Interstitial distribution of charged macromolecules in the dog lung: a kinetic model.

PubMed

Parker, J C; Miniati, M; Pitt, R; Taylor, A E

1987-01-01

A mathematic model was constructed to investigate conflicting physiologic data concerning the charge effect of continuous capillaries to macromolecules in the lung. We simulated the equilibration kinetics of lactate dehydrogenase (MR 4.2 nM) isozymes LDH 1 (pI = 5.0) and LDH 5 (pI = 7.9) between plasma and lymph using previously measured permeability coefficients, lung tissue distribution volumes (VA) and plasma concentrations (CP) in lung tissue. Our hypothesis is that the fixed anionic charges in interstitium, basement membrane, and cell surfaces determine equilibration rather than charged membrane effects at the capillary barrier, so the same capillary permeability coefficients were used for both isozymes. Capillary filtration rates and protein fluxes were calculated using conventional flux equations. Initial conditions at baseline and increased left atrial pressures (PLA) were those measured in animal studies. Simulated equilibration of isozymes over 30 h in the model at baseline capillary pressures accurately predicted the observed differences in lymph/plasma concentration ratios (CL/CP) between isotopes at 4 h and equilibration of these ratios at 24 h. Quantitative prediction of isozyme CL/CP ratios was also obtained at increased PLA. However, an additional cation selective compartment representing the surface glycocalyx was required to accurately simulate the initial higher transcapillary clearances of cationic LDH 5. Thus experimental data supporting the negative barrier, positive barrier, and no charge barrier hypotheses were accurately reproduced by the model using only the observed differences in interstitial partitioning of isozymes without differences in capillary selectivity.

Density Relaxation of Liquid-Vapor Critical Fluids Examined in Earth's Gravity

NASA Technical Reports Server (NTRS)

Wilkinson, R. Allen

2000-01-01

This work shows quantitatively the pronounced differences between the density equilibration of very compressible dense fluids in Earth's gravity and those in microgravity. The work was performed onsite at the NASA Glenn Research Center at Lewis Field and is complete. Full details are given in references 1 and 2. Liquid-vapor critical fluids (e.g., water) at their critical temperature and pressure, are very compressible. They collapse under their own weight in Earth's gravity, allowing only a thin meniscus-like layer with the critical pressure to survive. This critical layer, however, greatly slows down the equilibration process of the entire sample. A complicating feature is the buoyancy-driven slow flows of layers of heavier and lighter fluid. This work highlights the incomplete understanding of the hydrodynamics involved in these fluids.

Case Report of a Hypobaric Chamber Fitness to Fly Test in a Child With Severe Cystic Lung Disease.

PubMed

Loo, Sarah; Campbell, Andrew; Vyas, Julian; Pillarisetti, Naveen

2017-07-01

Patients with severe cystic lung disease are considered to be at risk for cyst rupture during air travel because of the possibility of increase in cyst size and impaired equilibration of pressure between the cysts and other parts of the lung. This may have clinically devastating consequences for the patient but may also result in significant costs for emergency alteration of flight schedule. We report the use of a hypobaric chamber to simulate cabin pressure changes encountered on a commercial flight to assess the safety to fly of a child with severe cystic lung disease secondary to Langerhans cell histiocytosis. The test did not result in an air leak, and the child subsequently undertook air travel without mishap. This is the first reported use of a hypobaric chamber test in a child with severe cystic lung disease. This test has the potential to be used as a fitness to fly test in children at risk for air leak syndromes who are being considered for air travel. Copyright © 2017 by the American Academy of Pediatrics.

Termination of a Magnetized Plasma on a Neutral Gas: The End of the Plasma

NASA Astrophysics Data System (ADS)

Cooper, C. M.; Gekelman, W.

2013-06-01

Experiments are performed at the Enormous Toroidal Plasma Device at UCLA to study the neutral boundary layer (NBL) between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. This is the first experiment to measure plasma termination within a neutral gas without the presence of a wall or obstacle. A magnetized, current-free helium plasma created by a lanthanum hexaboride (LaB6) cathode terminates entirely within a neutral helium gas. The plasma is weakly ionized (ne/nn˜1%) and collisional λn≪Lplasma. The NBL occurs where the plasma pressure equilibrates with the neutral gas pressure, consistent with a pressure balance model. It is characterized by a field-aligned ambipolar electric field, developing self-consistently to maintain a current-free termination of the plasma on the neutral gas. Probes are inserted into the plasma to measure the plasma density, flow, temperature, current, and potential. These measurements confirm the presence of the ambipolar field and the pressure equilibration model of the NBL.

Critical Evaluation of Soil Pore Water Extraction Methods on a Natural Soil

NASA Astrophysics Data System (ADS)

Orlowski, Natalie; Pratt, Dyan; Breuer, Lutz; McDonnell, Jeffrey

2017-04-01

Soil pore water extraction is an important component in ecohydrological studies for the measurement of δ2H and δ18O. The effect of pore water extraction technique on resultant isotopic signature is poorly understood. Here we present results of an intercomparison of commonly applied lab-based soil water extraction techniques on a natural soil: high pressure mechanical squeezing, centrifugation, direct vapor equilibration, microwave extraction, and two types of cryogenic extraction systems. We applied these extraction methods to a natural summer-dry (gravimetric water contents ranging from 8% to 15%) glacio-lacustrine, moderately fine textured clayey soil; excavated in 10 cm sampling increments to a depth of 1 meter. Isotope results were analyzed via OA-ICOS and compared for each extraction technique that produced liquid water. From our previous intercomparison study among the same extraction techniques but with standard soils, we discovered that extraction methods are not comparable. We therefore tested the null hypothesis that all extraction techniques would be able to replicate the natural evaporation front in a comparable manner occurring in a summer-dry soil. Our results showed that the extraction technique utilized had a significant effect on the soil water isotopic composition. High pressure mechanical squeezing and vapor equilibration techniques produced similar results with similarly sloped evaporation lines. Due to the nature of soil properties and dryness, centrifugation was unsuccessful in obtaining pore water for isotopic analysis. Cryogenic extraction on both tested techniques produced similar results to each other on a similar sloping evaporation line, but dissimilar with depth.

Pressure equilibration in the penguin middle ear.

PubMed

Sadé, Jacob; Handrich, Yves; Bernheim, Joelle; Cohen, David

2008-01-01

King penguins have a venous structure in the form of a corpus cavernosum (CC) in their middle ear (ME) submucosa. The CC may be viewed as a special organelle that can change ME volume for pressure equilibration during deep-sea diving it is a pressure regulating organelle (PRO). A similar CC and muscles also surround the external ear (EE) and may constrict it, isolating the tympanic membrane from the outside. A CC was previously found also in the ME of marine diving mammals and can be expected to exist in other deep diving animals, such as marine turtles. Marine animals require equalization of middle ear (ME) pressure when diving hundreds or thousands of meters to catch prey. We investigated what mechanism enables king penguins to protect their ME when they dive to great depths. Biopsies and serial sections of the ME and the EE of the deep diving king penguin (Aptenodytes patagonicus) were examined microscopically. It was demonstrated that the penguin ME has an extensive network of small and large submucosal venous sinuses. This venous formation, a corpus cavernosum, can expand and potentially 'flood' the ME almost completely on diving, thus elevating ME pressure and reducing the ME space. The EE has a similar protective mechanism.

Organic-inorganic interactions at oil-water contacts: quantitative retracing of processes controlling the CO2 occurrence in Norwegian oil reservoirs

NASA Astrophysics Data System (ADS)

van Berk, Wolfgang; Schulz, Hans-Martin

2010-05-01

Crude oil quality in reservoirs can be modified by degradation processes at oil-water contacts (OWC). Mineral phase assemblages, composition of coexisting pore water, and type and amount of hydrocarbon degradation products (HDP) are controlling factors in complex hydrogeochemical processes in hydrocarbon-bearing siliciclastic reservoirs, which have undergone different degrees of biodegradation. Moreover, the composition of coexisting gas (particularly CO2 partial pressure) results from different pathways of hydrogeochemical equilibration. In a first step we analysed recent and palaeo-OWCs in the Heidrun field. Anaerobic decomposition of oil components at the OWC resulted in the release of methane and carbon dioxide and subsequent dissolution of feldspars (anorthite and adularia) leading to the formation of secondary kaolinite and carbonate phases. Less intensively degraded hydrocarbons co-occur with calcite, whereas strongly degraded hydrocarbons co-occur with solid solution carbonate phase (siderite, magnesite, calcite) enriched in δ13C. To test such processes quantitatively in a second step, CO2 equilibria and mass transfers induced by organic-inorganic interactions have been hydrogeochemically modelled in different semi-generic scenarios with data from the Norwegian continental shelf (acc. Smith & Ehrenberg 1989). The model is based on chemical thermodynamics and includes irreversible reactions representing hydrolytic disproportionation of hydrocarbons according to Seewald's (2006) overall reaction (1a) which is additionally applied in our modelling work in an extended form including acetic acid (1b): (1) R-CH2-CH2-CH3 + 4H2O -> R + 2CO2 + CH4 + 5H2, (2) R-CH2-CH2-CH3 + 4H2O -> R + 1.9CO2 + 0.1CH3COOH + 0.9CH4 + 5H2. Equilibrating mineral assemblages (different feldspar types, quartz, kaolinite, calcite) are based on the observed primary reservoir composition at 72 °C. Modelled equilibration and coupled mass transfer were triggered by the addition and reaction of different amounts of HDP. Modelled CO2 partial pressure values in a multicomponent gas phase equilibrated with K-feldspar, quartz, kaolinite, and calcite resemble measured data. Similar CO2 contents result from acetic acid addition (eq. 1b). Equilibration with albite or anorthite reduces the release of CO2 into the multicomponent gas phase dramatically, by 1 or 4 orders of magnitude compared with the equilibration with K-feldspar (van Berk et al., 2009). Third and based on data by Ehrenberg & Jakobsen (2001), the effects of organic-inorganic interactions at OWCs in Brent Group reservoir sandstones from the Gullfaks Oilfield (offshore Norway) have been hydrogeochemically modelled. Observed local changes in mineral phase assemblage compositions (content of different feldspar types, kaolinite, carbonate) and CO2 partial pressures are attributed to varying degrees of oil-biodegradation (up to more than 10 %; Horstadt et al. 1992). Modelling results are congruent with observations and indicate that (i) intense dissolution of anorthite, (ii) less intense dissolution of albite, (iii) minor dissolution of K-feldspar, (iv) intense precipitation of kaolinite and quartz, (v) less intense precipitation of carbonate, and (vi) formation of CO2 partial pressures are driven by the release of HDP. References Ehrenberg SN & Jakobsen KG (2001) Plagioclase dissolution related to biodegradation of oil in Brent Group sandstones (Middle Jurassic) of Gullfaks Field, northern North Sea. Sedimentology, 48, 703-721. Smith JT & Ehrenberg SN (1989) Correlation of carbon dioxide abundance with temperature in clastic hydrocarbon reservoirs: relationship to inorganic chemical equilibrium. Marine and Petroleum Geology, 6, 129-135. Seewald JS (2003) Organic-inorganic interactions in petroleum-producing sedimentary basins. Nature, 426, 327-333. van Berk, W, Schulz, H-M & Fu, Y (2009) Hydrogeochemical modelling of CO2 equilibria and mass transfer induced by organic-inorganic interactions in siliciclastic petroleum reservoirs. Geofluids, 9, 253-262.

The Effect of Pressure on Iron Speciation in Silicate Melts at a Fixed Oxygen Fugacity: The Possibility of a Redox Profile Through a Terrestrial Magma Ocean

NASA Astrophysics Data System (ADS)

Armstrong, K.; Frost, D. J.; McCammon, C. A.; Rubie, D. C.; Boffa Ballaran, T.

2017-12-01

As terrestrial planets accreted, mantle silicates equilibrated with core-forming metallic iron, which would have imposed a mantle oxygen fugacity below the iron-wüstite oxygen buffer. Throughout Earth's history, however, the oxygen fugacity of at least the accessible portions of the upper mantle has been 4-5 orders of magnitude higher. The process that caused the rapid increase in the redox state of the mantle soon after core formation is unclear. Here we test the possibility that pressure stabilises ferric iron in silicate melts, as has been observed in silicate minerals. A deep magma ocean, which would have likely existed towards the end of accretion, could then develop a gradient in oxygen fugacity for a fixed ferric-ferrous ratio as a result of pressure. We have equilibrated an andesitic melt with a Ru-RuO2 buffer in a multianvil press between 5 and 24 GPa. Further experiments were performed on the same melt in equilibrium with iron metal. The recovered melts were then analysed using Mössbauer spectroscopy to determine the ferric/ferrous ratio. The results show that for the Ru-RuO2 buffer at lower pressures, the ferric iron content decreases with pressure, due to a positive volume change of the reaction FeO + 1/4O2 = FeO1.5. Ferric iron content also appears to be sensitive to water content at lower pressures. However, above 15 GPa this trend apparently reverses and the ferric iron content increases with pressure. This reversal in pressure dependence would drive the oxygen fugacity of a deep magma ocean with a fixed ferric/ferrous ratio down with increasing depth. This would create a redox gradient, where the magma ocean could potentially be in equilibrium with metallic iron at its base but more oxidised in its shallower regions. Crystallisation of this magma ocean could render an upper mantle oxygen fugacity similar to that in the Earth's accessible mantle today.

Materials to Engineer the Immune System

DTIC Science & Technology

2010-04-01

presentation of danger signals to regulate the ratio of distinct DC subtypes was next examined by immobilizing TLR-activating, polyethylenimine (PEI...compression molded. The resulting disc was allowed to equilibrate within a high-pressure CO2 environment, and a rapid reduction in pressure causes the...pressure CO2 process to foam macroporous PLG matrices incorporating tumor lysates. To incorporate CpG-ODNs into PLG scaffolds, we first con- densed CpG-ODN

Airway exchange of highly soluble gases.

PubMed

Hlastala, Michael P; Powell, Frank L; Anderson, Joseph C

2013-03-01

Highly blood soluble gases exchange with the bronchial circulation in the airways. On inhalation, air absorbs highly soluble gases from the airway mucosa and equilibrates with the blood before reaching the alveoli. Highly soluble gas partial pressure is identical throughout all alveoli. At the end of exhalation the partial pressure of a highly soluble gas decreases from the alveolar level in the terminal bronchioles to the end-exhaled partial pressure at the mouth. A mathematical model simulated the airway exchange of four gases (methyl isobutyl ketone, acetone, ethanol, and propylene glycol monomethyl ether) that have high water and blood solubility. The impact of solubility on the relative distribution of airway exchange was studied. We conclude that an increase in water solubility shifts the distribution of gas exchange toward the mouth. Of the four gases studied, ethanol had the greatest decrease in partial pressure from the alveolus to the mouth at end exhalation. Single exhalation breath tests are inappropriate for estimating alveolar levels of highly soluble gases, particularly for ethanol.

Airway exchange of highly soluble gases

PubMed Central

Powell, Frank L.; Anderson, Joseph C.

2013-01-01

Highly blood soluble gases exchange with the bronchial circulation in the airways. On inhalation, air absorbs highly soluble gases from the airway mucosa and equilibrates with the blood before reaching the alveoli. Highly soluble gas partial pressure is identical throughout all alveoli. At the end of exhalation the partial pressure of a highly soluble gas decreases from the alveolar level in the terminal bronchioles to the end-exhaled partial pressure at the mouth. A mathematical model simulated the airway exchange of four gases (methyl isobutyl ketone, acetone, ethanol, and propylene glycol monomethyl ether) that have high water and blood solubility. The impact of solubility on the relative distribution of airway exchange was studied. We conclude that an increase in water solubility shifts the distribution of gas exchange toward the mouth. Of the four gases studied, ethanol had the greatest decrease in partial pressure from the alveolus to the mouth at end exhalation. Single exhalation breath tests are inappropriate for estimating alveolar levels of highly soluble gases, particularly for ethanol. PMID:23305981

Conversion of para and ortho hydrogen in the Jovian planets

NASA Technical Reports Server (NTRS)

Massie, S. T.; Hunten, D. M.

1982-01-01

A mechanism is proposed which partially equilibrates the para and ortho rotational levels of molecular hydrogen in the atmospheres of Jupiter, Saturn, and Uranus. Catalytic reactions between the free-radical surface sites of aerosol particles and hydrogen modecules yield significant equilibration near 1 bar pressure, if the efficiency of conversion per collision is between 10 to the -8th and 10 to the -10th and the effective eddy mixing coefficient is 10,000 sq cm/sec. At lower pressures the ortho-para ratio retains the value at the top of the cloud layer, except for a very small effect from conversion in the thermosphere. The influence of conversion on the specific heat and adiabatic lapse rate is also investigated. The effect is found to be generally small, though is can rise to 10% inside the aerosol layer.

Dynamic equilibration of airway smooth muscle contraction during physiological loading.

PubMed

Latourelle, Jeanne; Fabry, Ben; Fredberg, Jeffrey J

2002-02-01

Airway smooth muscle contraction is the central event in acute airway narrowing in asthma. Most studies of isolated muscle have focused on statically equilibrated contractile states that arise from isometric or isotonic contractions. It has recently been established, however, that muscle length is determined by a dynamically equilibrated state of the muscle in which small tidal stretches associated with the ongoing action of breathing act to perturb the binding of myosin to actin. To further investigate this phenomenon, we describe in this report an experimental method for subjecting isolated muscle to a dynamic microenvironment designed to closely approximate that experienced in vivo. Unlike previous methods that used either time-varying length control, force control, or time-invariant auxotonic loads, this method uses transpulmonary pressure as the controlled variable, with both muscle force and muscle length free to adjust as they would in vivo. The method was implemented by using a servo-controlled lever arm to load activated airway smooth muscle strips with transpulmonary pressure fluctuations of increasing amplitude, simulating the action of breathing. The results are not consistent with classical ideas of airway narrowing, which rest on the assumption of a statically equilibrated contractile state; they are consistent, however, with the theory of perturbed equilibria of myosin binding. This experimental method will allow for quantitative experimental evaluation of factors that were previously outside of experimental control, including sensitivity of muscle length to changes of tidal volume, changes of lung volume, shape of the load characteristic, loss of parenchymal support and inflammatory thickening of airway wall compartments.

CO2-ECBM related coupled physical and mechanical transport processes

NASA Astrophysics Data System (ADS)

Gensterblum, Yves; Satorius, Michael; Busch, Andreas; Krooß, Bernhard

2013-04-01

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH4, CO2) and inert gases (N2, Ar, He) on a sub bituminous A coal from the Surat Basin, Queensland Australia. From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected "true" permeability coefficients and the Klinkenberg slip factors were derived. The "true"-, absolute or Klinkenberg corrected permeability shows a gas type dependence. Following the approach of Seidle et al. (1992) the cleat volume compressibility (cf) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa we observe with increasing mean pressure at lower confining pressure an increase in permeability which we attribute to a cleat aperture widening. The cleat volume compressibility (cf) also shows a dependence on the mean pore pressure. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. This permeability hysteresis is in accordance with results reported by Harpalani and McPherson (1985). The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and "diffusion coefficients" were calculated using several unipore and bidisperse diffusion models. While the CH4 sorption capacity of moisture-equilibrated coals was significantly lower (by 50%) than of dry coals, no hysteresis was observed between sorption and desorption on dry and moisture-equilibrated samples and the sorption isotherms recorded for different particle sizes were essentially identical. The CH4 uptake rates were lower by a factor of two for moist coals than for dry coals. Busch, A., Gensterblum, Y., Krooss, B.M. and Siemons, N., 2006. Investigation of high-pressure selective adsorption/desorption behaviour of CO2 and CH4 on coals: An experimental study. International Journal of Coal Geology, 66(1-2): 53-68. Harpalani, S. and McPherson, M.J., 1985. Effect of stress on permeability of coal. Quarterly Review of methane from coal seams technology, 3(2): 23-29. Seidle, J.P., Jeansonne, M.W. and Erickson, D.J., 1992. Application of Matchstick Geometry to Stress-Dependent Permeability in Coals, SPE Rocky Mountain Regional Meeting, Casper, Wyoming.

CO2-ECBM related coupled physical and mechanical transport processes

NASA Astrophysics Data System (ADS)

Gensterblum, Y.; Sartorius, M.; Busch, A.; Cumming, D.; Krooss, B. M.

2012-04-01

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH4, CO2) and inert gases (N2, Ar, He) on a sub bituminous A coal from the Surat Basin, Queensland Australia. From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected "true" permeability coefficients and the Klinkenberg slip factors were derived. The "true"-, absolute or Klinkenberg corrected permeability shows a gas type dependence. Following the approach of Seidle et al. (1992) the cleat volume compressibility (cf) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa we observe with increasing mean pressure at lower confining pressure an increase in permeability which we attribute to a cleat aperture widening. The cleat volume compressibility (cf) also shows a dependence on the mean pore pressure. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. This permeability hysteresis is in accordance with results reported by Harpalani and McPherson (1985). The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and "diffusion coefficients" were calculated using several unipore and bidisperse diffusion models. While the CH4 sorption capacity of moisture-equilibrated coals was significantly lower (by 50%) than of dry coals, no hysteresis was observed between sorption and desorption on dry and moisture-equilibrated samples and the sorption isotherms recorded for different particle sizes were essentially identical. The CH4 uptake rates were lower by a factor of two for moist coals than for dry coals. Busch, A., Gensterblum, Y., Krooss, B.M. and Siemons, N., 2006. Investigation of high-pressure selective adsorption/desorption behaviour of CO2 and CH4 on coals: An experimental study. International Journal of Coal Geology, 66(1-2): 53-68. Harpalani, S. and McPherson, M.J., 1985. Effect of stress on permeability of coal. Quarterly Review of methane from coal seams technology, 3(2): 23-29. Seidle, J.P., Jeansonne, M.W. and Erickson, D.J., 1992. Application of Matchstick Geometry to Stress-Dependent Permeability in Coals, SPE Rocky Mountain Regional Meeting, Casper, Wyoming.

Ultrafast equilibration of excited electrons in dynamical simulations.

PubMed

Lin, Zhibin; Allen, Roland E

2009-12-02

In our density-functional-based simulations of materials responding to femtosecond-scale laser pulses, we have observed a potentially useful phenomenon: the excited electrons automatically equilibrate to a Fermi-Dirac distribution within ∼100 fs, solely because of their coupling to the nuclear motion, even though the resulting electronic temperature is one to two orders of magnitude higher than the kinetic temperature defined by the nuclear motion. Microscopic simulations like these can then provide the separate electronic and kinetic temperatures, chemical potentials, pressures, and nonhydrostatic stresses as input for studies on larger lengths and timescales.

High-pressure sorption of nitrogen, carbon dioxide, and their mixtures on Argonne Premium Coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreas Busch; Yves Gensterblum; Bernhard M. Krooss

2007-06-15

Gas sorption isotherms have been measured for carbon dioxide and nitrogen and their binary mixture (N{sub 2}/CO{sub 2} {approximately} 80/20) on three different moisture-equilibrated coals from the Argonne Premium Coal Sample Program by the U.S. Department of Energy, varying in rank from 0.25 to 1.68% vitrinite reflectance (VR{sub r}). The measurements were conducted at 55 C and at pressures up to 27 MPa for the pure gases and up to 10 MPa for the gas mixture. The effects of the large differences in equilibrium moisture contents (0.8 to 32.2%) on sorption capacity were estimated on the basis of the aqueousmore » solubility of CO{sub 2} and N{sub 2} at experimental conditions. Especially for the Beulah-Zap coal with an equilibrium moisture content of {approximately} 32%, the amount of dissolved CO{sub 2} contributes significantly to the overall storage capacity, whereas the amounts of N{sub 2} dissolved in the moisture water are low and can be neglected. Sorption measurements with nitrogen/carbon dioxide mixtures showed very low capacities for N{sub 2}. For Illinois coal, these excess sorption values were even slightly negative, probably due to small volumetric effects (changes in condensed phase volume). The evolution of the composition of the free gas phase in contact with the coal sample has been monitored continuously during each pressure step of the sorption tests. This composition changed strongly over time. Apparently, CO{sub 2} reaches sorption sites very quickly initially and is subsequently partly replaced by N{sub 2} molecules until concentration equilibration is reached. 18 refs., 10 figs., 2 tabs.« less

Sensitivities of Earth's core and mantle compositions to accretion and differentiation processes

NASA Astrophysics Data System (ADS)

Fischer, Rebecca A.; Campbell, Andrew J.; Ciesla, Fred J.

2017-01-01

The Earth and other terrestrial planets formed through the accretion of smaller bodies, with their core and mantle compositions primarily set by metal-silicate interactions during accretion. The conditions of these interactions are poorly understood, but could provide insight into the mechanisms of planetary core formation and the composition of Earth's core. Here we present modeling of Earth's core formation, combining results of 100 N-body accretion simulations with high pressure-temperature metal-silicate partitioning experiments. We explored how various aspects of accretion and core formation influence the resulting core and mantle chemistry: depth of equilibration, amounts of metal and silicate that equilibrate, initial distribution of oxidation states in the disk, temperature distribution in the planet, and target:impactor ratio of equilibrating silicate. Virtually all sets of model parameters that are able to reproduce the Earth's mantle composition result in at least several weight percent of both silicon and oxygen in the core, with more silicon than oxygen. This implies that the core's light element budget may be dominated by these elements, and is consistent with ≤1-2 wt% of other light elements. Reproducing geochemical and geophysical constraints requires that Earth formed from reduced materials that equilibrated at temperatures near or slightly above the mantle liquidus during accretion. The results indicate a strong tradeoff between the compositional effects of the depth of equilibration and the amounts of metal and silicate that equilibrate, so these aspects should be targeted in future studies aiming to better understand core formation conditions. Over the range of allowed parameter space, core and mantle compositions are most sensitive to these factors as well as stochastic variations in what the planet accreted as a function of time, so tighter constraints on these parameters will lead to an improved understanding of Earth's core composition.

Importance of equilibration time in the partitioning and toxicity of zinc in spiked sediment bioassays

USGS Publications Warehouse

Lee, J.-S.; Lee, B.-G.; Luoma, S.N.; Yoo, H.

2004-01-01

The influences of spiked Zn concentrations (1-40 ??mol/g) and equilibration time (???95 d) on the partitioning of Zn between pore water (PW) and sediment were evaluated with estuarine sediments containing two levels (5 and 15 ??mol/g) of acid volatile sulfides (AVS). Their influence on Zn bioavailability was also evaluated by a parallel, 10-d amphipod (Leptocheirus plumulosus) mortality test at 5, 20, and 85 d of equilibration. During the equilibration, AVS increased (up to twofold) with spiked Zn concentration ([Zn]), whereas Zn-simultaneously extracted metals ([SEM]; Zn with AVS) remained relatively constant. Concentrations of Zn in PW decreased most rapidly during the initial 30 d and by 11- to 23-fold during the whole 95-d equilibration period. The apparent partitioning coefficient (Kpw, ratio of [Zn] in SEM to PW) increased by 10- to 20-fold with time and decreased with spiked [Zn] in sediments. The decrease of PW [Zn] could be explained by a combination of changes in AVS and redistribution of Zn into more insoluble phases as the sediment aged. Amphipod mortality decreased significantly with the equilibration time, consistent with decrease in dissolved [Zn]. The median lethal concentration (LC50) value (33 ??M) in the second bioassay, conducted after 20 d of equilibration, was twofold the LC50 in the initial bioassay at 5 d of equilibration, probably because of the change of dissolved Zn speciation. Sediment bioassay protocols employing a short equilibration time and high spiked metal concentrations could accentuate partitioning of metals to the dissolved phase and shift the pathway for metal exposure toward the dissolved phase.

CREKID: A computer code for transient, gas-phase combustion of kinetics

NASA Technical Reports Server (NTRS)

Pratt, D. T.; Radhakrishnan, K.

1984-01-01

A new algorithm was developed for fast, automatic integration of chemical kinetic rate equations describing homogeneous, gas-phase combustion at constant pressure. Particular attention is paid to the distinguishing physical and computational characteristics of the induction, heat-release and equilibration regimes. The two-part predictor-corrector algorithm, based on an exponentially-fitted trapezoidal rule, includes filtering of ill-posed initial conditions, automatic selection of Newton-Jacobi or Newton iteration for convergence to achieve maximum computational efficiency while observing a prescribed error tolerance. The new algorithm was found to compare favorably with LSODE on two representative test problems drawn from combustion kinetics.

Application of photon Doppler velocimetry to direct impact Hopkinson pressure bars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lea, Lewis J., E-mail: ll379@cam.ac.uk; Jardine, Andrew P.

2016-02-15

Direct impact Hopkinson pressure bar systems offer many potential advantages over split Hopkinson pressure bars, including access to higher strain rates, higher strains for equivalent striker velocity and system length, lower dispersion, and faster achievement of force equilibrium. Currently, these advantages are gained at the expense of all information about the striker impacted specimen face, preventing the experimental determination of force equilibrium, and requiring approximations to be made on the sample deformation history. In this paper, we discuss an experimental method and complementary data analysis for using photon Doppler velocimetry to measure surface velocities of the striker and output barsmore » in a direct impact bar experiment, allowing similar data to be recorded as in a split bar system. We discuss extracting velocity and force measurements, and the precision of measurements. Results obtained using the technique are compared to equivalent split bar tests, showing improved stress measurements for the lowest and highest strains in fully dense metals, and improvement for all strains in slow and non-equilibrating materials.« less

Testing charm quark equilibration in ultrahigh-energy heavy ion collisions with fluctuations

NASA Astrophysics Data System (ADS)

Graf, Thorben; Steinheimer, Jan; Bleicher, Marcus; Herold, Christoph

2018-03-01

Recent lattice QCD data on higher order susceptibilities of charm quarks provide the opportunity to explore charm quark equilibration in the early quark gluon plasma (QGP) phase. Here, we propose to use the lattice data on second- and fourth-order net charm susceptibilities to infer the charm quark equilibration temperature and the corresponding volume, in the early QGP stage, via a combined analysis of experimentally measured multiplicity fluctuations. Furthermore, the first perturbative results for the second- and fourth-order charm quark susceptibilities and their ratio are presented.

Development and preliminary test of a new plateau hyperbaric chamber.

PubMed

Sun, Liang; Ding, Meng-jiang; Cai, Tian-cai; Fan, Hao-jun; Zhang, Jian-peng

2015-10-01

The objective of this study is to validate the performance, define its limits, and provide details on a new plateau hyperbaric chamber at 355-, 2880-, and 4532-m high altitude. A new multiplace plateau hyperbaric chamber was designed to satisfy the needed of patients who have acute mountain sickness. Tests were conducted inside the chamber at 355-, 2880-, and 4532-m high altitude. The safely and conveniences of the new plateau hyperbaric chamber were estimated. Minimum pressures of the main compartment can reach up to 0.029, 0.022, and 0.02 MPa at 355-, 2880-, and 4532-m high altitude. During pressurization, there was no leak of air around the chamber. The time lag of pressure equilibration between main and buffer compartment varies from 30.3±2.01 to 200.5±5.44 seconds and between buffer compartment and ambient pressure varies from 60.2±4.13 to 215.9±6.76 seconds. The chamber can be applicated for acute mountain sickness treatment safety and convenience. However, further experience about animals and human within the chamber is needed to improve the hardware and establish conditions of effective utilization of this equipment in the high altitude. Copyright © 2015. Published by Elsevier Inc.

42 CFR 84.207 - Bench tests; gas and vapor tests; minimum requirements; general.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 64 3 50 50 Ammonia Equilibrated NH3 1000 32 4 50 50 Chlorine As received Cl2 500 64 3 5 35 Chlorine... 4 5 50 Sulfur dioxide As received SO2 500 64 3 5 30 Sulfur dioxide Equilibrated SO2 500 32 4 5 30 1... respiratory protection against more than one type of gas or vapor, as for use in ammonia and in chlorine, the...

42 CFR 84.207 - Bench tests; gas and vapor tests; minimum requirements; general.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 64 3 50 50 Ammonia Equilibrated NH3 1000 32 4 50 50 Chlorine As received Cl2 500 64 3 5 35 Chlorine... 4 5 50 Sulfur dioxide As received SO2 500 64 3 5 30 Sulfur dioxide Equilibrated SO2 500 32 4 5 30 1... respiratory protection against more than one type of gas or vapor, as for use in ammonia and in chlorine, the...

Tank Pressure Control Experiment: Thermal Phenomena in Microgravity. Video 3 of 4

NASA Technical Reports Server (NTRS)

1996-01-01

The report presents the results of the flight experiment Tank Pressure Control Experiment/Thermal Phenomena (TPCE/TP) performed in the microgravity environment of the space shuttle. TPCE/TP, flown on the Space Transportation System STS-52, was a second flight of the Tank Pressure Control Experiment (TPCE). The experiment used Freon 113 at near saturation conditions. The test tank was filled with liquid to about 83 percent by volume. The experiment consisted of 21 tests. Each test generally started with a heating phase to increase the tank pressure and to develop temperature stratification in the fluid, followed by a fluid mixing phase for the tank pressure reduction and fluid temperature equilibration. The heating phase provided pool boiling data from large (relative to bubble sizes) heating surfaces (0.1046 m by 0.0742 m) at low heat fluxes (0.23 to 1.16 kW/m(exp 2)). The system pressure and the bulk liquid subcooling varied from 39 to 78 kPa and 1 to 3 deg C, respectively. The boiling process during the entire heating period, as well a jet-induced mixing process for the first 2 min. of the mixing period, was also recorded on video. Analyses of data from the two flight experiments (TPCE and TPCE/TP) and their comparison with the results obtained in drop tower experiments suggest that as Bond number approaches zero the flow pattern produced by an axial jet and the mixing time can be predicted by the Weber number. This is video 3 of 4.

Tank Pressure Control Experiment: Thermal Phenomena in Microgravity. Video 4 of 4

NASA Technical Reports Server (NTRS)

1996-01-01

The report presents the results of the flight experiment Tank Pressure Control Experiment/Thermal Phenomena (TPCE/TP) performed in the microgravity environment of the space shuttle. TPCE/TP, flown on the Space Transportation System STS-52, was a second flight of the Tank Pressure Control Experiment (TPCE). The experiment used Freon 113 at near saturation conditions. The test tank was filled with liquid to about 83 percent by volume. The experiment consisted of 21 tests. Each test generally started with a heating phase to increase the tank pressure and to develop temperature stratification in the fluid, followed by a fluid mixing phase for the tank pressure reduction and fluid temperature equilibration. The heating phase provided pool boiling data from large (relative to bubble sizes) heating surfaces (0.1046 m by 0.0742 m) at low heat fluxes (0.23 to 1.16 kW/m(exp 2)). The system pressure and the bulk liquid subcooling varied from 39 to 78 kPa and 1 to 3 deg C, respectively. The boiling process during the entire heating period, as well a jet-induced mixing process for the first 2 min. of the mixing period, was also recorded on video. Analyses of data from the two flight experiments (TPCE and TPCE/TP) and their comparison with the results obtained in drop tower experiments suggest that as Bond number approaches zero the flow pattern produced by an axial jet and the mixing time can be predicted by the Weber number. This is video 4 of 4.

Tank Pressure Control Experiment: Thermal Phenomena in Microgravity. Video 1 of 4

NASA Technical Reports Server (NTRS)

1996-01-01

The report presents the results of the flight experiment Tank Pressure Control Experiment/Thermal Phenomena (TPCE/TP) performed in the microgravity environment of the space shuttle. TPCE/TP, flown on the Space Transportation System STS-52, was a second flight of the Tank Pressure Control Experiment (TPCE). The experiment used Freon 113 at near saturation conditions. The test tank was filled with liquid to about 83 percent by volume. The experiment consisted of 21 tests. Each test generally started with a heating phase to increase the tank pressure and to develop temperature stratification in the fluid, followed by a fluid mixing phase for the tank pressure reduction and fluid temperature equilibration. The heating phase provided pool boiling data from large (relative to bubble sizes) heating surfaces (0.1046 m by 0.0742 m) at low heat fluxes (0.23 to 1.16 kW/m(exp 2)). The system pressure and the bulk liquid subcooling varied from 39 to 78 kPa and 1 to 3 deg C, respectively. The boiling process during the entire heating period, as well a jet-induced mixing process for the first 2 min. of the mixing period, was also recorded on video. Analyses of data from the two flight experiments (TPCE and TPCE/TP) and their comparison with the results obtained in drop tower experiments suggest that as Bond number approaches zero the flow pattern produced by an axial jet and the mixing time can be predicted by the Weber number. This is video 1 of 4.

Tank Pressure Control Experiment: Thermal Phenomena in Microgravity. Video 2 of 4

NASA Technical Reports Server (NTRS)

1996-01-01

The report presents the results of the flight experiment Tank Pressure Control Experiment/Thermal Phenomena (TPCE/TP) performed in the microgravity environment of the space shuttle. TPCE/TP, flown on the Space Transportation System STS-52, was a second flight of the Tank Pressure Control Experiment (TPCE). The experiment used Freon 113 at near saturation conditions. The test tank was filled with liquid to about 83 percent by volume. The experiment consisted of 21 tests. Each test generally started with a heating phase to increase the tank pressure and to develop temperature stratification in the fluid, followed by a fluid mixing phase for the tank pressure reduction and fluid temperature equilibration. The heating phase provided pool boiling data from large (relative to bubble sizes) heating surfaces (0.1046 m by 0.0742 m) at low heat fluxes (0.23 to 1.16 kW/m(exp 2)). The system pressure and the bulk liquid subcooling varied from 39 to 78 kPa and 1 to 3 deg C, respectively. The boiling process during the entire heating period, as well a jet-induced mixing process for the first 2 min. of the mixing period, was also recorded on video. Analyses of data from the two flight experiments (TPCE and TPCE/TP) and their comparison with the results obtained in drop tower experiments suggest that as Bond number approaches zero the flow pattern produced by an axial jet and the mixing time can be predicted by the Weber number. This is video 2 of 4.

Tolerance of brown bear spermatozoa to conditions of pre-freezing cooling rate and equilibration time.

PubMed

López-Urueña, E; Alvarez, M; Gomes-Alves, S; Martínez-Rodríguez, C; Borragan, S; Anel-López, L; de Paz, P; Anel, L

2014-06-01

Specific protocols for the cryopreservation of endangered Cantabrian brown bear spermatozoa are critical to create a genetic resource bank. The aim of this study was to assess the effect of cooling rates and equilibration time before freezing on post-thawed brown bear spermatozoa quality. Electroejaculates from 11 mature bears were extended to 100 × 10(6) spermatozoa/mL in a TES-Tris-Fructose-based extender, cryopreserved following performance of the respective cooling/equilibration protocol each sample was assigned to, and stored at -196 °C for further assessment. Before freezing, after thawing, and after 1 hour's incubation post-thawing at 37 °C (thermal stress test), the quality of the samples was assessed for motility by computer-assisted semen analysis, and for viability (SYBR-14/propidium iodide), acrosomal status (peanut agglutinin-fluorescein isothiocyanate /propidium iodide), and sperm chromatin stability (SCSA) by flow cytometry. In experiment 1, three cooling rates (0.25 °C/min, 1 °C/min, and 4 °C/min) to 5 °C were assessed. After thawing, total motility (%TM) was higher and percentage of damaged acrosomes (%dACR) was lower (P < 0.05) for 0.25 °C/min than for 4 °C/min. The thermal stress test data indicated equally poor quality (P < 0.05) for the 4 °C/min cooled samples in viability (%VIAB), %dACR, %TM, and progressive motility (%PM). In experiment 2, the effect of a pre-freezing equilibration period at 5 °C for 1 hour (cooling at 0.25 °C/min) was evaluated. Samples kept at 5 °C for 1 hour showed higher (P < 0.05) values than the nonequilibrated ones for both thawing (%dACR) and thermal stress test (%VIAB, %TM, and %PM). In experiment 3, samples stored without cooling and equilibration (direct freezing) were compared with the samples cooled at 0.25 °C/min and equilibrated for 1 hour (control freezing). Using thermal stress test, we observed that direct freezing causes damage in viability, acrosomal status, and motility of spermatozoa compared with the control group (P < 0.05). In conclusion, our results suggest that slow cooling rates to 5 °C and at least 1 hour equilibration time are necessary for the effective cryopreservation of brown bear sperm. Copyright © 2014 Elsevier Inc. All rights reserved.

Evaluation of alternative filter media for particulate matter emission testing of residential wood heating devices

DOE PAGES

Allen, George; Rector, Lisa; Butcher, Thomas; ...

2017-07-31

The performance of Teflon-coated glass fiber filter media (Pallflex Emfab TX40) is evaluated for particulate matter (PM) sampling of residential wood heating devices in a dilution tunnel. Thirty samples of varying duration and PM loading and concentration were collected from an U.S. Environmental Protection Agency (EPA) Method 28 dilution tunnel using dual Method 5G sample trains with untreated glass fiber and Emfab filters. Filters were weighed soon after the end of sampling and again the next day after equilibration at 35% relative humidity (RH). PM concentrations from both types of filters agreed very well with 1-day equilibration, demonstrating that Emfabmore » filters are appropriate for use in measuring PM from residential wood burning appliances in a dilution tunnel and have performance equal to or better than the glass fiber filter media. Agreement between filter media without equilibration was erratic, with PM from glass fiber filter samples varying from slightly less than the Emfab samples to as much as 2.8 times higher. Some of the glass fiber filters lost substantial mass with equilibration, with the highest percent loss at lower filter mass loadings. Mass loss for Emfab samples was a small percentage of the mass and very consistent across the range of mass loadings. Taken together, these results may indicate water uptake on the glass fiber media that is readily removed with 1-day equilibration at moderate RH conditions. Implications: EPA regulations now allow the use of either glass fiber or Teflon filter media for wood appliance PM emission testing. Teflon filter media minimizes the potential for acid-gas PM artifacts on glass fiber filters; this is important as EPA moves toward the use of locally sourced cordwood for testing that may have higher sulfur content. This work demonstrates that the use of Teflon-coated glass fiber filters can give similar PM measurement results to glass fiber filters after 1 day of equilibration. With no equilibration, measured PM from glass fiber filters was usually higher than from Teflon-coated glass fiber filters.« less

Evaluation of alternative filter media for particulate matter emission testing of residential wood heating devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, George; Rector, Lisa; Butcher, Thomas

The performance of Teflon-coated glass fiber filter media (Pallflex Emfab TX40) is evaluated for particulate matter (PM) sampling of residential wood heating devices in a dilution tunnel. Thirty samples of varying duration and PM loading and concentration were collected from an U.S. Environmental Protection Agency (EPA) Method 28 dilution tunnel using dual Method 5G sample trains with untreated glass fiber and Emfab filters. Filters were weighed soon after the end of sampling and again the next day after equilibration at 35% relative humidity (RH). PM concentrations from both types of filters agreed very well with 1-day equilibration, demonstrating that Emfabmore » filters are appropriate for use in measuring PM from residential wood burning appliances in a dilution tunnel and have performance equal to or better than the glass fiber filter media. Agreement between filter media without equilibration was erratic, with PM from glass fiber filter samples varying from slightly less than the Emfab samples to as much as 2.8 times higher. Some of the glass fiber filters lost substantial mass with equilibration, with the highest percent loss at lower filter mass loadings. Mass loss for Emfab samples was a small percentage of the mass and very consistent across the range of mass loadings. Taken together, these results may indicate water uptake on the glass fiber media that is readily removed with 1-day equilibration at moderate RH conditions. Implications: EPA regulations now allow the use of either glass fiber or Teflon filter media for wood appliance PM emission testing. Teflon filter media minimizes the potential for acid-gas PM artifacts on glass fiber filters; this is important as EPA moves toward the use of locally sourced cordwood for testing that may have higher sulfur content. This work demonstrates that the use of Teflon-coated glass fiber filters can give similar PM measurement results to glass fiber filters after 1 day of equilibration. With no equilibration, measured PM from glass fiber filters was usually higher than from Teflon-coated glass fiber filters.« less

Evaluation of Direct Vapour Equilibration for Stable Isotope Analysis of Plant Water.

NASA Astrophysics Data System (ADS)

Millar, C. B.; McDonnell, J.; Pratt, D.

2017-12-01

The stable isotopes of water (2H and 18O), extracted from plants, have been utilized in a variety of ecohydrological, biogeochemical and climatological studies. The array of methods used to extract water from plants are as varied as the studies themselves. Here we perform a comprehensive inter-method comparison of six plant water extraction techniques: direct vapour equilibration, microwave extraction, two unique versions of cryogenic extraction, centrifugation, and high pressure mechanical squeezing. We applied these methods to four isotopically unique plant portions (heads, stems, leaves and root crown) of spring wheat (Triticum aestivum L.). The spring wheat was grown under controlled conditions with irrigation inputs of a known isotopic composition. Our results show that the methods of extraction return significantly different plant water isotopic signals. Centrifugation, microwave extraction, direct vapour equilibration, and squeezing returned more enriched results. Both cryogenic systems and squeezing returned more depleted results, depending upon the plant portion extracted. While cryogenic extraction is currently the most widely used method in the literature, our results suggest that direct vapor equilibration method outperforms it in terms of accuracy, sample throughput and replicability. More research is now needed with other plant species (especially woody plants) to see how far the findings from this study could be extended.

Kinetics of bacterial potentiometric titrations: the effect of equilibration time on buffering capacity of Pantoea agglomerans suspensions.

PubMed

Kapetas, Leon; Ngwenya, Bryne T; Macdonald, Alan M; Elphick, Stephen C

2011-07-15

Several recent studies have made use of continuous acid-base titration data to describe the surface chemistry of bacterial cells as a basis for accurately modelling metal adsorption to bacteria and other biomaterials of potential industrial importance. These studies do not share a common protocol; rather they titrate in different pH ranges and they use different stability criteria to define equilibration time during titration. In the present study we investigate the kinetics of bacterial titrations and test the effect they have on the derivation of functional group concentrations and acidity constants. We titrated suspensions of Pantoea agglomerans by varying the equilibration time between successive titrant additions until stability of 0.1 or 0.001 mV s(-1) was attained. We show that under longer equilibration times, titration results are less reproducible and suspensions exhibit marginally higher buffering. Fluorescence images suggest that cell lysis is not responsible for these effects. Rather, high DOC values and titration reversibility hysterisis after long equilibration times suggest that variability in buffering is due to the presence of bacterial exudates, as demonstrated by titrating supernatants separated from suspensions of different equilibration times. It is recommended that an optimal equilibration time is always determined with variable stability control and preliminary reversibility titration experiments. Copyright © 2011 Elsevier Inc. All rights reserved.

Auxiliary Electrodes for Chromium Vapor Sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fergus, Jeffrey; Shahzad, Moaiz; Britt, Tommy

Measurement of chromia-containing vapors in solid oxide fuel cell systems is useful for monitoring and addressing cell degradation caused by oxidation of the chomia scale formed on alloys for interconnects and balance-of-plant components. One approach to measuring chromium is to use a solid electrolyte with an auxiliary electrode that relates the partial pressure of the chromium containing species to the mobile species in the electrolyte. One example is YCrO3 which can equilibrate with the chromium containing vapor and yttrium in yttria stabilized zirconia to establish an oxygen activity. Another is Na2CrO4 which can equilibrate with the chromium-containing vapor to establishmore » a sodium activity.« less

Response of local vascular volumes to lower body negative pressure stress

NASA Technical Reports Server (NTRS)

Wolthuis, R. A.; Leblanc, A.; Carpentier, W. A.; Bergman, S. A., Jr.

1975-01-01

The present study involved an intravenous injection of radioactive iodinated serum albumin, equilibration of this isotope within the vascular space, and the continuous measurement of isotope activity over selected anatomical areas before, during and following multiple human LBNP tests. Both rate and magnitude of vascular pooling were distinctly different within each of five selected lower body anatomical areas. In the upper body, all areas except the abdomen showed depletions from their resting vascular volumes during LBNP. The presence of uniquely different pooling patterns in the lower body, the apparent stability of abdominal vascular volumes, and a possible decrease in cerebral blood volume during LBNP represent the major findings of this study.

“Multi-temperature” method for high-pressure sorption measurements on moist shales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gasparik, Matus; Ghanizadeh, Amin; Gensterblum, Yves

2013-08-15

A simple and effective experimental approach has been developed and tested to study the temperature dependence of high-pressure methane sorption in moist organic-rich shales. This method, denoted as “multi-temperature” (short “multi-T”) method, enables measuring multiple isotherms at varying temperatures in a single run. The measurement of individual sorption isotherms at different temperatures takes place in a closed system ensuring that the moisture content remains constant. The multi-T method was successfully tested for methane sorption on an organic-rich shale sample. Excess sorption isotherms for methane were measured at pressures of up to 25 MPa and at temperatures of 318.1 K, 338.1more » K, and 348.1 K on dry and moisture-equilibrated samples. The measured isotherms were parameterized with a 3-parameter Langmuir-based excess sorption function, from which thermodynamic sorption parameters (enthalpy and entropy of adsorption) were obtained. Using these, we show that by taking explicitly into account water vapor as molecular species in the gas phase with temperature-dependent water vapor pressure during the experiment, more meaningful results are obtained with respect to thermodynamical considerations. The proposed method can be applied to any adsorbent system (coals, shales, industrial adsorbents) and any supercritical gas (e.g., CH{sub 4}, CO{sub 2}) and is particularly suitable for sorption measurements using the manometric (volumetric) method.« less

Metal-silicate Partitioning and Its Role in Core Formation and Composition on Super-Earths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaefer, Laura; Petaev, M. I.; Sasselov, Dimitar D.

We use a thermodynamic framework for silicate-metal partitioning to determine the possible compositions of metallic cores on super-Earths. We compare results using literature values of the partition coefficients of Si and Ni, as well as new partition coefficients calculated using results from laser shock-induced melting of powdered metal-dunite targets at pressures up to 276 GPa, which approaches those found within the deep mantles of super-Earths. We find that larger planets may have little to no light elements in their cores because the Si partition coefficient decreases at high pressures. The planet mass at which this occurs will depend on themore » metal-silicate equilibration depth. We also extrapolate the equations of state (EOS) of FeO and FeSi alloys to high pressures, and present mass–radius diagrams using self-consistent planet compositions assuming equilibrated mantles and cores. We confirm the results of previous studies that the distribution of elements between mantle and core will not be detectable from mass and radius measurements alone. While observations may be insensitive to interior structure, further modeling is sensitive to compositionally dependent properties, such as mantle viscosity and core freeze-out properties. We therefore emphasize the need for additional high pressure measurements of partitioning as well as EOSs, and highlight the utility of the Sandia Z-facilities for this type of work.« less

Time-dependent wellbore breakout growth caused by drilling-induced pore pressure transients: Implications for estimations of far field stress magnitude

NASA Astrophysics Data System (ADS)

Olcott, K. A.; Saffer, D. M.; Elsworth, D.

2013-12-01

One method used to constrain principal stress orientations and magnitudes in the crust combines estimates of rock strength with observations of wellbore failures, including drilling-induced tensile fractures (DITF) and compressional borehole breakouts (BO). This method has been applied at numerous Integrated Ocean Drilling Program (IODP) boreholes drilled into sediments in a wide range of settings, including the Gulf of Mexico, the N. Japan and Costa Rican subduction margins, and the Nankai Trough Accretionary Prism. At Nankai and N. Japan, BO widths defined by logging-while-drilling (LWD) resistivity images have been used to estimate magnitudes of far-field horizontal tectonic stresses. At several drillsites (C0010, C0002, and C0011), sections of the borehole were relogged with LWD after the hole was left open for times ranging from ~30 min to 3 days; times between acquisition were associated with pipe connections (~30 min), cleaning and circulating the hole (up to ~3 hr), and evacuation of the site for weather (~3 days). Relogged portions exhibit widening of BO, hypothesized to reflect time-dependent re-equilibration of instantaneous changes in pore fluid pressure (Pf) induced by opening the borehole. In this conceptual model, Pf decrease caused by initial excavation of the borehole and resulting changes in the state of stress at the borehole wall lead to an initial strengthening of the sediment. Re-equilibration of Pf results in time-dependent weakening of the sediment and subsequent BO growth. If correct, this hypothesis implies that stress magnitudes estimated by BO widths could be significantly underestimated. We test this idea using a finite-element model in COMSOL multiphysics that couples fluid flow and deformation in a poroelastic medium. We specify far-field horizontal principal stresses (SHmax and Shmin) in the model domain. At the start of simulations/at the time of borehole opening, we impose a decreased stress at the borehole wall. We consider a range of sediment permeability from 10-18 m2 to 10-14 m2. We find Pf initially increases at the borehole wall over a range of azimuths +/-~60° from Shmin, with a maximum increase of 10 MPa (4.4% of the maximum principal stress (σ1) at the borehole wall) and would lead to weakening of the rock. Pf decreases over a range of azimuths +/- ~30° from SHmax, with a maximum decrease of 10 MPa (8.8% of σ1), leading to initial strengthening of the rock. Evolution of Pf depends strongly on sediment permeability: Pf is 90% equilibrated at the borehole wall in ~43 minutes for a permeability of 10-18 m2, whereas for a permeability of 10-14 m2, Pf equilibrates nearly instantaneously. Since BO form parallel to Shmin, BO growth driven by drilling-induced Pf changes require that the initial BO be wider than ~120°, or outside the zone of initially increased Pf. This is not consistent with observations of BO growth, where initial BO are 0-25° and grow up to 125°. In contrast, our results imply that analyses based on BO measured immediately after drilling could overestimate far-field stresses because the BO are formed in sediments weakened by poroelastic pressure changes. Future work will focus on systematic investigation of the role of far field stresses and different sediment rheologies on the distribution of pore pressure change around the wellbore.

Defect chemistry and characterization of Hg(1-x)Cd(x)Te

NASA Technical Reports Server (NTRS)

Vydyanath, H. R.

1981-01-01

Undoped mercury cadmium telluride crystals were subjected to high temperature equilibration at temperatures ranging from 400 C to 655 C in various Hg atmospheres. Hall effect and mobility measurements were carried out on the crystals quenched to room temperature subsequent to the high temperature equilibration. The variation of the hole concentration in the cooled crystals at 77 K as a function of the partial pressure of Hg at the equlibration temperatures, together with a comparison of the hole mobility in the undoped samples with that in the copper and phosphorous doped samples yielded a defect model for the undoped crystals, according to which, the undoped crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. Native donor defects appear to be negligible in concentration, implying that the p to n conversion in these alloys is mainly due to residual foreign donor impurities. The thermodynamic constants for the intrinsic excitation process as well as for the incorporation of the doubly ionized native acceptor defects in the undoped crystals were obtained.

Thermobarometry of mafic igneous rocks based on clinopyroxene-liquid equilibria, 0 30 kbar

NASA Astrophysics Data System (ADS)

Putirka, K.; Johnson, Marie; Kinzler, Rosamond; Longhi, John; Walker, David

1996-02-01

Models for estimating the pressure and temperature of igneous rocks from co-existing clino-pyroxene and liquid compositions are calibrated from existing data and from new data obtained from experiments performed on several mafic bulk compositions (from 8 30 kbar and 1100 1475° C). The resulting geothermobarometers involve thermodynamic expressions that relate temperature and pressure to equilibrium constants. Specifically, the jadeite (Jd; NaAlSi2O6) diopside/hedenbergite (DiHd; Ca(Mg, Fe) Si2O6) exchange equilibrium between clinopyroxene and liquid is temperature sensitive. When compositional corrections are made to the calibrated equilibrium constant the resulting geothermometer is (i) 104 T=6.73-0.26* ln [Jdpx*Caliq*FmliqDiHdpx*Naliq*Alliq] -0.86* ln [MgliqMgliq+Feliq]+0.52*ln [Caliq] an expression which estimates temperature to ±27 K. Compared to (i), the equilibrium constant for jadeite formation is more sensitive to pressure resulting in a thermobarometer (ii) P=-54.3+299* T104+36.4* T104 ln [Jdpx[Siliq]2*Naliq*Alliq] +367*[Naliq*Alliq] which estimates pressure to ± 1.4 kbar. Pressure is in kbar, T is in Kelvin. Quantities such as Naliq represent the cation fraction of the given oxide (NaO0.5) in the liquid and Fm=MgO+FeO. The mole fractions of Jd and diopside+hedenbergite (DiHd) components are calculated from a normative scheme which assigns the lesser of Na or octahedral Al to form Jd; any excess AlVI forms Calcium Tschermak’s component (CaTs; CaAlAlSiO6); Ca remaining after forming CaTs and CaTiAl2O6 is taken as DiHd. Experimental data not included in the regressions were used to test models (i) and (ii). Error on predictions of T using model (i) is ±40 K. A pressure-dependent form of (i) reduces this error to ±30 K. Using model (ii) to predict pressures, the error on mean values of 10 isobaric data sets (0 25 kbar, 118 data) is ±0.3 kbar. Calculating thermodynamic properties from regression coefficients in (ii) gives VJd f of 23.4 ±1.3 cm3/mol, close to the value anticipated from bar molar volume data (23.5 cm3/mol). Applied to clinopyroxene phenocrysts from Mauna Kea, Hawaii lavas, the expressions estimate equilibration depths as great as 40 km. This result indicates that transport was sufficiently rapid that at least some phenocrysts had insufficient time to re-equilibrate at lower pressures.

42 CFR Appendix - Tables to Subpart L of Part 84

Code of Federal Regulations, 2014 CFR

2014-10-01

....) Number of tests Penetration 1 (p.p.m.) Minimum life 2 (min.) Ammonia As received NH3 1000 64 3 50 50 Ammonia Equilibrated NH3 1000 32 4 50 50 Chlorine As received Cl2 500 64 3 5 35 Chlorine Equilibrated Cl2... life shall be one-half that shown for each type of gas or vapor. Where a respirator is designed for...

42 CFR Appendix - Tables to Subpart L of Part 84

Code of Federal Regulations, 2012 CFR

2012-10-01

....) Number of tests Penetration 1 (p.p.m.) Minimum life 2 (min.) Ammonia As received NH3 1000 64 3 50 50 Ammonia Equilibrated NH3 1000 32 4 50 50 Chlorine As received Cl2 500 64 3 5 35 Chlorine Equilibrated Cl2... life shall be one-half that shown for each type of gas or vapor. Where a respirator is designed for...

42 CFR Appendix - Tables to Subpart L of Part 84

Code of Federal Regulations, 2013 CFR

2013-10-01

....) Number of tests Penetration 1 (p.p.m.) Minimum life 2 (min.) Ammonia As received NH3 1000 64 3 50 50 Ammonia Equilibrated NH3 1000 32 4 50 50 Chlorine As received Cl2 500 64 3 5 35 Chlorine Equilibrated Cl2... life shall be one-half that shown for each type of gas or vapor. Where a respirator is designed for...

PHOTOMETRIC EVIDENCE FOR THE OSMOTIC BEHAVIOR OF RAT LIVER MICROSOMES

PubMed Central

Tedeschi, Henry; James, Joseph M.; Anthony, William

1963-01-01

Electron microscope observations are consistent with the interpretation that the elements of the endoplasmic reticulum are osmotically active in situ as well as after isolation. More recently, it has been reported that microsomal suspensions equilibrate almost completely with added C14-sucrose and that no osmotic behavior is evident from photometric data. These findings were considered at variance with the electron microscope data. However, equilibration with added label simply attests to a relatively high permeability, and, in addition, the photometric data need not be critical. Osmotic volume changes, measured photometrically, may be masked by concomitant events (e.g., changes in the refractive index of the test solutions at varying osmotic pressures, breakdown of the particles, and agglutination). For these reasons the photometric experiments were repeated. In this work, the reciprocal of optical density of microsomal suspensions was found to vary linearly with the reciprocal of concentration of the medium at constant refractive index. These changes probably correspond to osmotic volume changes, since the effect was found to be (a) independent of substance used and (b) osmotically reversible. The transmission of the suspension was found to vary with the refractive index of the medium, the concentration of particles, and the wavelength of incident light, according to relationships that are similar to or identical with those obtained for mitochondrial suspensions. PMID:14064105

Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone.

PubMed

Satsukawa, Takako; Griffin, William L; Piazolo, Sandra; O'Reilly, Suzanne Y

2015-11-13

Investigations of the Mantle Transition Zone (MTZ; 410-660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context.

Vocal function and upper airway thermoregulation in five different environmental conditions.

PubMed

Sandage, Mary J; Connor, Nadine P; Pascoe, David D

2014-02-01

Phonation threshold pressure and perceived phonatory effort were hypothesized to increase and upper airway temperature to decrease following exposure to cold and/or dry air. Greater changes were expected with mouth versus nose breathing. In a within-participant repeated measures design, 15 consented participants (7 men, 8 women) completed 20-min duration trials to allow for adequate thermal equilibration for both nose and mouth breathing in 5 different environments: 3 temperatures (°C) matched for relative humidity (% RH), cold (15 °C, 40% RH), thermally neutral (25 °C, 40% RH), and hot (35 °C, 40% RH); and 2 temperatures with variable relative humidity to match vapor pressure for the neutral environment (25 °C, 40% RH), cold (15 °C, 74% RH) and hot (35 °C, 23% RH). Following each equilibration trial, measures were taken in this order: upper airway temperature (transnasal thermistor probe), phonation threshold pressure, and perceived phonatory effort. Data were analyzed using repeated measures analysis of variance, and no significant differences were established. The study hypotheses were not supported. Findings suggest that the upper airway is tightly regulated for temperature when challenged by a realistic range of temperature and relative humidity environments. This is the first study of its kind to include measurement of upper airway temperature in conjunction with measures of vocal function.

Multiple Reaction Geobarometry for Gabbroic Rocks

NASA Astrophysics Data System (ADS)

Ziberna, L.; Green, E. C. R.; Blundy, J. D.

2016-12-01

Gabbroic rocks are fundamental constituents of the Earth's crust. Given that they can form over a wide range of depths, from the base of the crust to shallow magma storage zones, estimating the pressure (P) of formation of any gabbroic rock found either in exposed crustal sections or as xenolith included in magmas is critically important. Model errors of commonly used geobarometers for gabbroic rocks are > 3 kbar (standard error of estimate), which is unhelpfully high considering the typical P range to be investigated (e.g., < 10 kbar for island arcs). Most likely, the difficulty to extract a clear P signal is partly related to the fact that most thermobarometers use either empirical formulations based on the composition of a single phase, or a single reaction involving only two phases, the latter being often characterized by a relatively low volume change. A multiple-reaction approach employing an internally consistent thermodynamic dataset potentially offers more precise results, as it allows all of the pressure and temperature information in a mineral assemblage for which thermodynamic models exist to be used simultaneously. In this work we evaluated the reliability of the average P method (avP; a multiple-reaction method included in thermocalc; Powell & Holland, 2008, J. Metamorphic Geol. 26, 155-179), applied using some of the latest internally-consistent dataset and activity-composition relations (e.g., Green et al. 2016; doi:10.1111/jmg.12211). The avP method uses a least square minimization technique to calculate the optimal P, taking into account the correlated uncertainties in the pressures predicted by each reaction in an independent set. We tested the method and thermodynamic models using a dataset of phase equilibrium experiments in basaltic systems and well-equilibrated natural samples from a variety of geodynamic settings. We then made minor modifications to the activity-composition models and thermodynamic properties of clinopyroxene and spinel in order to improve the accuracy and precision of the results given by avP. Thanks to the careful selection of experimental data and assessment of the diagnostic utilities in thermocalc, our approach is capable of calculating pressures with 1σ uncertainties < 1.5 kbar for natural assemblages equilibrated in the range 1.0-9.0 kbar.

Boron Diffusion in Surface-Treated Framing Lumber

Treesearch

Patricia K. Lebow; Stan T. Lebow; Steven A. Halverson

2013-01-01

The extent of boron penetration in framing lumber treated by spray applications during construction is not well quantified. This study evaluated the effect of formulation and concentration on diffusion of boron in lumber specimens that were equilibrated in conditions that produced wood moisture contents of 18 to 21 percent. One set of specimens was pressure treated...

Core formation in the shergottite parent body and comparison with the earth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Treiman, A.H.; Jones, J.H.; Drake, M.J.

1987-03-30

The mantle of the shergottite parent body (SPB) is depleted relative to the bulk SPB in siderophile and chalcophile elements; these elements are inferred to reside in the SPB's core. Our chemical model of these depletions rests on a physically plausible process of segregation of partially molten metal form partially molten silicates as the SPB grows and is heated above silicate and metallic solidi during accretion. Metallic and silicate phases equilibrate at low pressures as new material is accreted to the SPB surface. Later movement of the metallic phases to the planet's center is so rapid that high-pressure equilibration ismore » insignificant. Partitioning of siderophile and chalcophile elements among solid and liquid metal and silicate determines their abundances in the SPB mantle. Using partition coefficients and the SPB mantle composition determined in earlier studies, we model the abundances of Ag, Au, Co, Ga, Mo, Ni, P, Re, S, and W with free parameters being oxygen fugacity, proportion of solid metal formed, proportion of metallic liquid formed, and proportion of silicate that is molten.« less

Shock Re-equilibration of Fluid Inclusions

NASA Technical Reports Server (NTRS)

Madden, M. E. Elwood; Horz, F.; Bodnar, R. J.

2004-01-01

Fluid inclusions (microscopic volumes of fluid trapped within minerals as they precipitate) are extremely common in terrestrial minerals formed under a wide range of geological conditions from surface evaporite deposits to kimberlite pipes. While fluid inclusions in terrestrial rocks are nearly ubiquitous, only a few fluid inclusion-bearing meteorites have been documented. The scarcity of fluid inclusions in meteoritic materials may be a result of (a) the absence of fluids when the mineral was formed on the meteorite parent body or (b) the destruction of fluid inclusions originally contained in meteoritic materials by subsequent shock metamorphism. However, the effects of impact events on pre-existing fluid inclusions trapped in target and projectile rocks has received little study. Fluid inclusions trapped prior to the shock event may be altered (re-equilibrated) or destroyed due to the high pressures, temperatures, and strain rates associated with impact events. By examining the effects of shock deformation on fluid inclusion properties and textures we may be able to better constrain the pressure-temperature path experienced by terrestrial and meteoritic shocked materials and also gain a clearer understanding of why fluid inclusions are rarely found in meteorite samples.

Effect of storage temperature and equilibration time on polymethyl methacrylate (PMMA) bone cement polymerization in joint replacement surgery.

PubMed

Koh, Bryan T H; Tan, J H; Ramruttun, Amit Kumarsing; Wang, Wilson

2015-11-17

In cemented joint arthroplasty, the handling characteristics (doughing, working, and setting times) of polymethyl methacrylate (PMMA) bone cement is important as it determines the amount of time surgeons have to optimally position an implant. Storage conditions (temperature and humidity) and the time given for PMMA cement to equilibrate to ambient operating theater (OT) temperatures are often unregulated and may lead to inconsistencies in its handling characteristics. This has not been previously studied. Hence, the purpose of this study was to investigate the effect of storage temperatures on the handling characteristics of PMMA cement and the duration of equilibration time needed at each storage temperature to produce consistent and reproducible doughing, setting, and working times. SmartSet® HV cement was stored at three different controlled temperatures: 20 °C (control), 24 °C, and 28 °C for at least 24 h prior to mixing. The cement components were then brought into a room kept at 20 °C and 50 % humidity. Samples were allowed to equilibrate to ambient conditions for 15, 30, 45, and 60 min. The cement components were mixed and the dough time, temperature-versus-time curve (Lutron TM-947SD, Lutron Electronics, Inc., Coopersburg, PA), and setting time were recorded. Analysis was performed using the two-way ANOVA test (IBM SPSS Statistics V.22). At 20 °C (control) storage temperature, the mean setting time was 534 ± 17 s. At 24 °C storage temperature, the mean setting time was 414 ± 6 s (p < 0.001*) with 15 min of equilibration, 446 ± 11 s (p < 0.001*) with 30 min of equilibration, 501 ± 12 s (p < 0.001*) with 45 min of equilibration, and 528 ± 15 (p > 0.05) with 60 min of equilibration. At 28 °C storage temperature, the mean setting time was 381 ± 8 s (p < 0.001*) with 15 min of equilibration, 432 ± 30 s (p < 0.001*) with 30 min of equilibration, 487 ± 9 (p < 0.001*) with 45 min of equilibration, and 520 ± 16 s (p > 0.05) with 60 min of equilibration. This study reflects the extent to which storage temperatures and equilibration times can potentially affect the handling characteristics of PMMA cement. We recommend institutions to have a well-regulated temperature and humidity-controlled facility for storage of bone cements and a protocol to standardize the equilibration time of cements prior to use in the OT to improve consistency and reproducibility of the handling characteristics of PMMA cement.

Self-assembly of silk fibroin under osmotic stress

NASA Astrophysics Data System (ADS)

Sohn, Sungkyun

The supramolecular self-assembly behavior of silk fibroin was investigated using osmotic stress technique. In Chapter 2, a ternary phase diagram of water-silk-LiBr was constructed based on X-ray results on the osmotically stressed regenerated silk fibroin of Bombyx mori silkworm. Microscopic data indicated that silk I is a hydrated structure and a rough estimate of the number of water molecules lost by the structure upon converting from silk I to silk II has been made, and found to be about 2.2 per [GAGAGS] hexapeptide. In Chapter 3, wet-spinning of osmotically stressed, regenerated silk fibroin was performed, based on the prediction that the enhanced control over structure and phase behavior using osmotic stress method helps improve the physical properties of wet-spun regenerated silk fibroin fibers. The osmotic stress was applied in order to pre-structure the regenerated silk fibroin molecule from its original random coil state to more oriented state, manipulating the phase of the silk solution in the phase diagram before the start of spinning. Monofilament fiber with a diameter of 20 microm was produced. In Chapter 4, we investigated if there is a noticeable synergistic osmotic pressure increase between co-existing polymeric osmolyte and salt when extremely highly concentrated salt molecules are present both at sample subphase and stressing subphase, as is the case of silk fibroin self-assembly. The equilibration method that measures osmotic pressure relative to a reference with known osmotic pressure was introduced. Osmotic pressure of aqueous LiBr solution up to 2.75M was measured and it was found that the synergistic effect was insignificant up to this salt concentration. Solution parameters of stressing solutions and Arrhenius kinetics based on time-temperature relationship for the equilibration process were derived as well. In Chapter 5, self-assembly behavior of natural silk fibroin within the gland of Bombyx mori silkworm was investigated using osmotic stress technique. Microscopic and thermodynamic details of this self-assembly process along the spinline have been assessed. Formation of a needle-shaped molecular lath under appropriate osmotic stress was found. Silk I degree of hydration of silk gland was quantitatively estimated by image analysis of optical micrographs and the numbers varied from 2.2 to 2.7 depending on the region in the gland. Osmotic pressure in the gland was also estimated by equilibration method.

Very high pressure liquid chromatography using core-shell particles: quantitative analysis of fast gradient separations without post-run times.

PubMed

Stankovich, Joseph J; Gritti, Fabrice; Stevenson, Paul G; Beaver, Lois A; Guiochon, Georges

2014-01-17

Five methods for controlling the mobile phase flow rate for gradient elution analyses using very high pressure liquid chromatography (VHPLC) were tested to determine thermal stability of the column during rapid gradient separations. To obtain rapid separations, instruments are operated at high flow rates and high inlet pressure leading to uneven thermal effects across columns and additional time needed to restore thermal equilibrium between successive analyses. The purpose of this study is to investigate means to minimize thermal instability and obtain reliable results by measuring the reproducibility of the results of six replicate gradient separations of a nine component RPLC standard mixture under various experimental conditions with no post-run times. Gradient separations under different conditions were performed: constant flow rates, two sets of constant pressure operation, programmed flow constant pressure operation, and conditions which theoretically should yield a constant net heat loss at the column's wall. The results show that using constant flow rates, programmed flow constant pressures, and constant heat loss at the column's wall all provide reproducible separations. However, performing separations using a high constant pressure with programmed flow reduces the analysis time by 16% compared to constant flow rate methods. For the constant flow rate, programmed flow constant pressure, and constant wall heat experiments no equilibration time (post-run time) was required to obtain highly reproducible data. Copyright © 2013 Elsevier B.V. All rights reserved.

Combinations of glycerol percent, glycerol equilibration time, and thawing rate upon freezability of bull spermatozoa in plastic straws.

PubMed

Wiggin, H B; Almquist, J O

1975-03-01

Twelve ejaculates were used in a central composite experiment to test 15 combinations of glycerol (7, 9, 11, 13, or 15%), glycerol equilibration times (1, 2, 4, 8, or 16 h) and thawing rates (water at 35 C for 15 s, 50 C for 13 s, 65 C for 11 s, 80 C for 9 s, or 95 C for 7 s). Semen was diluted in heated skim milk-glycerol, packaged in .3-ml. Continental U.S. straws and frozen in liquid nitrogen vapor. Based on post-thaw progressive sperm motility after storage at -196 C for 9 to 11 days, estimated optima from multiple regression were 10.7% for glycerol, 2.0 h for glycerol equilibration time, and 76 C for thawing bath temperature. Only the linear effect for each variable was significant. Much faster thawing rates and shorter glycerol equilibration times than those for freezing bull spermatozoa in glass ampules should be used for maximum post-thaw sperm motility in straws.

Stability of chromium (III) sulfate in atmospheres containing oxygen and sulfur

NASA Technical Reports Server (NTRS)

Jacob, K. T.; Rao, B. D.; Nelson, H. G.

1978-01-01

The stability of chromium sulfate in the temperature range from 880 K to 1040 K was determined by employing a dynamic gas-solid equilibration technique. The solid chromium sulfate was equilibrated in a gas stream of controlled SO3 potential. Thermogravimetric and differential thermal analyses were used to follow the decomposition of chromium sulfate. X-ray diffraction analysis indicated that the decomposition product was crystalline Cr2O3 and that the mutual solubility between Cr2(SO4)3 and Cr2O3 was negligible. Over the temperature range investigated, the decomposition pressure were significantly high so that chromium sulfate is not expected to form on commercial alloys containing chromium when exposed to gaseous environments containing oxygen and sulfur (such as those encountered in coal gasification).

The last stage of Earth's formation: Increasing the pressure

NASA Astrophysics Data System (ADS)

Lock, S. J.; Stewart, S. T.; Mukhopadhyay, S.

2017-12-01

A range of high-energy, high-angular momentum (AM) giant impacts have been proposed as a potential trigger for lunar origin. High-energy, high-AM collisions create a previously unrecognized planetary object, called a synestia. Terrestrial synestias exceed the corotation limit for a rocky planet, forming an extended structure with a corotating inner region and disk-like outer region. We demonstrate that the internal pressures of Earth-like planets do not increase monotonically during the giant impact stage, but can vary substantially in response to changes in rotation and thermal state. The internal pressures in an impact-generated synestia are much lower than in condensed, slowly rotating planets of the same mass. For example, the core-mantle boundary (CMB) pressure can be as low as 60 GPa for a synestia with Earth mass and composition, compared to 136 GPa in the present-day Earth. The lower pressures are due to the low density and rapid rotation of the post-impact structure. After a high-AM Moon-forming impact, the internal pressures in the interior of the synestia would have increased to present-day Earth values in two stages: first by vapor condensation and second by removal of AM from the Earth during the tidal evolution of the Moon. The pressure evolution of the Earth has several implications. Metal-silicate equilibration after the impact would have occurred at much lower pressures than has previously been assumed. The observed moderately siderophile element abundances in the mantle may be consistent with equilibration at the bottom of a deep, lower-pressure magma ocean. In addition, the pressure at the CMB during cooling is coincident with, or lower than, the proposed intersection of liquid adiabats with the mantle liquidus. The mantle would hence freeze from the bottom up and there would be no basal magma ocean. The subsequent pressure increase and tidal heating due to the Moon's orbital evolution likely induces melting in the lowermost mantle. Increasing pressure in the upper mantle also leads to exothermic and endothermic phase changes potentially producing partial melts in the mid-mantle. High-pressure partial melts could produce precursor material for the seismically and chemically anomalous regions that are observed in the lower mantle today.

Measuring Transcutaneous Oxygenation to Validate the Duration Required to Achieve Electrode Equilibration.

PubMed

Chiang, Nathaniel; Jain, Jitendra K; Sleigh, Jamie; Vasudevan, Thodur

2018-06-01

The transcutaneous oxygenation measurement (TCOM) system is useful in assessing tissue viability. There are no clear recommendations regarding the duration required for the electrode to equilibrate and reliably evaluate tissue oxygenation values. The objective of this study was to validate the duration required to achieve electrode equilibration in a clinical setting. Minute-by-minute recordings using TCOM (TCOM3; Radiometer Medical ApS, Brønshøj, Copenhagen) were obtained for 82 limbs in 50 participants. Twenty-five limbs were in patients with peripheral vascular disease; 30 were in patients with no known peripheral vascular disease; and 27 were in healthy volunteers. Transcutaneous partial pressure of oxygen and carbon dioxide (TcPO2 and TcPCO2) were recorded over a 15-minute period. Participants' TcPO2 decreased and TcPCO2 increased over time. Both changed in a nonlinear fashion, eventually settling at an "equilibrium" where the measurements became stable. The difference in proportional change of TcPO2 between minutes 14 and 15 was 0.8%, and for TcPCO2was 2.9%. Changes in TCOM measurements over time were similar among the 3 groups. This is the first study to target minute-by-minute variation in TcPO2 and TcPCO2 measurements. Recording for a minimum of 15 minutes allows a reliable period for the TCOM electrode to equilibrate to record absolute values and determine wound healing potential.

Effect of Dihedral Angle and Porosity on Percolating-Sealing Capacity of Texturally Equilibrated Rock Salt

NASA Astrophysics Data System (ADS)

Ghanbarzadeh, S.; Hesse, M. A.; Prodanovic, M.; Gardner, J. E.

2013-12-01

Salt deposits in sedimentary basins have long been considered to be a seal against fluid penetration. However, experimental, theoretical and field evidence suggests brine (and oil) can wet salt crystal surfaces at higher pressures and temperatures, which can form a percolating network. This network may act as flow conduits even at low porosities. The aim of this work is to investigate the effects of dihedral angle and porosity on the formation of percolating paths in different salt network lattices. However, previous studies considered only simple homogeneous and isotropic geometries. This work extends the analysis to realistic salt textures by presenting a novel numerical method to describe the texturally equilibrated pore shapes in polycrystalline rock salt and brine systems. First, a theoretical interfacial topology was formulated to minimize the interfacial surface between brine and salt. Then, the resulting nonlinear system of ordinary differential equations was solved using the Newton-Raphson method. Results show that the formation of connected fluid channels is more probable in lower dihedral angles and at higher porosities. The connectivity of the pore network is hysteretic, because the connection and disconnection at the pore throats for processes with increasing or decreasing porosities occur at different porosities. In porous media with anisotropic solids, pores initially connect in the direction of the shorter crystal axis and only at much higher porosities in the other directions. Consequently, even an infinitesimal elongation of the crystal shape can give rise to very strong anisotropy in permeability of the pore network. Also, fluid flow was simulated in the resulting pore network to calculate permeability, capillary entry pressure and velocity field. This work enabled us to investigate the opening of pore space and sealing capacity of rock salts. The obtained pore geometries determine a wide range of petrophysical properties such as permeability and capillary entry pressure. This expanded knowledge of the salt textural behavior vs. depth could also improve drilling operations in salt. Second, a series of experiments in different P-T conditions was carried out to investigate the actual shape of equilibrated channels in salt. The synthetic salt samples were scanned at the High Resolution X-ray CT Facility at the Department of Geological Science, the University of Texas at Austin with resolution in 1-6 micron range. The experimental results show both equilibrated (tubular pores) and non-equilibrated (planar features) in salt structure. Image processing was carried out by two open source software programs: ImageJ, which is a public domain Java image processing program, and 3DMA-Rock, which is a software package for quantitative analyzing of the pore space in three-dimensional X-ray computed microtomographic images of rock. We obtain medial axis and medial surface of the pore space, as well as find and characterize the corresponding pore-throat network. We also report permeability of the pore space computed using Palabos software.

Investigating catalyst coated membrane equilibration time for polymer electrolyte membrane fuel cell manufacturing

NASA Astrophysics Data System (ADS)

Cote, Philippe

Mercedes-Benz Canada Inc., Fuel Cell Division, manufactures polymer electrolyte membrane fuel cell stacks for use in vehicles. The manufacturing line is being optimized for efficiency and quality control, in order to uphold the high standards of Mercedes-Benz Inc. vehicles. In an operating polymer electrolyte membrane fuel cell, the catalyst coated membrane facilitates the electrochemical reaction that generates electricity. This research examines the equilibration of catalyst coated membrane rolls to controlled temperature and humidity conditions, before they are used in the manufacturing of polymer electrolyte membrane fuel cells. Equilibration involves allowing the water content in the catalyst coated membrane to stabilize at the controlled conditions, in order to reduce mechanical stress in the material for better manufacturability. Initial equilibration measurements were conducted on discrete catalyst coated membrane samples using novel electronic conductivity measurements of the catalyst layer, and compared to ionic conductivity measurements of the membrane. Electronic conductivity measurements are easier to implement in the manufacturing environment than the more complex ionic conductivity measurements. When testing discrete catalyst coated membrane samples in an environmental chamber, the equilibration trends for the measured ionic and electronic conductivity signals were similar enough to permit us to adapt the electronic conductivity measurements for catalyst coated membrane in roll form. Equilibration measurements of catalyst coated membrane rolls were optimized to achieve a robust and repeatable procedure which could be used in the manufacturing environment at Mercedes-Benz Canada Inc., Fuel Cell Division.

Phloem water relations and translocation.

