Thermodynamic models for bounding pressurant mass requirements of cryogenic tanks

NASA Technical Reports Server (NTRS)

Vandresar, Neil T.; Haberbusch, Mark S.

1994-01-01

Thermodynamic models have been formulated to predict lower and upper bounds for the mass of pressurant gas required to pressurize a cryogenic tank and then expel liquid from the tank. Limiting conditions are based on either thermal equilibrium or zero energy exchange between the pressurant gas and initial tank contents. The models are independent of gravity level and allow specification of autogenous or non-condensible pressurants. Partial liquid fill levels may be specified for initial and final conditions. Model predictions are shown to successfully bound results from limited normal-gravity tests with condensable and non-condensable pressurant gases. Representative maximum collapse factor maps are presented for liquid hydrogen to show the effects of initial and final fill level on the range of pressurant gas requirements. Maximum collapse factors occur for partial expulsions with large final liquid fill fractions.

Effect of pressure on the Raman-active modes of zircon (ZrSiO4): a first-principles study

NASA Astrophysics Data System (ADS)

Sheremetyeva, Natalya; Cherniak, Daniele J.; Watson, E. Bruce; Meunier, Vincent

2018-02-01

Density-functional theory (DFT) was employed in a first-principles study of the effects of pressure on the Raman-active modes of zircon (ZrSiO4), using both the generalized gradient and local density approximations (GGA and LDA, respectively). Beginning with the equilibrium structure at zero pressure, we conducted a calibration of the effect of pressure in a manner procedurally similar to an experimental calibration. For pressures between 0 and 7 GPa, we find excellent qualitative agreement of frequency-pressure slopes partial ω /partial P calculated from GGA DFT with results of previous experimental studies. In addition, we were able to rationalize the ω vs. P behavior based on details of the vibrational modes and their atomic displacements. Most of the partial ω /partial P slopes are positive as expected, but the symmetry of the zircon lattice also results in two negative slopes for modes that involve slight shearing and rigid rotation of SiO4 tetrahedra. Overall, LDA yields absolute values of the frequencies of the Raman-active modes in good agreement with experimental values, while GGA reproduces the shift in frequency with pressure especially well.

Isochoric Burn, an Internally Consistent Method for the Reactant to Product Transformation in Reactive Flow

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

Reaugh, J E; Lee, E L

2002-07-01

Mixture rules for partially reacted explosives differ amongst various models. For instance, JWL++ uses a partial pressure addition to compute an average zonal pressure, Ignition and Growth requires pressure equilibration and thermal equilibration of temperature dependent JWL EOSs, CHEETAH In Line RF also assumes temperature and pressure equilibration. It has been suggested in the past that a more realistic equilibration scheme should comprise isentropic pressure equilibration of the separate reacted and unreacted phases. This turns out not to be a proper path for equilibration. Rather, we find that the only internally consistent method is the evaluation of the equilibrium pressuremore » that satisfies the particular conditions of reactant and product resulting from deflagration in a fixed volume.« less

Effect of Group-III precursors on unintentional gallium incorporation during epitaxial growth of InAlN layers by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Jeomoh; Ji, Mi-Hee; Detchprohm, Theeradetch; Dupuis, Russell D.; Fischer, Alec M.; Ponce, Fernando A.; Ryou, Jae-Hyun

2015-09-01

Unintentional incorporation of gallium (Ga) in InAlN layers grown with different molar flow rates of Group-III precursors by metalorganic chemical vapor deposition has been experimentally investigated. The Ga mole fraction in the InAl(Ga)N layer was increased significantly with the trimethylindium (TMIn) flow rate, while the trimethylaluminum flow rate controls the Al mole fraction. The evaporation of metallic Ga from the liquid phase eutectic system between the pyrolized In from injected TMIn and pre-deposited metallic Ga was responsible for the Ga auto-incorporation into the InAl(Ga)N layer. The theoretical calculation on the equilibrium vapor pressure of liquid phase Ga and the effective partial pressure of Group-III precursors based on growth parameters used in this study confirms the influence of Group-III precursors on Ga auto-incorporation. More Ga atoms can be evaporated from the liquid phase Ga on the surrounding surfaces in the growth chamber and then significant Ga auto-incorporation can occur due to the high equilibrium vapor pressure of Ga comparable to effective partial pressure of input Group-III precursors during the growth of InAl(Ga)N layer.

Metastable superheated ice in liquid-water inclusions under high negative pressure

USGS Publications Warehouse

Roedder, E.

1967-01-01

In some microscopic inclusions (consisting of aqueous liquid and vapor) in minerals, freezing eliminates the vapor phase because of greater volume occupied by the resulting ice. When vapor fails to nucleate again on partial melting, the resulting negative pressure (hydrostatic tension) inside the inclusions permits the existence of ice I crystals under reversible, metastable equilibrium, at temperatures as high as +6.5??C and negative pressures possibly exceeding 1000 bars.

