Boyer ◽  
D. J. Graber ◽  
P. H. Hackett ◽  
K. H. Maret ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Maximal Exercise ◽  
Ambient Air ◽  
O2 Uptake ◽  
Mount Everest ◽  
Air Breathing ◽  
Co2 Partial Pressure ◽  
O2 Partial Pressure ◽  
Low Levels ◽  
Arterial Po2

Maximal exercise at extreme altitudes was studied during the course of the American Medical Research Expedition to Everest. Measurements were carried out at sea level [inspired O2 partial pressure (PO2) 147 Torr], 6,300 m during air breathing (inspired PO2 64 Torr), 6,300 m during 16% O2 breathing (inspired PO2 49 Torr), and 6,300 m during 14% O2 breathing (inspired PO2 43 Torr). The last PO2 is equivalent to that on the summit of Mt. Everest. All the 6,300 m studies were carried out in a warm well-equipped laboratory on well-acclimatized subjects. Maximal O2 uptake fell dramatically as the inspired PO2 was reduced to very low levels. However, two subjects were able to reach an O2 uptake of 1 l/min at the lowest inspired PO2. Arterial O2 saturations fell markedly and alveolar-arterial PO2 differences increased as the work rate was raised at high altitude, indicating diffusion limitation of O2 transfer. Maximal exercise ventilations exceeded 200 l/min at 6,300 m during air breathing but fell considerably at the lowest values of inspired PO2. Alveolar CO2 partial pressure was reduced to 7-8 Torr in one subject at the lowest inspired PO2, and the same value was obtained from alveolar gas samples taken by him at rest on the summit. The results help to explain how man can reach the highest point on earth while breathing ambient air.

Effect of O2 Partial Pressure on Post Annealed Ba2YCU3O7-δ Thin Films

1992 ◽  
Vol 275 ◽  
Author(s):  
Julia M. PhUlips ◽  
M. P. Siegal ◽  
S. Y. Hou ◽  
T. H. Tiefel ◽  
J. H. Marshall
Keyword(s):  
Partial Pressure ◽  
Film Growth ◽  
Epitaxial Films ◽  
Pinning Force ◽  
Low Oxygen ◽  
O2 Partial Pressure ◽  
Growth Method ◽  
Lower Temperature ◽  
The Relationship

ABSTRACTEpitaxial films of Ba2YCu3O7-δ (BYCO) as thin as 250 å A and with Jc's approaching those of the best in situ grown films can be formed by co-evaporating BaF2, Y, and Cu followed by a two-stage anneal. These results extend the work on films > 2000 Å thick by R. Feenstra et al. [J. Appl. Phys. 69, 6569 (1991)]. High quality films of these thicknesses become possible if low oxygen partial pressure [p(O2) = 4.3 Torr] is used during the high temperature portion cf the anneal (Ta). The BYCO melt line is the upper limit for Ta. The use of low p(O2) shifts the window for stable BYCO film growth to lower temperature, which allows the formation of smooth films with greater microstructural disorder than is found in films grown in p(O2) = 740 Torr at higher Ta. The best films annealed in p(O2)=4.3 Torr have Jc values a factor of four higher than do comparable films annealed in P2=740 Torr. The relationship between the T required to grow films with the strongest pinning force and p(O2) is log independent of growth method (in situ or situ) over a range of five orders of magnitude of P(O2).

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