PubMed

Kaufmann, M R; Kramer, P J

1967-02-01

Satisfactory measurements of phloem water potential of trees can be obtained with the Richards and Ogata psychrometer and the vapor equilibration techniques, although corrections for loss of dry weight and for heating by respiration are required for the vapor equilibrium values. The psychrometer technique is the more satisfactory of the 2 because it requires less time for equilibration, less tissue, and less handling of tissue. Phloem water potential of a yellow-poplar tree followed a diurnal pattern quite similar to that of leaves, except that the values were higher (less negative) and changed less than in the leaves.The psychrometer technique permits a different approach to the study of translocation in trees. Measurements of water potential of phloem discs followed by freezing of samples and determination of osmotic potential allows estimation of turgor pressure in various parts of trees as the difference between osmotic potential and total water potential. This technique was used in evaluating gradients in water potential, osmotic potential, and turgor pressure in red maple trees. The expected gradients in osmotic potential were observed in the phloem, osmotic potential of the cell sap increasing (sap becoming more dilute) down the trunk. However, values of water potential were such that a gradient in turgor pressure apparently did not exist at a time when rate of translocation was expected to be high. These results do not support the mass flow theory of translocation favored by many workers.

Phloem Water Relations and Translocation 1

PubMed Central

Kaufmann, Merrill R.; Kramer, Paul J.

1967-01-01

Satisfactory measurements of phloem water potential of trees can be obtained with the Richards and Ogata psychrometer and the vapor equilibration techniques, although corrections for loss of dry weight and for heating by respiration are required for the vapor equilibrium values. The psychrometer technique is the more satisfactory of the 2 because it requires less time for equilibration, less tissue, and less handling of tissue. Phloem water potential of a yellow-poplar tree followed a diurnal pattern quite similar to that of leaves, except that the values were higher (less negative) and changed less than in the leaves. The psychrometer technique permits a different approach to the study of translocation in trees. Measurements of water potential of phloem discs followed by freezing of samples and determination of osmotic potential allows estimation of turgor pressure in various parts of trees as the difference between osmotic potential and total water potential. This technique was used in evaluating gradients in water potential, osmotic potential, and turgor pressure in red maple trees. The expected gradients in osmotic potential were observed in the phloem, osmotic potential of the cell sap increasing (sap becoming more dilute) down the trunk. However, values of water potential were such that a gradient in turgor pressure apparently did not exist at a time when rate of translocation was expected to be high. These results do not support the mass flow theory of translocation favored by many workers. PMID:16656495

Vocal Function and Upper Airway Thermoregulation in Five Different Environmental Conditions

PubMed Central

Sandage, Mary J.; Connor, Nadine P.; Pascoe, David D.

2013-01-01

Purpose Phonation threshold pressure and perceived phonatory effort were hypothesized to increase and upper airway temperature decrease following exposure to cold and/or dry air. Greater changes were expected with mouth versus nose breathing. Method Using a within-participant repeated measures design, 15 consented participants (7 men, 8 women) completed 20-minute duration trials to allow for adequate thermal equilibration for both nose and mouth breathing in five different environments: three temperatures (°C) matched for relative humidity (%RH): cold (15°C/40% RH), thermally neutral (25°C/40% RH), and hot (35°C/40% RH); and two temperatures with variable relative humidity to match vapor pressure for the neutral environment (25°C/40% RH): cold (15°C/74% RH) and hot (35°C; 23% RH). Following each equilibration trial, measures were taken in this order: upper airway temperature (transnasal thermistor probe), phonation threshold pressure, and perceived phonatory effort. Results Data were analyzed using repeated measures analysis of variance and no significant differences were established. Conclusions The study hypotheses were not supported. Findings suggest that the upper airway is tightly regulated for temperature when challenged by a realistic range of temperature/relative humidity environments. This is the first study of its kind to include measurement of upper airway temperature in conjunction with measures of vocal function. PMID:23900031

Preparation and characterization of nickel-spiked freshwater sediments for toxicity tests: toward more environmentally realistic nickel partitioning

USGS Publications Warehouse

Brumbaugh, William G.; Besser, John M.; Ingersoll, Christopher G.; May, Thomas W.; Ivey, Chris D.; Schlekat, Christian E.; Garman, Emily R.

2013-01-01

Two spiking methods were compared and nickel (Ni) partitioning was evaluated during a series of toxicity tests with 8 different freshwater sediments having a range of physicochemical characteristics. A 2-step spiking approach with immediate pH adjustment by addition of NaOH at a 2:1 molar ratio to the spiked Ni was effective in producing consistent pH and other chemical characteristics across a range of Ni spiking levels. When Ni was spiked into sediment having a high acid-volatile sulfide and organic matter content, a total equilibration period of at least 10 wk was needed to stabilize Ni partitioning. However, highest spiking levels evidently exceeded sediment binding capacities; therefore, a 7-d equilibration in toxicity test chambers and 8 volume-additions/d of aerobic overlying water were used to avoid unrealistic Ni partitioning during toxicity testing. The 7-d pretest equilibration allowed excess spiked Ni and other ions from pH adjustment to diffuse from sediment porewater and promoted development of an environmentally relevant, 0.5- to 1-cm oxic/suboxic sediment layer in the test chambers. Among the 8 different spiked sediments, the logarithm of sediment/porewater distribution coefficient values (log Kd) for Ni during the toxicity tests ranged from 3.5 to 4.5. These Kd values closely match the range of values reported for various field Ni-contaminated sediments, indicating that testing conditions with our spiked sediments were environmentally realistic.

Study of Chromium Oxide Activities in EAF Slags

NASA Astrophysics Data System (ADS)

Yan, Baijun; Li, Fan; Wang, Hui; Sichen, Du

2016-02-01

The activity coefficients of chromium in Cu-Cr melts were determined by equilibrating liquid copper with solid Cr2O3 in CO-CO2 atmosphere. The temperature dependence of the activity coefficients of chromium in Cu-Cr melts could be expressed as lg γ_{Cr}(s)^{0} = { 3 2 5 9( ± 1 8 6} )/T - 0. 5 9( { ± 0. 1} ). Based on the above results, the activities of bivalent and trivalent chromium oxide in some slags at 1873 K (1600 °C) were measured. The slags were equilibrated with Cu-Cr melts under two oxygen partial pressures ( {p_{O}_{ 2} }} } = 6.9 × 10-4 and 1.8 × 10-6 Pa, respectively). The morphology of the quenched slags and the solubility of chromium oxide in the melts were investigated by EPMA, SEM, and XRD. Under both oxygen partial pressures, the slags were saturated by the solid solution MgAl2- x Cr x O4- δ . At the low oxygen partial pressure (1.8 × 10-6 Pa), the content of Cr in the liquid phase varied from 0.4 to 1.6 mass pct with the total Cr content in the slags increasing from 1.3 to 10.8 mass pct. At the high oxygen partial pressure (6.9 × 10-4 Pa), the content of Cr in the liquid phase decreased to the level of 0.2 to 0.6 mass pct. Both the activities of CrO and Cr2O3 in slag were found to increase approximately linearly with the increase of the total Cr content in slag. While the oxygen partial pressure had minor effect on the activity of Cr2O3 in the slag, it had significant effect on the activity of CrO.

Eclogitization on the way up: Lu-Hf garnet chronology of metasomatic ultrahigh-pressure rocks from the Western Gneiss Complex, Norway

NASA Astrophysics Data System (ADS)

Cutts, J.; Smit, M. A.; Vrijmoed, J. C.

2016-12-01

The Western Gneiss Complex (WGC) is a fragment of continental crust that was subjected to high- and ultrahigh pressure (HP; UHP) conditions as a result of Caledonian continental collision (420-400 Ma). Most eclogite lenses and related high-pressure rocks have yielded petrological and chronological results that are consistent with a generalized model of Caledonian continental subduction. A distinct suite of eclogitic rocks - metasomatized (`Caledonized') Fe-Ti meta-peridotites - indicate extreme pressure conditions that do not fit the regional field gradient. The timing of these excursions is critical to their interpretation; however, so far limited age constraints exist for these rocks. In this study, we subject one such rock - the Magerøy orthopyroxene eclogite on the island of Otrøy - to Lu-Hf garnet chronology; a method that provides precise and robust data for garnet even at extreme temperatures. Conventional barometry indicates equilibration of the main garnet-bearing assemblage at c. 4.3 GPa and garnet geochronology yielded a date of c. 390 Ma. This result overlaps with Sm-Nd garnet and U-Pb zircon ages from the nearby diamond-bearing Svartberget peridotite body and leucosomes in its host gneiss. However, the age is ≥ 10 Ma younger than age data for most other eclogite lenses in WGC and corresponds to a time when the terrane was already exhumed to 30-35 km depth. The discrepancy in P-T-t evolution between the bulk of the WGC, and the (ultra-) mafic rocks at Magerøy and Svartberget indicates that the latter rocks reflect localized fluid-induced re-equilibration at pressures higher than lithostatic. The new data provide new support for the occurrence of this phenomenon in subducted continental crust undergoing exhumation and partial melting.

Effects of salt secretion on psychrometric determinations of water potential of cotton leaves.

PubMed

Klepper, B; Barrs, H D

1968-07-01

Thermocouple psychrometers gave lower estimates of water potential of cotton leaves than did a pressure chamber. This difference was considerable for turgid leaves, but progressively decreased for leaves with lower water potentials and fell to zero at water potentials below about -10 bars. The conductivity of washings from cotton leaves removed from the psychrometric equilibration chambers was related to the magnitude of this discrepancy in water potential, indicating that the discrepancy is due to salts on the leaf surface which make the psychrometric estimates too low. This error, which may be as great as 400 to 500%, cannot be eliminated by washing the leaves because salts may be secreted during the equilibration period. Therefore, a thermocouple psychrometer is not suitable for measuring the water potential of cotton leaves when it is above about -10 bars.

Effect of Stepwise Pressure Change on Porosity Evolution during Directional Solidification in Small Cylindrical Channels

NASA Technical Reports Server (NTRS)

Grugel, R.N.; Lee, C.P.; Cox, M.C.; Blandford, B.T.; Anilkumar, A.V.

2008-01-01

Controlled directional solidification experiments were performed in capillary channels, using nitrogen-saturated succinonitrile, to examine the effect of an in-situ stepwise processing pressure increase on an isolated pore evolution. Two experiments were performed using different processing pressure input profiles. The results indicate that a processing pressure increase has a transient effect on pore growth geometry characterized by an initial phase of decreasing pore diameter, followed by a recovery phase of increasing pore diameter. The experimental results also show that processing pressure can be used as a control parameter to either increase or terminate porosity formation. A theoretical model is introduced which indicates that the pore formation process is limited by the diffusion of solute-gas through the melt, and that the observed response toa pressure increase is attributed to the re-equilibration of solute concentration in the melt associated with the increased melt pressure.

Multi-Material Closure Model for High-Order Finite Element Lagrangian Hydrodynamics

DOE PAGES

Dobrev, V. A.; Kolev, T. V.; Rieben, R. N.; ...

2016-04-27

We present a new closure model for single fluid, multi-material Lagrangian hydrodynamics and its application to high-order finite element discretizations of these equations [1]. The model is general with respect to the number of materials, dimension and space and time discretizations. Knowledge about exact material interfaces is not required. Material indicator functions are evolved by a closure computation at each quadrature point of mixed cells, which can be viewed as a high-order variational generalization of the method of Tipton [2]. This computation is defined by the notion of partial non-instantaneous pressure equilibration, while the full pressure equilibration is achieved bymore » both the closure model and the hydrodynamic motion. Exchange of internal energy between materials is derived through entropy considerations, that is, every material produces positive entropy, and the total entropy production is maximized in compression and minimized in expansion. Results are presented for standard one-dimensional two-material problems, followed by two-dimensional and three-dimensional multi-material high-velocity impact arbitrary Lagrangian–Eulerian calculations. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.« less

Anionic Pt in Silicate Melts at Low Oxygen Fugacity: Speciation, Partitioning and Implications for Core Formation Processes on Asteroids

NASA Technical Reports Server (NTRS)

Medard, E.; Martin, A. M.; Righter, K.; Malouta, A.; Lee, C.-T.

2017-01-01

Most siderophile element concentrations in planetary mantles can be explained by metal/ silicate equilibration at high temperature and pressure during core formation. Highly siderophile elements (HSE = Au, Re, and the Pt-group elements), however, usually have higher mantle abundances than predicted by partitioning models, suggesting that their concentrations have been set by late accretion of material that did not equilibrate with the core. The partitioning of HSE at the low oxygen fugacities relevant for core formation is however poorly constrained due to the lack of sufficient experimental constraints to describe the variations of partitioning with key variables like temperature, pressure, and oxygen fugacity. To better understand the relative roles of metal/silicate partitioning and late accretion, we performed a self-consistent set of experiments that parameterizes the influence of oxygen fugacity, temperature and melt composition on the partitioning of Pt, one of the HSE, between metal and silicate melts. The major outcome of this project is the fact that Pt dissolves in an anionic form in silicate melts, causing a dependence of partitioning on oxygen fugacity opposite to that reported in previous studies.

Multi-Material Closure Model for High-Order Finite Element Lagrangian Hydrodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobrev, V. A.; Kolev, T. V.; Rieben, R. N.

We present a new closure model for single fluid, multi-material Lagrangian hydrodynamics and its application to high-order finite element discretizations of these equations [1]. The model is general with respect to the number of materials, dimension and space and time discretizations. Knowledge about exact material interfaces is not required. Material indicator functions are evolved by a closure computation at each quadrature point of mixed cells, which can be viewed as a high-order variational generalization of the method of Tipton [2]. This computation is defined by the notion of partial non-instantaneous pressure equilibration, while the full pressure equilibration is achieved bymore » both the closure model and the hydrodynamic motion. Exchange of internal energy between materials is derived through entropy considerations, that is, every material produces positive entropy, and the total entropy production is maximized in compression and minimized in expansion. Results are presented for standard one-dimensional two-material problems, followed by two-dimensional and three-dimensional multi-material high-velocity impact arbitrary Lagrangian–Eulerian calculations. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.« less

Sensitivity and Specificity of Eustachian Tube Function Tests in Adults

PubMed Central

Doyle, William J.; Swarts, J. Douglas; Banks, Julianne; Casselbrant, Margaretha L; Mandel, Ellen M; Alper, Cuneyt M.

2013-01-01

Objective Determine if Eustachian Tube (ET) function (ETF) tests can identify ears with physician-diagnosed ET dysfunction (ETD) in a mixed population at high sensitivity and specificity and define the inter-relatedness of ETF test parameters. Methods ETF was evaluated using the Forced-Response, Inflation-Deflation, Valsalva and Sniffing tests in 15 control ears of adult subjects after unilateral myringotomy (Group I) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (Group II). Data were analyzed using logistic regression including each parameter independently and then a step-down Discriminant Analysis including all ETF test parameters to predict group assignment. Factor Analysis operating over all parameters was used to explore relatedness. Results The Discriminant Analysis identified 4 ETF test parameters (Valsalva, ET opening pressure, dilatory efficiency and % positive pressure equilibrated) that together correctly assigned ears to Group II at a sensitivity of 95% and a specificity of 83%. Individual parameters representing the efficiency of ET opening during swallowing showed moderately accurate assignments of ears to their respective groups. Three factors captured approximately 98% of the variance among parameters, the first had negative loadings of the ETF structural parameters, the second had positive loadings of the muscle-assisted ET opening parameters and the third had negative loadings of the muscle-assisted ET opening parameters and positive loadings of the structural parameters. Discussion These results show that ETF tests can correctly assign individual ears to physician-diagnosed ETD with high sensitivity and specificity and that ETF test parameters can be grouped into structural-functional categories. PMID:23868429

Non-Immunogenic Structurally and Biologically Intact Tissue Matrix Grafts for the Immediate Repair of Ballistic-Induced Vascular and Nerve Tissue Injury in Combat Casualty Care

DTIC Science & Technology

2005-07-01

as an access graft is addressed using statistical methods below. Graft consistency can be defined statistically as the variance associated with the...addressed using statistical methods below. Graft consistency can be defined statistically as the variance associated with the sample of grafts tested in...measured using a refractometer (Brix % method). The equilibration data are shown in Graph 1. The results suggest the following equilibration scheme: 40% v/v

Characterizing the Chemical Stability of High Temperature Materials for Application in Extreme Environments

NASA Technical Reports Server (NTRS)

Opila, Elizabeth

2005-01-01

The chemical stability of high temperature materials must be known for use in the extreme environments of combustion applications. The characterization techniques available at NASA Glenn Research Center vary from fundamental thermodynamic property determination to material durability testing in actual engine environments. In this paper some of the unique techniques and facilities available at NASA Glenn will be reviewed. Multiple cell Knudsen effusion mass spectrometry is used to determine thermodynamic data by sampling gas species formed by reaction or equilibration in a Knudsen cell held in a vacuum. The transpiration technique can also be used to determine thermodynamic data of volatile species but at atmospheric pressures. Thermodynamic data in the Si-O-H(g) system were determined with this technique. Free Jet Sampling Mass Spectrometry can be used to study gas-solid interactions at a pressure of one atmosphere. Volatile Si(OH)4(g) was identified by this mass spectrometry technique. A High Pressure Burner Rig is used to expose high temperature materials in hydrocarbon-fueled combustion environments. Silicon carbide (SiC) volatility rates were measured in the burner rig as a function of total pressure, gas velocity and temperature. Finally, the Research Combustion Lab Rocket Test Cell is used to expose high temperature materials in hydrogen/oxygen rocket engine environments to assess material durability. SiC recession due to rocket engine exposures was measured as a function of oxidant/fuel ratio, temperature, and total pressure. The emphasis of the discussion for all techniques will be placed on experimental factors that must be controlled for accurate acquisition of results and reliable prediction of high temperature material chemical stability.

Very high pressure liquid chromatography using fully porous particles: quantitative analysis of fast gradient separations without post-run times.

PubMed

Stankovich, Joseph J; Gritti, Fabrice; Stevenson, Paul G; Beaver, Lois Ann; Guiochon, Georges

2014-01-10

Using a column packed with fully porous particles, four methods for controlling the flow rates at which gradient elution runs are conducted in very high pressure liquid chromatography (VHPLC) were tested to determine whether reproducible thermal conditions could be achieved, such that subsequent analyses would proceed at nearly the same initial temperature. In VHPLC high flow rates are achieved, producing fast analyses but requiring high inlet pressures. The combination of high flow rates and high inlet pressures generates local heat, leading to temperature changes in the column. Usually in this case a post-run time is input into the analytical method to allow the return of the column temperature to its initial state. An alternative strategy involves operating the column without a post-run equilibration period and maintaining constant temperature variations for subsequent analysis after conducting one or a few separations to bring the column to a reproducible starting temperature. A liquid chromatography instrument equipped with a pressure controller was used to perform constant pressure and constant flow rate VHPLC separations. Six replicate gradient separations of a nine component mixture consisting of acetophenone, propiophenone, butyrophenone, valerophenone, hexanophenone, heptanophenone, octanophenone, benzophenone, and acetanilide dissolved in water/acetonitrile (65:35, v/v) were performed under various experimental conditions: constant flow rate, two sets of constant pressure, and constant pressure operation with a programmed flow rate. The relative standard deviations of the response factors for all the analytes are lower than 5% across the methods. Programming the flow rate to maintain a fairly constant pressure instead of using instrument controlled constant pressure improves the reproducibility of the retention times by a factor of 5, when plotting the chromatograms in time. Copyright © 2013 Elsevier B.V. All rights reserved.

Effects of Salt Secretion on Psychrometric Determinations of Water Potential of Cotton Leaves

PubMed Central

Klepper, Betty; Barrs, H. D.

1968-01-01

Thermocouple psychrometers gave lower estimates of water potential of cotton leaves than did a pressure chamber. This difference was considerable for turgid leaves, but progressively decreased for leaves with lower water potentials and fell to zero at water potentials below about −10 bars. The conductivity of washings from cotton leaves removed from the psychrometric equilibration chambers was related to the magnitude of this discrepancy in water potential, indicating that the discrepancy is due to salts on the leaf surface which make the psychrometric estimates too low. This error, which may be as great as 400 to 500%, cannot be eliminated by washing the leaves because salts may be secreted during the equilibration period. Therefore, a thermocouple psychrometer is not suitable for measuring the water potential of cotton leaves when it is above about −10 bars. PMID:16656895

Shock Radiation Tests for Saturn and Uranus Entry Probes

NASA Technical Reports Server (NTRS)

Cruden, Brett A.; Bogdanoff, David W.

2014-01-01

This paper describes a test series in the Electric Arc Shock Tube at NASA Ames Research Center with the objective of quantifying shock-layer radiative heating magnitudes for future probe entries into Saturn and Uranus atmospheres. Normal shock waves are measured in Hydrogen/Helium mixtures (89:11 by mole) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 km/s. No shock layer radiation is detected below 25 km/s, a finding consistent with predictions for Uranus entries. Between 25-30 km/s, radiance is quantified from the Vacuum Ultraviolet through Near Infrared, with focus on the Lyman-alpha and Balmer series lines of Hydrogen. Shock profiles are analyzed for electron number density and electronic state distribution. The shocks do not equilibrate over several cm, and distributions are demonstrated to be non-Boltzmann. Radiation data are compared to simulations of Decadal survey entries for Saturn and shown to be significantly lower than predicted with the Boltzmann radiation model.

Mechanical Design and Testing of an Instrumented Rocker-Bogie Mobility System for the Kapvik Micro-Rover

NASA Astrophysics Data System (ADS)

Setterfield, T.

The rocker-bogie mobility system is a six-wheeled mobility system with the ability to equilibrate ground pressure amongst its wheels and traverse obstacles up to one wheel diameter in height; it has been used previously on NASA's Sojourner, Spirit, Opportunity and Curiosity rovers. This paper presents the mechanical design of an instrumented rocker-bogie mobility system for Kapvik, a 30 kg planetary micro-rover prototype developed for the Canadian Space Agency. The design of the wheel drive system is presented, including: motor selection, gear train selection, and performance limits. The design of a differential mechanism, which minimizes the pitch angle of the rover body, is provided. Design considerations for the integration of single-axis force sensors above the wheel hubs are presented. Structural analysis of the rocker and bogie links is outlined. The cross-hill and uphill-downhill static stability of Kapvik is investigated. Load cell and joint position data from testing during obstacle negotiation and uphill operation are presented.

Failure of the straight-line DCS boundary when extrapolated to the hypobaric realm.

PubMed

Conkin, J; Van Liew, H D

1992-11-01

The lowest pressure (P2) to which a diver can ascend without developing decompression sickness (DCS) after becoming equilibrated at some higher pressure (P1) is described by a straight line with a negative y-intercept. We tested whether extrapolation of such a line also predicts safe decompression to altitude. We substituted tissue nitrogen pressure (P1N2) calculated for a compartment with a 360-min half-time for P1 values; this allows data from hypobaric exposures to be plotted on a P2 vs. P1N2 graph, even if the subject breathes oxygen before ascent. In literature sources, we found 40 reports of human exposures in hypobaric chambers that fell in the region of a P2 vs. P1N2 plot where the extrapolation from hyperbaric data predicted that the decompression should be free of DCS. Of 4,576 exposures, 785 persons suffered decompression sickness (17%), indicating that extrapolation of the diver line to altitude is not valid. Over the pressure range spanned by human hypobaric exposures and hyperbaric air exposures, the best separation between no DCS and DCS on a P2 vs. P1N2 plot seems to be a curve which approximates a straight line in the hyperbaric region but bends toward the origin in the hypobaric region.

Continuous high-frequency dissolved O2/Ar measurements by equilibrator inlet mass spectrometry.

PubMed

Cassar, Nicolas; Barnett, Bruce A; Bender, Michael L; Kaiser, Jan; Hamme, Roberta C; Tilbrook, Bronte

2009-03-01

The oxygen (O(2)) concentration in the surface ocean is influenced by biological and physical processes. With concurrent measurements of argon (Ar), which has similar solubility properties as oxygen, we can remove the physical contribution to O(2) supersaturation and determine the biological oxygen supersaturation. Biological O(2) supersaturation in the surface ocean reflects the net metabolic balance between photosynthesis and respiration, i.e., the net community productivity (NCP). We present a new method for continuous shipboard measurements of O(2)/Ar by equilibrator inlet mass spectrometry (EIMS). From these measurements and an appropriate gas exchange parametrization, NCP can be estimated at high spatial and temporal resolution. In the EIMS configuration, seawater from the ship's continuous intake flows through a cartridge enclosing a gas-permeable microporous membrane contactor. Gases in the headspace of the cartridge equilibrate with dissolved gases in the flowing seawater. A fused-silica capillary continuously samples headspace gases, and the O(2)/Ar ratio is measured by mass spectrometry. The ion current measurements on the mass spectrometer reflect the partial pressures of dissolved gases in the water flowing through the equilibrator. Calibration of the O(2)/Ar ion current ratio (32/40) is performed automatically every 2 h by sampling ambient air through a second capillary. A conceptual model demonstrates that the ratio of gases reaching the mass spectrometer is dependent on several parameters, such as the differences in molecular diffusivities and solubilities of the gases. Laboratory experiments and field observations performed by EIMS are discussed. We also present preliminary evidence that other gas measurements, such as N(2)/Ar and pCO(2) measurements, may potentially be performed with EIMS. Finally, we compare the characteristics of the EIMS with the previously described membrane inlet mass spectrometry (MIMS) approach.

Driving Force of Plasma Bullet in Atmospheric-Pressure Plasma

NASA Astrophysics Data System (ADS)

Yambe, Kiyoyuki; Masuda, Seiya; Kondo, Shoma

2018-06-01

When plasma is generated by applying high-voltage alternating current (AC), the driving force of the temporally and spatially varying electric field is applied to the plasma. The strength of the driving force of the plasma at each spatial position is different because the electrons constituting the atmospheric-pressure nonequilibrium (cold) plasma move at a high speed in space. If the force applied to the plasma is accelerated only by the driving force, the plasma will be accelerated infinitely. The equilibrium between the driving force and the restricting force due to the collision between the plasma and neutral particles determines the inertial force and the drift velocity of the plasma. Consequently, the drift velocity depends on the strength of the time-averaged AC electric field. The pressure applied by the AC electric field equilibrates with the plasma pressure. From the law of conservation of energy, the pressure equilibrium is maintained by varying the drift velocity of the plasma.

Aqueous solubilities, vapor pressures, and 1-octanol-water partition coefficients for C9-C14 linear alkylbenzenes

USGS Publications Warehouse

Sherblom, P.M.; Gschwend, P.M.; Eganhouse, R.P.

1992-01-01

Measurements and estimates of aqueous solubilities, 1-octanol-water partition coefficients (Kow), and vapor pressures were made for 29 linear alkylbenzenes having alkyl chain lengths of 9-14 carbons. The ranges of values observed were vapor pressures from 0.002 to 0.418 Pa, log Kow, from 6.83 to 9.95, and aqueous solubilities from 4 to 38 nmol??L-1. Measured values exhibited a relationship to both the alkyl chain length and the position of phenyl substitution on the alkyl chain. Measurement of the aqueous concentrations resulting from equilibration of a mixture of alkylbenzenes yielded higher than expected values, indicating cosolute or other interactive effects caused enhanced aqueous concentrations of these compounds. ?? 1992 American Chemical Society.

Changes in ionic selectivity with changes in density of water in gels and cells

PubMed Central

Wiggins, Philippa M.; van Ryn, René T.

1990-01-01

Gels equilibrated with aqueous solutions of impermeant solutes reached a steady state in which, in the absence of a pressure difference, the activity of water in the pores of the gel was higher than that of water in the external solution. The chemical potential of water in the gel/polymer solution slurry was higher than that in the supernatant polymer solution removed from the gel. Water in the pores of the gel decreased in density to 0.96 as increasing osmotic stress was applied. It is argued that at constant temperature and pressure water can equilibrate between two compartments of unequal osmolality only by adjusting its molar volume. Experiments showed that when gel water had a higher activity than external water it was K+ selective; when it had a lower activity it was Na+ selective. It is proposed that a continuous spectrum of water structures can exist in these two compartment systems from dense, reactive, weakly-bonded water which selects highly hydrated ions, to expanded, stretched, unreactive, viscous water which is strongly hydrogen bonded and selects K+ and univalent anions. These findings are related to the state and properties of cytoplasmic water which is probably held under osmotic stress by the activity of the sodium pump. PMID:19431765

The effect of thermal resetting and recrystallisation on white mica 40Ar/39Ar ages during retrograde metamorphism on Syros, Greece

NASA Astrophysics Data System (ADS)

Uunk, Bertram; Wijbrans, Jan; Brouwer, Fraukje

2015-04-01

White mica 40Ar/39Ar dating is a proven powerful tool for constraining timing of metamorphism, deformation and exhumation. However, in high-pressure metamorphic rocks, dating often results in wide age ranges which are not in agreement with constraints from other isotopic systems, indicating that geological and chemical processes complicate straightforward 40Ar/39Ar dating. In this research project, white mica ages from rocks of the Cycladic Blueschist Unit on Syros, Greece with contrasting rheology and strain mechanisms are compared, in order to better understand the role of deformation, recrystallization and fluid flow on 40Ar/39Ar ages of white mica during retrograde metamorphism. Resulting ages vary along different sections on the island, inconsistent with other isotopic constraints on eclogite-blueschist metamorphism (55-50 Ma) and greenschist overprinting (41-30 Ma). Two end-member models are possible: 1) Results represent continuous crystallization of white mica while moving from blueschist to greenschist conditions in the metamorphic P-T loop, or 2) white mica equilibrated in eclogite-blueschist conditions and their diffusion systematics were progressively perturbed during greenschist overprinting. The single grain fusion analyses yielded contrasting age distributions, which indicate contrasts in degree of re-equilibration during retrograde metamorphism. Step wise heating of larger grain populations resulted in flat plateau shapes, providing no evidence for partial resetting. Electron microprobe measurements of Si per formula unit, as a proxy for pressure during crystallisation, do not explain age variation within sections or on the island scale. The previously unreported north-south age trend and age ranges per sample, as shown only in the 40Ar/39Ar system of the metapelitic and marble lithologies, contains key information that will allow us to test between different scenarios for age formation. Excess argon infiltration at this stage seems to have been of minor importance. Our new approach should lead to a better understanding of the interplay of these processes during and after HP metamorphism.

A Recipe for implementing the Arrhenius-Shock-Temperature State Sensitive WSD (AWSD) model, with parameters for PBX 9502

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aslam, Tariq Dennis

2017-10-03

A reactive ow model for the tri-amino-tri-nitro-benzene (TATB) based plastic bonded explosive PBX 9502 is presented. This newly devised model is based primarily on the shock temperature of the material, along with local pressure, and accurately models a broader range of detonation and initiation scenarios. The equation of state for the reactants and products, as well as the thermodynamic closure of pressure and temperature equilibration are carried over from the Wescott-Stewart-Davis (WSD) model7,8. Thus, modifying an existing WSD model in a hydrocode should be rather straightforward.

A new device for continuous monitoring the CO2 dissolved in water

NASA Astrophysics Data System (ADS)

de Gregorio, S.; Camarda, M.; Cappuzzo, S.; Giudice, G.; Gurrieri, S.; Longo, M.

2009-04-01

The measurements of dissolved CO2 in water are common elements of industrial processes and scientific research. In order to perform gas dissolved measurements is required to separate the dissolved gaseous phase from water. We developed a new device able to separate the gases phase directly in situ and well suitable for continuous measuring the CO2 dissolved in water. The device is made by a probe of a polytetrafluorethylene (PTFE) tube connected to an I.R. spectrophotometer (I.R.) and a pump. The PTFE is a polymeric semi-permeable membrane and allows the permeation of gas in the system. Hence, this part of the device is dipped in water in order to equilibrate the probe headspace with the dissolved gases. The partial pressure of the gas i in the headspace at equilibrium (Pi) follows the Henry's law: Pi=Hi•Ci, where Hi is the Henry's constant and Ci is the dissolved concentration of gas i. After the equilibrium is achieved, the partial pressure of CO2 inside the tube is equal to the partial pressure of dissolved CO2. The concentration of CO2 is measured by the I.R. connected to the tube. The gas is moved from the tube headspace to the I.R. by using the pump. In order to test the device and assess the best operating condition, several experimental were performed in laboratory. All the test were executed in a special apparatus where was feasible to create controlled atmospheres. Afterward the device has been placed in a draining tunnel sited in the Mt. Etna Volcano edifice (Italy). The monitored groundwater intercepts the Pernicana Fault, along which degassing phenomena are often observed. The values recorded by the station result in agreement with monthly directly measurements of dissolved CO2 partial pressure.

Development of a biaxial compression device for biological samples: preliminary experimental results for a closed cell foam.

PubMed

Little, J P; Tevelen, G; Adam, C J; Evans, J H; Pearcy, M J

2009-07-01

Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological samples. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the sample along one axis with an equilibrating tensile pressure. Thus a state of equibiaxial compression was created perpendicular to the long axis of a rectangular sample. For the purpose of calibration and commissioning of the vessel, rectangular samples of closed cell ethylene vinyl acetate (EVA) foam were tested. Each sample was subjected to repeated loading, and nine separate biaxial experiments were carried out to a maximum pressure of 204 kPa (30 psi), with a relaxation time of two hours between them. Calibration testing demonstrated the force applied to the samples had a maximum error of 0.026 N (0.423% of maximum applied force). Under repeated loading, the foam sample demonstrated lower stiffness during the first load cycle. Following this cycle, an increased stiffness, repeatable response was observed with successive loading. While the experimental protocol was developed for EVA foam, preliminary results on this material suggest that this device may be capable of providing test data for biological tissue samples. The load response of the foam was characteristic of closed cell foams, with consolidation during the early loading cycles, then a repeatable load-displacement response upon repeated loading. The repeatability of the test results demonstrated the ability of the test device to provide reproducible test data and the low experimental error in the force demonstrated the reliability of the test data.

Laser based water equilibration method for d18O determination of water samples

NASA Astrophysics Data System (ADS)

Mandic, Magda; Smajgl, Danijela; Stoebener, Nils

2017-04-01

Determination of d18O with water equilibration method using mass spectrometers equipped with equilibration unit or Gas Bench is known already for many years. Now, with development of laser spectrometers this extends methods and possibilities to apply different technologies in laboratory but also in the field. The Thermo Scientific™ Delta Ray™ Isotope Ratio Infrared Spectrometer (IRIS) analyzer with the Universal Reference Interface (URI) Connect and Teledyne Cetac ASX-7100 offers high precision and throughput of samples. It employs optical spectroscopy for continuous measurement of isotope ratio values and concentration of carbon dioxide in ambient air, and also for analysis of discrete samples from vials, syringes, bags, or other user-provided sample containers. Test measurements and conformation of precision and accuracy of method determination d18O in water samples were done in Thermo Fisher application laboratory with three lab standards, namely ANST, Ocean II and HBW. All laboratory standards were previously calibrated with international reference material VSMOW2 and SLAP2 to assure accuracy of the isotopic values of the water. With method that we present in this work achieved repeatability and accuracy are 0.16‰ and 0.71‰, respectively, which fulfill requirements of regulatory method for wine and must after equilibration with CO2.

Weak and strong coupling equilibration in nonabelian gauge theories

NASA Astrophysics Data System (ADS)

Keegan, Liam; Kurkela, Aleksi; Romatschke, Paul; van der Schee, Wilke; Zhu, Yan

2016-04-01

We present a direct comparison studying equilibration through kinetic theory at weak coupling and through holography at strong coupling in the same set-up. The set-up starts with a homogeneous thermal state, which then smoothly transitions through an out-of-equilibrium phase to an expanding system undergoing boost-invariant flow. This first apples-to-apples comparison of equilibration provides a benchmark for similar equilibration processes in heavy-ion collisions, where the equilibration mechanism is still under debate. We find that results at weak and strong coupling can be smoothly connected by simple, empirical power-laws for the viscosity, equilibration time and entropy production of the system.

Tank Pressure Control Experiment: Thermal Phenomena in Microgravity

NASA Technical Reports Server (NTRS)

Hasan, Mohammad M.; Lin, Chin S.; Knoll, Richard H.; Bentz, Michael D.

1996-01-01

The report presents the results of the flight experiment Tank Pressure Control Experiment/Thermal Phenomena (TPCE/TP) performed in the microgravity environment of the space shuttle. TPCE/TP, flown on the Space Transportation System STS-52, was a second flight of the Tank Pressure Control Experiment (TPCE). The experiment used Freon 113 at near saturation conditions. The test tank was filled with liquid to about 83% by volume. The experiment consisted of 21 tests. Each test generally started with a heating phase to increase the tank pressure and to develop temperature stratification in the fluid, followed by a fluid mixing phase for the tank pressure reduction and fluid temperature equilibration. The heating phase provided pool boiling data from large (relative to bubble sizes) heating surfaces (0.1046 m by 0.0742 m) at low heat fluxes (0.23 to 1.16 kW/sq m). The system pressure and the bulk liquid subcooling varied from 39 to 78 kPa and 1 to 3 C, respectively. The boiling process during the entire heating period, as well as the jet-induced mixing process for the first 2 min of the mixing period, was also recorded on video. The unique features of the experimental results are the sustainability of high liquid superheats for long periods and the occurrence of explosive boiling at low heat fluxes (0.86 to 1.1 kW/sq m). For a heat flux of 0.97 kW/sq m, a wall superheat of 17.9 C was attained in 10 min of heating. This superheat was followed by an explosive boiling accompanied by a pressure spike of about 38% of the tank pressure at the inception of boiling. However, at this heat flux the vapor blanketing the heating surface could not be sustained. Steady nucleate boiling continued after the explosive boiling. The jet-induced fluid mixing results were obtained for jet Reynolds numbers of 1900 to 8000 and Weber numbers of 0.2 to 6.5. Analyses of data from the two flight experiments (TPCE and TPCE/TP) and their comparison with the results obtained in drop tower experiments suggest that as Bond number approaches zero the flow pattern produced by an axial jet and the mixing time can be predicted by the Weber number.

Experiments pertaining to the formation and equilibration of planetary cores

NASA Technical Reports Server (NTRS)

Jeanloz, Raymond; Knittle, Elise; Williams, Quentin

1987-01-01

The phase diagram of FeO was experimentally determined to pressures of 155 GPa and temperatures of 4000 K using shock wave and diamond-cell techniques. Researchers discovered a metallic phase of FeO at pressures greater than 70 GPa and temperatures exceeding 1000 K. The metallization of FeO at high pressures implies that oxygen can be present as the light alloying element of the Earth's outer core, in accord with the geochemical predictions of Ringwood. The high pressures necessry for this metallization suggest that the core has acquired its composition well after the initial stages of the Earth's accretion. The core forming alloy can react chemically with oxides such as those forming the mantle. The core and mantle may never have reached complete chemical equilibrium, however. If this is the case, the core-mantle boundary is likely to be a zone of active chemical reactions.

H2O Adsorption on Smectites: Application to the Diurnal Variation of H2O in the Martian Atmosphere

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Howard, J.; Quinn, R. C.

2000-01-01

Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper, we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H2O adsorption kinetics on SWy-1, a Na-rich montmorillonite from Wyoming. The highest-temperature (273 K) data equilibrates rapidly. Data gathered at realistic H2O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars-like conditions, we show that the interlayer sites of smectites are likely to be unavailable.

Vascular endothelial growth factor receptor-3 is a novel target to improve net ultrafiltration in methylglyoxal-induced peritoneal injury.

PubMed

Terabayashi, Takeshi; Ito, Yasuhiko; Mizuno, Masashi; Suzuki, Yasuhiro; Kinashi, Hiroshi; Sakata, Fumiko; Tomita, Takako; Iguchi, Daiki; Tawada, Mitsuhiro; Nishio, Ryosuke; Maruyama, Shoichi; Imai, Enyu; Matsuo, Seiichi; Takei, Yoshifumi

2015-09-01

Appropriate fluid balance is important for good clinical outcomes and survival in patients on peritoneal dialysis. We recently reported that lymphangiogenesis associated with fibrosis developed in the peritoneal cavity via the transforming growth factor-β1-vascular endothelial growth factor-C (VEGF-C) pathway. We investigated whether VEGF receptor-3 (VEGFR-3), the receptor for VEGF-C and -D, might be a new target to improve net ultrafiltration by using adenovirus-expressing soluble VEGFR-3 (Adeno-sVEGFR-3) in rodent models of peritoneal injury induced by methylglyoxal (MGO). We demonstrated that lymphangiogenesis developed in these MGO models, especially in the diaphragm, indicating that lymphangiogenesis is a common feature in the peritoneal cavity with inflammation and fibrosis. In MGO models, VEGF-D was significantly increased in the diaphragm; however, VEGF-C was not significantly upregulated. Adeno-sVEGFR-3, which was detected on day 50 after administration via tail vein injections, successfully suppressed lymphangiogenesis in the diaphragm and parietal peritoneum in mouse MGO models without significant effects on fibrosis, inflammation, or neoangiogenesis. Drained volume in the peritoneal equilibration test using a 7.5% icodextrin peritoneal dialysis solution (the 7.5% icodextrin peritoneal equilibration test) was improved by Adeno-sVEGFR-3 on day 22 (P<0.05) and day 50 after reduction of inflammation (P<0.01), indicating that the 7.5% icodextrin peritoneal equilibration test identifies changes in lymphangiogenesis. The solute transport rate was not affected by suppression of lymphangiogenesis. In human peritoneal dialysis patients, the dialysate to plasma ratio of creatinine positively correlated with the dialysate VEGF-D concentration (P<0.001). VEGF-D mRNA was significantly higher in the peritoneal membranes of patients with ultrafiltration failure, indicating that VEGF-D is involved in the development of lymphangiogenesis in peritoneal dialysis patients. These results indicate that VEGFR-3 is a new target to improve net ultrafiltration by suppressing lymphatic absorption and that the 7.5% icodextrin peritoneal equilibration test is useful for estimation of lymphatic absorption.

Weak and strong coupling equilibration in nonabelian gauge theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keegan, Liam; Kurkela, Aleksi; Romatschke, Paul

2016-04-06

In this study, we present a direct comparison studying equilibration through kinetic theory at weak coupling and through holography at strong coupling in the same set-up. The set-up starts with a homogeneous thermal state, which then smoothly transitions through an out-of-equilibrium phase to an expanding system undergoing boost-invariant flow. This first apples-to-apples comparison of equilibration provides a benchmark for similar equilibration processes in heavy-ion collisions, where the equilibration mechanism is still under debate. We find that results at weak and strong coupling can be smoothly connected by simple, empirical power-laws for the viscosity, equilibration time and entropy production of themore » system.« less

Changes of peritoneal transport parameters with time on dialysis: assessment with sequential peritoneal equilibration test.

PubMed

Waniewski, Jacek; Antosiewicz, Stefan; Baczynski, Daniel; Poleszczuk, Jan; Pietribiasi, Mauro; Lindholm, Bengt; Wankowicz, Zofia

2017-10-27

Sequential peritoneal equilibration test (sPET) is based on the consecutive performance of the peritoneal equilibration test (PET, 4-hour, glucose 2.27%) and the mini-PET (1-hour, glucose 3.86%), and the estimation of peritoneal transport parameters with the 2-pore model. It enables the assessment of the functional transport barrier for fluid and small solutes. The objective of this study was to check whether the estimated model parameters can serve as better and earlier indicators of the changes in the peritoneal transport characteristics than directly measured transport indices that depend on several transport processes. 17 patients were examined using sPET twice with the interval of about 8 months (230 ± 60 days). There was no difference between the observational parameters measured in the 2 examinations. The indices for solute transport, but not net UF, were well correlated between the examinations. Among the estimated parameters, a significant decrease between the 2 examinations was found only for hydraulic permeability LpS, and osmotic conductance for glucose, whereas the other parameters remained unchanged. These fluid transport parameters did not correlate with D/P for creatinine, although the decrease in LpS values between the examinations was observed mostly for patients with low D/P for creatinine. We conclude that changes in fluid transport parameters, hydraulic permeability and osmotic conductance for glucose, as assessed by the pore model, may precede the changes in small solute transport. The systematic assessment of fluid transport status needs specific clinical and mathematical tools beside the standard PET tests.

A critical appraisal of the zero-multipole method: Structural, thermodynamic, dielectric, and dynamical properties of a water system.

PubMed

Wang, Han; Nakamura, Haruki; Fukuda, Ikuo

2016-03-21

We performed extensive and strict tests for the reliability of the zero-multipole (summation) method (ZMM), which is a method for estimating the electrostatic interactions among charged particles in a classical physical system, by investigating a set of various physical quantities. This set covers a broad range of water properties, including the thermodynamic properties (pressure, excess chemical potential, constant volume/pressure heat capacity, isothermal compressibility, and thermal expansion coefficient), dielectric properties (dielectric constant and Kirkwood-G factor), dynamical properties (diffusion constant and viscosity), and the structural property (radial distribution function). We selected a bulk water system, the most important solvent, and applied the widely used TIP3P model to this test. In result, the ZMM works well for almost all cases, compared with the smooth particle mesh Ewald (SPME) method that was carefully optimized. In particular, at cut-off radius of 1.2 nm, the recommended choices of ZMM parameters for the TIP3P system are α ≤ 1 nm(-1) for the splitting parameter and l = 2 or l = 3 for the order of the multipole moment. We discussed the origin of the deviations of the ZMM and found that they are intimately related to the deviations of the equilibrated densities between the ZMM and SPME, while the magnitude of the density deviations is very small.

Dual-Mode Free-Jet Combustor

NASA Technical Reports Server (NTRS)

Trefny, Charles J.; Dippold, Vance F., III; Yungster, Shaye

2017-01-01

The dual-mode free-jet combustor concept, pictured in figure 1, is described. It was introduced in 2010 as a wide- operating-range propulsion device using a novel supersonic free-jet combustion process. The unique feature of the free-jet combustor pictured in figure 1a, is supersonic combustion in an unconfined free-jet that traverses a larger subsonic combustion chamber to a variable nozzle. During this mode of operation, the propulsive stream is not in contact with the combustor walls, and equilibrates to the combustion chamber pressure. To a first order, thermodynamic efficiency is similar to that of a traditional scramjet under the assumption of constant-pressure combustion. Qualitatively, a number of possible benefits to this approach are obvious.

Shock Radiation Tests for Saturn and Uranus Entry Probes

NASA Technical Reports Server (NTRS)

Cruden, Brett A.; Bogdanoff, David W.

2017-01-01

This paper describes a test series in the Electric Arc Shock Tube at NASA Ames Research Center with the objective of quantifying shock-layer radiative heating magnitudes for future probe entries into Saturn and Uranus atmospheres. Normal shock waves are measured in Hydrogen-Helium mixtures (89:11 by volume) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 kms. No shock layer radiation is detected within measurement limits below 25 kms, a finding consistent with predictions for Uranus entries. Between 25-30 kms, radiance is quantified from the Vacuum Ultraviolet through Near Infrared, with focus on the Lyman-a and Balmer series lines of Hydrogen. Shock profiles are analyzed for electron number density and electronic state distribution. The shocks do not equilibrate over several cm, and in many cases the state distributions are non-Boltzmann. Radiation data are compared to simulations of Decadal Survey entries for Saturn and shown to be as much as 8x lower than predicted with the Boltzmann radiation model. Radiance is observed in front of the shock layer, the characteristics of which match the expected diffusion length.

Sensitivity and specificity of eustachian tube function tests in adults.

PubMed

Doyle, William J; Swarts, J Douglas; Banks, Julianne; Casselbrant, Margaretha L; Mandel, Ellen M; Alper, Cuneyt M

2013-07-01

The study demonstrates the utility of eustachian tube (ET) function (ETF) test results for accurately assigning ears to disease state. To determine if ETF tests can identify ears with physician-diagnosed ET dysfunction (ETD) in a mixed population at high sensitivity and specificity and to define the interrelatedness of ETF test parameters. Through use of the forced-response, inflation-deflation, Valsalva, and sniffing tests, ETF was evaluated in 15 control ears of adult subjects after unilateral myringotomy (group 1) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (group 2). Data were analyzed using logistic regression including each parameter independently and then a step-down discriminant analysis including all ETF test parameters to predict group assignment. Factor analysis operating over all parameters was used to explore relatedness. ETF testing. ETF parameters for the forced response, inflation-deflation, Valsalva, and sniffing tests measured in 15 control ears of adult subjects after unilateral myringotomy (group 1) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (group 2). The discriminant analysis identified 4 ETF test parameters (Valsalva, ET opening pressure, dilatory efficiency, and percentage of positive pressure equilibrated) that together correctly assigned ears to group 2 at a sensitivity of 95% and a specificity of 83%. Individual parameters representing the efficiency of ET opening during swallowing showed moderately accurate assignments of ears to their respective groups. Three factors captured approximately 98% of the variance among parameters: the first had negative loadings of the ETF structural parameters; the second had positive loadings of the muscle-assisted ET opening parameters; and the third had negative loadings of the muscle-assisted ET opening parameters and positive loadings of the structural parameters. These results show that ETF tests can correctly assign individual ears to physician-diagnosed ETD with high sensitivity and specificity and that ETF test parameters can be grouped into structural-functional categories.

Characterizing NZ equilibration in dynamically deformed system at 15, 25, 35 and 45 MeV/nucleon

NASA Astrophysics Data System (ADS)

Jedele, Andrea

2017-09-01

Neutron-proton equilibration is sensitive to the asymmetry energy in the nuclear equation of state. The process is governed by the contact time between the colliding nuclei and the gradient of the potential driving the equilibration. Recent work has shown NZ equilibration between the two largest fragments originating from the excited projectile-like fragment (PLF*) follows first-order kinetics in 70Zn, 64Zn and 64Ni symmetric reaction systems at 35 MeV/nucleon. The rate constant extracted was 3 zs-1, corresponding to a mean equilibration lifetime of 0.3 zs. An experiment has been proposed to examine the characteristics of NZ equilibration in 40Ca+ 64 , 70Zn at 15, 25, 35 and 45 MeV/nucleon with the NIMROD array.

Formation of sinoite in EL chondrites by impact melting

NASA Astrophysics Data System (ADS)

Rubin, Alan E.

1997-03-01

Approximately 10-200-micron-sized sunhedral and euhedral grains of twinned, optically zoned sinoite associated with euhedral enstatite and graphite within impact-melted portions of QUE94368, the first EL4 chondrite, suggest that sinoite formed by crystallization from a melt, not by thermal metamorphism. The occurrence of olivine and enstatite with undulose extinction in QUE94368 indicates that the rock is shock stage S2, corresponding to an equilibration shock pressure of about 5 GPa, as in EL5 and EL6 chondrites.

Shock Wave Structure Mediated by Energetic Particles

NASA Astrophysics Data System (ADS)

Mostafavi, P.; Zank, G. P.; Webb, G. M.

2016-12-01

Energetic particles such as cosmic rays, Pick Up Ions (PUIs), and solar energetic particles can affect all facets of plasma physics and astrophysical plasma. Energetic particles play an especially significant role in the dissipative process at shocks and in determining their structure. The very interesting recent observations of shocks in the inner heliosphere found that many shocks appear to be significantly mediated by solar energetic particles which have a pressure that exceeds considerably both the thermal gas pressure and the magnetic field pressure. Energetic particles contribute an isotropic scalar pressure to the plasma system at the leading order, as well as introducing dissipation via a collisionless heat flux (diffusion) at the next order and a collisionless stress tensor (viscosity) at the second order. Cosmic-ray modified shocks were discussed by Axford et al. (1982), Drury (1983), and Webb (1983). Zank et al. (2014) investigated the incorporation of PUIs in the supersonic solar wind beyond 10AU, in the inner Heliosheath and in the Very Local Interstellar Medium. PUIs do not equilibrate collisionally with the background plasma in these regimes. In the absence of equilibration between plasma components, a separate coupled plasma description for the energetic particles is necessary. This model is used to investigate the structure of shock waves assuming that we can neglect the magnetic field. Specifically, we consider the dissipative role that both the energetic particle collisionless heat flux and viscosity play in determining the structure of collisionless shock waves. We show that the incorporation of both energetic particle collisionless heat flux and viscosity is sufficient to completely determine the structure of a shock. Moreover, shocks with three sub-shocks converge to the weak sub-shocks. This work differs from the investigation of Jokipii and Williams (1992) who restricted their attention to a cold thermal gas. For a cold thermal non-magnetized gas, all shocks are smoothed by cosmic ray diffusion and therefore viscosity is not an important process.

A Proposed Dynamic Pressure and Temperature Primary Standard

PubMed Central

Rosasco, Gregory J.; Bean, Vern E.; Hurst, Wilbur S.

1990-01-01

Diatomic gas molecules have a fundamental vibrational motion whose frequency is affected by pressure in a simple way. In addition, these molecules have well defined rotational energy levels whose populations provide a reliable measure of the thermodynamic temperature. Since information concerning the frequency of vibration and the relative populations can be determined by laser spectroscopy, the gas molecules themselves can serve as sensors of pressure and temperature. Through measurements under static conditions, the pressure and temperature dependence of the spectra of selected molecules is now understood. As the time required for the spectroscopic measurement can be reduced to nanoseconds, the diatomic gas molecule is an excellent candidate for a dynamic pressure/temperature primary standard. The temporal response in this case will be limited by the equilibration time for the molecules to respond to changes in local thermodynamic variables. Preliminary feasibility studies suggest that by using coherent anti-Stokes Raman spectroscopy we will be able to measure dynamic pressure up to 108 Pa and dynamic temperature up to 1500 K with an uncertainty of 5%. PMID:28179756

Transport in a field aligned magnetized plasma/neutral gas boundary: the end of the plasma

NASA Astrophysics Data System (ADS)

Cooper, Christopher Michael

The objective of this dissertation is to characterize the physics of a boundary layer between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. A series of experiments are performed at the Enormous Toroidal Plasma Device (ETPD) at UCLA to study this field aligned Neutral Boundary Layer (NBL) at the end of the plasma. A Lanthanum Hexaboride (LaB6) cathode and semi-transparent anode creates a magnetized, current-free helium plasma which terminates on a neutral helium gas without touching any walls. Probes are inserted into the plasma to measure the basic plasma parameters and study the transport in the NBL. The experiment is performed in the weakly ionized limit where the plasma density (ne) is much less than the neutral density (nn) such that ne/nn < 5%. The NBL is characterized by a field-aligned electric field which begins at the point where the plasma pressure equilibrates with the neutral gas pressure. Beyond the pressure equilibration point the electrons and ions lose their momentum by collisions with the neutral gas and come to rest. An electric field is established self consistently to maintain a current-free termination through equilibration of the different species' stopping rates in the neutral gas. The electric field resembles a collisional quasineutral sheath with a length 10 times the electron-ion collision length, 100 times the neutral collision length, and 10,000 times the Debye length. Collisions with the neutral gas dominate the losses in the system. The measured plasma density loss rates are above the classical cross-field current-free ambipolar rate, but below the anomalous Bohm diffusion rate. The electron temperature is below the ionization threshold of the gas, 2.2 eV in helium. The ions are in thermal equilibrium with the neutral gas. A generalized theory of plasma termination in a Neutral Boundary Layer is applied to this case using a two-fluid, current-free, weakly ionized transport model. The electron and ion momentum equations along the field are combined in a generalized Ohm's law which predicts the axial electric field required to maintain a current-free termination. The pressure balance criteria for termination and the predicted electric field are confirmed over a scaling of plasma parameters. The experiment and the model are relevant for studying NBLs in other systems, such as the atmospheric termination of the aurora or detached gaseous divertors. A steady state modified ambipolar system is measured in the ETPD NBL. The drift speeds associated with these currents are a small fraction of the plasma flow speeds and the problem is treated as a perturbation to the termination model. The current-free condition on the model is relaxed to explain the presence of the divergence free current.

Experimental study of dynamic effective stress coefficient for ultrasonic velocities of Bakken cores

NASA Astrophysics Data System (ADS)

Ma, X.; Zoback, M. D.

2016-12-01

We have performed a series of exhaustive experiments to measure the effective stress coefficient (α) of the tight cores from the Bakken shale oil play. Five distinct, bedding-normal cores from a vertical well were tested, covering the sequences of Lodgepole, Middle Bakken, and Three Forks. The scope of this laboratory study is two-fold: (1) to obtain the dynamic effective stress coefficient for ultrasonic velocities; (2) to characterize the poromechanical properties in relation to rock's mineral composition and microstructure. The experiments were carried out as follows: Argon-saturated specimen (1-inch length, 1-inch diameter) was subjected to hydrostatic confining pressure under drained conditions. Pore pressure was regulated as Argon was injected into both ends of the specimen. We drilled multiple non-through-going boreholes (1-mm diameter) in the specimen to facilitate pore pressure equilibrium, without compromising its integrity. The specimen was put through a loading path to experience confining pressure and pore pressure up to 70 and 60 MPa, respectively. P- and S- wave velocities were measured and used to calculate the rock's dynamic effective stress coefficient. Results of all five cores unanimously show that the dynamic a is a function of both confining and pore pressures, regardless of the wave type and loading path. When the simple effective stress is low, α is close to unity; however, α consistently increases as the simple effective stress rises and can reach as much as 3 when the latter reaches 60 MPa. This trend is rather surprising as it is diametrically the opposite of what was observed for the static α. A possible explanation is that high-frequency wave-induced pore pressure increment may have not remained equilibrated throughout the pore space, especially in very thin cracks, according to the squirt model. This phenomenon can be enhanced when the bulk modulus of pore fluid (gas typically considered to be `soft' and `non-viscous') increases with pore pressure and becomes comparable to the crack stiffness.

Effects of an extension of the equilibration period up to 96 hours on the characteristics of cryopreserved bull semen.

PubMed

Fleisch, A; Malama, E; Witschi, U; Leiding, C; Siuda, M; Janett, F; Bollwein, H

2017-02-01

This study was designed to investigate the effects of an equilibration period up to 96 hours and three extenders (AndroMed, OPTIXcell, and Triladyl) on the quality of cryopreserved bull semen and to evaluate, whether an extension of the equilibration time to 72 hours does affect fertility in the field. One ejaculate of 17 bulls was collected and divided into three equal aliquots and diluted, respectively, with the three extenders. Each aliquot was again divided into five parts and equilibrated for 4, 24, 48, 72, and 96 hours before freezing in an automatic freezer. Sperm motility, plasma membrane and acrosome integrity (PMAI), and DNA fragmentation index (% DFI) were measured during equilibration. In addition to the parameters measured during equilibration, the percentage of viable sperm cells with high mitochondrial membrane potential (HMMP) was measured immediately after thawing, and after 3 hours of incubation at 37 °C. Sperm motility was assessed using CASA, and PMAI, HMMP, and % DFI were measured using flow cytometry. Equilibration time did affect all parameters before freezing (P < 0.01), and also the extender affected all parameters except HMMP (P < 0.05). After thawing, all parameters except HMMP immediately after thawing were influenced by the equilibration period (P < 0.001), whereas all parameters except % DFI immediately after thawing were influenced by the extender (P < 0.001). The changes of semen characteristics during 3 hours of incubation were also dependent on the equilibration time and the extender used in all parameters (P < 0.01). In the field study, semen of nine bulls was collected thrice weekly, processed using Triladyl egg yolk extender, and frozen in 0.25 mL straws with 15 × 10 6 spermatozoa per straw. In total, the nonreturn rates on Day 90 after insemination (NRR90) of 263,816 inseminations in two periods were evaluated. Whereas semen collected on Mondays and Wednesdays was equilibrated for 24 hours in both periods, semen collected on Fridays was equilibrated for 4 hours in period one and equilibrated for 72 hours in period 2. No differences in NRR90 could be found (P > 0.05). In conclusion, extension of the equilibration time from 4 hours to 24-72 hours can improve motility and viability of cryopreserved semen after thawing. The extent of improvement in semen quality is dependent on the extender used. Prolongation of the equilibration period from 4 hours to 72 hours had no effect on fertility in the field. Copyright © 2016 Elsevier Inc. All rights reserved.

Preservation of Primordial Mantle in the Aftermath of a Giant Impact

NASA Astrophysics Data System (ADS)

Lock, S. J.; Stewart, S. T.; Mukhopadhyay, S.

2016-12-01

Terrestrial planets experience a number of giant impacts in the final stages of accretion. These highly energetic events force planets into hot, partially vaporized, and occasionally rapidly-rotating states. However, recent measurements of Xe and W isotopes in mantle plume-derived basalts imply that the terrestrial mantle was not homogenized during this violent stage of Earth's accretion. Understanding the physical structure of post-impact states is key for interpreting these primitive mantle signatures. Post-impact states are highly thermally stratified: the lowermost mantle has lower entropy than the rest of the mantle. Usually, the lowermost mantle is near the solidus or partially molten. The high-entropy portion of the mantle is super-liquidus, smoothly grading to a silicate vapor atmosphere. Here, we consider the competing processes acting on these distinct layers as the mantle establishes a single thermal gradient. If the whole mantle chemically mixed during cooling, then any pre-impact chemical signature would be erased. Previous work has neglected the critical time period between the highly vaporized post-impact state and a fully-condensed silicate body, i.e., a separated magma ocean and atmosphere. The post-impact structure cools rapidly by radiation from the photosphere, causing contraction of the body and redistribution of mass and angular momentum. One consequence of contraction is that the pressure in the mantle increases significantly (on the order of several to 10s GPa at the core mantle boundary) over 10s-1000s years. The increased pressure causes part of the mantle to solidify. Significantly, the timescale for pressure-induced freezing is shorter than the timescale for thermal equilibration between the low and high entropy mantle layers and the timescale for melt percolation (both >100s yrs). Therefore, pressure-induced freezing in the aftermath of a giant impact may be an important factor in preserving primordial Xe and W signatures in the lower mantle. Pressure-induced freezing of the lower mantle predicts a different chemistry than that produced by fractional crystallization of a magma ocean. The post-impact planet could inherit chemical signatures from portions of the mantles of the impacting bodies that did not re-equilibrate with the metal core or outgas volatiles.

Potential energy landscape of TIP4P/2005 water

NASA Astrophysics Data System (ADS)

Handle, Philip H.; Sciortino, Francesco

2018-04-01

We report a numerical study of the statistical properties of the potential energy landscape of TIP4P/2005, one of the most accurate rigid water models. We show that, in the region where equilibrated configurations can be generated, a Gaussian landscape description is able to properly describe the model properties. We also find that the volume dependence of the landscape properties is consistent with the existence of a locus of density maxima in the phase diagram. The landscape-based equation of state accurately reproduces the TIP4P/2005 pressure-vs-volume curves, providing a sound extrapolation of the free-energy at low T. A positive-pressure liquid-liquid critical point is predicted by the resulting free-energy.

Pressure drop of He II flow through a porous media

NASA Technical Reports Server (NTRS)

Maddocks, J. R.; Van Sciver, S. W.

1990-01-01

The paper reports on measurements of He II pressure drop across two porous SiO2 ceramic filter materials. These materials vary only in porosity, having values of 0.94 and 0.96. The average fiber diameter in both cases is approximately 5 microns. The experiment consists of a glass tube containing a piece of this sponge in one end. The tube is rapidly displaced downward in a bath of helium and the liquid levels are allowed to equilibrate over time producing variable velocities up to 10 cm/sec. The results are compared with those previously obtained using fine mesh screens. Good qualitative agreement is observed for turbulent flow; however, the behavior in the laminar flow regime is not fully understood.

Note: A dual temperature closed loop batch reactor for determining the partitioning of trace gases within CO2-water systems.

PubMed

Warr, Oliver; Rochelle, Christopher A; Masters, Andrew J; Ballentine, Christopher J

2016-01-01

An experimental approach is presented which can be used to determine partitioning of trace gases within CO2-water systems. The key advantages of this system are (1) The system can be isolated with no external exchange, making it ideal for experiments with conservative tracers. (2) Both phases can be sampled concurrently to give an accurate composition at each phase at any given time. (3) Use of a lower temperature flow loop outside of the reactor removes contamination and facilitates sampling. (4) Rapid equilibration at given pressure/temperature conditions is significantly aided by stirring and circulating the water phase using a magnetic stirrer and high-pressure liquid chromatography pump, respectively.

Behavior of fragmentation front in a porous viscoelastic material

NASA Astrophysics Data System (ADS)

Ichihara, M.; Takayama, K.

2002-12-01

We are developing laboratory experiments to investigate dynamics of magma fragmentation during explosive volcanic eruptions. Fragmentation of such a mixture as magma consisting of viscoelastic melt, bubbles and solid particles, is not known yet, and experiments are necessary to establish a mathematical model. It has been shown that viscoelastic silicone compound (Dow Corning 3179) is a useful analogous material to simulate magma fragmentation. In the previous work, a porous specimen made of the compound was rapidly decompressed and development of brittle fragmentation was observed. However, there were arguments that the experiment was different from actual processes which produce fragments as small as volcanic ash, because in the experiment the specimen was broken into only several pieces. This time, results of the improved experiments are presented. The experimental apparatus is a kind of a vertical shock tube, which mainly consists of a high pressure test section and low pressure chambers. The test section is made of acrylic tube of which inner diameter is 25 mm. The internal phenomenon is recorded by a high-speed video camera. Pressure is measured in the gas above and beneath the specimen by piezoelectric transducers. The specimen is prepared in the following way. First, an acrylic tube filled with the compound is put in a nitrogen tank and kept at 45 bar for more than 8 hours. The compound absorbs the gas and equilibrates with the nitrogen. Next, the tank is decompressed back to the atmospheric pressure slowly. Nitrogen exsolves and bubbles are formed in the compound quite uniformly. Finally, the expanded compound sticking out of both ends of the tube is cut down, and the tube containing the specimen is attached to the shock tube. The specimen is rapidly decompressed by 24, 16, and 8 bars. The high-speed video images demonstrate a sequence of the fragmentation process. We observe propagation of a clear fracture front at 50 m/s for 24 bar of decompression and at smaller speed for smaller decompression. The pressure change associated with development of the fragmentation is analyzed and effects of over pressure in the pores and permeable gas flow on fragmentation behavior are discussed.

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects.

PubMed

Lemke, Sonja; Handle, Philip H; Plaga, Lucie J; Stern, Josef N; Seidl, Markus; Fuentes-Landete, Violeta; Amann-Winkel, Katrin; Köster, Karsten W; Gainaru, Catalin; Loerting, Thomas; Böhmer, Roland

2017-07-21

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping. The kinetics of the HDA to LDA transformation lacks a proton/deuteron isotope effect, revealing that this process is dominated by the restructuring of the oxygen network. The x-ray diffraction experiments performed on samples at intermediate transition stages reflect a linear combination of the LDA and HDA patterns implying a macroscopic phase separation, instead of a local intermixing of the two amorphous states.

Considerations for the head-injured air-evacuated patient: a case report of frontal sinus fracture and review of the literature.

PubMed

Helling, Eric; McKinlay, Alex J

2005-07-01

Head and neck injuries are not uncommon in combat environments and may be increasing due to survivable injuries from the use of kevlar helmets and body armor. With the current capability of rapid evacuation from the battlefield, acutely injured patients with frontal sinus injuries may undergo further barometric challenges. Proper care during transport can prevent the occurrence of secondary injury (increased intracranial pressure, tension pneumocephalus) that would complicate the patient's management at the next level of care. Management principles (importance of low-level flight/pressurized cabin, preflight use of decongestants, avoidance of valsalva, and ability to manage complications either procedurally or by landing) are reviewed. In addition, we propose a simple mechanism for pressure equilibration of a compromised frontal sinus during air evacuation using an angiocatheter placed through the wound before closure.

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects

NASA Astrophysics Data System (ADS)

Lemke, Sonja; Handle, Philip H.; Plaga, Lucie J.; Stern, Josef N.; Seidl, Markus; Fuentes-Landete, Violeta; Amann-Winkel, Katrin; Köster, Karsten W.; Gainaru, Catalin; Loerting, Thomas; Böhmer, Roland

2017-07-01

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping. The kinetics of the HDA to LDA transformation lacks a proton/deuteron isotope effect, revealing that this process is dominated by the restructuring of the oxygen network. The x-ray diffraction experiments performed on samples at intermediate transition stages reflect a linear combination of the LDA and HDA patterns implying a macroscopic phase separation, instead of a local intermixing of the two amorphous states.

Equilibration in finite Bose systems

NASA Astrophysics Data System (ADS)

Wolschin, Georg

2018-06-01

The equilibration of a finite Bose system is modeled using a gradient expansion of the collision integral that leads to a nonlinear transport equation. For constant transport coefficients, it is solved in closed form through a nonlinear transformation. Using schematic initial conditions, the exact solution and the equilibration time are derived and compared to the corresponding case for fermions. Applications to the fast equilibration of the gluon system created initially in relativistic heavy-ion collisions, and to cold quantum gases are envisaged.

Equilibrator-based measurements of dissolved nitrous oxide in the surface ocean using an integrated cavity output laser absorption spectrometer

NASA Astrophysics Data System (ADS)

Grefe, I.; Kaiser, J.

2014-06-01

Dissolved nitrous oxide (N2O) concentrations are usually determined by gas chromatography (GC). Here we present laboratory tests and initial field measurements using a novel setup comprising a commercially available laser-based analyser for N2O, carbon monoxide and water vapour coupled to a glass-bed equilibrator. This approach is less labour-intensive and provides higher temporal and spatial resolution than the conventional GC technique. The standard deviation of continuous equilibrator or atmospheric air measurements was 0.2 nmol mol-1 (averaged over 5 min). The short-term repeatability for reference gas measurements within 1 h of each other was 0.2 nmol mol-1 or better. Another indicator of the long-term stability of the analyser is the standard deviation of the calibrated N2O mole fraction in marine air, which was between 0.5 and 0.7 nmol mol-1. The equilibrator measurements were compared with purge-and-trap gas chromatography-mass spectrometry (GC-MS) analyses of N2O concentrations in discrete samples from the Southern Ocean and showed agreement to within the 2% measurement uncertainty of the GC-MS method. The equilibrator response time to concentration changes in water was from 142 to 203 s, depending on the headspace flow rate. The system was tested at sea during a north-to-south transect of the Atlantic Ocean. While the subtropical gyres were slightly undersaturated, the equatorial region was a source of nitrous oxide to the atmosphere, confirming previous findings (Forster et al., 2009). The ability to measure at high temporal and spatial resolution revealed submesoscale variability in dissolved N2O concentrations. Mean sea-to-air fluxes in the tropical and subtropical Atlantic ranged between -1.6 and 0.11 μmol m-2 d-1 and confirm that the subtropical Atlantic is not an important source region for N2O to the atmosphere, compared to global average fluxes of 0.6-2.4 μmol m-2 d-1. The system can be easily modified for autonomous operation on voluntary observing ships (VOS). Future work should include an interlaboratory comparison exercise with other methods of dissolved N2O analyses.

Equilibration of experimentally determined protein structures for molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Walton, Emily B.; Vanvliet, Krystyn J.

2006-12-01

Preceding molecular dynamics simulations of biomolecular interactions, the molecule of interest is often equilibrated with respect to an initial configuration. This so-called equilibration stage is required because the input structure is typically not within the equilibrium phase space of the simulation conditions, particularly in systems as complex as proteins, which can lead to artifactual trajectories of protein dynamics. The time at which nonequilibrium effects from the initial configuration are minimized—what we will call the equilibration time—marks the beginning of equilibrium phase-space exploration. Note that the identification of this time does not imply exploration of the entire equilibrium phase space. We have found that current equilibration methodologies contain ambiguities that lead to uncertainty in determining the end of the equilibration stage of the trajectory. This results in equilibration times that are either too long, resulting in wasted computational resources, or too short, resulting in the simulation of molecular trajectories that do not accurately represent the physical system. We outline and demonstrate a protocol for identifying the equilibration time that is based on the physical model of Normal Mode Analysis. We attain the computational efficiency required of large-protein simulations via a stretched exponential approximation that enables an analytically tractable and physically meaningful form of the root-mean-square deviation of atoms comprising the protein. We find that the fitting parameters (which correspond to physical properties of the protein) fluctuate initially but then stabilize for increased simulation time, independently of the simulation duration or sampling frequency. We define the end of the equilibration stage—and thus the equilibration time—as the point in the simulation when these parameters attain constant values. Compared to existing methods, our approach provides the objective identification of the time at which the simulated biomolecule has entered an energetic basin. For the representative protein considered, bovine pancreatic trypsin inhibitor, existing methods indicate a range of 0.2-10ns of simulation until a local minimum is attained. Our approach identifies a substantially narrower range of 4.5-5.5ns , which will lead to a much more objective choice of equilibration time.

Chronic binge alcohol consumption during pregnancy alters rat maternal uterine artery pressure response.

PubMed

Naik, Vishal D; Lunde-Young, Emilie R; Davis-Anderson, Katie L; Orzabal, Marcus; Ivanov, Ivan; Ramadoss, Jayanth

2016-11-01

We aimed to investigate pressure-dependent maternal uterine artery responses and vessel remodeling following gestational binge alcohol exposure. Two groups of pregnant rats were used: the alcohol group (28.5% wt/v, 6.0 g/kg, once-daily orogastric gavage in a binge paradigm between gestational day (GD) 5-19) and pair-fed controls (isocalorically matched). On GD20, excised, pressurized primary uterine arteries were studied following equilibration (60 mm Hg) using dual chamber arteriograph. The uterine artery diameter stabilized at 20 mm Hg, showed passive distension at 40 mm Hg, and redeveloped tone at 60 mm Hg. An alcohol effect (P = 0.0025) was observed on the percent constriction of vessel diameter with greater pressure-dependent myogenic constriction. Similar alcohol effect was noted with lumen diameter response (P = 0.0020). The percent change in media:lumen ratio was higher in the alcohol group (P < 0.0001). Thus, gestational alcohol affects pressure-induced uterine artery reactivity, inward-hypotrophic remodeling, and adaptations critical for nutrient delivery to the fetus. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of equilibration on primitive path analyses of entangled polymers.

PubMed

Hoy, Robert S; Robbins, Mark O

2005-12-01

We use recently developed primitive path analysis (PPA) methods to study the effect of equilibration on entanglement density in model polymeric systems. Values of Ne for two commonly used equilibration methods differ by a factor of 2-4 even though the methods produce similar large-scale chain statistics. We find that local chain stretching in poorly equilibrated samples increases entanglement density. The evolution of Ne with time shows that many entanglements are lost through fast processes such as chain retraction as the local stretching relaxes. Quenching a melt state into a glass has little effect on Ne. Equilibration-dependent differences in short-scale structure affect the craze extension ratio much less than expected from the differences in PPA values of Ne.

The electrolyte challenge for a direct methanol-air polymer electrolyte fuel cell operating at temperatures up to 200 C

NASA Technical Reports Server (NTRS)

Savinell, Robert; Yeager, Ernest; Tryk, Donald; Landau, Uziel; Wainright, Jesse; Gervasio, Dominic; Cahan, Boris; Litt, Morton; Rogers, Charles; Scherson, Daniel

1993-01-01

Novel polymer electrolytes are being evaluated for use in a direct methanol-air fuel cell operating at temperatures in excess of 100 C. The evaluation includes tests of thermal stability, ionic conductivity, and vapor transport characteristics. The preliminary results obtained to date indicate that a high temperature polymer electrolyte fuel cell is feasible. For example, Nafion 117 when equilibrated with phosphoric acid has a conductivity of at least 0.4 Omega(exp -1)cm(exp -1) at temperatures up to 200 C in the presence of 400 torr of water vapor and methanol vapor cross over equivalent to 1 mA/cm(exp 2) under a one atmosphere methanol pressure differential at 135 C. Novel polymers are also showing similar encouraging results. The flexibility to modify and optimize the properties by custom synthesis of these novel polymers presents an exciting opportunity to develop an efficient and compact methanol fuel cell.

Subduction of Proterozoic to Late Triassic continental basement in the Guatemala suture zone: A petrological and geochronological study of high-pressure metagranitoids from the Chuacús complex

NASA Astrophysics Data System (ADS)

Maldonado, Roberto; Ortega-Gutiérrez, Fernando; Ortíz-Joya, Guillermo A.

2018-05-01

Many continental subduction complexes contain abundant granitic rocks coexisting with minor volumes of eclogite-facies rocks. Characterization of granitic protoliths is crucial to decipher the origin of subducted continental crust, whereas knowledge of its metamorphic evolution is required to constrain the mechanisms of burial and exhumation. In this work we present geochronological and petrological evidence that demonstrate the occurrence of a subducted Proterozoic to Late Triassic granitic basement in the Chuacús complex of central Guatemala. Metagranitoids exposed in this area are interlayered with eclogite and other high-pressure rocks, and their structure is considerably variable due to strain partitioning during deformation. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon data from two ferroan metagranites yield protolith crystallization ages of ca. 1.1 Ga and their trace-element abundances suggest an origin related to intraplate magmatism, while a high-silica, peraluminous metagranite is dated at 1.0 Ga and was probably originated by partial melting of a high-grade continental crust. On the other hand, two megacrystic to augen metagranitoids yield protolith crystallization ages of ca. 224 Ma, which are identical within errors to the protolith age of hosted eclogitic metabasites. Their high incompatible trace element abundances together with the observed spatial-temporal relationships with mafic protoliths suggest that Late Triassic bimodal magmatism in the Chuacús complex was probably originated in a within-plate setting. Regardless of their age or structure, the studied metagranites preserve evidences for high-pressure metamorphic equilibration, such as the occurrence of Ca-rich garnet (XCa up to 0.52) in association with phengite (Si contents of up to 3.4 pfu) and rutile. The integration of Zr-in-rutile thermometry and phengite barometry allows the peak metamorphic conditions to be constrained at 640-680 °C and 13 kbar. This pressure-temperature estimate indicates that metagranitoids underwent high-pressure metamorphism but equilibrated at significantly lower pressures than associated eclogite-facies rocks, and, therefore, they do not necessarily share a common high-pressure metamorphic evolution. The new data show that the Chuacús complex in the study area represents a Proterozoic (1.1-1.0 Ga) to Late Triassic (220 Ma) continental basement that was subducted, and consequently metamorphosed under high-pressure conditions, during the Cretaceous evolution of the North America-Caribbean plate boundary.

Effects of Dissolved Carbonate on Arsenate Adsorption and Surface Speciation at the Hematite-Water Interface

USGS Publications Warehouse

Arai, Y.; Sparks, D.L.; Davis, J.A.

2004-01-01

Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [PCO2 = 10 -3.5 atm and ???0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L -1, [As(V)]0 = 1.5 mM and / = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L-1, [As(V)] 0 = 0.5 mM and / = 0.01 M NaCl], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (PCO2 = 10-3.5 atm)than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear (???2.8 A??) and bidentate binuclear (???3.3 A??) bonding at pH 4.5-8 and loading levels of 0.46-3.10 ??M m-2. Using the results of the pseudoequilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the PCO2 = 10-3.5 atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to electrical double-layer potentials caused by the adsorption of carbonate in the air-equilibrated system. Overall results suggest that the effects of dissolved carbonate on As(V) adsorption were influenced by the reaction conditions [e.g., available surface sites, initial As(V) concentrations, and reaction times]. Quantifying the effects of adsorbed carbonate may be important in predicting As(V) transport processes in groundwater, where iron oxide-coated aquifer materials are exposed to seasonally fluctuating partial pressures of CO2(g).

Siderophile Element Constraints on the Conditions of Core Formation in Mars

NASA Technical Reports Server (NTRS)

Righter, K.; Humayun, M.

2012-01-01

Siderophile element concentrations in planetary basalts and mantle samples have been used to estimate conditions of core formation for many years and have included applications to Earth, Moon, Mars and asteroid 4 Vesta [1]. For Earth, we have samples of mantle and a diverse collection of mantle melts which have provided a mature understanding of the how to reconstruct the concentration of siderophile elements in mantle materials, from only concentrations in surficial basalt (e.g., [2]). This approach has led to the consensus views that Earth underwent an early magma ocean stage to pressures of 40-50 GPa (e.g., [3,4]), Moon melted extensively and formed a small (approx. 2 mass %) metallic core [5], and 4 Vesta contains a metallic core that is approximately 18 mass % [6,7]. Based on new data from newly found meteorites, robotic spacecraft, and experimental partitioning studies, [8] showed that eight siderophile elements (Ni, Co, Mo, W, Ga, P, V and Cr) are consistent with equilibration of a 20 mass% S-rich metallic core with the mantle at pressures of 14 +/- 3 GPa. We aim to test this rather simple scenario with additional analyses of meteorites for a wide range of siderophile elements, and application of new experimental data for the volatile siderophile and highly siderophile elements.

Residual CO2 trapping in Indiana limestone.

PubMed

El-Maghraby, Rehab M; Blunt, Martin J

2013-01-02

We performed core flooding experiments on Indiana limestone using the porous plate method to measure the amount of trapped CO(2) at a temperature of 50 °C and two pressures: 4.2 and 9 MPa. Brine was mixed with CO(2) for equilibration, then the mixture was circulated through a sacrificial core. Porosity and permeability tests conducted before and after 884 h of continuous core flooding confirmed negligible dissolution. A trapping curve for supercritical (sc)CO(2) in Indiana showing the relationship between the initial and residual CO(2) saturations was measured and compared with that of gaseous CO(2). The results were also compared with scCO(2) trapping in Berea sandstone at the same conditions. A scCO(2) residual trapping end point of 23.7% was observed, indicating slightly less trapping of scCO(2) in Indiana carbonates than in Berea sandstone. There is less trapping for gaseous CO(2) (end point of 18.8%). The system appears to be more water-wet under scCO(2) conditions, which is different from the trend observed in Berea; we hypothesize that this is due to the greater concentration of Ca(2+) in brine at higher pressure. Our work indicates that capillary trapping could contribute to the immobilization of CO(2) in carbonate aquifers.

Ion Acceleration by Double Layers with Multi-Component Ion Species

NASA Astrophysics Data System (ADS)

Good, Timothy; Aguirre, Evan; Scime, Earl; West Virginia University Team

2017-10-01

Current-free double layers (CFDL) models have been proposed to explain observations of magnetic field-aligned ion acceleration in plasmas expanding into divergent magnetic field regions. More recently, experimental studies of the Bohm sheath criterion in multiple ion species plasma reveal an equilibration of Bohm speeds at the sheath-presheath boundary for a grounded plate in a multipole-confined filament discharge. We aim to test this ion velocity effect for CFDL acceleration. We report high resolution ion velocity distribution function (IVDF) measurements using laser induced fluorescence downstream of a CFDL in a helicon plasma. Combinations of argon-helium, argon-krypton, and argon-xenon gases are ionized and measurements of argon or xenon IVDFs are investigated to determine whether ion acceleration is enhanced (or diminished) by the presence of lighter (or heavier) ions in the mix. We find that the predominant effect is a reduction of ion acceleration consistent with increased drag arising from increased gas pressure under all conditions, including constant total gas pressure, equal plasma densities of different ions, and very different plasma densities of different ions. These results suggest that the physics responsible for acceleration of multiple ion species in simple sheaths is not responsible for the ion acceleration observed in these expanding plasmas. Department of Physics, Gettysburg College.