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 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.

Finite-size versus interface-proximity effects in thin-film epitaxial SrTiO3

NASA Astrophysics Data System (ADS)

De Souza, R. A.; Gunkel, F.; Hoffmann-Eifert, S.; Dittmann, R.

2014-06-01

The equilibrium electrical conductivity of epitaxial SrTiO3 (STO) thin films was investigated as a function of temperature, 950≤ T/K ≤1100, and oxygen partial pressure, 10-23≤ pO2/bar ≤1. Compared with single-crystal STO, nanoscale thin-film STO exhibited with decreasing film thickness an increasingly enhanced electronic conductivity under highly reducing conditions, with a corresponding decrease in the activation enthalpy of conduction. This implies substantial modification of STO's point-defect thermodynamics for nanoscale film thicknesses. We argue, however, against such a finite-size effect and for an interface-proximity effect. Indeed, assuming trapping of oxygen vacancies at the STO surface and concomitant depletion of oxygen vacancies—and accumulation of electrons—in an equilibrium surface space-charge layer, we are able to predict quantitatively the conductivity as a function of temperature, oxygen partial pressure, and film thickness. Particularly complex behavior is predicted for ultrathin films that are consumed entirely by space charge.

The change of steel surface chemistry regarding oxygen partial pressure and dew point

NASA Astrophysics Data System (ADS)

Norden, Martin; Blumenau, Marc; Wuttke, Thiemo; Peters, Klaus-Josef

2013-04-01

By investigating the surface state of a Ti-IF, TiNb-IF and a MnCr-DP after several series of intercritical annealing, the impact of the annealing gas composition on the selective oxidation process is discussed. On behalf of the presented results, it can be concluded that not the general oxygen partial pressure in the annealing furnace, which is a result of the equilibrium reaction of water and hydrogen, is the main driving force for the selective oxidation process. It is shown that the amounts of adsorbed gases at the strip surface and the effective oxygen partial pressure resulting from the adsorbed gases, which is mainly dependent on the water content of the annealing furnace, is driving the selective oxidation processes occurring during intercritical annealing. Thus it is concluded, that for industrial applications the dew point must be the key parameter value for process control.

Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics.

PubMed

Zhu, Huayang; Ricote, Sandrine; Coors, W Grover; Kee, Robert J

2015-01-01

A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst-Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst-Planck-Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

Effect of Group-III precursors on unintentional gallium incorporation during epitaxial growth of InAlN layers by metalorganic chemical vapor deposition

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

Kim, Jeomoh, E-mail: jkim610@gatech.edu; Ji, Mi-Hee; Detchprohm, Theeradetch

2015-09-28

Unintentional incorporation of gallium (Ga) in InAlN layers grown with different molar flow rates of Group-III precursors by metalorganic chemical vapor deposition has been experimentally investigated. The Ga mole fraction in the InAl(Ga)N layer was increased significantly with the trimethylindium (TMIn) flow rate, while the trimethylaluminum flow rate controls the Al mole fraction. The evaporation of metallic Ga from the liquid phase eutectic system between the pyrolized In from injected TMIn and pre-deposited metallic Ga was responsible for the Ga auto-incorporation into the InAl(Ga)N layer. The theoretical calculation on the equilibrium vapor pressure of liquid phase Ga and the effectivemore » partial pressure of Group-III precursors based on growth parameters used in this study confirms the influence of Group-III precursors on Ga auto-incorporation. More Ga atoms can be evaporated from the liquid phase Ga on the surrounding surfaces in the growth chamber and then significant Ga auto-incorporation can occur due to the high equilibrium vapor pressure of Ga comparable to effective partial pressure of input Group-III precursors during the growth of InAl(Ga)N layer.« less

