The Role of Eh in Nuclear Waste Form Dissolution

1983 ◽  
Vol 26 ◽  
Author(s):  
W. Phelps Freeborn ◽  
William B. White
Keyword(s):  
Redox Potential ◽  
Nuclear Waste ◽  
Palladium Catalyst ◽  
Platinum Electrode ◽  
Thermodynamic Calculations ◽  
Waste Form ◽  
Series Of Experiments ◽  
Rapid Kinetics

ABSTRACTA series of experiments was conducted to evaluate the significance of redox potential, Eh, as an independent opensystem variable in the dissolution of nuclear waste glasses and ceramics. The standard platinum electrode can be used in leach solutions. Measurements on couples with rapid kinetics such as Fe+++/Fe++ give results in agreement with thermodynamic calculations. Highly reducing leaching solutions can be obtained by passing hydrogen through the solvent in the presence of a palladium catalyst.

scholarly journals Methods of Simulating Low Redox Potential (Eh) for a Basalt Repository

1983 ◽  
Vol 26 ◽  
Author(s):  
Carol M. Jantzen
Keyword(s):  
Redox Potential ◽  
Nuclear Waste ◽  
Deionized Water ◽  
Waste Form ◽  
Laboratory Simulation ◽  
Redox Potentials ◽  
Waste Package ◽  
Leach Rate ◽  
Ph Conditions ◽  
Selection Of

ABSTRACTIn the selection of a repository for burying vitrified nuclear waste, the leach rate of the waste form in groundwater is of concern. Basaltic groundwaters have inherently low redox potentials which may affect the waste form leach rate. Laboratory simulation of the Eh-pH conditions to be found in a basalt repository can be achieved when crushed basalt is added to deoxygenated deionized water. The effects of other redoxactive waste package components, such as iron, were found to stabilize solution redox potential at different valves under oxic and anoxic conditions. When iron was present, different waste form leach rates were observed with and without oxygen.

scholarly journals Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

2021 ◽  
Author(s):  
Keisuke Saito ◽  
Minesato Nakagawa ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Photosystem Ii ◽  
Redox Potential ◽  
Quantum Chemical Calculations ◽  
Catalytic Reaction ◽  
Quantum Chemical ◽  
Ionic Radius ◽  
Redox Potentials ◽  
Oxygen Evolving ◽  
Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals  [M] ([M]  = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

Nitric oxide decreases lung liquid production via guanosine 3′,5′-cyclic monophosphate

2001 ◽  
Vol 280 (5) ◽  
pp. L923-L929 ◽  
Author(s):  
James J. Cummings ◽  
Huamei Wang
Keyword(s):  
Nitric Oxide ◽  
Pulmonary Epithelium ◽  
Fetal Sheep ◽  
Cgmp Analog ◽  
Pulmonary Arterial ◽  
Series Of Experiments ◽  
Lung Liquid ◽  
Tracer Dilution ◽  
Induced Changes

We studied the role of cGMP in nitric oxide (NO)-induced changes in lung liquid production ( J v ) in chronically instrumented fetal sheep. Forty-five studies were done in which J v was measured by a tracer dilution technique. Left pulmonary arterial flow (Qlpa) was measured by a Doppler flow probe. There were two series of experiments. In the first, we gave 8-bromo-cGMP, a cGMP analog, by either the pulmonary vascular or intraluminal route; in the second, we used agents to inhibit or enhance endogenous cGMP activity. When infused directly into the pulmonary circulation, 8-bromo-cGMP significantly increased Qlpa but had no effect on J v. Conversely, when instilled into the lung liquid, 8-bromo-cGMP had no effect on Qlpa but significantly reduced J v. Inhibition of guanylate cyclase activity with methylene blue totally blocked, whereas phosphodiesterase inhibition with Zaprinast significantly enhanced, the effect of instilled NO on J v. Thus the reduction in lung liquid caused by NO appears to be mediated by cGMP, perhaps through a direct effect on the pulmonary epithelium.