How long does it take to equilibrate the unfolded state of a protein?

PubMed Central

Levy, Ronald M; Dai, Wei; Deng, Nan-Jie; Makarov, Dmitrii E

2013-01-01

How long does it take to equilibrate the unfolded state of a protein? The answer to this question has important implications for our understanding of why many small proteins fold with two state kinetics. When the equilibration within the unfolded state U is much faster than the folding, the folding kinetics will be two state even if there are many folding pathways with different barriers. Yet the mean first passage times (MFPTs) between different regions of the unfolded state can be much longer than the folding time. This seems to imply that the equilibration within U is much slower than the folding. In this communication we resolve this paradox. We present a formula for estimating the time to equilibrate the unfolded state of a protein. We also present a formula for the MFPT to any state within U, which is proportional to the average lifetime of that state divided by the state population. This relation is valid when the equilibration within U is very fast as compared with folding as it often is for small proteins. To illustrate the concepts, we apply the formulas to estimate the time to equilibrate the unfolded state of Trp-cage and MFPTs within the unfolded state based on a Markov State Model using an ultra-long 208 microsecond trajectory of the miniprotein to parameterize the model. The time to equilibrate the unfolded state of Trp-cage is ∼100 ns while the typical MFPTs within U are tens of microseconds or longer. PMID:23963761

What can the Hf–W System tell Us About the Mechanism and Timing of Earth's Core Formation?

NASA Astrophysics Data System (ADS)

Fischer, R. A.; Nimmo, F.; O'Brien, D. P.

2018-05-01

Strong tradeoff between effects of depth and extent of metal-silicate equilibration and formation timescale on the Hf-W system. Whole mantle equilibration requires k = 0.4. Later formation times require less equilibration to match Earth's anomaly.

Computer controlled titration with piston burette or peristaltic pump - a comparison.

PubMed

Hoffmann, W

1996-09-01

The advantages and problems of the use of piston burettes and peristaltic pumps for dosage of titrant solutions in automatic titrations are shown. For comparison, only the dosing devices were exchanged and all other components and conditions remained unchanged. The results of continuous acid base titration show good agreement and comparable reproducibility. Potentiometric sensors (glass electrodes) with different equilibration behaviour influence the results. The capability of such electrodes was tested. Conductometric measurements allow a much faster detection because there is no equilibration of electrodes. Piston burettes should be used for titration with very high precision, titration with organic solvents and slow titrations. Peristaltic pumps seem to be more suitable for continuous titrations and long time operation without service.

Moisture absorption and bakeout characteristics of rigid-flexible multilayer printed wiring boards

NASA Astrophysics Data System (ADS)

Lula, J. W.

1991-01-01

Moisture absorption and bakeout characteristics of rigid flexible printed wiring boards were determined. It was found that test specimens had absorbed 0.95 weight percent moisture when equilibrated to a 50 percent RH, 25 C environment. Heating those equilibrated specimens in a 120 C static air oven removed 92 percent of this absorbed moisture in 24 h. Heating the samples in a 80 C static air oven removed only 64 percent of the absorbed moisture at the end of 24 h. A 120 C vacuum bake removed moisture at essentially the same rate with parylene slowed the absorption rate by approximately 50 percent but did not appreciably affect the equilibrium moisture content or the drying rate.

Spectrometric Analysis for Pulse Jet Mixer Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

ZEIGLER, KRISTINE

2004-07-12

The Analytical Development Section (ADS) was tasked with providing support for a Hanford River Protection Program-Waste Treatment Program (RPP-WTP) project test involving absorption analysis for non-Newtonian pulse jet mixer testing for small scale (PJM) and prototype (CRV) tanks with sparging. Tanks filled with clay were mixed with various amounts of powdered dye as a tracer. The objective of the entire project was to determine the best mixing protocol (nozzle velocity, number of spargers used, total air flow, etc.) by determining the percent mixed volume through the use of an ultraviolet-visible (UV-Vis) spectrometer. The dye concentration within the sample could bemore » correlated to the volume fraction mixed in the tank. Samples were received in vials, a series of dilutions were generated from the clay, allowed to equilibrate, then centrifuged and siphoned for the supernate liquid to analyze by absorption spectroscopy. Equilibration of the samples and thorough mixing of the samples were a continuous issue with dilution curves being difficult to obtain. Despite these technical issues, useful data was obtained for evaluation of various mix conditions.« less

Equilibration: Developing the Hard Core of the Piagetian Research Program.

ERIC Educational Resources Information Center

Rowell, J.A.

1983-01-01

Argues that the status of the concept of equilibration is classified by considering Piagetian theory as a research program in the sense elaborated in 1974 by Lakatos. A pilot study was made to examine the precision and testability of equilibration in Piaget's 1977 model.(Author/RH)

Rapid spatial equilibration of a particle in a box.

PubMed

Malabarba, Artur S L; Linden, Noah; Short, Anthony J

2015-12-01

We study the equilibration behavior of a quantum particle in a one-dimensional box, with respect to a coarse-grained position measurement (whether it lies in a certain spatial window or not). We show that equilibration in this context indeed takes place and does so very rapidly, in a time comparable to the time for the initial wave packet to reach the edges of the box. We also show that, for this situation, the equilibration behavior is relatively insensitive to the precise choice of position measurements or initial condition.

Short communication: Serum composition of milk subjected to re-equilibration by dialysis at different temperatures, after pH adjustments.

PubMed

Zhao, Zhengtao; Corredig, Milena

2016-04-01

The objective of this work was to investigate the properties of casein micelles after pH adjustment and their re-equilibration to the original pH and serum composition. Re-equilibration was carried out by dialyzing against skim milk at 2 different temperatures (4 or 22 °C). Turbidity, the average radius of the casein micelles, and the composition of the soluble phase were measured at different pH values, ranging between 5.5 and 8. Acidification led to the solubilization of colloidal calcium phosphate and decrease of the average radius of the micelles. With re-equilibration, casein dissociation occurred. In milk with pH values greater than 6.0, the average radius was recovered after re-equilibration. At pH values greater than neutral, an increase of the radius of casein micelles and increased dissociation of the casein were found. After re-equilibration, the radius of micelles and soluble protein in the serum decreased. The results were not affected by the temperature of re-equilibration. The changes to the calcium phosphate equilibrium and the dissociation of the micelles will have important consequences to the functionality of casein micelles. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Insensitivity of cardiovascular function to low power cm-/mm-microwaves.

PubMed

Kantz, J; Müller, J; Hadeler, K P; Landstorfer, F M; Lang, F

2005-06-01

A previous study failed to disclose an effect of short (15 min) exposure to low level energy microwaves (3 microW/cm2) emitted by a commercially available automobile radar system (77 GHz) for adaptive cruise control (ACC) on cardiovascular function. The present study explored whether a 15 min exposure to higher level energy microwaves of frequencies varying from 5.8 to 110 GHz influences cardiovascular function. To this end heart rate, skin temperature (thermocouple), skin conductance (Ag/AgCl electrodes), systolic and diastolic blood pressure (automatic cuff) were recorded in 50 test persons before, during and after a 15 min exposure to a sequential pattern of microwaves varying from 5.8 to 110 GHz (59.7 microW/cm2). After an equilibration period of 30 min the first group of test persons and after additional 30 min the second group of test persons were exposed. The study has been performed in a strict double blind design. While significant effects on the measured parameters were observed depending on time ("calming" effect), no significant difference was observed between exposure and sham exposure to microwaves. In view of the small scatter of the data the present study rules out physiologically relevant effects of moderate energy (59.7 microW/cm2) microwaves varying from 5.8 to 110 GHz on cardiovascular function.

Colloidal Fouling of Nanofiltration Membranes: Development of a Standard Operating Procedure

PubMed Central

Al Mamun, Md Abdullaha; Bhattacharjee, Subir; Pernitsky, David; Sadrzadeh, Mohtada

2017-01-01

Fouling of nanofiltration (NF) membranes is the most significant obstacle to the development of a sustainable and energy-efficient NF process. Colloidal fouling and performance decline in NF processes is complex due to the combination of cake formation and salt concentration polarization effects, which are influenced by the properties of the colloids and the membrane, the operating conditions of the test, and the solution chemistry. Although numerous studies have been conducted to investigate the influence of these parameters on the performance of the NF process, the importance of membrane preconditioning (e.g., compaction and equilibrating with salt water), as well as the determination of key parameters (e.g., critical flux and trans-membrane osmotic pressure) before the fouling experiment have not been reported in detail. The aim of this paper is to present a standard experimental and data analysis protocol for NF colloidal fouling experiments. The developed methodology covers preparation and characterization of water samples and colloidal particles, pre-test membrane compaction and critical flux determination, measurement of experimental data during the fouling test, and the analysis of that data to determine the relative importance of various fouling mechanisms. The standard protocol is illustrated with data from a series of flat sheet, bench-scale experiments. PMID:28106775

Note: A dual temperature closed loop batch reactor for determining the partitioning of trace gases within CO{sub 2}-water systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warr, Oliver, E-mail: oliver.warr@earth.ox.ac.uk; Ballentine, Christopher J.; Rochelle, Christopher A.

An experimental approach is presented which can be used to determine partitioning of trace gases within CO{sub 2}-water systems. The key advantages of this system are (1) The system can be isolated with no external exchange, making it ideal for experiments with conservative tracers. (2) Both phases can be sampled concurrently to give an accurate composition at each phase at any given time. (3) Use of a lower temperature flow loop outside of the reactor removes contamination and facilitates sampling. (4) Rapid equilibration at given pressure/temperature conditions is significantly aided by stirring and circulating the water phase using a magneticmore » stirrer and high-pressure liquid chromatography pump, respectively.« less

Equilibrator: Modeling Chemical Equilibria with Excel

ERIC Educational Resources Information Center

Vander Griend, Douglas A.

2011-01-01

Equilibrator is a Microsoft Excel program for learning about chemical equilibria through modeling, similar in function to EQS4WIN, which is no longer supported and does not work well with newer Windows operating systems. Similar to EQS4WIN, Equilibrator allows the user to define a system with temperature, initial moles, and then either total…

Multi-point estimation of total energy expenditure: a comparison between zinc-reduction and platinum-equilibration methodologies.

PubMed

Sonko, Bakary J; Miller, Leland V; Jones, Richard H; Donnelly, Joseph E; Jacobsen, Dennis J; Hill, James O; Fennessey, Paul V

2003-12-15

Reducing water to hydrogen gas by zinc or uranium metal for determining D/H ratio is both tedious and time consuming. This has forced most energy metabolism investigators to use the "two-point" technique instead of the "Multi-point" technique for estimating total energy expenditure (TEE). Recently, we purchased a new platinum (Pt)-equilibration system that significantly reduces both time and labor required for D/H ratio determination. In this study, we compared TEE obtained from nine overweight but healthy subjects, estimated using the traditional Zn-reduction method to that obtained from the new Pt-equilibration system. Rate constants, pool spaces, and CO2 production rates obtained from use of the two methodologies were not significantly different. Correlation analysis demonstrated that TEEs estimated using the two methods were significantly correlated (r=0.925, p=0.0001). Sample equilibration time was reduced by 66% compared to those of similar methods. The data demonstrated that the Zn-reduction method could be replaced by the Pt-equilibration method when TEE was estimated using the "Multi-Point" technique. Furthermore, D equilibration time was significantly reduced.

High Stress Consolidation, Ultrasonic, and Permeability Measurements: Constraints on Physical Properties and In Situ Stress along the Costa Rica Subduction Plate Interface

NASA Astrophysics Data System (ADS)

Winner, A.; Saffer, D. M.; Valdez, R. D.

2014-12-01

Sediment permeability and consolidation behavior are key parameters in governing the drainage state and thus potential for excess pore fluid pressure in subduction zones. Elevated pore pressure, in turn, is one important control on the strength and sliding behavior of faults. Along many subduction margins, evidence of elevated, near-lithostatic, in situ pore pressure comes from high seismic reflectivity, low P-wave velocity (Vp), and high Vp/Vs ratios. This inference is broadly supported by numerical modeling studies that indicate elevated pore pressures are likely given high rates of burial and tectonic loading, combined with the low permeability of marine mudstones. Here, we report on a series of high-stress consolidation experiments on sediment core samples from the incoming Cocos plate obtained as part of Integrated Ocean Drilling Program (IODP) Expedition 344. Our experiments were designed to measure the consolidation behavior, permeability, and P-wave velocity of the incoming sediments over a range of confining stresses from .5 to 90 MPa. We explore a range of paths,including isostatic loading (σ1=σ2=σ3), K0 consolidation, in which the ratio of σ3/σ1 is maintained at ~0.6, and the trixial loading paths designed to maintain a near critical-state failure condition. In our tests, load is increased in a series of steps. After equilibration at each step, we conduct constant head permeability tests, and measure P-wave velocities in a "time of flight" mode. Initial results from isostatic loading tests on hemipelagic mudstone samples from 34 mbsf document consolidation and permeability-porosity trends, in which porosity decreases from 69% to 54% as stress in increased from .5 MPa to 15 MPa, and permeability decreases from 8.1 X 10-18 m2 at 1 MPa to 1.1 X 10-19 m2 at 15 MPa. P-wave velocity increases by 486-568 km/s over this effective stress range. Ultimately, data from our experiments will provide a robust basis for quantifying fluid content and pressure from seismic velocity and fault plane reflectivity at this margin, and provide data to parameterize forward models of fluid flow and consolidation.

Effect of shortening the prefreezing equilibration time with glycerol on the quality of chamois (Rupicapra pyrenaica), ibex (Capra pyrenaica), mouflon (Ovis musimon) and aoudad (Ammotragus lervia) ejaculates.

PubMed

Pradiee, J; O'Brien, E; Esteso, M C; Castaño, C; Toledano-Díaz, A; Lopez-Sebastián, A; Marcos-Beltrán, J L; Vega, R S; Guillamón, F G; Martínez-Nevado, E; Guerra, R; Santiago-Moreno, J

2016-08-01

The present study reports the effect of shortening the prefreezing equilibration time with glycerol on the quality of frozen-thawed ejaculated sperm from four Mediterranean mountain ungulates: Cantabrian chamois (Rupicapra pyrenaica), Iberian ibex (Capra pyrenaica), mouflon (Ovis musimon) and aoudad (Ammotragus lervia). Ejaculated sperm from these species were divided into two aliquots. One was diluted with either a Tris-citric acid-glucose based medium (TCG-glycerol; for chamois and ibex sperm) or a Tris-TES-glucose-based medium (TTG-glycerol; for mouflon and aoudad sperm), and maintained at 5°C for 3h prior to freezing. The other aliquot was diluted with either TCG (chamois and ibex sperm) or TTG (mouflon and aoudad sperm) and maintained at 5°C for 1h before adding glycerol (final concentration 5%). After a 15min equilibration period in the presence of glycerol, the samples were frozen. For the ibex, there was enhanced (P<0.05) sperm viability and acrosome integrity after the 3h as compared with the 15min equilibration time. For the chamois, subjective sperm motility and cell membrane functional integrity were less (P<0.05) following 15min of equilibration. In the mouflon, progressive sperm motility and acrosome integrity was less (P<0.05) when the equilibration time was reduced to 15min. For the aoudad, the majority of sperm variables measured were more desirable after the 3h equilibration time. The freezing-thawing processes reduced the sperm head size in all the species studied; however, the equilibration time further affected the frozen-thawed sperm head variables in a species-dependent fashion. While the equilibration time for chamois sperm might be shortened, this appears not to be the case for all ungulates. Copyright © 2016 Elsevier B.V. All rights reserved.

Testing Neoclassical Competitive Theory in Multilateral Decentralized Markets

ERIC Educational Resources Information Center

List, John A.

2004-01-01

Walrasian tatonnement has been a fundamental assumption in economics ever since Walras' general equilibrium theory was introduced in 1874. Nearly a century after its introduction, Vernon Smith relaxed the Walrasian tatonnement assumption by showing that neoclassical competitive market theory explains the equilibrating forces in "double-auction"…

Diffusive Transport and Structural Properties of Liquid Iron Alloys at High Pressure

NASA Astrophysics Data System (ADS)

Posner, E.; Rubie, D. C.; Steinle-Neumann, G.; Frost, D. J.

2017-12-01

Diffusive transport properties of liquid iron alloys at high pressures (P) and temperatures (T) place important kinetic constraints on processes related to the origin and evolution of planetary cores. Earth's core composition is largely controlled by the extent of chemical equilibration achieved between liquid metal bodies and a silicate magma ocean during core formation, which can be estimated using chemical diffusion data. In order to estimate the time and length scales of metal-silicate chemical equilibration, we have measured chemical diffusion rates of Si, O and Cr in liquid iron over the P-T range of 1-18 GPa and 1873-2643 K using a multi-anvil apparatus. We have also performed first-principles molecular dynamic simulations of comparable binary liquid compositions, in addition to pure liquid Fe, over a much wider P-T range (1 bar-330 GPa, 2200-5500 K) in order to both validate the simulation results with experimental data at conditions accessible in the laboratory and to extend our dataset to conditions of the Earth's core. Over the entire P-T range studied using both methods, diffusion coefficients are described consistently and well using an exponential function of the homologous temperature relation. Si, Cr and Fe diffusivities of approximately 5 × 10-9 m2 s-1 are constant along the melting curve from ambient to core pressures, while oxygen diffusion is 2-3 times faster. Our results indicate that in order for the composition of the Earth's core to represent chemical equilibrium, impactor cores must have broken up into liquid droplet sizes no larger than a few tens of cm. Structural properties, analyzed using partial radial distribution functions from the molecular dynamics simulations, reveal a pressure-induced structural change in liquid Fe0.96O0.04 at densities of 8 g cm-3, in agreement with previous experimental studies. For densities above 8 g cm-3, the liquid is essentially close packed with a local CsCl-like (B2) packing of Fe around O under conditions of the Earth's core.

Early Earth differentiation [rapid communication

NASA Astrophysics Data System (ADS)

Walter, Michael J.; Trønnes, Reidar G.

2004-09-01

The birth and infancy of Earth was a time of profound differentiation involving massive internal reorganization into core, mantle and proto-crust, all within a few hundred million years of solar system formation ( t0). Physical and isotopic evidence indicate that the formation of iron-rich cores generally occurred very early in planetesimals, the building blocks of proto-Earth, within about 3 million years of t0. The final stages of terrestrial planetary accretion involved violent and tremendously energetic giant impacts among core-segregated Mercury- to Mars-sized objects and planetary embryos. As a consequence of impact heating, the early Earth was at times partially or wholly molten, increasing the likelihood for high-pressure and high-temperature equilibration among core- and mantle-forming materials. The Earth's silicate mantle harmoniously possesses abundance levels of the siderophile elements Ni and Co that can be reconciled by equilibration between iron alloy and silicate at conditions comparable to those expected for a deep magma ocean. Solidification of a deep magma ocean possibly involved crystal-melt segregation at high pressures, but subsequent convective stirring of the mantle could have largely erased nascent layering. However, primitive upper mantle rocks apparently have some nonchondritic major and trace element refractory lithophile element ratios that can be plausibly linked to early mantle differentiation of ultra-high-pressure mantle phases. The geochemical effects of crystal fractionation in a deep magma ocean are partly constrained by high-pressure experimentation. Comparison between compositional models for the primitive convecting mantle and bulk silicate Earth generally allows, and possibly favors, 10-15% total fractionation of a deep mantle assemblage comprised predominantly of Mg-perovskite and with minor but geochemically important amounts of Ca-perovskite and ferropericlase. Long-term isolation of such a crystal pile is generally consistent with isotopic constraints for time-integrated Sm/Nd and Lu/Hf ratios in the modern upper mantle and might account for the characteristics of some mantle isotope reservoirs. Although much remains to be learned about the earliest formative period in the Earth's development, a convergence of theoretical, physical, isotopic and geochemical arguments is beginning to yield a self-consistent portrait of the infant Earth.

Modeling the movement and equilibrium of water in the body of ruminants in relation to estimating body composition by deuterium oxide dilution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnold, R.N.

1986-01-01

Deuterium oxide (D/sub 2/O) dilution was evaluated for use in estimating body composition of ruminants. Empty body composition of cattle could not be accurately estimated by two- or three-compartment models when solved on the basis of clearance of D/sub 2/O from blood. A 29-compartment blood-flow model was developed from measured blood flow rates and water volumes of tissues of sheep. The rates of equilibration of water in tissues that were simulated by the blood-flow model were much faster than actual rates measured in sheep and cattle. The incorporation of diffusion hindrances for movement of water into tissues enabled the bloodmore » flow model to simulate the measured equilibration rates in tissues, but the values of the diffusion coefficients were different for each tissue. The D/sub 2/O-disappearance curve for blood simulated by the blood-flow model with diffusion limitations was comprised for four exponential components. The tissues and gastrointestinal tract contents were placed into five groups based upon the rate of equilibration. Water in the organs of the body equilibrated with water in blood within 3 min. Water in visceral fat, head, and some of the gastrointestinal tract tissues equilibrated within 8 to 16 min. Water in skeletal muscle, fat, and bone and the contents of some segments of the gastrointestinal tract equilibrated within 30 to 36 min. Water in the tissues and contents of the cecum and upper-large intestine equilibrated within 160 to 200 min. Water in ruminal tissue and contents equilibrated within 480 min.« less

Oxygen deficient Ti oxides (natural magnéli phases) from mudstone xenoliths with native iron from Disko, central West Greenland

NASA Astrophysics Data System (ADS)

Pedersen, A. K.; Rønsbo, J. G.

1987-05-01

Mudstone xenoliths in a strongly reduced andesitic subaquatic breccia with native iron from the Asuk Member on Disko contain Ti oxides which are oxygen deficient relative to rutile. Ore microscopy reveals that the mudstone xenoliths contain former clastic oxide grains which have equilibrated to blue Ti oxides and grey aluminous Ti oxides. They also contain still immature coal fragments in a glassy matrix with native iron. The blue oxides are compositionally similar to magnéli phases TinO2n-1 within the range n=4 to 7, and several grains contain more than one natural magnéli phase. Two other phases found are 1) pale orange blebs in magnéli phases with a composition approaching Al1Ti{1/3+}Ti{2/4+}O7 (AlTi phase B) and 2) grey oxide rims on magnéli phases or independent grains of the compositional series Al2-x(Ti{0.5/4+}(Mg,Fe)0.5)xTi{n-2/4+}O2n-1 with n mostly between 7 and 10 (AlTi phase A). The natural magnéli phases equilibrated at oxygen fugacities 4 to 5 log units below the Fe-W oxygen buffer at igneous temperatures and represent the most reduced high-temperature environment yet recorded among native iron bearing rocks from Disko. The extremely reducing conditions were met in rocks where coal fragments were still in a state of degassing hydrocarbon components at the time of quenching. Field geology and carbon barometry indicate equilibration at pressures of less than 10 bars.

The Thermal States of Accreting Planets: From Mars-like Embryos to a MAD Earth

NASA Astrophysics Data System (ADS)

Stewart, S. T.; Lock, S. J.

2015-12-01

The thermal states of rocky planets can vary widely during the process of accretion. The thermal structure affects several major processes on the growing planet, including the mechanics of core formation, pressure-temperature conditions for metal-silicate equilibration, mixing, and atmospheric erosion. Because impact energy is distributed heterogeneously, accretional energy is preferentially deposited in the gravitationally re-equilibrated outer layers of the planet for both small and giant impacts. The resulting stably stratified structure inhibits complete mixing within the mantle. Initially, the specific energy of giant impacts between Mars-mass embryos leads to melting of the mantle. However, as planet formation progresses, the specific energies of giant impacts increase and can drive the mantle into a transient supercritical state. In the hottest regions of the planet, metal and silicates are miscible, and metal exsolution occurs as the structure cools. The cooling time of the supercritical structure is typically longer than the timescale for metal segregation to the core. Thus, these high temperature excursions during planet formation are significant for understanding metal-silicate equilibration. Furthermore, when a supercritical planet is also rapidly rotating, the mantle, atmosphere and disk (MAD) form a continuous dynamic and thermodynamic structure. Lunar origin by condensation from a MAD Earth can explain the major characteristics of the Moon (Lock et al., this meeting). One of the greatest uncertainties in understanding the thermal states of planets during accretion is the changing composition and mass of the atmosphere. After the dispersal of the solar nebula, the thermal boundary condition imposed by the atmosphere can vary between silicate vapor and condensed ices. The coupled problem of atmospheric origin and planetary accretion can be used to constrain the many uncertainties in the growth and divergence of the terrestrial planets in our solar system.

Crosstalk between the equilibrative nucleoside transporter ENT2 and alveolar Adora2b adenosine receptors dampens acute lung injury

PubMed Central

Eckle, Tobias; Hughes, Kelly; Ehrentraut, Heidi; Brodsky, Kelley S.; Rosenberger, Peter; Choi, Doo-Sup; Ravid, Katya; Weng, Tingting; Xia, Yang; Blackburn, Michael R.; Eltzschig, Holger K.

2013-01-01

The signaling molecule adenosine has been implicated in attenuating acute lung injury (ALI). Adenosine signaling is terminated by its uptake through equilibrative nucleoside transporters (ENTs). We hypothesized that ENT-dependent adenosine uptake could be targeted to enhance adenosine-mediated lung protection. To address this hypothesis, we exposed mice to high-pressure mechanical ventilation to induce ALI. Initial studies demonstrated time-dependent repression of ENT1 and ENT2 transcript and protein levels during ALI. To examine the contention that ENT repression represents an endogenous adaptive response, we performed functional studies with the ENT inhibitor dipyridamole. Dipyridamole treatment (1 mg/kg; EC50=10 μM) was associated with significant increases in ALI survival time (277 vs. 395 min; P<0.05). Subsequent studies in gene-targeted mice for Ent1 or Ent2 revealed a selective phenotype in Ent2−/− mice, including attenuated pulmonary edema and improved gas exchange during ALI in conjunction with elevated adenosine levels in the bronchoalveolar fluid. Furthermore, studies in genetic models for adenosine receptors implicated the A2B adenosine receptor (Adora2b) in mediating ENT-dependent lung protection. Notably, dipyridamole-dependent attenuation of lung inflammation was abolished in mice with alveolar epithelial Adora2b gene deletion. Our newly identified crosstalk pathway between ENT2 and alveolar epithelial Adora2b in lung protection during ALI opens possibilities for combined therapies targeted to this protein set.—Eckle, T., Hughes, K., Ehrentraut, H., Brodsky, K. S., Rosenberger, P., Choi, D.-S., Ravid, K., Weng, T., Xia, Y., Blackburn, M. R., Eltzschig, H. K. Crosstalk between the equilibrative nucleoside transporter ENT2 and alveolar Adora2b adenosine receptors dampens acute lung injury. PMID:23603835

Metamorphic P-T conditions and CO2 influx history of medium-grade metapelites from Karakorum, Trans-Himalaya, India

NASA Astrophysics Data System (ADS)

Sachan, Himanshu K.; Santosh, M.; Prakash, Divya; Kharya, Aditya; Chandra Singh, P.; Rai, Santosh K.

2016-07-01

The medium grade metapelites of Pangong-Tso area in the trans-Himalayan region underwent sillimanite-grade metamorphism initiated during the Cretaceous, associated with the collision of the Kohistan arc and the Indian plate with Asia. This paper present results from a petrological and fluid inclusion study to understand the metamorphic P-T conditions and fluid history of these rocks. The calculated phase equilibria in the Na2O-CaO-K2O-FeO-MgO-MnO-Al2O3-SiO2-H2O-TiO2 (NCKFMMnASHT) system suggest P-T conditions of 8 kbar and 650 °C for the peak metamorphic event. Primary fluid inclusions occur in staurolite and garnet, whereas quartz carries mostly secondary fluid inclusions. The trapped fluids in primary inclusions show initial melting temperatures in the range of -56.9 to -56.6 °C, suggesting nearly pure CO2 composition. The secondary fluids are of mixed carbonic-aqueous nature. The re-equilibrated inclusions show annular morphology as well as necking phenomena. The CO2 isochores for the primary inclusions indicate pressures of 6.1-6.7 kbar, suggesting that the CO2-rich fluids were trapped during post-peak exhumation of the rocks, or that synmetamorphic carbonic fluids underwent density reversal during isothermal decompression. The secondary CO2-H2O fluids must have been trapped during the late exhumation stage, as their isochores define further lower pressures of 4.8 kbar. The morphology of re-equilibrated fluid inclusions and the rapid decrease in pressure are consistent with a near-isothermal decompression trajectory following the peak metamorphism. The carbonic fluids were probably derived locally from decarbonation reactions of the associated carbonate rocks during metamorphism or from a deep-seated reservoir through Karakorum fault.

Melt inclusion constraints on petrogenesis of the 2014-2015 Holuhraun eruption, Iceland

NASA Astrophysics Data System (ADS)

Hartley, Margaret E.; Bali, Enikö; Maclennan, John; Neave, David A.; Halldórsson, Sæmundur A.

2018-02-01

The 2014-2015 Holuhraun eruption, on the Bárðarbunga volcanic system in central Iceland, was one of the best-monitored basaltic fissure eruptions that has ever occurred, and presents a unique opportunity to link petrological and geochemical data with geophysical observations during a major rifting episode. We present major and trace element analyses of melt inclusions and matrix glasses from a suite of ten samples collected over the course of the Holuhraun eruption. The diversity of trace element ratios such as La/Yb in Holuhraun melt inclusions reveals that the magma evolved via concurrent mixing and crystallization of diverse primary melts in the mid-crust. Using olivine-plagioclase-augite-melt (OPAM) barometry, we calculate that the Holuhraun carrier melt equilibrated at 2.1 ± 0.7 kbar (7.5 ± 2.5 km), which is in agreement with the depths of earthquakes (6 ± 1 km) between Bárðarbunga central volcano and the eruption site in the days preceding eruption onset. Using the same approach, melt inclusions equilibrated at pressures between 0.5 and 8.0 kbar, with the most probable pressure being 3.2 kbar. Diffusion chronometry reveals minimum residence timescales of 1-12 days for melt inclusion-bearing macrocrysts in the Holuhraun carrier melt. By combining timescales of diffusive dehydration of melt inclusions with the calculated pressure of H2O saturation for the Holuhraun magma, we calculate indicative magma ascent rates of 0.12-0.29 m s-1. Our petrological and geochemical data are consistent with lateral magma transport from Bárðarbunga volcano to the eruption site in a shallow- to mid-crustal dyke, as has been suggested on the basis of seismic and geodetic datasets. This result is a significant step forward in reconciling petrological and geophysical interpretations of magma transport during volcano-tectonic episodes, and provides a critical framework for the interpretation of premonitory seismic and geodetic data in volcanically active regions.

High Pressure/Temperature Metal Silicate Partitioning of Tungsten

NASA Technical Reports Server (NTRS)

Shofner, G. A.; Danielson, L.; Righter, K.; Campbell, A. J.

2010-01-01

The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. <10 GPa, and in two cases at or near 20 GPa. According to those data, the stronger influences on the distribution coefficient of W are temperature, composition, and oxygen fugacity with a relatively slight influence in pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

Pressure dependence of the photocycle kinetics of bacteriorhodopsin.

PubMed Central

Klink, B U; Winter, R; Engelhard, M; Chizhov, I

2002-01-01

The pressure dependence of the photocycle kinetics of bacteriorhodopsin from Halobacterium salinarium was investigated at pressures up to 4 kbar at 25 degrees C and 40 degrees C. The kinetics can be adequately modeled by nine apparent rate constants, which are assigned to irreversible transitions of a single relaxation chain of nine kinetically distinguishable states P(1) to P(9). All states except P(1) and P(9) consist of two or more spectral components. The kinetic states P(2) to P(6) comprise only the two fast equilibrating spectral states L and M. From the pressure dependence, the volume differences DeltaV(o)(LM) between these two spectral states could be determined that range from DeltaV(o)(LM) = -11.4 +/- 0.7 ml/mol (P(2)) to DeltaV(o)(LM) = 14.6 +/- 2.8 mL/mol (P(6)). A model is developed that explains the dependence of DeltaV(o)(LM) on the kinetic state by the electrostriction effect of charges, which are formed and neutralized during the L/M transition. PMID:12496115

Impact Vaporization of Planetesimal Cores

NASA Astrophysics Data System (ADS)

Kraus, R. G.; Root, S.; Lemke, R. W.; Stewart, S. T.; Jacobsen, S. B.; Mattsson, T. R.

2013-12-01

The degree of mixing and chemical equilibration between the iron cores of planetesimals and the mantle of the growing Earth has important consequences for understanding the end stages of Earth's formation and planet formation in general. At the Sandia Z machine, we developed a new shock-and-release technique to determine the density on the liquid-vapor dome of iron, the entropy on the iron shock Hugoniot, and the criteria for shock-induced vaporization of iron. We find that the critical shock pressure to vaporize iron is 507(+65,-85) GPa and show that decompression from a 15 km/s impact will initiate vaporization of iron cores, which is a velocity that is readily achieved at the end stages of planet formation. Vaporization of the iron cores increases dispersal of planetesimal cores, enables more complete chemical equilibration of the planetesimal cores with Earth's mantle, and reduces the highly siderophile element abundance on the Moon relative to Earth due to the expanding iron vapor exceeding the Moon's escape velocity. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Securities Administration under Contract No. DE-AC04-94AL85000.

Low-Ca pyroxenes from LL group chondritic meteorites: Crystal structural studies and implications for their thermal histories

NASA Astrophysics Data System (ADS)

Artioli, G.; Davoli, G.

1994-12-01

Crystal structural refinements of one orthorhombic (Pbca) and two monoclinic (P21/c) single crystals, from chondrules of low-Ca pyroxenes from unequilibrated chondritic meteorites of the LL group, were carried out. The intracrystalline Fe-Mg distribution between the M1 and M2 crystallographic sites of the Parnallee (LL-3) orthoenstatite is suggestive of very rapid cooling, whereas both the structural state and intracrystalline Fe-Mg distribution in the Soko Banja (LL-4) and Jolomba (LL-6) clinoenstaties indicate rapid cooling from the high temperature polymorphs, with no significant re-equilibration at lower temperatures. These results imply that thermal metamorphism in the parent body, if present, was insufficient to allow re-equilibration of the pyroxene minerals to low temperature, ordered crystal structures. The data also indicate that, assuming low or mild pressure and shock effects, there is no well defined correlation between equilibrium temperature of the mineral phases and the alleged petrologic type of the meteorites. This evidence is consistent with a rubble pile model for the parent body accretional history, or with an onion shell model with very low thermal peak metamorphism, as is assumed for a very small object.

Multiscale approach for the construction of equilibrated all-atom models of a poly(ethylene glycol)-based hydrogel

PubMed Central

Li, Xianfeng; Murthy, N. Sanjeeva; Becker, Matthew L.; Latour, Robert A.

2016-01-01

A multiscale modeling approach is presented for the efficient construction of an equilibrated all-atom model of a cross-linked poly(ethylene glycol) (PEG)-based hydrogel using the all-atom polymer consistent force field (PCFF). The final equilibrated all-atom model was built with a systematic simulation toolset consisting of three consecutive parts: (1) building a global cross-linked PEG-chain network at experimentally determined cross-link density using an on-lattice Monte Carlo method based on the bond fluctuation model, (2) recovering the local molecular structure of the network by transitioning from the lattice model to an off-lattice coarse-grained (CG) model parameterized from PCFF, followed by equilibration using high performance molecular dynamics methods, and (3) recovering the atomistic structure of the network by reverse mapping from the equilibrated CG structure, hydrating the structure with explicitly represented water, followed by final equilibration using PCFF parameterization. The developed three-stage modeling approach has application to a wide range of other complex macromolecular hydrogel systems, including the integration of peptide, protein, and/or drug molecules as side-chains within the hydrogel network for the incorporation of bioactivity for tissue engineering, regenerative medicine, and drug delivery applications. PMID:27013229

Numerical Simulation of Laser Ablative Shock Waves From Aluminum in Presence of Helium Gas At Different Ambient Pressures

NASA Astrophysics Data System (ADS)

Paturi, Prem Kiran; Durvasula, P. S. L. Kameswari; S, Sai Shiva; Acrhem, University Of Hyderabad Team

2017-06-01

A two dimensional comparative study of Laser Ablative Shock Wave into the Aluminum target in the presence of Helium gas at different ambient pressures over a range of 690 - 105 Pa performed using FLASH hydrodynamic codes will be presented. The irradiation of Aluminum target (thickness 2 mm and radius 3 mm) with a 7 ns laser pulse of energy 175 mJ, spot size of 150 µm on the target surface at a wavelength of 532 nm at normal incidence is simulated. Helium gas enclosed in a chamber of height 3 mm and width 3 mm. The electron-ion inverse bremsstrahlung absorption coefficient is considered in the laser energy deposition process. The simulation was performed over a duration of 1 μs. It was observed that an ablative shock is launched into the Helium gas for the pressures of 0.5 atm and above. However, for pressure less than the 0.5 atm the plasma expanded into the He gas upto 12ns and after which due to pressure equilibration with the surroundings and plume splitting shock wave is launched in to Al. Authors acknowledge funding from DRDO, India.

Direct visualization of the arterial wall water permeability barrier using CARS microscopy

PubMed Central

Lucotte, Bertrand M.; Powell, Chloe; Knutson, Jay R.; Combs, Christian A.; Malide, Daniela; Yu, Zu-Xi; Knepper, Mark; Patel, Keval D.; Pielach, Anna; Johnson, Errin; Borysova, Lyudmyla; Balaban, Robert S.

2017-01-01

The artery wall is equipped with a water permeation barrier that allows blood to flow at high pressure without significant water leak. The precise location of this barrier is unknown despite its importance in vascular function and its contribution to many vascular complications when it is compromised. Herein we map the water permeability in intact arteries, using coherent anti-Stokes Raman scattering (CARS) microscopy and isotopic perfusion experiments. Generation of the CARS signal is optimized for water imaging with broadband excitation. We identify the water permeation barrier as the endothelial basolateral membrane and show that the apical membrane is highly permeable. This is confirmed by the distribution of the AQP1 water channel within endothelial membranes. These results indicate that arterial pressure equilibrates within the endothelium and is transmitted to the supporting basement membrane and internal elastic lamina macromolecules with minimal deformation of the sensitive endothelial cell. Disruption of this pressure transmission could contribute to endothelial cell dysfunction in various pathologies. PMID:28373558

HSE Abundances in Angrites and HEDs: Core-Mantle Equilibration or Late Accretion Addition of a Chondritic Component

NASA Astrophysics Data System (ADS)

Rai, N.; Downes, H.; Smith, C. L.

2016-08-01

Using metal-silicate partitioning of HSEs together with their mantle abundances in Vesta and the APB respectively, we test whether formation of a metallic core could have led to the observed abundances of the HSEs, in the mantles of these bodies.

Advanced structural analysis of nanoporous materials by thermal response measurements.

PubMed

Oschatz, Martin; Leistner, Matthias; Nickel, Winfried; Kaskel, Stefan

2015-04-07

Thermal response measurements based on optical adsorption calorimetry are presented as a versatile tool for the time-saving and profound characterization of the pore structure of porous carbon-based materials. This technique measures the time-resolved temperature change of an adsorbent during adsorption of a test gas. Six carbide and carbon materials with well-defined nanopore architecture including micro- and/or mesopores are characterized by thermal response measurements based on n-butane and carbon dioxide as the test gases. With this tool, the pore systems of the model materials can be clearly distinguished and accurately analyzed. The obtained calorimetric data are correlated with the adsorption/desorption isotherms of the materials. The pore structures can be estimated from a single experiment due to different adsorption enthalpies/temperature increases in micro- and mesopores. Adsorption/desorption cycling of n-butane at 298 K/1 bar with increasing desorption time allows to determine the pore structure of the materials in more detail due to different equilibration times. Adsorption of the organic test gas at selected relative pressures reveals specific contributions of particular pore systems to the increase of the temperature of the samples and different adsorption mechanisms. The use of carbon dioxide as the test gas at 298 K/1 bar provides detailed insights into the ultramicropore structure of the materials because under these conditions the adsorption of this test gas is very sensitive to the presence of pores smaller than 0.7 nm.

Experimental pressure enhancement of the rate of homogenous methanogenesis: implications for abiotic methane yields in terrestrial and planetary environments

NASA Astrophysics Data System (ADS)

Lazar, C.; Cody, G. D.

2011-12-01

Abiotic methane may play a role in the development of a biosphere on an otherwise lifeless planet. Methane concentrations in fluids emanating from serpentinite-hosted submarine springs such as Rainbow and Logatchev are below that required for equilibrium with coexisting CO2 and H2, indicating that the compositions of such fluids may be kinetically-controlled. The presence of transition metal-bearing accessory minerals in serpentinites has led to the hypothesis that heterogeneous catalysis may influence the rate of methanogenesis. We present new experiments that show pressure can also significantly accelerate homogenous methanogenesis, i.e., methane production in the absence of mineral catalysts. A series of cold-seal experiments were performed from 1-3.5 kbar at 300C for two weeks, using dilute isotopically labeled formic acid as a carbon and hydrogen source (70mmol solution). The experiments showed a significant increase in 13CH4 yield with pressure: e.g., the yield at 3.5 kbar was ~20X the yield at 1 kbar. This pressure enhancement is consistent with our previous results on homogeneous and heterogeneous methanogenesis and suggests that mineral catalysts are not necessary for CH4 equilibration in high pressure environments such as Precambrian crystalline basements or regional blueschist-grade metamorphic systems. Furthermore, in hydrothermal systems wherein fluid residence times are too short to permit equilibration, the reaction progress of methanogenesis is expected to increase with pressure. Recently discovered methane plumes above the mid-Cayman trough have been attributed to methanogenesis in deep serpentinites-hosted springs. The current experimental results lead to the prediction that the mid-Cayman springs (>1 kbar) contain higher methane concentrations than their lower pressure analogues at Rainbow and Logatchev (<0.5kbar). Fluids escaping forearc serpentinization in cold, steeply-dipping subduction zones may yield more methane than in warm shallow-dipping subduction zones, consistent with the detection of abiotic CH4 in serpentine mud along the Marianas forearc. The methane production rate from water-rock interaction on a deep planetary seafloor may be higher than from analogous terrestrial settings: e.g, on Europa (2.5 kbar seafloor) and Titan (8 kbar seafloor). Since many of the mineral catalysts commonly found in serpentinites (awaruite, heazlewoodite, e.g.) are not present during basaltic metamorphism, the potential for pressure-enhanced homogenous methanogenesis presents the possibility that deep hydrothermal alteration of the basaltic Martian crust could be the source for atmospheric methane on Mars. If methanogenic microbes are sustained by an energy imbalance made possible by kinetic barriers to the reduction of CO2 to CH4, then the habitability of hydrothermal systems with respect to methanogens may decrease with depth as the reaction progress of methanogenesis increases.

Hormonal regulation of fluid and electrolyte metabolism during periods of headward fluid shifts

NASA Technical Reports Server (NTRS)

Keil, Lanny C.; Severs, W. B.; Thrasher, T.; Ramsay, D. J.

1991-01-01

In the broadest sense, this project evaluates how spaceflight induced shifts of blood and interstitial fluids into the thorax affect regulation by the central nervous system (CNS) of fluid-electrolyte hormone secretion. Specifically, it focuses on the role of hormones related to salt/water balance and their potential function in the control of intracranial pressure and cerebrospinal fluid (CSF) composition. Fluid-electrolyte status during spaceflight gradually equilibrates, with a reduction in all body fluid compartments. Related to this is the cardiovascular deconditioning of spaceflight which is manifested upon return to earth as orthostatic intolerance.

Productions of Volatile Organic Compounds (VOCs) in Surface Waters from Reactions with Atmospheric Ozone

NASA Astrophysics Data System (ADS)

Hopkins, Frances; Bell, Thomas; Yang, Mingxi

2017-04-01

Ozone (O3) is a key atmospheric oxidant, greenhouse gas and air pollutant. In marine environments, some atmospheric ozone is lost by reactions with aqueous compounds (e.g. dissolved organic material, DOM, dimethyl sulfide, DMS, and iodide) near the sea surface. These reactions also lead to formations of volatile organic compounds (VOCs). Removal of O3 by the ocean remains a large uncertainty in global and regional chemical transport models, hampering coastal air quality forecasts. To better understand the role of the ocean in controlling O3 concentrations in the coastal marine atmosphere, we designed and implemented a series of laboratory experiments whereby ambient surface seawater was bubbled with O3-enriched, VOC-free air in a custom-made glass bubble equilibration system. Gas phase concentrations of a range of VOCs were monitored continuously over the mass range m/z 33 - 137 at the outflow of the bubble equilibrator by a proton transfer reaction - mass spectrometer (PTR-MS). Gas phase O3 was also measured at the input and output of the equilibrator to monitor the uptake due to reactions with dissolved compounds in seawater. We observed consistent productions of a variety of VOCs upon reaction with O3, notably isoprene, aldehydes, and ketones. Aqueous DMS is rapidly removed from the reactions with O3. To test the importance of dissolved organic matter precursors, we added increasing (milliliter) volumes of Emiliania huxleyi culture to the equilibrator filled with aged seawater, and observed significant linear increases in gas phase concentrations of a number of VOCs. Reactions between DOM and O3 at the sea-air interface represent a potentially significant source of VOCs in marine air and a sink of atmospheric O3.

Water in orthopyroxene from abyssal spinel peridotites of the East Pacific Rise (ODP Leg 147: Hess Deep)

NASA Astrophysics Data System (ADS)

Hesse, Kirsten T.; Gose, Jürgen; Stalder, Roland; Schmädicke, Esther

2015-09-01

Abyssal spinel peridotites from Hess Deep, East Pacific Rise (ODP Leg 147) were investigated concerning their major, minor, and trace element mineral chemistry and the incorporation of structural water in orthopyroxene. The rocks are partially serpentinized harzburgites containing primary minerals of olivine, orthopyroxene, clinopyroxene, and spinel. Orthopyroxene is enstatitic with Mg# (Mg/(Mg + Fe)) between 0.90 and 0.92 and Al2O3 from 0.5 to 2.9 wt.%. The residual harzburgite experienced high degrees of melt removal in the spinel peridotite stability field. The average degree of partial melting was calculated to be 17.5% (range: 16.4-17.8%). Trace element data of ortho- and clinopyroxenes reflect this strong depletion, characteristic for the restitic nature of abyssal peridotites. Mantle re-equilibration temperatures around 1000 °C indicate that, after melt extraction and before exhumation to the ocean floor, the rocks experienced significant cooling in the spinel peridotite facies. Water contents of orthopyroxene range from 86 to 233 wt. ppm H2O with an average concentration of 142 wt. ppm H2O. These results represent the first data on water contents in the sub-pacific mantle obtained by direct measurements of sub-oceanic peridotite. The water contents are not related to mineral chemistry, stratigraphy, melting degree, mantle equilibrium conditions or oxidation state. Calculated post-melt peridotite water contents vary between 40 and 100 wt. ppm H2O. Compared to Mid-Atlantic Ridge peridotites, the East Pacific Rise samples of Leg 147 contain somewhat lower water concentrations than samples from Leg 153 and considerably higher contents than those of Leg 209 (Gose et al., 2009; Schmädicke et al., 2011). In Leg 147, the strongest OH absorbtion band occurs at 3420 cm- 1, wheras orthopyroxene from MAR peridotite (Legs 153 and 209) has its strongest absorbtion band at 3566 and 3522 cm- 1. The mantle equilibrium temperature of Leg 147 peridotites is lower than that of Leg 209 ( 1250 °C) but close to that of Leg 153 samples (950-1000 °C). The high degree of partial melting of Leg 147 peridotite samples overlaps with the Leg 209 samples. In accordance to this data we conclude that in order to obtain relatively high water contents of up to 233 wt. ppm in depleted peridotite, after melt removal water must have re-entered the orthopyroxene structure. We suggest that re-equilibration of water contents took place under spinel-facies conditions before exhumation of the tectonite, since elevated temperatures enhance diffusion and elevated pressures facilitate hydrogen uptake. The extended time span between melt removal and uplift inferred from significant isobaric cooling of at least 200 K at spinel-facies depth facilitates re-equilibration of water contents and may explain the high concentrations. Exhumation from spinel-facies depth was fast and accompanied by further cooling such that re-equilibration to lower pressure assemblages and decompression-induced water loss were prevented.

The Construction and Validation of All-Atom Bulk-Phase Models of Amorphous Polymers Using the TIGER2/TIGER3 Empirical Sampling Method

PubMed Central

Li, Xianfeng; Murthy, Sanjeeva; Latour, Robert A.

2011-01-01

A new empirical sampling method termed “temperature intervals with global exchange of replicas and reduced radii” (TIGER3) is presented and demonstrated to efficiently equilibrate entangled long-chain molecular systems such as amorphous polymers. The TIGER3 algorithm is a replica exchange method in which simulations are run in parallel over a range of temperature levels at and above a designated baseline temperature. The replicas sampled at temperature levels above the baseline are run through a series of cycles with each cycle containing four stages – heating, sampling, quenching, and temperature level reassignment. The method allows chain segments to pass through one another at elevated temperature levels during the sampling stage by reducing the van der Waals radii of the atoms, thus eliminating chain entanglement problems. Atomic radii are then returned to their regular values and re-equilibrated at elevated temperature prior to quenching to the baseline temperature. Following quenching, replicas are compared using a Metropolis Monte Carlo exchange process for the construction of an approximate Boltzmann-weighted ensemble of states and then reassigned to the elevated temperature levels for additional sampling. Further system equilibration is performed by periodic implementation of the previously developed TIGER2 algorithm between cycles of TIGER3, which applies thermal cycling without radii reduction. When coupled with a coarse-grained modeling approach, the combined TIGER2/TIGER3 algorithm yields fast equilibration of bulk-phase models of amorphous polymer, even for polymers with complex, highly branched structures. The developed method was tested by modeling the polyethylene melt. The calculated properties of chain conformation and chain segment packing agreed well with published data. The method was also applied to generate equilibrated structural models of three increasingly complex amorphous polymer systems: poly(methyl methacrylate), poly(butyl methacrylate), and DTB-succinate copolymer. Calculated glass transition temperature (Tg) and structural parameter profile (S(q)) for each resulting polymer model were found to be in close agreement with experimental Tg values and structural measurements obtained by x-ray diffraction, thus validating that the developed methods provide realistic models of amorphous polymer structure. PMID:21769156

Growth of a Bacterium Under a High-Pressure Oxy-Helium Atmosphere †

PubMed Central

Taylor, Craig D.

1979-01-01

Growth of a barotolerant marine organism, EP-4, in a glutamate medium equilibrated with an oxy-helium atmosphere at 500 atmospheres (atm; total pressure) (20°C) was compared with control cultures incubated at hydrostatic pressures of 1 and 500 atm. Relative to the 1-atm control culture, incubation of EP-4 at 500 atm in the absence of an atmosphere resulted in an approximately fivefold reduction in the growth rate and a significant but time variant reduction in the rate constants for the incorporation of substrate into cell material and respiration. Distinct from the pressurized control and separate from potential effects of dissolution of helium upon decompression of subsamples, exposure of the organism to high-pressure oxy-helium resulted in either a loss of viability of a large fraction of the cells or the arrest of growth for one-third of the experimental period. After these initial effects, however, the culture grew exponentially at a rate which was three times greater than the 500-atm control culture. The rate constant for the incorporation of substrate into cell material was also enhanced twofold in the presence of high-pressure oxy-helium. Dissolved oxygen was well controlled in all of the cultures, minimizing any potential toxic effects of this gas. PMID:16345337

A critical Examination of the Phenomenon of Bonding Area - Bonding Strength Interplay in Powder Tableting.

PubMed

Osei-Yeboah, Frederick; Chang, Shao-Yu; Sun, Changquan Calvin

2016-05-01

Although the bonding area (BA) and bonding strength (BS) interplay is used to explain complex tableting behaviors, it has never been experimentally proven. The purpose of this study is to unambiguously establish the distinct contributions of each by decoupling the contributions from BA and BS. To modulate BA, a Soluplus® powder was compressed into tablets at different temperatures and then broken following equilibration at 25°C. To modulate BS, tablets were equilibrated at different temperatures. To simultaneously modulate BA and BS, both powder compression and tablet breaking test were carried out at different temperatures. Lower tablet tensile strength is observed when the powder is compressed at a lower temperature but broken at 25°C. This is consistent with the increased resistance to polymer deformation at lower temperatures. When equilibrated at different temperatures, the tensile strength of tablets prepared under identical conditions increases with decreasing storage temperature, indicating that BS is higher at a lower temperature. When powder compression and tablet breaking are carried out at the same temperature, the profile with a maximum tensile strength at 4°C is observed due to the BA-BS interplay. By systematically varying temperature during tablet compression and breaking, we have experimentally demonstrated the phenomenon of BA-BS interplay in tableting.

The Effect of Increased Intracranial Pressure on Vestibular Evoked Myogenic Potentials in Superior Canal Dehiscence Syndrome

PubMed Central

Janky, Kristen L.; Zuniga, M. Geraldine; Schubert, Michael C; Carey, John P

2014-01-01

Objective To determine if vestibular evoked myogenic potential (VEMP) responses change during inversion in patients with superior canal dehiscence syndrome (SCDS) compared to controls. Methods Sixteen subjects with SCDS (mean: 43, range 30–57 years) and 15 age-matched, healthy subjects (mean: 41, range 22–57 years) completed cervical VEMP (cVEMP) in response to air conduction click stimuli and ocular VEMP (oVEMP) in response to air conduction 500 Hz tone burst stimuli and midline tap stimulation. All VEMP testing was completed in semi-recumbent and inverted conditions. Results SCDS ears demonstrated significantly larger oVEMP peak-to-peak amplitudes in comparison to normal ears in semi-recumbency. While corrected cVEMP peak-to-peak amplitudes were larger in SCDS ears; this did not reach significance in our sample. Overall, there was not a differential change in o- or cVEMP amplitude with inversion between SCDS and normal subjects. Conclusions Postural-induced changes in o- and cVEMP responses were measured in the steady state regardless of whether the labyrinth was intact or dehiscent. Significance VEMP responses are blunted during inversion. Although steady-state measurements of VEMPs during inversion do not increase diagnostic accuracy for SCDS, the findings suggest that inversion may provide more general insights into the equilibration of pressures between intracranial and intralabyrinthine fluids. PMID:25103787

A Portable and Autonomous Mass Spectrometric System for On-Site Environmental Gas Analysis.

PubMed

Brennwald, Matthias S; Schmidt, Mark; Oser, Julian; Kipfer, Rolf

2016-12-20

We developed a portable mass spectrometric system ("miniRuedi") for quantificaton of the partial pressures of He, Ne (in dry gas), Ar, Kr, N 2 , O 2 , CO 2 , and CH 4 in gaseous and aqueous matrices in environmental systems with an analytical uncertainty of 1-3%. The miniRuedi does not require any purification or other preparation of the sampled gases and therefore allows maintenance-free and autonomous operation. The apparatus is most suitable for on-site gas analysis during field work and at remote locations due to its small size (60 cm × 40 cm × 14 cm), low weight (13 kg), and low power consumption (50 W). The gases are continuously sampled and transferred through a capillary pressure reduction system into a vacuum chamber, where they are analyzed using a quadrupole mass spectrometer with a time resolution of ≲1 min. The low gas consumption rate (<0.1 mL/min) minimizes interference with the natural mass balance of gases in environmental systems, and allows the unbiased quantification of dissolved-gas concentrations in water by gas/water equilibration using membrane contractors (gas-equilibrium membrane-inlet mass spectrometry, GE-MIMS). The performance of the miniRuedi is demonstrated in laboratory and field tests, and its utility is illustrated in field applications related to soil-gas formation, lake/atmosphere gas exchange, and seafloor gas emanations.

Kinetic Investigation of Homogeneous H(2)-D(2) Equilibration Catalyzed by Pt-Au Cluster Compounds. Characterization of the Cluster [(H)Pt(AuPPh(3))(9)](NO(3))(2).

PubMed

Rubinstein, Leon I.; Pignolet, Louis H.

1996-11-06

The new Pt-Au hydrido cluster compound [(H)Pt(AuPPh(3))(9)](NO(3))(2) (3) has been synthesized and characterized by NMR, FABMS, and single-crystal X-ray diffraction [triclinic, P&onemacr;, a = 17.0452(1) Å, b = 17.4045(2) Å, c = 55.2353(1) Å, alpha = 89.891(1) degrees, beta = 85.287(1) degrees, gamma = 75.173(1) degrees, V = 15784.0(2) Å(3), Z = 4 (two molecules in asymmetric unit), residual R = 0.089 for 45 929 observed reflections and 3367 variables, Mo Kalpha radiation]. The Pt(AuP)(9) core geometry is a distorted icosahedron with three vertices vacant. The Pt-Au, Au-Au, and Au-P distances are within the normal ranges observed in other Pt-Au clusters. This cluster is a catalyst for H(2)-D(2) equilibration in homogeneous solution phase and has been used in a general mechanistic study of this reaction catalyzed by Pt-Au clusters. We previously proposed that a key step in the mechanism for catalytic H(2)-D(2) equilibration is the dissociation of a PPh(3) ligand to give a cluster with an open Au site for bonding of H(2) or D(2). This was based on qualitative observations that PPh(3) inhibited the rate of HD production with [Pt(AuPPh(3))(8)](NO(3))(2) (1) as catalyst. In order to test this hypothesis, phosphine inhibition (on the rate of HD production) and phosphine ligand exchange kinetic experiments were carried out with [(H)(PPh(3))Pt(AuPPh(3))(7)](NO(3))(2) (2) and 3. In this paper we show that the rate constant for phosphine dissociation determined from the PPh(3) inhibition rate study of H(2)-D(2) equilibration with cluster 2 is nearly identical to the rate constant for dissociative phosphine ligand exchange. The slower rate for H(2)-D(2) equilibration observed with 3 compared with 2 (5.5 x 10(-3) vs 7.7 x 10(-2) turnover s(-1)) is explained by its smaller rate constant for phosphine dissociation (2.8 x 10(-5) vs 2.9 x 10(-4) s(-1)). The fact that clusters 2 and 3 show similar kinetic behaviors suggests that the PPh(3) dissociation step in the catalytic H(2)-D(2) equilibration is general for 18-electron hydrido Pt-AuPPh(3) clusters.

42 CFR Appendix - Tables to Subpart L of Part 84

Code of Federal Regulations, 2010 CFR

2010-10-01

... respiratory protection against more than one gas of a type, as for use in chlorine and sulfur dioxide, the... Ammonia Equilibrated NH3 1000 32 4 50 50 Chlorine As received Cl2 500 64 3 5 35 Chlorine Equilibrated Cl2... Sulfur dioxide As received SO2 500 64 3 5 30 Sulfur dioxide Equilibrated SO2 500 32 4 5 30 1 Minimum life...

Electron-ion temperature equilibration in warm dense tantalum

DOE PAGES

Doppner, T; LePape, S.; Ma, T.; ...

2014-11-05

We present measurements of electron-ion temperature equilibration in proton-heated tantalum, under warm dense matter conditions. Our results agree with theoretical predictions for metals calculated using input data from ab initio simulations. Furthermore, the fast relaxation observed in the experiment contrasts with much longer equilibration times found in proton heated carbon, indicating that the energy flow pathways in warm dense matter are far from being fully understood.

Effect of increasing equilibration time of diluted bull semen up to 72 h prior to freezing on sperm quality parameters and calving rate following artificial insemination.

PubMed

Murphy, E M; Eivers, B; O'Meara, C M; Lonergan, P; Fair, S

2018-03-01

An equilibration period of approximately 3-4 h prior to semen cryopreservation is standard practice for maintaining membrane integrity and motility of bull sperm. However, a number of studies indicate that an overnight equilibration period prior to freezing results in improved post-thaw semen quality thus optimising pregnancy rates. The aim of this study was to assess the effect of increasing the equilibration time of bull semen up to 72 h before freezing on sperm quality parameters and calving rate (CR) following artificial insemination (AI) with frozen-thawed semen. The effect of holding semen at 4 °C for 6, 24, 48 or 72 h post dilution before freezing on subsequent post-thaw total and progressive motility (Experiment 1) and field fertility (n = 1640 inseminations, Experiment 2) of frozen-thawed semen was assessed. Equilibration time did not affect post-thaw total and progressive motility (P > 0.05). In addition, there was no effect (P > 0.05) of equilibration time on field fertility with a CR of 53.3, 50.5, 51.3 and 47.3 for the 6, 24, 48 and 72 h treatments, respectively. In conclusion, increasing the equilibration time of diluted bull semen from 6 to 72 h had no significant effect on CR, within the expected range of fertility outcomes, thus providing semen processing centres with flexibility in the time which semen can be held prior to freezing. Copyright © 2017 Elsevier Inc. All rights reserved.

Equilibrating high-molecular-weight symmetric and miscible polymer blends with hierarchical back-mapping.

PubMed

Ohkuma, Takahiro; Kremer, Kurt; Daoulas, Kostas

2018-05-02

Understanding properties of polymer alloys with computer simulations frequently requires equilibration of samples comprised of microscopically described long molecules. We present the extension of an efficient hierarchical backmapping strategy, initially developed for homopolymer melts, to equilibrate high-molecular-weight binary blends. These mixtures present significant interest for practical applications and fundamental polymer physics. In our approach, the blend is coarse-grained into models representing polymers as chains of soft blobs. Each blob stands for a subchain with N b microscopic monomers. A hierarchy of blob-based models with different resolution is obtained by varying N b . First the model with the largest N b is used to obtain an equilibrated blend. This configuration is sequentially fine-grained, reinserting at each step the degrees of freedom of the next in the hierarchy blob-based model. Once the blob-based description is sufficiently detailed, the microscopic monomers are reinserted. The hard excluded volume is recovered through a push-off procedure and the sample is re-equilibrated with molecular dynamics (MD), requiring relaxation on the order of the entanglement time. For the initial method development we focus on miscible blends described on microscopic level through a generic bead-spring model, which reproduces hard excluded volume, strong covalent bonds, and realistic liquid density. The blended homopolymers are symmetric with respect to molecular architecture and liquid structure. To parameterize the blob-based models and validate equilibration of backmapped samples, we obtain reference data from independent hybrid simulations combining MD and identity exchange Monte Carlo moves, taking advantage of the symmetry of the blends. The potential of the backmapping strategy is demonstrated by equilibrating blend samples with different degree of miscibility, containing 500 chains with 1000 monomers each. Equilibration is verified by comparing chain conformations and liquid structure in backmapped blends with the reference data. Possible directions for further methodological developments are discussed.

Equilibrating high-molecular-weight symmetric and miscible polymer blends with hierarchical back-mapping

NASA Astrophysics Data System (ADS)

Ohkuma, Takahiro; Kremer, Kurt; Daoulas, Kostas

2018-05-01

Understanding properties of polymer alloys with computer simulations frequently requires equilibration of samples comprised of microscopically described long molecules. We present the extension of an efficient hierarchical backmapping strategy, initially developed for homopolymer melts, to equilibrate high-molecular-weight binary blends. These mixtures present significant interest for practical applications and fundamental polymer physics. In our approach, the blend is coarse-grained into models representing polymers as chains of soft blobs. Each blob stands for a subchain with N b microscopic monomers. A hierarchy of blob-based models with different resolution is obtained by varying N b. First the model with the largest N b is used to obtain an equilibrated blend. This configuration is sequentially fine-grained, reinserting at each step the degrees of freedom of the next in the hierarchy blob-based model. Once the blob-based description is sufficiently detailed, the microscopic monomers are reinserted. The hard excluded volume is recovered through a push-off procedure and the sample is re-equilibrated with molecular dynamics (MD), requiring relaxation on the order of the entanglement time. For the initial method development we focus on miscible blends described on microscopic level through a generic bead-spring model, which reproduces hard excluded volume, strong covalent bonds, and realistic liquid density. The blended homopolymers are symmetric with respect to molecular architecture and liquid structure. To parameterize the blob-based models and validate equilibration of backmapped samples, we obtain reference data from independent hybrid simulations combining MD and identity exchange Monte Carlo moves, taking advantage of the symmetry of the blends. The potential of the backmapping strategy is demonstrated by equilibrating blend samples with different degree of miscibility, containing 500 chains with 1000 monomers each. Equilibration is verified by comparing chain conformations and liquid structure in backmapped blends with the reference data. Possible directions for further methodological developments are discussed.

NICMOS Filter Wheel Test

NASA Astrophysics Data System (ADS)

Malhotra, Sangeeta

2003-07-01

This is an engineering test to verify the aliveness, functionality, operability, and electro-mechanical calibration of the NICMOS filter wheel motors and assembly after NCS restart in August 2003. This test has been designed to obviate concerns over possible deformation or breakage of the fitter wheel "soda-straw" shafts due to excess rotational drag torque and/or bending moments which may be imparted due to changes in the dewar metrology from warm-up/cool-down. This test should be executed after the NCS {and filter wheel housing} has reached and approximately equilibrated to its nominal Cycle 11 operating temperature.

CoMFA and CoMSIA 3D-QSAR studies on S(6)-(4-nitrobenzyl)mercaptopurine riboside (NBMPR) analogs as inhibitors of human equilibrative nucleoside transporter 1 (hENT1).

PubMed

Gupte, Amol; Buolamwini, John K

2009-01-15

3D-QSAR (CoMFA and CoMSIA) studies were performed on human equlibrative nucleoside transporter (hENT1) inhibitors displaying K(i) values ranging from 10,000 to 0.7nM. Both CoMFA and CoMSIA analysis gave reliable models with q2 values >0.50 and r2 values >0.92. The models have been validated for their stability and robustness using group validation and bootstrapping techniques and for their predictive abilities using an external test set of nine compounds. The high predictive r2 values of the test set (0.72 for CoMFA model and 0.74 for CoMSIA model) reveals that the models can prove to be a useful tool for activity prediction of newly designed nucleoside transporter inhibitors. The CoMFA and CoMSIA contour maps identify features important for exhibiting good binding affinities at the transporter, and can thus serve as a useful guide for the design of potential equilibrative nucleoside transporter inhibitors.

CO2 adhesion on hydrated mineral surfaces.

PubMed

Wang, Shibo; Tao, Zhiyuan; Persily, Sara M; Clarens, Andres F

2013-10-15

Hydrated mineral surfaces in the environment are generally hydrophilic but in certain cases can strongly adhere CO2, which is largely nonpolar. This adhesion can significantly alter the wettability characteristics of the mineral surface and consequently influence capillary/residual trapping and other multiphase flow processes in porous media. Here, the conditions influencing adhesion between CO2 and homogeneous mineral surfaces were studied using static pendant contact angle measurements and captive advancing/receding tests. The prevalence of adhesion was sensitive to both surface roughness and aqueous chemistry. Adhesion was most widely observed on phlogopite mica, silica, and calcite surfaces with roughness on the order of ~10 nm. The incidence of adhesion increased with ionic strength and CO2 partial pressure. Adhesion was very rarely observed on surfaces equilibrated with brines containing strong acid or base. In advancing/receding contact angle measurements, adhesion could increase the contact angle by a factor of 3. These results support an emerging understanding of adhesion of, nonpolar nonaqueous phase fluids on mineral surfaces influenced by the properties of the electrical double layer in the aqueous phase film and surface functional groups between the mineral and CO2.

XANES and Mg isotopic analyses of spinels in Ca-Al-rich inclusions: Evidence for formation under oxidizing conditions

NASA Astrophysics Data System (ADS)

Paque, J. M.; Sutton, S. R.; Simon, S. B.; Beckett, J. R.; Burnett, D. S.; Grossman, L.; Yurimoto, H.; Itoh, S.; Connolly, H. C.

2013-10-01

Ti valence measurements in MgAl2O4 spinel from calcium-aluminum-rich inclusions (CAIs) by X-ray absorption near-edge structure (XANES) spectroscopy show that many spinels have predominantly tetravalent Ti, regardless of host phases. The average spinel in Allende type B1 inclusion TS34 has 87% Ti+4. Most spinels in fluffy type A (FTA) inclusions also have high Ti valence. In contrast, the rims of some spinels in TS34 and spinel grain cores in two Vigarano type B inclusions have larger amounts of trivalent titanium. Spinels from TS34 have approximately equal amounts of divalent and trivalent vanadium. Based on experiments conducted on CAI-like compositions over a range of redox conditions, both clinopyroxene and spinel should be Ti+3-rich if they equilibrated with CAI liquids under near-solar oxygen fugacities. In igneous inclusions, the seeming paradox of high-valence spinels coexisting with low-valence clinopyroxene can be explained either by transient oxidizing conditions accompanying low-pressure evaporation or by equilibration of spinel with relict Ti+4-rich phases (e.g., perovskite) prior to or during melting. Ion probe analyses of large spinel grains in TS34 show that they are enriched in heavy Mg, with an average Δ25Mg of 4.25 ± 0.028‰, consistent with formation of the spinel from an evaporating liquid. Δ25Mg shows small, but significant, variation, both within individual spinels and between spinel and adjacent melilite hosts. The Δ25Mg data are most simply explained by the low-pressure evaporation model, but this model has difficulty explaining the high Ti+4 concentrations in spinel.

Statistical Constraints from Siderophile Elements on Earth's Accretion, Differentiation, and Initial Core Stratification

NASA Astrophysics Data System (ADS)

O'Rourke, J. G.; Stevenson, D. J.

2015-12-01

Abundances of siderophile elements in the primitive mantle constrain the conditions of Earth's core/mantle differentiation. Core growth occurred as Earth accreted from collisions between planetesimals and larger embryos of unknown original provenance, so geochemistry is directly related to the overall dynamics of Solar System formation. Recent studies claim that only certain conditions of equilibration (pressure, temperature, and oxygen fugacity) during core formation can reproduce the available data. Typical analyses, however, only consider the effects of varying a few out of tens of free parameters in continuous core formation models. Here we describe the Markov chain Monte Carlo method, which simultaneously incorporates the large uncertainties on Earth's composition and the parameterizations that describe elemental partitioning between metal and silicate. This Bayesian technique is vastly more computationally efficient than a simple grid search and is well suited to models of planetary accretion that involve a plethora of variables. In contrast to previous work, we find that analyses of siderophile elements alone cannot yield a unique scenario for Earth's accretion. Our models predict a wide range of possible light element contents for the core, encompassing all combinations permitted by seismology and mineral physics. Specifically, we are agnostic between silicon and oxygen as the dominant light element, and the addition of carbon or sulfur is also permissible but not well constrained. Redox conditions may have remained roughly constant during Earth's accretion or relatively oxygen-rich material could have been incorporated before reduced embryos. Pressures and temperatures of equilibration, likewise, may only increase slowly throughout accretion. Therefore, we do not necessarily expect a thick (>500 km), compositionally stratified layer that is stable against convection to develop at the top of the core of Earth (or, by analogy, Venus). A thinner stable layer might inhibit the initialization of the dynamo.

Fluid pressure and fault strength: insights from load-controlled experiments on carbonate-bearing rocks

NASA Astrophysics Data System (ADS)

Spagnuolo, E.; Violay, M.; Nielsen, S. B.; Di Toro, G.

2013-12-01

Fluid pressure Pf has been indicated as a major factor controlling natural (e.g., L'Aquila, Italy, 2009 Mw 6.3) and induced seismicity (e.g., Wilzetta, Oklahoma, 2011 Mw 5.7). The Terzaghi's principle states that the effective normal stress σeff= σn (1- α Pf ), with α the Biot coefficient and σn the normal stress, is reduced in proportion to Pf. A value of α=1 is often used by default; however, within a complex fault core of inhomogeneous permeability, α may vary in a yet poorly understood way. To shed light on this problem, we conducted experiments on carbonate-bearing rock samples (Carrara marble) in room humidity conditions and in the presence of pore fluids (drained conditions), where a pre-cut fault is loaded by shear stress τ in a rotary apparatus (SHIVA) under constant σn=15 MPa. Two types of tests were performed with fluids: (1) the fluid pressure was kept constant at Pf=5 MPa (close to hydrostatic conditions at a depth of 0.5 km) and the fault was driven to failure instability by gradually increasing τ; (2) the fluid pressure was kept at Pf=5 MPa and τ was increased until close to instability (τ = 7 MPa): at this point Pf was raised of 0.5 MPa every 10 s up to Pf =10 MPa to induce a main (failure) instability. Assuming α=1 and an effective peak strength (τp)eff=μp σeff at failure, the experiments reveal that: 1) (τp)eff is sensitive to the shear loading rate: fast loading rates (0.5 MPa every 20 s) induce higher peak shear-stress values than slow loading rates (0.5 MPa every 40 s). Such effect is not observed (minor or inexistent) in the absence of pore fluids. 2) Under fast loading rates the (τp)eff may surpass that measured in the absence of pore fluids under identical effective normal stress σeff. 3) An increase of Pf does not necessarily induce the main instability (within the time intervals studied here, i.e. up to ~10 s) even if the effective strength threshold is largely surpassed (e.g., (τp)eff=1.3 μp σeff). We interpret these results in terms of limited permeability of the fault slip zone which reduces α. Indeed result (3) may indicate that a Pf increase did not rapidly penetrate the slip zone because a seal (thin layer of wet ultrafine calcite gouge) formed during the slip preceding the main instability. On the other hand, shearing of the slip zone probably induces dilation (not measured because below resolution) in the slip zone and results in a decrease in pore pressure. Again, due to limited permeability, the drop in pore pressure within the slip zone does not have time to re-equilibrate with the imposed Pf, provided that the hold time is short (20 s) with respect to the diffusion time, but it may re-equilibrate under longer hold times (40 s). As a consequence the Biot coefficient depends on the time interval of observation, with α~0 at short time periods and α~1 at long time periods. This yields an approximate hydraulic diffusivity κ~10-8 m2 s-1 using κ=l2/td with the half length of the contact surface l=5 mm and td=30 s. Such diffusivity is compatible, for example, with a low porosity shale.

A (1)H-NMR study on the effect of high pressures on beta-lactoglobulin.

PubMed

Belloque, J; López-Fandiño, R; Smith, G M

2000-09-01

1H NMR was used to study the effect of high pressure on changes in the structure of beta-lactoglobulin (beta-Lg), particularly the strongly bonded regions, the "core". beta-Lg was exposed to pressures ranging from 100 to 400 MPa at neutral pH. After depressurization and acidification to pH 2.0, (1)H NMR spectra were taken. Pressure-induced unfolding was studied by deuterium exchange. Refolding was also evaluated. Our results showed that the core was unaltered at 100 MPa but increased its conformational flexibility at >/=200 MPa. Even though the core was highly flexible at 400 MPa, its structure was found to be identical to the native structure after equilibration back to atmospheric pressure. It is suggested that pressure-induced aggregates are formed by beta-Lg molecules maintaining most of their structure, and the intermolecular -SS- bonds, formed by -SH/-SS- exchange reaction, are likely to involve C(66)-C(160) rather than C(106)-C(119). In addition, the beta-Lg variants A and B could be distinguished in a (1)H NMR spectrum from a solution made with the AB mixed variant, by the differences in chemical shifts of M(107) and C(106); structural implications are discussed. Under pressure, the core of beta-Lg A seemed to unfold faster than that of beta-LgB. The structural recovery of the core was full for both variants.

Determining pH at elevated pressure and temperature using in situ ¹³C NMR.

PubMed

Surface, J Andrew; Wang, Fei; Zhu, Yanzhe; Hayes, Sophia E; Giammar, Daniel E; Conradi, Mark S

2015-02-03

We have developed an approach for determining pH at elevated pressures and temperatures by using (13)C NMR measurements of inorganic carbon species together with a geochemical equilibrium model. The approach can determine in situ pH with precision better than 0.1 pH units at pressures, temperatures, and ionic strengths typical of geologic carbon sequestration systems. A custom-built high pressure NMR probe was used to collect (13)C NMR spectra of (13)C-labeled CO2 reactions with NaOH solutions and Mg(OH)2 suspensions at pressures up to 107 bar and temperatures of 80 °C. The quantitative nature of NMR spectroscopy allows the concentration ratio [CO2]/[HCO3(-)] to be experimentally determined. This ratio is then used with equilibrium constants calculated for the specific pressure and temperature conditions and appropriate activity coefficients for the solutes to calculate the in situ pH. The experimentally determined [CO2]/[HCO3(-)] ratios agree well with the predicted values for experiments performed with three different concentrations of NaOH and equilibration with multiple pressures of CO2. The approach was then applied to experiments with Mg(OH)2 slurries in which the change in pH could track the dissolution of CO2 into solution, rapid initial Mg(OH)2 dissolution, and onset of magnesium carbonate precipitation.

Mineralization of Basalts in the CO 2-H 2O-H 2S System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaef, Herbert T.; McGrail, B. Peter; Owen, Antionette T.

2013-05-10

Basalt samples representing five different formations were immersed in water equilibrated with supercritical carbon dioxide containing 1% hydrogen sulfide (H2S) at reservoir conditions (100 bar, 90°C) for up to 3.5 years. Surface coatings in the form of pyrite and metal cation substituted carbonates were identified as reaction products associated with all five basalts. In some cases, high pressure tests contained excess H2S, which produced the most corroded basalts and largest amount of secondary products. In comparison, tests containing limited amounts of H2S appeared least reacted with significantly less concentrations of reaction products. In all cases, pyrite appeared to precede carbonation,more » and in some instances, was observed in the absence of carbonation such as in cracks, fractures, and within the porous glassy mesostasis. Armoring reactions from pyrite surface coatings observed in earlier shorter duration tests were found to be temporary with carbonate mineralization observed with all the basalts tested in these long duration experiments. Geochemical simulations conducted with the geochemical code EQ3/6 accurately predicted early pyrite precipitation followed by formation of carbonates. Reactivity with H2S was correlated with measured Fe(II)/Fe(III) ratios in the basalts with more facile pyrite formation occurring with basalts containing more Fe(III) phases. These experimental and modeling results confirm potential for long term sequestration of acid gas mixtures in continental flood basalt formations.« less

The rate of equilibration of viscous aerosol particles

NASA Astrophysics Data System (ADS)

O'Meara, Simon; Topping, David O.; McFiggans, Gordon

2016-04-01

The proximity of atmospheric aerosol particles to equilibrium with their surrounding condensable vapours can substantially impact their transformations, fate and impacts and is the subject of vibrant research activity. In this study we first compare equilibration timescales estimated by three different models for diffusion through aerosol particles to assess any sensitivity to choice of model framework. Equilibration times for diffusion coefficients with varying dependencies on composition are compared for the first time. We show that even under large changes in the saturation ratio of a semi-volatile component (es) of 1-90 % predicted equilibration timescales are in agreement, including when diffusion coefficients vary with composition. For condensing water and a diffusion coefficient dependent on composition, a plasticising effect is observed, leading to a decreased estimated equilibration time with increasing final es. Above 60 % final es maximum equilibration times of around 1 s are estimated for comparatively large particles (10 µm) containing a relatively low diffusivity component (1 × 10-25 m2 s-1 in pure form). This, as well as other results here, questions whether particle-phase diffusion through water-soluble particles can limit hygroscopic growth in the ambient atmosphere. In the second part of this study, we explore sensitivities associated with the use of particle radius measurements to infer diffusion coefficient dependencies on composition using a diffusion model. Given quantified similarities between models used in this study, our results confirm considerations that must be taken into account when designing such experiments. Although quantitative agreement of equilibration timescales between models is found, further work is necessary to determine their suitability for assessing atmospheric impacts, such as their inclusion in polydisperse aerosol simulations.

Fast equilibration protocol for million atom systems of highly entangled linear polyethylene chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sliozberg, Yelena R.; TKC Global, Inc., Aberdeen Proving Ground, Maryland 21005; Kröger, Martin

Equilibrated systems of entangled polymer melts cannot be produced using direct brute force equilibration due to the slow reptation dynamics exhibited by high molecular weight chains. Instead, these dense systems are produced using computational techniques such as Monte Carlo-Molecular Dynamics hybrid algorithms, though the use of soft potentials has also shown promise mainly for coarse-grained polymeric systems. Through the use of soft-potentials, the melt can be equilibrated via molecular dynamics at intermediate and long length scales prior to switching to a Lennard-Jones potential. We will outline two different equilibration protocols, which use various degrees of information to produce the startingmore » configurations. In one protocol, we use only the equilibrium bond angle, bond length, and target density during the construction of the simulation cell, where the information is obtained from available experimental data and extracted from the force field without performing any prior simulation. In the second protocol, we moreover utilize the equilibrium radial distribution function and dihedral angle distribution. This information can be obtained from experimental data or from a simulation of short unentangled chains. Both methods can be used to prepare equilibrated and highly entangled systems, but the second protocol is much more computationally efficient. These systems can be strictly monodisperse or optionally polydisperse depending on the starting chain distribution. Our protocols, which utilize a soft-core harmonic potential, will be applied for the first time to equilibrate a million particle system of polyethylene chains consisting of 1000 united atoms at various temperatures. Calculations of structural and entanglement properties demonstrate that this method can be used as an alternative towards the generation of entangled equilibrium structures.« less

Hydrogen bonds in concreto and in computro

NASA Astrophysics Data System (ADS)

Stouten, Pieter F. W.; Kroon, Jan

1988-07-01

Molecular dynamics simulations of liquid water and liquid methanol have been carried out. For both liquids an effective pair potential was used. The models were fitted to the heat of vaporization, pressure and various radial distribution functions resulting from diffraction experiments on liquids. In both simulations 216 molecules were put in a cubic periodical ☐. The system was loosely coupled to a temperature bath and to a pressure bath. Following an initial equilibration period relevant data were sampled during 15 ps. The distributions of oxygen—oxygen distances in hydrogen bonds obtained from the two simulations are essentially the same. The distribution obtained from crystal data is somewhat different: the maximum has about the same position, but the curve is much narrower, which can be expected merely from the fact that diffraction experiments only supply average atomic positions and hence average interatomic distances. When thermal motion is taken into account a closer likeness is observed.