Steady-State Plant Model to Predict Hydroden Levels in Power Plant Components

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

Glatzmaier, Greg C.; Cable, Robert; Newmarker, Marc

The National Renewable Energy Laboratory (NREL) and Acciona Energy North America developed a full-plant steady-state computational model that estimates levels of hydrogen in parabolic trough power plant components. The model estimated dissolved hydrogen concentrations in the circulating heat transfer fluid (HTF), and corresponding partial pressures within each component. Additionally for collector field receivers, the model estimated hydrogen pressure in the receiver annuli. The model was developed to estimate long-term equilibrium hydrogen levels in power plant components, and to predict the benefit of hydrogen mitigation strategies for commercial power plants. Specifically, the model predicted reductions in hydrogen levels within the circulatingmore » HTF that result from purging hydrogen from the power plant expansion tanks at a specified target rate. Our model predicted hydrogen partial pressures from 8.3 mbar to 9.6 mbar in the power plant components when no mitigation treatment was employed at the expansion tanks. Hydrogen pressures in the receiver annuli were 8.3 to 8.4 mbar. When hydrogen partial pressure was reduced to 0.001 mbar in the expansion tanks, hydrogen pressures in the receiver annuli fell to a range of 0.001 mbar to 0.02 mbar. When hydrogen partial pressure was reduced to 0.3 mbar in the expansion tanks, hydrogen pressures in the receiver annuli fell to a range of 0.25 mbar to 0.28 mbar. Our results show that controlling hydrogen partial pressure in the expansion tanks allows us to reduce and maintain hydrogen pressures in the receiver annuli to any practical level.« less

Method of forming cavitated objects of controlled dimension

DOEpatents

Anderson, Paul R.; Miller, Wayne J.

1982-01-01

A method of controllably varying the dimensions of cavitated objects such as hollow spherical shells wherein a precursor shell is heated to a temperature above the shell softening temperature in an ambient atmosphere wherein the ratio of gases which are permeable through the shell wall at that temperature to gases which are impermeable through the shell wall is substantially greater than the corresponding ratio for gases contained within the precursor shell. As the shell expands, the partial pressures of permeable gases internally and externally of the shell approach and achieve equilibrium, so that the final shell size depends solely upon the difference in impermeable gas partial pressures and shell surface tension.

Development of a low-pressure materials pre-treatment process for improved energy efficiency

NASA Astrophysics Data System (ADS)

Lee, Kwanghee; You, Byung Don

2017-09-01

Low pressure materials pre-treatment process has been developed as an alternative to the existing high-temperature sludge drying, limestone calcination, and limonite dehydroxylation. Using the thermodynamic equilibrium relationship between temperature and pressure represented by the Clausius-Clapeyron equation, the operational temperature of these reactions could be lowered at reduced pressure for increased energy efficiency. For industrial sludge drying, the evaporation rate was controlled by interfacial kinetics showing a constant rate with time and significant acceleration in the reaction could be observed with reduced pressure. At this modified reaction rate under low pressure, the rate was also partially controlled by mass transfer. Temperature of limestone calcination was lowered, but the reaction was limited at the calculated equilibrium temperature of the Clausius-Clapeyron equation and slightly higher temperatures were required. The energy consumption during limestone calcination and limonite dehydroxylation were evaluated, where lower processing pressures could enhance the energy efficiency for limestone calcination, but limonite dehydroxylation could not achieve energy-savings due to the greater power consumption of the vacuum pump under lower pressure and reduced temperatures.

Discussion of enthalpy, entropy and free energy of formation of GaN

NASA Astrophysics Data System (ADS)

Jacob, K. T.; Rajitha, G.

2009-07-01

Presented in this letter is a critical discussion of a recent paper on experimental investigation of the enthalpy, entropy and free energy of formation of gallium nitride (GaN) published in this journal [T.J. Peshek, J.C. Angus, K. Kash, J. Cryst. Growth 311 (2008) 185-189]. It is shown that the experimental technique employed detects neither the equilibrium partial pressure of N 2 corresponding to the equilibrium between Ga and GaN at fixed temperatures nor the equilibrium temperature at constant pressure of N 2. The results of Peshek et al. are discussed in the light of other information on the Gibbs energy of formation available in the literature. Entropy of GaN is derived from heat-capacity measurements. Based on a critical analysis of all thermodynamic information now available, a set of optimized parameters is identified and a table of thermodynamic data for GaN developed from 298.15 to 1400 K.

Aerothermodynamic radiation studies

NASA Technical Reports Server (NTRS)

Donohue, K.; Reinecke, W. G.; Rossi, D.; Marinelli, W. J.; Krech, R. H.; Caledonia, G. E.

1991-01-01

We have built and made operational a 6 in. electric arc driven shock tube which alloys us to study the non-equilibrium radiation and kinetics of low pressure (0.1 to 1 torr) gases processed by 6 to 12 km/s shock waves. The diagnostic system allows simultaneous monitoring of shock radiation temporal histories by a bank of up to six radiometers, and spectral histories with two optical multi-channel analyzers. A data set of eight shots was assembled, comprising shocks in N2 and air at pressures between 0.1 and 1 torr and velocities of 6 to 12 km/s. Spectrally resolved data was taken in both the non-equilibrium and equilibrium shock regions on all shots. The present data appear to be the first spectrally resolved shock radiation measurements in N2 performed at 12 km/s. The data base was partially analyzed with salient features identified.

Physical properties of the stratospheric aerosols

NASA Technical Reports Server (NTRS)

Toon, O. B.; Pollack, J. B.