Rapid kinetics of second messenger production in bitter taste

1996 ◽  
Vol 270 (3) ◽  
pp. C926-C931 ◽  
Author(s):  
A. I. Spielman ◽  
H. Nagai ◽  
G. Sunavala ◽  
M. Dasso ◽  
H. Breer ◽  
...  
Keyword(s):  
Bitter Taste ◽  
Second Messengers ◽  
Second Messenger ◽  
Mouse Strains ◽  
Protective Mechanism ◽  
Transient Nature ◽  
Sucrose Octaacetate ◽  
Rapid Kinetics ◽  
First Time

The tasting of bitter compounds may have evolved as a protective mechanism against ingestion of potentially harmful substances. We have identified second messengers involved in bitter taste and show here for the first time that they are rapid and transient. Using a quench-flow system, we have studied bitter taste signal transduction in a pair of mouse strains that differ in their ability to taste the bitter stimulus sucrose octaacetate (SOA); however, both strains taste the bitter agent denatonium. In both strains of mice, denatonium (10 mM) induced a transient and rapid increase in levels of the second messenger inositol 1,4,5-trisphosphate (IP3) with a maximal production near 75-100 ms after stimulation. In contrast, SOA (100 microM) brought about a similar increase in IP3 only in SOA-taster mice. The response to SOA was potentiated in the presence of GTP (1 microM). The GTP-enhanced SOA-response supports a G protein-mediated response for this bitter compound. The rapid kinetics, transient nature, and specificity of the bitter taste stimulus-induced IP3 formation are consistent with the role of IP3 as a second messenger in the chemoelectrical transduction of bitter taste.

The Role of Colloids in Nuclear Waste Disposal

1983 ◽  
Vol 26 ◽  
Author(s):  
A. Avogadro ◽  
G.De Marsily
Keyword(s):  
Ground Water ◽  
Nuclear Waste ◽  
Waste Disposal ◽  
Column Experiments ◽  
Colloidal Transport ◽  
Container Material ◽  
Colloidal Fraction ◽  
Filtration Model

ABSTRACTAspects of formation and characterization of a radioactive colloidal fraction released by the waste form or produced by association with microcolloids naturally existing in ground water or produced either by corrosion of container material or by degradation of backfill material are discussed. A filtration model has been developed in order to describe colloidal transport under field conditions. Comparison between data obtained with laboratory column experiments and theoretical evaluations is presented.

The Role of Cutter Eccentricity on Surface Finish and Milling Forces

2004 ◽  
Author(s):  
Tony L. Schmitz ◽  
Jeremiah Couey ◽  
Eric Marsh ◽  
Michael F. Tummond
Keyword(s):  
Surface Finish ◽  
Milling Machine ◽  
Time Domain Simulation ◽  
Machined Surface ◽  
Premature Failure ◽  
Series Of Experiments ◽  
Error Motion ◽  
Milling Forces ◽  
Chip Load

In this paper, the role of milling cutter eccentricity, commonly referred to as runout, is explored to determine its effects on surface topography and milling forces. This work is motivated by the observation that commercially-available cutter bodies often exhibit variation in the teeth/insert radial locations as a result of manufacturing issues. Consequently, the chip load on individual cutting teeth varies periodically, which can lead to premature failure of the cutting edges. Additionally, this chip load variation increases the roughness of machined surfaces. This research isolates the effect of runout on cutting forces and the machined surface finish in a series of experiments completed on a precision milling machine with 0.1 μm positioning repeatability and 0.02 μm spindle error motion. The runout is varied in a controlled fashion and results compared between experiment and a comprehensive time-domain simulation.

Beaumont's Contribution to Gastric Psychophysiology: A Reappraisal

1988 ◽  
Vol 33 (7) ◽  
pp. 650-653 ◽  
Author(s):  
François M. Mai
Keyword(s):  
Gastric Emptying ◽  
Delayed Gastric Emptying ◽  
Bile Reflux ◽  
Emotional Arousal ◽  
Gastric Fistula ◽  
Physiological Changes ◽  
Digestive Process ◽  
Psychophysiological Research ◽  
Series Of Experiments

William Beaumont's monograph on the physiology of digestion which was first published in 1833, has become a classic in its field. In a series of experiments over a 10 year period on Alexis St. Martin, a 19 year old Canadian voyageur with a traumatic gastric fistula, Beaumont was the first to describe many important aspects of the digestive process. In two of the 238 experiments Beaumont noted gastric physiological changes induced by emotional arousal, these being bile reflux and delayed gastric emptying. Elsewhere in the book, but not in experimental context, Beaumont referred to non-specific changes in coloration and secretion of the mucous membrane induced by emotion. Modern gastric psychophysiological research has shown that emotional arousal increases, and withdrawal decreases, gastric acid secretion. It has also been shown conclusively that emotion can cause a reflux of bile into the stomach and it may delay gastric emptying. Although the main thrust of Beaumont's work was physiological, he must be credited with being the first investigator to draw attention to the role of emotional arousal in the digestive process.

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