Hydraulic fracture during epithelial stretching

NASA Astrophysics Data System (ADS)

Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier

2015-03-01

The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here, we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression manoeuvres. After pressure equilibration, cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics.

Hydraulic fracture during epithelial stretching

PubMed Central

Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier

2015-01-01

The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression maneuvers. After pressure equilibration cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics. PMID:25664452

Molecular dynamics studies of electron-ion temperature equilibration in hydrogen plasmas within the coupled-mode regime

DOE PAGES

Benedict, Lorin X.; Surh, Michael P.; Stanton, Liam G.; ...

2017-04-10

Here, we use classical molecular dynamics (MD) to study electron-ion temperature equilibration in two-component plasmas in regimes for which the presence of coupled collective modes has been predicted to substantively reduce the equilibration rate. Guided by previous kinetic theory work, we examine hydrogen plasmas at a density of n = 10 26cm –3, T i = 10 5K, and 10 7 K < Te < 10 9K. The nonequilibrium classical MD simulations are performed with interparticle interactions modeled by quantum statistical potentials (QSPs). Our MD results indicate (i) a large effect from time-varying potential energy, which we quantify by appealingmore » to an adiabatic two-temperature equation of state, and (ii) a notable deviation in the energy equilibration rate when compared to calculations from classical Lenard-Balescu theory including the QSPs. In particular, it is shown that the energy equilibration rates from MD are more similar to those of the theory when coupled modes are neglected. We suggest possible reasons for this surprising result and propose directions of further research along these lines.« less

Biophase equilibration times.

PubMed

Veng-Pedersen, P; Mandema, J W; Danhof, M

1991-09-01

Various methods for describing how quickly a drug equilibrates at the biophase are proposed. The biophase equilibration time (BET) is the time it takes the biophase drug level to reach a given percentage (p) of its predicted steady state in a drug administration that leads to a steady-state condition. The time to reach biophase equilibrium may be defined as the BET value for p = 95, and the 50% biophase equilibration time is obtained when p = 50. Biophase equilibration profiles (BEPs), obtained by plotting p versus BET, give a dynamic representation of the approach to equilibrium and may serve as an indicator of the rate of drug delivery to the biophase. A pharmacodynamic system analysis method is proposed to determine BETs and BEPs from the biophase conduction function. The approach is demonstrated using pharmacodynamic data from the CNS effect of amobarbital evaluated by an aperiodic analysis of EEG recordings. The relevance of the BET and/or BEP principles in optimal computer-controlled drug infusion, drug design, and evaluation of targeted drug delivery is discussed. Both vascular and extravascular drug administrations are considered in the analysis.

High-resolution measurement of DMS and volatile organic compounds dissolved in seawater using equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS)

NASA Astrophysics Data System (ADS)

Kameyama, S.; Tanimoto, H.; Inomata, S.; Tsunogai, U.; Ooki, A.; Yokouchi, Y.; Takeda, S.; Obata, H.; Tsuda, A.; Uematsu, M.

2010-12-01

We developed an equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) for high-resolution measurement of multiple volatile organic compounds (VOCs) dissolved in seawater. The equilibration of six VOC species (dimethyl sulfide (DMS), isoprene, propene, acetone, acetaldehyde, and methanol) between seawater and carrier gas, and the response time of the system were evaluated in the laboratory. While isoprene and propene are not in equilibrium associated with slow response time (≈ 15 min) due to low solubility, other species achieve complete equilibrium with overall response time within 2 min under the condition without water droplets on the inner wall of the headspace of the equilibrator. The EI-PTR-MS instrument was deployed during a cruise in the western North Pacific. For DMS and isoprene, comparison of EI-PTR-MS with a membrane tube equilibrator-gas chromatography/mass spectrometry was made, showing generally good agreement. EI-PTR-MS captured temporal variations of dissolved VOCs including small-scale variability, demonstrating the performance of EI-PTR-MS technique for continuous measurement of multiple VOCs in seawater.

Pore Fluid Pressure Development in Compacting Fault Gouge in Theory, Experiments, and Nature

NASA Astrophysics Data System (ADS)

Faulkner, D. R.; Sanchez-Roa, C.; Boulton, C.; den Hartog, S. A. M.

2018-01-01

The strength of fault zones is strongly dependent on pore fluid pressures within them. Moreover, transient changes in pore fluid pressure can lead to a variety of slip behavior from creep to unstable slip manifested as earthquakes or slow slip events. The frictional properties of low-permeability fault gouge in nature and experiment can be affected by pore fluid pressure development through compaction within the gouge layer, even when the boundaries are drained. Here the conditions under which significant pore fluid pressures develop are analyzed analytically, numerically, and experimentally. Friction experiments on low-permeability fault gouge at different sliding velocities show progressive weakening as slip rate is increased, indicating that faster experiments are incapable of draining the pore fluid pressure produced by compaction. Experiments are used to constrain the evolution of the permeability and pore volume needed for numerical modeling of pore fluid pressure build up. The numerical results are in good agreement with the experiments, indicating that the principal physical processes have been considered. The model is used to analyze the effect of pore fluid pressure transients on the determination of the frictional properties, illustrating that intrinsic velocity-strengthening behavior can appear velocity weakening if pore fluid pressure is not given sufficient time to equilibrate. The results illustrate that care must be taken when measuring experimentally the frictional characteristics of low-permeability fault gouge. The contribution of compaction-induced pore fluid pressurization leading to weakening of natural faults is considered. Cyclic pressurization of pore fluid within fault gouge during successive earthquakes on larger faults may reset porosity and hence the capacity for compaction weakening.

An internally consistent pressure calibration of geobarometers applicable to the Earth’s upper mantle using in situ XRD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beyer, Christopher; Rosenthal, Anja; Myhill, Robert

We have performed an experimental cross calibration of a suite of mineral equilibria within mantle rock bulk compositions that are commonly used in geobarometry to determine the equilibration depths of upper mantle assemblages. Multiple barometers were compared simultaneously in experimental runs, where the pressure was determined using in-situ measurements of the unit cell volumes of MgO, NaCl, Re and h-BN between 3.6 and 10.4 GPa, and 1250 and 1500 °C. The experiments were performed in a large volume press (LVPs) in combination with synchrotron X-ray diffraction. Noble metal capsules drilled with multiple sample chambers were loaded with a range ofmore » bulk compositions representative of peridotite, eclogite and pyroxenite lithologies. By this approach, we simultaneously calibrated the geobarometers applicable to different mantle lithologies under identical and well determined pressure and temperature conditions. We identified discrepancies between the calculated and experimental pressures for which we propose simple linear or constant correction factors to some of the previously published barometric equations. As a result, we establish internally-consistent cross-calibrations for a number of garnet-orthopyroxene, garnet-clinopyroxene, Ca-Tschermaks-in-clinopyroxene and majorite geobarometers.« less

Effect of biofilm dryness on the transfer of Listeria monocytogenes biofilms grown on stainless steel to bologna and hard salami.

PubMed

Rodríguez, Andrés; Autio, Wesley R; McLandsborough, Lynne A

2007-11-01

Listeria monocytogenes continues to be a major cause of class I food recalls in the United States. Very little is known about its transfer and cross-contamination in processing scenarios. The objective of this study was to evaluate the effect of hydration level on L. monocytogenes biofilms grown on stainless steel and its effect on the biofilm transfer to foods. Biofilms were grown on stainless steel in diluted tryptic soy broth 1:20 for 48 h at 32 degrees C. After this, biofilms were equilibrated over saturated salt solutions at 20 degrees C for 24 h (94, 75, 58, and 33% relative humidity; % RH) prior to transferring. Transfer experiments were conducted from inoculated stainless steel to bologna and hard salami at a constant pressure (45 kPa) and time (30 s) with a universal testing machine. The experiment was designed with a factorial design 4 x 2 (biofilms equilibrated at 4% RH and two foods) and duplicated every day, and the whole experiment was repeated nine times. The results were analyzed with an analysis of variance by SAS Statistical Analysis Software. Our results showed that more bacteria were transferred to bologna (mean efficiency of transfer [EOT] = 3.0) than to hard salami (mean EOT = 0.35, P < 0.01). As biofilms became drier, the transfer of Listeria from stainless steel to both foods increased (P < 0.05). The EOT increased from 2 to 3.8 and from 0.2 to 0.51 upon transfer when drying the biofilm for bologna and hard salami, respectively. This study may be an indication that as biofilms were dried, the cell-cell and cell-surface interactions became weaker, and bacterial transfer increased. This phenomenon was enhanced in foods containing higher water activity levels. We hypothesize that this increased in transfer was due to the presence of capillary forces in the food.

Core layering

NASA Astrophysics Data System (ADS)

Jacobson, S. A.; Rubie, D. C.; Hernlund, J. W.; Morbidelli, A.

2015-12-01

We have created a planetary accretion and differentiation model that self-consistently builds and evolves Earth's core. From this model, we show that the core grows stably stratified as the result of rising metal-silicate equilibration temperatures and pressures, which increases the concentrations of light element impurities into each newer core addition. This stable stratification would naturally resist convection and frustrate the onset of a geodynamo, however, late giant impacts could mechanically mix the distinct accreted core layers creating large homogenous regions. Within these regions, a geodynamo may operate. From this model, we interpret the difference between the planetary magnetic fields of Earth and Venus as a difference in giant impact histories. Our planetary accretion model is a numerical N-body integration of the Grand Tack scenario [1]—the most successful terrestrial planet formation model to date [2,3]. Then, we take the accretion histories of Earth-like and Venus-like planets from this model and post-process the growth of each terrestrial planet according to a well-tested planetary differentiation model [4,5]. This model fits Earth's mantle by modifying the oxygen content of the pre-cursor planetesimals and embryos as well as the conditions of metal-silicate equilibration. Other non-volatile major, minor and trace elements included in the model are assumed to be in CI chondrite proportions. The results from this model across many simulated terrestrial planet growth histories are robust. If the kinetic energy delivered by larger impacts is neglected, the core of each planet grows with a strong stable stratification that would significantly impede convection. However, if giant impact mixing is very efficient or if the impact history delivers large impacts late, than the stable stratification can be removed. [1] Walsh et al. Nature 475 (2011) [2] O'Brien et al. Icarus 223 (2014) [3] Jacobson & Morbidelli PTRSA 372 (2014) [4] Rubie et al. EPSL 301 (2011) [5] Rubie et al. Icarus 248 (2015)

Intrauterine temperature during intrapartum amnioinfusion: a prospective observational study.

PubMed

Tomlinson, T M; Schaecher, C; Sadovsky, Y; Gross, G

2012-07-01

To determine the influence of routine intrapartum amnioinfusion (AI) on intrauterine temperature. Prospective observational study. Maternity unit, Barnes Jewish Hospital, St Louis, MO, USA. Forty women with singleton gestations and an indication for intrapartum intrauterine pressure catheter placement. Using a temperature probe, we digitally recorded intrauterine temperature every 10 minutes during labour. Amnioinfusion was administered according to a standard protocol using saline equilibrated to the ambient temperature. Mean intrauterine temperature during labour. Participants were monitored for a mean of 280 minutes (range 20-820). A total of 164 intrauterine temperature readings in the AI cohort were compared with 797 control measurements. When compared with controls, we observed a lower intrauterine temperature in the AI cohort (36.4 versus 37.4°C, P<0.01). More measurements in the AI cohort were recorded in the presence of intrapartum fever (40% versus 30%). A subgroup analysis of measurements recorded in afebrile parturients revealed an even greater effect of AI (1.5°C decrease, 37.3 versus 35.8°C, P<0.01). Routine intrapartum AI using saline equilibrated to a mean ambient temperature of 25.0°C reduces intrauterine temperature and may thereby affect fetal core temperature. © 2012 The Authors BJOG An International Journal of Obstetrics and Gynaecology © 2012 RCOG.

Neutral Gas Temperature Estimates in an Inductively Coupled CF4 Plasma by Fitting Diatomic Emission Spectra

NASA Technical Reports Server (NTRS)

Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, M.

2001-01-01

This work examines the accuracy of plasma neutral temperature estimates by fitting the rotational band envelope of different diatomic species in emission. Experiments are performed in an inductively coupled CF4 plasma generated in a Gaseous Electronics Conference reference cell. Visible and ultraviolet emission spectra are collected at a power of 300 W (approximately 0.7 W/cc) and pressure of 30 mtorr. The emission bands of several molecules (CF, CN, C2, CO, and SiF) are fit simultaneously for rotational and vibrational temperatures and compared. Four different rotational temperatures are obtained: 1250 K for CF and CN, 1600 K for CO, 1800 K for C2, and 2300 K for SiF. The vibrational temperatures obtained vary from 1750-5950 K, with the higher vibrational temperatures generally corresponding to the lower rotational temperatures. These results suggest that the different species have achieved different degrees of equilibration between the rotational and vibrational modes and may not be equilibrated with the translational temperatures. The different temperatures are also related to the likelihood that the species are produced by ion bombardment of the surface, with etch products like SiF, CO, and C2 having higher temperatures than species expected to have formed in the gas phase.

Reversed headspace analysis for characterization, identification, and analysis of solid and liquid matrices: Part I.

PubMed

Markelov, M; Bershevits, O

2006-03-01

This paper offers a methodology of an experimentally simple reversed headspace (RHS) analysis for measuring of matrix effects and their use for identification and characterization of condensed matrices such as pharmaceuticals, polymers, chromatographic packing, etc. applicable for both quality control monitoring and research and development investigation. In RHS methods, the matrix is spiked and equilibrated with a mixture of volatile chemicals containing various functional groups (molecular sensor array or MSA mixture). Headspace chromatograms of the same spikes of a sample and an empty vial are compared. Examination of basic headspace theory shows that matrix specific constants (M), rather than partition coefficients (K), can be calculated from the headspace chromatograms and M=(K-1)xbeta, where beta is a degree of matrix volume change during equilibration. Matrix specific constants can be plotted against any property of chemicals (polarity, dielectric constant, solubility parameter, vapor pressure, etc.) or just against a set of consecutive numbers, each representing a chemical in MSA. This plot is, in a sense, a molecular affinity spectrum (MAS) specific for a given matrix at a given temperature and is independent of an instrument. Changes in MAS that correspond to chemicals with a particular functional group give an insight to the type of differences between matrices and may quantitatively define them.

Energy demand of cardioplegically perfused human hearts.

PubMed

Preusse, C J; Winter, J; Schulte, H D; Bircks, W

1985-01-01

Human adult hearts with aortic valve disease (n = 20) and hypertrophic obstructive cardiomyopathy (n = 1) were perfused intraoperatively with cold histidine buffered Bretschneider solution. During a seven minute cardioplegic perfusion the temperature level, the electrolyte level, the resistance of the left (LCA) and right coronary artery (RCA), and myocardial O2 consumption were analysed. Equilibration of K+ was terminated shortly after the start of the perfusion while Na+ equilibration lasted for about 5 minutes. Resistance of RCA did not change significantly, but that of the LCA was diminished significantly (p less than 0.025) within the perfusion period indicating a delayed washout of calcium from the extracellular space. Myocardial O2 consumption was reduced from 2.71 ml/min (1. minute) to 1.51 ml/min (4. minute) to 0.93 ml/min (7. minute) although the temperature had reached a low level after 3 minutes. The difference between 4. to 7. minutes is significant (p less than 0.001). By our results it is concluded that in adult hearts high-volume cardioplegic perfusion at a flow rate of 1 ml/min X gm at a perfusion pressure of 40 to 50 mmHg should be performed for at least 6 to 7 minutes to achieve a sufficient intra-ischemic myocardial protection.

Exploding Pusher Targets for Electron-Ion Coupling Measurements

NASA Astrophysics Data System (ADS)

Whitley, Heather D.; Pino, Jesse; Schneider, Marilyn; Shepherd, Ronnie; Benedict, Lorin; Bauer, Joseph; Graziani, Frank; Garbett, Warren

2015-11-01

Over the past several years, we have conducted theoretical investigations of electron-ion coupling and electronic transport in plasmas. In the regime of weakly coupled plasmas, we have identified models that we believe describe the physics well, but experimental data is still needed to validate the models. We are currently designing spectroscopic experiments to study electron-ion equilibration and/or electron heat transport using exploding pusher (XP) targets for experiments at the National Ignition Facility. Two platforms are being investigated: an indirect drive XP (IDXP) with a plastic ablator and a polar-direct drive XP (PDXP) with a glass ablator. The fill gas for both designs is D2. We propose to use a higher-Z dopant, such as Ar, as a spectroscopic tracer for time-resolved electron and ion temperature measurements. We perform 1D simulations using the ARES hydrodynamic code, in order to produce the time-resolved plasma conditions, which are then post-processed with CRETIN to assess the feasibility of a spectroscopic measurement. We examine target performance with respect to variations in gas fill pressure, ablator thickness, atom fraction of the Ar dopant, and drive energy, and assess the sensitivity of the predicted spectra to variations in the models for electron-ion equilibration and thermal conductivity. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-675219.

Casein Micelle Dispersions under Osmotic Stress

PubMed Central

Bouchoux, Antoine; Cayemitte, Pierre-Emerson; Jardin, Julien; Gésan-Guiziou, Geneviève; Cabane, Bernard

2009-01-01

Abstract Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic pressure is dominated by the contribution from small residual peptides that are dissolved in the aqueous phase. ii), A transition range that starts when the casein micelles begin to interact through their κ-casein brushes and ends when the micelles are forced to get into contact with each other. At the end of this regime, the dispersions behave as coherent solids that do not fully redisperse when osmotic stress is released. iii), A concentrated regime in which compression removes water from within the micelles, and increases the fraction of micelles that are irreversibly linked to each other. In this regime the osmotic pressure profile is a power law of the residual free volume. It is well described by a simple model that considers the micelle to be made of dense regions separated by a continuous phase. The amount of water in the dense regions matches the usual hydration of proteins. PMID:19167314

Casein micelle dispersions under osmotic stress.

PubMed

Bouchoux, Antoine; Cayemitte, Pierre-Emerson; Jardin, Julien; Gésan-Guiziou, Geneviève; Cabane, Bernard

2009-01-01

Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic pressure is dominated by the contribution from small residual peptides that are dissolved in the aqueous phase. ii), A transition range that starts when the casein micelles begin to interact through their kappa-casein brushes and ends when the micelles are forced to get into contact with each other. At the end of this regime, the dispersions behave as coherent solids that do not fully redisperse when osmotic stress is released. iii), A concentrated regime in which compression removes water from within the micelles, and increases the fraction of micelles that are irreversibly linked to each other. In this regime the osmotic pressure profile is a power law of the residual free volume. It is well described by a simple model that considers the micelle to be made of dense regions separated by a continuous phase. The amount of water in the dense regions matches the usual hydration of proteins.

The ilmenite liquidus and depths of segregation for high-Ti picrite glasses

NASA Technical Reports Server (NTRS)

Hess, P. C.

1993-01-01

Lunar picrite glasses represent primitive and perhaps near primary liquids which have suffered only minor degrees of crystallization or near crustal modification. These glasses are multisaturated with olivine and orthopyroxene at pressures from 20-25 kb. I argue below that high TiO2 mare glasses were indeed equilibrated with orthopyroxene and were segregated from the lunar mantle at mean depths of 400-500 km. The glasses are typically modelled as products of relatively low degrees of melting of an hybridized source resulting from the overturn and mixing of the gravitationally unstable cumulate pile. But the models are neither unique nor, in some cases, correct.

21 CFR 201.327 - Over-the-counter sunscreen drug products; required labeling based on effectiveness testing.

Code of Federal Regulations, 2013 CFR

2013-04-01

... equilibrate for 15 minutes in the dark before the pre-irradiation described in paragraph (c) of this section. (3) Sunscreen product pre-irradiation. To account for lack of photostability, apply the sunscreen... simulator described in section 352.70(b) of this chapter. The irradiation dose should be 4 MEDs which is...

21 CFR 201.327 - Over-the-counter sunscreen drug products; required labeling based on effectiveness testing.

Code of Federal Regulations, 2012 CFR

2012-04-01

... equilibrate for 15 minutes in the dark before the pre-irradiation described in paragraph (c) of this section. (3) Sunscreen product pre-irradiation. To account for lack of photostability, apply the sunscreen... simulator described in section 352.70(b) of this chapter. The irradiation dose should be 4 MEDs which is...

21 CFR 201.327 - Over-the-counter sunscreen drug products; required labeling based on effectiveness testing.

Code of Federal Regulations, 2014 CFR

2014-04-01

... equilibrate for 15 minutes in the dark before the pre-irradiation described in paragraph (c) of this section. (3) Sunscreen product pre-irradiation. To account for lack of photostability, apply the sunscreen... simulator described in section 352.70(b) of this chapter. The irradiation dose should be 4 MEDs which is...

Development and Evaluation of an Online Air Quality Monitor (DIVEAIR2) for Diving Compressors

DTIC Science & Technology

2009-03-01

nonextreme levels. However, our experience with field testing has shown that the temperatures of work spaces commonly used for instrument setup and...so far. Nevertheless, one strategy for field use might be to allow the monitor to equilibrate to the ambient temperature near the compressor before...limit be subject to change, depending on experience with actual field testing. 4. Before any monitors are delivered to the Fleet for field use, we

Equilibrated moisture content of several carbon phenolics and their relationship to resin, fiber, and interface properties

NASA Technical Reports Server (NTRS)

Stokes, E. H.

1991-01-01

This study focuses on the relationship between relative humidity and the equilibrated moisture content of several variants of two distinctly different carbon phenolic composites. One of the materials gives a typical exponential relationship between RH and equilibrated moisture content while the second gives an inverse sigmoidal relationship with the largest increase in moisture between 45-60 percent relative humidity. The possible relationship between the shape of the curves and the nature of the material constituents is discussed.

Passive flux meter measurement of water and nutrient flux in saturated porous media: bench-scale laboratory tests.

PubMed

Cho, Jaehyun; Annable, Michael D; Jawitz, James W; Hatfield, Kirk

2007-01-01

The passive nutrient flux meter (PNFM) is introduced for simultaneous measurement of both water and nutrient flux through saturated porous media. The PNFM comprises a porous sorbent pre-equilibrated with a suite of alcohol tracers, which have different partitioning coefficients. Water flux was estimated based on the loss of loaded resident tracers during deployment, while nutrient flux was quantified based on the nutrient solute mass captured on the sorbent. An anionic resin, Lewatit 6328 A, was used as a permeable sorbent and phosphate (PO4(3-)) was the nutrient studied. The phosphate sorption capacity of the resin was measured in batch equilibration tests as 56 mg PO4(3-) g(-1), which was determined to be adequate capacity to retain PO4(3-) loads intercepted over typical PNFM deployment periods in most natural systems. The PNFM design was validated with bench-scale laboratory tests for a range of 9.8 to 28.3 cm d(-1) Darcy velocities and 6 to 43 h deployment durations. Nutrient and water fluxes measured by the PNFM averaged within 6 and 12% of the applied values, respectively, indicating that the PNFM shows promise as a tool for simultaneous measurement of water and nutrient fluxes.

Investigation of preparation techniques for δ2H analysis of keratin materials and a proposed analytical protocol

USGS Publications Warehouse

Qi, H.; Coplen, T.B.

2011-01-01

Accurate hydrogen isotopic measurements of keratin materials have been a challenge due to exchangeable hydrogen in the sample matrix and the paucity of appropriate isotopic reference materials for calibration. We found that the most reproducible δ2HVSMOW-SLAP and mole fraction of exchangeable hydrogen, x(H)ex, of keratin materials were measured with equilibration at ambient temperature using two desiccators and two different equilibration waters with two sets of the keratin materials for 6 days. Following equilibration, drying the keratin materials in a vacuum oven for 4 days at 60 °C was most critical. The δ2H analysis protocol also includes interspersing isotopic reference waters in silver tubes among samples in the carousel of a thermal conversion elemental analyzer (TC/EA) reduction unit. Using this analytical protocol, δ2HVSMOW-SLAP values of the non-exchangeable fractions of USGS42 and USGS43 human-hair isotopic reference materials were determined to be –78.5 ± 2.3 ‰ and –50.3 ± 2.8 ‰, respectively. The measured x(H)ex values of keratin materials analyzed with steam equilibration and N2 drying were substantially higher than those previously published, and dry N2 purging was unable to remove absorbed moisture completely, even with overnight purging. The δ2H values of keratin materials measured with steam equilibration were about 10 ‰ lower than values determined with equilibration in desiccators at ambient temperatures when on-line evacuation was used to dry samples. With steam equilibrations the x(H)ex of commercial keratin powder was as high as 28 %. Using human-hair isotopic reference materials to calibrate other keratin materials, such as hoof or horn, can introduce bias in δ2H measurements because the amount of absorbed water and the x(H)ex values may differ from those of unknown samples. Correct δ2HVSMOW-SLAP values of the non-exchangeable fractions of unknown human-hair samples can be determined with atmospheric moisture equilibration by normalizing with USGS42 and USGS43 human-hair reference materials when all materials have the same powder size.

Detection of haemoglobins with abnormal oxygen affinity by single blood gas analysis and 2,3-diphosphoglycerate measurement.

PubMed

Guerrini, G; Morabito, A; Samaja, M

2000-10-01

The aim is to determine if a single measurement of blood 2,3-diphosphoglycerate combined with gas analysis (pH, PCO2, PO2 and saturation) can identify the cause of an altered blood-oxygen affinity: the presence of an abnormal haemoglobin or a red cell disorder. The population (n=94) was divided into healthy controls (A, n=14), carriers of red cell disorders (B, n=72) and carriers of high oxygen affinity haemoglobins (C, n=8). Those variables were measured both in samples equilibrated at selected PCO2 and PO2 and in venous blood. In the univariable approach applied to equilibrated samples, we correctly identified C subjects in 93.6% or 96.8% of the cases depending on the selected variable, the standard P50 (PO2 at which 50% of haemoglobin is oxygenated) or a composite variable calculated from the above measurements. After introducing the haemoglobin concentration as a further discriminating variable, the A and B subjects were correctly identified in 91.9% or 94.2% of the cases, respectively. These figures become 93.0% or 86.1%, and 93.7% or 94.9% of the cases when using direct readings from venous blood, thereby avoiding the blood equilibration step. This test is feasible also in blood samples stored at 4 degrees C for 48 h, or at room temperature for 8 h.

Leaf water content and palisade cell size.

PubMed

Canny, M J; Huang, C X

2006-01-01

The palisade cell sizes in leaves of Eucalyptus pauciflora were estimated in paradermal sections of cryo-fixed leaves imaged in the cryo-scanning electron microscope, as a quantity called the cell area fraction (CAF). Cell sizes were measured in detached leaves as a function of leaf water content, in intact leaves in the field during a day"s transpiration as a function of balance pressure of adjacent leaves, and on leaf disks equilibrated with air of relative humidities from 100 to 58%. Values of CAF ranged from 0.82 at saturation to approx. 0.3 in leaves dried to a relative water content (RWC) of 0.5, and in the field to approx. 0.58 at 15 bar (1.5 MPa) balance pressure. At a CAF of 0.58, the moisture content of the cell walls is in equilibrium with air at 90% relative humidity, which is the estimated relative humidity in the intercellular spaces. It is shown that at this moisture content, the cell walls could be exerting a pressure of approx. 50 bar on the cell contents.

Sickling of red blood cells through rapid oxygen exchange in microfluidic drops.

PubMed

Abbyad, Paul; Tharaux, Pierre-Louis; Martin, Jean-Louis; Baroud, Charles N; Alexandrou, Antigoni

2010-10-07

We have developed a microfluidic approach to study the sickling of red blood cells associated with sickle cell anemia by rapidly varying the oxygen partial pressure within flowing microdroplets. By using the perfluorinated carrier oil as a sink or source of oxygen, the oxygen level within the water droplets quickly equilibrates through exchange with the surrounding oil. This provides control over the oxygen partial pressure within an aqueous drop ranging from 1 kPa to ambient partial pressure, i.e. 21 kPa. The dynamics of the oxygen exchange is characterized through fluorescence lifetime measurements of a ruthenium compound dissolved in the aqueous phase. The gas exchange is shown to occur primarily during and directly after droplet formation, in 0.1 to 0.5 s depending on the droplet diameter and speed. The controlled deoxygenation is used to trigger the polymerization of hemoglobin within sickle red blood cells, encapsulated in drops. This process is observed using polarization microscopy, which yields a robust criterion to detect polymerization based on transmitted light intensity through crossed polarizers.

Probing microscopic material properties inside simulated membranes through spatially resolved three-dimensional local pressure fields and surface tensions

PubMed Central

Kasson, Peter M.; Hess, Berk; Lindahl, Erik

2013-01-01

Cellular lipid membranes are spatially inhomogeneous soft materials. Materials properties such as pressure and surface tension thus show important microscopic-scale variation that is critical to many biological functions. We present a means to calculate pressure and surface tension in a 3D-resolved manner within molecular-dynamics simulations and show how such measurements can yield important insight. We also present the first corrections to local virial and pressure fields to account for the constraints typically used in lipid simulations that otherwise cause problems in highly oriented systems such as bilayers. Based on simulations of an asymmetric bacterial ion channel in a POPC bilayer, we demonstrate how 3D-resolved pressure can probe for both short-range and long-range effects from the protein on the membrane environment. We also show how surface tension is a sensitive metric for inter-leaflet equilibrium and can be used to detect even subtle imbalances between bilayer leaflets in a membrane-protein simulation. Since surface tension is known to modulate the function of many proteins, this effect is an important consideration for predictions of ion channel function. We outline a strategy by which our local pressure measurements, which we make available within a version of the GROMACS simulation package, may be used to design optimally equilibrated membrane-protein simulations. PMID:23318532

Experimental Phase Relations of Hydrous, Primitive Melts: Implications for variably depleted mantle melting in arcs and the generation of primitive high-SiO2 melts

NASA Astrophysics Data System (ADS)

Weaver, S.; Wallace, P. J.; Johnston, A.

2010-12-01

There has been considerable experimental and theoretical work on how the introduction of H2O-rich fluids into the mantle wedge affects partial melting in arcs and chemical evolution of mantle melts as they migrate through the mantle. Studies aimed at describing these processes have become largely quantitative, with an emphasis on creating models that suitably predict the production and evolution of melts and describe the thermal state of arcs worldwide. A complete experimental data set that explores the P-T conditions of melt generation and subsequent melt extraction is crucial to the development, calibration, and testing of these models. This work adds to that data set by constraining the P-T-H2O conditions of primary melt extraction from two end-member subduction zones, a continental arc (Mexico) and an intraoceanic arc (Aleutians). We present our data in context with primitive melts found worldwide and with other experimental studies of melts produced from fertile and variably depleted mantle sources. Additionally, we compare our experimental results to melt compositions predicted by empirical and thermodynamic models. We used a piston-cylinder apparatus and employed an inverse approach in our experiments, constraining the permissible mantle residues with which our melts could be in equilibrium. We confirmed our inverse approach with forced saturation experiments at the P-T-H2O conditions of melt-mantle equilibration. Our experimental results show that a primitive, basaltic andesite melt (JR-28) from monogenetic cinder cone Volcan Jorullo (Central Mexico) last equilibrated with a harzburgite mantle residue at 1.2-1.4 GPa and 1150-1175°C with H2O contents in the range of 5.5-7 wt% H2O prior to ascent and eruption. Phase relations of a tholeiitic high-MgO basaltic melt (ID-16) from the Central Aleutians (Okmok) show the conditions of last equilibration with a fertile lherzolite mantle residue at shallower (1.2 GPa) but hotter (1275°C) conditions with approximately 2 wt% H2O. Given the estimated crustal thicknesses of these two regions, our data suggest that both samples equilibrate with mantle minerals just below the Moho. Recent viscosity dependent thermal models that account for slab geometry suggest that JR-28 melts last equilibrate with harzburgite in a cooler region of the mantle wedge. In contrast, ID-16 equilibrated with a fertile source near the hotter core of the mantle wedge. Our results support the hypothesis that lherzolite melting (wet or dry) produces essentially basaltic melts, whereas more Si-rich primitive melts require shallow hydrous melting of harzburgite or reequilibration of basaltic melts with harzburgite in the uppermost part of the wedge.

Simultaneous measurement and integrated analysis of analgesia and respiration after an intravenous morphine infusion.

PubMed

Dahan, Albert; Romberg, Raymonda; Teppema, Luc; Sarton, Elise; Bijl, Hans; Olofsen, Erik

2004-11-01

To study the influence of morphine on chemical control of breathing relative to the analgesic properties of morphine, the authors quantified morphine-induced analgesia and respiratory depression in a single group of healthy volunteers. Both respiratory and pain measurements were performed over single 24-h time spans. Eight subjects (four men, four women) received a 90-s intravenous morphine infusion; eight others (four men, four women) received a 90-s placebo infusion. At regular time intervals, respiratory variables (breathing at a fixed end-tidal partial pressure of carbon dioxide of 50 mmHg and the isocapnic acute hypoxic response), pain tolerance (derived from a transcutaneous electrical acute pain model), and arterial blood samples were obtained. Data acquisition continued for 24 h. Population pharmacokinetic (sigmoid Emax)-pharmacodynamic models were applied to the respiratory and pain data. The models are characterized by potency parameters, shape parameters (gamma), and blood-effect site equilibration half-lives. All collected data were analyzed simultaneously using the statistical program NONMEM. Placebo had no systematic effect on analgesic or respiratory variables. Morphine potency parameter and blood-effect site equilibration half-life did not differ significantly among the three measured effect parameters (P > 0.01). The integrated NONMEM analysis yielded a potency parameter of 32 +/- 1.4 nm (typical value +/- SE) and a blood-effect site equilibration half-life of 4.4 +/- 0.3 h. Parameter gamma was 1 for hypercapnic and hypoxic breathing but 2.4 +/- 0.7 for analgesia (P < 0.01). Our data indicate that systems involved in morphine-induced analgesia and respiratory depression share important pharmacodynamic characteristics. This suggests similarities in central mu-opioid analgesic and respiratory pathways (e.g., similarities in mu-opioid receptors and G proteins). The clinical implication of this study is that after morphine administration, despite lack of good pain relief, moderate to severe respiratory depression remains possible.

Electron storage in single wall carbon nanotubes. Fermi level equilibration in semiconductor-SWCNT suspensions.

PubMed

Kongkanand, Anusorn; Kamat, Prashant V

2007-08-01

The use of single wall carbon nanotubes (SWCNTs) as conduits for transporting electrons in a photoelectrochemical solar cell and electronic devices requires better understanding of their electron-accepting properties. When in contact with photoirradiated TiO(2) nanoparticles, SWCNTs accept and store electrons. The Fermi level equilibration with photoirradiated TiO(2) particles indicates storage of up to 1 electron per 32 carbon atoms in the SWCNT. The stored electrons are readily discharged on demand upon addition of electron acceptors such as thiazine and oxazine dyes (reduction potential less negative than that of the SWCNT conduction band) to the TiO(2)-SWCNT suspension. The stepwise electron transfer from photoirradiated TiO(2) nanoparticles --> SWCNT --> redox couple has enabled us to probe the electron equilibration process and determine the apparent Fermi level of the TiO(2)-SWCNT system. A positive shift in apparent Fermi level (20-30 mV) indicates the ability of SWCNTs to undergo charge equilibration with photoirradiated TiO(2) particles. The dependence of discharge capacity on the reduction potential of the dye redox couple is compared for TiO(2) and TiO(2)-SWCNT systems under equilibration conditions.

The Perils of Partition: Difficulties in Retrieving Magma Compositions from Chemically Equilibrated Basaltic Meteorites

NASA Technical Reports Server (NTRS)

Treiman, Allan H.

1996-01-01

The chemical compositions of magmas can be derived from the compositions of their equilibrium minerals through mineral/magma partition coefficients. This method cannot be applied safely to basaltic rocks, either solidified lavas or cumulates, which have chemically equilibrated or partially equilibrated at subsolidus temperatures, i.e., in the absence of magma. Applying mineral/ melt partition coefficients to mineral compositions from such rocks will typically yield 'magma compositions' that are strongly fractionated and unreasonably enriched in incompatible elements (e.g., REE's). In the absence of magma, incompatible elements must go somewhere; they are forced into minerals (e.g., pyroxenes, plagioclase) at abundance levels far beyond those established during normal mineral/magma equilibria. Further, using mineral/magma partition coefficients with such rocks may suggest that different minerals equilibrated with different magmas, and the fractionation sequence of those melts (i.e., enrichment in incompatible elements) may not be consistent with independent constraints on the order of crystallization. Subsolidus equilibration is a reasonable cause for incompatible- element-enriched minerals in some eucrites, diogenites, and martian meteorites and offers a simple alternative to petrogenetic schemes involving highly fractionated magmas or magma infiltration metasomatism.

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: I. Laboratory development

USGS Publications Warehouse

Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

2008-01-01

A gel probe equilibrium sampler has been developed to study arsenic (As) geochemistry and sorption behavior in sediment porewater. The gels consist of a hydrated polyacrylamide polymer, which has a 92% water content. Two types of gels were used in this study. Undoped (clear) gels were used to measure concentrations of As and other elements in sediment porewater. The polyacrylamide gel was also doped with hydrous ferric oxide (HFO), an amorphous iron (Fe) oxyhydroxide. When deployed in the field, HFO-doped gels introduce a fresh sorbent into the subsurface thus allowing assessment of in situ sorption. In this study, clear and HFO-doped gels were tested under laboratory conditions to constrain the gel behavior prior to field deployment. Both types of gels were allowed to equilibrate with solutions of varying composition and re-equilibrated in acid for analysis. Clear gels accurately measured solution concentrations (??1%), and As was completely recovered from HFO-doped gels (??4%). Arsenic speciation was determined in clear gels through chromatographic separation of the re-equilibrated solution. For comparison to speciation in solution, mixtures of As(III) and As(V) adsorbed on HFO embedded in gel were measured in situ using X-ray absorption spectroscopy (XAS). Sorption densities for As(III) and As(V) on HFO embedded in gel were obtained from sorption isotherms at pH 7.1. When As and phosphate were simultaneously equilibrated (in up to 50-fold excess of As) with HFO-doped gels, phosphate inhibited As sorption by up to 85% and had a stronger inhibitory effect on As(V) than As(III). Natural organic matter (>200 ppm) decreased As adsorption by up to 50%, and had similar effects on As(V) and As(III). The laboratory results provide a basis for interpreting results obtained by deploying the gel probe in the field and elucidating the mechanisms controlling As partitioning between solid and dissolved phases in the environment. ?? 2008 American Chemical Society.

Petrology of Two Itokawa Particles: Comparison with Equilibrated LL Chondrites

NASA Technical Reports Server (NTRS)

Komatsu, M.; Mikouchi, T.; Arai, T.; Fagan, T. J.; Zolensky, M.; Hagiya, K.; Ohsumi, K.; Karouji, Y.

2015-01-01

A strong link between Itokawa particles and LL chondrites was confirmed by preliminary examinations of Hayabusa particles [e.g., 1, 2]. Both poorly equilibrated and highly equilibrated particles have been found among the grains returned from Itokawa [1], and it is suggested that they correspond to LL4 and LL5-6, respectively. Here we report the petrography of two Itokawa particles and TEM study of one, and compare them to Antarctic LL chondrites with variable petrologic types (LL4-LL7) in order to understand the metamorphic history of asteroid Itokawa.

Technical Consultation of the International Space Station (ISS) Internal Active Thermal Control System (IATCS) Cooling Water Chemistry

NASA Technical Reports Server (NTRS)

Gentz, Steven J.; Rotter, Hank A.; Easton, Myriam; Lince, Jeffrey; Park, Woonsup; Stewart, Thomas; Speckman, Donna; Dexter, Stephen; Kelly, Robert

2005-01-01

The Internal Active Thermal Control System (IATCS) coolant exhibited unexpected chemical changes during the first year of on-orbit operation following the launch and activation in February 2001. The coolant pH dropped from 9.3 to below the minimum specification limit of 9.0, and re-equilibrated between 8.3 and 8.5. This drop in coolant pH was shown to be the result of permeation of CO2 from the cabin into the coolant via Teflon flexible hoses which created carbonic acid in the fluid. This unexpected diffusion was the result of having a cabin CO2 partial pressure higher than the ground partial pressure (average 4.0 mmHg vs. less than 0.2 mmHg). This drop in pH was followed by a concurrent increasing coolant nickel concentration. No other metal ions were observed in the coolant and based on previous tests, the source of nickel ion was thought to be the boron nickel (BNi) braze intermetallics used in the construction of HXs and cold plates. Specifically, BNi2 braze alloy was used for the IATCS IFHX and BNi3 braze alloy was used for the IATCS Airlock Servicing and Performance Checkout Unit (SPCU) HX and cold plates. Given the failure criticality of the HXs, a Corrosion Team was established by the IATCS CWG to determine the impact of the nickel corrosion on hardware performance life.

Direct Coexistence Methods to Determine the Solubility of Salts in Water from Numerical Simulations. Test Case NaCl.

PubMed

Manzanilla-Granados, Héctor M; Saint-Martín, Humberto; Fuentes-Azcatl, Raúl; Alejandre, José

2015-07-02

The solubility of NaCl, an equilibrium between a saturated solution of ions and a solid with a crystalline structure, was obtained from molecular dynamics simulations using the SPC/E and TIP4P-Ew water models. Four initial setups on supersaturated systems were tested on sodium chloride (NaCl) solutions to determine the equilibrium conditions and computational performance: (1) an ionic solution confined between two crystal plates of periodic NaCl, (2) a solution with all the ions initially distributed randomly, (3) a nanocrystal immersed in pure water, and (4) a nanocrystal immersed in an ionic solution. In some cases, the equilibration of the system can take several microseconds. The results from this work showed that the solubility of NaCl was the same, within simulation error, for the four setups, and in agreement with previously reported values from simulations with the setup (1). The system of a nanocrystal immersed in supersaturated solution was found to equilibrate faster than others. In agreement with laser-Doppler droplet measurements, at equilibrium with the solution the crystals in all the setups had a slight positive charge.

eQuilibrator--the biochemical thermodynamics calculator.

PubMed

Flamholz, Avi; Noor, Elad; Bar-Even, Arren; Milo, Ron

2012-01-01

The laws of thermodynamics constrain the action of biochemical systems. However, thermodynamic data on biochemical compounds can be difficult to find and is cumbersome to perform calculations with manually. Even simple thermodynamic questions like 'how much Gibbs energy is released by ATP hydrolysis at pH 5?' are complicated excessively by the search for accurate data. To address this problem, eQuilibrator couples a comprehensive and accurate database of thermodynamic properties of biochemical compounds and reactions with a simple and powerful online search and calculation interface. The web interface to eQuilibrator (http://equilibrator.weizmann.ac.il) enables easy calculation of Gibbs energies of compounds and reactions given arbitrary pH, ionic strength and metabolite concentrations. The eQuilibrator code is open-source and all thermodynamic source data are freely downloadable in standard formats. Here we describe the database characteristics and implementation and demonstrate its use.

eQuilibrator—the biochemical thermodynamics calculator

PubMed Central

Flamholz, Avi; Noor, Elad; Bar-Even, Arren; Milo, Ron

2012-01-01

The laws of thermodynamics constrain the action of biochemical systems. However, thermodynamic data on biochemical compounds can be difficult to find and is cumbersome to perform calculations with manually. Even simple thermodynamic questions like ‘how much Gibbs energy is released by ATP hydrolysis at pH 5?’ are complicated excessively by the search for accurate data. To address this problem, eQuilibrator couples a comprehensive and accurate database of thermodynamic properties of biochemical compounds and reactions with a simple and powerful online search and calculation interface. The web interface to eQuilibrator (http://equilibrator.weizmann.ac.il) enables easy calculation of Gibbs energies of compounds and reactions given arbitrary pH, ionic strength and metabolite concentrations. The eQuilibrator code is open-source and all thermodynamic source data are freely downloadable in standard formats. Here we describe the database characteristics and implementation and demonstrate its use. PMID:22064852

Achieving swift equilibration of a Brownian particle using flow-fields

NASA Astrophysics Data System (ADS)

Patra, Ayoti; Jarzynski, Christopher

Can a system be driven to a targeted equilibrium state on a timescale that is much shorter than its natural equilibration time? In a recent experiment, the swift equilibration of an overdamped Brownian particle was achieved by use of an appropriately designed, time-dependent optical trap potential. Motivated by these results, we develop a general theoretical approach for guiding an ensemble of Brownian particles to track the instantaneous equilibrium distribution of a desired potential U (q , t) . In our approach, we use flow-fields associated with the parametric evolution of the targeted equilibrium state to construct an auxiliary potential U (q , t) , such that dynamics under the composite potential U (t) + U (t) achieves the desired evolution. Our results establish a close connection between the swift equilibration of Brownian particles, quantum shortcuts to adiabaticity, and the dissipationless driving of a classical, Hamiltonian system.

Effects of an alveolar recruitment maneuver on subdural pressure, brain swelling, and mean arterial pressure in patients undergoing supratentorial tumour resection: a randomized crossover study.

PubMed

Flexman, Alana M; Gooderham, Peter A; Griesdale, Donald E; Argue, Ruth; Toyota, Brian

2017-06-01

Although recruitment maneuvers have been advocated as part of a lung protective ventilation strategy, their effects on cerebral physiology during elective neurosurgery are unknown. Our objectives were to determine the effects of an alveolar recruitment maneuver on subdural pressure (SDP), brain relaxation score (BRS), and cerebral perfusion pressure among patients undergoing supratentorial tumour resection. In this prospective crossover study, patients scheduled for resection of a supratentorial brain tumour were randomized to undergo either a recruitment maneuver (30 cm of water for 30 sec) or a "sham" maneuver (5 cm of water for 30 sec), followed by the alternative intervention after a 90-sec equilibration period. Subdural pressure was measured through a dural perforation following opening of the cranium. Subdural pressure and mean arterial pressure (MAP) were recorded continuously. The blinded neurosurgeon provided a BRS at baseline and at the end of each intervention. During each treatment, the changes in SDP, BRS, and MAP were compared. Twenty-one patients underwent the study procedure. The increase in SDP was higher during the recruitment maneuver than during the sham maneuver (difference, 3.9 mmHg; 95% confidence interval [CI], 2.2 to 5.6; P < 0.001). Mean arterial pressure decreased further in the recruitment maneuver than in the sham maneuver (difference, -9.0 mmHg; 95% CI, -12.5 to -5.6; P < 0.001). Cerebral perfusion pressure decreased 14 mmHg (95% CI, 4 to 24) during the recruitment maneuver. The BRS did not change with either maneuver. Our results suggest that recruitment maneuvers increase subdural pressure and reduce cerebral perfusion pressure, although the clinical importance of these findings is thus far unknown. This trial was registered with ClinicalTrials.gov, NCT02093117.

Using artificial intelligence to predict the equilibrated postdialysis blood urea concentration.

PubMed

Fernández, E A; Valtuille, R; Willshaw, P; Perazzo, C A

2001-01-01

Total dialysis dose (Kt/V) is considered to be a major determinant of morbidity and mortality in hemodialyzed patients. The continuous growth of the blood urea concentration over the 30- to 60-min period following dialysis, a phenomenon known as urea rebound, is a critical factor in determining the true dose of hemodialysis. The misestimation of the equilibrated (true) postdialysis blood urea or equilibrated Kt/V results in an inadequate hemodialysis prescription, with predictably poor clinical outcomes for the patients. The estimation of the equilibrated postdialysis blood urea (eqU) is therefore crucial in order to estimate the equilibrated (true) Kt/V. In this work we propose a supervised neural network to predict the eqU at 60 min after the end of hemodialysis. The use of this model is new in this field and is shown to be better than the currently accepted methods (Smye for eqU and Daugirdas for eqKt/V). With this approach we achieve a mean difference error of 0.22 +/- 7.71 mg/ml (mean % error: 1.88 +/- 13.46) on the eqU prediction and a mean difference error for eqKt/V of -0.01 +/- 0.15 (mean % error: -0.95 +/- 14.73). The equilibrated Kt/V estimated with the eqU calculated using the Smye formula is not appropriate because it showed a great dispersion. The Daugirdas double-pool Kt/V estimation formula appeared to be accurate and in agreement with the results of the HEMO study. Copyright 2001 S. Karger AG, Basel.

A randomized prospective study of desflurane versus isoflurane in minimal flow anesthesia using “equilibration time” as the change-over point to minimal flow

PubMed Central

Mallik, Tanuja; Aneja, S; Tope, R; Muralidhar, V

2012-01-01

Background: In the administration of minimal flow anesthesia, traditionally a fixed time period of high flow has been used before changing over to minimal flow. However, newer studies have used “equilibration time” of a volatile anesthetic agent as the change-over point. Materials and Methods: A randomized prospective study was conducted on 60 patients, who were divided into two groups of 30 patients each. Two volatile inhalational anesthetic agents were compared. Group I received desflurane (n = 30) and group II isoflurane (n = 30). Both the groups received an initial high flow till equilibration between inspired (Fi) and expired (Fe) agent concentration were achieved, which was defined as Fe/Fi = 0.8. The mean (SD) equilibration time was obtained for both the agent. Then, a drift in end-tidal agent concentration during the minimal flow anesthesia and recovery profile was noted. Results: The mean equilibration time obtained for desflurane and isoflurane were 4.96 ± 1.60 and 16.96 ± 9.64 min (P < 0.001). The drift in end-tidal agent concentration over time was minimal in the desflurane group (P = 0.065). Recovery time was 5.70 ± 2.78 min in the desflurane group and 8.06 ± 31 min in the isoflurane group (P = 0.004). Conclusion: Use of equilibration time of the volatile anesthetic agent as a change-over point, from high flow to minimal flow, can help us use minimal flow anesthesia, in a more efficient way. PMID:23225926

New high pressure experiments on sulfide saturation of high-FeO∗ basalts with variable TiO2 contents - Implications for the sulfur inventory of the lunar interior

NASA Astrophysics Data System (ADS)

Ding, Shuo; Hough, Taylor; Dasgupta, Rajdeep

2018-02-01

In order to constrain sulfur concentration in intermediate to high-Ti mare basalts at sulfide saturation (SCSS), we experimentally equilibrated FeS melt and basaltic melt using a piston cylinder at 1.0-2.5 GPa and 1400-1600 °C, with two silicate compositions similar to high-Ti (Apollo 11: A11, ∼11.1 wt.% TiO2, 19.1 wt.% FeO∗, and 39.6 wt.% SiO2) and intermediate-Ti (Luna 16, ∼5 wt.% TiO2, 18.7 wt.% FeO∗, and 43.8 wt.% SiO2) mare basalts. Our experimental results show that SCSS increases with increasing temperature, and decreases with increasing pressure, which are similar to the results from previous experimental studies. SCSS in the A11 melt is systematically higher than that in the Luna 16 melt, which is likely due to higher FeO∗, and lower SiO2 and Al2O3 concentration in the former. Compared to the previously constructed SCSS models, including those designed for high-FeO∗ basalts, the SCSS values determined in this study are generally lower than the predicted values, with overprediction increasing with increasing melt TiO2 content. We attribute this to the lower SiO2 and Al2O3 concentration of the lunar magmas, which is beyond the calibration range of previous SCSS models, and also more abundant FeTiO3 complexes in our experimental melts that have higher TiO2 contents than previous models' calibration range. The formation of FeTiO3 complexes lowers the activity of FeO∗, a FeO∗silicatemelt , and therefore causes SCSS to decrease. To accommodate the unique lunar compositions, we have fitted a new SCSS model for basaltic melts of >5 wt.% FeO∗ and variable TiO2 contents. Using previous chalcophile element partitioning experiments that contained more complex Fe-Ni-S sulfide melts, we also derived an empirical correction that allows SCSS calculation for basalts where the equilibrium sulfides contain variable Ni contents of 10-50 wt.%. At the pressures and temperatures of multiple saturation points, SCSS of lunar magmas with compositions from picritic glasses, mare basalts, to young lunar meteorites vary from 2600 to 4800 ppm for basalt equilibration with a pure FeS melt and from 1400 to 2600 ppm for basalt equilibration with a Fe-rich sulfide melt containing 30 wt.% Ni. The measured S contents in these proposed near-primary lunar magmas are lower than the predicted SCSS at the conditions of their last equilibration with the lunar mantle, indicating no sulfide retention in the lunar mantle source during partial melting. Sulfide exhaustion during partial melting in the lunar mantle also supports the notion that the bulk silicate moon is depleted in highly siderophile elements. Based on the measured S contents and the estimated degree of melting, the estimated S contents for the mantle source of A15 green glass and A15 mare basalts is 10-23 ppm; for A17 orange glass is 25-62 ppm, for A12 mare basalts is 27-92 ppm, and for A11 basalt is 35-120 ppm. Consideration of SCSS decrease due to the presence of Ni in the sulfide melt does not change these mantle S abundance estimates for <30 wt.% Ni in the sulfide. The inferred S contents suggest that the lunar mantle is heterogeneous in terms of S. Although variable among different groups, the inferred S abundance of up to 120 ppm in the lunar mantle falls near the lower end of the S content of the depleted terrestrial mantle such as the MORB source.

Elastic Wave Velocity Measurements on Mantle Peridotite at High Pressure and Temperature

NASA Astrophysics Data System (ADS)

Mistler, G. W.; Ishikawa, M.; Li, B.

2002-12-01

With the success of conducting ultrasonic measurements at high pressure and high temperature in large volume high pressure apparatus with in-situ measurement of the sample length by X-ray imaging, it is now possible to measure elastic wave velocities on aggregate samples with candidate compositions of the mantle to the conditions of the Earth's transition zone in the laboratory. These data can be directly compared with seismic data to distinguish the compositional models in debate. In this work, we carried out velocity measurements on natural peridotite KLB-1 at the conditions of the Earth's upper mantle. Fine powered sample of natural KLB-1 was used as starting material. Specimens for ultrasonic measurements were hot-pressed and equilibrated at various pressure and temperature conditions along geotherm up to the transition zone. The recovered samples were characterized with density measurement, X-ray diffraction and microprobe analysis. Bench top P and S wave velocities of KLB-1 sample sintered at 3-4 GPa and 1400 degree centigrade showed a very good agreement with the VRH average of pyrolite. High pressure and high temperature measurements was conducted up to 7 GPa and 800 degree centigrade using ultrasonic interferometric method in a DIA-type high pressure apparatus in conjunction with X-ray diffraction and X-ray imaging. The utilization of X-ray imaging technique provides direct measurements of sample lengths at high pressure and high temperature, ensuring a precise determination of velocities. The results of P and S wave velocities at high pressure and high temperature as well as their comparison with calculated pyrolite model will be presented.

Thermal, dynamic and compositional aspects of the core-forming Earth

NASA Technical Reports Server (NTRS)

Stevenson, D. J.

1985-01-01

Core formation is the most important and singular differentiation event in the history of a terrestrial planet. It almost certainly involved the downward migration of a partially or wholly molten iron alloy through a silicate and oxide mantle, and was contemporaneous with accretion. Several important, unresolved issues which have implications for mantle and core geochemistry, the thermal history of the Earth, and the origin of geomagnetism are addressed: whether the early Earth was molten; whether core formation involved low or high pressure geochemistry, or both; early Earth mantle homogenization; whether equilibration established between core forming material and the mantle through which it migrated; and how much iron is stranded and unable to reach the core.

Determination of Activities of Niobium in Cu-Nb Melts Containing Dilute Nb

NASA Astrophysics Data System (ADS)

Wang, Daya; Yan, Baijun; Sichen, Du

2015-04-01

The activity coefficients of niobium in Cu-Nb melts were measured by equilibrating solid NbO2 with liquid copper under controlled oxygen potentials in the temperature range of 1773 K to 1898 K (1500 °C to 1625 °C). Either CO-CO2 gas mixture or H2-CO2 gas mixture was employed to obtain the desired oxygen partial pressures. Cu-Nb system was found to follow Henry's law in the composition range studied. The temperature dependence of Henry's constant in the Cu-Nb melts could be expressed as follows: The partial molar excess Gibbs energy change of niobium in Cu-Nb melts can be expressed as follows:

The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure

NASA Technical Reports Server (NTRS)

Barnes, S. J.

1986-01-01

The Cr distributions for a synthetic silicate melt equilibrated with bronzitic orthopyroxene and chromite spinel between 1334 and 1151 C over a range of oxygen fugacities between the nickel-nickel oxide and iron-wuestite buffers are studied. The occurrence, chemical composition, and structure of the orthopyroxene-silicate melt and the spinel-silicate melt are described. It is observed that the Cr content between bronzite and the melt increases with falling temperature along a given oxygen buffer and decreases with falling oxygen fugacity at a given temperature; however, the Cr content of the melt in equilibrium with spinel decreases with falling temperature and increases with lower oxygen fugacity.

Effects of oxygen-augmented atmosphere on the immune response.

NASA Technical Reports Server (NTRS)

Guttman, H. N.

1973-01-01

Antibovine serum albumin antibody and nonspecific protein production was evaluated in female rabbits (11-14.5 kg) housed in special cages ventilated with 20% or 40% oxygen at normal barometric pressure. Animals exposed to 40% oxygen do not show normal steady increase of serum antibody. Instead, their titers show a pattern of undershoot, overshoot, undershoot, and finally equilibration at a subnormal level; they have a depressed popliteal node polysome level and have an abnormally low proportion of membrane-bound polysomes. They also show reduced capability of popliteal nodes to synthesize protein (as expected from the reduced number of polysomes). However, the ratio of newly-synthesized specific antibody: nonspecific protein remains normal.

Analysis of Dynamic Fracture Compliance Based on Poroelastic Theory - Part II: Results of Numerical and Experimental Tests

NASA Astrophysics Data System (ADS)

Wang, Ding; Ding, Pin-bo; Ba, Jing

2018-03-01

In Part I, a dynamic fracture compliance model (DFCM) was derived based on the poroelastic theory. The normal compliance of fractures is frequency-dependent and closely associated with the connectivity of porous media. In this paper, we first compare the DFCM with previous fractured media theories in the literature in a full frequency range. Furthermore, experimental tests are performed on synthetic rock specimens, and the DFCM is compared with the experimental data in the ultrasonic frequency band. Synthetic rock specimens saturated with water have more realistic mineral compositions and pore structures relative to previous works in comparison with natural reservoir rocks. The fracture/pore geometrical and physical parameters can be controlled to replicate approximately those of natural rocks. P- and S-wave anisotropy characteristics with different fracture and pore properties are calculated and numerical results are compared with experimental data. Although the measurement frequency is relatively high, the results of DFCM are appropriate for explaining the experimental data. The characteristic frequency of fluid pressure equilibration calculated based on the specimen parameters is not substantially less than the measurement frequency. In the dynamic fracture model, the wave-induced fluid flow behavior is an important factor for the fracture-wave interaction process, which differs from the models at the high-frequency limits, for instance, Hudson's un-relaxed model.

Cell Surface Mechanochemistry and the Determinants of Bleb Formation, Healing, and Travel Velocity

PubMed Central

Manakova, Kathryn; Yan, Huaming; Lowengrub, John; Allard, Jun

2016-01-01

Blebs are pressure-driven cell protrusions implicated in cellular functions such as cell division, apoptosis, and cell motility, including motility of protease-inhibited cancer cells. Because of their mechanical nature, blebs inform us about general cell-surface mechanics, including membrane dynamics, pressure propagation throughout the cytoplasm, and the architecture and dynamics of the actin cortex. Mathematical models including detailed fluid dynamics have previously been used to understand bleb expansion. Here, we develop mathematical models in two and three dimensions on longer timescales that recapitulate the full bleb life cycle, including both expansion and healing by cortex reformation, in terms of experimentally accessible biophysical parameters such as myosin contractility, osmotic pressure, and turnover of actin and ezrin. The model provides conditions under which blebbing occurs, and naturally gives rise to traveling blebs. The model predicts conditions under which blebs travel or remain stationary, as well as the bleb traveling velocity, a quantity that has remained elusive in previous models. As previous studies have used blebs as reporters of membrane tension and pressure dynamics within the cell, we have used our system to investigate various pressure equilibration models and dynamic, nonuniform membrane tension to account for the shape of a traveling bleb. We also find that traveling blebs tend to expand in all directions unless otherwise constrained. One possible constraint could be provided by spatial heterogeneity in, for example, adhesion density. PMID:27074688

Sequential peritoneal equilibration test: a new method for assessment and modelling of peritoneal transport.

PubMed

Galach, Magda; Antosiewicz, Stefan; Baczynski, Daniel; Wankowicz, Zofia; Waniewski, Jacek

2013-02-01

In spite of many peritoneal tests proposed, there is still a need for a simple and reliable new approach for deriving detailed information about peritoneal membrane characteristics, especially those related to fluid transport. The sequential peritoneal equilibration test (sPET) that includes PET (glucose 2.27%, 4 h) followed by miniPET (glucose 3.86%, 1 h) was performed in 27 stable continuous ambulatory peritoneal dialysis patients. Ultrafiltration volumes, glucose absorption, ratio of concentration in dialysis fluid to concentration in plasma (D/P), sodium dip (Dip D/P Sodium), free water fraction (FWF60) and the ultrafiltration passing through small pores at 60 min (UFSP60), were calculated using clinical data. Peritoneal transport parameters were estimated using the three-pore model (3p model) and clinical data. Osmotic conductance for glucose was calculated from the parameters of the model. D/P creatinine correlated with diffusive mass transport parameters for all considered solutes, but not with fluid transport characteristics. Hydraulic permeability (L(p)S) correlated with net ultrafiltration from miniPET, UFSP60, FWF60 and sodium dip. The fraction of ultrasmall pores correlated with FWF60 and sodium dip. The sequential PET described and interpreted mechanisms of ultrafiltration and solute transport. Fluid transport parameters from the 3p model were independent of the PET D/P creatinine, but correlated with fluid transport characteristics from PET and miniPET.

Can the three pore model correctly describe peritoneal transport of protein?

PubMed

Waniewski, Jacek; Poleszczuk, Jan; Antosiewicz, Stefan; Baczynński, Daniel; Gałach, Magda; Pietribiasi, Mauro; Wanńkowicz, Zofia

2014-01-01

The three pore model (3PM) includes large pores for the description of protein leak to the peritoneal cavity during peritoneal dialysis. However, the reliability of this description has been not fully tested against clinical data yet. Peritoneal transport parameters were estimated using 3PM, extended 3p model (with estimation of fraction of large pores, ext3PM), ext3PM with modified size of pores and proteins (mext3PM), and simplified two pore (2PM, small and ultrasmall pores) models for 32 patients on peritoneal dialysis investigated using the sequential peritoneal equilibration test (consecutive peritoneal equilibration test [PET]: glucose 2.27%, 4 h, and miniPET: glucose 3.86%, 1 h). Urea, creatinine, glucose, sodium, phosphate, albumin, and IgM concentrations were measured in dialysis fluid and plasma. Ext3PM and mext3PM, with large pore fraction of about 0.14, provided a good description of fluid and small solute kinetics, but their predictions for albumin transport were less accurate. Two pore model precisely described the data on fluid and small solute transport. The 3p models could not describe the diffusive-convective transport of albumin as precisely as the transport of fluid, small solutes, and IgM. The 2p model (not applicable for proteins) was an efficient tool for modeling fluid and small solute transport.

Intercomparison of Lab-Based Soil Water Extraction Methods for Stable Water Isotope Analysis

NASA Astrophysics Data System (ADS)

Pratt, D.; Orlowski, N.; McDonnell, J.

2016-12-01

The effect of pore water extraction technique on resultant isotopic signature is poorly understood. Here we present results of an intercomparison of five common lab-based soil water extraction techniques: high pressure mechanical squeezing, centrifugation, direct vapor equilibration, microwave extraction, and cryogenic extraction. We applied five extraction methods to two physicochemically different standard soil types (silty sand and clayey loam) that were oven-dried and rewetted with water of known isotopic composition at three different gravimetric water contents (8, 20, and 30%). We tested the null hypothisis that all extraction techniques would provide the same isotopic result independent from soil type and water content. Our results showed that the extraction technique had a significant effect on the soil water isotopic composition. Each method exhibited deviations from spiked reference water, with soil type and water content showing a secondary effect. Cryogenic extraction showed the largest deviations from the reference water, whereas mechanical squeezing and centrifugation provided the closest match to the reference water for both soil types. We also compared results for each extraction technique that produced liquid water on both an OA-ICOS and IRMS; differences between them were negligible.

Reaction of Titanium and Zirconium Particles in Cylindrical Explosive Charges

NASA Astrophysics Data System (ADS)

Frost, David; Cairns, Malcolm; Goroshin, Samuel; Zhang, Fan

2007-06-01

The critical conditions for the reaction of high melting-point metallic particles (Ti, Zr) dispersed during the detonation of long cylindrical explosive charges have been investigated experimentally. The charges consisted of packed beds of either spherical titanium particles (with diameters of 35, 90, or 215 μm; AP&C, Inc.) or nonspherical zirconium particles (250 -- 500 μm or 500 -- 600 μm, Atlantic Equipment Eng., NJ) saturated with sensitized liquid nitromethane. For the titanium particles, a threshold particle diameter exists, above which self-sustained particle reaction is not observed, although some particle reaction occurs immediately behind the detonation front then rapidly quenches. For the smallest particles, the proportion of the conical particle cloud that reacts increases with charge diameter, suggesting that the reaction initiation is a competition between particle heating and expansion cooling of the products. For zirconium particles, no critical conditions exist; particle ignition was observed for all particle and charge diameters tested. In this case, interaction of the high pressure detonation wave with the particles is sufficient to initiate reaction at the particle surface after a delay time (˜ 10's μs), which is much less than the time required for thermal equilibration of the particles.

Experimental and theoretical analysis of the rate of solvent equilibration in the hanging drop method of protein crystal growth

NASA Technical Reports Server (NTRS)

Fowlis, William W.; Delucas, Lawrence J.; Twigg, Pamela J.; Howard, Sandra B.; Meehan, Edward J.

1988-01-01

The principles of the hanging-drop method of crystal growth are discussed, and the rate of water evaporation in a water droplet (containing protein, buffer, and a precipitating agent) suspended above a well containing a double concentration of precipitating agent is investigated theoretically. It is shown that, on earth, the rate of evaporation may be determined from diffusion theory and the colligative properties of solutions. The parameters affecting the rate of evaporation include the temperature, the vapor pressure of water, the ionization constant of the salt, the volume of the drop, the contact angle between the droplet and the coverslip, the number of moles of salt in the droplet, the number of moles of water and salt in the well, the molar volumes of water and salt, the distance from the droplet to the well, and the coefficient of diffusion of water vapor through air. To test the theoretical equations, hanging-drop experiments were conducted using various reagent concentrations in 25-microliter droplets and measuring the evaporation times at 4 C and 25 C. The results showed good agreement with the theory.

Repeated use of ion-exchange resin membranes in calcareous soils

USGS Publications Warehouse

Sherrod, S.K.; Belnap, Jayne; Miller, M.E.

2003-01-01

This study compared the consistency of nutrient extraction among repeated cycles of ion-exchange resin membrane use. Two sandy calcareous soils and different equilibration temperatures were tested. No single nutrient retained consistent values from cycle to cycle in all treatments, although both soil source and temperature conferred some influence. It was concluded that the most conservative use of resin membranes is single-use.

Effect Of Water On Permeation By Hydrogen

NASA Technical Reports Server (NTRS)

Tomazic, William A.; Hulligan, David

1988-01-01

Water vapor in working fluid equilibrates with permeability-reducing oxides in metal parts. Report describes study of effects of water on permeation of heater-head tubes by hydrogen in Stirling engine. Experiments performed to determine minimum concentration of oxygen and/or oxygen-bearing gas maintaining oxide coverage adequate for low permeability. Tests showed 750 ppm or more of water effective in maintaining stable, low permeability.

Modeled Urea Distribution Volume and Mortality in the HEMO Study

PubMed Central

Greene, Tom; Depner, Thomas A.; Levin, Nathan W.; Chertow, Glenn M.

2011-01-01

Summary Background and objectives In the Hemodialysis (HEMO) Study, observed small decreases in achieved equilibrated Kt/Vurea were noncausally associated with markedly increased mortality. Here we examine the association of mortality with modeled volume (Vm), the denominator of equilibrated Kt/Vurea. Design, setting, participants, & measurements Parameters derived from modeled urea kinetics (including Vm) and blood pressure (BP) were obtained monthly in 1846 patients. Case mix–adjusted time-dependent Cox regressions were used to relate the relative mortality hazard at each time point to Vm and to the change in Vm over the preceding 6 months. Mixed effects models were used to relate Vm to changes in intradialytic systolic BP and to other factors at each follow-up visit. Results Mortality was associated with Vm and change in Vm over the preceding 6 months. The association between change in Vm and mortality was independent of vascular access complications. In contrast, mortality was inversely associated with V calculated from anthropometric measurements (Vant). In case mix–adjusted analysis using Vm as a time-dependent covariate, the association of mortality with Vm strengthened after statistical adjustment for Vant. After adjustment for Vant, higher Vm was associated with slightly smaller reductions in intradialytic systolic BP and with risk factors for mortality including recent hospitalization and reductions in serum albumin concentration and body weight. Conclusions An increase in Vm is a marker for illness and mortality risk in hemodialysis patients. PMID:21511841

A model of oscillatory transport in granular soils, with application to barometric pumping and earth tides.

PubMed

Neeper, D A

2001-04-01

A simple algebraic model is proposed to estimate the transport of a volatile or soluble chemical caused by oscillatory flow of fluid in a porous medium. The model is applied to the barometric pumping of vapors in the vadose zone, and to the transport of dissolved species by earth tides in an aquifer. In the model, the fluid moves sinusoidally with time in the porosity of the soil. The chemical concentration in the mobile fluid is considered to equilibrate with the concentration in the surrounding matrix according to a characteristic time governed by diffusion, sorption, or other rate processes. The model provides a closed form solution, to which barometric pressure data are applied in an example of pore gas motion in the vadose zone. The model predicts that the additional diffusivity due barometric pumping in an unfractured vadose zone would be comparable to the diffusivity in stagnant pore gas if the equilibration time is 1 day or longer. Water motion due to the M2 lunar tide is examined as an example of oscillatory transport in an aquifer. It is shown that the tidal motion of the water in an aquifer might significantly increase the vertical diffusivity of dissolved species when compared to diffusion in an absolutely stagnant aquifer, but the hydrodynamic dispersivity due to tidal motion or gravitational flow would probably exceed the diffusivity due to oscillatory advection.

Multisystem Temperature Equilibration and the Second Law

ERIC Educational Resources Information Center

Leff, Harvey S.

1977-01-01

Shows that the entropy change during the temperature equilibration of an isolated collection of systems which may exchange heat (but not work) energy is positive when the constant-volume heat capacity of each system is a non-negative function of the temperature. (MLH)

Crossover from equilibration to aging: Nonequilibrium theory versus simulations.

PubMed

Mendoza-Méndez, P; Lázaro-Lázaro, E; Sánchez-Díaz, L E; Ramírez-González, P E; Pérez-Ángel, G; Medina-Noyola, M

2017-08-01

Understanding glasses and the glass transition requires comprehending the nature of the crossover from the ergodic (or equilibrium) regime, in which the stationary properties of the system have no history dependence, to the mysterious glass transition region, where the measured properties are nonstationary and depend on the protocol of preparation. In this work we use nonequilibrium molecular dynamics simulations to test the main features of the crossover predicted by the molecular version of the recently developed multicomponent nonequilibrium self-consistent generalized Langevin equation theory. According to this theory, the glass transition involves the abrupt passage from the ordinary pattern of full equilibration to the aging scenario characteristic of glass-forming liquids. The same theory explains that this abrupt transition will always be observed as a blurred crossover due to the unavoidable finiteness of the time window of any experimental observation. We find that within their finite waiting-time window, the simulations confirm the general trends predicted by the theory.

Impact of holding and equilibration time on post-thaw quality of shipped boar semen.

PubMed

Schäfer, J; Waberski, D; Jung, M; Schulze, M

2017-12-01

Cryopreservation of boar semen is of growing interest for breeding companies. Overnight-shipping of pre-diluted ejaculates to specialized laboratories offers a practicable method, but requires fine-tuned protocols. In this study, the impact of holding post shipping at 17°C for 2 or 24h (n=10 samples) and of equilibration in lactose-egg yolk extender without glycerol at 5°C for 2, 4, 24 or 48h (n=11 samples) before freezing was investigated. Sperm-rich fractions of ejaculates from 21 mature Pietrain boars were collected at a single boar stud. After pre-dilution (1+1, v:v) with Beltsville thawing solution, samples were sent to the laboratory. Temperature profiles during transport and initial equilibration time were recorded. Semen quality post-thaw (PT) was evaluated using CASA and flow cytometry. Holding of 2h after shipping resulted in higher sperm motility (P=0.013) and beat cross frequency (BCF; P=0.047) compared to 24h. Differences between both groups vanished with prolonged incubation at 38°C PT. Equilibration at 5°C for 4h yielded the highest motility and BCF, whereas the equilibration for 48h impaired sperm motility. Membrane integrity, mitochondrial activity and DNA fragmentation index were not affected by any protocol modification. In conclusion, processing of pre-diluted boar semen shipped overnight within 2h after arrival at the laboratory is preferred to 24h of additional holding at 17°C. Extending the equilibration period in lactose-egg yolk extender without glycerol at 5°C from 2h to 4h before freezing is recommended. Copyright © 2017 Elsevier B.V. All rights reserved.

A hydrogen isotope study of CO3 type carbonaceous chondrites; comparison with type 3 ordinary chondrites

NASA Technical Reports Server (NTRS)

Morse, A. D.; Newton, J.; Pillinger, C. T.

1993-01-01

Meteorites of the Ornans type 3 carbonaceous chondrites exhibit a range in degree of equilibration, attributed to differing amounts of thermal metamorphism. These differences have been used to split the CO3 chondrites into petrologic sub-types from 3.0, least equilibrated, to 3.7, being most equilibrated. This is similar to the system of assigning the type 3 ordinary chondrites into petrologic sub-types 3.0 to 3.9 based upon thermoluminescence (TL) and other properties; however, the actual range of thermal metamorphism experienced by CO3 chondrites is much less than that of the type 3 ordinary chondrites. The least equilibrated ordinary chondrites show evidence of aqueous alteration and have high D/H ratios possibly due to a deuterium-rich organic carrier. The aim of this study was to determine whether the CO3 chondrites, which have experienced similar secondary conditions to the type 3 ordinary chondrites, also contain a similar deuterium-rich carrier. To date a total of 5 CO3 meteorites, out of a set of 11 for which carbon and nitrogen isotopic data are available, have been analyzed. Ornans has not been analyzed yet, because it does not appear to fit in with the metamorphic sequence exhibited by the other CO3 chondrites; it also has an extremely high delta-D value of +2150 percent, unusual for such a comparatively equilibrated meteorite (type 3.4). Initial results indicate that the more equilibrated CO3's tend to have lower delta-D values, analogous to the higher petrologic type ordinary chondrites. However this is complicated by the effects of terrestrial weathering and the small data-set.

A new barometer from stress fields around inclusions

NASA Astrophysics Data System (ADS)

Avadanii, Diana; Hansen, Lars; Wallis, David; Waters, David

2017-04-01

A key step in understanding geological and geodynamic processes is modelling the pressure-temperature paths of metamorphic rocks. Traditional thermobarometry relies on mineral assemblage equilibria and thermodynamic modelling to infer the pressures and temperatures of chemical equilibration. This approach requires the presence of specific mineral assemblages and compositions, which narrows its applicability. In this study we aim to develop a geobarometer based on mechanical interactions between inclusions and their host grains. Exhumation of minerals with inclusions causes heterogeneous residual stress fields due to the different, and often anisotropic, elastic properties of the inclusion and host. Recent studies measure residual mean stresses within inclusions using Raman spectroscopy and use those stresses as a barometer. In contrast, we map each component of the stress tensor around inclusions using high angular-resolution electron backscatter diffraction (HR-EBSD). This technique provides both higher spatial resolution and increased sensitivity to elastic strains relative to Raman spectroscopy. We focus on quartz inclusions in garnet, a common feature in metamorphic rocks. This assemblage also provides an opportunity to test our results with compositional thermobarometry. We analyse samples metamorphosed at pressures ranging from ˜ 300 MPa to ˜ 1600 MPa, as recorded by independent geobarometers. HR-EBSD reveals symmetric and lobate signals around inclusions, with elastic strains and residual stresses of the order 10-3 and ±102 -103 MPa, respectively. We solve Eshelby's problem for the 'inhomogeneous inclusion' case to simulate the elastic strain/stress field around an anisotropic ellipsoidal inclusion surrounded by an isotropic, homogeneous, infinite matrix. This model calculates the stress disturbances caused by differential expansion of an inclusion and host subjected to decompression. We additionally account for differential expansion related to cooling by imposing an eigenstrain in the inclusion, according to the thermal expansivity of quartz. Thermal contraction in the host garnet is accounted for by modifying the macroscopic pressure. The simulations reproduce the general pattern of the elastic fields that we observe from HR-EBSD and account for different geometries of the inclusion. The simulations provide the basis for quantitatively relating the stress fields measured by HR-EBSD to the entrapment pressures of inclusions.

Critical fluid thermal equilibration experiment (19-IML-1)

NASA Technical Reports Server (NTRS)

Wilkinson, R. Allen

1992-01-01

Gravity sometimes blocks all experimental techniques of making a desired measurement. Any pure fluid possesses a liquid-vapor critical point. It is defined by a temperature, pressure, and density state in thermodynamics. The critical issue that this experiment attempts to understand is the time it takes for a sample to reach temperature and density equilibrium as the critical point is approached; is it infinity due to mass and thermal diffusion, or do pressure waves speed up energy transport while mass is still under diffusion control. The objectives are to observe: (1) large phase domain homogenization without and with stirring; (2) time evolution of heat and mass after temperature step is applied to a one phase equilibrium sample; (3) phase evolution and configuration upon going two phase from a one phase equilibrium state; (4) effects of stirring on a low g two phase configuration; (5) two phase to one phase healing dynamics starting from a two phase low g configuration; and (6) effects of shuttle acceleration events on spatially and temporally varying compressible critical fluid dynamics.

Sequential Injection Chromatography with an Ultra-short Monolithic Column for the Low-Pressure Separation of α-Tocopherol and γ-Oryzanol in Vegetable Oils and Nutrition Supplements.

PubMed

Thaithet, Sujitra; Kradtap Hartwell, Supaporn; Lapanantnoppakhun, Somchai

2017-01-01

A low-pressure separation procedure of α-tocopherol and γ-oryzanol was developed based on a sequential injection chromatography (SIC) system coupled with an ultra-short (5 mm) C-18 monolithic column, as a lower cost and more compact alternative to the HPLC system. A green sample preparation, dilution with a small amount of hexane followed by liquid-liquid extraction with 80% ethanol, was proposed. Very good separation resolution (R s = 3.26), a satisfactory separation time (10 min) and a total run time including column equilibration (16 min) were achieved. The linear working range was found to be 0.4 - 40 μg with R 2 being more than 0.99. The detection limits of both analytes were 0.28 μg with the repeatability within 5% RSD (n = 7). Quantitative analyses of the two analytes in vegetable oil and nutrition supplement samples, using the proposed SIC method, agree well with the results from HPLC.

Long-term frequency and amplitude stability of a solid-nitrogen-cooled, continuous wave THz quantum cascade laser

NASA Astrophysics Data System (ADS)

Danylov, Andriy A.; Waldman, Jerry; Light, Alexander R.; Goyette, Thomas M.; Giles, Robert H.; Qian, Xifeng; Chandrayan, Neelima; Goodhue, William D.; Nixon, William E.

2012-02-01

Operational temperature increase of CW THz QCLs to 77 K has enabled us to employ solid nitrogen (SN2) as the cryogen. A roughing pump was used to solidify liquid nitrogen and when the residual vapor pressure in the nitrogen reservoir reached the pumping system's minimum pressure the temperature equilibrated and remained constant until all the nitrogen sublimated. The hold time compared to liquid helium has thereby increased approximately 70-fold, and at a greatly reduced cost. The milliwatt CW QCL was at a temperature of approximately 60 K, dissipating 5 W of electrical power. To measure the long-term frequency, current, and temperature stability, we heterodyned the free-running 2.31 THz QCL with a CO2 pumped far-infrared gas laser line in methanol (2.314 THz) in a corner-cube Schottky diode and recorded the IF frequency, current and temperature. Under these conditions the performance characteristics of the QCL, which will be reported, exceeded that of a device mounted in a mechanical cryocooler.

Alkaline electrochemical cells and method of making

NASA Technical Reports Server (NTRS)

Hoyt, H. E.; Pfluger, H. L. (Inventor)

1970-01-01

Equilibrated cellulose ether membranes of increased electrolytic conductivity for use as separators in concentrated alkaline electrochemical cells are investigated. The method of making such membranes by equilibration to the degree desired in an aqueous alkali solution mantained at a temperature below about 10 C is described.

A New Method of Estimating Atomic Charges by Electronegativity Equilibration.

ERIC Educational Resources Information Center

Smith, Derek W.

1990-01-01

Presented is a modification of Bratsch's prescription so that difficult problems are obviated while simple, familiar Pauling electronegativities are retained. Discussed are the equilibration of electronegativity in molecules, group electronegativities, coordination compounds and molecules with dative bonds, ions, and correlation with core…

Scattering of charge and spin excitations and equilibration of a one-dimensional Wigner crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matveev, K. A.; Andreev, A. V.; Klironomos, A. D.