1973-01-01

A comparison of the equilibrium vapor pressure over nitric acid solutions with observed water and nitric acid partial pressures in the stratosphere implies that nitric acid cannot be present as an aerosol particle in the lower stratosphere. A similar comparison for sulfuric acid solutions indicates that sulfuric acid aerosol particles are 75% H2SO4 by weight in water, in good agreement with direct observations. The freezing curve of H2SO4 solutions requires that the H2SO4 aerosol particles be solid or supercooled. The equilibrium vapor pressure of H2SO4 in the stratosphere is of the order of 20 picotorr. At stratospheric temperatures, ammonium sulfate is in a ferroelectric phase. As a result, polar molecules may form a surface coating on these aerosols, which may be a fertile ground for further chemical reaction.

Capacity retention in hydrogen storage alloys

NASA Technical Reports Server (NTRS)

Anani, A.; Visintin, A.; Srinivasan, S.; Appleby, A. J.; Reilly, J. J.; Johnson, J. R.

1992-01-01

Results of our examination of the properties of several candidate materials for hydrogen storage electrodes and their relation to the decrease in H-storage capacity upon open-circuit storage over time are reported. In some of the alloy samples examined to date, only about 10 percent of the hydrogen capacity was lost upon storage for 20 days, while in others, this number was as high as 30 percent for the same period of time. This loss in capacity is attributed to two separate mechanisms: (1) hydrogen desorbed from the electrode due to pressure differences between the cell and the electrode sample; and (2) chemical and/or electrochemical degradation of the alloy electrode upon exposure to the cell environment. The former process is a direct consequence of the equilibrium dissociation pressure of the hydride alloy phase and the partial pressure of hydrogen in the hydride phase in equilibrium with that in the electrolyte environment, while the latter is related to the stability of the alloy phase in the cell environment. Comparison of the equilibrium gas-phase dissociation pressures of these alloys indicate that reversible loss of hydrogen capacity is higher in alloys with P(eqm) greater than 1 atm than in those with P(eqm) less than 1 atm.

Gas-liquid equilibrium in a CO{sub 2}-MDEA-H{sub 2}O system and the effect of piperazine on it

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

Xu, G.W.; Zhang, C.F.; Qin, S.J.

1998-04-01

Aqueous N-methyldiethanolamine (MDEA) solutions are widely used for removal of the acid gas (H{sub 2}S and CO{sub 2}) from natural gas synthesis and refinery gas streams. Solubility data of CO{sub 2} and vapor pressure of water in 3.04--4.28 kmol/m{sup 3} aqueous N-methyldiethanolamine (MDEA) solutions were obtained at temperatures ranging from 40 to 100 C and CO{sub 2} partial pressures ranging from 0.876 to 1,013 kPa. A thermodynamic model was proposed and used for predicting CO{sub 2} solubility and water vapor pressure. An enthalpy change of absorption of CO{sub 2} in 4.28 kmol/m{sup 3} MDEA solution was estimated. The effect ofmore » piperazine (PZ) concentration on CO{sub 2} loading in MDEA solutions was determined at piperazine concentration ranging from 0 to 0.515 kmol/m{sup 3}. The results show that piperazine is beneficial to the CO{sub 2} loading. The equilibrium partial pressure of piperazine in the PZ-MDEA-H{sub 2}O system was measured in an Ellis Cell. Results show that the PZ-MDEA-H{sub 2}O system is a typical negative deviation system, with the strength of deviation decreasing with MDEA solutions.« less

Investigation of uranium plasma emission from 1050 to 6000 A

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

Mack, J.M. Jr.

1977-12-01

Absolute emission coefficient measurements on arc-generated uranium plasmas in local thermodynamic equilibrium are described for a wavelength bandwidth of 1050 to 6000A. Low- and high-pressure arcs were investigated for their emission properties, characteristic temperatures and uranium partial pressures. Temperatures from 5500 to 8000 K and uranium partial pressures from 0.001 to 0.01 atm were found at the arc centerline. The new emission data are compared with other similar experimental results and to existing theoretical calculations. The effects of cold-layer UF/sub 6/ photoabsorption on uranium plasma emission characteristics are established for UF/sub 6/ molecular densities ranging from 1.0 x 10/sup 16/more » to 1.0 x 10/sup 17/ cm/sup -3/ and layer thickness from 1.0 to 5.0 cm.« less

Thermodynamic Equilibrium Solubility of Diethanolamine – N-Butyl-1-Methylpyrrolidinium Dicyanamide [DEABMPYRR DCA] Mixtures for Carbon Dioxide Capture

NASA Astrophysics Data System (ADS)

Salleh, R. M.; Jamaludin, S. N.

2018-05-01

Solubility data of carbon dioxide (CO2) in aqueous Diethanolamine (DEA) blended with pyrrolidinium-based ionic liquid: N-Butyl-1-Methylpyrrolidinium Dıcyanamıde [Bmpyrr][DCA] are presented at various temperatures (313.15K-333.15K) and pressure up to about 700 psi. The concentration of [Bmpyrr][DCA] ranges from 0-10wt% and 30-40wt% for DEA. The solubility of CO2 was evaluated by measuring the pressure drop in high pressure stirred absorption cell reactor. The CO2 loading in all studied mixtures increases with an increase in CO2 partial pressure and decreases with temperature. It was also found that the CO2 loading capacity decrease as the concentration of [Bmpyrr][DCA] increases. The experimental data were correlated as a function of temperature and CO2 partial pressure to predict the solubility of CO2 in the mixtures. It was found that the model predicted results in a good agreement with experimental value.

Conservative-variable average states for equilibrium gas multi-dimensional fluxes

NASA Technical Reports Server (NTRS)

Iannelli, G. S.

1992-01-01

Modern split component evaluations of the flux vector Jacobians are thoroughly analyzed for equilibrium-gas average-state determinations. It is shown that all such derivations satisfy a fundamental eigenvalue consistency theorem. A conservative-variable average state is then developed for arbitrary equilibrium-gas equations of state and curvilinear-coordinate fluxes. Original expressions for eigenvalues, sound speed, Mach number, and eigenvectors are then determined for a general average Jacobian, and it is shown that the average eigenvalues, Mach number, and eigenvectors may not coincide with their classical pointwise counterparts. A general equilibrium-gas equation of state is then discussed for conservative-variable computational fluid dynamics (CFD) Euler formulations. The associated derivations lead to unique compatibility relations that constrain the pressure Jacobian derivatives. Thereafter, alternative forms for the pressure variation and average sound speed are developed in terms of two average pressure Jacobian derivatives. Significantly, no additional degree of freedom exists in the determination of these two average partial derivatives of pressure. Therefore, they are simultaneously computed exactly without any auxiliary relation, hence without any geometric solution projection or arbitrary scale factors. Several alternative formulations are then compared and key differences highlighted with emphasis on the determination of the pressure variation and average sound speed. The relevant underlying assumptions are identified, including some subtle approximations that are inherently employed in published average-state procedures. Finally, a representative test case is discussed for which an intrinsically exact average state is determined. This exact state is then compared with the predictions of recent methods, and their inherent approximations are appropriately quantified.

Gyrokinetic Magnetohydrodynamics and the Associated Equilibrium

NASA Astrophysics Data System (ADS)

Lee, W. W.; Hudson, S. R.; Ma, C. H.

2017-10-01

A proposed scheme for the calculations of gyrokinetic MHD and its associated equilibrium is discussed related a recent paper on the subject. The scheme is based on the time-dependent gyrokinetic vorticity equation and parallel Ohm's law, as well as the associated gyrokinetic Ampere's law. This set of equations, in terms of the electrostatic potential, ϕ, and the vector potential, ϕ , supports both spatially varying perpendicular and parallel pressure gradients and their associated currents. The MHD equilibrium can be reached when ϕ -> 0 and A becomes constant in time, which, in turn, gives ∇ . (J|| +J⊥) = 0 and the associated magnetic islands. Examples in simple cylindrical geometry will be given. The present work is partially supported by US DoE Grant DE-AC02-09CH11466.

Phase Equilibrium Investigation on 2-Phenylethanol in Binary and Ternary Systems: Influence of High Pressure on Density and Solid-Liquid Phase Equilibrium.