2014-07-01

We study scattering of charge and spin excitations in a system of interacting electrons in one dimension. At low densities, electrons form a one-dimensional Wigner crystal. To a first approximation, the charge excitations are the phonons in the Wigner crystal, and the spin excitations are described by the Heisenberg model with nearest-neighbor exchange coupling. This model is integrable and thus incapable of describing some important phenomena, such as scattering of excitations off each other and the resulting equilibration of the system. We obtain the leading corrections to this model, including charge-spin coupling and the next-nearest-neighbor exchange in the spin subsystem.more » We apply the results to the problem of equilibration of the one-dimensional Wigner crystal and find that the leading contribution to the equilibration rate arises from scattering of spin excitations off each other. We discuss the implications of our results for the conductance of quantum wires at low electron densities« less

An improved technique for the 2H/1H analysis of urines from diabetic volunteers

USGS Publications Warehouse

Coplen, T.B.; Harper, I.T.

1994-01-01

The H2-H2O ambient-temperature equilibration technique for the determination of 2H/1H ratios in urinary waters from diabetic subjects provides improved accuracy over the conventional Zn reduction technique. The standard deviation, ~ 1-2???, is at least a factor of three better than that of the Zn reduction technique on urinary waters from diabetic volunteers. Experiments with pure water and solutions containing glucose, urea and albumen indicate that there is no measurable bias in the hydrogen equilibration technique.The H2-H2O ambient-temperature equilibration technique for the determination of 2H/1H ratios in urinary waters from diabetic subjects provides improved accuracy over the conventional Zn reduction technique. The standard deviation, approximately 1-2%, is at least a factor of three better than that of the Zn reduction technique on urinary waters from diabetic volunteers. Experiments with pure water and solutions containing glucose, urea and albumen indicate that there is no measurable bias in the hydrogen equilibration technique.

Diagenetic palaeotemperatures from aqueous fluid inclusions: re- equilibration of inclusions in carbonate cements by burial heating.

USGS Publications Warehouse

Burruss, R.C.

1987-01-01

Calculations based on the observed behaviour of inclusions in fluorite under external confining P allows prediction of the T and depths of burial necessary to initiate re-equilibration of aqueous inclusions in the common size range 40-4 mu m. Heating of 20-60oC over the initial trapping T may cause errors of 10-20oC in the homogenization T. This suggests that re-equilibration may cause aqueous inclusions in carbonates to yield a poor record of their low-T history, but a useful record of the maximum T experienced by the host rock. Previous work suggests that inclusions containing petroleum fluids will be less susceptible to re-equilibration.This and the following six abstracts represent papers presented at a joint meeting of the Applied Mineralogy Group of the Mineralogical Society and the Petroleum Group of the Geological Society held in Newcastle upon Tyne in April 1986.-R.A.H.

Modeling Hf-W Evolution for Earth, Moon and Mars in Grand Tack Accretion Simulations: The Isotopic Consequences of Rapid Accretion

NASA Astrophysics Data System (ADS)

Zube, N.; Nimmo, F.; Jacobson, S. A.; Fischer, R. A.

2017-12-01

Short-lived isotopes, such as the decay of lithophile 182Hf into siderophile 182W with a half-life of 9 My, can provide constraints on the timescales of planetary core formation and accretion. Classical accretion scenarios have produced Hf-W isotopic outcomes like those measured presently on the Earth [2,3]. We examine Grand Tack accretion simulations [4,5] and determine the mantle equilibration conditions necessary to produce the observed tungsten isotopic anomaly. Additionally, we follow Hf-W evolution for pairs of bodies that experience a last giant impact fitting the conditions of Earth's Moon-forming collision. In this way, we determine the likelihood of producing the observed almost indistinguishable W isotope anomalies of the Earth and Moon mantles [6]. We model Hf-W evolution for growing planets in 141 N-body simulations during late accretion in the Grand Tack scenario. For each case, we vary the equilibration factor during collisions—the fraction of impactor core that experiences re-equilibration with the entire target mantle—in steps ranging from none (cores merging) to complete equilibration. For Earth-like and Mars-like surviving planets, we find that cases with a high equilibration factor (k > 0.8) and an intermediate (2:1 - 4:1) ratio of initial embryo mass to planetesimal mass were most frequently able to approximate the observed W measurements for Earth and Mars. The equilibration factor required is more restrictive than the one found for classical accretion scenarios [2,3] and may not be consistent with fluid-dynamical predictions [7]. Moons made of impactor material from Earth's last giant impact are only able to result in an Earth-Moon pair having sufficiently similar W anomalies with a likelihood of 8% or less across all simulations. This indicates that a scenario where the Moon isotopically equilibrated with the Earth's mantle after the impact [8] may be required to explain the measured values. [1] Kleine et al. 2009 [2] Nimmo et al. 2010 [3] Rudge et al. 2010 [4] Walsh et al. 2009 [5] Jacobson et al. 2014 [6] Touboul et al., 2007 [7] Deguen et al. 2014 [8] Pahlevan and Stevenson 2007

Experimental evidence for the absence of iron isotope fractionation between metal and silicate liquids at 1 GPa and 1250-1300 °C and its cosmochemical consequences

NASA Astrophysics Data System (ADS)

Hin, Remco C.; Schmidt, Max W.; Bourdon, Bernard

2012-09-01

Iron isotope fractionation during metal-silicate differentiation has been proposed as a cause for differences in iron isotope compositions of chondrites, iron meteorites and the bulk silicate Earth. Stable isotope fractionation, however, rapidly decreases with increasing temperature. We have thus performed liquid metal-liquid silicate equilibration experiments at 1250-1300 °C and 1 GPa to address whether Fe isotope fractionation is resolvable at the lowest possible temperatures for magmatic metal-silicate differentiation. A centrifuging piston cylinder apparatus enabled quantitative metal-silicate segregation. Elemental tin or sulphur was used in the synthetic metal-oxide mixtures to lower the melting temperature of the metal. The analyses demonstrate that eight of the 10 experimental systems equilibrated in a closed isotopic system, as was assessed by varying run durations and starting Fe isotope compositions. Statistically significant iron isotope fractionation between quenched metals and silicates was absent in nine of the 10 experiments and all 10 experiments yield an average metal-silicate fractionation factor of 0.01 ± 0.04‰, independent of whether graphite or silica glass capsules were used. This implies that Fe isotopes do not fractionate during low pressure metal-silicate segregation under magmatic conditions. In large bodies such as the Earth, fractionation between metal and high pressure (>20 GPa) silicate phases may still be a possible process for equilibrium fractionation during metal-silicate differentiation. However, the 0.07 ± 0.02‰ heavier composition of bulk magmatic iron meteorites relative to the average of bulk ordinary/carbonaceous chondrites cannot result from equilibrium Fe isotope fractionation during core segregation. The up to 0.5‰ lighter sulphide than metal fraction in iron meteorites and in one ordinary chondrite can only be explained by fractionation during subsolidus processes.

Gas phase 1H NMR studies and kinetic modeling of dihydrogen isotope equilibration catalyzed by Ru-nanoparticles under normal conditions: dissociative vs. associative exchange.

PubMed

Limbach, Hans-Heinrich; Pery, Tal; Rothermel, Niels; Chaudret, Bruno; Gutmann, Torsten; Buntkowsky, Gerd

2018-04-25

The equilibration of H2, HD and D2 between the gas phase and surface hydrides of solid organic-ligand-stabilized Ru metal nanoparticles has been studied by gas phase 1H NMR spectroscopy using closed NMR tubes as batch reactors at room temperature and 800 mbar. When two different nanoparticle systems, Ru/PVP (PVP ≡ polyvinylpyrrolidone) and Ru/HDA (HDA ≡ hexadecylamine) were exposed to D2 gas, only the release of HD from the hydride containing surface could be detected in the initial stages of the reaction, but no H2. In the case of Ru/HDA also the reverse experiment was performed where surface deuterated nanoparticles were exposed to H2. In that case, the conversion of H2 into gaseous HD was detected. In order to analyze the experimental kinetic and spectroscopic data, we explored two different mechanisms taking into account potential kinetic and equilibrium H/D isotope effects. Firstly, we explored the dissociative exchange mechanism consisting of dissociative adsorption of dihydrogen, fast hydride surface diffusion and associative desorption of dihydrogen. It is shown that if D2 is the reaction partner, only H2 will be released in the beginning of the reaction, and HD only in later reaction stages. The second mechanism, dubbed here associative exchange consists of the binding of dihydrogen to Ru surface atoms, followed by a H-transfer to or by H-exchange with an adjacent hydride site, and finally of the associative desorption of dihydrogen. In that case, in the exchange with D2, only HD will be released in the beginning of the reaction. Our experimental results are not compatible with the dissociative exchange but can be explained in terms of the associative exchange. Whereas the former will dominate at low temperatures and pressures, the latter will prevail around room temperature and normal pressures where transition metal nanoparticles are generally used as reaction catalysts.

A potential new proxy for paleo-atmospheric pO2 from soil carbonate-hosted fluid inclusions applied to pristine Chinle soils from the Petrified Forest 1A core

NASA Astrophysics Data System (ADS)

Schaller, M. F.; Pettitt, E.; Knobbe, T.

2017-12-01

Proxies for the concentration of O2 in the ancient atmosphere are scarce. We have developed a potential new proxy for ancient atmospheric O2 content based on soil carbonate-hosted fluid inclusions. Soils are in continuous atmospheric communication, and relatively static equilibration between soil gas and atmospheric gas during formation, such that a predictable amount of atmosphere infiltrates a soil. This atmosphere is trapped by inclusions during carbonate precipitation. Here we show that carbonate hosted fluid inclusions are faithful recorders of soil gas concentrations and isotope ratios, and specifically that soil O2 partial pressures can be derived from the total gas contents of these inclusions. Using carbonate nodules from a span of depths in a modern vertisol near Dallas, TX, as a test case, we employ an online crushing technique to liberate gases from soil carbonates into a small custom-built quadrupole mass spectrometer where all gases are measured in real time. We quantify the total oxygen content of the gas using a matrix-matched calibration, and define each species as a partial pressure of the total gas released from the nodule. Atmospheric pO2 is very simply derived from the soil-nodule partial pressures by accounting for the static productivity of the soil (using a small correction based on the CO2 concentration). When corrected for aqueous solubility using Henry's Law, these soil-carbonate hosted gas results reveal soil O2 concentrations that are comparable to modern-day dry atmosphere. Armed with this achievement in modern soils, and as a test on the applicability of the approach to ancient samples, we successfully apply the new proxy to nodules from the Late Triassic Chinle formation from the Petrified Forest National Park Core, taken as part of the Colorado Plateau Coring Project. Analysis of soil O2 from soil gas monitoring wells paired with measurements from contemporaneous soil carbonate nodules is needed to precisely calibrate the new proxy.

Strain-Rate Dependence of Deformation-Twinning in Tantalum

NASA Astrophysics Data System (ADS)

Abeywardhana, Jayalath; Germann, Tim; Ravelo, Ramon

2017-06-01

Large-Scale molecular dynamics (MD) simulations are used to model quasi-isentropic compression and expansion (QIC) in tantalum crystals varying the rate of deformation between the range 108 -1012s-1 and compressive pressures up to 100 GPa. The atomic interactions were modeled employing an embedded-atom method (EAM) potential of Ta. Isentropic expansion was done employing samples initially compressed to pressures of 60 and 100 GPa followed by uniaxial and quasi-isentropically expansion to zero pressure. The effect of initial dislocation density on twinning was also examined by varying the initial defect density of the Ta samples (1010 -1012cm-2). At these high-strain rates, a threshold in strain-rate on deformation twining is observed. Under expansion or compression, deformation twinning increases with strain rate for strain-rates >109s-1 . Below this value, small fraction of twins nucleates but anneal out with time. Samples with lower fraction of twins equilibrate to defect states containing higher screw dislocation densities from those with initially higher twinning fractions. This work was supported by the Department of Energy under contract DE-AC52-06NA25396 and by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-12-1-0476.

ANALYSES OF FISH TISSUE BY VACUUM DISTILLATION/GAS CHROMATOGRAPHY/MASS SPECTROMETRY

EPA Science Inventory

The analyses of fish tissue using VD/GC/MS with surrogate-based matrix corrections is described. Techniques for equilibrating surrogate and analyte spikes with a tissue matrix are presented, and equilibrated spiked samples are used to document method performance. The removal of a...

Fabrication and Properties of a Metal-Insulator - Type Oxygen Sensor Using Lanthanum Trifluoride as the Sole Dielectric.

NASA Astrophysics Data System (ADS)

Mattingly, William Brashear, III

1995-01-01

Oxygen sensors were fabricated using a metal-insulator -semiconductor construction where the sole 'insulator' is a thin film of LaF_3, an ionic conductor. The typical oxide or nitride layers were eliminated producing a simple Pt/LaF_3/Si design. LaF_3 films, 200-300nm thick, were directly deposited on n-type Si(111) using a high temperature effusion cell in an ultra high vacuum MBE chamber. The film morphology could be controlled from polycrystalline to near single crystal epitaxy. Epitaxial films exhibited a single relaxed variant with the LaF _3 c-axis normal to the silicon surface and the in-plane LaF_3(10^ -10) parallel to Si(110). Polycrystalline films also showed a high degree of LaF_3 c-axis normal texture. Films doped with strontium were also produced. Polycrystalline films were more robust and fabricated into MIS (metal-insulator-semiconductor) capacitors. Capacitance voltage tests of the devices demonstrate nearly ideal MIS capacitor behavior. The flatband voltages were typically within 300mV of the calculated value. Bias challenge tests developed in the lab showed less than 70mV flatband voltage shift. The dielectric constant of undoped LaF_3 films measured close to 14. Doped films, rm Sr_{x}La_ {1-x}F_3 x =.06, showed a dielectric constant of 275, at 100kHz. Oxygen partial pressure tests were performed with mixtures of dry nitrogen and dry oxygen. Oxygen partial pressures were varied between 2.5 times 10^{-4} and 1.0 atmosphere. The steady state data are consistent with a Pt/LaF _3 interface adsorption mechanism, where the work function of the platinum gate metal is modulated. The mechanism is not a half-cell Nernst-type response. Langmiur isotherm fitted data indicate the response range for undoped devices is 0.3 V. Signal drift was less than 5 mV/day. The metal free-surface reactions and the dipole species at the Pt/LaF_3 interface are yet to be determined. Device kinetic studies show the time required for full equilibration after a step in oxygen partial pressure is 24 hours at 90^circC. Initial response kinetics to downward steps in oxygen show the activation energy of the process is 0.54 eV.

Prevention of chinosol absorption by rubber stoppers used to seal glass vials containing tuberculin PPD Mantoux solutions.

PubMed

Landi, S; Held, H R

1965-01-01

Chinosol (8-quinolinol sulfate), which is employed as an antimicrobial agent in tuberculin PPD solutions used for the Mantoux test, is known to disappear from these solutions after storage. It has been established that the loss of this preservative from tuberculin solutions dispensed in glass vials is caused by the rubber stoppers used to seal the vials. All the rubber stoppers tested absorbed Chinosol very readily.The nature of the binding of Chinosol by a rubber stopper is both chemical (irreversible) and physical (reversible). The capacity to bind Chinosol chemically was determined for 12 types of rubber stopper, and was found to vary from 0 to more than 25% by weight of the stopper. This phenomenon can be attributed mainly to metal ingredients in the stopper. The capacity of stoppers to bind Chinosol physically is expressed quantitatively by a partition coefficient. This was determined for 7 types of rubber stopper and found to be high when compared with the partition coefficients of other preservatives.We have shown that all stoppers presaturated in Chinosol can be equilibrated against a buffered solution containing 0.01% Chinosol. Equilibrated silicone, white, and red oxiglazed stoppers can be used satisfactorily for sealing multi-dose vials of tuberculin PPD containing 0.01% Chinosol.

Prevention of Chinosol absorption by rubber stoppers used to seal glass vials containing tuberculin PPD Mantoux solutions

PubMed Central

Landi, S.; Held, H. R.

1965-01-01

Chinosol (8-quinolinol sulfate), which is employed as an antimicrobial agent in tuberculin PPD solutions used for the Mantoux test, is known to disappear from these solutions after storage. It has been established that the loss of this preservative from tuberculin solutions dispensed in glass vials is caused by the rubber stoppers used to seal the vials. All the rubber stoppers tested absorbed Chinosol very readily. The nature of the binding of Chinosol by a rubber stopper is both chemical (irreversible) and physical (reversible). The capacity to bind Chinosol chemically was determined for 12 types of rubber stopper, and was found to vary from 0 to more than 25% by weight of the stopper. This phenomenon can be attributed mainly to metal ingredients in the stopper. The capacity of stoppers to bind Chinosol physically is expressed quantitatively by a partition coefficient. This was determined for 7 types of rubber stopper and found to be high when compared with the partition coefficients of other preservatives. We have shown that all stoppers presaturated in Chinosol can be equilibrated against a buffered solution containing 0.01% Chinosol. Equilibrated silicone, white, and red oxiglazed stoppers can be used satisfactorily for sealing multi-dose vials of tuberculin PPD containing 0.01% Chinosol. ImagesFIG. 2 PMID:5294923

Effector diversification within compartments of the Leptosphaeria maculans genome affected by repeat induced point mutations

USDA-ARS?s Scientific Manuscript database

The genome sequence of the phytopathogenic fungus Leptosphaeria maculans has been determined. It has a unique bipartite structure, divided between distinct GC-equilibrated and AT-rich regions (isochores), reminiscent of some plants and animals but not previously observed in fungi. The GC-equilibrate...

EVALUATION OF VAPOR EQUILIBRATION AND IMPACT OF PURGE VOLUME ON SOIL-GAS SAMPLING RESULTS

EPA Science Inventory

Sequential sampling was utilized at the Raymark Superfund site to evaluate attainment of vapor equilibration and the impact of purge volume on soil-gas sample results. A simple mass-balance equation indicates that removal of three to five internal volumes of a sample system shou...

Unshocked Equilibrated H Chondrites: A Common Low-Temperature Record from Fe-Mg Ordering in Orthopyroxene

NASA Astrophysics Data System (ADS)

Folco, L.; Mellini, M.; Pillinger, C. T.

1995-09-01

The study of the thermal metamorphism of ordinary chondrites through geothermometers can provide significant constraints on the parent body thermal models which remain controversial. We report here results from Fe-Mg ordering closure temperatures (Tc) of orthopyroxenes from eight unshocked equilibrated H-chondrites obtained by means of single crystal X-ray diffraction. The method is based on the fact that cation partitioning in orthopyroxene is sensitive to temperature [1], and makes use of the experimental calibration by Molin et al. [2]. The goal of the investigation is to check how petrographic types relate to cation ordering thermal records. Results: The orthopyroxenes show a very similar degree of Fe-Mg ordering (see Table 1.). The Tc's cluster within the 384+/-48 to 480+/-28 degrees C interval, and show no correlation with petrographic type. The lack of a correlation does not mean that the distribution is random, rather, it appears to be controlled in individual samples by the degree of equilibration. In fact, the higher the petrographic type, the more coherent the results of the grains from individual chondrites. The spread of Tc's in the least equilibrated chondrites could be either a memory of heterogeneous pre-metamorphic records related to individual chondrule histories, or an artefact due to crystal defects. Therefore (1) the thermal records, inferred from the Fe-Mg ordering, are nearly the same for all the equilibrated H-chondrites; (2) the most equilibrated chondrites record distinct Tc values within the larger common Tc range; (3) the spread of Tc in H4's maybe indicative of disequilibrium and merits further study. The closure temperature conveys information on the cooling rate close to its value, regardless of the temperature regimes when the ordering process started. Extrapolation to high temperatures can be made only if the cooling path is constrained. Since we have no data to establish the temperature when ordering began and to decide whether the cooling was linear, we have not attempted quantitative estimates of cooling rates. However we can say that as equilibrated H-chondrites carry similar Tc records, they cooled at similar rates through 380-480 degrees C. However, the k(sub)D's (i.e., the intracrystalline Fe-Mg distribution coefficient) range 0.029 to 0.054, suggesting that H-chondrites cooled in petrogenetic environments intermediate between those of volcanic [3] and granulitic rocks [3,4]. Conclusion: Our results provide the following constraints: (1) Equilibrated H-chondrites, regardless the petrographic type, were located in petrogenetic environments characterized by similar temperature-time conditions when cooling through 380-480 degrees C, and, in terms of terrestrial environments, intermediate between those of volcanic and granulitic facies. (2) Different petrographic types reflect distinct metamorphic thermal regimes. Thus, to account for constraint (1), petrographic type was determined at temperatures above the 380-480 degrees C interval. This implies that equilibrated H-chondrites were placed in different geological environments characterized by distinct temperature-time regimes when still above this temperature range. In the case of the least equilibrated chondrites, for which the two events could coincide. Acknowledgments: We thank EUROMET for providing us with the Frontier Mt. samples, and PNRA for supporting this study. References: [1] Saxena S. K. and Dal Negro A. (1983) Bull. Min ral., 106, 443-449. [2] Molin G. M. et al. (1991) EPSL, 105, 260-265. [3] Bertolo S. and Nimis P. (1993) EJM, 5, 707-719. [4] Tribaudino M. and Talarico F. (1992) EJM, 4, 453-463.

Fast analysis of doping agents in urine by ultra-high-pressure liquid chromatography-quadrupole time-of-flight mass spectrometry I. Screening analysis.

PubMed

Badoud, F; Grata, E; Perrenoud, L; Avois, L; Saugy, M; Rudaz, S; Veuthey, J-L

2009-05-15

The general strategy to perform anti-doping analyses of urine samples starts with the screening for a wide range of compounds. This step should be fast, generic and able to detect any sample that may contain a prohibited substance while avoiding false negatives and reducing false positive results. The experiments presented in this work were based on ultra-high-pressure liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry. Thanks to the high sensitivity of the method, urine samples could be diluted 2-fold prior to injection. One hundred and three forbidden substances from various classes (such as stimulants, diuretics, narcotics, anti-estrogens) were analysed on a C(18) reversed-phase column in two gradients of 9min (including two 3min equilibration periods) for positive and negative electrospray ionisation and detected in the MS full scan mode. The automatic identification of analytes was based on retention time and mass accuracy, with an automated tool for peak picking. The method was validated according to the International Standard for Laboratories described in the World Anti-Doping Code and was selective enough to comply with the World Anti-Doping Agency recommendations. In addition, the matrix effect on MS response was measured on all investigated analytes spiked in urine samples. The limits of detection ranged from 1 to 500ng/mL, allowing the identification of all tested compounds in urine. When a sample was reported positive during the screening, a fast additional pre-confirmatory step was performed to reduce the number of confirmatory analyses.

Effect of Steam Deactivation Severity of ZSM-5 Additives on LPG Olefins Production in the FCC Process.

PubMed

Gusev, Andrey A; Psarras, Antonios C; Triantafyllidis, Konstantinos S; Lappas, Angelos A; Diddams, Paul A

2017-10-21

ZSM-5-containing catalytic additives are widely used in oil refineries to boost light olefin production and improve gasoline octanes in the Fluid Catalytic Cracking (FCC) process. Under the hydrothermal conditions present in the FCC regenerator (typically >700 °C and >8% steam), FCC catalysts and additives are subject to deactivation. Zeolites (e.g., Rare Earth USY in the base catalyst and ZSM-5 in Olefins boosting additives) are prone to dealumination and partial structural collapse, thereby losing activity, micropore surface area, and undergoing changes in selectivity. Fresh catalyst and additives are added at appropriate respective levels to the FCC unit on a daily basis to maintain overall targeted steady-state (equilibrated) activity and selectivity. To mimic this process under accelerated laboratory conditions, a commercial P/ZSM-5 additive was hydrothermally equilibrated via a steaming process at two temperatures: 788 °C and 815 °C to simulate moderate and more severe equilibration industrial conditions, respectively. n -Dodecane was used as probe molecule and feed for micro-activity cracking testing at 560 °C to determine the activity and product selectivity of fresh and equilibrated P-doped ZSM-5 additives. The fresh/calcined P/ZSM-5 additive was very active in C 12 cracking while steaming limited its activity, i.e., at catalyst-to-feed (C/F) ratio of 1, about 70% and 30% conversion was obtained with the fresh and steamed additives, respectively. A greater activity drop was observed upon increasing the hydrothermal deactivation severity due to gradual decrease of total acidity and microporosity of the additives. However, this change in severity did not result in any selectivity changes for the LPG (liquefied petroleum gas) olefins as the nature (Brønsted-to-Lewis ratio) of the acid/active sites was not significantly altered upon steaming. Steam deactivation of ZSM-5 had also no significant effect on aromatics formation which was enhanced at higher conversion levels. Coke remained low with both fresh and steam-deactivated P/ZSM-5 additives.

Experimental considerations in metal mobilization from soil by chelating ligands: The influence of soil-solution ratio and pre-equilibration - A case study on Fe acquisition by phytosiderophores.

PubMed

Schenkeveld, W D C; Kimber, R L; Walter, M; Oburger, E; Puschenreiter, M; Kraemer, S M

2017-02-01

The efficiency of chelating ligands in mobilizing metals from soils and sediments is generally examined under conditions remote from those under which they are exuded or applied in the field. This may lead to incorrect estimations of the mobilizing efficiency. The aim of this study was to establish the influence of the soil solution ratio (SSR) and pre-equilibration with electrolyte solution on metal mobilization and metal displacement. For this purpose a series of interaction experiments with a calcareous clay soil and a biogenic chelating agent, the phytosiderophore 2'-deoxymugineic acid (DMA) were carried out. For a fixed ligand concentration, the SSR had a strong influence on metal mobilization and displacement. Metal complexation was faster at higher SSR. Reactive pools of metals that were predominantly mobilized at SSR 6 (in this case Cu), became depleted at SSR 0.1, whereas metals that were marginally mobilized at SSR 6, were dominantly mobilized at SSR 0.1 (in this case Fe), because of large soil reactive pools. For a fixed "amount of ligand"-to-"amount of soil"-ratio, metal complexation scaled linearly with the SSR. The efficiency of ligands in mobilizing metals under field conditions can be predicted with batch experiments, as long as the ligand-to-soil-ratio is matched. In most previously reported studies this criterion was not met. Equivalent metal-complex concentrations under field conditions can be back-calculated using adsorption isotherms for the respective metal-complexes. Drying and dry storage created labile pools of Fe, Cu and Zn, which were rapidly mobilized upon addition of DMA solution to dry soil. Pre-equilibration decreased these labile pools, leading to smaller concentrations of these metals during initial mobilization, but did not reduce the lag time between ligand addition and onset of microbial degradation of the metal-complexes. Hence SSR and pre-equilibration should be carefully considered when testing the metal mobilizing efficiency of chelating ligands. Copyright © 2016. Published by Elsevier B.V.

Influence of Multidimensionality on Convergence of Sampling in Protein Simulation

NASA Astrophysics Data System (ADS)

Metsugi, Shoichi

2005-06-01

We study the problem of convergence of sampling in protein simulation originating in the multidimensionality of protein’s conformational space. Since several important physical quantities are given by second moments of dynamical variables, we attempt to obtain the time of simulation necessary for their sufficient convergence. We perform a molecular dynamics simulation of a protein and the subsequent principal component (PC) analysis as a function of simulation time T. As T increases, PC vectors with smaller amplitude of variations are identified and their amplitudes are equilibrated before identifying and equilibrating vectors with larger amplitude of variations. This sequential identification and equilibration mechanism makes protein simulation a useful method although it has an intrinsic multidimensional nature.

QCD matter thermalization at the RHIC and the LHC

NASA Astrophysics Data System (ADS)

Xu, Zhe; Cheng, Luan; El, Andrej; Gallmeister, Kai; Greiner, Carsten

2009-06-01

Employing the perturbative QCD inspired parton cascade, we investigate kinetic and chemical equilibration of the partonic matter created in central heavy ion collisions at RHIC and LHC energies. Two types of initial conditions are chosen. One is generated by the model of wounded nucleons using the PYTHIA event generator and Glauber geometry. Another is considered as a color glass condensate. We show that kinetic equilibration is almost independent of the chosen initial conditions, whereas there is a sensitive dependence for chemical equilibration. The time scale of thermalization lies between 1 and 1.5 fm/c. The final parton transverse energy obtained from BAMPS calculations is compared with the RHIC data and is estimated for the LHC energy.

Orthodontic management by functional activator treatment: a case report.

PubMed

Aprile, Giuseppe; Ortu, Eleonora; Cattaneo, Ruggero; Pietropaoli, Davide; Giannoni, Mario; Monaco, Annalisa

2017-12-02

Managing orthodontic treatment is often very difficult for the orthodontist. Many devices are used during the orthopedic phase of orthodontic treatment, always with different functions. We describe a case of orthodontic management treated with the Equilibrator O.S.A. device (equilibrator designed by Ovidi, Santi, and Aprile for Eptamed SRL; Cesena, Italy; www.eptamed.com ). A healthy 10-year-old white boy presented with a skeletal class II, division 1 malocclusion, molar class II, exhibiting an overjet of 7 mm prior to treatment. For treatment, we only used the Equilibrator O.S.A. device. We successfully treated an orthopedic/orthodontic case with a particular device that we describe here.

Radon as a tracer of biogenic gas equilibration and transport from methane-saturated sediments

NASA Technical Reports Server (NTRS)

Martens, Christopher S.; Chanton, Jeffrey P.

1989-01-01

Data on Rn-222 activity in methane-rich gas bubbles from anoxic coastal sediments of Cape Lookout Bight, North Carolina, were used to determine gas equilibration with pore waters and the rates of ebullitive stripping and transport of gases to overlying waters and the atmosphere. Results showed that, during summer months, the bubble ebullition process strips and transports 1.9-4.8 percent/day of the standing crop of radon (and, by inference, other gases equilibrated with gas bubbles) in surface sediments of Cape Lookout Bight to the troposphere. Thus, the ebullitive mode of gas transport represents an effective mechanism for delivering reduced biogenic gases directly to the atmosphere.

Improvements in the gaseous hydrogen-water equilibration technique for hydrogen isotope ratio analysis

USGS Publications Warehouse

Coplen, T.B.; Wildman, J.D.; Chen, J.

1991-01-01

Improved precision in the H2-H2O equilibration method for ??D analysis has been achieved in an automated system. Reduction in 1-?? standard deviation of a single mass-spectrometer analysis to 1.3??? is achieved by (1) bonding catalyst to glass rods and assigning use to specific equilibration chambers to monitor performance of catalyst, (2) improving the apparatus design, and (3) reducing the H3+ contribution of the mass-spectrometer ion source. For replicate analysis of a water sample, the standard deviation improved to 0.8???. H2S-bearing samples and samples as small as 0.1 mL can be analyzed routinely with this method.

Acidification of rabbit corneal endothelium during contact lens wear in vitro.

PubMed

Giasson, C; Bonanno, J A

1995-04-01

Contact lens wear causes significant epithelial and stromal acidosis. In this study, we tested whether lens wear can cause endothelial acidosis as well. Rabbit corneas were isolated and perfused in vitro. The endothelial intracellular pH (pHi) was measured with a pH sensitive fluorescent probe (BCECF). Three conditions were examined: 1) Polymethylmethacrylate (PMMA) and rigid gas-permeable (RGP) contact lens wear using a range of oxygen transmissibility (Dk/L) from 0 to 121, 2) epithelial hypoxia produced by exposure to oligomycin/sodium azide solution or epithelial perfusion with 100% N2 equilibrated Ringer's solution, and 3) epithelial exposure to Ringer's equilibrated with 5% CO2, balance air. PMMA and RGP contact lens wear acidified endothelial cells by 0.23 +/- 0.01 (n = 23) and 0.11 +/- 0.01 pH units (n = 23), respectively, within twenty min of lens insertion. Epithelial hypoxia, induced by sodium azide and oligomycin, reversibly acidified the endothelium by 0.04 +/- 0.01 pH units (n = 4). However, epithelial hypoxia induced by perfusion with 100% N2 equilibrated Ringer's did not have a significant effect on endothelial pHi. Introduction of 5% CO2 to the epithelium, acidified the endothelium by 0.15 +/- 0.02 pH units (n = 7) within 10 min. We conclude that contact lens wear can significantly acidify corneal endothelial cells. The endothelial pHi change is caused almost exclusively by a build up of CO2 behind the lens; hypoxia having very little contribution. As expected, RGP contact lenses induced less endothelial acidosis than PMMA controls.

Metric anisotropies and emergent anisotropic hydrodynamics

NASA Astrophysics Data System (ADS)

Dash, Ashutosh; Jaiswal, Amaresh

2018-05-01

Expansion of a locally equilibrated fluid is considered in an anisotropic space-time given by the Bianchi type-I metric. Starting from the isotropic equilibrium phase-space distribution function in the local rest frame, we obtain expressions for components of the energy-momentum tensor and conserved current, such as number density, energy density, and pressure components. In the case of an axissymmetric Bianchi type-I metric, we show that they are identical to those obtained within the setup of anisotropic hydrodynamics. We further consider the case in which the Bianchi type-I metric is a vacuum solution of the Einstein equation: the Kasner metric. For the axissymmetric Kasner metric, we discuss the implications of our results in the context of anisotropic hydrodynamics.

Genesis of recent silicic magmatism in the Medicine Lake Highland, California - Evidence from cognate inclusions found at Little Glass Mountain

NASA Technical Reports Server (NTRS)

Mertzman, S. A.; Williams, R. J.

1981-01-01

Sparse, granular inclusions of early-formed minerals found within the Little Glass Mountain rhyolite flows in northern California are shown to provide a means of characterizing the physical conditions, at depth, beneath the Medicine Lake Highland during the latest phase of volcanic activity. Mineral compositions, in combination with thermodynamic calculations and experiments, suggest crystalization at a pressure of 5,200 bars within a 966-836 C temperature range; implying that mineral segregation and equilibration occurred at a depth of 15-18 km beneath the surface. In addition, mass balance calculations indicate that the Medicine Lake flow is a close approximation to the parental magma for the latest silicic lavas.

The equilibrated state of freezing as a basis for distinguishing lethal stresses of freezing in plants

USDA-ARS?s Scientific Manuscript database

A model for coordination of stresses that limit winterhardiness in plants based on the thermodynamic equilibrated state of freezing and melting provides a rational basis for distinction of freeze-induced energies which can stress and injure living organisms in various ways. The departure from equili...

Recycled Crust in the Mantle: Is High-Ni Olivine the Smoking Gun or a Red Herring?

NASA Astrophysics Data System (ADS)

Li, C.; Ripley, E. M.

2008-12-01

It is widely accepted that small amounts of recycled crustal components are present in some mantle-derived mafic and ultramafic magmas. This concept is supported by many isotopic and trace element studies of basalts, picrites and komatiites in the last 30 years. Recently Sobolev et al. [1,2] used olivine compositions such as Ni content and Mn/Fe ratio to demonstrate that the amounts of the recycled crustal component (i.e. pyroxenite) in these mantle-derived melts are much larger than previously appreciated. Their calculations show that the pyroxenite-derived component varies mostly between 40 and 80% for Hawaiian shield basalts and Siberian flood basalts, and mostly between 10 and 40% for mid-ocean ridge basalts and Archean komatiities. However, a critical test using olivine-liquid Mg-Fe equilibrium that was overlooked by Sobolev et al. [1,2] reveals that mixing of the two end-members (pyroxenite-derived and peridotite-derived melts) that were used in their models cannot generate the parental melts for the above natural samples. Such a discrepancy prompts us to reexamine the conventional view of a peridotite-dominant source for the Hawaiian shield basalts. This hypothesis has been criticized recently by many people because the contents of Ni in olivine phenocrysts in the basalts are significantly higher than mantle olivines in associated peridotite xenoliths and because total pressure has little effect on olivine-liquid Ni partition coefficient (DNi). What has not been generally considered is that the depth of olivine crystallization/equilibration has a negative effect on olivine Ni content because DNi is negatively correlated with melt temperature which decreases during adiabatic ascent. To evaluate such an effect quantitatively we have used all available experimental results of Ni partitioning between olivine and liquid to construct a robust empirical equation for DNi based on melt composition and temperature. The results of our calculations indicate that the contrasting Ni contents between mantle olivines and olivine phenocrysts in the Hawaiian shield basalts can be explained by variation in their crystallization/equilibration temperatures at different depths. [1] Sobolev et al. (2005) Nature 434, 590-597. [2] Sobolev et al. (2007) Science 316, 412-417.

Selective Equilibration of Spin-Polarized Quantum Hall Edge States in Graphene

NASA Astrophysics Data System (ADS)

Amet, F.; Williams, J. R.; Watanabe, K.; Taniguchi, T.; Goldhaber-Gordon, D.

2014-05-01

We report on transport measurements of dual-gated, single-layer graphene devices in the quantum Hall regime, allowing for independent control of the filling factors in adjoining regions. Progress in device quality allows us to study scattering between edge states when the fourfold degeneracy of the Landau level is lifted by electron correlations, causing edge states to be spin and/or valley polarized. In this new regime, we observe a dramatic departure from the equilibration seen in more disordered devices: edge states with opposite spins propagate without mixing. As a result, the degree of equilibration inferred from transport can reveal the spin polarization of the ground state at each filling factor. In particular, the first Landau level is shown to be spin polarized at half filling, providing an independent confirmation of a conclusion of Young et al. [Nat. Phys. 8, 550 (2012)]. The conductance in the bipolar regime is strongly suppressed, indicating that copropagating edge states, even with the same spin, do not equilibrate along PN interfaces. We attribute this behavior to the formation of an insulating ν =0 stripe at the PN interface.

Petrogenesis of Miller Range 07273, a new type of anomalous melt breccia: Implications for impact effects on the H chondrite asteroid

NASA Astrophysics Data System (ADS)

Ruzicka, Alex M.; Hutson, Melinda; Friedrich, Jon M.; Rivers, Mark L.; Weisberg, Michael K.; Ebel, Denton S.; Ziegler, Karen; Rumble, Douglas; Dolan, Alyssa A.

2017-09-01

Miller Range 07273 is a chondritic melt breccia that contains clasts of equilibrated ordinary chondrite set in a fine-grained (<5 μm), largely crystalline, igneous matrix. Data indicate that MIL was derived from the H chondrite parent asteroid, although it has an oxygen isotope composition that approaches but falls outside of the established H group. MIL also is distinctive in having low porosity, cone-like shapes for coarse metal grains, unusual internal textures and compositions for coarse metal, a matrix composed chiefly of clinoenstatite and omphacitic pigeonite, and troilite veining most common in coarse olivine and orthopyroxene. These features can be explained by a model involving impact into a porous target that produced brief but intense heating at high pressure, a sudden pressure drop, and a slower drop in temperature. Olivine and orthopyroxene in chondrule clasts were the least melted and the most deformed, whereas matrix and troilite melted completely and crystallized to nearly strain-free minerals. Coarse metal was largely but incompletely liquefied, and matrix silicates formed by the breakdown during melting of albitic feldspar and some olivine to form pyroxene at high pressure (>3 GPa, possibly to 15-19 GPa) and temperature (>1350 °C, possibly to ≥2000 °C). The higher pressures and temperatures would have involved back-reaction of high-pressure polymorphs to pyroxene and olivine upon cooling. Silicates outside of melt matrix have compositions that were relatively unchanged owing to brief heating duration.

Nitric oxide (NO) in normal and hypoxic vascular regulation of the spiny dogfish, Squalus acanthias.

PubMed

Swenson, Kai E; Eveland, Randy L; Gladwin, Mark T; Swenson, Erik R

2005-02-01

Nitric oxide (NO) is a potent vasodilator in terrestrial vertebrates, but whether vascular endothelial-derived NO plays a role in vascular regulation in fish remains controversial. To explore this issue, a study was made of spiny dogfish sharks (Squalus acanthias) in normoxia and acute hypoxia (60 min exposure to seawater equilibrated with 3% oxygen) with various agents known to alter NO metabolism or availability. In normoxia, nitroprusside (a NO donor) reduced blood pressure by 20%, establishing that vascular smooth muscle responds to NO. L-arginine, the substrate for NO synthase, had no hemodynamic effect. Acetylcholine, which stimulates endothelial NO and prostaglandin production in mammals, reduced blood pressure, but also caused marked bradycardia. L-NAME, an inhibitor of all NO synthases, caused a small 10% rise in blood pressure, but cell-free hemoglobin (a potent NO scavenger and hypertensive agent in mammals) had no effect. Acute hypoxia caused a 15% fall in blood pressure, which was blocked by L-NAME and cell-free hemoglobin. Serum nitrite, a marker of NO production, rose with hypoxia, but not with L-NAME. Results suggest that NO is not an endothelial-derived vasodilator in the normoxic elasmobranch. The hypertensive effect of L-NAME may represent inhibition of NO production in the CNS and nerves regulating blood pressure. In acute hypoxia, there is a rapid up-regulation of vascular NO production that appears to be responsible for hypoxic vasodilation.

C Diffusion in Fe: Isotope Effects and Other Complexities

NASA Astrophysics Data System (ADS)

Watson, E. B.; Muller, T.; Trail, D.; Van Orman, J. A.; Papineau, D.

2011-12-01

Carbon is a minor but significant component of iron meteorites, and probably also of planetary cores, including that of Earth. Given the dynamical nature of core-forming processes, C diffusion in the metal phase may play a role in C equilibration between Fe-Ni metal and silicate, carbide or oxide at some stage. Despite its relevance to steel-making, C diffusion in Fe is not well characterized over the range of conditions of interest in planetary bodies, and the likelihood of an isotope mass effect on C diffusion has not been explored. The prospect of incomplete diffusive equilibration of carbon in Fe-Ni raises the possibility that carbon isotopes might be fractionated by diffusion during core formation and evolution-perhaps to an extent that could affect the C isotope ratio of the bulk silicate Earth. Here we report results of preliminary experiments addressing the isotopic mass effect on C diffusion in Fe. Initial low-pressure experiments were conducted by placing a layer of ^{13}C-enriched graphite ( 20% ^{13}C) at the end of a high-purity, polycrystalline Fe cylinder in a silica glass container. These diffusion couples were run in a piston-cylinder apparatus at 1.5 GPa and 1000-1100^{o}C for several hours, and the resulting C-uptake profiles in the Fe cylinders were measured by EPMA and SIMS. In traverses moving away from the original C-Fe interface, total carbon decreases monotonically and becomes significantly lighter, indicating that ^{12}C diffuses faster than ^{13}C. Preliminary estimates of β in the relative isotope diffusivity relation D_{1}/D_{2} = [M_{2}/M_{1}]^{β} (where D is diffusivity and M is mass of isotopes 1 and 2) suggest values as high as 0.5, corresponding to predictions for gaseous diffusion. Isotope mass effects approaching this magnitude have been observed previously for diffusion in metals, and are expected to be highest for interstitial diffusion. Such a high β value will lead to major C isotope fractionation in some partial equilibration scenarios in planets and meteorite parent bodies. Caution is warranted at this point, however, because D_{carbon} is sensitive to carbon concentration, complicating quantification of the isotope effect.

Quantitation of 24-Hour Moisturization by Electrical Measurements of Skin Hydration.

PubMed

Wickett, R Randall; Damjanovic, Bronson

The purpose of this study was to quantify the effects of several moisturizers on hydration of the stratum corneum by measuring their effect on electrical conductance over a 24-hour period. Double-blind, randomized controlled trial. Twenty-five healthy female volunteers aged 18 to 65 years with dry skin on the lower legs and no other known dermatologic pathology participated in the study. Additional exclusion criteria were pregnant or taking anti-inflammatory steroids. The study was carried out in a clinical research facility in Winnipeg, Manitoba, Canada. Subjects underwent a 3-day conditioning period using a natural soap bar on the lower legs and no application of moisturizer to the skin. Participants then came to the test site and equilibrated for at least 30 minutes under controlled conditions of temperature and humidity. After baseline hydration measurements on test sites on the lower legs of each subject, a single application of each of 5 test products at a dose of 2 mg/cm was made. Skin hydration was assessed by electrical conductance measurements with a specialized probe. The probe was briefly placed on the skin surface with light pressure, and the measurement recorded in units of microsiemens (μS). Conductance was measured at 2, 4, 6, 8, and 24 hours after product applications. Although all but 1 of the test products increased conductance at 2 hours, only 2 moisturizers containing high levels of glycerin (products C and E) maintained increased conductance relative to baseline at 24 hours, +37.8 (P < .001) and +103.5 (P < .001), respectively. Moisturizers containing high levels of glycerin can provide a measurable moisturization benefit as determined by skin conductance for at least 24 hours after a single application.

Illinois basin coal fly ashes. 2. Equilibria relationships and qualitative modeling of ash-water reactions

USGS Publications Warehouse

Roy, W.R.; Griffin, R.A.

1984-01-01

Alkaline and acidic Illinois Basin coal fly ash samples were each mixed with deionized water and equilibrated for about 140 days to simulate ash ponding environments. Common to both equilibrated solutions, anhydrite solubility dominated Ca2+ activities, and Al3+ activities were in equilibrium with both matrix mullite and insoluble aluminum hydroxide phases. Aqueous silica activities were controlled by both mullite and matrix silicates. The pH of the extract of the acidic fly ash was 4.1 after 24 h but increased to a pH value of 6.4 as the H2SO4, assumed to be adsorbed to the particle surfaces, was exhausted by the dissolution of matrix iron oxides and aluminosilicates. The activities of aqueous Al3+ and iron, initially at high levels during the early stages of equilibration, decreased to below analytical detection limits as the result of the formation of insoluble Fe and Al hydroxide phases. The pH of the extract of the alkaline fly ash remained above a pH value of 10 during the entire equilibration interval as a result of the hydrolysis of matrix oxides. As with the acidic system, Al3+ activities were controlled by amorphous aluminum hydroxide phases that began to form after about 7 days of equilibration. The proposed mechanisms and their interrelations are discussed in addition to the solubility diagrams used to deduce these relationships. ?? 1984 American Chemical Society.

Evaluation of headspace equilibration methods for quantifying greenhouse gases in groundwater.

PubMed

Jahangir, M M R; Johnston, P; Khalil, M I; Grant, J; Somers, C; Richards, K G

2012-11-30

The objective of the study was to evaluate the different headspace equilibration methods for the quantification of dissolved greenhouse gases in groundwater. Groundwater samples were collected from wells with contrasting hydrogeochemical properties and degassed using the headspace equilibration method. One hundred samples from each well were randomly selected, treatments were applied and headspace gases analysed by gas chromatography. Headspace equilibration treatments varied helium (He):water ratio, shaking time and standing time. Mean groundwater N(2)O, CO(2) and CH(4) concentrations were 0.024 mg N L(-1), 13.71 mg C L(-1) and 1.63 μg C L(-1), respectively. All treatments were found to significantly influence dissolved gas concentrations. Considerable differences in the optimal He:water ratio and standing time were observed between the three gases. For N(2)O, CO(2) and CH(4) the optimum operating points for He:water ratio was 4.4:1, 3:1 and 3.4:1; shaking time was 13, 12 and 13 min; and standing time was 63, 17 and 108 min, respectively. The headspace equilibration method needs to be harmonised to ensure comparability between studies. The experiment reveals that He:water ratio 3:1 and shaking time 13 min give better estimation of dissolved gases than any lower or higher ratios and shaking times. The standing time 63, 17 and 108 min should be applied for N(2)O, CO(2) and CH(4), respectively. Copyright © 2012. Published by Elsevier Ltd.

Group II Xenoliths from Lunar Crater Volcanic Field, Central Nevada: Evidence for a Kinked Geotherm

NASA Astrophysics Data System (ADS)

Roden, M.; Mosely, J.; Norris, J.

2015-12-01

Group II xenoliths associated with the 140 Ka Easy Chair Crater, Lunar Crater volcanic field, NV, consist of amphibole rich-inclusions including amphibolites, pyroxenites, and gabbros. Abundant minerals in these inclusions are kaersutite, aluminous (7.3-9.7 wt% Al2O3), calcic clinopyroxene, primarily diopside, and olivine (Mg# 69-73) with accessory spinel, sulfide and apatite. Although most apatites are fluor-hydroxyapatite solid solutions, one xenolith contains Cl- and OH-rich apatite suggesting that Cl may have been an important constituent in the parent magma(s) . The xenoliths show abundant evidence for equilibration at relatively low temperatures including amphibole and orthopyroxene exsolution in clinopyroxene, and granules of magnetite in hercynite hosts. If latter texture is due to exsolution, then this particular Group II xenolith equilibrated at temperatures near or below 500oC or at a depth of about 15 km along a conductive geotherm. It may be that all the Group II xenoliths equilibrated at low temperatures given the abundant exsolution textures although Fe-Mg exchange relations suggest equilibration at temperatures in excess of 800oC. Low equilibration temperatures are in conflict with the unusually high equilibration temperatures, >1200oC (Smith, 2000) displayed by Group I xenoliths from this same volcanic field. Taken at face value, the geothermometric results indicate unusually high temperatures in the upper mantle, normal temperatures in the crust and the possibility of a kinked geotherm in the region. Curiously the LCVF lies in an area of "normal" heat flow, south of the Battle Mountain area of high heat flow but the number of heat flow measurements in the Lunar Crater area is very low (Humphreys et al., 2003; Sass, 2005). References: Humphreys et al., 2003, Int. Geol. Rev. 45: 575; Sass et al., 2005, http://pubs.usgs.gov/of/2005/1207/; Smith, 2000, JGR 105: 16769.

Measurement of mean circulatory filling pressure and vascular compliance in domestic pigs.

PubMed

Ogilvie, R I; Zborowska-Sluis, D; Tenaschuk, B

1990-06-01

To measure mean circulatory filling pressure (Pmcf), a balloon was placed in the right atrium of seven pentobarbital sodium-anesthetized open-chest pigs for transient occlusion of flow combined with mechanical transfer of blood from the arterial to the venous circulation. Equilibration occurred within 6-8 s at a pressure at 12.3 +/- 0.3 (SE) mmHg after a 2.9 +/- 0.2 ml/kg transfer of blood. In another group of pentobarbital sodium-anesthetized closed-chest pigs, acetylcholine (ACh) was used to induce cardiac arrest. The Pmcf was 11.6 +/- 1.0 mmHg in the 7:17 pigs that arrested for 6-8 s. In four isoflurane-anesthetized closed-chest pigs, the Pmcf was 12.0 +/- 1.0 mmHg after terminal cardiac arrest induced by KCl. The pressure gradient for venous return [Pmcf--right atrial pressure (Pra)] averaged 5.9 +/- 0.2 mmHg. Total vascular compliance estimated from plots of Pmcf at base line, 5, and 10 ml/kg increases in circulating volume was 2.1 +/- 0.3 and 3.5 +/- 0.9 ml.kg-1.mmHg-1 in the balloon and ACh groups, respectively compared with 2.8 +/- 0.4 ml.kg-1.mmHg-1 using a volume infusion-withdrawal method without circulatory arrest. The use of ACh for the estimate of Pmcf in the pig is not recommended because of failure to consistently induce circulatory arrest and probable failure to achieve sufficient equilibrium of vascular pressures 6-8 s postarrest when it occurs.

The use of the oesophageal Doppler in perioperative medicine: new opportunities in research and clinical practice.

PubMed

Pinto, Bernardo Bollen; Atlas, Glen; Geerts, Bart F; Bendjelid, Karim

2017-10-01

The oesophageal Doppler (OD) is a minimally invasive haemodynamic monitor used in the surgical theatre and the ICU. Using the OD, goal-directed therapy (GDT) has been shown to reduce perioperative complications in high-risk surgical patients. However, most GDT protocols currently in use are limited to stroke volume optimisation. In the present manuscript, we examine the conceptual models behind new OD-based measurements. These would provide the clinician with a comprehensive view of haemodynamic pathophysiology; including pre-load, contractility, and afterload. Specifically, volume status could be estimated using mean systemic filling pressure (MSFP), the pressure to which all intravascular pressures equilibrate during asystole. Using the OD, MSFP could be readily estimated by simultaneous measurements of aortic blood flow and arterial pressure with sequential manoeuvres of increasing airway pressure. This would result in subsequent reductions in cardiac output and arterial pressure and would allow for a linear extrapolation of a static MSFP value to a "zero flow" state. In addition, we also demonstrate that EF is proportional to mean blood flow velocity measured in the descending thoracic aorta with the OD. Furthermore, OD-derived indexes of blood flow velocity and acceleration, as well as force and kinetic energy, can be derived and used for continuous assessment of cardiac contractility at the bedside. Using OD-derived parameters, the different components of afterload: inertia, resistance and elastance, could also be individually determined. The integration of these additional haemodynamic parameters could assist the clinician in optimising and individualising haemodynamic performance in unstable patients.

The Precise Measurement of Vapor-Liquid Equilibrium Properties of the CO2/Isopentane Binary Mixture, and Fitted Parameters for a Helmholtz Energy Mixture Model

NASA Astrophysics Data System (ADS)

Miyamoto, H.; Shoji, Y.; Akasaka, R.; Lemmon, E. W.

2017-10-01

Natural working fluid mixtures, including combinations of CO2, hydrocarbons, water, and ammonia, are expected to have applications in energy conversion processes such as heat pumps and organic Rankine cycles. However, the available literature data, much of which were published between 1975 and 1992, do not incorporate the recommendations of the Guide to the Expression of Uncertainty in Measurement. Therefore, new and more reliable thermodynamic property measurements obtained with state-of-the-art technology are required. The goal of the present study was to obtain accurate vapor-liquid equilibrium (VLE) properties for complex mixtures based on two different gases with significant variations in their boiling points. Precise VLE data were measured with a recirculation-type apparatus with a 380 cm3 equilibration cell and two windows allowing observation of the phase behavior. This cell was equipped with recirculating and expansion loops that were immersed in temperature-controlled liquid and air baths, respectively. Following equilibration, the composition of the sample in each loop was ascertained by gas chromatography. VLE data were acquired for CO2/ethanol and CO2/isopentane binary mixtures within the temperature range from 300 K to 330 K and at pressures up to 7 MPa. These data were used to fit interaction parameters in a Helmholtz energy mixture model. Comparisons were made with the available literature data and values calculated by thermodynamic property models.

Water Saturation Relations and Their Diffusion-Limited Equilibration in Gas Shale: Implications for Gas Flow in Unconventional Reservoirs

NASA Astrophysics Data System (ADS)

Tokunaga, Tetsu K.; Shen, Weijun; Wan, Jiamin; Kim, Yongman; Cihan, Abdullah; Zhang, Yingqi; Finsterle, Stefan

2017-11-01

Large volumes of water are used for hydraulic fracturing of low permeability shale reservoirs to stimulate gas production, with most of the water remaining unrecovered and distributed in a poorly understood manner within stimulated regions. Because water partitioning into shale pores controls gas release, we measured the water saturation dependence on relative humidity (rh) and capillary pressure (Pc) for imbibition (adsorption) as well as drainage (desorption) on samples of Woodford Shale. Experiments and modeling of water vapor adsorption into shale laminae at rh = 0.31 demonstrated that long times are needed to characterize equilibrium in larger (5 mm thick) pieces of shales, and yielded effective diffusion coefficients from 9 × 10-9 to 3 × 10-8 m2 s-1, similar in magnitude to the literature values for typical low porosity and low permeability rocks. Most of the experiments, conducted at 50°C on crushed shale grains in order to facilitate rapid equilibration, showed significant saturation hysteresis, and that very large Pc (˜1 MPa) are required to drain the shales. These results quantify the severity of the water blocking problem, and suggest that gas production from unconventional reservoirs is largely associated with stimulated regions that have had little or no exposure to injected water. Gravity drainage of water from fractures residing above horizontal wells reconciles gas production in the presence of largely unrecovered injected water, and is discussed in the broader context of unsaturated flow in fractures.

Paradoxes of thermodynamics of swelling equilibria of polymers in liquids and vapors.

PubMed

Davankov, Vadim A; Pastukhov, Alexander V

2011-12-29

An automatic registration of the changing size of a single spherical microbead of a cross-linked polymer was applied for studying the swelling process of the bead by the sorption of vapors and/or liquids. Many representatives of all three basic types of polymeric networks, gel-type, hypercrosslinked, and macroporous, were examined. Only the first two display large volume changes and prove suitable for following the kinetics and extent of swelling by the above dilatometric technique. The results unambiguously prove that swelling of all polymeric networks in liquids is always higher than in corresponding saturated vapors (Schroeder's paradox). The general nature of this phenomenon implies that the absolute activity of any sorbate in its liquid form is always larger than in the form of its saturated vapor. Surprisingly, gels with any solvent contents, which fall into the broad range between the vapor-equilibrated and liquid-equilibrated extreme contents, retain their volumes constant in the saturated vapor atmosphere. This paradox of a wide range of gels swollen to a different extent and, nevertheless, standing in equilibrium with saturated vapor is explained by the specificity of the network polymers, namely, that the energy of the solvent-polymer interactions is easily compensated by the energy of remaining between-chain interactions at any solvent content in the above range. Therefore, the strain-free swollen gels do not generate enhanced vapor pressure, but neither display the ability to take up more sorbate from its vapor. © 2011 American Chemical Society

Slow equilibration of reversed-phase columns for the separation of ionized solutes.

PubMed

Marchand, D H; Williams, L A; Dolan, J W; Snyder, L R

2003-10-10

Reversed-phase columns that have been stored in buffer-free solvents can exhibit pronounced retention-time drift when buffered, low-pH mobile phases are used with ionized solutes. Whereas non-ionized compounds exhibit constant retention times within 20 min of the beginning of mobile phase flow, the retention of ionized compounds can continue to change (by 20% or more) for several hours. If mobile phase pH is changed from low to high and back again, an even longer time may be required before the column reaches equilibration at low pH. The speed of column equilibration for ionized solutes can vary significantly among different reversed-phase columns and is not affected by flow rate.

Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems

NASA Astrophysics Data System (ADS)

Gogolin, Christian; Eisert, Jens

2016-05-01

We review selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics. We cover topics such as equilibration and thermalisation in pure state statistical mechanics, the eigenstate thermalisation hypothesis, the equivalence of ensembles, non-equilibration dynamics following global and local quenches as well as ramps. We also address initial state independence, absence of thermalisation, and many-body localisation. We elucidate the role played by key concepts for these phenomena, such as Lieb-Robinson bounds, entanglement growth, typicality arguments, quantum maximum entropy principles and the generalised Gibbs ensembles, and quantum (non-)integrability. We put emphasis on rigorous approaches and present the most important results in a unified language.

Generic equilibration dynamics of planar defects in trapped atomic superfluids

DOE PAGES

Scherpelz, Peter; Padavić, Karmela; Murray, Andy; ...

2015-03-18

Here, we investigate equilibration processes shortly after sudden perturbations are applied to ultracold trapped superfluids. We show the similarity of phase imprinting and localized density depletion perturbations, both of which initially are found to produce “phase walls”. These planar defects are associated with a sharp gradient in the phase. Importantly they relax following a quite general sequence. Our studies, based on simulations of the complex time-dependent Ginzburg-Landau equation, address the challenge posed by these experiments: how a superfluid eventually eliminatesa spatially extended planar defect. The processes involved are necessarily more complex than equilibration involving simpler line vortices. An essential mechanismmore » form relaxation involves repeated formation and loss of vortex rings near the trap edge.« less

Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems.

PubMed

Gogolin, Christian; Eisert, Jens

2016-05-01

We review selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics. We cover topics such as equilibration and thermalisation in pure state statistical mechanics, the eigenstate thermalisation hypothesis, the equivalence of ensembles, non-equilibration dynamics following global and local quenches as well as ramps. We also address initial state independence, absence of thermalisation, and many-body localisation. We elucidate the role played by key concepts for these phenomena, such as Lieb-Robinson bounds, entanglement growth, typicality arguments, quantum maximum entropy principles and the generalised Gibbs ensembles, and quantum (non-)integrability. We put emphasis on rigorous approaches and present the most important results in a unified language.

An experimental study of amphibole stability in low-pressure granitic magmas and a revised Al-in-hornblende geobarometer

NASA Astrophysics Data System (ADS)

Mutch, E. J. F.; Blundy, J. D.; Tattitch, B. C.; Cooper, F. J.; Brooker, R. A.

2016-10-01

We report new experimental data on the composition of magmatic amphiboles synthesised from a variety of granite (sensu lato) bulk compositions at near-solidus temperatures and pressures of 0.8-10 kbar. The total aluminium content (Altot) of the synthetic calcic amphiboles varies systematically with pressure ( P), although the relationship is nonlinear at low pressures (<2.5 kbar). At higher pressures, the relationship resembles that of other experimental studies, which suggests of a general relationship between Altot and P that is relatively insensitive to bulk composition. We have developed a new Al-in-hornblende geobarometer that is applicable to granitic rocks with the low-variance mineral assemblage: amphibole + plagioclase (An15-80) + biotite + quartz + alkali feldspar + ilmenite/titanite + magnetite + apatite. Amphibole analyses should be taken from the rims of grains, in contact with plagioclase and in apparent textural equilibrium with the rest of the mineral assemblage at temperatures close to the haplogranite solidus (725 ± 75 °C), as determined from amphibole-plagioclase thermometry. Mean amphibole rim compositions that meet these criteria can then be used to calculate P (in kbar) from Altot (in atoms per formula unit, apfu) according to the expression: {it{P }}( {{kbar}} ) = 0.5 + 0.331( 8 ) × {{Al}}^{{tot}} + 0.995( 4 ) × ( {{{Al}}^{{tot}} } )2 This expression recovers equilibration pressures of our calibrant dataset, comprising both new and published experimental and natural data, to within ±16 % relative uncertainty. An uncertainty of 10 % relative for a typical Altot value of 1.5 apfu translates to an uncertainty in pressure estimate of 0.5 kbar, or 15 % relative. Thus the accuracy of the barometer expression is comparable to the precision with which near-solidus amphibole rim composition can be characterised.

WETTABILITY AND PREDICTION OF OIL RECOVERY FROM RESERVOIRS DEVELOPED WITH MODERN DRILLING AND COMPLETION FLUIDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jill S. Buckley; Norman R. Morrow

2003-10-01

In this report we focus on surface studies of the wetting effects of SBM components; three areas of research are covered. First we present results of tests of interfacial properties of some commercial emulsifiers that are routinely used in both oil-based and synthetic oil-based drilling fluids. These products fall into two main groups, based on their CMC and IFT trends with changing pH. All can alter the wetting of mica, but measurements vary widely depending on the details of exposure and observation protocols. Non-equilibrium effects appear to be responsible for these variations, with equilibrated fluids generally giving lower contact anglesmore » than those observed with fluids that have not been pre-equilibrated. Addition of small amounts of emulsifier can increase the tendency of a crude oil to alter wetting of mica surfaces. The effects of similar amounts of these emulsifiers can be detected in interfacial tension measurements. Next, we report on the preliminary results of a study of polyethoxylated amines of varying structures on the wetting of mica surfaces. Contact angles have been measured for unequilibrated and pre-equilibrated fluids. Reduction in contact angles was generally observed when the surfaces were washed with toluene after exposure to surfactant solutions. Atomic forces microscopy is also being used to observe the interactions between these surfactants and mica surfaces. Finally, we show the results of a study of asphaltene stability in the presence of synthetic base oils. Most of the base oils in current use are paraffinic or olefinic--the aromatic content is minimized for environmental reasons--and they destabilize asphaltenes. Tests with two crude oils show onset conditions for base oils that are comparable to n-heptane and n-pentadecane in terms of the solubility conditions at the onset. Two ester-based products, Petrofree and Petrofree LV, did not cause asphaltene flocculation in these tests. A meeting of the research groups from New Mexico Tech and the University of Wyoming, was held in Laramie on the 9th and 10th of October. All the members of the research teams presented updates on their progress and exchanged views on directions for the remainder of the project.« less

Pressure evolution equation for the particulate phase in inhomogeneous compressible disperse multiphase flows

NASA Astrophysics Data System (ADS)

Annamalai, Subramanian; Balachandar, S.; Sridharan, P.; Jackson, T. L.

2017-02-01

An analytical expression describing the unsteady pressure evolution of the dispersed phase driven by variations in the carrier phase is presented. In this article, the term "dispersed phase" represents rigid particles, droplets, or bubbles. Letting both the dispersed and continuous phases be inhomogeneous, unsteady, and compressible, the developed pressure equation describes the particle response and its eventual equilibration with that of the carrier fluid. The study involves impingement of a plane traveling wave of a given frequency and subsequent volume-averaged particle pressure calculation due to a single wave. The ambient or continuous fluid's pressure and density-weighted normal velocity are identified as the source terms governing the particle pressure. Analogous to the generalized Faxén theorem, which is applicable to the particle equation of motion, the pressure expression is also written in terms of the surface average of time-varying incoming flow properties. The surface average allows the current formulation to be generalized for any complex incident flow, including situations where the particle size is comparable to that of the incoming flow. Further, the particle pressure is also found to depend on the dispersed-to-continuous fluid density ratio and speed of sound ratio in addition to dynamic viscosities of both fluids. The model is applied to predict the unsteady pressure variation inside an aluminum particle subjected to normal shock waves. The results are compared against numerical simulations and found to be in good agreement. Furthermore, it is shown that, although the analysis is conducted in the limit of negligible flow Reynolds and Mach numbers, it can be used to compute the density and volume of the dispersed phase to reasonable accuracy. Finally, analogous to the pressure evolution expression, an equation describing the time-dependent particle radius is deduced and is shown to reduce to the Rayleigh-Plesset equation in the linear limit.

Impact of cryopreservation on bull () semen proteome.

PubMed

Westfalewicz, B; Dietrich, M A; Ciereszko, A

2015-11-01

Cryopreservation of bull spermatozoa is a well-established technique, allowing artificial insemination of cattle on a commercial scale. However, the extent of proteome changes in seminal plasma and spermatozoa during cryopreservation are not yet fully known. The objective of this study was to compare the proteomes of fresh, equilibrated, and cryopreserved bull semen (spermatozoa and seminal plasma) to establish the changes in semen proteins during the cryopreservation process. Semen was collected from 6 mature Holstein Friesian bulls. After sample processing, comparative analysis and identification of proteins was performed using 2-dimensional difference in-gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry. Analysis of spermatozoa extracts revealed that 25 identified protein spots, representing 16 proteins, underwent significant ( < 0.05) changes in abundance due to equilibration and cryopreservation. Eighteen protein spots decreased in abundance, 5 protein spots increased in abundance, and 2 protein spots showed different, specific patterns of abundance changes. Analysis of seminal fluid containing seminal plasma showed that 6 identified protein spots, representing 4 proteins, underwent significant ( < 0.05) changes in abundance due to equilibration and cryopreservation. Two protein spots increased in abundance and 4 decreased in abundance. Semen extending and equilibration seems to be responsible for a significant portion of the proteome changes related to cryopreservation technology. Most sperm proteins affected by equilibration and cryopreservation are membrane bound, and loss of those proteins may reduce natural spermatozoa coating. Further research is needed to unravel the mechanisms of the particular protein changes described in this study and establish the relationship between those changes and sperm quality.

Deep solid-state equilibration and deep melting of plagioclase-free spinel peridotite from the slow-spreading Mid-Atlantic Ridge, ODP Leg 153

NASA Astrophysics Data System (ADS)

Will, Thomas M.; Schmädicke, Esther; Frimmel, Hartwig E.

2010-11-01

A petrological investigation of abyssal, plagioclase-free spinel peridotite drilled during ODP cruise 153 in the North Atlantic revealed that the peridotite represent refractory, partial residual mantle material that experienced depletion of incompatible trace elements during upper mantle melting. The degree of partial melting as estimated from spinel compositions was c. 12%. Fractionated middle and heavy rare earth elements imply polybaric melting, with c. 1-4% initial melting in the garnet peridotite stability field and subsequent partial melting of ~7-10% in the spinel peridotite stability field. Geothermobarometric investigations revealed that the solid-state equilibration of the spinel peridotite occurred at some 1,100-1,150°C and c. 20-23 kbar, corresponding to an equilibration depth of c. 70 ± 5 km and an unusually low thermal gradient of some 11-17°C/km. A thermal re-equilibration of the peridotite occurred at ~850-1,000°C at similar depths. Naturally, the initial mantle melting in the garnet-peridotite stability field must have commenced at depths greater than 70 ± 5 km. It is likely that the residual peridotite rose rapidly through the lithospheric cap towards the ridge axis. The exhumation of the abyssal peridotite occurred, at least in parts, via extensional detachment faulting. Given the shallow to moderate dip angles of the fault surfaces, the exhumation of the peridotite from its equilibration depth would imply an overall ridge-normal horizontal displacement of c. 50-160 km if tectonic stretching and detachment faulting were the sole exhumation mechanism.

Chemically non-equilibrated QGP and thermal photon elliptic flow

NASA Astrophysics Data System (ADS)

Monnai, Akihiko

2016-07-01

It has been discovered in recent heavy-ion experiments that elliptic and triangular flow of direct photons are underpredicted by most hydrodynamic models. I discuss possible enhancement mechanisms based on late chemical equilibration of the QGP and in-medium modification of parton distributions. Numerical hydrodynamic analyses indicate that they suppress early photon emission and visibly enhance thermal photon elliptic flow.

Sorption, dissolution and pH determine the long-term equilibration and toxicity of coated and uncoated ZnO nanoparticles in soil.

PubMed

Waalewijn-Kool, Pauline L; Diez Ortiz, Maria; van Straalen, Nico M; van Gestel, Cornelis A M

2013-07-01

To assess the effect of long-term dissolution on bioavailability and toxicity, triethoxyoctylsilane coated and uncoated zinc oxide nanoparticles (ZnO-NP), non-nano ZnO and ZnCl2 were equilibrated in natural soil for up to twelve months. Zn concentrations in pore water increased with time for all ZnO forms but peaked at intermediate concentrations of ZnO-NP and non-nano ZnO, while for coated ZnO-NP such a clear peak only was seen after 12 months. Dose-related increases in soil pH may explain decreased soluble Zn levels due to fixation of Zn released from ZnO at higher soil concentrations. At T = 0 uncoated ZnO-NP and non-nano ZnO were equally toxic to the springtail Folsomia candida, but not as toxic as coated ZnO-NP, and ZnCl2 being most toxic. After three months equilibration toxicity to F. candida was already reduced for all Zn forms, except for coated ZnO-NP which showed reduced toxicity only after 12 months equilibration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Equilibration of energy in slow–fast systems

PubMed Central

Shah, Kushal; Gelfreich, Vassili; Rom-Kedar, Vered

2017-01-01

Ergodicity is a fundamental requirement for a dynamical system to reach a state of statistical equilibrium. However, in systems with several characteristic timescales, the ergodicity of the fast subsystem impedes the equilibration of the whole system because of the presence of an adiabatic invariant. In this paper, we show that violation of ergodicity in the fast dynamics can drive the whole system to equilibrium. To show this principle, we investigate the dynamics of springy billiards, which are mechanical systems composed of a small particle bouncing elastically in a bounded domain, where one of the boundary walls has finite mass and is attached to a linear spring. Numerical simulations show that the springy billiard systems approach equilibrium at an exponential rate. However, in the limit of vanishing particle-to-wall mass ratio, the equilibration rates remain strictly positive only when the fast particle dynamics reveal two or more ergodic components for a range of wall positions. For this case, we show that the slow dynamics of the moving wall can be modeled by a random process. Numerical simulations of the corresponding springy billiards and their random models show equilibration with similar positive rates. PMID:29183966

Conventional slow freezing cryopreserves mouflon spermatozoa better than vitrification.

PubMed

Pradiee, J; Esteso, M C; Castaño, C; Toledano-Díaz, A; Lopez-Sebastián, A; Guerra, R; Santiago-Moreno, J

2017-04-01

This work examines the effectiveness of a TCG (Tris, citric acid, glucose, 6% egg yolk and 5% glycerol) and a TEST (TES, Tris, glucose, 6% egg yolk and 5% glycerol) sperm extender in the freezing of mouflon spermatozoa at slow cooling rates, using different pre-freezing equilibration times (2-3 hr). It also examines the tolerance of mouflon spermatozoa to different concentrations of cryoprotectants (5, 10, 20% glycerol; 5%, 10%, 20% dimethyl sulfoxide; 6% polyvinylpyrrolidone) and/or sucrose (100, 300, 500 mm). The highest quality (p < .01) thawed spermatozoa were obtained when using the TEST extender and an equilibration time of 3 hr. Sperm motility and membrane integrity were strongly reduced when using rapid freezing rates (60-85°C min -1 ), independent of the concentration of cryoprotectants. The lowest sucrose concentration (100 mm) provided the highest (p < .05) percentage of motile spermatozoa and live spermatozoa with an intact acrosome. Vitrified-warmed sperm variables were at their best when the spermatozoa was diluted in TCG-6% egg yolk + 100 mm sucrose and warmed at 60°C. Slow warming at 37°C strongly reduced (p < .05) sperm motility and viability. However, sperm vitrification returned lower fertility, sperm motility and sperm viability values than conventional sperm freezing. © 2016 Blackwell Verlag GmbH.

Thermal Convection in High-Pressure Ice Layers Beneath a Buried Ocean within Titan and Ganymede

NASA Astrophysics Data System (ADS)

Tobie, G.; Choblet, G.; Dumont, M.

2014-12-01

Deep interiors of large icy satellites such as Titan and Ganymede probably harbor a buried ocean sandwiched between low pressure ice and high-pressure ice layers. The nature and location of the lower interface of the ocean involves equilibration of heat and melt transfer in the HP ices and is ultimately controlled by the amount heat transferred through the surface ice Ih layer. Here, we perform 3D simulations of thermal convection, using the OEDIPUS numerical tool (Choblet et al. GJI 2007), to determine the efficiency of heat and mass transfer through these HP ice mantles. In a first series of simulations with no melting, we show that a significant fraction of the HP layer reaches the melting point. Using a simple description of water production and transport, our simulations demonstrate that the melt generation in the outermost part of the HP ice layer and its extraction to the overlying ocean increase the efficiency of heat transfer and reduce strongly the internal temperature. structure and the efficiency of the heat transfer. Scaling relationships are proposed to describe the cooling effect of melt production/extraction and used to investigate the consequences of internal melting on the thermal history of Titan and Ganymede's interior.

The putative liquid-liquid transition is a liquid-solid transition in atomistic models of water

NASA Astrophysics Data System (ADS)

Limmer, David T.; Chandler, David

2011-10-01

We use numerical simulation to examine the possibility of a reversible liquid-liquid transition in supercooled water and related systems. In particular, for two atomistic models of water, we have computed free energies as functions of multiple order parameters, where one is density and another distinguishes crystal from liquid. For a range of temperatures and pressures, separate free energy basins for liquid and crystal are found, conditions of phase coexistence between these phases are demonstrated, and time scales for equilibration are determined. We find that at no range of temperatures and pressures is there more than a single liquid basin, even at conditions where amorphous behavior is unstable with respect to the crystal. We find a similar result for a related model of silicon. This result excludes the possibility of the proposed liquid-liquid critical point for the models we have studied. Further, we argue that behaviors others have attributed to a liquid-liquid transition in water and related systems are in fact reflections of transitions between liquid and crystal.

Shock temperature dependent rate law for plastic bonded explosives

NASA Astrophysics Data System (ADS)

Aslam, Tariq D.

2018-04-01

A reactive flow model for the tri-amino-tri-nitro-benzene (TATB) based plastic bonded explosive PBX 9502 (95% TATB, 5% polymeric binder Kel-F 800) is presented. This newly devised model is based primarily on the shock temperature of the material, along with local pressure, and accurately models a broader range of detonation and initiation scenarios. Specifically, sensitivity changes to the initial explosive temperature are accounted for naturally and with a single set of parameters. The equation of state forms for the reactants and products, as well as the thermodynamic closure of pressure and temperature equilibration, are carried over from the Wescott-Stewart-Davis (WSD) model [Wescott et al., J. Appl. Phys. 98, 053514 (2005) and "Modeling detonation diffraction and dead zones in PBX-9502," in Proceedings of the Thirteenth International Detonation Symposium (2006)]. This newly devised model, with Arrhenius state dependence on the shock temperature, based on the WSD equation of states, is denoted by AWSD. Modifying an existing implementation of the WSD model to the AWSD model in a hydrocode is a rather straightforward procedure.

Physical modelling of LNG rollover in a depressurized container filled with water

NASA Astrophysics Data System (ADS)

Maksim, Dadonau; Denissenko, Petr; Hubert, Antoine; Dembele, Siaka; Wen, Jennifer

2015-11-01

Stable density stratification of multi-component Liquefied Natural Gas causes it to form distinct layers, with upper layer having a higher fraction of the lighter components. Heat flux through the walls and base of the container results in buoyancy-driven convection accompanied by heat and mass transfer between the layers. The equilibration of densities of the top and bottom layers, normally caused by the preferential evaporation of Nitrogen, may induce an imbalance in the system and trigger a rapid mixing process, so-called rollover. Numerical simulation of the rollover is complicated and codes require validation. Physical modelling of the phenomenon has been performed in a water-filled depressurized vessel. Reducing gas pressure in the container to levels comparable to the hydrostatic pressure in the water column allows modelling of tens of meters industrial reservoirs using a 20 cm laboratory setup. Additionally, it allows to model superheating of the base fluid layer at temperatures close the room temperature. Flow visualizations and parametric studies are presented. Results are related to outcomes of numerical modelling.

From Lawson to Burning Plasmas: a Multi-Fluid Approach

NASA Astrophysics Data System (ADS)

Guazzotto, Luca; Betti, Riccardo

2017-10-01

The Lawson criterion, easily compared to experimental parameters, gives the value for the triple product of plasma density, temperature and energy confinement time needed for the plasma to ignite. Lawson's inaccurate assumptions of 0D geometry and single-fluid plasma model were improved in recent work, where 1D geometry and multi-fluid (ions, electrons and alphas) physics were included in the model, accounting for physical equilibration times and different energy confinement times between species. A much more meaningful analysis than Lawson's for current and future experiment would be expressed in terms of burning plasma state (Q=5, where Q is the ratio between fusion power and heating power). Minimum parameters for reaching Q=5 are calculated based on experimental profiles for density and temperatures and can immediately be compared with experimental performance by defining a no-alpha pressure. This is done in terms of the pressure that the plasma needs to reach for breakeven once the alpha heating has been subtracted from the energy balance. These calculations can be applied to current experiments and future burning-plasma devices. DE-FG02-93ER54215.

Supersonic Pitch Damping Predictions of Blunt Entry Vehicles from Static CFD Solutions

NASA Technical Reports Server (NTRS)

Schoenenberger, Mark

2013-01-01

A technique for predicting supersonic pitch damping of blunt axisymmetric bodies from static CFD data is presented. The contributions to static pitching moment due to forebody and aftbody pressure distributions are broken out and considered separately. The one-dimension moment equation is cast to model the separate contributions from forebody and aftbody pressures with no traditional damping term included. The aftbody contribution to pitching moment is lagged by a phase angle of the natural oscillation period. This lag represents the time for aftbody wake structures to equilibrate while the body is oscillation. The characteristic equation of this formulation indicates that the lagged backshell moment adds a damping moment equivalent in form to a constant pitch damping term. CFD calculations of the backshell's contribution to the static pitching moment for a range of angles-of-attack is used to predict pitch damping coefficients. These predictions are compared with ballistic range data taken of the Mars Exploration Rover (MER) capsule and forced oscillation data of the Mars Viking capsule. The lag model appears to capture dynamic stability variation due to backshell geometry as well as Mach number.

Phase relations in the system Cu-Ho-O and stability of Cu{sub 2}Ho{sub 2}O{sub 5}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, T.; Jacob, K.T.

1994-01-01

The phase relations in the system Cu-Ho-O have been determined at 1300 K using X-ray diffraction, optical microscopy, and electron microprobe analysis of samples equilibrated in evacuated quartz ampules and in pure oxygen. Only one ternary compound, Cu{sub 2}Ho{sub 2}O{sub 5}, was found to be stable. The Gibbs free energy of formation of this compound has been measured. Since the formation is endothermic, Cu{sub 2}Ho{sub 2}O{sub 5} becomes thermodynamically unstable with respect to CuO and Ho{sub 2}O{sub 3} below 810 K. When the oxygen partial pressure over Cu{sub 2}Ho{sub 2}O{sub 5} is lowered, it decomposes. The decomposition temperature at anmore » oxygen partial pressure of 1.52 X 10{sup 4} Pa was measured using a combined DTA-TGA apparatus. Based on these results, an oxygen potential diagram for the system Cu-Ho-O at 1300 K is presented.« less

Complex igneous processes and the formation of the primitive lunar crustal rocks

NASA Technical Reports Server (NTRS)

Longhi, J.; Boudreau, A. E.

1979-01-01

Crystallization of a magma ocean with initial chondritic Ca/Al and REE ratios such as proposed by Taylor and Bence (TB, 1975), is capable of producing the suite of primitive crustal rocks if the magma ocean underwent locally extensive assimilation and mixing in its upper layers as preliminary steps in formation of an anorthositic crust. Lunar anorthosites were the earliest permanent crustal rocks to form the result of multiple cycles of suspension and assimilation of plagioclase in liquids fractionating olivine and pyroxene. There may be two series of Mg-rich cumulate rocks: one which developed as a result of the equilibration of anorthositic crust with the magma ocean; the other which formed in the later stages of the magma ocean during an epoch of magma mixing and ilmenite crystallization. This second series may be related to KREEP genesis. It is noted that crystallization of the magma ocean had two components: a low pressure component which produced a highly fractionated and heterogeneous crust growing downward and a high pressure component which filled in the ocean from the bottom up, mostly with olivine and low-Ca pyroxene.

The melting temperature of liquid water with the effective fragment potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brorsen, Kurt R.; Willow, Soohaeng Y.; Xantheas, Sotiris S.

2015-09-17

Direct simulation of the solid-liquid water interface with the effective fragment potential (EFP) via the constant enthalpy and pressure (NPH) ensemble was used to estimate the melting temperature (Tm) of ice-Ih. Initial configurations and velocities, taken from equilibrated constant pressure and temperature (NPT) simulations at T = 300 K, 350 K and 400 K, respectively, yielded corresponding Tm values of 378±16 K, 382±14 K and 384±15 K. These estimates are consistently higher than experiment, albeit to the same degree with previously reported estimates using density functional theory (DFT)-based Born-Oppenheimer simulations with the Becke-Lee-Yang-Parr functional plus dispersion corrections (BLYP-D). KRB wasmore » supported by a Computational Science Graduate Fellowship from the Department of Energy. MSG was supported by a U.S. National Science Foundation Software Infrastructure (SI2) grant (ACI – 1047772). SSX acknowledges support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.« less

Effects of soil type, prepercolation, and ageing on bioaccumulation and toxicity of zinc for the springtail Folsomia candida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smit, C.E.; Van Gestel, C.A.M.