PubMed

Domańska, Urszula; Królikowski, Marek; Wlazło, Michał; Więckowski, Mikołaj

2018-05-30

Ionic liquids (ILs) are important new solvents proposed for applications in different separation processes. Herein, an idea of possible use of high pressure in a general strategy of production of 2-phenylethanol (PEA) is discussed. In this work, we present the influence of pressure on the density in binary systems of {1-hexyl-1-methylpyrrolidynium bis{(trifluoromethyl)sulfonyl}imide, [HMPYR][NTf 2 ], or 1-dodecyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [DoMIM][NTf 2 ] + PEA} in a wide range of temperatures (298.15-348.15 K) and pressures (0.1-40 MPa). The densities at ambient and high pressures are measured to present the physicochemical properties of the ILs used in the process of separation of PEA from aqueous phase. The Tait equation was used for the correlation of density of one-component and two-component systems as a function of mole fraction, temperature, and pressure. The influence of pressure is not significant. These systems exhibit mainly negative molar excess volumes, V E . The solid-liquid phase equilibrium (SLE) of [DoMIM][NTf 2 ] in PEA at atmospheric pressure was measured and compared to the SLE high-pressure results. Additionally, the ternary liquid-liquid phase equilibrium (LLE) at ambient pressure in the {[DoMIM][NTf 2 ] (1) + PEA (2) + water (3)} at temperature T = 308.15 K was investigated. The solubility of water in the [DoMIM][NTf 2 ] is quite high in comparison with that measured by us earlier for ILs ( x 3 = 0.403) at T = 308.15 K, which results in not very successful average selectivity of extraction of PEA from the aqueous phase. The [DoMIM][NTf 2 ] has shown strong interaction with PEA without the immiscibility region. The ternary system revealed Treybal's type phase equilibrium in which two partially miscible binaries ([DoMIM][NTf 2 ] + water) and (PEA + water) exist. From the results of LLE in the ternary system, the selectivity and the solute distribution ratio of separation of water/PEA were calculated and compared to the results obtained for the ILs measured earlier by us. The popular NRTL model was used to correlate the experimental tie-lines in ternary LLE. These results may help in a new technological project of "in situ" extraction of PEA from aqueous phase during the biosynthesis.

Hysteresis of the Contact Angle of a Meniscus Inside a Capillary with Smooth, Homogeneous Solid Walls.

PubMed

Kuchin, Igor V; Starov, Victor M

2016-05-31

A theory of contact angle hysteresis of a meniscus inside thin capillaries with smooth, homogeneous solid walls is developed in terms of surface forces (disjoining/conjoining pressure isotherm) using a quasi-equilibrium approach. The disjoining/conjoining pressure isotherm includes electrostatic, intermolecular, and structural components. The values of the static receding θr, advancing θa, and equilibrium θe contact angles in thin capillaries were calculated on the basis of the shape of the disjoining/conjoining pressure isotherm. It was shown that both advancing and receding contact angles depend on the capillary radius. The suggested mechanism of the contact angle hysteresis has a direct experimental confirmation: the process of receding is accompanied by the formation of thick β-films on the capillary walls. The effect of the transition from partial to complete wetting in thin capillaries is predicted and analyzed. This effect takes place in very thin capillaries, when the receding contact angle decreases to zero.

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

Hu, Shenyang; Setyawan, Wahyu; Joshi, Vineet V.

Xe gas bubble superlattice formation is observed in irradiated uranium–10 wt% molybdenum (U10Mo) fuels. However, the thermodynamic properties of the bubbles (the relationship among bubble size, equilibrium Xe concentration, and bubble pressure) and the mechanisms of bubble growth and superlattice formation are not well known. In this work, molecular dynamics is used to study these properties and mechanisms. The results provide important inputs for quantitative mesoscale models of gas bubble evolution and fuel performance. In the molecular dynamics simulations, the embedded-atom method (EAM) potential of U10Mo-Xe (Smirnova et al. 2013) is employed. Initial gas bubbles with low Xe concentration aremore » generated in a U10Mo single crystal. Then Xe atom atoms are continuously added into the bubbles, and the evolution of pressure and dislocation emission around the bubbles is analyzed. The relationship between pressure, equilibrium Xe concentration, and radius of the bubbles is established. It was found that the gas bubble growth is accompanied by partial dislocation emission, which results in a star-shaped dislocation structure and an anisotropic stress field. The emitted partial dislocations have a Burgers vector along the <111> direction and a slip plane of (11-2). Dislocation loop punch-out was not observed. A tensile stress was found along <110> directions around the bubble, favoring the nucleation and formation of a face-centered cubic bubble superlattice in body-centered cubic U10Mo fuels.« less

Role of partial miscibility on pressure buildup due to constant rate injection of CO2 into closed and open brine aquifers

NASA Astrophysics Data System (ADS)

Mathias, Simon A.; Gluyas, Jon G.; GonzáLez MartíNez de Miguel, Gerardo J.; Hosseini, Seyyed A.

2011-12-01

This work extends an existing analytical solution for pressure buildup because of CO2 injection in brine aquifers by incorporating effects associated with partial miscibility. These include evaporation of water into the CO2 rich phase and dissolution of CO2 into brine and salt precipitation. The resulting equations are closed-form, including the locations of the associated leading and trailing shock fronts. Derivation of the analytical solution involves making a number of simplifying assumptions including: vertical pressure equilibrium, negligible capillary pressure, and constant fluid properties. The analytical solution is compared to results from TOUGH2 and found to accurately approximate the extent of the dry-out zone around the well, the resulting permeability enhancement due to residual brine evaporation, the volumetric saturation of precipitated salt, and the vertically averaged pressure distribution in both space and time for the four scenarios studied. While brine evaporation is found to have a considerable effect on pressure, the effect of CO2 dissolution is found to be small. The resulting equations remain simple to evaluate in spreadsheet software and represent a significant improvement on current methods for estimating pressure-limited CO2 storage capacity.