1998-06-01

Soil properties are a major influence on the bioavailability and toxicity of metals and represent one of the important factors that complicate the extrapolation of results from laboratory tests to field situations. The influence of soil characteristics and way of contamination on the bioaccumulation and toxicity of zinc was investigated for the springtail Folsomia candida, and the applicability of chemical extraction techniques for the prediction of zinc uptake and toxicity was evaluated. Bioaccumulation of zinc in F. candida was related to water-soluble zinc concentrations, and uptake was dependent on the test soil used. Effects of zinc for F. candida couldmore » not be fully explained by bioaccumulation. This indicates that the existence of a fixed internal threshold concentration of zinc above which physiological functions are impaired is not likely for F. candida. In freshly contaminated soils, zinc toxicity was related to organic matter and clay content of the soil; however, the use of these soils overestimated the effects of zinc for F. candida by a factor of 5 to 8 compared to a test soil that was subjected to ageing under field conditions for 1.5 years. Equilibration of the zinc contamination by percolating the soils with water before use in the toxicity experiment strongly reduced the difference in zinc toxicity between laboratory-treated and aged soils. Water-soluble concentrations are most appropriate to predict effects of zinc on reproduction of F. candida in soils with unknown contamination histories. For laboratory toxicity tests, it is recommended to percolate soils with water after contamination and to include an equilibration period prior to use to achieve a more realistic exposure situation.« less

Optimization of conditions for the cryopreservation of yellow catfish (Pelteobagrus fulvidraco) sperm.

PubMed

Yang, Sen; Han, Linqiang; Huang, Rushou; Liufu, Yongzhong; Meng, Zining; Lin, Haoran

2017-06-01

Yellow catfish (Pelteobagrus fulvidraco) is a promising aquaculture species in China with an increasing market demand. To serve the growing demand of male broodstock for artificial fertilization and the preservation of valuable strains for selective breeding, we tried to develop a species-specific cryopreservation protocol for yellow catfish sperm in this study. Important factors such as cryoprotectant, freezing height above the liquid nitrogen (LN) surface, dilution ratio, equilibration time, thawing temperature and cool storage before freezing were standardized. Among the cryoprotectants tested here, 10% Me 2 SO was the most suitable for sperm cryopreservation. Freezing at 7 cm above the LN surface for 10 min yielded the highest post-thaw motility. Further evaluation showed that dilution ratio of 1:3 and 1:5 produced higher post-thaw motility than semen diluted at 2:1, 1:1, 1:9 or 1:19. Equilibration times from 0 to 30 min did not cause significant differences in both equilibrated and post-thaw motility. Also, cool storage up to 24 h did not affect the suitability of sperm for cryopreservation. After thawing, sperm could be stored at 4 °C for 2 h without a reduction in motility parameters. With the combination of optimized freezing conditions, the fertilization and hatching rate of cryopreserved sperm were 87.1 ± 5.2% and 78.5 ± 7.4%, respectively, which were similar to those of fresh sperm (91.8 ± 3.5% and 83.7 ± 2.5%). In general, the cryopreservation protocol optimized here would facilitate breeding practice and hatchery operation in this economically important fish. Copyright © 2017. Published by Elsevier Inc.

Re-equilibration after quenches in athermal martensites: Conversion delays for vapor-to-liquid domain-wall phases

NASA Astrophysics Data System (ADS)

Shankaraiah, N.; Murthy, K. P. N.; Lookman, T.; Shenoy, S. R.

2015-06-01

Entropy barriers and aging states appear in martensitic structural-transition models, slowly re-equilibrating after temperature quenches, under Monte Carlo dynamics. Concepts from protein folding and aging harmonic oscillators turn out to be useful in understanding these nonequilibrium evolutions. We show how the athermal, nonactivated delay time for seeded parent-phase austenite to convert to product-phase martensite arises from an identified entropy barrier in Fourier space. In an aging state of low Monte Carlo acceptances, the strain structure factor makes constant-energy searches for rare pathways to enter a Brillouin zone "golf hole" enclosing negative-energy states, and to suddenly release entropically trapped stresses. In this context, a stress-dependent effective temperature can be defined, that re-equilibrates to the quenched bath temperature.

A Simple Method for Automated Equilibration Detection in Molecular Simulations.

PubMed

Chodera, John D

2016-04-12

Molecular simulations intended to compute equilibrium properties are often initiated from configurations that are highly atypical of equilibrium samples, a practice which can generate a distinct initial transient in mechanical observables computed from the simulation trajectory. Traditional practice in simulation data analysis recommends this initial portion be discarded to equilibration, but no simple, general, and automated procedure for this process exists. Here, we suggest a conceptually simple automated procedure that does not make strict assumptions about the distribution of the observable of interest in which the equilibration time is chosen to maximize the number of effectively uncorrelated samples in the production timespan used to compute equilibrium averages. We present a simple Python reference implementation of this procedure and demonstrate its utility on typical molecular simulation data.

Minimizing magnetic fields for precision experiments

NASA Astrophysics Data System (ADS)

Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S.; Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.

2015-06-01

An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

A simple method for automated equilibration detection in molecular simulations

PubMed Central

Chodera, John D.

2016-01-01

Molecular simulations intended to compute equilibrium properties are often initiated from configurations that are highly atypical of equilibrium samples, a practice which can generate a distinct initial transient in mechanical observables computed from the simulation trajectory. Traditional practice in simulation data analysis recommends this initial portion be discarded to equilibration, but no simple, general, and automated procedure for this process exists. Here, we suggest a conceptually simple automated procedure that does not make strict assumptions about the distribution of the observable of interest, in which the equilibration time is chosen to maximize the number of effectively uncorrelated samples in the production timespan used to compute equilibrium averages. We present a simple Python reference implementation of this procedure, and demonstrate its utility on typical molecular simulation data. PMID:26771390

Constraining the Depth of the Martian Magma Ocean during Core Formation using Element Partitioning

NASA Astrophysics Data System (ADS)

Wijbrans, Ineke; Tronche, Elodie; van Westrenen, Wim

2010-05-01

The depth of a planetary magma ocean places first order constraints on the thermal state of a young planet. For the Earth, the depth of the magma ocean is mostly constrained by the pressure-temperature conditions at which Fe-rich metal last equilibrated with the bulk silicate Earth (BSE). These equilibration conditions are thought to correspond to the conditions at the terrestrial magma ocean floor, as this is where the metal ponds before sinking to the core. This depth is estimated by combining the BSE contents of siderophile (iron-loving) elements with metal-silicate partition coefficients (D) at high temperatures and pressures [e.g. 1]. The extent and depth of a magma ocean on Mars are hotly debated. In the case of Mars, the sulphur content of the core is significantly higher than for Earth (10-16 wt% sulphur [2]). The presence of sulphur has been shown to have an effect on the metal-silicate partitioning of some siderophile elements [3], but the current data set is insufficient to be of use for direct application to Martian conditions. We have started an experimental programme to constrain siderophile element partition coefficients for Ni and Co between metal and silicate as a function of temperature, pressure and sulphur content in the metal-alloy. For the silicate composition we used a newly proposed bulk silicate Mars (BSM) [4]. We chose the above-mentioned siderophile elements because their BSM concentrations are reasonably known from studies of Martian meteorites. Our aim is to derive new constraints on the depth of the Martian magma ocean and the chemistry accompanying Martian core formation. Experimental methods: The starting material consisted of a 1:1 mixture of silicate glass + quench crystals in the FeO-CaO-MgO-Al2O3-SiO2 (FCMAS) system with a composition based on [4], and metal consisting of FeS, Fe, Ni, Co, FeP3. Four different metal compositions were used with sulphur contents of 0, 5, 15 and 25wt% respectively. Experiments were made in an end-loaded piston-cylinder using graphite-lined Pt capsules. Experiments were performed at 1, 2 and 3 GPa, and at temperatures of 1600 and 1650 °C, for 5hrs. Electron microprobe was used to determine the concentration of major and minor elements in each phase. Results: Preliminary results show that the sulfur content has an effect on the siderophile element partitioning, even within this small range of pressures and temperatures. With these experiments made with realistic conditions for a Martian magma ocean, we will present a new parameterization of metal-silicate D (Ni and Co) depending on pressure, temperature and sulfur content. References: [1] Righter (2003) Ann. Rev. Earth Planet. Sci. 31, 135-174 [2] Schubert (1990) JGR 95, 14095-14104. [3] Jana and Walker (1997) GCA 61, 5255-5277. [4] Khan and Connolly (2008) JGR, 113, E07003.

Cook and Chill: Effect of Temperature on the Performance of Nonequilibrated Blood Glucose Meters.

PubMed

Deakin, Sherine; Steele, Dominic; Clarke, Sarah; Gribben, Cathryn; Bexley, Anne-Marie; Laan, Remmert; Kerr, David

2015-08-20

Exposure to extreme temperature can affect the performance of blood glucose monitoring systems. The aim was to determine the non-equilibrated performance of these systems at extreme high and low temperatures that can occur in daily life. The performances of 5 test systems, (1) Abbott FreeStyle Freedom Lite, (2) Roche AccuChek Aviva, (3) Bayer Contour, (4) LifeScan OneTouch Verio, and (5) Sanofi BG Star, were compared after "cooking" (50°C for 1 hour) or "chilling" (-5°C for 1 hour) with room temperature controls (23°C) using whole blood with glucose concentrations of 50, 100, and 200 mg/dl. The equilibration period (time from the end of incubation to when the test system is operational) was between 1 and 8 minutes, and each test system took between 15 and 30 minutes after incubation to obtain stable measurements at room temperature. Incubating the strips at -5°C or 50°C had little effect on the glucose measurement, whereas incubating the meters introduced bias in performance between 0 and 15 minutes but not subsequently, compared to room temperature controls and at all 3 glucose levels. Compensating technologies embedded within blood glucose monitoring systems studied here perform well at extreme temperatures. People with diabetes need to be alerted to this feature to avoid perceptions of malperformance of their devices and the possible inability to get blood glucose readings on short notice (eg, during time of suspected rapid change or before an unplanned meal). © 2015 Diabetes Technology Society.

Development of a pre-concentration system and auto-analyzer for dissolved methane, ethane, propane, and butane concentration measurements with a GC-FID

NASA Astrophysics Data System (ADS)

Chepigin, A.; Leonte, M.; Colombo, F.; Kessler, J. D.

2014-12-01

Dissolved methane, ethane, propane, and butane concentrations in natural waters are traditionally measured using a headspace equilibration technique and gas chromatograph with flame ionization detector (GC-FID). While a relatively simple technique, headspace equilibration suffers from slow equilibration times and loss of sensitivity due to concentration dilution with the pure gas headspace. Here we present a newly developed pre-concentration system and auto-analyzer for use with a GC-FID. This system decreases the time required for each analysis by eliminating the headspace equilibration time, increases the sensitivity and precision with a rapid pre-concentration step, and minimized operator time with an autoanalyzer. In this method, samples are collected from Niskin bottles in newly developed 1 L plastic sample bags rather than glass vials. Immediately following sample collection, the sample bags are placed in an incubator and individually connected to a multiport sampling valve. Water is pumped automatically from the desired sample bag through a small (6.5 mL) Liqui-Cel® membrane contactor where the dissolved gas is vacuum extracted and directly flushed into the GC sample loop. The gases of interest are preferentially extracted with the Liqui-Cel and thus a natural pre-concentration effect is obtained. Daily method calibration is achieved in the field with a five-point calibration curve that is created by analyzing gas standard-spiked water stored in 5 L gas-impermeable bags. Our system has been shown to substantially pre-concentrate the dissolved gases of interest and produce a highly linear response of peak areas to dissolved gas concentration. The system retains the high accuracy, precision, and wide range of measurable concentrations of the headspace equilibration method while simultaneously increasing the sensitivity due to the pre-concentration step. The time and labor involved in the headspace equilibration method is eliminated and replaced with the immediate and automatic analysis of a maximum of 13 sequential samples. The elapsed time between sample collection and analysis is reduced from approximately 12 hrs to < 10 min, enabling dynamic and highly resolved sampling plans.

Satellite Estimation of Daily Land Surface Water Vapor Pressure Deficit from AMSR- E

NASA Astrophysics Data System (ADS)

Jones, L. A.; Kimball, J. S.; McDonald, K. C.; Chan, S. K.; Njoku, E. G.; Oechel, W. C.

2007-12-01

Vapor pressure deficit (VPD) is a key variable for monitoring land surface water and energy exchanges, and estimating plant water stress. Multi-frequency day/night brightness temperatures from the Advanced Microwave Scanning Radiometer on EOS Aqua (AMSR-E) were used to estimate daily minimum and average near surface (2 m) air temperatures across a North American boreal-Arctic transect. A simple method for determining daily mean VPD (Pa) from AMSR-E air temperature retrievals was developed and validated against observations across a regional network of eight study sites ranging from boreal grassland and forest to arctic tundra. The method assumes that the dew point and minimum daily air temperatures tend to equilibrate in areas with low night time temperatures and relatively moist conditions. This assumption was tested by comparing the VPD algorithm results derived from site daily temperature observations against results derived from AMSR-E retrieved temperatures alone. An error analysis was conducted to determine the amount of error introduced in VPD estimates given known levels of error in satellite retrieved temperatures. Results indicate that the assumption generally holds for the high latitude study sites except for arid locations in mid-summer. VPD estimates using the method with AMSR-E retrieved temperatures compare favorably with site observations. The method can be applied to land surface temperature retrievals from any sensor with day and night surface or near-surface thermal measurements and shows potential for inferring near-surface wetness conditions where dense vegetation may hinder surface soil moisture retrievals from low-frequency microwave sensors. This work was carried out at The University of Montana, at San Diego State University, and at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

Cell water potential, osmotic potential, and turgor in the epidermis and mesophyll of transpiring leaves : Combined measurements with the cell pressure probe and nanoliter osmometer.

PubMed

Nonami, H; Schulze, E D

1989-01-01

Water potential, osmotic potential and turgor measurements obtained by using a cell pressure probe together with a nanoliter osmometer were compared with measurements obtained with an isopiestic psychrometer. Both types of measurements were conducted in the mature region of Tradescantia virginiana L. leaves under non-transpiring conditions in the dark, and gave similar values of all potentials. This finding indicates that the pressure probe and the osmometer provide accurate measurements of turgor, osmotic potentials and water potentials. Because the pressure probe does not require long equilibration times and can measure turgor of single cells in intact plants, the pressure probe together with the osmometer was used to determine in-situ cell water potentials, osmotic potentials and turgor of epidermal and mesophyll cells of transpiring leaves as functions of stomatal aperture and xylem water potential. When the xylem water potential was-0.1 MPa, the stomatal aperture was at its maximum, but turgor of both epidermal and mesophyll cells was relatively low. As the xylem water potential decreased, the stomatal aperture became gradually smaller, whereas turgor of both epidermal and mesophyll cells first increased and afterward decreased. Water potentials of the mesophyll cells were always lower than those of the epidermal cells. These findings indicate that evaporation of water is mainly occurring from mesophyll cells and that peristomatal transpiration could be less important than it has been proposed previously, although peristomatal transpiration may be directly related to regulation of turgor in the guard cells.

Brine and Gas Flow Patterns Between Excavated Areas and Disturbed Rock Zone in the 1996 Performance Assessment for the Waste Isolation Pilot Plant for a Single Drilling Intrusion that Penetrates Repository and Castile Brine Reservoir

DOE Office of Scientific and Technical Information (OSTI.GOV)

ECONOMY,KATHLEEN M.; HELTON,JON CRAIG; VAUGHN,PALMER

1999-10-01

The Waste Isolation Pilot Plant (WIPP), which is located in southeastern New Mexico, is being developed for the geologic disposal of transuranic (TRU) waste by the U.S. Department of Energy (DOE). Waste disposal will take place in panels excavated in a bedded salt formation approximately 2000 ft (610 m) below the land surface. The BRAGFLO computer program which solves a system of nonlinear partial differential equations for two-phase flow, was used to investigate brine and gas flow patterns in the vicinity of the repository for the 1996 WIPP performance assessment (PA). The present study examines the implications of modeling assumptionsmore » used in conjunction with BRAGFLO in the 1996 WIPP PA that affect brine and gas flow patterns involving two waste regions in the repository (i.e., a single waste panel and the remaining nine waste panels), a disturbed rock zone (DRZ) that lies just above and below these two regions, and a borehole that penetrates the single waste panel and a brine pocket below this panel. The two waste regions are separated by a panel closure. The following insights were obtained from this study. First, the impediment to flow between the two waste regions provided by the panel closure model is reduced due to the permeable and areally extensive nature of the DRZ adopted in the 1996 WIPP PA, which results in the DRZ becoming an effective pathway for gas and brine movement around the panel closures and thus between the two waste regions. Brine and gas flow between the two waste regions via the DRZ causes pressures between the two to equilibrate rapidly, with the result that processes in the intruded waste panel are not isolated from the rest of the repository. Second, the connection between intruded and unintruded waste panels provided by the DRZ increases the time required for repository pressures to equilibrate with the overlying and/or underlying units subsequent to a drilling intrusion. Third, the large and areally extensive DRZ void volumes is a significant source of brine to the repository, which is consumed in the corrosion of iron and thus contributes to increased repository pressures. Fourth, the DRZ itself lowers repository pressures by providing storage for gas and access to additional gas storage in areas of the repository. Fifth, given the pathway that the DRZ provides for gas and brine to flow around the panel closures, isolation of the waste panels by the panel closures was not essential to compliance with the U.S. Environment Protection Agency's regulations in the 1996 WIPP PA.« less

Learning to perceive in the sensorimotor approach: Piaget’s theory of equilibration interpreted dynamically

PubMed Central

Di Paolo, Ezequiel Alejandro; Barandiaran, Xabier E.; Beaton, Michael; Buhrmann, Thomas

2014-01-01

Learning to perceive is faced with a classical paradox: if understanding is required for perception, how can we learn to perceive something new, something we do not yet understand? According to the sensorimotor approach, perception involves mastery of regular sensorimotor co-variations that depend on the agent and the environment, also known as the “laws” of sensorimotor contingencies (SMCs). In this sense, perception involves enacting relevant sensorimotor skills in each situation. It is important for this proposal that such skills can be learned and refined with experience and yet up to this date, the sensorimotor approach has had no explicit theory of perceptual learning. The situation is made more complex if we acknowledge the open-ended nature of human learning. In this paper we propose Piaget’s theory of equilibration as a potential candidate to fulfill this role. This theory highlights the importance of intrinsic sensorimotor norms, in terms of the closure of sensorimotor schemes. It also explains how the equilibration of a sensorimotor organization faced with novelty or breakdowns proceeds by re-shaping pre-existing structures in coupling with dynamical regularities of the world. This way learning to perceive is guided by the equilibration of emerging forms of skillful coping with the world. We demonstrate the compatibility between Piaget’s theory and the sensorimotor approach by providing a dynamical formalization of equilibration to give an explicit micro-genetic account of sensorimotor learning and, by extension, of how we learn to perceive. This allows us to draw important lessons in the form of general principles for open-ended sensorimotor learning, including the need for an intrinsic normative evaluation by the agent itself. We also explore implications of our micro-genetic account at the personal level. PMID:25126065

Learning to perceive in the sensorimotor approach: Piaget's theory of equilibration interpreted dynamically.

PubMed

Di Paolo, Ezequiel Alejandro; Barandiaran, Xabier E; Beaton, Michael; Buhrmann, Thomas

2014-01-01

if understanding is required for perception, how can we learn to perceive something new, something we do not yet understand? According to the sensorimotor approach, perception involves mastery of regular sensorimotor co-variations that depend on the agent and the environment, also known as the "laws" of sensorimotor contingencies (SMCs). In this sense, perception involves enacting relevant sensorimotor skills in each situation. It is important for this proposal that such skills can be learned and refined with experience and yet up to this date, the sensorimotor approach has had no explicit theory of perceptual learning. The situation is made more complex if we acknowledge the open-ended nature of human learning. In this paper we propose Piaget's theory of equilibration as a potential candidate to fulfill this role. This theory highlights the importance of intrinsic sensorimotor norms, in terms of the closure of sensorimotor schemes. It also explains how the equilibration of a sensorimotor organization faced with novelty or breakdowns proceeds by re-shaping pre-existing structures in coupling with dynamical regularities of the world. This way learning to perceive is guided by the equilibration of emerging forms of skillful coping with the world. We demonstrate the compatibility between Piaget's theory and the sensorimotor approach by providing a dynamical formalization of equilibration to give an explicit micro-genetic account of sensorimotor learning and, by extension, of how we learn to perceive. This allows us to draw important lessons in the form of general principles for open-ended sensorimotor learning, including the need for an intrinsic normative evaluation by the agent itself. We also explore implications of our micro-genetic account at the personal level.

Establishing a standard calibration methodology for MOSFET detectors in computed tomography dosimetry.

PubMed

Brady, S L; Kaufman, R A

2012-06-01

The use of metal-oxide-semiconductor field-effect transistor (MOSFET) detectors for patient dosimetry has increased by ~25% since 2005. Despite this increase, no standard calibration methodology has been identified nor calibration uncertainty quantified for the use of MOSFET dosimetry in CT. This work compares three MOSFET calibration methodologies proposed in the literature, and additionally investigates questions relating to optimal time for signal equilibration and exposure levels for maximum calibration precision. The calibration methodologies tested were (1) free in-air (FIA) with radiographic x-ray tube, (2) FIA with stationary CT x-ray tube, and (3) within scatter phantom with rotational CT x-ray tube. Each calibration was performed at absorbed dose levels of 10, 23, and 35 mGy. Times of 0 min or 5 min were investigated for signal equilibration before or after signal read out. Calibration precision was measured to be better than 5%-7%, 3%-5%, and 2%-4% for the 10, 23, and 35 mGy respective dose levels, and independent of calibration methodology. No correlation was demonstrated for precision and signal equilibration time when allowing 5 min before or after signal read out. Differences in average calibration coefficients were demonstrated between the FIA with CT calibration methodology 26.7 ± 1.1 mV cGy(-1) versus the CT scatter phantom 29.2 ± 1.0 mV cGy(-1) and FIA with x-ray 29.9 ± 1.1 mV cGy(-1) methodologies. A decrease in MOSFET sensitivity was seen at an average change in read out voltage of ~3000 mV. The best measured calibration precision was obtained by exposing the MOSFET detectors to 23 mGy. No signal equilibration time is necessary to improve calibration precision. A significant difference between calibration outcomes was demonstrated for FIA with CT compared to the other two methodologies. If the FIA with a CT calibration methodology was used to create calibration coefficients for the eventual use for phantom dosimetry, a measurement error ~12% will be reflected in the dosimetry results. The calibration process must emulate the eventual CT dosimetry process by matching or excluding scatter when calibrating the MOSFETs. Finally, the authors recommend that the MOSFETs are energy calibrated approximately every 2500-3000 mV. © 2012 American Association of Physicists in Medicine.

CO 2-induced chemo-mechanical alteration in reservoir rocks assessed via batch reaction experiments and scratch testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aman, Michael; Espinoza, D. Nicolas; Ilgen, Anastasia G.

Here, the injection of carbon dioxide (CO 2) into geological formations results in a chemical re-equilibration between the mineral assemblage and the pore fluid, with ensuing mineral dissolution and re-precipitation. Hence, target rock formations may exhibit changes of mechanical and petrophysical properties due to CO 2 exposure. We conducted batch reaction experiments with Entrada Sandstone and Summerville Siltstone exposed to de-ionized water and synthetic brine under reservoir pressure (9–10 MPa) and temperature (80°C) for up to four weeks. Samples originate from the Crystal Geyser field site, where a naturally occurring CO 2 seepage alters portions of these geologic formations. Wemore » conducted micro-scratch tests on rock samples without alteration, altered under laboratory conditions, and naturally altered over geologic time. Scratch toughness and hardness decrease as a function of exposure time and water salinity up to 52% in the case of Entrada and 87% in the case of Summerville after CO 2-induced alteration in the laboratory. Imaging of altered cores with SEM-EDS and X-ray microCT methods show dissolution of carbonate and silica cements and matrix accompanied by minor dissolution of Fe-oxides, clays, and other silicates. Parallel experiments using powdered samples confirm that dissolution of carbonate and silica are the primary reactions. The batch reaction experiments in the autoclave utilize a high fluid to rock volume ratio and represent an end member of possible alteration associated with CO 2 storage systems. These types of tests serve as a pre-screening tool to identify the susceptibility of rock facies to CO 2-related chemical-mechanical alteration during long-term CO 2 storage.« less

CO 2-induced chemo-mechanical alteration in reservoir rocks assessed via batch reaction experiments and scratch testing

DOE PAGES

Aman, Michael; Espinoza, D. Nicolas; Ilgen, Anastasia G.; ...

2017-09-22

Here, the injection of carbon dioxide (CO 2) into geological formations results in a chemical re-equilibration between the mineral assemblage and the pore fluid, with ensuing mineral dissolution and re-precipitation. Hence, target rock formations may exhibit changes of mechanical and petrophysical properties due to CO 2 exposure. We conducted batch reaction experiments with Entrada Sandstone and Summerville Siltstone exposed to de-ionized water and synthetic brine under reservoir pressure (9–10 MPa) and temperature (80°C) for up to four weeks. Samples originate from the Crystal Geyser field site, where a naturally occurring CO 2 seepage alters portions of these geologic formations. Wemore » conducted micro-scratch tests on rock samples without alteration, altered under laboratory conditions, and naturally altered over geologic time. Scratch toughness and hardness decrease as a function of exposure time and water salinity up to 52% in the case of Entrada and 87% in the case of Summerville after CO 2-induced alteration in the laboratory. Imaging of altered cores with SEM-EDS and X-ray microCT methods show dissolution of carbonate and silica cements and matrix accompanied by minor dissolution of Fe-oxides, clays, and other silicates. Parallel experiments using powdered samples confirm that dissolution of carbonate and silica are the primary reactions. The batch reaction experiments in the autoclave utilize a high fluid to rock volume ratio and represent an end member of possible alteration associated with CO 2 storage systems. These types of tests serve as a pre-screening tool to identify the susceptibility of rock facies to CO 2-related chemical-mechanical alteration during long-term CO 2 storage.« less

The Influence of Agility Training on Physiological and Cognitive Performance

DTIC Science & Technology

2010-11-01

attenuate the fat gain. We did not measure exact calorie expenditure or intake during the protocol but we did strictly equilibrate duration, frequency...bodyweight change between groups was significant (pɘ.05.) Both groups increased their percentages of body fat from pre to post testing, although the...traditional group gained slightly more fat (1.6 kg) than the agility group (0.9 kg). VO2max increased by 6.1%, or 2.6 ml/kg/min, (pɘ.05) in the

Underthrusting of passive margin strata into deep crustal hot zones associated with Cretaceous arc magmatism in North America: links and timescales of magmatic vs. tectonic thickening

NASA Astrophysics Data System (ADS)

Chin, E. J.; Lee, C.; Tollstrup, D. L.; Xie, L.; Wimpenny, J.; Yin, Q.

2011-12-01

The North American Cordillera experienced lithospheric thickening during the Cretaceous as a result of subduction-induced magmatism and tectonic shortening. Several studies suggest correlations between increased plate convergence rates and crustal underthrusting with apparent magmatic flux and evolved isotopic excursions, yet questions still remain regarding causality between tectonic and magmatic thickening. Here, we use lower crustal garnet-bearing metaquartzite (80% SiO2) xenoliths hosted in late Miocene basalts in the central Sierra Nevada Batholith, California to constrain the P-T-t (pressure-temperature-time) history of crustal thickening. The xenoliths are equigranular in texture and are comprised of >50% quartz, ~10% metamorphic garnet, <40% plagioclase, and trace rutile, kyanite, and biotite. High quartz mode, abundant well-rounded detrital zircons, and oriented graphite laths demonstrating sedimentary or metamorphic layering point to a supracrustal sedimentary protolith. However, final equilibration temperatures using titanium-in-quartz thermometry are 700 - 800 °C, and final equilibration pressures using the GASP barometer yield 0.9 - 1.3 GPa, indicating the metaquartzites equilibrated within a hot lower crust (18 - 45 km). Low whole-rock REE totals, lack of whole-rock HREE enrichment relative to LREE and MREE, and absence of positive Eu anomalies suggest that significant melting in the garnet or plagioclase fields did not occur. The whole-rock trace element geochemistry is also consistent with an initially garnet-free protolith. Simultaneous LA-ICP-MS measurements of U-Pb and Hf isotopes in detrital zircons show that all zircons have discordant U-Pb with variable upper intercept ages (1.7, 2.7, 3.3 Ga; consistent with Hf model ages), but common lower intercept ages (100 Ma). The above indicate that protoliths of the metaquartzites were North American Proterozoic to Paleozoic passive margin sediments which were simultaneously emplaced into the lower crust at ~100 Ma, during the peak of Cretaceous arc magmatism. We envision underthrusting of N. American lithosphere beneath the active Sierran arc as the mechanism for transporting these sediments to high P, T conditions, but underthrusting cold continental lithosphere alone cannot explain the xenoliths' high final temperatures. An additional heat source, derived from deep crustal magmatic "hot zones", seems required. We are currently exploring diffusion modeling in garnet porphyroblasts as a way to estimate rates of thickening. Because the protoliths were initially garnet-free, growth of metamorphic garnet can potentially record the length of time it took the metaquartzites to achieve their high P, T conditions. We will also use Ti zonation in detrital zircons as an added constraint on timescales involved in thickening. So far, our results indicate firsthand that tectonic underthrusting of continental supracrustal rocks extends all the way into deep magmatic zones beneath arcs, implying that magmatic differentiation alone is not the only mechanism by which continental crust achieves its felsic composition.

Laser Spectroscopy Monitoring of 13C18O16O and 12C17O16O of Atmospheric Carbon Dioxide

NASA Astrophysics Data System (ADS)

Shorter, J. H.; Nelson, D. D.; Ono, S.; McManus, J. B.; Zahniser, M. S.

2017-12-01

One of the main challenges to making accurate predictions of future changes in CO2 concentration is the capability to determine what fraction of human produced CO2 remains in the atmosphere. We present our progress in the application of Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) to the measurement of the primary clumped (13C18O16O) as well as 17O (12C17O16O) isotopologues of atmospheric CO2, as a tracer of its sources and sinks. We expect unique isotopologue signals in CO2 from high-temperature combustion sources, plants, soils, and air-sea exchange processes. High sampling frequency (a few minutes for each sample vs. reference cycle) achieved by a TILDAS instrument is expected to enable us to document local heterogeneous sources and temporal variations. The TILDAS is equipped with a newly developed 400-meter absorption cell. We designed a dual pressure measurement technique in which the clumped isotopologue, 13C18O16O, and 13C16O16O are first measured at 30 torr cell pressure. This is followed by measurement of 12C17O16O, 12C18O16O and 12C16O16O at lower ( 5 torr) cell pressure. Isotopologue ratios are compared between reference and sample gases. Preliminary tests demonstrated a precision approaching 0.03 ‰ for the ratio 13C18O16O/13C16O16O and 0.08‰ for Δ13C18O16O value (1σ repeatability for 4 min sample vs. reference cycle). Sample size for a single analysis is approximately 100 mL of air (1.6μmol of CO2). Given the previously observed range of variations for Δ13C18O16O and Δ17O values as large as 0.6 to 0.3 ‰, respectively, TILDAS offers a novel approach for real time monitoring of atmospheric CO2 isotopologues. It was found that achieving better than 0.1‰ requires careful matching of CO2 mixing ratios between reference and sample air. A primary cause of pressure and mixing ratio dependence is inaccurate baseline fitting (analogous to abundance sensitivity or pressure baseline for IRMS). Given that mixing ratios of atmospheric CO2 can vary as much as 50% or more, a dynamic dilution scheme, where sample air is diluted by CO2 free air to match the reference mixing ratio, is being developed. An in-line calibration source of hot, equilibrated CO2 isotopologues is also being tested. We will discuss the current instrument performance, areas for improvement, and project future applications.

A pressure relaxation closure model for one-dimensional, two-material Lagrangian hydrodynamics based on the Riemann problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamm, James R; Shashkov, Mikhail J

2009-01-01

Despite decades of development, Lagrangian hydrodynamics of strengthfree materials presents numerous open issues, even in one dimension. We focus on the problem of closing a system of equations for a two-material cell under the assumption of a single velocity model. There are several existing models and approaches, each possessing different levels of fidelity to the underlying physics and each exhibiting unique features in the computed solutions. We consider the case in which the change in heat in the constituent materials in the mixed cell is assumed equal. An instantaneous pressure equilibration model for a mixed cell can be cast asmore » four equations in four unknowns, comprised of the updated values of the specific internal energy and the specific volume for each of the two materials in the mixed cell. The unique contribution of our approach is a physics-inspired, geometry-based model in which the updated values of the sub-cell, relaxing-toward-equilibrium constituent pressures are related to a local Riemann problem through an optimization principle. This approach couples the modeling problem of assigning sub-cell pressures to the physics associated with the local, dynamic evolution. We package our approach in the framework of a standard predictor-corrector time integration scheme. We evaluate our model using idealized, two material problems using either ideal-gas or stiffened-gas equations of state and compare these results to those computed with the method of Tipton and with corresponding pure-material calculations.« less

What We Have Learned About the Existing Trace Element Partitioning data During the Population Phase of traceDs

NASA Astrophysics Data System (ADS)

Nielsen, R. L.; Ghiorso, M. S.; Trischman, T.

2015-12-01

The database traceDs is designed to provide a transparent and accessible resource of experimental partitioning data. It now includes ~ 90% of all the experimental trace element partitioning data (~4000 experiments) produced over the past 45 years, and is accessible through a web based interface (using the portal lepr.ofm-research.org). We set a minimum standard for inclusion, with the threshold criteria being the inclusion of: Experimental conditions (temperature, pressure, device, container, time, etc.) Major element composition of the phases Trace element analyses of the phases Data sources that did not report these minimum components were not included. The rationale for not including such data is that the degree of equilibration is unknown, and more important, no rigorous approach to modeling the behavior of trace elements is possible without knowledge of composition of the phases, and the temperature and pressure of formation/equilibration. The data are stored using a schema derived from that of the Library of Experimental Phase Relations (LEPR), modified to account for additional metadata, and restructured to permit multiple analytical entries for various element/technique/standard combinations. In the process of populating the database, we have learned a number of things about the existing published experimental partitioning data. Most important are: ~ 20% of the papers do not satisfy one or more of the threshold criteria. The standard format for presenting data is the average. This was developed as the standard during the time where there were space constraints for publication in spite of fact that all the information can now be published as electronic supplements. The uncertainties that are published with the compositional data are often not adequately explained (e.g. 1 or 2 sigma, standard deviation of the average, etc.). We propose a new set of publication standards for experimental data that include the minimum criteria described above, the publication of all analyses with error based on peak count rates and background, plus information on the structural state of the mineral (e.g. orthopyroxene vs. pigeonite).

Evaluation of short-term tracer fluctuations in groundwater and soil air in a two year study

NASA Astrophysics Data System (ADS)

Jenner, Florian; Mayer, Simon; Aeschbach, Werner; Weissbach, Therese

2016-04-01

The application of gas tracers like noble gases (NGs), SF6 or CFCs in groundwater studies such as paleo temperature determination requires a detailed understanding of the dynamics of reactive and inert gases in the soil air with which the infiltrating water equilibrates. Due to microbial gas consumption and production, NG partial pressures in soil air can deviate from atmospheric air, an effect that could bias noble gas temperatures estimates if not taken into account. So far, such an impact on NG contents in groundwater has not been directly demonstrated. We provide the first long-term study of the above mentioned gas tracers and physical parameters in both the saturated and unsaturated soil zone, sampled continuously for more than two years near Mannheim (Germany). NG partial pressures in soil air correlate with soil moisture and the sum value of O2+CO2, with a maximal significant enhancement of 3-6% with respect to atmospheric air during summer time. Observed seasonal fluctuations result in a mass dependent fractionation of NGs in soil air. Concentrations of SF6 and CFCs in soil air are determined by corresponding fluctuations in local atmospheric air, caused by industrial emissions. Arising concentration peaks are damped with increasing soil depth. Shallow groundwater shows short-term NG fluctuations which are smoothed within a few meters below the water table. A correlation between NG contents of soil air and of groundwater is observable during strong recharge events. However, there is no evidence for a permanent influence of seasonal variations of soil air composition on shallow groundwater. Fluctuating NG contents in shallow groundwater are rather determined by variations of soil temperature and water table level. Our data gives evidence for a further temperature driven equilibration of groundwater with entrapped air bubbles within the topmost saturated zone, which permanently occurs even some years after recharge. Local subsurface temperature fluctuations may thus lead to subsequent variations of NG contents in groundwater, independent of the former recharge temperature. This effect is of major importance for gas tracer applications in recent and shallow groundwater.

Simulation of charge transfer and orbital rehybridization in molecular and condensed matter systems

NASA Astrophysics Data System (ADS)

Nistor, Razvan A.

The mixing and shifting of electronic orbitals in molecules, or between atoms in bulk systems, is crucially important to the overall structure and physical properties of materials. Understanding and accurately modeling these orbital interactions is of both scientific and industrial relevance. Electronic orbitals can be perturbed in several ways. Doping, adding or removing electrons from systems, can change the bond-order and the physical properties of certain materials. Orbital rehybridization, driven by either thermal or pressure excitation, alters the short-range structure of materials and changes their long-range transport properties. Macroscopically, during bond formation, the shifting of electronic orbitals can be interpreted as a charge transfer phenomenon, as electron density may pile up around, and hence, alter the effective charge of, a given atom in the changing chemical environment. Several levels of theory exist to elucidate the mechanisms behind these orbital interactions. Electronic structure calculations solve the time-independent Schrodinger equation to high chemical accuracy, but are computationally expensive and limited to small system sizes and simulation times. Less fundamental atomistic calculations use simpler parameterized functional expressions called force-fields to model atomic interactions. Atomistic simulations can describe systems and time-scales larger and longer than electronic-structure methods, but at the cost of chemical accuracy. In this thesis, both first-principles and phenomenological methods are addressed in the study of several encompassing problems dealing with charge transfer and orbital rehybridization. Firstly, a new charge-equilibration method is developed that improves upon existing models to allow next-generation force-fields to describe the electrostatics of changing chemical environments. Secondly, electronic structure calculations are used to investigate the doping dependent energy landscapes of several high-temperature superconducting materials in order to parameterize the apparently large nonlinear electron-phonon coupling. Thirdly, ab initio simulations are used to investigate the role of pressure-driven structural re-organization in the crystalline-to-amorphous (or, metallic-to-insulating) transition of a common binary phase-change material composed of Ge and Sb. Practical applications of each topic will be discussed. Keywords. Charge-equilibration methods, molecular dynamics, electronic structure calculations, ab initio simulations, high-temperature superconductors, phase-change materials.

History of blood gas analysis. II. pH and acid-base balance measurements.

PubMed

Severinghaus, J W; Astrup, P B

1985-10-01

Electrometric measurement of the hydrogen ion concentration was discovered by Wilhelm Ostwald in Leipzig about 1890 and described thermodynamically by his student Walther Nernst, using the van't Hoff concept of osmotic pressure as a kind of gas pressure, and the Arrhenius concept of ionization of acids, both of which had been formalized in 1887. Hasselbalch, after adapting the pH nomenclature of Sørensen to the carbonic-acid mass equation of Henderson, made the first actual blood pH measurements (with a hydrogen electrode) and proposed that metabolic acid-base imbalance be quantified as the "reduced" pH of blood after equilibration to a carbon dioxide tension (PCO2) of 40 mm Hg. This good idea, coming 40 years before simple blood pH measurements at 37 degrees C became widely available, was never adopted. Instead, Van Slyke developed a concept of acid-base chemistry that depended on measuring plasma CO2 content with his manometric apparatus, a standard method until the 1960s, when it was displaced by the three-electrode method of blood gas analysis. The 1952 polio epidemic in Copenhagen stimulated Astrup to develop a glass electrode in which pH could be measured in blood at 37 degrees C before and after equilibration with known PCO2. He introduced the interpolative measurement of PCO2 and bicarbonate level (later base excess) using only pH measurements and, with Siggaard-Andersen, developed clinical acid-base chemistry. Controversy arose when blood base excess was noted to be altered by acute changes in PCO2 and when abnormalities of base excess were called metabolic acidosis or alkalosis, even when they represented compensation for respiratory abnormalities in PCO2. In the 1970s it became clear that "in-vivo" or "extracellular fluid" base excess (measured at an average extracellular fluid hemoglobin concentration of 5 g) eliminated the error caused by acute changes in PCO2. Base excess is now almost universally used as the index of nonrespiratory acid-base imbalance.

Ion beam plume and efflux characterization flight experiment study. [space shuttle payload

NASA Technical Reports Server (NTRS)

Sellen, J. M., Jr.; Zafran, S.; Cole, A.; Rosiak, G.; Komatsu, G. K.

1977-01-01

A flight experiment and flight experiment package for a shuttle-borne flight test of an 8-cm mercury ion thruster was designed to obtain charged particle and neutral particle material transport data that cannot be obtained in conventional ground based laboratory testing facilities. By the use of both ground and space testing of ion thrusters, the flight worthiness of these ion thrusters, for other spacecraft applications, may be demonstrated. The flight experiment definition for the ion thruster initially defined a broadly ranging series of flight experiments and flight test sensors. From this larger test series and sensor list, an initial flight test configuration was selected with measurements in charged particle material transport, condensible neutral material transport, thruster internal erosion, ion beam neutralization, and ion thrust beam/space plasma electrical equilibration. These measurement areas may all be examined for a seven day shuttle sortie mission and for available test time in the 50 - 100 hour period.

Effect of equilibration time on Pu desorption from goethite

DOE PAGES

Wong, Jennifer C.; Zavarin, Mavrik; Begg, James D.; ...

2015-01-28

Strongly sorbing ions such as plutonium may become irreversibly bound to mineral surfaces over time implicates near- and far-field transport of Pu. Batch adsorption–desorption data were collected as a function of time and pH to study the surface stability of Pu on goethite. Pu(IV) was adsorbed to goethite over the pH range 4.2 to 6.6 for different periods of time (1, 6, 15, 34 and 116 d). Moreover, following adsorption, Pu was leached from the mineral surface with desferrioxamine B (DFOB), a complexant capable of effectively competing with the goethite surface for Pu. The amount of Pu desorbed from the goethitemore » was found to vary as a function of the adsorption equilibration time, with less Pu removed from the goethite following longer adsorption periods. This effect was most pronounced at low pH. Logarithmic desorption distribution ratios for each adsorption equilibration time were fit to a pH-dependent model. Model slopes decreased between 1 and 116 d adsorption time, indicating that overall Pu(IV) surface stability on goethite surfaces becomes less dependent on pH with greater adsorption equilibration time. The combination of adsorption and desorption kinetic data suggest that non-redox aging processes affect Pu sorption behavior on goethite.« less

The effect of natural organic matter on mercury methylation by Desulfobulbus propionicus 1pr3

USGS Publications Warehouse

Moreau, John W.; Gionfriddo, Caitlin M.; Krabbenhoft, David P.; Ogorek, Jacob M.; DeWild, John F.; Aiken, George R.; Roden, Eric E.

2015-01-01

Methylation of tracer and ambient mercury (200Hg and 202Hg, respectively) equilibrated with four different natural organic matter (NOM) isolates was investigated in vivo using the Hg-methylating sulfate-reducing bacterium Desulfobulbus propionicus 1pr3. Desulfobulbus cultures grown fermentatively with environmentally representative concentrations of dissolved NOM isolates, Hg[II], and HS− were assayed for absolute methylmercury (MeHg) concentration and conversion of Hg(II) to MeHg relative to total unfiltered Hg(II). Results showed the 200Hg tracer was methylated more efficiently in the presence of hydrophobic NOM isolates than in the presence of transphilic NOM, or in the absence of NOM. Different NOM isolates were associated with variable methylation efficiencies for either the 202Hg tracer or ambient 200Hg. One hydrophobic NOM, F1 HpoA derived from dissolved organic matter from the Florida Everglades, was equilibrated for different times with Hg tracer, which resulted in different methylation rates. A 5 day equilibration with F1 HpoA resulted in more MeHg production than either the 4 h or 30 day equilibration periods, suggesting a time dependence for NOM-enhanced Hg bioavailability for methylation.

Investigating the time-dependent zeta potential of wood surfaces.

PubMed

Muff, Livius F; Luxbacher, Thomas; Burgert, Ingo; Michen, Benjamin

2018-05-15

This work reports on streaming potential measurements through natural capillaries in wood and investigates the cause of a time-dependent zeta potential measured during the equilibration of wood cell-walls with an electrolyte solution. For the biomaterial, this equilibration phase takes several hours, which is much longer than for many other materials that have been characterized by electrokinetic measurements. During this equilibration phase the zeta potential magnitude is decaying due to two parallel mechanisms: (i) the swelling of the cell-wall which causes a dimensional change reducing the charge density at the capillary interface; (ii) the transport of ions from the electrolyte solution into the permeable cell-wall which alters the electrical potential at the interface by internal charge compensation. The obtained results demonstrate the importance of equilibration kinetics for an accurate determination of the zeta potential, especially for materials that interact strongly with the measurement electrolyte. Moreover, the change in zeta potential with time can be correlated with the bulk swelling of wood if the effect of electrolyte ion diffusion is excluded. This study shows the potential of streaming potential measurements of wood, and possibly of other hygroscopic and nanoporous materials, to reveal kinetic information about their interaction with liquids, such as swelling and ion uptake. Copyright © 2018 Elsevier Inc. All rights reserved.

A critical analysis of the accuracy of several numerical techniques for combustion kinetic rate equations

NASA Technical Reports Server (NTRS)

Radhadrishnan, Krishnan

1993-01-01

A detailed analysis of the accuracy of several techniques recently developed for integrating stiff ordinary differential equations is presented. The techniques include two general-purpose codes EPISODE and LSODE developed for an arbitrary system of ordinary differential equations, and three specialized codes CHEMEQ, CREK1D, and GCKP4 developed specifically to solve chemical kinetic rate equations. The accuracy study is made by application of these codes to two practical combustion kinetics problems. Both problems describe adiabatic, homogeneous, gas-phase chemical reactions at constant pressure, and include all three combustion regimes: induction, heat release, and equilibration. To illustrate the error variation in the different combustion regimes the species are divided into three types (reactants, intermediates, and products), and error versus time plots are presented for each species type and the temperature. These plots show that CHEMEQ is the most accurate code during induction and early heat release. During late heat release and equilibration, however, the other codes are more accurate. A single global quantity, a mean integrated root-mean-square error, that measures the average error incurred in solving the complete problem is used to compare the accuracy of the codes. Among the codes examined, LSODE is the most accurate for solving chemical kinetics problems. It is also the most efficient code, in the sense that it requires the least computational work to attain a specified accuracy level. An important finding is that use of the algebraic enthalpy conservation equation to compute the temperature can be more accurate and efficient than integrating the temperature differential equation.

Investigation of thermal and temporal responses of ionization chambers in radiation dosimetry.

PubMed

AlMasri, Hussein; Funyu, Akira; Kakinohana, Yasumasa; Murayama, Sadayuki

2012-07-01

The ionization chamber is a primary dosimeter that is used in radiation dosimetry. Generally, the ion chamber response requires temperature/pressure correction according to the ideal gas law. However, this correction does not consider the thermal volume effect of chambers. The temporal and thermal volume effects of various chambers (CC01, CC13, NACP parallel-plate, PTW) with different wall and electrode materials have been studied in a water phantom. Measurements were done after heating the water with a suitable heating system, and chambers were submerged for a sufficient time to allow for temperature equilibrium. Temporal results show that all chambers equilibrate quickly in water. The equilibration time was between 3 and 5 min for all chambers. Thermal results show that all chambers expanded in response to heating except for the PTW, which contracted. This might be explained by the differences in the volumes of all chambers and also by the difference in wall material composition of PTW from the other chambers. It was found that the smallest chamber, CC01, showed the greatest expansion. The magnitude of the expansion was ~1, 0.8, and 0.9% for CC01, CC13, and parallel-plate chambers, respectively, in the temperature range of 295-320 K. The magnitude of the detected contraction was <0.3% for PTW in the same temperature range. For absolute dosimetry, it is necessary to make corrections for the ion chamber response, especially for small ion chambers like the CC01. Otherwise, room and water phantom temperatures should remain within a close range.

Water Saturation Relations and Their Diffusion-Limited Equilibration in Gas Shale: Implications for Gas Flow in Unconventional Reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tokunaga, Tetsu K.; Shen, Weijun; Wan, Jiamin

Large volumes of water are used for hydraulic fracturing of low permeability shale reservoirs to stimulate gas production, with most of the water remaining unrecovered and distributed in a poorly understood manner within stimulated regions. Because water partitioning into shale pores controls gas release, we measured the water saturation dependence on relative humidity (rh) and capillary pressure (P c) for imbibition (adsorption) as well as drainage (desorption) on samples of Woodford Shale. Experiments and modeling of water vapor adsorption into shale laminae at rh = 0.31 demonstrated that long times are needed to characterize equilibrium in larger (5 mm thick)more » pieces of shales, and yielded effective diffusion coefficients from 9 × 10 -9 to 3 × 10 -8 m 2 s -1, similar in magnitude to the literature values for typical low porosity and low permeability rocks. Most of the experiments, conducted at 50°C on crushed shale grains in order to facilitate rapid equilibration, showed significant saturation hysteresis, and that very large P c (~1 MPa) are required to drain the shales. These results quantify the severity of the water blocking problem, and suggest that gas production from unconventional reservoirs is largely associated with stimulated regions that have had little or no exposure to injected water. Finally, gravity drainage of water from fractures residing above horizontal wells reconciles gas production in the presence of largely unrecovered injected water, and is discussed in the broader context of unsaturated flow in fractures.« less

Water Saturation Relations and Their Diffusion-Limited Equilibration in Gas Shale: Implications for Gas Flow in Unconventional Reservoirs

DOE PAGES

Tokunaga, Tetsu K.; Shen, Weijun; Wan, Jiamin; ...

2017-11-15

Large volumes of water are used for hydraulic fracturing of low permeability shale reservoirs to stimulate gas production, with most of the water remaining unrecovered and distributed in a poorly understood manner within stimulated regions. Because water partitioning into shale pores controls gas release, we measured the water saturation dependence on relative humidity (rh) and capillary pressure (P c) for imbibition (adsorption) as well as drainage (desorption) on samples of Woodford Shale. Experiments and modeling of water vapor adsorption into shale laminae at rh = 0.31 demonstrated that long times are needed to characterize equilibrium in larger (5 mm thick)more » pieces of shales, and yielded effective diffusion coefficients from 9 × 10 -9 to 3 × 10 -8 m 2 s -1, similar in magnitude to the literature values for typical low porosity and low permeability rocks. Most of the experiments, conducted at 50°C on crushed shale grains in order to facilitate rapid equilibration, showed significant saturation hysteresis, and that very large P c (~1 MPa) are required to drain the shales. These results quantify the severity of the water blocking problem, and suggest that gas production from unconventional reservoirs is largely associated with stimulated regions that have had little or no exposure to injected water. Finally, gravity drainage of water from fractures residing above horizontal wells reconciles gas production in the presence of largely unrecovered injected water, and is discussed in the broader context of unsaturated flow in fractures.« less

Isospin equilibration processes and dipolar signals: Coherent cluster production

NASA Astrophysics Data System (ADS)

Papa, M.; Berceanu, I.; Acosta, L.; Agodi, C.; Auditore, L.; Cardella, G.; Chatterjee, M. B.; Dell'Aquila, D.; De Filippo, E.; Francalanza, L.; Lanzalone, G.; Lombardo, I.; Maiolino, C.; Martorana, N.; Pagano, A.; Pagano, E. V.; Pirrone, S.; Politi, G.; Quattrocchi, L.; Rizzo, F.; Russotto, P.; Trifiró, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

2017-11-01

The total dipolar signal related to multi-break-up processes induced on the system ^{48}Ca +{^{27}Al} at 40MeV/nucleon has been investigated with the CHIMERA multi-detector. Experimental data related to semi-peripheral collisions are shown and compared with CoMD-III calculations. The strong connection between the dipolar signal as obtained from the detected fragments and the dynamics of the isospin equilibration processes is also shortly discussed.

Entanglement tsunami: universal scaling in holographic thermalization.

PubMed

Liu, Hong; Suh, S Josephine

2014-01-10

We consider the time evolution of entanglement entropy after a global quench in a strongly coupled holographic system, whose subsequent equilibration is described in the gravity dual by the gravitational collapse of a thin shell of matter resulting in a black hole. In the limit of large regions of entanglement, the evolution of entanglement entropy is controlled by the geometry around and inside the event horizon of the black hole, resulting in regimes of pre-local-equilibration quadratic growth (in time), post-local-equilibration linear growth, a late-time regime in which the evolution does not carry memory of the size and shape of the entangled region, and a saturation regime with critical behavior resembling those in continuous phase transitions. Collectively, these regimes suggest a picture of entanglement growth in which an "entanglement tsunami" carries entanglement inward from the boundary. We also make a conjecture on the maximal rate of entanglement growth in relativistic systems.

Self-equilibrated Tapered Three-stage Tensegrity Mast

NASA Astrophysics Data System (ADS)

Oh, C. L.; Choong, K. K.; Nishimura, T.; Lee, S. W.

2018-04-01

Investigation of tensegrity structures for the space application is ongoing owing to the characteristics of being lightweight and flexible. Tensegrity structures consist of struts and cables are self-stressed and stable under gravitational loading. Form-finding is an important process to obtain the configuration of tensegrity structures that are in self-equilibrated state. Form-finding of tensegrity structures involves a complex computational strategy in solving the geometrical and forces of the structures. This paper aims to form-finding for a tapered three-stage tensegrity mast. The form-finding strategy involves the assemblage of the tensegrity mast, establishment of equilibrium equations and determination of one possible set of coefficient beta. Several cases of configurations with various twist angles with range of 20°-40° are investigated. A configuration with 9 struts and 42 cables satisfying the material elastic conditions was successfully found. The scalable self-equilibrated tensegrity mast is recommended for space applications.

Comparison of Mitochondrial Function in Boar and Bull Spermatozoa Throughout Cryopreservation Based on JC-1 Staining.

PubMed

Hu, C H; Zhuang, X J; Wei, Y M; Zhang, M; Lu, S S; Lu, Y Q; Yang, X G; Lu, K H

Poor reproductivity hampers the commercialization of cryopreserved boar semen. This study was to determine the differences in the sperm mitochondrial function between boar and bull semen at different cryopreservation stages. Boar and bull fresh, equilibrated, and frozen-thawed spermatozoa were evaluated for mitochondrial function using JC-1 under a fluorescent microscope. Bull and boar percentage of spermatozoa staining green (PSSG) showed no difference between fresh and equilibrated semen (P> 0.05). However, frozen-thawed bull and boar semen demonstrated significantly higher PSSG (P < 0.01) than fresh and equilibrated semen. Frozen-thawed boar semen represented a significantly higher PSSG (P < 0.01) than bull semen. Negative cryopreservation influence on boar and bull spermatozoa was not significantly produced by pre-freezing procedures, but rather by freezing and thawing. Cryopreservation has more pronounced negative effects on boar than on bull spermatozoa, which partly explains lagged commercialization of frozen boar semen.

Enhanced electron/fuel-ion equilibration through impurity ions: Studies applicable to NIF and Omega

NASA Astrophysics Data System (ADS)

Petrasso, R. D.; Sio, H.; Kabadi, N.; Lahmann, B.; Simpson, R.; Parker, C.; Frenje, J.; Gatu Johnson, M.; Li, C. K.; Seguin, F. H.; Rinderknecht, H.; Casey, D.; Grabowski, P.; Graziani, F.; Taitano, W.; Le, A.; Chacon, L.; Hoffman, N.; Kagan, G.; Simakov, A.; Zylstra, A.; Rosenberg, M.; Betti, R.; Srinivasan, B.; Mancini, R.

2017-10-01

In shock-driven exploding-pushers, a platform used extensively to study multi-species and kinetic effects, electrons and fuel ions are far out of equilibrium, as reflected by very different temperatures. However, impurity ions, even in small quantities, can couple effectively to the electrons, because of a Z2 dependence, and in turn, impurity ions can then strongly couple to the fuel ions. Through this mechanism, electrons and fuel-ions can equilibrate much faster than they otherwise would. This is a quantitative issue, depending upon the amount and Z of the impurity. For NIF and Omega, we consider the role of this process. Coupled non-linear equations, reflecting the temperatures of the three species, are solved for a range of conditions. Consideration is also given to ablatively driven implosions, since impurities can similarly affect the equilibration. This work was supported in part by DOE/NNSA DE-NA0002949 and DE-NA0002726.

Ortho-para-hydrogen equilibration on Jupiter

NASA Technical Reports Server (NTRS)

Carlson, Barbara E.; Lacis, Andrew A.; Rossow, William B.

1992-01-01

Voyager IRIS observations reveal that the Jovian para-hydrogen fraction is not in thermodynamic equilibrium near the NH3 cloud top, implying that a vertical gradient exists between the high-temperature equilibrium value of 0.25 at depth and the cloud top values. The height-dependent para-hydrogen profile is obtained using an anisotropic multiple-scattering radiative transfer model. A vertical correlation is found to exist between the location of the para-hydrogen gradient and the NH3 cloud, strongly suggesting that paramagnetic conversion on NH3 cloud particle surfaces is the dominant equilibration mechanism. Below the NH3 cloud layer, the para fraction is constant with depth and equal to the high-temperature equilibrium value of 0.25. The degree of cloud-top equilibration appears to depend on the optical depth of the NH3 cloud layer. Belt-zone variations in the para-hydrogen profile seem to be due to differences in the strength of the vertical mixing.

Generalized thermalization for integrable system under quantum quench.

PubMed

Muralidharan, Sushruth; Lochan, Kinjalk; Shankaranarayanan, S

2018-01-01

We investigate equilibration and generalized thermalization of the quantum Harmonic chain under local quantum quench. The quench action we consider is connecting two disjoint harmonic chains of different sizes and the system jumps between two integrable settings. We verify the validity of the generalized Gibbs ensemble description for this infinite-dimensional Hilbert space system and also identify equilibration between the subsystems as in classical systems. Using Bogoliubov transformations, we show that the eigenstates of the system prior to the quench evolve toward the Gibbs Generalized Ensemble description. Eigenstates that are more delocalized (in the sense of inverse participation ratio) prior to the quench, tend to equilibrate more rapidly. Further, through the phase space properties of a generalized Gibbs ensemble and the strength of stimulated emission, we identify the necessary criterion on the initial states for such relaxation at late times and also find out the states that would potentially not be described by the generalized Gibbs ensemble description.

Kibdelones: novel anticancer polyketides from a rare Australian actinomycete.

PubMed

Ratnayake, Ranjala; Lacey, Ernest; Tennant, Shaun; Gill, Jennifer H; Capon, Robert J

2007-01-01

The kibdelones are a novel family of bioactive heterocyclic polyketides produced by a rare soil actinomycete, Kibdelosporangium sp. (MST-108465). Complete relative stereostructures were assigned to kibdelones A-C (1-3), kibdelone B rhamnoside (5), 13-oxokibdelone A (7), and 25-methoxy-24-oxokibdelone C (8) on the basis of detailed spectroscopic analysis and chemical interconversion, as well as mechanistic and biosynthetic considerations. Under mild conditions, kibdelones B (2) and C (3) undergo a facile equilibration to kibdelones A-C (1-3), while kibdelone B rhamnoside (5) equilibrates to a mixture of kibdelone A-C rhamnosides (4-6). A plausible mechanism for this equilibration is proposed and involves air oxidation, quinone/hydroquinone redox transformations, and a choreographed sequence of keto/enol tautomerizations that aromatize ring C via a quinone methide intermediate. Kibdelones exhibit potent and selective cytotoxicity against a panel of human tumor cell lines and display significant antibacterial and nematocidal activity.

Transfer of volatiles and metals from mafic to felsic magmas in composite magma chambers: An experimental study

NASA Astrophysics Data System (ADS)

Guo, Haihao; Audétat, Andreas

2017-02-01

In order to determine the behavior of metals and volatiles during intrusion of mafic magma into the base of silicic, upper crustal magma chambers, fluid-rock partition coefficients (Dfluid/rock) of Li, B, Na, S, Cl, K, Mn, Fe, Rb, Sr, Ba, Ce, Cu, Zn, Ag, Cd, Mo, As, Se, Sb, Te, W, Tl, Pb and Bi were determined experimentally at 2 kbar and 850 °C close to the solidus of mafic magma. In a first step, volatile-bearing mafic glasses were prepared by melting a natural basaltic trachyandesite in the presence of volatile-bearing fluids at 1200 °C/10 kbar in piston cylinder presses. The hydrous glasses were then equilibrated in subsequent experiments at 850 °C/2 kbar in cold-seal pressure vessels, which caused 80-90% of the melt to crystallize. After 0.5-2.0 days of equilibration, the exsolved fluid was trapped by means of in-situ fracturing in the form of synthetic fluid inclusions in quartz. Both the mafic rock residue and the fluid inclusions were subsequently analyzed by laser-ablation ICP-MS for major and trace elements. Reverse experiments were conducted by equilibrating metal-bearing aqueous solutions with rock powder and then trapping the fluid. In two additional experiments, information on relative element mobilities were obtained by reacting fluids that exsolved from crystallizing mafic magma with overlying silicic melts. The combined results suggest that under the studied conditions S, Cl, Cu, Se, Br, Cd and Te are most volatile (Dfluid/rock >10), followed by Li, B, Zn, As, Ag, Sb, Cs, W, Tl, Pb and Bi (Dfluid/rock = 1-10). Less volatile are Na, Mg, K, Ca, Mn, Fe, Rb, Sr, Mo and Rb (Dfluid/rock 0.1-1), and the least fluid-mobile elements are Al, Si, Ti, Zr, Ba and Ce (Dfluid/rock <0.1). This trend is broadly consistent with relative element volatilities determined on natural high-temperature fumarole gases, although some differences exist. Based on the volatility data and measured mineral-melt and sulfide-melt partition coefficients, volatile fluxing in felsic natural samples may be identified by Cu, Se, Te and Cd-enrichment in magmatic sulfides, and by As, Se, Cd and Bi-enrichment in magmatic apatite.

[Cryopreservation of mouse embryos in ethylene glycol-based solutions: a search for the optimal and simple protocols].

PubMed

Luo, Ming-Jiu; Liu, Na; Miao, De-Qiang; Lan, Guo-Cheng; Suo-Feng; Chang, Zhong-Le; Tan, Jing-He

2005-09-01

Although ethylene glycol (EG) has been widely used for embryo cryopreservation in domestic animals, few attempts were made to use this molecule to freeze mouse and human embryos. In the few studies that used EG for slow-freezing of mouse and human embryos, complicated protocols for human embryos were used, and the protocols need to be simplified. Besides, freezing mouse morula with EG as a cryoprotectant has not been reported. In this paper, we studied the effects of embryo stages, EG concentration, duration and procedure of equilibration, sucrose supplementation and EG removal after thawing on the development of thawed mouse embryos, using the simple freezing and thawing procedures for bovine embryos. The blastulation and hatching rates (81.92% +/- 2.24% and 68.56% +/- 2.43%, respectively) of the thawed late compact morulae were significantly (P < 0.05) higher than those of embryos frozen-thawed at other stages. When mouse late compact morulae were frozen with different concentrations of EG, the highest rates of blastocyst formation and hatching were obtained with 1.8mol/L EG. The blastulation rate was significantly higher when late morulae were equilibrated in 1.8 mol/L EG for 10 min prior to freezing than when they were equilibrated for 30 min, and the hatching rate of embryos exposed to EG for 10 min was significantly higher than that of embryos exposed for 20 and 30 min. Both rates of blastocyst formation and hatching obtained with two-step equilibration were higher (P < 0.05) than with one-step equilibration in 1.8 mol/L EG. Addition of sucrose to the EG-based solution had no beneficial effects. On the contrary, an increased sucrose level (0.4 mol/L) in the solution impaired the development of the frozen-thawed embryos. In contrast, addition of 0.1 mol/L sucrose to the propylene glycol (PG)-based solution significantly improved the development of the frozen-thawed embryos. Elimination of the cryoprotectant after thawing did not improve the development of the thawed embryos. The cell numbers were less (P < 0.05) in blastocysts developed from the thawed morulae than in the in vivo derived ones. In summary, embryo stage, EG concentration, duration and procedure of equilibration and sucrose supplementation had marked effects on development of the thawed mouse embryos, and a protocol for cryopreservation of mouse embryos is recommended in which the late morulae are frozen in 1.8 mol/L EG using the simple freezing and thawing procedures of bovine embryos after a two-step equilibration and the embryos can be cultured or transferred without EG removal after thawing.

Magma Ocean Depth and Oxygen Fugacity in the Early Earth--Implications for Biochemistry.

PubMed

Righter, Kevin

2015-09-01

A large class of elements, referred to as the siderophile (iron-loving) elements, in the Earth's mantle can be explained by an early deep magma ocean on the early Earth in which the mantle equilibrated with metallic liquid (core liquid). This stage would have affected the distribution of some of the classic volatile elements that are also essential ingredients for life and biochemistry - H, C, S, and N. Estimates are made of the H, C, S, and N contents of Earth's early mantle after core formation, considering the effects of variable temperature, pressure, oxygen fugacity, and composition on their partitioning. Assessment is made of whether additional, exogenous, sources are required to explain the observed mantle concentrations, and areas are identified where additional data and experimentation would lead to an improved understanding of this phase of Earth's history.

Highly siderophile elements were stripped from Earth’s mantle by iron sulfide segregation

NASA Astrophysics Data System (ADS)

Rubie, David C.; Laurenz, Vera; Jacobson, Seth A.; Morbidelli, Alessandro; Palme, Herbert; Vogel, Antje K.; Frost, Daniel J.

2016-09-01

Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportions by late accretion, after core formation had ceased. Here we show that metal-silicate equilibration and segregation during Earth’s core formation actually increased HSE mantle concentrations because HSE partition coefficients are relatively low at the high pressures of core formation within Earth. The pervasive exsolution and segregation of iron sulfide liquid from silicate liquid (the “Hadean matte”) stripped magma oceans of HSEs during cooling and crystallization, before late accretion, and resulted in slightly suprachondritic palladium/iridium and ruthenium/iridium ratios.

Oxygen isotopes in nitrite: Analysis, calibration, and equilibration

USGS Publications Warehouse

Casciotti, K.L.; Böhlke, J.K.; McIlvin, M.R.; Mroczkowski, S.J.; Hannon, J.E.

2007-01-01

Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (NO3-), nitrite (NO2-), and nitrous oxide (N2O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because nitrite interferes with most methods of nitrate isotopic analysis, accurate isotopic analysis of nitrite is essential for correct measurement of nitrate isotopes in a sample that contains nitrite. In this study, nitrite salts with varying oxygen isotopic compositions were prepared and calibrated and then used to test the denitrifier method for nitrite oxygen isotopic analysis. The oxygen isotopic fractionation during nitrite reduction to N2O by Pseudomonas aureofaciens was lower than for nitrate conversion to N2O, while oxygen isotopic exchange between nitrite and water during the reaction was similar. These results enable the extension of the denitrifier method to oxygen isotopic analysis of nitrite (in the absence of nitrate) and correction of nitrate isotopes for the presence of nitrite in “mixed” samples. We tested storage conditions for seawater and freshwater samples that contain nitrite and provide recommendations for accurate oxygen isotopic analysis of nitrite by any method. Finally, we report preliminary results on the equilibrium isotope effect between nitrite and water, which can play an important role in determining the oxygen isotopic value of nitrite where equilibration with water is significant.

Crayfish respiration as a function of water oxygenation.

PubMed

Dejours, P; Beekenkamp, H

1977-06-01

Crayfish, Astacus leptodactylus, for several hours breathed water equilibrated either with a hypoxic gas mixture, or air, or oxygen. The hydrostatic pressure in the right epibranchial cavity was recorded and the left epibranchial water sempled from time to time. The higher the water oxygenation, the less the duration of ventilation, the frequency of the scaphognathite beats which ensure water convection, the negative of the water hydrostatic pressure relative to ambient water pressure, and the respired water flow. The water convection per unit quantity of oxygen consumed decreased by a factor of about 20 when the animal passed from hypoxic water at PO2 of 72 torr to hyperoxic water at PO2 of 697 torr. Prolonged hyperoxia, up to 100 days, results in a hypercapnic acidosis of the prebranchial blood. pH decreased about 0.2 unit, PCO2 increased from 2.5 torr to a value of 6 torr, and [HCO-3] from 6 to a value of 9 meq-L-1. This hypercapnic acidosis remained uncompensated during several weeks exposure to hyperoxia. Observations on the fresh water crayfish, a marine crab, and several species of fish, suggest that in aquatic animals (1) the ventilatory activity depends greatly on the degree of water oxygenation: the higher the water oxygenation, the lower the ventilation; (2) the change of ventilation may be accompanied by a new equilibrium of the blood acid-base status, quite different from that observed in normoxia.

The thermodynamic and hydrodynamic properties of macromolecules that influence the hydrodynamics of porous systems.

PubMed

Comper, W D

1994-06-21

The water flow across porous, semipermeable membranes associated with osmosis and filtration under a variety of conditions is analysed and compared to macromolecular diffusion across free-liquid boundaries, diffusion and sedimentation in the ultracentrifuge, and tracer diffusion of water. This study establishes that osmosis can be explained in terms of the irreversible thermodynamics of diffusion. For macromolecular osmotically active solutes in the semidilute concentration regime the water flows across semipermeable porous membranes are interpreted in terms of a rate-limiting solute-solvent exchange layer that exists on the solution side of the membrane adjacent to the membrane pore; both osmosis and filtration will be governed by these exchange layers. These exchange layers also yield unique properties of their constituent molecules in systems where there is osmotic equilibration between solutions of different solutes. This study also establishes the need to consider the internal osmotic pressure of membranes in the pressure balance associated with the flow across the membrane. The complex situation of partially permeable membranes is analysed for the simple case where there are no mechanical gradients and there is only one osmotically active solution that creates a rate-limiting exchange layer. This treatment predicts that the flow will be governed primarily by the osmotic pressure difference associated with the partitioning of the solute at the membrane-solution interface.

Phenomenological description of depoling current in Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 ferroelectric ceramics under shock wave compression: Relaxation model

NASA Astrophysics Data System (ADS)

Jiang, Dongdong; Du, Jinmei; Gu, Yan; Feng, Yujun

2012-05-01

By assuming a relaxation process for depolarization associated with the ferroelectric (FE) to antiferroelectric (AFE) phase transition in Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 ferroelectric ceramics under shock wave compression, we build a new model for the depoling current, which is different from both the traditional constant current source (CCS) model and the phase transition kinetics (PTK) model. The characteristic relaxation time and new-equilibrated polarization are dependent on both the shock pressure and electric field. After incorporating a Maxwell s equation, the relaxation model developed applies to all the depoling currents under short-circuit condition and high-impedance condition. Influences of shock pressure, load resistance, dielectric property, and electrical conductivity on the depoling current are also discussed. The relaxation model gives a good description about the suppressing effect of the self-generated electric field on the FE-to-AFE phase transition at low shock pressures, which cannot be described by the traditional models. After incorporating a time- and electric-field-dependent repolarization, this model predicts that the high-impedance current eventually becomes higher than the short-circuit current, which is consistent with the experimental results in the literature. Finally, we make the comparison between our relaxation model and the traditional CCS model and PTK model.

New findings for the equilibrated enstatite chondrite Grein 002

NASA Astrophysics Data System (ADS)

Patzer, Andrea; Schlüter, Jochen; Schultz, Ludolf; Tarkian, M.; Hill, Dolores H.; Boynton, William V.

2004-09-01

We report new petrographic and chemical data for the equilibrated EL chondrite Grein 002, including the occurrence of osbornite, metallic copper, abundant taenite, and abundant diopside. As inferred from low Si concentrations in kamacite, the presence of ferroan alabandite, textural deformation, chemical equilibration of mafic silicates, and a subsolar noble gas component, we concur with Grein 002's previous classification as an EL4-5 chondrite. Furthermore, the existence of pockets consisting of relatively coarse, euhedral enstatite crystals protruding large patches of Fe-Ni alloys suggests to us that this EL4-5 chondrite has been locally melted. We suspect impact induced shock to have triggered the formation of the melt pockets. Mineralogical evidence indicates that the localized melting of metal and adjacent enstatite must have happened relatively late in the meteorite's history. The deformation of chondrules, equilibration of mafic silicates, and generation of normal zoning in Fe, Zn-sulfides took place during thermal alteration before the melting event. Following parent body metamorphism, daubreelite was exsolved from troilite in response to a period of slow cooling at subsolidus temperatures. Exsolution of schreibersite from the coarse metal patches probably occurred during a similar period of slow cooling subsequent to the event that induced the formation of the melt pockets. Overall shock features other than localized melting correspond to stage S2 and were likely established by the final impact that excavated the Grein 002 meteoroid.

Fluid‐driven seismicity response of the Rinconada fault near Paso Robles, California, to the 2003 M 6.5 San Simeon earthquake

USGS Publications Warehouse

Hardebeck, Jeanne L.

2012-01-01

The 2003 M 6.5 San Simeon, California, earthquake caused significant damage in the city of Paso Robles and a persistent cluster of aftershocks close to Paso Robles near the Rinconada fault. Given the importance of secondary aftershock triggering in sequences of large events, a concern is whether this cluster of events could trigger another damaging earthquake near Paso Robles. An epidemic‐type aftershock sequence (ETAS) model is fit to the Rinconada seismicity, and multiple realizations indicate a 0.36% probability of at least one M≥6.0 earthquake during the next 30 years. However, this probability estimate is only as good as the projection into the future of the ETAS model. There is evidence that the seismicity may be influenced by fluid pressure changes, which cannot be forecasted using ETAS. The strongest evidence for fluids is the delay between the San Simeon mainshock and a high rate of seismicity in mid to late 2004. This delay can be explained as having been caused by a pore pressure decrease due to an undrained response to the coseismic dilatation, followed by increased pore pressure during the return to equilibrium. Seismicity migration along the fault also suggests fluid involvement, although the migration is too slow to be consistent with pore pressure diffusion. All other evidence, including focal mechanisms and b‐value, is consistent with tectonic earthquakes. This suggests a model where the role of fluid pressure changes is limited to the first seven months, while the fluid pressure equilibrates. The ETAS modeling adequately fits the events after July 2004 when the pore pressure stabilizes. The ETAS models imply that while the probability of a damaging earthquake on the Rinconada fault has approximately doubled due to the San Simeon earthquake, the absolute probability remains low.

Cell survival in a simulated Mars environment

NASA Astrophysics Data System (ADS)

Todd, Paul; Kurk, Michael Andy; Boland, Eugene; Thomas, David

2016-07-01

The most ancient life forms on earth date back comfortably to the time when liquid water was believed to be abundant on Mars. These ancient life forms include cyanobacteria, contemporary autotrophic earth organisms believed to have descended from ancestors present as long as 3.5 billion years ago. Contemporary cyanobacteria have adapted to the earth environment's harshest conditions (long-term drying, high and low temperature), and, being autotrophic, they are among the most likely life forms to withstand space travel and the Mars environment. However, it is unlikely that humans would unwittingly contaminate a planetary spacecraft with these microbes. One the other hand, heterotrophic microbes that co-habit with humans are more likely spacecraft contaminants, as history attests. Indeed, soil samples from the Atacama desert have yielded colony-forming organisms resembling enteric bacteria. There is a need to understand the survivability of cyanobacteria (likely survivors, unlikely contaminants) and heterotrophic eubacteria (unlikely survivors, likely contaminants) under simulated planetary conditions. A 35-day test was performed in a commercial planetary simulation system (Techshot, Inc., Greenville, IN) in which the minimum night-time temperature was -80 C, the maximum daytime temperature was +26 C, the simulated day-night light cycle in earth hours was 12-on and 12-off, and the total pressure of the pure CO _{2} atmosphere was maintained below 11 mbar. Any water present was allowed to equilibrate with the changing temperature and pressure. The gas phase was sampled into a CR1-A low-pressure hygrometer (Buck Technologies, Boulder, CO), and dew/frost point was measured once every hour and recorded on a data logger, along with the varying temperature in the chamber, from which the partial pressure of water was calculated. According to measurements there was no liquid water present throughout the test except during the initial pump-down period when aqueous specimens were introduced on the first day (less than 1 hour). All Samples were mixed into Mars regolith simulant for this test. Biological samples consisting of Cyanobacteria: Anabena sp., Chroococcidiopsis CCMEE171, Plectonema boryanum; Eubacteria: Bacillus subtilis, Pseudomonas aeruginosa, and Eukaryota: Chlorella ellipsoidia were maintained in the simulator under the above-described conditions. The exposed specimens were tested for intracellular esterase activity (fluorescein diacetate (FDA) hydrolysis), chlorophyll content (where appropriate) and reproductive survival (colony formation on nutrient plates). These tests all yielded low-level positive results indicating some survival in all cases. Three control populations of each species were simultaneously exposed to -80 C dark storage, +4 C dark storage, and +25 C diurnal cycles in the same Mars regolith simulant (Orbital Technologies, Madison, WI). The survival hierarchy based on intracellular esterase assay, in decreasing order of survival was Anabena > Chroococcidiopsis > Pseudomonas > Bacillus subtilis > Chlorella > Plectonema, and the range of survival based on this test was 8% - 50%. The survival hierarchy based on post-exposure colony growth was Plectonema > Chroococcidiopsis = Chlorella > Anabena, and Pseudomonas exhibited higher survival than Bacillus subtilis. These results indicate a need for longer-term high-fidelity planetary simulation studies of a wider variety of microbial species including extremophiles, such as psychrophilic strains like Psychrobacter spp., Planococcus halocryophilus, Rhodococcus sp. and the yeast Rhodotorula sp. that could be found in human environments. This research was supported by NASA NIAC Phase I Grant "Mars Ecopoiesis Testbed" NNX14AM97G.

The chlorine abundance of Earth: Implications for a habitable planet

NASA Astrophysics Data System (ADS)

Sharp, Z. D.; Draper, D. S.

2013-05-01

The Cl, Br and I contents of Earth are depleted by a factor of 10 relative to predicted values from chondritic and solar abundances. Possible explanations for the apparent discrepancy include (1) unrecognized sequestration of Cl in the core, (2) a much higher nebular volatility than normally presumed or (3) a preferential loss of the heavy halogens during planetary accretion. We tested the first assumption by conducting high pressure-temperature equilibration experiments between silicate and metal. At 15 GPa and 1900 °C, the DCl(metal-silicate) value for Cl is less than 0.007, indicating that the core is not a significant reservoir for Cl. The concentration of Cl in all chondritic classes follows a depletion trend very similar to that of Na and Mn, arguing against a low condensation temperature for Cl. Instead, we propose that the depletion of the heavy halogens is due to their unique hydrophilic behavior. Almost half of Earth's Cl and Br inventory resides in the ocean and evaporites, demonstrating the unique affinity for aqueous solutions for these elements. During planetary accretion, there would have been a strong sequestration of halogens into the crustal reservoir. 'Collisional erosion' during planetary accretion provides a mechanism that would uniquely strip the heavy halogens out of an accreting Earth. Had such loss not occurred, the salinity of the oceans would be 10× the present value, and complex life would probably never have evolved.

Phase Equilibria of ``Cu2O''-``FeO''-CaO-MgO-Al2O3 Slags at PO2 of 10-8.5 atm in Equilibrium with Metallic Copper for a Copper Slag Cleaning Production

NASA Astrophysics Data System (ADS)

Henao, Hector M.; Pizarro, Claudio; Font, Jonkion; Moyano, Alex; Hayes, Peter C.; Jak, Evgueni

2010-12-01

Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu2O”-“FeO”-SiO2-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al2O3 at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO2 weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations.

A trial of ignition innovation of gasoline engine by nanosecond pulsed low temperature plasma ignition

NASA Astrophysics Data System (ADS)

Shiraishi, Taisuke; Urushihara, Tomonori; Gundersen, Martin

2009-07-01

Application of nanosecond pulsed low temperature plasma as an ignition technique for automotive gasoline engines, which require a discharge under conditions of high back pressure, has been studied experimentally using a single-cylinder engine. The nanosecond pulsed plasma refers to the transient (non-equilibrated) phase of a plasma before the formation of an arc discharge; it was obtained by applying a high voltage with a nanosecond pulse (FWHM of approximately 80 or 25 ns) between coaxial cylindrical electrodes. It was confirmed that nanosecond pulsed plasma can form a volumetric multi-channel streamer discharge at an energy consumption of 60 mJ cycle-1 under a high back pressure of 1400 kPa. It was found that the initial combustion period was shortened compared with the conventional spark ignition. The initial flame visualization suggested that the nanosecond pulsed plasma ignition results in the formation of a spatially dispersed initial flame kernel at a position of high electric field strength around the central electrode. It was observed that the electric field strength in the air gap between the coaxial cylindrical electrodes was increased further by applying a shorter pulse. It was also clarified that the shorter pulse improved ignitability even further.

Chromium Distribution between Liquid Slag and Matte Phases

NASA Astrophysics Data System (ADS)

Eric, R. Hurman

The distribution of chromium between liquid silicate slags and copper-iron-nickel matte phases encountered in electric smelting of PGM containing South African sulphide concentrates were experimentally studied under controlled partial pressures of oxygen and sulphur. The reported experiments were conducted under silica saturation through the use of silica crucibles. Seven representative slag compositions were equilibrated with a typical sulphur deficient matte containing 18% Ni, 11% Cu, 42% Fe and 29% S. The slag constituents varied in the following ranges: SiO2: 42-58%, Al2O3: 3.5-9.0%, Fe2O3: 13-21%, MgO: 15.6-25%, CaO: 2-15%, Cr2O3: 0.2-3.5%. The slag and matte samples were synthetically prepared from pure components. The chromium content of the two phases was analysed chemically. According to the present available results of this ongoing research it was found that the partition of chromium to the matte phase decreased with an increase in the partial pressures of both oxygen and sulphur where the value of the distribution coefficient of chromium between the matte and the slag phase varied from as low as 0.07 to as high as 5.5.

Multidirectional approach to study peritoneal dialysis fluid biocompatibility in a chronic peritoneal dialysis model in the rat.

PubMed

Wieczorowska-Tobis, K; Polubinska, A; Wisniewska, J; Pawlaczyk, K; Kuzlan-Pawlaczyk, M; Filas, V; Breborowicz, A; Oreopoulos, D G

2001-03-01

Peritoneal dialysis causes the functional and morphological changes in the peritoneum that result from the bioincompatibility of dialysis solutions. We present a model of chronic peritoneal dialysis in the rat that can be used for testing the biocompatibility of dialysis fluids. Methods and Results. Long-term exposure of the peritoneum to dialysis solutions can be performed in rats with implanted peritoneal catheters. Sampling of the dialysate allows the evaluation of intraperitoneal inflammation by examining cell differential and dialysate cytokine levels. Peritoneal permeability can be evaluated at designed time intervals with the peritoneal equilibration test (PET). At the end of dialysis, peritoneal histology is studied with light and electron microscopy. Such a multidirectional approach is an effective way to test biocompatibility of dialysis solutions.

Magma storage prior to the 1912 eruption at Novarupta, Alaska

USGS Publications Warehouse

Hammer, J.E.; Rutherford, M.J.; Hildreth, W.

2002-01-01

New analytical and experimental data constrain the storage and equilibration conditions of the magmas erupted in 1912 from Novarupta in the 20th century's largest volcanic event. Phase relations at H2O+CO2 fluid saturation were determined for an andesite (58.7 wt% SiO2) and a dacite (67.7 wt%) from the compositional extremes of intermediate magmas erupted. The phase assemblages, matrix melt composition and modes of natural andesite were reproduced experimentally under H2O-saturated conditions (i.e., PH2O=PTOT) in a negatively sloping region in T-P space from 930 ??C/100 MPa to 960 ??C/75 MPa with fO2???N NO + 1. The H2O-saturated equilibration conditions of the dacite are constrained to a T-P region from 850 ??C/ 50 MPa to 880 ??C/25 MPa. If H2O-saturated, these magmas equilibrated at (and above) the level where coerupted rhyolite equilibrated (???100 MPa), suggesting that the andesite-dacite magma reservoir was displaced laterally rather than vertically from the rhyolite magma body. Natural mineral and melt compositions of intermediate magmas were also reproduced experimentally under saturation conditions with a mixed (H2O + CO2) fluid for the same range in PH2O. Thus, a storage model in which vertically stratified mafic to silicic intermediate magmas underlay H2O-saturated rhyolite is consistent with experimental findings only if the intermediates have XH2Ofl=0.7 and 0.9 for the extreme compositions, respectively. Disequilibrium features in natural pumice and scoria include pristine minerals existing outside their stability fields, and compositional zoning of titanomagnetite in contact with ilmenite. Variable rates of chemical equilibration which would eliminate these features constrain the apparent thermal excursion and re-distribution of minerals to the time scale of days.

Equilibration and aging of dense soft-sphere glass-forming liquids

NASA Astrophysics Data System (ADS)

Sánchez-Díaz, Luis Enrique; Ramírez-González, Pedro; Medina-Noyola, Magdaleno

2013-05-01

The recently developed nonequilibrium extension of the self-consistent generalized Langevin equation theory of irreversible relaxation [Ramírez-González and Medina-Noyola, Phys. Rev. E10.1103/PhysRevE.82.061503 82, 061503 (2010); Ramírez-González and Medina-Noyola, Phys. Rev. E10.1103/PhysRevE.82.061504 82, 061504 (2010)] is applied to the description of the irreversible process of equilibration and aging of a glass-forming soft-sphere liquid that follows a sudden temperature quench, within the constraint that the local mean particle density remains uniform and constant. For these particular conditions, this theory describes the nonequilibrium evolution of the static structure factor S(k;t) and of the dynamic properties, such as the self-intermediate scattering function FS(k,τ;t), where τ is the correlation delay time and t is the evolution or waiting time after the quench. Specific predictions are presented for the deepest quench (to zero temperature). The predicted evolution of the α-relaxation time τα(t) as a function of t allows us to define the equilibration time teq(ϕ), as the time after which τα(t) has attained its equilibrium value ταeq(ϕ). It is predicted that both, teq(ϕ) and ταeq(ϕ), diverge as ϕ→ϕ(a), where ϕ(a) is the hard-sphere dynamic-arrest volume fraction ϕ(a)(≈0.582), thus suggesting that the measurement of equilibrium properties at and above ϕ(a) is experimentally impossible. The theory also predicts that for fixed finite waiting times t, the plot of τα(t;ϕ) as a function of ϕ exhibits two regimes, corresponding to samples that have fully equilibrated within this waiting time (ϕ≤ϕ(c)(t)), and to samples for which equilibration is not yet complete (ϕ≥ϕ(c)(t)). The crossover volume fraction ϕ(c)(t) increases with t but saturates to the value ϕ(a).

Metal-driven and covalent synthesis of supramolecular grids from racks: a convergent approach to heterometallic and heteroleptic nanostructures.

PubMed

Schmittel, Michael; Kalsani, Venkateshwarlu; Bats, Jan W

2005-06-13

Supramolecular nanogrids were prepared from dynamic supramolecular racks through the coupling of terminal alkynes using either a covalent (with CuCl/O(2)) or a coordinative (with [trans-(PEt(3))(2)PtCl(2)]) approach. Because of the rapid equilibration of the racks (as tested by exchange reactions), oligomeric adducts potentially formed in the coupling process will selectively furnish the nanogrids through an entropically driven self-repair mechanism. To ascertain the structural assignment, the nanogrids were also synthesized by an independent strategy.

Solubility of water in lunar basalt at low pH2O

NASA Astrophysics Data System (ADS)

Newcombe, M. E.; Brett, A.; Beckett, J. R.; Baker, M. B.; Newman, S.; Guan, Y.; Eiler, J. M.; Stolper, E. M.

2017-03-01

We report the solubility of water in Apollo 15 basaltic "Yellow Glass" and an iron-free basaltic analog composition at 1 atm and 1350 °C. We equilibrated melts in a 1-atm furnace with flowing H2/CO2 gas mixtures that spanned ∼8 orders of magnitude in fO2 (from three orders of magnitude more reducing than the iron-wüstite buffer, IW-3.0, to IW+4.8) and ∼4 orders of magnitude in pH2/pH2O (from 0.003 to 24). Based on Fourier transform infrared spectroscopy (FTIR), our quenched experimental glasses contain 69-425 ppm total water (by weight). Our results demonstrate that under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH2O in the furnace atmosphere and is independent of fO2 and pH2/pH2O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H2 in our iron-free experiments is <∼4 ppm, even at oxygen fugacities as low as IW-2.3 and pH2/pH2O as high as 11; (5) Secondary ion mass spectrometry (SIMS) analyses of water in iron-rich glasses equilibrated under variable fO2 conditions may be strongly influenced by matrix effects, even when the concentration of water in the glasses is low; and (6) Our results can be used to constrain the entrapment pressure of lunar melt inclusions and the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads. We find that the most water-rich melt inclusion of Hauri et al. (2011) would be in equilibrium with a vapor with pH2O ∼ 3 bar and pH2 ∼ 8 bar. We constrain the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads to be 0.0005 bar and 0.0011 bar respectively. We calculate that batch degassing of lunar magmas containing initial volatile contents of 1200 ppm H2O (dissolved primarily as hydroxyl) and 4-64 ppm C would produce enough vapor to reach the critical vapor volume fraction thought to be required for magma fragmentation (∼65-75 vol.%) at a total pressure of ∼5 bar (corresponding to a depth beneath the lunar surface of ∼120 m). At a fragmentation pressure of ∼5 bar, the calculated vapor composition is dominated by H2, supporting the hypothesis that H2, rather than CO, was the primary propellant of the lunar fire fountain eruptions. The results of our batch degassing model suggest that initial melt compositions with >∼200 ppm C would be required for the vapor composition to be dominated by CO rather than H2 at 65-75% vesicularity.

Unconventional barometry and rheometry: new quantification approaches for mechanically-controlled microstructures

NASA Astrophysics Data System (ADS)

Tajcmanova, L.; Moulas, E.; Vrijmoed, J.; Podladchikov, Y.

2016-12-01

Estimation of pressure-temperature (P-T) from petrographic observations in metamorphic rocks has become a common practice in petrology studies during the last 50 years. This data often serves as a key input in geodynamic reconstructions and thus directly influences our understanding of lithospheric processes. Such an approach might have led the metamorphic geology field to a certain level of quiescence. In the classical view of metamorphic quantification approaches, fast viscous relaxation (and therefore constant pressure across the rock microstructure) is assumed, with chemical diffusion being the limiting factor in equilibration. Recently, we have focused on the other possible scenario - fast chemical diffusion and slow viscous relaxation - and brings an alternative interpretation of chemical zoning found in high-grade rocks. The aim has been to provide insight into the role of mechanically maintained pressure variations on multi-component chemical zoning in minerals. Furthermore, we used the pressure information from the mechanically-controlled microstructure for rheological constrains. We show an unconventional way of relating the direct microstructural observations in rocks to the nonlinearity of rheology at time scales unattainable by laboratory measurements. Our analysis documents that mechanically controlled microstructures that have been preserved over geological times can be used to deduce flow-law parameters and in turn estimate stress levels of minerals in their natural environment. The development of the new quantification approaches has opened new horizons in understanding the phase transformations in the Earth's lithosphere. Furthermore, the new data generated can serve as a food for thought for the next generation of fully coupled numerical codes that involve reacting materials while respecting conservation of mass, momentum and energy.

Average rainwater pH, concepts of atmospheric acidity, and buffering in open systems

NASA Astrophysics Data System (ADS)

Liljestrand, Howard M.

The system of water equilibrated with a constant partial pressure of CO 2, as a reference point for pH acidity-alkalinity relationships, has nonvolatile acidity and alkalinity components as conservative quantities, but not [H +]. Simple algorithms are presented for the determination of the average pH for combinations of samples both above and below pH 5.6. Averaging the nonconservative quantity [H +] yields erroneously low mean pH values. To extend the open CO 2 system to include other volatile atmospheric acids and bases distributed among the gas, liquid and particulate matter phases, a theoretical framework for atmospheric acidity is presented. Within certain oxidation-reduction limitations, the total atmospheric acidity (but not free acidity) is a conservative quantity. The concept of atmospheric acidity is applied to air-water systems approximating aerosols, fogwater, cloudwater and rainwater. The buffer intensity in hydrometeors is described as a function of net strong acidity, partial pressures of acid and base gases and the water to air ratio. For high liquid to air volume ratios, the equilibrium partial pressures of trace acid and base gases are set by the pH or net acidity controlled by the nonvolatile acid and base concentrations. For low water to air volume ratios as well as stationary state systems such as precipitation scavenging with continuous emissions, the partial pressures of trace gases (NH 3, HCl, HNO 3, SO 2 and CH 3COOH) appear to be of greater or equal importance as carbonate species as buffers in the aqueous phase.

Effect of controlled and uncontrolled rate of cooling, prior to controlled rate of freezing, on motion characteristics and acrosomal integrity of cryopreserved ram spermatozoa.

PubMed

Joshi, Anil; Kumar, Davendra; Naqvi, S M K; Maurya, V P

2008-12-01

A programmable cell freezer provides ideal cryobiological conditions for controlled-rate cooling and freezing of ram spermatozoa. The purpose of this study was to investigate the effects of controlled (Group 1) and uncontrolled (Group 2) cooling conditions prior to programmable freezing of ram semen on post-thaw sperm motion characteristics and acrosomal integrity of ram spermatozoa. Semen samples of good initial motility obtained from adult Malpura rams were pooled, diluted to 1 × 10(9) spermatozoa per milliliter with Egg yolk-TEST-glycerol extender, and packaged in 0.25 mL straws. Straws representing Group 1 were cooled in a programmable cell freezer from 25°C to 5°C at the rate of -0.15°C per minute followed by a holding time of 2 h for equilibration, while straws of Group 2 were allowed to cool slowly up to 5°C and equilibrate for 2 h in the cold cabinet. After equilibration, straws of Group 2 were also loaded in the cell freezer for freezing straws of both the treatment groups simultaneously from 5°C to -125°C at the rate of -25°C per minute. Thawing of straws was done at 50°C for 10 s and the quality of frozen-thawed spermatozoa was objectively assessed by using sperm motility analyzer. Thawed samples were also evaluated for acrosomal integrity after staining the dried semen smears with Giemsa stain. The average post-thaw motility of straws was significantly higher (P < 0.05) in samples frozen after controlled cooling, compared with samples frozen after uncontrolled rate of cooling. The percent of spermatozoa with normal acrosome was also significantly (P < 0.05) higher in Group 1, compared to Group 2. The results indicate that controlled-rate cooling has a significant effect on post-thaw motility and acrosomal integrity of frozen-thawed ram spermatozoa, compared to uncontrolled-rate cooling prior to programmable freezing.

Abiotic vs biological sources and fates of organic compounds in a low temperature continental serpentinizing system

NASA Astrophysics Data System (ADS)

Robinson, K.; Noble, S. M.; Shock, E.

2016-12-01

Serpentinization is likely the most common water-rock reaction in our solar system. During this process ultramafic silicates are hydrated, a calcium hydroxide solution is formed, and H2O is reduced to H2 coupled to the oxidation of Fe2+ to Fe3+. The resulting hyper-alkaline, reduced conditions generate thermodynamic drives for numerous carbon compound reactions, including the precipitation of various carbonate minerals and the reduction of inorganic carbonate to organic carbon. Testing the extent to which these thermodynamic drives lead to observable results led to the present study of the flow and transformations of carbon through the active continental serpentinizing system at the Samail Ophiolite in the Sultanate of Oman. Water samples were collected from shallow groundwater (representing system input), hyper-alkaline seeps (system output), boreholes (system intermediate), and surface fluid mixing zones, and analyzed for concentrations of dissolved inorganic carbon (DIC + δ13C), organic carbon (+ δ13C), formate, acetate, H2, methane (+ δ13C), ethane, and an accompanying suite of other geochemical solutes. These analyses indicate that the vast majority of DIC in these serpentinizing fluids precipitates in the subsurface as carbonate minerals; however, a significant amount of DIC is converted into organic acids and light hydrocarbons and expelled at the surface in hyper-alkaline seeps. Based on thermodynamic calculations, it seems most likely that formate last equilibrated with dolomite (CaMg[CO3]2) in the subsurface, acetate last equilibrated with calcite (CaCO3) near the surface, and methane and ethane last equilibrated in a distinct carbon-limited region of the subsurface. As for the fates of these compounds, energetic calculations reveal that a combination of oxidative, reductive, and fermentative metabolisms are thermodynamically favorable. Indeed, δ13C trends record microbial methane oxidation at the surface and cannot rule out methane as biologically sourced from the subsurface.

Equilibrium and Effective Climate Sensitivity

NASA Astrophysics Data System (ADS)

Rugenstein, M.; Bloch-Johnson, J.

2016-12-01

Atmosphere-ocean general circulation models, as well as the real world, take thousands of years to equilibrate to CO2 induced radiative perturbations. Equilibrium climate sensitivity - a fully equilibrated 2xCO2 perturbation - has been used for decades as a benchmark in model intercomparisons, as a test of our understanding of the climate system and paleo proxies, and to predict or project future climate change. Computational costs and limited time lead to the widespread practice of extrapolating equilibrium conditions from just a few decades of coupled simulations. The most common workaround is the "effective climate sensitivity" - defined through an extrapolation of a 150 year abrupt2xCO2 simulation, including the assumption of linear climate feedbacks. The definitions of effective and equilibrium climate sensitivity are often mixed up and used equivalently, and it is argued that "transient climate sensitivity" is the more relevant measure for predicting the next decades. We present an ongoing model intercomparison, the "LongRunMIP", to study century and millennia time scales of AOGCM equilibration and the linearity assumptions around feedback analysis. As a true ensemble of opportunity, there is no protocol and the only condition to participate is a coupled model simulation of any stabilizing scenario simulating more than 1000 years. Many of the submitted simulations took several years to conduct. As of July 2016 the contribution comprises 27 scenario simulations of 13 different models originating from 7 modeling centers, each between 1000 and 6000 years. To contribute, please contact the authors as soon as possible We present preliminary results, discussing differences between effective and equilibrium climate sensitivity, the usefulness of transient climate sensitivity, extrapolation methods, and the state of the coupled climate system close to equilibrium. Caption for the Figure below: Evolution of temperature anomaly and radiative imbalance of 22 simulations with 12 models (color indicates the model). 20 year moving average.

Evaluation of soil water stable isotope analysis by H2O(liquid)-H2O(vapor) equilibration method

NASA Astrophysics Data System (ADS)

Gralher, Benjamin; Stumpp, Christine

2014-05-01

Environmental tracers like stable isotopes of water (δ18O, δ2H) have proven to be valuable tools to study water flow and transport processes in soils. Recently, a new technique for soil water isotope analysis has been developed that employs a vapor phase being in isothermal equilibrium with the liquid phase of interest. This has increased the potential application of water stable isotopes in unsaturated zone studies as it supersedes laborious extraction of soil water. However, uncertainties of analysis and influencing factors need to be considered. Therefore, the objective of this study was to evaluate different methodologies of analysing stable isotopes in soil water in order to reduce measurement uncertainty. The methodologies included different preparation procedures of soil cores for equilibration of vapor and soil water as well as raw data correction. Two different inflatable sample containers (freezer bags, bags containing a metal layer) and equilibration atmospheres (N2, dry air) were tested. The results showed that uncertainties for δ18O were higher compared to δ2H that cannot be attributed to any specific detail of the processing routine. Particularly, soil samples with high contents of organic matter showed an apparent isotope enrichment which is indicative for fractionation due to evaporation. However, comparison of water samples obtained from suction cups with the local meteoric water line indicated negligible fractionation processes in the investigated soils. Therefore, a method was developed to correct the raw data reducing the uncertainties of the analysis.. We conclude that the evaluated method is advantageous over traditional methods regarding simplicity, resource requirements and sample throughput but careful consideration needs to be made regarding sample handling and data processing. Thus, stable isotopes of water are still a good tool to determine water flow and transport processes in the unsaturated zone.

Collision efficiency of water in the unimolecular reaction CH4 (+H2O) ⇆ CH3 + H (+H2O): one-dimensional and two-dimensional solutions of the low-pressure-limit master equation.

PubMed

Jasper, Ahren W; Miller, James A; Klippenstein, Stephen J

2013-11-27

The low-pressure-limit unimolecular decomposition of methane, CH4 (+M) ⇆ CH3 + H (+M), is characterized via low-order moments of the total energy, E, and angular momentum, J, transferred due to collisions. The low-order moments are calculated using ensembles of classical trajectories, with new direct dynamics results for M = H2O and new results for M = O2 compared with previous results for several typical atomic (M = He, Ne, Ar, Kr) and diatomic (M = H2 and N2) bath gases and one polyatomic bath gas, M = CH4. The calculated moments are used to parametrize three different models of the energy transfer function, from which low-pressure-limit rate coefficients for dissociation, k0, are calculated. Both one-dimensional and two-dimensional collisional energy transfer models are considered. The collision efficiency for M = H2O relative to the other bath gases (defined as the ratio of low-pressure limit rate coefficients) is found to depend on temperature, with, e.g., k0(H2O)/k0(Ar) = 7 at 2000 K but only 3 at 300 K. We also consider the rotational collision efficiency of the various baths. Water is the only bath gas found to fully equilibrate rotations, and only at temperatures below 1000 K. At elevated temperatures, the kinetic effect of "weak-collider-in-J" collisions is found to be small. At room temperature, however, the use of an explicitly two-dimensional master equation model that includes weak-collider-in-J effects predicts smaller rate coefficients by 50% relative to the use of a statistical model for rotations. The accuracies of several methods for predicting relative collision efficiencies that do not require solving the master equation and that are based on the calculated low-order moments are tested. Troe's weak collider efficiency, βc, includes the effect of saturation of collision outcomes above threshold and accurately predicts the relative collision efficiencies of the nine baths. Finally, a brief discussion is presented of mechanistic details of the energy transfer process, as inferred from the trajectories.

On the feasibility to conduct gradient liquid chromatography separations in narrow-bore columns at pressures up to 2000bar.

PubMed

De Pauw, Ruben; Swier, Tim; Degreef, Bart; Desmet, Gert; Broeckhoven, Ken

2016-11-18

The limits in operating pressures are extended for narrow-bore columns in gradient elution up to 2000bar. As the required pumps for these pressures are incompatible with common chromatographic solvents and are not suitable to apply a mobile phase composition gradient, a mobile phase delivery and injection system is described and experimentally validated which allows to use any possible chromatographic solvent in isocratic and gradient elution. The mobile phase delivery and injection system also allows to perform multiple separations without the need to depressurize the column. This system consists out of 5 dual on/off valves and two large volume loops in which the gradient and equilibration volume of initial mobile phase are loaded by a commercial liquid chromatography pump. The loops are then flushed toward the column at extreme pressures. The mobile phase delivery and injection system is first evaluated in isocratic elution and shows a comparable performance to a state-of-the-art commercial flow-through-needle injector but with twice the pressure rating. Distortion of the loaded gradient by dispersion in the gradient storage loop is studied. The effect of the most important parameters (such as flow rate, pressure and gradient steepness) is experimentally investigated. Different gradient steepnesses and volumes can be applied at different flow rates and operating pressures with a good repeatability. Due to the isobaric operation of the pumps, the gradient is monitored in real-time by a mass flow meter installed at the detector outlet. The chromatograms are then converted from time to volume-base. A separation of a 19-compound sample is performed on a 300×2.1mm column at 1000bar and on a 600×2.1mm column at 2000bar. The peak capacity was found to increase from 141 to 199 and thus scales with L as is predicted by theory. This allows to conclude that the inlet pressure for narrow-bore columns in gradient elution can be increased up to 2000bar without fundamental pressure-induced limitations. Copyright © 2016 Elsevier B.V. All rights reserved.

Formation of C-C and C-O bonds and oxygen removal in reactions of alkanediols, alkanols, and alkanals on copper catalysts.

PubMed

Sad, María E; Neurock, Matthew; Iglesia, Enrique

2011-12-21

This study reports evidence for catalytic deoxygenation of alkanols, alkanals, and alkanediols on dispersed Cu clusters with minimal use of external H(2) and with the concurrent formation of new C-C and C-O bonds. These catalysts selectively remove O-atoms from these oxygenates as CO or CO(2) through decarbonylation or decarboxylation routes, respectively, that use C-atoms present within reactants or as H(2)O using H(2) added or formed in situ from CO/H(2)O mixtures via water-gas shift. Cu catalysts fully convert 1,3-propanediol to equilibrated propanol-propanal intermediates that subsequently form larger oxygenates via aldol-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal-propanol-H(2) equilibration is mediated by their chemisorption and interconversion at surfaces via C-H and O-H activation and propoxide intermediates. The kinetic effects of H(2), propanal, and propanol pressures on turnover rates, taken together with measured selectivities and the established chemical events for base-catalyzed condensation and esterification reactions, indicate that both reactions involve kinetically relevant bimolecular steps in which propoxide species, acting as the base, abstract the α-hydrogen in adsorbed propanal (condensation) or attack the electrophilic C-atom at its carbonyl group (esterification). These weakly held basic alkoxides render Cu surfaces able to mediate C-C and C-O formation reactions typically catalyzed by basic sites inherent in the catalyst, instead of provided by coadsorbed organic moieties. Turnover rates for condensation and esterification reactions decrease with increasing Cu dispersion, because low-coordination corner and edge atoms prevalent on small clusters stabilize adsorbed intermediates and increase the activation barriers for the bimolecular kinetically relevant steps required for both reactions. © 2011 American Chemical Society

High-throughput analysis of bergamot essential oil by fast solid-phase microextraction-capillary gas chromatography-flame ionization detection.

PubMed

Tranchida, Peter Quinto; Presti, Maria Lo; Costa, Rosaria; Dugo, Paola; Dugo, Giovanni; Mondello, Luigi

2006-01-20

The advantages of using a narrow-bore column in headspace solid-phase microextraction-gas chromatographic (HS-SPME-GC) analysis are investigated. An automated rapid HS-SPME-GC method for the determination of volatile compounds in a complex sample (bergamot essential oil) was developed. A low-capacity (7 microm) SPME fibre was employed, enabling a short equilibration time (15 min). The absorbed volatile compounds were then separated in 12.5 min on a 10 m x 0.1 mm I.D. capillary. The fast GC method was characterized by relatively moderate GC parameters (head pressure: 173 kPa; temperature program rate: 12 degrees C/min). The employment of the low-capacity fibre also suited the reduced sample capacity of the capillary employed, hence column overloading was avoided. Analytical repeatibility was determined in terms of retention times (maximum RSD: 0.32%) and peak areas (maximum RSD: 9.80%). The results obtained were compared to those derived from a conventional HS-SPME-GC (a 30 microm SPME fibre and 0.25 mm I.D. capillary were used) application on the same sample. In this respect, a great reduction of analytical time was obtained both with regard to the conventional SPME equilibration and GC run times, which both required 50 min. Peak resolution was altogether comparable in both applications. Although a slight loss in terms of sensitivity was observed in the rapid approach (generally within the 25-50% range), this did not impair the detection of all peaks of interest. Finally, the selectivities of the 30 and 7 microm fibres were evaluated and, as expected, these were in good agreement.

Quantifying pCO2 in biological ocean acidification experiments: A comparison of four methods.

PubMed

Watson, Sue-Ann; Fabricius, Katharina E; Munday, Philip L

2017-01-01

Quantifying the amount of carbon dioxide (CO2) in seawater is an essential component of ocean acidification research; however, equipment for measuring CO2 directly can be costly and involve complex, bulky apparatus. Consequently, other parameters of the carbonate system, such as pH and total alkalinity (AT), are often measured and used to calculate the partial pressure of CO2 (pCO2) in seawater, especially in biological CO2-manipulation studies, including large ecological experiments and those conducted at field sites. Here we compare four methods of pCO2 determination that have been used in biological ocean acidification experiments: 1) Versatile INstrument for the Determination of Total inorganic carbon and titration Alkalinity (VINDTA) measurement of dissolved inorganic carbon (CT) and AT, 2) spectrophotometric measurement of pHT and AT, 3) electrode measurement of pHNBS and AT, and 4) the direct measurement of CO2 using a portable CO2 equilibrator with a non-dispersive infrared (NDIR) gas analyser. In this study, we found these four methods can produce very similar pCO2 estimates, and the three methods often suited to field-based application (spectrophotometric pHT, electrode pHNBS and CO2 equilibrator) produced estimated measurement uncertainties of 3.5-4.6% for pCO2. Importantly, we are not advocating the replacement of established methods to measure seawater carbonate chemistry, particularly for high-accuracy quantification of carbonate parameters in seawater such as open ocean chemistry, for real-time measures of ocean change, nor for the measurement of small changes in seawater pCO2. However, for biological CO2-manipulation experiments measuring differences of over 100 μatm pCO2 among treatments, we find the four methods described here can produce similar results with careful use.

Modelling of Equilibrium Between Mantle and Core: Refractory, Volatile, and Highly Siderophile Elements

NASA Technical Reports Server (NTRS)

Righter, K.; Danielson, L.; Pando, K.; Shofner, G.; Lee, C. -T.

2013-01-01

Siderophile elements have been used to constrain conditions of core formation and differentiation for the Earth, Mars and other differentiated bodies [1]. Recent models for the Earth have concluded that the mantle and core did not fully equilibrate and the siderophile element contents of the mantle can only be explained under conditions where the oxygen fugacity changes from low to high during accretion and the mantle and core do not fully equilibrate [2,3]. However these conclusions go against several physical and chemical constraints. First, calculations suggest that even with the composition of accreting material changing from reduced to oxidized over time, the fO2 defined by metal-silicate equilibrium does not change substantially, only by approximately 1 logfO2 unit [4]. An increase of more than 2 logfO2 units in mantle oxidation are required in models of [2,3]. Secondly, calculations also show that metallic impacting material will become deformed and sheared during accretion to a large body, such that it becomes emulsified to a fine scale that allows equilibrium at nearly all conditions except for possibly the length scale for giant impacts [5] (contrary to conclusions of [6]). Using new data for D(Mo) metal/silicate at high pressures, together with updated partitioning expressions for many other elements, we will show that metal-silicate equilibrium across a long span of Earth s accretion history may explain the concentrations of many siderophile elements in Earth's mantle. The modeling includes refractory elements Ni, Co, Mo, and W, as well as highly siderophile elements Au, Pd and Pt, and volatile elements Cd, In, Bi, Sb, Ge and As.

Quantifying pCO2 in biological ocean acidification experiments: A comparison of four methods

PubMed Central

Fabricius, Katharina E.; Munday, Philip L.

2017-01-01

Quantifying the amount of carbon dioxide (CO2) in seawater is an essential component of ocean acidification research; however, equipment for measuring CO2 directly can be costly and involve complex, bulky apparatus. Consequently, other parameters of the carbonate system, such as pH and total alkalinity (AT), are often measured and used to calculate the partial pressure of CO2 (pCO2) in seawater, especially in biological CO2-manipulation studies, including large ecological experiments and those conducted at field sites. Here we compare four methods of pCO2 determination that have been used in biological ocean acidification experiments: 1) Versatile INstrument for the Determination of Total inorganic carbon and titration Alkalinity (VINDTA) measurement of dissolved inorganic carbon (CT) and AT, 2) spectrophotometric measurement of pHT and AT, 3) electrode measurement of pHNBS and AT, and 4) the direct measurement of CO2 using a portable CO2 equilibrator with a non-dispersive infrared (NDIR) gas analyser. In this study, we found these four methods can produce very similar pCO2 estimates, and the three methods often suited to field-based application (spectrophotometric pHT, electrode pHNBS and CO2 equilibrator) produced estimated measurement uncertainties of 3.5–4.6% for pCO2. Importantly, we are not advocating the replacement of established methods to measure seawater carbonate chemistry, particularly for high-accuracy quantification of carbonate parameters in seawater such as open ocean chemistry, for real-time measures of ocean change, nor for the measurement of small changes in seawater pCO2. However, for biological CO2-manipulation experiments measuring differences of over 100 μatm pCO2 among treatments, we find the four methods described here can produce similar results with careful use. PMID:28957378

The Atmospheres of Directly Imaged Planets: Where Has All the Methane Gone?

NASA Technical Reports Server (NTRS)

Marley, Mark S.; Zahnle, Kevin

2014-01-01

Methane and ammonia both first appear at lower effective temperatures in brown dwarf atmospheres than equilibrium chemistry models would suggest. This has traditionally been understood as a consequence of vertical mixing timescales being shorter than chemical equilibration timescales in brown dwarf photospheres. Indeed the eddy diffusivity, a variable accounting for the vigor of vertical mixing, has become a standard part of the description of brown dwarf atmosphere models, along with Teff and log g. While some models have suggested that methane is less favored at lower gravity, the almost complete absence of methane in the atmospheres of directly imaged planets, such as those orbiting HR 8799, even at effective temperatures where methane is readily apparent in brown dwarf spectra, has been puzzling. To better understand the paucity of methane in low gravity atmospheres we have revisited the problem of methane chemistry and mixing. We employed a 1-D atmospheric chemistry code augmented with an updated and complete network of the chemical reactions that link CO to CH4. We find the methane abundance at altitudes at or above the effective photosphere is a strong function of surface gravity because higher g shifts the p-T structure to higher pressures (i.e., a given optical depth is proportional to p/g, a relation mitigated somewhat by pressure broadening). Thus quenching in more massive brown dwarfs occurs at a lower temperature and higher pressure, both favoring CH4. We predict that in the lowest mass young giant planets, methane will appear very late, at effective temperatures as low as 600 K rather than the 1200 K seen among field brown dwarfs. This methane deficiency has important implications for the interpretation of spectra as well as methane-based planetary companion searches, such as the NICI survey. The GPI and SPHERE surveys will test these ideas and probe atmospheric chemistry and composition in an entire new range of parameter space. A caveat is that these calculations presume that the C to O ratio is comfortably less than one; the behavior is quite different if C and O are equally abundant, and of course CH4 is always present if C exceeds O.

Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

PubMed Central

Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; van Driel, Tim B.; Adachi, Shin-ichi; Bordage, Amélie; Bressler, Christian; Chabera, Pavel; Christensen, Morten; Dohn, Asmus O.; Galler, Andreas; Gawelda, Wojciech; Gosztola, David; Haldrup, Kristoffer; Harlang, Tobias; Liu, Yizhu; Møller, Klaus B.; Németh, Zoltán; Nozawa, Shunsuke; Pápai, Mátyás; Sato, Tokushi; Sato, Takahiro; Suarez-Alcantara, Karina; Togashi, Tadashi; Tono, Kensuke; Uhlig, Jens; Vithanage, Dimali A.; Wärnmark, Kenneth; Yabashi, Makina; Zhang, Jianxin; Sundström, Villy; Nielsen, Martin M.

2015-01-01

Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined. PMID:25727920

Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

DOE PAGES

Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; ...

2015-03-02

Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances.more » Thus experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined.« less

Nucleophilic catalysis of acylhydrazone equilibration for protein-directed dynamic covalent chemistry

PubMed Central

Bhat, Venugopal T.; Caniard, Anne M.; Luksch, Torsten; Brenk, Ruth; Campopiano, Dominic J.; Greaney, Michael F.

2010-01-01

Dynamic covalent chemistry uses reversible chemical reactions to set up an equilibrating network of molecules at thermodynamic equilibrium, which can adjust its composition in response to any agent capable of altering the free energy of the system. When the target is a biological macromolecule, such as a protein, the process corresponds to the protein directing the synthesis of its own best ligand. Here, we demonstrate that reversible acylhydrazone formation is an effective chemistry for biological dynamic combinatorial library formation. In the presence of aniline as a nucleophilic catalyst, dynamic combinatorial libraries equilibrate rapidly at pH 6.2, are fully reversible, and may be switched on or off by means of a change in pH. We have interfaced these hydrazone dynamic combinatorial libraries with two isozymes from the glutathione S-transferase class of enzyme, and observed divergent amplification effects, where each protein selects the best-fitting hydrazone for the hydrophobic region of its active site. PMID:20489719

Control of the reversibility during boronic ester formation: application to the construction of ferrocene dimers and trimers.

PubMed

Ono, Kosuke; Tohyama, Yohei; Uchikura, Tatsuhiro; Kikuchi, Yuji; Fujii, Kotaro; Uekusa, Hidehiro; Iwasawa, Nobuharu

2017-02-14

Control of the reversibility during boronic ester formation from boronic acids and diols was found to be possible by choosing an appropriate solvent. As an example, ferrocene dimers and trimers were constructed by using tetrol 1 with an indacene framework, 1,1'-ferrocenediboronic acid 2, and ferrocenemonoboronic acid 4. When equimolar amounts of 1 and 2 were mixed in methanol under equilibrating conditions, two kinds of stacked ferrocene dimers homo- and hetero-3 were selectively obtained depending on the reaction time and both structures were determined by X-ray crystallographic analysis. On the other hand, the ferrocene trimer 7 was successfully constructed by stepwise assembly in the presence of anhydrous magnesium sulfate in acetone where the equilibration of boronic esters was suppressed, while no formation of ferrocene trimer 7 was detected when all components 1, 2 and 4 (2 : 1 : 2 ratio) for trimer 7 were mixed at a time in methanol under equilibrating conditions.

Thermochemistry and Kinetics of the Cl+O2 Association Reaction

NASA Technical Reports Server (NTRS)

Nicovich, J. M.; Kreutter, K. D.; Shackelford, C. J.; Wine, P. H.

1997-01-01

Laser flash photolysis of Cl2/O2 mixtures has been employed in conjunction with Cl((sup 2)P(sub 3/2)) detection by time-resolved fluorescence spectroscopy to investigate equilibration kinetics for the reactions Cl + O2 + O is in equilibrium with ClOO + O2 at temperatures of 181-200 K and O2 pressures of 15-40 Torr. The third-order rate coefficient for the association reaction at 186.5 +/- 5.5 K is (8.9 +/- 2.9) x 10(exp -33) cm(exp 6) molecule(exp -2) s(exp -1) and the equilibrium constant (K(p)) at 185.4 K is 18.9 atm(exp -1) (factor of 1.7 uncertainty). A third law analysis of our data leads to a value for the Cl-OO bond dissociation energy of 4.76 +/- 0.49 kcal mol(exp -1).

Headspace profiling of cocaine samples for intelligence purposes.

PubMed

Dujourdy, Laurence; Besacier, Fabrice

2008-08-06

A method for determination of residual solvents in illicit hydrochloride cocaine samples using static headspace-gas chromatography (HS-GC) associated with a storage computerized procedure is described for the profiling and comparison of seizures. The system involves a gas chromatographic separation of 18 occluded solvents followed by fully automatic data analysis and transfer to a PHP/MySQL database. First, a fractional factorial design was used to evaluate the main effects of some critical method parameters (salt choice, vial agitation intensity, oven temperature, pressurization and loop equilibration) on the results with a minimum of experiments. The method was then validated for tactical intelligence purposes (batch comparison) via several studies: selection of solvents and mathematical comparison tool, reproducibility and "cutting" influence studies. The decision threshold to determine the similarity of two samples was set and false positives and negatives evaluated. Finally, application of the method to distinguish geographical origins is discussed.

Kinetics of gas phase formic acid decomposition on platinum single crystal and polycrystalline surfaces

NASA Astrophysics Data System (ADS)

Detwiler, Michael D.; Milligan, Cory A.; Zemlyanov, Dmitry Y.; Delgass, W. Nicholas; Ribeiro, Fabio H.

2016-06-01

Formic acid dehydrogenation turnover rates (TORs) were measured on Pt(111), Pt(100), and polycrystalline Pt foil surfaces at a total pressure of 800 Torr between 413 and 513 K in a batch reactor connected to an ultra-high vacuum (UHV) system. The TORs, apparent activation energies, and reaction orders are not sensitive to the structure of the Pt surface, within the precision of the measurements. CO introduced into the batch reactor depressed the formic acid dehydrogenation TOR and increased the reaction's apparent activation energies on Pt(111) and Pt(100), consistent with behavior predicted by the Temkin equation. Two reaction mechanisms were explored which explain the formic acid decomposition mechanism on Pt, both of which include dissociative adsorption of formic acid, rate limiting formate decomposition, and quasi-equilibrated hydrogen recombination and CO adsorption. No evidence was found that catalytic supports used in previous studies altered the reaction kinetics or mechanism.

Nickel adsorption on chalk and calcite

NASA Astrophysics Data System (ADS)

Belova, D. A.; Lakshtanov, L. Z.; Carneiro, J. F.; Stipp, S. L. S.

2014-12-01

Nickel uptake from solution by two types of chalk and calcite was investigated in batch sorption studies. The goal was to understand the difference in sorption behavior between synthetic and biogenic calcite. Experiments at atmospheric partial pressure of CO2, in solutions equilibrated with calcite and chalk and pH ranging from 7.7 to 8.8, explored the influence of initial concentration and the amount and type of sorbent on Ni uptake. Adsorption increases with increased surface area and pH. A surface complexation model describes the data well. Stability constants for the Ni surface complex are log KNi = - 1.12 on calcite and log KNi = - 0.43 and - 0.50 on the two chalk samples. The study confirms that synthetic calcite and chalk both take up nickel, but Ni binds more strongly on the biogenic calcite than on inorganically precipitated, synthetic powder, because of the presence of trace amounts of polysaccharides and clay nanoparticles on the chalk surface.

Reproducibility of up-flow column percolation tests for contaminated soils

PubMed Central

Naka, Angelica; Sakanakura, Hirofumi; Kurosawa, Akihiko; Inui, Toru; Takeo, Miyuki; Inoba, Seiji; Watanabe, Yasutaka; Fujikawa, Takuro; Miura, Toshihiko; Miyaguchi, Shinji; Nakajou, Kunihide; Sumikura, Mitsuhiro; Ito, Kenichi; Tamoto, Shuichi; Tatsuhara, Takeshi; Chida, Tomoyuki; Hirata, Kei; Ohori, Ken; Someya, Masayuki; Katoh, Masahiko; Umino, Madoka; Negishi, Masanori; Ito, Keijiro; Kojima, Junichi; Ogawa, Shohei

2017-01-01

Up-flow column percolation tests are used at laboratory scale to assess the leaching behavior of hazardous substance from contaminated soils in a specific condition as a function of time. Monitoring the quality of these test results inter or within laboratory is crucial, especially if used for Environment-related legal policy or for routine testing purposes. We tested three different sandy loam type soils (Soils I, II and III) to determine the reproducibility (variability inter laboratory) of test results and to evaluate the difference in the test results within laboratory. Up-flow column percolation tests were performed following the procedure described in the ISO/TS 21268–3. This procedure consists of percolating solution (calcium chloride 1 mM) from bottom to top at a flow rate of 12 mL/h through softly compacted soil contained in a column of 5 cm diameter and 30 ± 5 cm height. Eluate samples were collected at liquid-to-solid ratio of 0.1, 0.2, 0.5, 1, 2, 5 and 10 L/kg and analyzed for quantification of the target elements (Cu, As, Se, Cl, Ca, F, Mg, DOC and B in this research). For Soil I, 17 institutions in Japan joined this validation test. The up-flow column experiments were conducted in duplicate, after 48 h of equilibration time and at a flow rate of 12 mL/h. Column percolation test results from Soils II and III were used to evaluate the difference in test results from the experiments conducted in duplicate in a single laboratory, after 16 h of equilibration time and at a flow rate of 36 mL/h. Overall results showed good reproducibility (expressed in terms of the coefficient of variation, CV, calculated by dividing the standard deviation by the mean), as the CV was lower than 30% in more than 90% of the test results associated with Soil I. Moreover, low variability (expressed in terms of difference between the two test results divided by the mean) was observed in the test results related to Soils II and III, with a variability lower than 30% in more than 88% of the cases for Soil II and in more than 96% of the cases for Soil III. We also discussed the possible factors that affect the reproducibility and variability in the test results from the up-flow column percolation tests. The low variability inter and within laboratory obtained in this research indicates that the ISO/TS 21268–3 can be successfully upgraded to a fully validated ISO standard. PMID:28582458

High yield expression and purification of equilibrative nucleoside transporter 7 (ENT7) from Arabidopsis thaliana.

PubMed

Girke, Christopher; Arutyunova, Elena; Syed, Maria; Traub, Michaela; Möhlmann, Torsten; Lemieux, M Joanne

2015-09-01

Equilibrative nucleoside transporters (ENTs) facilitate the import of nucleosides and their analogs into cells in a bidirectional, non-concentrative manner. However, in contrast to their name, most characterized plant ENTs act in a concentrative manner. A direct characterization of any ENT protein has been hindered due to difficulties in overexpression and obtaining pure recombinant protein. The equilibrative nucleoside transporter 7 from Arabidopsis thaliana (AtENT7) was expressed in Xenopus laevis oocytes to assess mechanism of substrate uptake. Recombinant protein fused to enhanced green fluorescent protein (eGFP) was expressed in Pichia pastoris to characterize its oligomeric state by gel filtration and substrate binding by microscale thermophoresis (MST). AtENT7 expressed in X. laevis oocytes works as a classic equilibrative transporter. The expression of AtENT7-eGFP in the P. pastoris system yielded milligram amounts of pure protein that exists as stable homodimers. The concentration dependent binding of purine and pyrimidine nucleosides to the purified recombinant protein, assessed by MST, confirmed that AtENT7-eGFP is properly folded. For the first time the binding of nucleobases was observed for AtENT7. The availability of pure recombinant AtENT7 will permit detailed kinetic and structural studies of this unique member of the ENT family and, given the functional similarity to mammalian ENTs, will serve as a good model for understanding the structural basis of translocation mechanism for the family. Copyright © 2015 Elsevier B.V. All rights reserved.

Ab initio/GIAO-CCSD(T) (13)C NMR study of the rearrangement and dynamic aspects of rapidly equilibrating tertiary carbocations, C6H13(+) and C7H15(+).

PubMed

Olah, George A; Prakash, G K Surya; Rasul, Golam

2016-01-05

The rearrangement pathways of the equilibrating tertiary carbocations, 2,3-dimethyl-2-butyl cation (C6H13(+), 1), 2,3,3-trimethyl-2-butyl cation (C7H15(+), 5) and 2,3-dimethyl-2-pentyl cation (C7H15(+), 8 and 9) were investigated using the ab initio/GIAO-CCSD(T) (13)C NMR method. Comparing the calculated and experimental (13)C NMR chemical shifts of a series of carbocations indicates that excellent prediction of δ(13)C could be achieved through scaling. In the case of symmetrical equilibrating cations (1 and 5) the Wagner-Meerwein 1,2-hydride and 1,2-methide shifts, respectively, produce the same structure. This indicates that the overall (13)C NMR chemical shifts are conserved and independent of temperature. However, in the case of unsymmetrical equilibrating cations (8 and 9) the Wagner-Meerwein shift produces different tertiary structures, which have slightly different thermodynamic stabilities and, thus, different spectra. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level structure 8 is only 90 calories/mol more stable than structure 9. Based on computed (13)C NMR chemical shift calculations, mole fractions of these isomers were determined by assuming the observed chemical shifts are due to the weighted average of the chemical shifts of the static ions. © 2015 Wiley Periodicals, Inc.

Development and clinical trial results of a prototype device for trans-cutaneous monitoring of kidney function

NASA Astrophysics Data System (ADS)

Debreczeny, Martin P.; Dorshow, Richard B.

2017-02-01

A prototype medical device for trans-cutaneous monitoring of kidney function has been developed, validated, and used in a clinical trial on 16 healthy subjects having a wide range of skin color types. The fluorescent tracer agent MB-102 was administered intravenously as a bolus that was varied between 0.5 and 4 μmole/kg subject weight. The tracer agent was tracked as a function of time in plasma by blood sampling and trans-cutaneously at four body sites (sternum, forehead, arm, and side) simultaneously. Excitation was performed with a very low level of amplitude-modulated LED light at 450 nm (<50 μW/cm2), and fluorescence emission was synchronously detected at 570 nm. With adjustment of detection gain between subjects, no skin color dependence was observed of the signal-to-noise ratio (SNR) of the transcutaneous measurements. The primary source of measurement noise appeared to be subject motion, likely due to variations in blood content at the skin measurement site. A typical two-compartment pharmacokinetic dependence was observed with equilibration of the fluorescent agent between the vascular space into which it was injected and the extracellular space into which it subsequently diffused. Variation of this equilibration time was observed across body sites, with the sternum providing the shortest and most consistent equilibration. After equilibration, the terminal fluorescence time dependence at the sternum site was found to be highly correlated with tracer agent concentration time dependence sampled from the blood plasma.

Probing the Interplay between Dendritic Spine Morphology and Membrane-Bound Diffusion.

PubMed

Adrian, Max; Kusters, Remy; Storm, Cornelis; Hoogenraad, Casper C; Kapitein, Lukas C

2017-11-21

Dendritic spines are protrusions along neuronal dendrites that harbor the majority of excitatory postsynapses. Their distinct morphology, often featuring a bulbous head and small neck that connects to the dendritic shaft, has been shown to facilitate compartmentalization of electrical and cytoplasmic signaling stimuli elicited at the synapse. The extent to which spine morphology also forms a barrier for membrane-bound diffusion has remained unclear. Recent simulations suggested that especially the diameter of the spine neck plays a limiting role in this process. Here, we examine the connection between spine morphology and membrane-bound diffusion through a combination of photoconversion, live-cell superresolution experiments, and numerical simulations. Local photoconversion was used to obtain the timescale of diffusive equilibration in spines and followed by global sparse photoconversion to determine spine morphologies with nanoscopic resolution. These morphologies were subsequently used to assess the role of morphology on the diffusive equilibration. From the simulations, we could determine a robust relation between the equilibration timescale and a generalized shape factor calculated using both spine neck width and neck length, as well as spine head size. Experimentally, we found that diffusive equilibration was often slower, but rarely faster than predicted from the simulations, indicating that other biological confounders further reduce membrane-bound diffusion in these spines. This shape-dependent membrane-bound diffusion in mature spines may contribute to spine-specific compartmentalization of neurotransmitter receptors and signaling molecules and thereby support long-term plasticity of synaptic contacts. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Species variation in osmotic, cryoprotectant, and cooling rate tolerance in poultry, eagle, and Peregrine Falcon spermatozoa

USGS Publications Warehouse

Blanco, J.M.; Gee, G.; Wildt, D.E.; Donoghue, A.M.

2000-01-01

Potential factors influencing spermatozoa survival to cryopreservation and thawing were analyzed across a range of the following avian species: domestic chicken (Gallus domesticus), domestic turkey (Meleagris gallopavo), golden eagle (Aquila chrysaetos), Bonelli's eagle (Hieraaetus fasciatus), imperial eagle (Aquila adalberti), and peregrine falcon (Falco peregrinus). Studies focused on spermatozoa tolerance to the following: 1) osmotic stress, 2) different extracellular concentrations of the cryoprotectant dimethylacetamide (DMA), 3) equilibration times of 1 versus 4 h, 4) equilibration temperature of 4 versus 21 degrees C, and 5) rapid versus slow cooling before cryopreservation and standard thawing. Sperm viability was assessed with the live/dead stain (SYBR14/ propidium iodine). Sperm viability at osmolalities >/=800 mOsm was higher (P: /=2.06 M), experienced decreased (P: < 0.05) spermatozoa survival in all species, except the golden eagle and peregrine falcon. Number of surviving spermatozoa diminished progressively with increasing DMA concentrations in all species. Increased equilibration temperature (from 4 to 21 degrees C) markedly reduced (P: < 0.05) spermatozoa survival in all species except the Bonelli's eagle and turkey. Rapid cooling was detrimental (P: < 0.05) to spermatozoa from all species except the imperial eagle and the chicken. These results demonstrate that avian spermatozoa differ remarkably in response to osmotic changes, DMA concentrations, equilibration time, temperature, and survival after fast or slow freezing. These differences emphasize the need for species-specific studies in the development and enhancement of assisted breeding for poultry and endangered species.

The consequences of crystal relaxation on CO2 partitioning in plagioclase-hosted melt inclusions

NASA Astrophysics Data System (ADS)

Drignon, M. J.; Nielsen, R.; Moore, L.; Bodnar, R. J.; Tepley, F. J., III; Kotash, A.

2017-12-01

Melt inclusions (MI) are samples of magmas representing the early stages of the development of the system, both spatially and compositionally. However, little work has been done to test and understand whether MI in plagioclase faithfully sample and maintain a record of the magmatic history. Here, we examine the effects of post entrapment processes such as sidewall crystallization (PEC) and crystal relaxation that may occur during transport and eruption and, thus alter the composition of MI. To better understand the effects of PEC and crystal relaxation, time-series experiments were conducted on plagioclase-hosted MI from plagioclase ultraphyric basalts to evaluate the extent of crystal relaxation. Run times ranged from 30 min to 4 days. To evaluate the magnitude of the effect, we analyzed the CO2 content in the vapor bubbles using Raman spectroscopy. CO2 in the MI glass was determined by SIMS. The working assumption was that relaxation would lead to a pressure drop within the MI leading to an increase in CO2 in the vapor bubbles as CO2 moved from the melt to the bubble. In addition, a drop in pressure was expected to affect the major element composition of the MI. Our results demonstrated that Na2O, CaO and Al2O3 in the MI decreased, and SiO2 and MgO increased as a function of run time. However, the magnitude of the changes cannot be explained by plagioclase melting alone. In addition, our preliminary data show more CO2 in the vapor bubbles after the 4 day runs than after 30 min runs. Using our SIMS data, and applying the total CO2 reconstruction methodology described in Moore et al. (2015), we estimate that 61% of the total CO2 in the MI is contained within the vapor bubbles after the 4 day runs and 37 % of the CO2 is in the vapor bubbles after 30 min. We hypothesize that after 4 days the CO2 exsolved from the melt into the vapor bubble and is not re-dissolved into the melt due to crystal relaxation and the concomitant pressure decrease in the MI. This suggests that plagioclase-hosted MI hold their volatiles after long runs. The total CO2 reconstruction indicates that the MI were trapped between 3000 and 6000 bars which correspond to 9-18 km. These pressures represent the pressures of last equilibration and suggest that plagioclase megacrysts crystallized in the upper mantle, and are not related to processes within or above the magma lens.

A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum.

PubMed

Sordo, Laura; Santos, Rui; Reis, Joao; Shulika, Alona; Silva, Joao

2016-01-01

Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO 2 . However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and p CO 2 . Here we describe a system in which the target p CO 2 is controlled via direct analysis of p CO 2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures p CO 2 and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO 2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of p CO 2 for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum . We found that after 11 months of high CO 2 exposure, photosynthesis increased with CO 2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO 2 , such as temperature, irradiance and nutrients.

A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum

PubMed Central

Santos, Rui; Reis, Joao; Shulika, Alona

2016-01-01

Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures pCO2 and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO2 for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO2 exposure, photosynthesis increased with CO2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO2, such as temperature, irradiance and nutrients. PMID:27703853

Performance characteristics of an ion chromatographic method for the quantitation of citrate and phosphate in pharmaceutical solutions.

PubMed

Jenke, Dennis; Sadain, Salma; Nunez, Karen; Byrne, Frances

2007-01-01

The performance of an ion chromatographic method for measuring citrate and phosphate in pharmaceutical solutions is evaluated. Performance characteristics examined include accuracy, precision, specificity, response linearity, robustness, and the ability to meet system suitability criteria. In general, the method is found to be robust within reasonable deviations from its specified operating conditions. Analytical accuracy is typically 100 +/- 3%, and short-term precision is not more than 1.5% relative standard deviation. The instrument response is linear over a range of 50% to 150% of the standard preparation target concentrations (12 mg/L for phosphate and 20 mg/L for citrate), and the results obtained using a single-point standard versus a calibration curve are essentially equivalent. A small analytical bias is observed and ascribed to the relative purity of the differing salts, used as raw materials in tested finished products and as reference standards in the analytical method. The assay is specific in that no phosphate or citrate peaks are observed in a variety of method-related solutions and matrix blanks (with and without autoclaving). The assay with manual preparation of the eluents is sensitive to the composition of the eluent in the sense that the eluent must be effectively degassed and protected from CO(2) ingress during use. In order for the assay to perform effectively, extensive system equilibration and conditioning is required. However, a properly conditioned and equilibrated system can be used to test a number of samples via chromatographic runs that include many (> 50) injections.

Experimental Investigation of Gas/Slag/Matte/Tridymite Equilibria in the Cu-Fe-O-S-Si System in Controlled Atmospheres: Development of Technique

NASA Astrophysics Data System (ADS)

Fallah-Mehrjardi, Ata; Hidayat, Taufiq; Hayes, Peter C.; Jak, Evgueni

2017-12-01

The majority of primary pyrometallurgical copper making processes involve the formation of two immiscible liquid phases, i.e., matte product and the slag phase. There are significant gaps and discrepancies in the phase equilibria data of the slag and the matte systems due to issues and difficulties in performing the experiments and phase analysis. The present study aims to develop an improved experimental methodology for accurate characterisation of gas/slag/matte/tridymite equilibria in the Cu-Fe-O-S-Si system under controlled atmospheres. The experiments involve high-temperature equilibration of synthetic mixtures on silica substrates in CO/CO2/SO2/Ar atmospheres, rapid quenching of samples into water, and direct composition measurement of the equilibrium phases using Electron Probe X-ray Microanalysis (EPMA). A four-point-test procedure was applied to ensure the achievement of equilibrium, which included the following: (i) investigation of equilibration as a function of time, (ii) assessment of phase homogeneity, (iii) confirmation of equilibrium by approaching from different starting conditions, and (iv) systematic analysis of the reactions specific to the system. An iterative improved experimental methodology was developed using this four-point-test approach to characterize the complex multi-component, multi-phase equilibria with high accuracy and precision. The present study is a part of a broader overall research program on the characterisation of the multi-component (Cu-Fe-O-S-Si-Al-Ca-Mg), multi-phase (gas/slag/matte/metal/solids) systems with minor elements (Pb, Zn, As, Bi, Sn, Sb, Ag, and Au).

Characterization of the Protein Crystal Growth Apparatus for Microgravity Aboard the Space Station

NASA Technical Reports Server (NTRS)

Kundrot, Craig E.; Roeber, D.; Achari, A.; Stinson, Thomas N. (Technical Monitor)

2002-01-01

We have conducted experiments to determine the equilibration rates of some major precipitants used in protein crystallography aboard the International Space Station (ISS). The solutions were placed in the Protein Crystallization Apparatus for Microgravity (PCAM) which mimic Cryschem sitting drop trays. The trays were placed in cylinders. These cylinders were placed inside a Single locker Thermal Enclosure System (STES), and were activated for different durations during the flight. Bumpers pressed against elastomers seal drops in a deactivated state during pre-flight and prior to transfer to the ISS. Activation occurs while in flight on the ISS by releasing the bumpers allowing the drops to be exposed to the reservoir. PCAM was flown to the ISS on STS 100, Flight 6A, on April 19, 2001. Six series of equilibration experiments were tested for each precipitant with a small amount of Green Fluorescent Protein (GFP). Cylinder 10 was never activated, 7 was activated for 40 days, 8 was activated for 20 days, 9 was activated for 10 days, 11 was activated for 4 days and 12 was activated for 2 days. Upon the return to Earth by STS 104 on July 24,2001 the samples were transferred to Marshall Space Flight Center. The samples were then brought to the lab and the volumes of each sample were measured.

Biomarkers of Exposure to Toxic Substances Volume 7: Identification of Potential Serum Protein Biomarkers Indicative of Low Level Kidney Degradation in Response to Toxin Exposures

DTIC Science & Technology

2009-05-01

equilibrated for 4 min with Buffer A with a flow rate of 1 mL/min at room temperature. Once the HPLC lines and MARS column were flushed and equilibrated...ul 4 ) FT mouse control HPLC 10 ul 9) E mouse control Spin Column 10 ul 5) E mouse control HPLC 10 ul 10) Blue MW Standard The distinct...of Low Level Kidney Degradation in Response to Toxin Exposures Christopher L. Woolard Camilla A. Mauzy Biosciences and Protection

Equilibration and nonclassicality of a double-well potential

NASA Astrophysics Data System (ADS)

Campbell, Steve; de Chiara, Gabriele; Paternostro, Mauro

2016-01-01

A double well loaded with bosonic atoms represents an ideal candidate to simulate some of the most interesting aspects in the phenomenology of thermalisation and equilibration. Here we report an exhaustive analysis of the dynamics and steady state properties of such a system locally in contact with different temperature reservoirs. We show that thermalisation only occurs ‘accidentally’. We further examine the nonclassical features and energy fluxes implied by the dynamics of the double-well system, thus exploring its finite-time thermodynamics in relation to the settlement of nonclassical correlations between the wells.

Stability limit of liquid water in metastable equilibrium with subsaturated vapors.

PubMed

Wheeler, Tobias D; Stroock, Abraham D

2009-07-07

A pure liquid can reach metastable equilibrium with its subsaturated vapor across an appropriate membrane. This situation is analogous to osmotic equilibrium: the reduced chemical potential of the dilute phase (the subsaturated vapor) is compensated by a difference in pressure between the phases. To equilibrate with subsaturated vapor, the liquid phase assumes a pressure that is lower than its standard vapor pressure, such that the liquid phase is metastable with respect to the vapor phase. For sufficiently subsaturated vapors, the liquid phase can even assume negative pressures. The appropriate membrane for this metastable equilibrium must provide the necessary mechanical support to sustain the difference in pressure between the two phases, limit nonhomogeneous mechanisms of cavitation, and resist the entry of the dilutant (gases) into the pure phase (liquid). In this article, we present a study of the limit of stability of liquid water--the degree of subsaturation at which the liquid cavitates--in this metastable state within microscale voids embedded in hydrogel membranes. We refer to these structures as vapor-coupled voids (VCVs). In these VCVs, we observed that liquid water cavitated when placed in equilibrium with vapors of activity aw,vapair

Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlüter, Steffen; Berg, Steffen; Li, Tianyi

2017-06-01

The relaxation dynamics toward a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces, andmore » relaxes the contact angle toward the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1–4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.« less

Time required for partial pressure of arterial oxygen equilibration during mechanical ventilation after a step change in fractional inspired oxygen concentration.

PubMed

Cakar, N; Tuŏrul, M; Demirarslan, A; Nahum, A; Adams, A; Akýncý, O; Esen, F; Telci, L

2001-04-01

To determine the time required for the partial pressure of arterial oxygen (PaO2) to reach equilibrium after a 0.20 increment or decrement in fractional inspired oxygen concentration (FIO2) during mechanical ventilation. A multi-disciplinary ICU in a university hospital. Twenty-five adult, non-COPD patients with stable blood gas values (PaO2/FIO2 > or = 180 on the day of the study) on pressure-controlled ventilation (PCV). Following a baseline PaO2 (PaO2b) measurement at FIO2 = 0.35, the FIO2 was increased to 0.55 for 30 min and then decreased to 0.35 without any other change in ventilatory parameters. Sequential blood gas measurements were performed at 3, 5, 7, 9, 11, 15, 20, 25 and 30 min in both periods. The PaO2 values measured at the 30th min after a step change in FIO2 (FIO2 = 0.55, PaO2[55] and FIO2 = 0.35, PaO2[35]) were accepted as representative of the equilibrium values for PaO2. Each patient's rise and fall in PaO2 over time, PaO2(t), were fitted to the following respective exponential equations: PaO2b + (PaO2[55]-PaO2b)(1-e-kt) and PaO2[55] + (PaO2[35]-PaO2[55])(e-kt) where "t" refers to time, PaO2[55] and PaO2[35] are the final PaO2 values obtained at a new FIO2 of 0.55 and 0.35, after a 0.20 increment and decrement in FIO2, respectively. Time constant "k" was determined by a non-linear fitting curve and 90% oxygenation times were defined as the time required to reach 90% of the final equilibrated PaO2 calculated by using the non-linear fitting curves. Time constant values for the rise and fall periods were 1.01 +/- 0.71 min-1, 0.69 +/- 0.42 min-1, respectively, and 90% oxygenation times for rises and falls in PaO2 periods were 4.2 +/- 4.1 min-1 and 5.5 +/- 4.8 min-1, respectively. There was no significant difference between the rise and fall periods for the two parameters (p > 0.05). We conclude that in stable patients ventilated with PCV, after a step change in FIO2 of 0.20, 5-10 min will be adequate for obtaining a blood gas sample to measure a PaO2 that will be representative of the equilibrium PaO2 value.

Petrological significance of high-pressure ultramafic xenoliths from ultrapotassic rocks of Central Italy

NASA Astrophysics Data System (ADS)

Conticelli, Sandro; Peccerillo, Angelo

1989-08-01

Two suites of ultramafic xenoliths have been found in ultrapotassic lavas from the 0.9 Ma old Torre Alfina volcano sited at the northern border of the Vulsinian district (Central Italy). One group of Xenoliths consists of spinel-bearing lherzolites, harzburgites, minor wherlites and dunites with a maximum size of 3-4 cm. Some samples contain discrete laths of phlogopite. A second class consists of phlogopite-rich, glass-bearing peridotites. The first suite displays textural characteristics such as triple points, deformed olivine with well developed kink banding and porphyroclastic textures indicating equilibration at high pressure. Pressure estimates give values in the range 1.3-2.5 GPa, corresponding to mantle depths in the area, where the present-day Moho is about 25 km deep. Equilibration temperatures have been estimated in the range between 950-1000°C. The chemical composition of some phases, such as the very high Fo contents of olivines (up to Fo 94 in harzburgites), Mg content of orthopyroxenes and {Cr}/{Cr}+Al ratios of clinopyroxenes and spinels, suggest that these xenoliths represent peridotites which suffered different degrees of partial melting before being incorporated into the Torre Alfina magma. On the other hand, the occurrence of phlogopite speaks for metasomatic events. The phlogopite-rich, glass-bearing xenoliths consist of phlogopite, olivine, clinopyroxene, rare orthopyroxene and glass. Apatite is the most common accessory. Olivine is present in both euhedral and strained crystals. A few relics of protogranular textures are also observed. Textural and chemical evidence suggests that these xenoliths represent mica-rich peridotites which have undergone phlogopite breakdown during rapid rise to the surface with the development of a K-rich liquid which reacted with mafic phases producing a rapid growth of olivine and, to a lower extent, pyroxene. Originally, these xenoliths may have represented intensively metasomatized upper mantle. However, a cumulitic origin from previous potassic magmatic events cannot be excluded. The host lavas have compositions intermediate between high-silica lamproite and Roman-type ultrapotassic rock. They have high abundances of incompatible elements and radiogenic Sr, coupled with high Mg content, {MgO}/{CaO}, Ni and Cr. These features support a genesis in a residual upper mantle which has suffered partial melting with the extraction of basaltic liquids, followed by metasomatic events which caused an enrichment in incompatible elements and radiogenic Sr. The presence of mantle-derived ultramafic xenoliths in the torre Alfina lavas testifies for a rapid uprise of the magma which reached the surface without suffering fractional crystallization and significant interaction with the upper crust. Accordingly, the Torre Alfina lavas represent an unique example of primitive potassic liquid in Central Italy.

Petrological significance of high-pressure ultramafic xenoliths from ultrapotassic rocks of Central Italy

NASA Astrophysics Data System (ADS)

Conticelli, Sandro; Peccerillo, Angelo

1990-08-01

Two suites of ultramafic xenoliths have been found in ultrapotassic lavas from the 0.9 Ma old Torre Alfina volcano sited at the northern border of the Vulsinian district (Central Italy). One group of Xenoliths consists of spinel-bearing lherzolites, harzburgites, minor wherlites and dunites with a maximum size of 3-4 cm. Some samples contain discrete laths of phlogopite. A second class consists of phlogopite-rich, glass-bearing peridotites. The first suite displays textural characteristics such as triple points, deformed olivine with well developed kink banding and porphyroclastic textures indicating equilibration at high pressure. Pressure estimates give values in the range 1.3-2.5 GPa, corresponding to mantle depths in the area, where the present-day Moho is about 25 km deep. Equilibration temperatures have been estimated in the range between 950-1000°C. The chemical composition of some phases, such as the very high Fo contents of olivines (up to Fo94 in harzburgites), Mg content of orthopyroxenes and {Cr}/{Cr}+Al ratios of clinopyroxenes and spinels, suggest that these xenoliths represent peridotites which suffered different degrees of partial melting before being incorporated into the Torre Alfina magma. On the other hand, the occurrence of phlogopite speaks for metasomatic events. The phlogopite-rich, glass-bearing xenoliths consist of phlogopite, olivine, clinopyroxene, rare orthopyroxene and glass. Apatite is the most common accessory. Olivine is present in both euhedral and strained crystals. A few relics of protogranular textures are also observed. Textural and chemical evidence suggests that these xenoliths represent mica-rich peridotites which have undergone phlogopite breakdown during rapid rise to the surface with the development of a K-rich liquid which reacted with mafic phases producing a rapid growth of olivine and, to a lower extent, pyroxene. Originally, these xenoliths may have represented intensively metasomatized upper mantle. However, a cumulitic origin from previous potassic magmatic events cannot be excluded. The host lavas have compositions intermediate between high-silica lamproite and Roman-type ultrapotassic rock. They have high abundances of incompatible elements and radiogenic Sr, coupled with high Mg content, {MgO}/{CaO}, Ni and Cr. These features support a genesis in a residual upper mantle which has suffered partial melting with the extraction of basaltic liquids, followed by metasomatic events which caused an enrichment in incompatible elements and radiogenic Sr. The presence of mantle-derived ultramafic xenoliths in the torre Alfina lavas testifies for a rapid uprise of the magma which reached the surface without suffering fractional crystallization and significant interaction with the upper crust. Accordingly, the Torre Alfina lavas represent an unique example of primitive potassic liquid in Central Italy.

Si and O partitioning between core metal and lower mantle minerals during core formation

NASA Astrophysics Data System (ADS)

Nakajima, Y.; Frost, D. J.; Rubie, D. C.

2010-12-01

In addition to Fe and Ni, the Earth’s core contains light alloying elements (e.g., H, C, O, Si, and/or S) in order to explain the 10% core density deficit (e.g., Birch, 1964, JGR). Experimental data on the partitioning behavior of siderophile elements such as Ni and Co between liquid Fe and mantle minerals indicate that equilibration between core-forming metal and a silicate magma ocean likely occurred at lower-mantle pressures (e.g., Li and Agee, 1996 Nature). If core-mantle differentiation has occurred under such conditions, significant quantities of O or Si could have entered the core. At these conditions the nature of the dominant light element in the core will depend strongly on the oxygen fugacity at which equilibration occurred. High pressure experiments were carried out at 25 GPa and 2400-2950 K using a Kawai-type multi-anvil apparatus in order to investigate the partitioning of Si and O between liquid Fe and (Mg,Fe)SiO3 perovskite (Pv), silicate melt, and (Mg,Fe)O ferropericlace (Fp). Starting materials consisting of metallic Fe (+-Si) and olivine (Fo70-95) were contained in single-crystal MgO capsules. Over the oxygen fugacity range IW-0.5 to -3, the Si molar partition coefficient D* (= [Si]metal /[Si]silicate) between metal and Pv increases linearly with decreasing oxygen fugacity at a fixed given temperature. The partition coefficient between metal and silicate melt is of a similar magnitude but is less dependent on the oxygen fugacity. The obtained oxygen distribution coefficient Kd (= [Fe]metal[O]metal /[FeO]Fp) is in agreement with that determined in the Fe-Fp binary system (Asahara et al., 2007 EPSL) below the silicate liquidus temperature. In contrast, a correlation between the O partitioning and Si concentration in Fe is observed above 2700 K where liquid metal coexists with silicate melt + Fp. With an increasing concentration of Si in the liquid metal, O partitioning into Fp is strongly enhanced. Five atomic% Si in the metal reduces the metal-silicate O partition coefficient by about 1 order magnitude. Near the base of a deep magma ocean where pressures exceed 20 GPa, liquid metal could have coexisted with silicate melt, Pv, and Fp. Our results show that Si would readily partitioned into core-forming metal from both perovskite and silicate liquid at a relevant oxygen fugacity (e.g., IW-2). Simultaneously, the Si solubility would hinder the dissolution of O in the liquid metal. This implies that the presence of Si in liquid metal must be included in models of O partitioning.

Time-dependent deformation of gas shales - role of rock framework versus reservoir fluids

NASA Astrophysics Data System (ADS)

Hol, Sander; Zoback, Mark

2013-04-01

Hydraulic fracturing operations are generally performed to achieve a fast, drastic increase of permeability and production rates. Although modeling of the underlying short-term mechanical response has proven successful via conventional geomechanical approaches, predicting long-term behavior is still challenging as the formation interacts physically and chemically with the fluids present in-situ. Recent experimental work has shown that shale samples subjected to a change in effective stress deform in a time-dependent manner ("creep"). Although the magnitude and nature of this behavior is strongly related to the composition and texture of the sample, also the choice of fluid used in the experiments affects the total strain response - strongly adsorbing fluids result in more, recoverable creep. The processes underlying time-dependent deformation of shales under in-situ stresses, and the long-term impact on reservoir performance, are at present poorly understood. In this contribution, we report triaxial mechanical tests, and theoretical/thermodynamic modeling work with the aim to identify and describe the main mechanisms that control time-dependent deformation of gas shales. In particular, we focus on the role of the shale solid framework versus the type and pressure of the present pore fluid. Our experiments were mainly performed on Eagle Ford Shale samples. The samples were subjected to cycles of loading and unloading, first in the dry state, and then again after equilibrating them with (adsorbing) CO2 and (non-adsorbing) He at fluid pressures of 4 MPa. Stresses were chosen close to those persisting under in-situ conditions. The results of our tests demonstrate that likely two main types of deformation mechanisms operate that relate to a) the presence of microfractures as a dominating feature in the solid framework of the shale, and b) the adsorbing potential of fluids present in the nanoscale voids of the shale. To explain the role of adsorption in the observed compaction creep, we postulate a serial coupling between 1) stress-driven desorption of the fluid species, 2) diffusion of the desorbed species out of the solid, and 3) consequent shrinkage. We propose a model in which the total shrinkage of the solid (Step 3) that is measured as bulk compaction, is driven by a change in stress state (Step 1), and evolves in time controlled by the diffusion characteristics of the system (Step 2). Our experimental and modeling study shows that both the nature of the solid framework of the shale, as well as the type and pressure of pore fluids affect the long-term in-situ mechanical behavior of gas shale reservoirs.

The stability of chalk during flooding of carbonated sea water at reservoir in-situ conditions

NASA Astrophysics Data System (ADS)

Nermoen, Anders; Korsnes, Reidar I.; Madland, Merete V.

2014-05-01

Injection of CO2 into carbonate oil reservoirs has been proposed as a possible utilization of the captured CO2 due to its capability to enhance the oil recovery. For offshore reservoirs such as Ekofisk and Valhall it has been discussed to alternate the CO2 and sea water injection (WAG) to reduce costs and keep the beneficial effects of both sea water (SSW) and gas injection. Water and CO2 mix to form carbonic acids that enhance the solubility of carbonates, thus a serious concern has been raised upon the potential de-stabilization of the reservoirs during CO2 injection. In this study we focus on how carbonated sea water alters the mechanical integrity of carbonate rocks both to evaluate safety of carbon storage sites and in the planning of production strategies in producing oil fields since enhanced compaction may have both detrimental and beneficial effects. Here we will present results from long term experiments (approx. half year each) performed on Kansas outcrop chalk (38-41% porosity), which serves as model material to understand the physical and chemical interplaying processes taking place in chalk reservoirs. All tests are performed at uni-axial strain conditions, meaning that the confining radial stresses are automatically adjusted to ensure zero radial strain. The tests are performed at in-situ conditions and run through a series of stages that mimic the reservoir history at both Ekofisk and Valhall fields. We observe the strain response caused by the injected brine. The experimental stages are: (a) axial stress build-up by pore pressure depletion to stresses above yield with NaCl-brine which is inert to the chalk; (b) uni-axial creep at constant axial stresses with NaCl-brine; (c) sea water injection; and (d) injection of carbonated water (SSW+CO2) at various mixture concentrations. Two test series were performed in which the pore pressure was increased (re-pressurized) before stage (c) to explore the stress dependency of the fluid induced strain triggering. The main findings of our investigations are: 1. The creep rate in the plastic phase is pore fluid dependent. The injection of sea water induces a period of accelerating creep. 2. The injection of CO2 and sea water reduces the deformation rate, a result which is in contrast to what has previously been shown. 3. The solid weight of the plugs is maintained during flooding which indicates that the observed carbonate dissolution at the inlet side is counteracted with secondary precipitation, possibly calcium sulphate, within the plug. These recent obtained results show that chalk cores maintain their mechanical integrity during flooding of carbonated water. This experimental study, however, separates from earlier studies by the low injection rate which allows secondary precipitation processes to equilibrate within the plugs, chalk type, test temperature, and stress conditions, which all are factors that will affect the reported dynamics.

The stability of hibonite, melilite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions from carbonaceous chondrites

NASA Technical Reports Server (NTRS)

Beckett, J. R.; Stolper, E.

1994-01-01

Phase fields in which hibonite and silicate melt coexist with spinel CaAl4O7, gehlenitic melilite, anorthite or corundum at 1 bar in the system CaO-MgO-Al2O3-SiO2-TiO2 were determined. The hibonites contain up to 1.7 wt% SiO2. For TiO2, the experimentally determined partition coefficients between hibonite and coexisting melt D(sub i)(sup Hib/L), vary from 0.8 to 2.1 and generally decrease with increasing TiO2 in the liquid. Based on Ti partitioning between hibonite and melt, bulk inclusion compositions and hibonite-saturated liquidus phase diagrams, the hibonite in hibonite-poor fluffy Type A inclusions from Allende and at least some hibonite from hibonite-rich inclusions is relict, although much of the hibonite from hibonite-glass spherules probably crystallized metasably from a melt. Bulk compositions for all of these CAIs are consistent with an origin as melite + hibonite + spinel + perovskite phase assembalges that were partially altered and in some cases partially or completely melted. The duration of the melting event was sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. Simple thermochemical models developed for meteoritic melilite and hibonite solid solutions were used to obtain equilibration temperatures of hibonite-bearing phase assemblages with vapor. Referenced to 10(exp -3) atm, hibonite + corundum + vapor equilibrated at approximately 1260 C and hibonite + spinel +/- melilite + vapor at 1215 +/- 10 C. If these temperatures reflect condensation in a cooling gas of solar composition, then hibonite +/- corundum condensed first, followed by spinel and then melilite. The position of perovskite within this sequence is uncertain, but it probably began to condense before spinel. This sequence of phase appearances and relative temperatures is generally consistent with observed textures but differs from expectations based on classical condensation calculations in that equilibration temperatures are generally lower than predicted and melilite initially condenses with or even after spinel. Simple thermochemical modes for the substitution of trace elements into the Ca site of meteoritic hibonites suggest that virtually all Eu is divalent in early condensate hibonites but that Eu(2+)/Eu(#+) decreases by a factor of 20 or more during the course of condensation primarily because the ratio is proportional to the partial pressure of Al, which decreases dramatically as aluminous phase condense. The relative sizes of Eu and Yb anomalies in meteoritic hibonites and inclusions may be partly due to this effect.

Trapping Dynamics in Photosystem I-Light Harvesting Complex I of Higher Plants Is Governed by the Competition Between Excited State Diffusion from Low Energy States and Photochemical Charge Separation.

PubMed

Molotokaite, Egle; Remelli, William; Casazza, Anna Paola; Zucchelli, Giuseppe; Polli, Dario; Cerullo, Giulio; Santabarbara, Stefano

2017-10-26

The dynamics of excited state equilibration and primary photochemical trapping have been investigated in the photosystem I-light harvesting complex I isolated from spinach, by the complementary time-resolved fluorescence and transient absorption approaches. The combined analysis of the experimental data indicates that the excited state decay is described by lifetimes in the ranges of 12-16 ps, 32-36 ps, and 64-77 ps, for both detection methods, whereas faster components, having lifetimes of 550-780 fs and 4.2-5.2 ps, are resolved only by transient absorption. A unified model capable of describing both the fluorescence and the absorption dynamics has been developed. From this model it appears that the majority of excited state equilibration between the bulk of the antenna pigments and the reaction center occurs in less than 2 ps, that the primary charge separated state is populated in ∼4 ps, and that the charge stabilization by electron transfer is completed in ∼70 ps. Energy equilibration dynamics associated with the long wavelength absorbing/emitting forms harbored by the PSI external antenna are also characterized by a time mean lifetime of ∼75 ps, thus overlapping with radical pair charge stabilization reactions. Even in the presence of a kinetic bottleneck for energy equilibration, the excited state dynamics are shown to be principally trap-limited. However, direct excitation of the low energy chlorophyll forms is predicted to lengthen significantly (∼2-folds) the average trapping time.

Equilibration and analysis of first-principles molecular dynamics simulations of water

NASA Astrophysics Data System (ADS)

Dawson, William; Gygi, François

2018-03-01

First-principles molecular dynamics (FPMD) simulations based on density functional theory are becoming increasingly popular for the description of liquids. In view of the high computational cost of these simulations, the choice of an appropriate equilibration protocol is critical. We assess two methods of estimation of equilibration times using a large dataset of first-principles molecular dynamics simulations of water. The Gelman-Rubin potential scale reduction factor [A. Gelman and D. B. Rubin, Stat. Sci. 7, 457 (1992)] and the marginal standard error rule heuristic proposed by White [Simulation 69, 323 (1997)] are evaluated on a set of 32 independent 64-molecule simulations of 58 ps each, amounting to a combined cumulative time of 1.85 ns. The availability of multiple independent simulations also allows for an estimation of the variance of averaged quantities, both within MD runs and between runs. We analyze atomic trajectories, focusing on correlations of the Kohn-Sham energy, pair correlation functions, number of hydrogen bonds, and diffusion coefficient. The observed variability across samples provides a measure of the uncertainty associated with these quantities, thus facilitating meaningful comparisons of different approximations used in the simulations. We find that the computed diffusion coefficient and average number of hydrogen bonds are affected by a significant uncertainty in spite of the large size of the dataset used. A comparison with classical simulations using the TIP4P/2005 model confirms that the variability of the diffusivity is also observed after long equilibration times. Complete atomic trajectories and simulation output files are available online for further analysis.

Evaluation of a self-equilibrium cutting strategy for the contour method of residual stress measurement

DOE PAGES

Muránsky, Ondrej; Hamelin, Cory J.; Hosseinzadeh, F.; ...

2017-04-06

An assessment of cutting-induced plasticity (CIP) is performed, by finite element (FE) prediction of the plastic strain accumulation along the cut tip when the EDM wire sections the NeT TG4 weld benchmark specimen along two cutting directions. The first direction corresponds to a conventional (C) cutting strategy, whereby the EDM wire cuts through the thickness of the weld specimen and travels in a direction transverse to the weld. The second direction corresponds to a self-equilibrating cutting (SE) strategy, whereby the EDM wire cuts across the transverse direction of the weld specimens and travels through the thickness of the plate. Themore » cutting thus progresses simultaneously through the compression-tension-compression regions of present weld residual stress (WRS) field. This type of cutting strategy is believed to minimize the CIP by minimising residual stress redistribution during cutting, due to stress equilibration across the sectioned material. The simulated cutting procedures are conducted under a range of clamping conditions to assess whether mechanical restraint has a primary or secondary influence on CIP accumulation. Both predictions of CIP and the resultant back-calculated WRS demonstrate that (i) mechanical restraint is the primary variable influencing CIP development, and (ii) under no circumstance does a self-equilibrating cutting strategy perform significantly better than a conventional cutting approach. Furthermore, the reason that self-equilibrating cuts are not effective is illustrated by calculating the Mode I (K I) stress intensity factor (SIF) along the cut tip, and correlating trends in K I to CIP development.« less

Evaluation of a self-equilibrium cutting strategy for the contour method of residual stress measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muránsky, Ondrej; Hamelin, Cory J.; Hosseinzadeh, F.