Derivation of intermediate to silicic magma from the basalt analyzed at the Vega 2 landing site, Venus.

PubMed

Shellnutt, J Gregory

2018-01-01

Geochemical modeling using the basalt composition analyzed at the Vega 2 landing site indicates that intermediate to silicic liquids can be generated by fractional crystallization and equilibrium partial melting. Fractional crystallization modeling using variable pressures (0.01 GPa to 0.5 GPa) and relative oxidation states (FMQ 0 and FMQ -1) of either a wet (H2O = 0.5 wt%) or dry (H2O = 0 wt%) parental magma can yield silicic (SiO2 > 60 wt%) compositions that are similar to terrestrial ferroan rhyolite. Hydrous (H2O = 0.5 wt%) partial melting can yield intermediate (trachyandesite to andesite) to silicic (trachydacite) compositions at all pressures but requires relatively high temperatures (≥ 950°C) to generate the initial melt at intermediate to low pressure whereas at high pressure (0.5 GPa) the first melts will be generated at much lower temperatures (< 800°C). Anhydrous partial melt modeling yielded mafic (basaltic andesite) and alkaline compositions (trachybasalt) but the temperature required to produce the first liquid is very high (≥ 1130°C). Consequently, anhydrous partial melting is an unlikely process to generate derivative liquids. The modeling results indicate that, under certain conditions, the Vega 2 composition can generate silicic liquids that produce granitic and rhyolitic rocks. The implication is that silicic igneous rocks may form a small but important component of the northeast Aphrodite Terra.

Derivation of intermediate to silicic magma from the basalt analyzed at the Vega 2 landing site, Venus

PubMed Central

2018-01-01

Geochemical modeling using the basalt composition analyzed at the Vega 2 landing site indicates that intermediate to silicic liquids can be generated by fractional crystallization and equilibrium partial melting. Fractional crystallization modeling using variable pressures (0.01 GPa to 0.5 GPa) and relative oxidation states (FMQ 0 and FMQ -1) of either a wet (H2O = 0.5 wt%) or dry (H2O = 0 wt%) parental magma can yield silicic (SiO2 > 60 wt%) compositions that are similar to terrestrial ferroan rhyolite. Hydrous (H2O = 0.5 wt%) partial melting can yield intermediate (trachyandesite to andesite) to silicic (trachydacite) compositions at all pressures but requires relatively high temperatures (≥ 950°C) to generate the initial melt at intermediate to low pressure whereas at high pressure (0.5 GPa) the first melts will be generated at much lower temperatures (< 800°C). Anhydrous partial melt modeling yielded mafic (basaltic andesite) and alkaline compositions (trachybasalt) but the temperature required to produce the first liquid is very high (≥ 1130°C). Consequently, anhydrous partial melting is an unlikely process to generate derivative liquids. The modeling results indicate that, under certain conditions, the Vega 2 composition can generate silicic liquids that produce granitic and rhyolitic rocks. The implication is that silicic igneous rocks may form a small but important component of the northeast Aphrodite Terra. PMID:29584745

Oxygen potentials, oxygen diffusion coefficients and defect equilibria of nonstoichiometric (U,Pu)O2±x

NASA Astrophysics Data System (ADS)

Kato, Masato; Watanabe, Masashi; Matsumoto, Taku; Hirooka, Shun; Akashi, Masatoshi

2017-04-01

Oxygen potential of (U,Pu)O2±x was evaluated based on defect chemistry using an updated experimental data set. The relationship between oxygen partial pressure and deviation x in (U,Pu)O2±x was analyzed, and equilibrium constants of defect formation were determined as functions of Pu content and temperature. Brouwer's diagrams were constructed using the determined equilibrium constants, and a relational equation to determine O/M ratio was derived as functions of O/M ratio, Pu content and temperature. In addition, relationship between oxygen potential and oxygen diffusion coefficients were described.