An assessment of cutting-induced plasticity (CIP) is performed, by finite element (FE) prediction of the plastic strain accumulation along the cut tip when the EDM wire sections the NeT TG4 weld benchmark specimen along two cutting directions. The first direction corresponds to a conventional (C) cutting strategy, whereby the EDM wire cuts through the thickness of the weld specimen and travels in a direction transverse to the weld. The second direction corresponds to a self-equilibrating cutting (SE) strategy, whereby the EDM wire cuts across the transverse direction of the weld specimens and travels through the thickness of the plate. Themore » cutting thus progresses simultaneously through the compression-tension-compression regions of present weld residual stress (WRS) field. This type of cutting strategy is believed to minimize the CIP by minimising residual stress redistribution during cutting, due to stress equilibration across the sectioned material. The simulated cutting procedures are conducted under a range of clamping conditions to assess whether mechanical restraint has a primary or secondary influence on CIP accumulation. Both predictions of CIP and the resultant back-calculated WRS demonstrate that (i) mechanical restraint is the primary variable influencing CIP development, and (ii) under no circumstance does a self-equilibrating cutting strategy perform significantly better than a conventional cutting approach. Furthermore, the reason that self-equilibrating cuts are not effective is illustrated by calculating the Mode I (K I) stress intensity factor (SIF) along the cut tip, and correlating trends in K I to CIP development.« less

Equilibration and analysis of first-principles molecular dynamics simulations of water.

PubMed

Dawson, William; Gygi, François

2018-03-28

First-principles molecular dynamics (FPMD) simulations based on density functional theory are becoming increasingly popular for the description of liquids. In view of the high computational cost of these simulations, the choice of an appropriate equilibration protocol is critical. We assess two methods of estimation of equilibration times using a large dataset of first-principles molecular dynamics simulations of water. The Gelman-Rubin potential scale reduction factor [A. Gelman and D. B. Rubin, Stat. Sci. 7, 457 (1992)] and the marginal standard error rule heuristic proposed by White [Simulation 69, 323 (1997)] are evaluated on a set of 32 independent 64-molecule simulations of 58 ps each, amounting to a combined cumulative time of 1.85 ns. The availability of multiple independent simulations also allows for an estimation of the variance of averaged quantities, both within MD runs and between runs. We analyze atomic trajectories, focusing on correlations of the Kohn-Sham energy, pair correlation functions, number of hydrogen bonds, and diffusion coefficient. The observed variability across samples provides a measure of the uncertainty associated with these quantities, thus facilitating meaningful comparisons of different approximations used in the simulations. We find that the computed diffusion coefficient and average number of hydrogen bonds are affected by a significant uncertainty in spite of the large size of the dataset used. A comparison with classical simulations using the TIP4P/2005 model confirms that the variability of the diffusivity is also observed after long equilibration times. Complete atomic trajectories and simulation output files are available online for further analysis.

Giant Linear Nonreciprocity, Zero Reflection, and Zero Band Gap in Equilibrated Space-Time-Varying Media

NASA Astrophysics Data System (ADS)

Taravati, Sajjad

2018-06-01

This article presents a class of space-time-varying media with giant linear nonreciprocity, zero space-time local reflections, and zero photonic band gap. This is achieved via equilibrium in the electric and magnetic properties of unidirectionally space-time-modulated media. The enhanced nonreciprocity is accompanied by a larger sonic regime interval which provides extra design freedom for achieving strong nonreciprocity by a weak pumping strength. We show that the width of photonic band gaps in general periodic space-time permittivity- and permeability-modulated media is proportional to the absolute difference between the electric and magnetic pumping strengths. We derive a rigorous analytical solution for investigation of wave propagation and scattering from general periodic space-time permittivity- and permeability-modulated media. In contrast with weak photonic transitions, from the excited mode to its two adjacent modes, in conventional space-time permittivity-modulated media, in an equilibrated space-time-varying medium, strong photonic transitions occur from the excited mode to its four adjacent modes. We study the enhanced nonreciprocity and zero band gap in equilibrated space-time-modulated media by analysis of their dispersion diagrams. In contrast to conventional space-time permittivity-modulated media, equilibrated space-time media exhibit different phase and group velocities for forward and backward harmonics. Furthermore, the numerical simulation scheme of general space-time permittivity- and permeability-modulated media is presented, which is based on the finite-difference time-domain technique. Our analytical and numerical results provide insights into general space-time refractive-index-modulated media, paving the way toward optimal isolators, nonreciprocal integrated systems, and subharmonic frequency generators.

Radionuclide Sensors and Systems for Monitoring Technetium-99 and Strontium-90 in Groundwater at the Hanford Site

NASA Astrophysics Data System (ADS)

Grate, J. W.; O'Hara, M. J.; Egorov, O. B.; Burge, S. R.

2009-12-01

We have developed automated sensor and analyzer devices for detection and monitoring of trace radionuclides in water, using preconcentrating columns and radiometric detection. The preconcentrating minicolumn sensor concept combines selective capture and detection in a single functional unit, where the column contains tens to hundreds of milligrams of selectively sorbent material, and the entire column content is monitored with a radiometric detector. Compared to thin film sensors with a few microgram of sorbent, this approach achieves tremendous preconcentration with efficient mass transport via pumping. Furthermore, in an equilibration-based mode of operation, the preconcentration by the sensor is maximized while eliminating the need for consumable reagents to regenerate the column; it can simply be re-equilibrated. We have demonstrated quantification of radionuclides such as technetium-99 to levels below drinking water standards in an equilibration-based process that produces steady state signals, signal proportional to concentration, and easy re-equilibration to new concentration levels. Alternatively, analyzers can be developed with separate separation and detection units that are fluidically linked. We have demonstrated detection of strontium-90 to levels below drinking water standards by this approach. We are developing autonomous systems for at-site monitoring on the Hanford Site in Washington State, using the fluidic sensor and analyzer methods, with the aim of monitoring natural and accelerated attenuation processes, remediation and barrier performance, and contaminant fluxes in the environment. Figure 1. The strontium-90 monitoring method deployed as part of the Burge Environmental Universal Sensor Platform, shown on the shores of the Columbia River on the Hanford site in Washington State.

Massively Parallel Simulations of Diffusion in Dense Polymeric Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faulon, Jean-Loup, Wilcox, R.T.

1997-11-01

An original computational technique to generate close-to-equilibrium dense polymeric structures is proposed. Diffusion of small gases are studied on the equilibrated structures using massively parallel molecular dynamics simulations running on the Intel Teraflops (9216 Pentium Pro processors) and Intel Paragon(1840 processors). Compared to the current state-of-the-art equilibration methods this new technique appears to be faster by some orders of magnitude.The main advantage of the technique is that one can circumvent the bottlenecks in configuration space that inhibit relaxation in molecular dynamics simulations. The technique is based on the fact that tetravalent atoms (such as carbon and silicon) fit in themore » center of a regular tetrahedron and that regular tetrahedrons can be used to mesh the three-dimensional space. Thus, the problem of polymer equilibration described by continuous equations in molecular dynamics is reduced to a discrete problem where solutions are approximated by simple algorithms. Practical modeling applications include the constructing of butyl rubber and ethylene-propylene-dimer-monomer (EPDM) models for oxygen and water diffusion calculations. Butyl and EPDM are used in O-ring systems and serve as sealing joints in many manufactured objects. Diffusion coefficients of small gases have been measured experimentally on both polymeric systems, and in general the diffusion coefficients in EPDM are an order of magnitude larger than in butyl. In order to better understand the diffusion phenomena, 10, 000 atoms models were generated and equilibrated for butyl and EPDM. The models were submitted to a massively parallel molecular dynamics simulation to monitor the trajectories of the diffusing species.« less

In situ study at high pressure and temperature of the environment of water in hydrous Na and Ca aluminosilicate melts and coexisting aqueous fluids

NASA Astrophysics Data System (ADS)

Le Losq, Charles; Dalou, Célia; Mysen, Bjorn O.

2017-07-01

The bonding and speciation of water dissolved in Na silicate and Na and Ca aluminosilicate melts were inferred from in situ Raman spectroscopy of the samples, in hydrothermal diamond anvil cells, while at crustal temperature and pressure conditions. Raman data were also acquired on Na silicate and Na and Ca aluminosilicate glasses, quenched from hydrous melts equilibrated at high temperature and pressure in a piston cylinder apparatus. In the hydrous melts, temperature strongly influences O-H stretching ν(O-H) signals, reflecting its control on the bonding of protons between different molecular complexes. Pressure and melt composition effects are much smaller and difficult to discriminate with the present data. However, the chemical composition of the melt + fluid system influences the differences between the ν(O-H) signals from the melts and the fluids and, hence, between their hydrogen partition functions. Quenching modifies the O-H stretching signals: strong hydrogen bonds form in the glasses below the glass transition temperature Tg, and this phenomenon depends on glass composition. Therefore, glasses do not necessarily record the O-H stretching signal shape in melts near Tg. The melt hydrogen partition function thus cannot be assessed with certainty using O-H stretching vibration data from glasses. From the present results, the ratio of the hydrogen partition functions of hydrous silicate melts and aqueous fluids mostly depends on temperature and the bulk melt + fluid system chemical composition. This implies that the fractionation of hydrogen isotopes between magmas and aqueous fluids in water-saturated magmatic systems with differences in temperature and bulk chemical composition will be different.

The effect of elevated methane pressure on methane hydrate dissociation

USGS Publications Warehouse

Circone, S.; Stern, L.A.; Kirby, S.H.

2004-01-01

Methane hydrate, equilibrated at P, T conditions within the hydrate stability field, was rapidly depressurized to 1.0 or 2.0 MPa and maintained at isobaric conditions outside its stability field, while the extent and rate of hydrate dissociation was measured at fixed, externally maintained temperatures between 250 and 288 K. The dissociation rate decreases with increasing pressure at a given temperature. Dissociation rates at 1.0 MPa parallel the complex, reproducible T-dependence previously observed between 250 and 272 K at 0.1 MPa. The lowest rates were observed near 268 K, such that >50% of the sample can persist for more than two weeks at 0.1 MPa to more than a month at 1 and 2 MPa. Varying the pressure stepwise in a single experiment increased or decreased the dissociation rate in proportion to the rates observed in the isobaric experiments, similar to the rate reversibility previously observed with stepwise changes in temperature at 0.1 MPa. At fixed P, T conditions, the rate of methane hydrate dissociation decreases monotonically with time, never achieving a steady rate. The relationship between time (t) and the extent of hydrate dissociation is empirically described by: Evolved gas (%) = A??tB where the pre-exponential term A ranges from 0 to 16% s-B and the exponent B is generally <1. Based on fits of the dissociation results to Equation 1 for the full range of temperatures (204 to 289 K) and pressures (0.1 to 2.0 MPa) investigated, the derived parameters can be used to predict the methane evolution curves for pure, porous methane hydrate to within ??5%. The effects of sample porosity and the presence of quartz sand and seawater on methane hydrate dissociation are also described using Equation 1.

Fault compaction and overpressured faults: results from a 3-D model of a ductile fault zone

NASA Astrophysics Data System (ADS)

Fitzenz, D. D.; Miller, S. A.

2003-10-01

A model of a ductile fault zone is incorporated into a forward 3-D earthquake model to better constrain fault-zone hydraulics. The conceptual framework of the model fault zone was chosen such that two distinct parts are recognized. The fault core, characterized by a relatively low permeability, is composed of a coseismic fault surface embedded in a visco-elastic volume that can creep and compact. The fault core is surrounded by, and mostly sealed from, a high permeability damaged zone. The model fault properties correspond explicitly to those of the coseismic fault core. Porosity and pore pressure evolve to account for the viscous compaction of the fault core, while stresses evolve in response to the applied tectonic loading and to shear creep of the fault itself. A small diffusive leakage is allowed in and out of the fault zone. Coseismically, porosity is created to account for frictional dilatancy. We show in the case of a 3-D fault model with no in-plane flow and constant fluid compressibility, pore pressures do not drop to hydrostatic levels after a seismic rupture, leading to an overpressured weak fault. Since pore pressure plays a key role in the fault behaviour, we investigate coseismic hydraulic property changes. In the full 3-D model, pore pressures vary instantaneously by the poroelastic effect during the propagation of the rupture. Once the stress state stabilizes, pore pressures are incrementally redistributed in the failed patch. We show that the significant effect of pressure-dependent fluid compressibility in the no in-plane flow case becomes a secondary effect when the other spatial dimensions are considered because in-plane flow with a near-lithostatically pressured neighbourhood equilibrates at a pressure much higher than hydrostatic levels, forming persistent high-pressure fluid compartments. If the observed faults are not all overpressured and weak, other mechanisms, not included in this model, must be at work in nature, which need to be investigated. Significant leakage perpendicular to the fault strike (in the case of a young fault), or cracks hydraulically linking the fault core to the damaged zone (for a mature fault) are probable mechanisms for keeping the faults strong and might play a significant role in modulating fault pore pressures. Therefore, fault-normal hydraulic properties of fault zones should be a future focus of field and numerical experiments.

Dynamic Dilational Strengthening During Earthquakes in Saturated Gouge-Filled Fault Zones

NASA Astrophysics Data System (ADS)

Sparks, D. W.; Higby, K.

2016-12-01

The effect of fluid pressure in saturated fault zones has been cited as an important factor in the strength and slip-stability of faults. Fluid pressure controls the effective normal stress across the fault and therefore controls the faults strength. In a fault core consisting of granular fault gouge, local transient dilations and compactions occur during slip that dynamically change the fluid pressure. We use a grain-scale numerical model to investigate the effect of these fluid effects in fault gouge during an earthquake. We use a coupled finite difference-discrete element model (Goren et al, 2011), in which the pore space is filled with a fluid. Local changes in grain packing generate local deviations in fluid pressure, which can be relieved by fluid flow through the permeable gouge. Fluid pressure gradients exert drag forces on the grains that couple the grain motion and fluid flow. We simulated 39 granular gouge zones that were slowly loaded in shear stress to near the failure point, and then conducted two different simulations starting from each grain packing: one with a high enough mean permeability (> 10-11 m2) that pressure remains everywhere equilibrated ("fully drained"), and one with a lower permeability ( 10-14 m2) in which flow is not fast enough to prevent significant pressure variations from developing ("undrained"). The static strength of the fault, the size of the event and the evolution of slip velocity are not imposed, but arise naturally from the granular packing. In our particular granular model, all fully drained slip events are well-modeled by a rapid drop in the frictional resistance of the granular packing from a static value to a dynamic value that remains roughly constant during slip. Undrained events show more complex behavior. In some cases, slip occurs via a slow creep with resistance near the static value. When rapid slip events do occur, the dynamic resistance is typically larger than in drained events, and highly variable. Frictional resistance is not correlated with the mean fluid pressure in the layer, but is instead controlled by local regions undergoing dilational strengthening. We find that (in the absence of pressure-generating effects like thermal pressurization or fluid-releasing reactions), the overall effect of fluid is to strengthen the fault.

Effect of skull flexural properties on brain response during dynamic head loading - biomed 2013.

PubMed

Harrigan, T P; Roberts, J C; Ward, E E; Carneal, C M; Merkle, A C

2013-01-01

The skull-brain complex is typically modeled as an integrated structure, similar to a fluid-filled shell. Under dynamic loads, the interaction of the skull and the underlying brain, cerebrospinal fluid, and other tissue produces the pressure and strain histories that are the basis for many theories meant to describe the genesis of traumatic brain injury. In addition, local bone strains are of interest for predicting skull fracture in blunt trauma. However, the role of skull flexure in the intracranial pressure response to blunt trauma is complex. Since the relative time scales for pressure and flexural wave transmission across the skull are not easily separated, it is difficult to separate out the relative roles of the mechanical components in this system. This study uses a finite element model of the head, which is validated for pressure transmission to the brain, to assess the influence of skull table flexural stiffness on pressure in the brain and on strain within the skull. In a Human Head Finite Element Model, the skull component was modified by attaching shell elements to the inner and outer surfaces of the existing solid elements that modeled the skull. The shell elements were given the properties of bone, and the existing solid elements were decreased so that the overall stiffness along the surface of the skull was unchanged, but the skull table bending stiffness increased by a factor of 2.4. Blunt impact loads were applied to the frontal bone centrally, using LS-Dyna. The intracranial pressure predictions and the strain predictions in the skull were compared for models with and without surface shell elements, showing that the pressures in the mid-anterior and mid-posterior of the brain were very similar, but the strains in the skull under the loads and adjacent to the loads were decreased 15% with stiffer flexural properties. Pressure equilibration to nearly hydrostatic distributions occurred, indicating that the important frequency components for typical impact loading are lower than frequencies based on pressure wave propagation across the skull. This indicates that skull flexure has a local effect on intracranial pressures but that the integrated effect of a dome-like structure under load is a significant part of load transfer in the skull in blunt trauma.

Combined Molecular Algorithms for the Generation, Equilibration and Topological Analysis of Entangled Polymers: Methodology and Performance

PubMed Central

Karayiannis, Nikos Ch.; Kröger, Martin

2009-01-01

We review the methodology, algorithmic implementation and performance characteristics of a hierarchical modeling scheme for the generation, equilibration and topological analysis of polymer systems at various levels of molecular description: from atomistic polyethylene samples to random packings of freely-jointed chains of tangent hard spheres of uniform size. Our analysis focuses on hitherto less discussed algorithmic details of the implementation of both, the Monte Carlo (MC) procedure for the system generation and equilibration, and a postprocessing step, where we identify the underlying topological structure of the simulated systems in the form of primitive paths. In order to demonstrate our arguments, we study how molecular length and packing density (volume fraction) affect the performance of the MC scheme built around chain-connectivity altering moves. In parallel, we quantify the effect of finite system size, of polydispersity, and of the definition of the number of entanglements (and related entanglement molecular weight) on the results about the primitive path network. Along these lines we approve main concepts which had been previously proposed in the literature. PMID:20087477

To Keep or Not to Keep? The Question of Crystallographic Waters for Enzyme Simulations in Organic Solvent

PubMed Central

Dahanayake, Jayangika N.; Gautam, Devaki N.; Verma, Rajni; Mitchell-Koch, Katie R.

2016-01-01

The use of enzymes in non-aqueous solvents expands the use of biocatalysts to hydrophobic substrates, with the ability to tune selectivity of reactions through solvent selection. Non-aqueous enzymology also allows for fundamental studies on the role of water and other solvents in enzyme structure, dynamics, and function. Molecular dynamics simulations serve as a powerful tool in this area, providing detailed atomic information about the effect of solvents on enzyme properties. However, a common protocol for non-aqueous enzyme simulations does not exist. If you want to simulate enzymes in non-aqueous solutions, how many and which crystallographic waters do you keep? In the present work, this question is addressed by determining which crystallographic water molecules lead most quickly to an equilibrated protein structure. Five different methods of selecting and keeping crystallographic waters are used in order to discover which crystallographic waters lead the protein structure to reach an equilibrated structure more rapidly in organic solutions. It is found that buried waters contribute most to rapid equilibration in organic solvent, with slow-diffusing waters giving similar results. PMID:27403032

The Cardiovascular Effects of Morphine THE PERIPHERAL CAPACITANCE AND RESISTANCE VESSELS IN HUMAN SUBJECTS

PubMed Central

Zelis, Robert; Mansour, Edward J.; Capone, Robert J.; Mason, Dean T.

1974-01-01

To evaluate the effects of morphine on the peripheral venous and arterial beds, 69 normal subjects were evaluated before and after the intravenous administration of 15 mg morphine. Venous tone was determined by three independent techniques in 22 subjects. The venous pressure measured in a hand vein during temporary circulatory arrest (isolated hand vein technique) fell from 20.2±1.4 to 13.4±0.9 mm Hg (P < 0.01) 10 min after morphine, indicating that a significant venodilation had occurred. With the acute occlusion technique, morphine induced a reduction in forearm venous tone from 12.8±1.1 to 7.9±2.3 mm Hg/ml/100 ml (P < 0.01). Although forearm venous volume at a pressure of 30 mm Hg (VV[30]) was increased from 2.26±0.17 to 2.55±0.26 ml/100 ml, measured by the equilibration technique, the change was not significant (P > 0.1). Of note is that the initial reaction to morphine was a pronounced venoconstriction, demonstrated during the first 1-2 min after the drug. (Isolated hand vein pressure increased to 37.2±5.4 mm Hg, P < 0.01). This rapidly subsided, and by 5 min a venodilation was evident. Morphine did not attenuate the venoconstrictor response to a single deep breath, mental arithmetic, or the application of ice to the forehead when measured by either the isolated hand vein technique or the equilibration technique. To evaluate the effects of morphine on the peripheral resistance vessels in 47 normal subjects, forearm blood flow was measured plethysmographically before and 10-15 min after the intravenous administration of 15 mg of morphine. Although mean systemic arterial pressure was unchanged, forearm blood flow increased from 2.92±0.28 to 3.96±0.46 ml/min/100 ml (P < 0.01), and calculated vascular resistance fell from 42.4±5.2 to 31.6±3.2 mm Hg/ml/min/100 ml (P < 0.01). When subjects were tilted to the 45° head-up position, morphine did not block the increase in total peripheral vascular resistance that occurs; however, it did significantly attenuate the forearm arteriolar constrictor response (before morphine, + 25.7±5.4; after morphine, + 13.7±5.3 mm Hg/ml/min/100 ml, P < 0.05). However, morphine did not block the post-Valsalva overshoot of blood pressure, nor did it block the increase in forearm vascular resistance produced by the application of ice to the forehead. Similarly, morphine did not block the arteriolar or venoconstrictor effects of intra-arterially administered norepinephrine. Morphine infused into the brachial artery in doses up to 200 μg/min produced no changes in ipsilateral forearm VV[30], forearm blood flow, or calculated forearm resistance. Intra-arterial promethazine, atropine, and propranolol did not block the forearm arteriolar dilator response to intravenous morphine; however, intra-arterial phentolamine abolished the response. These data suggest that in human subjects, morphine induces a peripheral venous and arteriolar dilation by a reflex reduction in sympathetic alpha adrenergic tone. Morphine does not appear to act as a peripheral alpha adrenergic blocking agent but seems to attenuate the sympathetic efferent discharge at a central nervous system level. Images PMID:4612057

Lunar and Planetary Science XXXV: Terrestrial Planets: Building Blocks and Differentiation

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Terrestrial Planets: Building Blocks and Differentiation: included the following topics:Magnesium Isotopes in the Earth, Moon, Mars, and Pallasite Parent Body: High-Precision Analysis of Olivine by Laser-Ablation Multi-Collector ICPMS; Meteoritic Constraints on Collision Rates in the Primordial Asteroid Belt and Its Origin; New Constraints on the Origin of the Highly Siderophile Elements in the Earth's Upper Mantle; Further Lu-Hf and Sm-Nd Isotopic Data on Planetary Materials and Consequences for Planetary Differentiation; A Deep Lunar Magma Ocean Based on Neodymium, Strontium and Hafnium Isotope Mass Balance Partial Resetting on Hf-W System by Giant Impacts; On the Problem of Metal-Silicate Equilibration During Planet Formation: Significance for Hf-W Chronometry ; Solid Metal-Liquid Metal Partitioning of Pt, Re, and Os: The Effect of Carbon; Siderophile Element Abundances in Fe-S-Ni-O Melts Segregated from Partially Molten Ordinary Chondrite Under Dynamic Conditions; Activity Coefficients of Silicon in Iron-Nickel Alloys: Experimental Determination and Relevance for Planetary Differentiation; Reinvestigation of the Ni and Co Metal-Silicate Partitioning; Metal/Silicate Paritioning of P, Ga, and W at High Pressures and Temperatures: Dependence on Silicate Melt Composition; and Closure of the Fe-S-Si Liquid Miscibility Gap at High Pressure and Its Implications for Planetary Core Formation.

MD simulations of phase stability of PuGa alloys: Effects of primary radiation defects and helium bubbles

DOE PAGES

Dremov, V. V.; Sapozhnikov, F. A.; Ionov, G. V.; ...

2013-05-14

We present classical molecular dynamics (MD) with Modified Embedded Atom Model (MEAM) simulations to investigate the role of primary radiation defects and radiogenic helium as factors affecting the phase stability of PuGa alloys in cooling–heating cycles at ambient pressure. The models of PuGa alloys equilibrated at ambient conditions were subjected to cooling–heating cycles in which they were initially cooled down to 100 K and then heated up to 500 K at ambient pressure. The rate of temperature change in the cycles was 10 K/ns. The simulations showed that the initial FCC phase of PuGa alloys undergo polymorphous transition in coolingmore » to a lower symmetry α'-phase. All the alloys undergo direct and reverse polymorphous transitions in the cooling–heating cycles. The alloys containing vacancies shift in both transitions to lower temperatures relative to the defect-free alloys. The radiogenic helium has much less effect on the phase stability compared to that of primary radiation defects (in spite of the fact that helium concentration is twice of that for the primary radiation defects). Lastly, this computational result agrees with experimental data on unconventional stabilization mechanism of PuGa alloys.« less

Self-pinched lithium beam transport experiments on SABRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, D.L.; Olson, C.L.; Poukey, J.W.

Self-pinched transport of ion beams has many advantages for ion-driven ICF applications involving high yield and energy production. The authors are currently preparing for a self-pinched lithium beam transport experiment on the SABRE accelerator. There are three transport elements that must eventually be demonstrated: (1) efficient lithium beam generation and ballistic transport to a focus at the self-pinched transport channel entrance; (2) self-pinched transport in the channel, requiring optimized injection conditions and gas breakdown; and (3) self-pinched transport of the equilibrated beam from the channel into free space, with associated aiming and stability considerations. In the present experiment, a hollowmore » annular lithium beam from an applied-B extraction ion diode will be focused to small radius (r {le} 2 cm) in a 60 cm long ballistic focus section containing argon gas at a pressure of a few Torr. The self-pinched transport channel will contain a low pressure background gas of 10--40 mTorr argon to allow sufficient net current to confine the beam for long distance transport. IPROP simulations are in progress to optimize the design of the ballistic and self-pinched transport sections. Progress on preparation of this lithium self-pinched transport experiment, including a discussion of transport system design, important gas breakdown issues, and diagnostics, will be presented.« less

Binary gaseous mixture and single component adsorption of methane and argon on exfoliated graphite

NASA Astrophysics Data System (ADS)

Russell, Brice Adam

Exfoliated graphite was used as a substrate for adsorption of argon and methane. Adsorption experiments were conducted for both equal parts mixtures of argon and methane and for each gas species independently. The purpose of this was to compare mixture adsorption to single component adsorption and to investigate theoretical predictions concerning the kinetics of adsorption made by Burde and Calbi.6 In particular, time to reach pressure equilibrium of a single dose at a constant temperature for the equal parts mixture was compared to time of adsorption for each species by itself. It was shown that mixture adsorption is a much more complex and time consuming process than single component adsorption and requires a much longer amount of time to reach equilibrium. Information about the composition evolution of the mixture during the times when pressure was going toward equilibrium was obtained using a quadrupole mass spectrometer. Evidence for initial higher rate of adsorption for the weaker binding energy species (argon) was found as well as overall composition change which clearly indicated a higher coverage of methane on the graphite sample by the time equilibration was reached. Effective specific surface area of graphite for both argon and methane was also determined using the Point-B method.2

Gas Surface Interactions Occurring on Materials Within Ultrahigh Vacuum. Ph.D. Thesis - va. Polytechnic Inst.

NASA Technical Reports Server (NTRS)

Outlaw, R. A.

1972-01-01

The physical adsorption of nitrogen on the chemically cleaned surfaces of Pyrex, 347 stainless steel and polycrystalline nickel was investigated over the pressure range 1 x 10 to the minus 12th power to 3 x 10 to the minus 7th power torr and for temperatures 77.4 and 87.4 K. The adsorption data were linearized by the Dubinin-Radushkevich equation. The metal surfaces were cleaned by electron impact desorption (EID) and the desorbed gases analyzed by mass spectrometry. Work function measurements were also used to indicate changes in the surface condition following an EID dose. At least a monolayer of gas was observed to desorb from the metal surfaces. The isotherms revealed that the metal surfaces were very heterogeneous and that the Pyrex surface had been leached. The calculated isosteric heats of adsorption indicated that the relative order of the physical binding of nitrogen to the solids was 347 stainless steel Pyrex nickel. A relationship was observed to exist in the dynamic technique between the equilibration time and the pressure above the absorbed layer. The slope of the log-log plot of these parameters was found to be sensitive to the surface heterogeneity and may be related to the activation energy for surface diffusion of physically absorbed molecules.

Convergence to equilibrium under a random Hamiltonian.

PubMed

Brandão, Fernando G S L; Ćwikliński, Piotr; Horodecki, Michał; Horodecki, Paweł; Korbicz, Jarosław K; Mozrzymas, Marek

2012-09-01

We analyze equilibration times of subsystems of a larger system under a random total Hamiltonian, in which the basis of the Hamiltonian is drawn from the Haar measure. We obtain that the time of equilibration is of the order of the inverse of the arithmetic average of the Bohr frequencies. To compute the average over a random basis, we compute the inverse of a matrix of overlaps of operators which permute four systems. We first obtain results on such a matrix for a representation of an arbitrary finite group and then apply it to the particular representation of the permutation group under consideration.

Convergence to equilibrium under a random Hamiltonian

NASA Astrophysics Data System (ADS)

Brandão, Fernando G. S. L.; Ćwikliński, Piotr; Horodecki, Michał; Horodecki, Paweł; Korbicz, Jarosław K.; Mozrzymas, Marek

2012-09-01

We analyze equilibration times of subsystems of a larger system under a random total Hamiltonian, in which the basis of the Hamiltonian is drawn from the Haar measure. We obtain that the time of equilibration is of the order of the inverse of the arithmetic average of the Bohr frequencies. To compute the average over a random basis, we compute the inverse of a matrix of overlaps of operators which permute four systems. We first obtain results on such a matrix for a representation of an arbitrary finite group and then apply it to the particular representation of the permutation group under consideration.

High-resolution measurements of elemental mercury in surface water for an improved quantitative understanding of the Baltic Sea as a source of atmospheric mercury

NASA Astrophysics Data System (ADS)

Kuss, Joachim; Krüger, Siegfried; Ruickoldt, Johann; Wlost, Klaus-Peter

2018-03-01

Marginal seas are directly subjected to anthropogenic and natural influences from land in addition to receiving inputs from the atmosphere and open ocean. Together these lead to pronounced gradients and strong dynamic changes. However, in the case of mercury emissions from these seas, estimates often fail to adequately account for the spatial and temporal variability of the elemental mercury concentration in surface water (Hg0wat). In this study, a method to measure Hg0wat at high resolution was devised and subsequently validated. The better-resolved Hg0wat dataset, consisting of about one measurement per nautical mile, yielded insight into the sea's small-scale variability and thus improved the quantification of the sea's Hg0 emission. This is important because global marine Hg0 emissions constitute a major source of atmospheric mercury. Research campaigns in the Baltic Sea were carried out between 2011 and 2015 during which Hg0 both in surface water and in ambient air were measured. For the former, two types of equilibrators were used. A membrane equilibrator enabled continuous equilibration and a bottle equilibrator assured that equilibrium was reached for validation. The measurements were combined with data obtained in the Baltic Sea in 2006 from a bottle equilibrator only. The Hg0 sea-air flux was newly calculated with the combined dataset based on current knowledge of the Hg0 Schmidt number, Henry's law constant, and a widely used gas exchange transfer velocity parameterization. By using a newly developed pump-CTD with increased pumping capability in the Hg0 equilibrator measurements, Hg0wat could also be characterized in deeper water layers. A process study carried out near the Swedish island Øland in August 2015 showed that the upwelling of Hg0-depleted water contributed to Hg0 emissions of the Baltic Sea. However, a delay of a few days after contact between the upwelled water and light was apparently necessary before the biotic and abiotic transformations of ionic to volatile Hg0 produced a distinct sea-air Hg0 concentration gradient. This study clearly showed spatial, seasonal, and interannual variability in the Hg0 sea-air flux of the Baltic Sea. The average annual Hg0 emission was 0.90 ± 0.18 Mg for the Baltic proper and extrapolated to 1.73 ± 0.32 Mg for the entire Baltic Sea, which is about half the amount entrained by atmospheric deposition. A comparison of our results with the Hg0 sea-air fluxes determined in the Mediterranean Sea and in marginal seas in East Asia were to some extent similar but they partly differed in terms of the deviations in the amount and seasonality of the flux.

Confocal Raman Microscopy for in Situ Measurement of Octanol-Water Partitioning within the Pores of Individual C18-Functionalized Chromatographic Particles.

PubMed

Kitt, Jay P; Harris, Joel M

2015-05-19

Octanol-water partitioning is one of the most widely used predictors of hydrophobicity and lipophilicity. Traditional methods for measuring octanol-water partition coefficients (K(ow)), including shake-flasks and generator columns, require hours for equilibration and milliliter quantities of sample solution. These challenges have led to development of smaller-scale methods for measuring K(ow). Recent advances in microfluidics have produced faster and smaller-volume approaches to measuring K(ow). As flowing volumes are reduced, however, separation of water and octanol prior to measurement and detection in small volumes of octanol phase are especially challenging. In this work, we reduce the receiver volume of octanol-water partitioning measurements from current practice by six-orders-of-magnitude, to the femtoliter scale, by using a single octanol-filled reversed-phase, octadecylsilane-modified (C18-silica) chromatographic particle as a collector. The fluid-handling challenges of working in such small volumes are circumvented by eliminating postequilibration phase separation. Partitioning is measured in situ within the pore-confined octanol phase using confocal Raman microscopy, which is capable of detecting and quantifying a wide variety of molecular structures. Equilibration times are fast (less than a minute) because molecular diffusion is efficient over distance scales of micrometers. The demonstrated amount of analyte needed to carry out a measurement is very small, less than 50 fmol, which would be a useful attribute for drug screening applications or testing of small quantities of environmentally sensitive compounds. The method is tested for measurements of pH-dependent octanol-water partitioning of naphthoic acid, and the results are compared to both traditional shake-flask measurements and sorption onto C18-modified silica without octanol present within the pores.

Magmatic conditions and processes in the storage zone of the 2004-2006 Mount St. Helens dacite: Chapter 31 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

USGS Publications Warehouse

Rutherford, Malcom J.; Devine, Joseph D.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

2008-01-01

O2 values of NNO +1 log unit. Magnetite compositions suggest that the 2004-6 magma was formed by mingling of magmas less than 5-8 weeks before eruption and that the magma last equilibrated within this temperature range. The amphibole phenocryst zoning involves approximately equal amounts of a pressure-sensitive Al-Tschermak molecular substitution and a temperature-sensitive edenite substitution in one cycle of growth. Hydrothermal experiments done on the natural dacite show that crystallization of the Fe- and Al-rich amphibole end member requires pressures of 200-300 MPa at temperatures of 900°C, conditions approaching the upper temperature limit of amphibole stability. The dacitic magma crystallizes the An68 plagioclase when the pressure drops to 200 MPa at 900°C. The magma must cool at this depth to produce a complete An68-An40 plagioclase zone and a Mg-rich layer on the amphiboles before the magma is cycled back to a high pressure, when a new layer of Fe-rich amphibole is acquired. The amphibole crystallizing in the dacite experiments at less than 200 MPa is lower in aluminum than any compositions in the natural cyclically zoned phenocrysts. The outer rim on some 2004-6 amphibole phenocrysts appears to have formed in the 100-200 MPa range, as do some phenocrysts in the May 1980 dacite pumice. Plagioclase rims of An35 in the 2004-6 magmas indicate that phenocryst growth continued until the pressure decreased to 130 MPa and that ascent was slow until this depth. Magma then entered the conduit for a relatively rapid ascent to the surface as indicated by the very thin (less than 5 μm) decompression-induced rims on the amphibole phenocrysts.

Growth history of Kilauea inferred from volatile concentrations in submarine-collected basalts

NASA Astrophysics Data System (ADS)

Coombs, Michelle L.; Sisson, Thomas W.; Lipman, Peter W.

2006-03-01

Major-element and volatile (H 2O, CO 2, S) compositions of glasses from the submarine flanks of Kilauea Volcano record its growth from pre-shield into tholeiite shield-stage. Pillow lavas of mildly alkalic basalt at 2600-1900 mbsl on the upper slope of the south flank are an intermediate link between deeper alkalic volcaniclastics and the modern tholeiite shield. Lava clast glasses from the west flank of Papau Seamount are subaerial Mauna Loa-like tholeiite and mark the contact between the two volcanoes. H 2O and CO 2 in sandstone and breccia glasses from the Hilina bench, and in alkalic to tholeiitic pillow glasses above and to the east, were measured by FTIR. Volatile saturation pressures equal sampling depths (10 MPa = 1000 m water) for south flank and Puna Ridge pillow lavas, suggesting recovery near eruption depths and/or vapor re-equilibration during down-slope flow. South flank glasses are divisible into low-pressure (CO 2 < 40 ppm, H 2O < 0.5 wt.%, S < 500 ppm), moderate-pressure (CO 2 < 40 ppm, H 2O > 0.5 wt.%, S 1000-1700 ppm), and high-pressure groups (CO 2 > 40 ppm, S > ˜1000 ppm), corresponding to eruption ≥ sea level, at moderate water depths (300-1000 m) or shallower but in disequilibrium, and in deep water (> 1000 m). Saturation pressures range widely in early alkalic to strongly alkalic breccia clast and sandstone glasses, establishing that early Kīlauea's vents spanned much of Mauna Loa's submarine flank, with some vents exceeding sea level. Later south flank alkalic pillow lavas expose a sizeable submarine edifice that grew concurrent with nearby subaerial alkalic eruptions. The onset of the tholeiitic shield stage is marked by extension of eruptions eastward and into deeper water (to 5500 m) during growth of the Puna Ridge. Subaerial and shallow water eruptions from earliest Kilauea show that it is underlain shallowly by Mauna Loa, implying that Mauna Loa is larger, and Kilauea smaller, than previously recognized.

Heterogeneous mineral assemblages in martian meteorite Tissint as a result of a recent small impact event on Mars

NASA Astrophysics Data System (ADS)

Walton, E. L.; Sharp, T. G.; Hu, J.; Filiberto, J.

2014-09-01

The microtexture and mineralogy of shock melts in the Tissint martian meteorite were investigated using scanning electron microscopy, Raman spectroscopy, transmission electron microscopy and synchrotron micro X-ray diffraction to understand shock conditions and duration. Distinct mineral assemblages occur within and adjacent to the shock melts as a function of the thickness and hence cooling history. The matrix of thin veins and pockets of shock melt consists of clinopyroxene + ringwoodite ± stishovite embedded in glass with minor Fe-sulfide. The margins of host rock olivine in contact with the melt, as well as entrained olivine fragments, are now amorphosed silicate perovskite + magnesiowüstite or clinopyroxene + magnesiowüstite. The pressure stabilities of these mineral assemblages are ∼15 GPa and >19 GPa, respectively. The ∼200-μm-wide margin of a thicker, mm-size (up to 1.4 mm) shock melt vein contains clinopyroxene + olivine, with central regions comprising glass + vesicles + Fe-sulfide spheres. Fragments of host rock within the melt are polycrystalline olivine (after olivine) and tissintite + glass (after plagioclase). From these mineral assemblages the crystallization pressure at the vein edge was as high as 14 GPa. The interior crystallized at ambient pressure. The shock melts in Tissint quench-crystallized during and after release from the peak shock pressure; crystallization pressures and those determined from olivine dissociation therefore represent the minimum shock loading. Shock deformation in host rock minerals and complete transformation of plagioclase to maskelynite suggest the peak shock pressure experienced by Tissint ⩾ 29-30 GPa. These pressure estimates support our assessment that the peak shock pressure in Tissint was significantly higher than the minimum 19 GPa required to transform olivine to silicate perovskite plus magnesiowüstite. Small volumes of shock melt (<100 μm) quench rapidly (0.01 s), whereas thermal equilibration will occur within 1.2 s in larger volumes of melt (1 mm2). The apparent variation in shock pressure recorded by variable mineral assemblages within and around shock melts in Tissint is consistent with a shock pulse on the order of 10-20 ms combined with a longer duration of post-shock cooling and complex thermal history. This implies that the impact on Mars that shocked and ejected Tissint at ∼1 Ma was not exceptionally large.

Effectiveness of glucose-methanol extender for cryopreservation of Huso huso spermatozoa.

PubMed

Aramli, Mohammad Sadegh; Golshahi, Karim; Nazari, Rajab Mohammad; Aramli, Salim; Banan, Ashkan

2015-11-01

The present approach was designed to evaluate the methanol-glucose extender effects on sperm cryopreservation in beluga sturgeon, Huso huso. Sperm quality was examined by measuring post-thaw sperm motility and fertilizing rate at hatching stage. We first tested the effect of glucose concentration (0, 0.10, 0.15, 0.20 and 0.30M) in a methanol extender on post-thaw sperm motility. The optimal cryopreservation conditions were found to be 0.2M glucose in the extender. Then, motility and fertilization rates of sperm cryopreserved with 0.2M glucose and 10% methanol (GM) were compared to Tris-sucrose-KCl in 10% methanol extender (TSKM). Additionally, sperm motility and fertilizing ability in relation to 15 and 30min equilibration in GM extender before and after cryopreservation were measured. Higher post-thaw sperm motility duration and percentage as well as fertilization rate were obtained with the GM extender when compared to TSKM extender. Equilibration of sperm in extender did not affect the motility quality of either fresh-diluted or frozen/thawed sperm, while fertilization rate showed a significant decline alone after 30min of post-thaw storage. Our results indicated that the use of a simple extender consisting of 0.2M glucose in 10% methanol can be an alternative cryopreservation method to those previously described for sturgeons. Copyright © 2015 Elsevier B.V. All rights reserved.

Direct formulation of a 4-node hybrid shell element with rotational degrees of freedom

NASA Technical Reports Server (NTRS)

Aminpour, Mohammad A.

1990-01-01

A simple 4-node assumed-stress hybrid quadrilateral shell element with rotational or drilling degrees of freedom is formulated. The element formulation is based directly on a 4-node element. This direct formulation requires fewer computations than a similar element that is derived from an internal 8-node isoparametric element in which the midside degrees of freedom are eliminated in favor of rotational degree of freedom at the corner nodes. The formulation is based on the principle of minimum complementary energy. The membrane part of the element has 12 degrees of freedom including rotational degrees of freedom. The bending part of the element also has 12 degrees of freedom. The bending part of the quadratic variations for both in-plane and out-of-plane displacement fields and linear variations for both in-plane and out-of-plane rotation fields are assumed along the edges of the element. The element Cartesian-coordinate system is chosen such as to make the stress field invariant with respect to node numbering. The membrane part of the stress field is based on a 9-parameter equilibrating stress field, while the bending part is based on a 13-parameter equilibrating stress field. The element passes the patch test, is nearly insensitive to mesh distortion, does not lock, possesses the desirable invariance properties, has no spurious modes, and produces accurate and reliable results.

Temperature uniformity of the bulk medium produced in relativistic heavy-ion collisions

NASA Astrophysics Data System (ADS)

Ray, Lanny

2006-10-01

The success of hydrodynamic models of elliptic flow in relativistic heavy ion collisions is often touted as evidence for rapid thermal equilibration. However, large momentum scale two-particle correlations indicate that a significant fraction of the final-state hadrons retain jet-like correlation structure associated with early stage, non-equilibrated low-Q^2 partons [1]. In addition, correlations on transverse momentum (pt1xpt2) suggest that low-Q^2 parton momentum is partially dissipated causing fluctuations in the effective temperature (thermal and/or collective motion) of the bulk medium[2]. We first show that both global and local temperature fluctuation models describe the available (pt1xpt2) correlation data equally well. Results of an analytical model are then presented which tests the sensitivity of (pt1xpt2) correlations to the first few lower-order cumulants of the two-point temperature distribution for the event ensemble. Unique signatures in the predicted (pt1xpt2) correlations are observed for each cumulant term studied. The prospects for direct measurement of the absolute temperature distribution in the bulk medium produced in relativistic heavy-ion collisions using (pt1xpt2) and other correlation measures are discussed. [1] J. Adams et al., Phys. Rev. C 73, 064907 (2006); J. Phys.G. 32, L37 (2006). [2]J. Adams et al., nucl-ex/0408012.

Role of adenosine and wake-promoting basal forebrain in insomnia and associated sleep disruptions caused by ethanol dependence.

PubMed

Sharma, Rishi; Engemann, Samuel; Sahota, Pradeep; Thakkar, Mahesh M

2010-11-01

Insomnia is a severe symptom of alcohol withdrawal; however, the underlying neuronal mechanism is yet unknown. We hypothesized that chronic ethanol exposure will impair basal forebrain (BF) adenosinergic mechanism resulting in insomnia-like symptoms. We performed a series of experiments in Sprague-Dawley rats to test our hypothesis. We used Majchrowicz's chronic binge ethanol protocol to induce ethanol dependency. Our first experiment verified the effects of ethanol withdrawal on sleep-wakefulness. Significant increase in wakefulness was observed during ethanol withdrawal. Next, we examined c-Fos expression (marker of neuronal activation) in BF wake-promoting neurons during ethanol withdrawal. There was a significant increase in the number of BF wake-promoting neurons with c-Fos immunoreactivity. Our third experiment examined the effects of ethanol withdrawal on sleep deprivation induced increase in BF adenosine levels. Sleep deprivation did not increase BF adenosine levels in ethanol dependent rats. Our last experiment examined the effects of ethanol withdrawal on equilibrative nucleoside transporter 1 and A1 receptor expression in the BF. There was a significant reduction in A1 receptor and equilibrative nucleoside transporter 1 expression in the BF of ethanol dependent rats. Based on these results, we suggest that insomnia observed during ethanol withdrawal is caused because of impaired adenosinergic mechanism in the BF. © 2010 The Authors. Journal of Neurochemistry © 2010 International Society for Neurochemistry.

Simulating Air-Entrapment in Low Permeability Mudrocks using a Macroscopic Invasion Percolation Model

NASA Astrophysics Data System (ADS)

Singh, A.; Holt, R. M.; Ramarao, B.; Clemo, T.

2011-12-01

Three radioactive waste disposal landfills at the Waste Control Specialists (WCS) facility in Andrews County, Texas are constructed below grade, within the low-permeability Dockum Group mudrocks (Cooper Canyon Formation) of Triassic age. Recent site investigations at the WCS disposal facilities indicate the presence of a trapped and compressed gas phase in the mudrocks. The Dockum is a low-permeability medium with vertical and horizontal effective hydraulic conductivities of 1.2E-9 cm/s and 2.9E-7 cm/s. The upper 300+ feet of the Dockum is in the unsaturated zone, with an average saturation of 0.87 and average capillary pressure of 2.8 MPa determined from core samples. Air entry pressures on core samples range from from 0.016 to 9.8 MPa, with a mean of 1.0 MPa. Heat dissipation sensors, thermocouple psychrometers, and advanced tensiometers installed in Dockum borehole arrays generally show capillary pressures one order of magnitude less than those measured on core samples. These differences with core data are attributed to the presence of a trapped and compressed gas phase within Dockum materials. In the vicinity of an instrumented borehole, the gas phase pressure equilibrates with atmospheric pressure, lowering the capillary pressure. We have developed a new macroscopic invasion percolation (MIP) model to illustrate the origin of the trapped gas phase in the Dockum rocks. An MIP model differs from invasion percolation (IP) through the definition of macro-scale capillarity. Individual pore throats and necks are not considered. Instead, a near pore-scale block is defined and characterized by a local threshold spanning pressure (a local block-scale breakthrough pressure) that represents the behavior of the subscale network. The model domain is discretized into an array of grid blocks with assigned spanning pressures. An invasion pressure for each block is then determined by the sum of spanning pressure, buoyance forces, and viscous forces. An IP algorithm sorts the invadable blocks, selects the block connected to the growing cluster with the lowest invasion pressure, and invades it. Our new MIP model incorporates several new features, including an efficient three-dimensional clustering algorithm; simultaneous invasion/reinvasion of water and air phases; hysteresis in water and air drainage curves; capability for distributed porosities and drainage parameters; and gas-phase compression and trapping. We apply this model in simulations representing the WCS site and illustrate the origin of the trapped and compressed gas phase in Dockum mudrocks.

Excitation transfer and trapping kinetics in plant photosystem I probed by two-dimensional electronic spectroscopy.

PubMed

Akhtar, Parveen; Zhang, Cheng; Liu, Zhengtang; Tan, Howe-Siang; Lambrev, Petar H

2018-03-01

Photosystem I is a robust and highly efficient biological solar engine. Its capacity to utilize virtually every absorbed photon's energy in a photochemical reaction generates great interest in the kinetics and mechanisms of excitation energy transfer and charge separation. In this work, we have employed room-temperature coherent two-dimensional electronic spectroscopy and time-resolved fluorescence spectroscopy to follow exciton equilibration and excitation trapping in intact Photosystem I complexes as well as core complexes isolated from Pisum sativum. We performed two-dimensional electronic spectroscopy measurements with low excitation pulse energies to record excited-state kinetics free from singlet-singlet annihilation. Global lifetime analysis resolved energy transfer and trapping lifetimes closely matches the time-correlated single-photon counting data. Exciton energy equilibration in the core antenna occurred on a timescale of 0.5 ps. We further observed spectral equilibration component in the core complex with a 3-4 ps lifetime between the bulk Chl states and a state absorbing at 700 nm. Trapping in the core complex occurred with a 20 ps lifetime, which in the supercomplex split into two lifetimes, 16 ps and 67-75 ps. The experimental data could be modelled with two alternative models resulting in equally good fits-a transfer-to-trap-limited model and a trap-limited model. However, the former model is only possible if the 3-4 ps component is ascribed to equilibration with a "red" core antenna pool absorbing at 700 nm. Conversely, if these low-energy states are identified with the P 700 reaction centre, the transfer-to-trap-model is ruled out in favour of a trap-limited model.

Evolution of light hydrocarbon gases in subsurface processes: Constraints from chemical equilibrium

NASA Astrophysics Data System (ADS)

Sugisaki, Ryuichi; Nagamine, Koichiro

1995-06-01

The behaviour of CH 4, C 2H 6 and C 3H 8 in subsurface processes such as magma intrusion, volcanic gas discharge and natural gas generation have been examined from the viewpoint of chemical equilibrium. It seems that equilibrium among these three hydrocarbons is attainable at about 200°C. When a system at high temperatures is cooled, re-equilibration is continued until a low temperature is reached. The rate at which re-equilibration is achieved, however, steadily diminishes and, below 200°C, the reaction between the hydrocarbons stops and the gas composition at this time is frozen in, and it remains unchanged in a metastable state for a long period of geological time. Natural gas compositions from various fields have shown that, when a hydrocarbon system out of chemical equilibrium is heated, it gradually approaches equilibrium above 150°C. On the way towards equilibration, compositions of thermogenic gases apparently temporarily show a thermodynamic equilibrium constant at a temperature that is higher than the real equilibrium temperature expected from the ambient temperature of the samples; in contrast, biogenic gases indicate a lower temperature. In lower temperature regions, kinetic effects probably control the gas composition; the compositions are essentially subjected to genetic processes operating on the gases (such as pyrolysis of organic material and bacterial activity) and they fluctuate substantially. Examination of volcanic gases and pyrolysis experimental data, however, have suggested that the equilibration rate of these hydrocarbons is sluggish in comparison with that of reactive inorganic species such as H 2S and SO 2. The view presented in this study will be helpful in understanding the genetic processes that create oil and gas and the migration of these hydrocarbons and in interpreting the origins of magmatic gases.

Topics in Non-Equilibrium Dynamics and the Emergence of Spacetime

NASA Astrophysics Data System (ADS)

Engelhardt, Dalit

The Anti-de Sitter / Conformal Field Theory (AdS/CFT) correspondence that arises in string theory has had implications for the study of phenomena across a range of subfields in physics, from spacetime geometry to the behavior of condensed matter systems. Two major themes that have featured prominently in these investigations have been the behavior of systems out of equilibrium, and the emergence of spacetime. In this thesis, aspects of these themes are considered and analyzed. The question of equilibration and thermalization in 2D conformal field theories is addressed and refined via a number of observations about local versus global thermalization in such systems, the validity of particular diagnostics of thermalization, the dependence of the equilibration behavior of a conformal field theory on its operator spectrum, and the holographic dual of the generalized Gibbs ensemble that is of interest in studies of equilibration in systems with a large number of conserved quantities. A formalism for analyzing the non-equilibrium dynamics of 1+1-dimensional conformal field theories is discussed, and its physical relevance is motivated with an example connecting such a system to an experimental system that exhibited unusual equilibration behavior. Qualitative agreement is demonstrated between the CFT picture and the experimental observations. The emergence of spacetime geometry from quantum entanglement, while largely a byproduct of considerations from holographic dualities, has also been proposed to have a direct, non-holographic manifestation. Here a particular realization of such a direct emergence is presented through a demonstration that, in the presence of quantum entanglement alone, certain observations of electric fields in the entangled system appear qualitatively the same as the corresponding observations in a physically-connected geometric spacetime, so that the entanglement effectively mimics particular features associated with geometric connectivity.

Temperature-dependent dynamics of bovine casein micelles in the range 10-40 °C.

PubMed

Liu, Dylan Z; Weeks, Michael G; Dunstan, David E; Martin, Gregory J O

2013-12-15

Milk is a complex colloidal system that responds to changes in temperature imposed during processing. Whilst much has been learned about the effects of temperature on milk, little is known about the dynamic response of casein micelles to changes in temperature. In this study, a comprehensive physico-chemical study of casein micelles in skim milk was performed between 10 and 40 °C. When fully equilibrated, the amount of soluble casein, soluble calcium and the pH of skim milk all decreased as a function of increasing temperature, whilst the hydration and volume fraction of the casein micelles decreased. The effect of temperature on casein micelle size, as determined by dynamic light scattering and differential centrifugation, was less straightforward. Real-time measurements of turbidity and pH were used to investigate the dynamics of the system during warming and cooling of milk in the range 10-40 °C. Changes in pH are indicative of changes to the mineral system and the turbidity is a measure of alterations to the casein micelles. The pH and turbidity showed that alterations to both the casein micelles and the mineral system occurred very rapidly on warming. However, whilst mineral re-equilibration occurred very rapidly on cooling, changes to the casein micelle structure continued after 40 min of measurement, returning to equilibrium after 16 h equilibration. Casein micelle structure and the mineral system of milk were both dependent on temperature in the range 10-40 °C. The dynamic response of the mineral system to changes in temperature appeared almost instantaneous whereas equilibration of casein was considerably slower, particularly upon cooling. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effects of various combinations of cryoprotectants and cooling speed on the survival and further development of mouse oocytes after vitrification

PubMed Central

Cha, Soo Kyung; Kim, Bo Yeun; Kim, Mi Kyung; Kim, You Shin; Lee, Woo Sik

2011-01-01

Objective The objectives of this study were to analyze efficacy of immature and mature mouse oocytes after vitrification and warming by applying various combinations of cryoprotectants (CPAs) and/or super-rapid cooling using slush nitrogen (SN2). Methods Four-week old ICR female mice were superovulated for GV- and MII-stage oocytes. Experimental groups were divided into two groups. Ethylene glycol (EG) only group: pre-equilibrated with 1.5 M EG for 2.5 minutes and then equilibrated with 5.5 M EG and 1.0 M sucrose for 20 seconds. EG+dimethylsulfoxide (DMSO) group: pre-equilibrated with 1.3 M EG+1.1 M DMSO for 2.5 minutes and equilibrated with 2.7 M EG+2.1 M DMSO+0.5 M sucrose for 20 seconds. The oocytes were loaded onto grids and plunged into SN2 or liquid nitrogen (LN2). Stored oocytes were warmed by a five-step method, and then their survival, maturation, cleavage, and developmental rates were observed. Results The EG only and EG+DMSO groups showed no significant difference in survival of immature oocytes vitrified after warming. However, maturation and cleavage rates after conventional insemination were greater in the EG only group than in the EG+DMSO group. In mature oocytes, survival, cleavage, and blastocyst formation rates after warming showed no significant difference when EG only or EG+DMSO was applied. Furthermore, cleavage and blastocyst formation rates of MII oocytes vitrified using SN2 were increased in both the EG only and EG+DMSO groups. Conclusion A combination of CPAs in oocyte cryopreservation could be formulated according to the oocyte stage. In addition, SN2 may improve the efficiency of vitrification by reducing cryoinjury. PMID:22384414

The Importance of Sulfate Adenylyl Transferase in S and O Fractionation by Sulfate Reducing Bacteria

NASA Astrophysics Data System (ADS)

Smith, D. A.; Johnston, D. T.; Bradley, A. S.

2016-12-01

Microbial sulfate reduction (MSR) is critical to the oxidation of organic matter in modern and ancient oceans, and plays an important role in regulating the redox state of the Earth's surface. The sulfur and oxygen isotopic composition of seawater sulfate and of sulfate minerals reflect the biogeochemical processes that cycle sulfur, of which MSR is among the most important. MSR is a multi-enzymatic reaction network that partitions the isotopes of sulfur and oxygen as a consequence of both the flux of sulfate through this biochemical network and the fractionation imposed by each individual enzyme. MSR affects the δ18O of residual, extracellular sulfate mainly by the equilibration of the MSR intermediate sulfite with extracellular water (Antler et al., 2013 GCA, Wankel et al., 2013 Geobiol). A series of oxidative and exchange reactions catalyzed by APS reductase (APSr), sulfate adenylyl transferase (Sat), and sulfate transporters promote the conversion of water-equilibrated intracellular sulfite to extracellular sulfate. The flux of sulfoxy anions via these proteins will be, at least in part, dependent on the activity of these enzymes. To test this, we examined sulfur and oxygen isotope fractionation in genetically engineered mutants of the sulfate reducing bacterium Desulfovibrio vulgaris Hildenborough (DvH). In these mutants, the activity of Sat has been artificially increased by perturbing the (i) transcriptional repressor Rex and (ii) its binding site upstream of the gene encoding Sat (Christensen et al., 2015 J. Bacteriol). It was predicted that this would minimize the back reaction of Sat, enhance the intracellular pool of APS, and minimize the equilibration between sulfite and adenosine monophosphate (AMP). Both mutants, along with the wild type DvH were grown in batch culture made with water enriched in 18O. Samples were collected throughout batch growth, and we report the evolution of the S and O isotopic composition of sulfate, and of the S isotopic composition of sulfide. The results from this experiment will inform our understanding of the metabolic controls on the isotopic composition of seawater sulfate.

Americium, Cesium, and Plutonium Colloid-Facilitated Transport in a Groundwater/Bentonite/Fracture Fill Material System: Column Experiments and Model Results

NASA Astrophysics Data System (ADS)

Dittrich, T. M.; Boukhalfa, H.; Reimus, P. W.

2014-12-01

The objective of this study was to investigate and quantify the effects of desorption kinetics and colloid transport on radionuclides with different sorption affinities. We focused on quantifying transport mechanisms important for upscaling in time and distance. This will help determine the long-term fate and transport of radionuclides to aid in risk assessments. We selected a fractured/weathered granodiorite at the Grimsel Test Site (GTS) in Switzerland as a model crystalline rock repository system because the system has been thoroughly studied and field experiments involving radionuclides have already been conducted. Working on this system provides a unique opportunity to compare lab experiments with field-scale observations. Weathered fracture fill material (FFM) and bentonite used as backfill at the GTS were characterized (e.g., BET, SEM/EDS, QXRD), and batch and breakthrough column experiments were conducted. Solutions were prepared in synthetic groundwaters that matched the natural water chemistry. FFM samples were crushed, rinsed, sieved (150-355 μm), and equilibrated with synthetic groundwater. Bentonite was crushed, sodium-saturated, equilibrated with synthetic groundwater, and settled to yield a stable suspension. Suspensions were equilibrated with Am, Cs, or Pu. All experiments were conducted with Teflon®materials to limit sorption to system components. After radionuclide/colloid injections reached stability, radionuclide-free solutions were injected to observe the desorption and release behavior. Aliquots of effluent were measured for pH, colloid concentration, and total and dissolved radionuclides. Unanalyzed effluent from the first column was then injected through a second column of fresh material. The process was repeated for a third column and the results of all three breakthrough curves were modeled with a multi-site/multi-rate MATLAB code to elucidate the sorption rate coefficients and binding site densities of the bentonite colloids and fracture fill material. Nearly 50% of the sorbed Am was exchanged from the colloids to the fracture filling material in each of the three columns; whereas, less Cs and Pu was desorbed with each pass through a new column. Using a two-site kinetic model allowed for interrogation of desorption rates and dominant transport parameters.

Cryopreservation of epididymal sperm collected postmortem in the Tasmanian devil (Sarcophilus harrisii).

PubMed

Keeley, T; McGreevy, P D; O'Brien, J K

2012-07-15

Effective sperm cryopreservation protocols are limited to a small number of marsupial species. In this study, postmortem gamete rescue (PMGR) epididymal sperm samples from Tasmanian devils (N=34) euthanized due to the fatal Devil Facial Tumor Disease were used to develop long-term sperm storage techniques for the species. Cryoprotectant toxicity associated with equilibration of sperm samples in a TEST yolk diluent (TEST; 189 mM N-Tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid, 85 mM Trizma base [Tris], 11 mM glucose, 20% vol/vol egg yolk; pH 7.1, and 315.0±5.0 mOsm/kg) with a final concentration of 0.06 M trehalose, or 4%, 10%, and 18% vol/vol of either glycerol or dimethyl sulfoxide (DMSO), was examined over 12 h at 15 °C. Trehalose supplementation resulted in an immediate decline (P<0.05) of total motility. After 12 h, total motility was reduced (P<0.05) in treatments containing 18% glycerol, and 10% and 18% dimethyl sulfoxide. The effects of final glycerol concentration (4% and 10%), glycerol equilibration duration (10 min 1 h, or 3 h) prefreeze, freezing rate and the addition of 0.10 M lactose or a combination of 0.10 M lactose and 0.11 M raffinose were assessed during three experiments on the cryopreservation of postmortem gamete rescue samples in TEST. In all experiments, motility and viability were reduced (P<0.01 postthaw). Samples cryopreserved in TEST supplemented with lactose or lactose with raffinose using a fast freezing rate (-8 °C/min from 4 to -40 °C, then -65 °C/min until -165 °C) produced the highest (P<0.05) postthaw motility (18.6±5.5% and 16.9±8.5%, respectively), which represented 35% to 48% retention of prefreeze motility. These results apparently were the best postthaw results of dasyurid sperm reported to date and will help lay the foundations for developing assisted reproductive technologies for marsupial species. Copyright © 2012 Elsevier Inc. All rights reserved.

30 CFR 250.448 - What are the BOP pressure tests requirements?

Code of Federal Regulations, 2010 CFR

2010-07-01

... you pressure test the BOP system, you must conduct a low-pressure and a high-pressure test for each BOP component. You must conduct the low-pressure test before the high-pressure test. Each individual... zero and reinitiate the test. (b) High-pressure test for ram-type BOPs, the choke manifold, and other...

Method of high-precision microsampled blood and plasma mass densitometry

NASA Technical Reports Server (NTRS)

Hinghofer-Szalkay, H.

1986-01-01

The reliability of the mechanical oscillator technique for blood and plasma density measurements on samples of volumes less than 0.1 ml is examined, and a precision of 0.001 g/l is found if plasma-isodensic heparin solution and siliconized densitometers are employed. Sources of measurement errors in the density determinations include storage of plasma samples, inhomogeneity of blood samples, and density reading before adequate temperature equilibration. In tests of plasma sample storage, the best reproducibility was obtained with samples kept at 4 C. Linear correlations were found between plasma density and plasma protein concentration, blood density and blood hemoglobin concentration, and erythrocyte density and MCHC.

Recovery of mechanical pressure in a gas of underdamped active dumbbells with Brownian noise

NASA Astrophysics Data System (ADS)

Joyeux, Marc

2017-05-01

In contrast with a gas at thermodynamic equilibrium, the mean force exerted on a wall by a gas of active particles usually depends on the confining potential, thereby preventing a proper definition of mechanical pressure. In this paper, we investigate numerically the properties of a gas of underdamped self-propelled dumbbells subject to Brownian noise of increasing intensity, in order to understand how the notion of pressure is recovered as noise progressively masks the effects of self-propulsion and the system approaches thermodynamic equilibrium. The simulations performed for a mobile asymmetric wall separating two chambers containing an equal number of active dumbbells highlight some subtle and unexpected properties of the system. First, Brownian noise of moderate intensity is sufficient to let mean forces equilibrate for small values of the damping coefficient, while much stronger noise is required for larger values of the damping coefficient. Moreover, the displacement of the mean position of the wall upon increase of the intensity of the noise is not necessarily monotonous and may instead display changes of direction. Both facts actually reflect the existence of several mechanisms leading to the rupture of force balance, which tend to displace the mean position of the wall towards different directions and display different robustness against an increase of the intensity of Brownian noise. This work therefore provides a clear illustration of the fact that driving an autonomous system towards (or away from) thermodynamic equilibrium may not be a straightforward process, but may instead proceed through the variations of the relative weights of several conflicting mechanisms.

Passive shut-down heat removal system

DOEpatents

Hundal, Rolv; Sharbaugh, John E.

1988-01-01

An improved shut-down heat removal system for a liquid metal nuclear reactor of the type having a vessel for holding hot and cold pools of liquid sodium is disclosed herein. Generally, the improved system comprises a redan or barrier within the reactor vessel which allows an auxiliary heat exchanger to become immersed in liquid sodium from the hot pool whenever the reactor pump fails to generate a metal-circulating pressure differential between the hot and cold pools of sodium. This redan also defines an alternative circulation path between the hot and cold pools of sodium in order to equilibrate the distribution of the decay heat from the reactor core. The invention may take the form of a redan or barrier that circumscribes the inner wall of the reactor vessel, thereby defining an annular space therebetween. In this embodiment, the bottom of the annular space communicates with the cold pool of sodium, and the auxiliary heat exchanger is placed in this annular space just above the drawn-down level that the liquid sodium assumes during normal operating conditions. Alternatively, the redan of the invention may include a pair of vertically oriented, concentrically disposed standpipes having a piston member disposed between them that operates somewhat like a pressure-sensitive valve. In both embodiments, the cessation of the pressure differential that is normally created by the reactor pump causes the auxiliary heat exchanger to be immersed in liquid sodium from the hot pool. Additionally, the redan in both embodiments forms a circulation flow path between the hot and cold pools so that the decay heat from the nuclear core is uniformly distributed within the vessel.

Managing patients with stable respiratory disease planning air travel: a primary care summary of the British Thoracic Society recommendations.

PubMed

Josephs, Lynn K; Coker, Robina K; Thomas, Mike

2013-06-01

Air travel poses medical challenges to passengers with respiratory disease, principally because of exposure to a hypobaric environment. In 2002 the British Thoracic Society published recommendations for adults and children with respiratory disease planning air travel, with a web update in 2004. New full recommendations and a summary were published in 2011, containing key recommendations for the assessment of high-risk patients and identification of those likely to require in-flight supplemental oxygen. This paper highlights the aspects of particular relevance to primary care practitioners with the following key points: (1) At cabin altitudes of 8000 feet (the usual upper limit of in-flight cabin pressure, equivalent to 0.75 atmospheres) the partial pressure of oxygen falls to the equivalent of breathing 15.1% oxygen at sea level. Arterial oxygen tension falls in all passengers; in patients with respiratory disease, altitude may worsen preexisting hypoxaemia. (2) Altitude exposure also influences the volume of any air in cavities, where pressure x volume remain constant (Boyle's law), so that a pneumothorax or closed lung bulla will expand and may cause respiratory distress. Similarly, barotrauma may affect the middle ear or sinuses if these cavities fail to equilibrate. (3) Patients with respiratory disease require clinical assessment and advice before air travel to: (a) optimise usual care; (b) consider contraindications to travel and possible need for in-flight oxygen; (c) consider the need for secondary care referral for further assessment; (d) discuss the risk of venous thromboembolism; and (e) discuss forward planning for the journey.

Protein Equilibration through Somatic Ring Canals in Drosophila

PubMed Central

McLean, Peter F.; Cooley, Lynn

2013-01-01

Although intercellular bridges resulting from incomplete cytokinesis were discovered in somatic Drosophila tissues decades ago, the impact of these structures on intercellular communication and tissue biology is largely unknown. In this work, we demonstrate that the ~250 nm diameter somatic ring canals permit diffusion of cytoplasmic contents between connected cells and across mitotic clone boundaries, and enable the equilibration of protein between transcriptionally mosaic follicle cells in the Drosophila ovary. We obtained similar, though more restricted, results in the larval imaginal discs. Our work illustrates the lack of cytoplasmic autonomy in these tissues and suggests a role for somatic ring canals in promoting homogeneous protein expression within the tissue. PMID:23704373

Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System.

PubMed

Paredes, Ricardo; Fariñas-Sánchez, Ana Isabel; Medina-Rodrı Guez, Bryan; Samaniego, Samantha; Aray, Yosslen; Álvarez, Luis Javier

2018-03-06

The process of equilibration of the tetradecane-water interface in the presence of sodium hexadecane-benzene sulfonate is studied using intensive atomistic molecular dynamics simulations. Starting as an initial point with all of the surfactants at the interface, it is obtained that the equilibration time of the interface (several microseconds) is orders of magnitude higher than previously reported simulated times. There is strong evidence that this slow equilibration process is due to the aggregation of surfactants molecules on the interface. To determine this fact, temporal evolution of interfacial tension and interfacial formation energy are studied and their temporal variations are correlated with cluster formation. To study cluster evolution, the mean cluster size and the probability that a molecule of surfactant chosen at random is free are obtained as a function of time. Cluster size distribution is estimated, and it is observed that some of the molecules remain free, whereas the rest agglomerate. Additionally, the temporal evolution of the interfacial thickness and the structure of the surfactant molecules on the interface are studied. It is observed how this structure depends on whether the molecules agglomerate or not.

Triplet Excitation Transfer between Carotenoids in the LH2 Complex from Photosynthetic Bacterium Rhodopseudomonas palustris.

PubMed

Feng, Juan; Wang, Qian; Wu, Yi-Shi; Ai, Xi-Cheng; Zhang, Xu-Jia; Huang, You-Guo; Zhang, Xing-Kang; Zhang, Jian-Ping

2004-01-01

We have studied, by means of sub-microsecond time-resolved absorption spectroscopy, the triplet-excited state dynamics of carotenoids (Cars) in the intermediate-light adapted LH2 complex (ML-LH2) from Rhodopseudomonas palustris containing Cars with different numbers of conjugated double bonds. Following pulsed photo-excitation at 590 nm at room temperature, rapid spectral equilibration was observed either as a red shift of the isosbestic wavelength on a time scale of 0.6-1.0 mus, or as a fast decay in the shorter-wavelength side of the T(n)<--T(1) absorption of Cars with a time constant of 0.5-0.8 mus. Two major spectral components assignable to Cars with 11 and 12 conjugated double bonds were identified. The equilibration was not observed in the ML-LH2 at 77 K, or in the LH2 complex from Rhodobacter sphaeroides G1C containing a single type of Car. The unique spectral equilibration was ascribed to temperature-dependent triplet excitation transfer among different Car compositions. The results suggest that Cars of 11 and 12 conjugated bonds, both in close proximity of BChls, may coexist in an alpha,beta-subunit of the ML-LH2 complex.

Fluid flow in deforming media: interpreting stable isotope signatures of marbles

NASA Astrophysics Data System (ADS)

Bond, C. E.

2016-12-01

Fluid flow in the crust is controlled by permeable networks. These networks can be created and destroyed dynamically during rock deformation. Rock deformation is therefore critical in controlling fluid pathways in the crust and hence the location of mineral and other resources. Here, evidence for deformation-enhanced fluid infiltration shows that a range of deformation mechanisms control fluid flow and chemical and isotopic equilibration. The results attest to localised fluid infiltration within a single metamorphic terrain (12km) over a range of metamorphic grades; ecologite- blueschist to greenschist. For fluid infiltrating marbles during ductile deformation, chemical and isotopic signatures are now homogenous; whilst fluid infiltration associated with brittle deformation results in chemical and isotopic heterogeneity at a microscale. The findings demonstrate how ductile deformation enhances equilibration of δ18O at a grain scale whilst brittle deformation does not. The control of deformation mechanisms in equilibrating isotopic and chemical heterogeneities have implications for the understanding of fluid-rock interaction in the crust. Interpretation of bulk stable isotope data, particularly in the use of isotope profiles to determine fluid fluxes into relatively impermeable units that have been deformed need to be used with care when trying to determine fluid fluxes and infiltration mechanisms.

Laboratory investigations of stable carbon and oxygen isotope ratio data enhance monitoring of CO2 underground

NASA Astrophysics Data System (ADS)

Barth, Johannes A. C.; Myrttinen, Anssi; Becker, Veith; Nowak, Martin; Mayer, Bernhard

2014-05-01

Stable carbon and oxygen isotope data play an important role in monitoring CO2 in the subsurface, for instance during carbon capture and storage (CCS). This includes monitoring of supercritical and gaseous CO2 movement and reactions under reservoir conditions and detection of potential CO2 leakage scenarios. However, in many cases isotope data from field campaigns are either limited due to complex sample retrieval or require verification under controlled boundary conditions. Moreover, experimentally verified isotope fractionation factors are also accurately known only for temperatures and pressures lower than commonly found in CO2 reservoirs (Myrttinen et al., 2012). For this reason, several experimental series were conducted in order to investigate effects of elevated pressures, temperatures and salinities on stable carbon and oxygen isotope changes of CO2 and water. These tests were conducted with a heateable pressure device and with glass or metal gas containers in which CO2 reacted with fluids for time periods of hours to several weeks. The obtained results revealed systematic differences in 13C/12C-distributions between CO2 and the most important dissolved inorganic carbon (DIC) species under reservoir conditions (CO2(aq), H2CO3 and HCO3-). Since direct measurements of the pH, even immediately after sampling, were unreliable due to rapid CO2 de-gassing, one of the key results of this work is that carbon isotope fractionation data between DIC and CO2 may serve to reconstruct in situ pH values. pH values reconstructed with this approach ranged between 5.5 and 7.4 for experiments with 60 bars and up to 120 °C and were on average 1.4 pH units lower than those measured with standard pH electrodes directly after sampling. In addition, pressure and temperature experiments with H2O and CO2 revealed that differences between the oxygen isotope ratios of both phases depended on temperature, water-gas ratios as well as salt contents of the solutions involved. Such systematic knowledge of the extent of oxygen isotope fractionation between H2O and CO2 can help to reconstruct equilibration times, fluid-CO2 ratios as well as temperature and salinity conditions. Isotope results from systematic laboratory studies and the information they provide for assessing in situ reservoir conditions can be transferred to field applications concerning integrity of CO2 reservoirs. They can also apply to natural systems and other industrial uses that involve monitoring of gases in the subsurface under similar pressure and temperature conditions. Reference: Myrttinen, A., Becker, V., Barth, J.A.C., 2012. A review of methods used for equilibrium isotope fractionation investigations between dissolved inorganic carbon and CO2. Earth-Science Reviews, 115(3): 192-199.

49 CFR 195.304 - Test pressure.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Test pressure. 195.304 Section 195.304... PIPELINE Pressure Testing § 195.304 Test pressure. The test pressure for each pressure test conducted under... case of a pipeline that is not visually inspected for leakage during the test, for at least an...

Estimation of phenolic conjugation by colonic mucosa.

PubMed Central

Ramakrishna, B S; Gee, D; Weiss, A; Pannall, P; Roberts-Thomson, I C; Roediger, W E

1989-01-01

Conjugation of phenol by the colonic mucosa was assessed in vivo using dialysis tubing containing 1.5 ml of 1 mmol/l acetaminophen (paracetamol) and 10 mmol/l butyrate. These were allowed to equilibrate in the rectum for one hour. The glucuronidated and sulphated conjugates of acetaminophen were measured by high pressure liquid chromatography and bicarbonate concentrations by gas analysis. In 21 subjects without colonic disease sulphate conjugation was observed in all cases, with a mean (SE) of 3.86 (0.66) nmol/hour, while glucuronide conjugation was found in seven of 21 cases. Mean (SE) bicarbonate output of 42.9 (3.9) mumol/hour (n = 21) indicated healthy colonic mucosal metabolism and phenolic sulphation in dialysate and agreed with published sulphation rates obtained with cultured cells of colonic epithelium. Acetaminophen sulphation suggests that the colonic mucosa has an important role in the conjugation of phenols, and the method reported here would be useful in assessing the detoxification capacity of the colonic mucosa in diseases of the rectal mucosa. PMID:2738167

Integrated Experimental and Modelling Research for Non-Ferrous Smelting and Recycling Systems

NASA Astrophysics Data System (ADS)

Jak, Evgueni; Hidayat, Taufiq; Shishin, Denis; Mehrjardi, Ata Fallah; Chen, Jiang; Decterov, Sergei; Hayes, Peter

The chemistries of industrial pyrometallurgical non-ferrous smelting and recycling processes are becoming increasingly complex. Optimisation of process conditions, charge composition, temperature, oxygen partial pressure, and partitioning of minor elements between phases and different process streams require accurate description of phase equilibria and thermodynamics which are the focus of the present research. The experiments involve high temperature equilibration in controlled gas atmospheres, rapid quenching and direct measurement of equilibrium phase compositions with quantitative microanalytical techniques including electron probe X-ray microanalysis and Laser Ablation ICP-MS. The thermodynamic modelling is undertaken using computer package FactSage with the quasi-chemical model for the liquid slag phase and other advanced models. Experimental and modelling studies are combined into an integrated research program focused on the major elements Cu-Pb-Fe-O-Si-S system, slagging Al, Ca, Mg and other minor elements. The ongoing development of the research methodologies has resulted in significant advances in research capabilities. Examples of applications are given.

Tracing high-pressure metamorphism in marbles: Phase relations in high-grade aluminous calcite-dolomite marbles from the Greek Rhodope massif in the system CaO-MgO-Al 2O 3-SiO 2-CO 2 and indications of prior aragonite

NASA Astrophysics Data System (ADS)

Proyer, A.; Mposkos, E.; Baziotis, I.; Hoinkes, G.

2008-08-01

Four different types of parageneses of the minerals calcite, dolomite, diopside, forsterite, spinel, amphibole (pargasite), (Ti-)clinohumite and phlogopite were observed in calcite-dolomite marbles collected in the Kimi-Complex of the Rhodope Metamorphic Province (RMP). The presence of former aragonite can be inferred from carbonate inclusions, which, in combination with an analysis of phase relations in the simplified system CaO-MgO-Al 2O 3-SiO 2-CO 2 (CMAS-CO 2) show that the mineral assemblages preserved in these marbles most likely equilibrated at the aragonite-calcite transition, slightly below the coesite stability field, at ca. 720 °C, 25 kbar and aCO 2 ~ 0.01. The thermodynamic model predicts that no matter what activity of CO 2, garnet has to be present in aluminous calcite-dolomite-marble at UHP conditions.

Experimental Investigation of Gas/Slag/Matte/Spinel Equilibria in the Cu-Fe-O-S-Si System at 1473 K (1200 °C) and P(SO2) = 0.25 atm

NASA Astrophysics Data System (ADS)

Hidayat, Taufiq; Fallah-Mehrjardi, Ata; Hayes, Peter C.; Jak, Evgueni

2018-04-01

New experimental data were obtained on the gas/slag/matte/spinel equilibria in the Cu-Fe-O-S-Si system at 1473 K (1200 °C) and P(SO2) = 0.25 atm covering Cu concentrations in matte between 42 and 78 wt pct Cu. Accurate measurements were obtained using high-temperature equilibration and the rapid quenching technique, followed by electron-probe X-ray microanalysis of equilibrium phase compositions. The use of spinel substrates made to support the samples ensures equilibrium with this primary phase solid, eliminates crucible contamination, and facilitates direct gas-condensed phase equilibrium and high quenching rates. Particular attention was given to the confirmation of the achievement of equilibrium. The results quantify the relationship between Cu in matte and oxygen partial pressure, sulfur in matte, oxygen in matte, Fe/SiO2 at slag liquidus, sulfur in slag, and dissolved copper in slag.

Surface defect chemistry and oxygen exchange kinetics in La2-xCaxNiO4+δ

NASA Astrophysics Data System (ADS)

Tropin, E. S.; Ananyev, M. V.; Farlenkov, A. S.; Khodimchuk, A. V.; Berenov, A. V.; Fetisov, A. V.; Eremin, V. A.; Kolchugin, A. A.

2018-06-01

Surface oxygen exchange kinetics and diffusion in La2-xCaxNiO4+δ (x = 0; 0.1; 0.3) have been studied by the isotope exchange method with gas phase equilibration in the temperature range of 600-800 °C and oxygen pressure range 0.13-2.5 kPa. Despite an enhanced electrical conductivity of La2-xCaxNiO4+δ theirs oxygen surface exchange (k*) and oxygen tracer diffusion (D*) coefficients were significantly lower in comparison with La2NiO4+δ. The rates of the elementary stages of oxygen exchange have been calculated. Upon Ca doping the change of the rate-determining stage was observed. The surface of the oxides was found to be inhomogeneous towards oxygen exchange process according to the recently developed model. The reasons of such inhomogeneity are discussed as well as Ca influence on the surface defect chemistry and oxygen surface exchange and diffusivity.