Reproducing early Martian atmospheric carbon dioxide partial pressure by modeling the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops on Mars

NASA Astrophysics Data System (ADS)

Berk, Wolfgang; Fu, Yunjiao; Ilger, Jan-Michael

2012-10-01

The well defined composition of the Comanche rock's carbonate (Magnesite0.62Siderite0.25Calcite0.11Rhodochrosite0.02) and its host rock's composition, dominated by Mg-rich olivine, enable us to reproduce the atmospheric CO2partial pressure that may have triggered the formation of these carbonates. Hydrogeochemical one-dimensional transport modeling reveals that similar aqueous rock alteration conditions (including CO2partial pressure) may have led to the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops (Gusev Crater) and also in the ultramafic rocks exposed in the Nili Fossae region. Hydrogeochemical conditions enabling the formation of Mg-rich solid solution carbonate result from equilibrium species distributions involving (1) ultramafic rocks (ca. 32 wt% olivine; Fo0.72Fa0.28), (2) pure water, and (3) CO2partial pressures of ca. 0.5 to 2.0 bar at water-to-rock ratios of ca. 500 molH2O mol-1rock and ca. 5°C (278 K). Our modeled carbonate composition (Magnesite0.64Siderite0.28Calcite0.08) matches the measured composition of carbonates preserved in the Comanche rocks. Considerably different carbonate compositions are achieved at (1) higher temperature (85°C), (2) water-to-rock ratios considerably higher and lower than 500 mol mol-1 and (3) CO2partial pressures differing from 1.0 bar in the model set up. The Comanche rocks, hosting the carbonate, may have been subjected to long-lasting (>104 to 105 years) aqueous alteration processes triggered by atmospheric CO2partial pressures of ca. 1.0 bar at low temperature. Their outcrop may represent a fragment of the upper layers of an altered olivine-rich rock column, which is characterized by newly formed Mg-Fe-Ca solid solution carbonate, and phyllosilicate-rich alteration assemblages within deeper (unexposed) units.

Infinitely dilute partial molar properties of proteins from computer simulation.

PubMed

Ploetz, Elizabeth A; Smith, Paul E

2014-11-13

A detailed understanding of temperature and pressure effects on an infinitely dilute protein's conformational equilibrium requires knowledge of the corresponding infinitely dilute partial molar properties. Established molecular dynamics methodologies generally have not provided a way to calculate these properties without either a loss of thermodynamic rigor, the introduction of nonunique parameters, or a loss of information about which solute conformations specifically contributed to the output values. Here we implement a simple method that is thermodynamically rigorous and possesses none of the above disadvantages, and we report on the method's feasibility and computational demands. We calculate infinitely dilute partial molar properties for two proteins and attempt to distinguish the thermodynamic differences between a native and a denatured conformation of a designed miniprotein. We conclude that simple ensemble average properties can be calculated with very reasonable amounts of computational power. In contrast, properties corresponding to fluctuating quantities are computationally demanding to calculate precisely, although they can be obtained more easily by following the temperature and/or pressure dependence of the corresponding ensemble averages.

Humidity influence on gas-particle phase partitioning of α-pinene + O3 secondary organic aerosol

NASA Astrophysics Data System (ADS)

Prisle, N. L.; Engelhart, G. J.; Bilde, M.; Donahue, N. M.

2010-01-01

Water vapor uptake to particles could potentially affect organic-aerosol mass in three ways: first, water in the organic phase could reduce organic (equilibrium) partial pressures according to Raoult's law; second, an aqueous phase could attract water soluble organics according to Henry's law; finally, deliquescence of inorganic particle cores could mix the organic and inorganic particle phases, significantly diluting the organics and again reducing organic partial pressures according to Raoult's law. We present experiments using initially dry α-pinene + ozone secondary organic aerosol (SOA) on ammonium sulfate (AS) seeds at atmospheric concentrations in a smog chamber. After SOA formation, the chamber relative humidity is increased steadily by addition of steam to near 100%. Little subsequent SOA mass growth is observed, suggesting that none of these potential effects play a strong role in this system.

Formation and Dimerization of NO2 A General Chemistry Experiment

NASA Astrophysics Data System (ADS)

Hennis, April D.; Highberger, C. Scott; Schreiner, Serge

1997-11-01

We have developed a general chemistry experiment which illustrates Gay-Lussac's law of combining volumes. Students are able to determine the partial pressures and equilibrium constant for the formation and dimerization of NO2. The experiment can be carried out in about 45 minutes with students working in groups of two. The experiment readily provides students with data that can be manipulated with a common spreadsheet.

Low-pressure argon adsorption assessment of micropore connectivities in activated carbons.

PubMed

Zimny, T; Villieras, F; Finqueneisel, G; Cossarutto, L; Weber, J V

2006-01-01

Low-pressure argon adsorption has been used to study the energetic distribution of microporous activated carbons differing by their burn-off. The collected isotherms were analyzed using the derivative isotherm summation method. Some oscillations on the experimental curves for very low partial pressures were detected. The results are analyzed and discussed according to the literature and could be attributed to local overheating caused by spontaneous mass transfer of argon through constrictions between former pores and the new opening pore or deadend pores. We used the dynamic character of the experimental method and mainly the discrepancy of the quasi-equilibrium state to deduce key parameters related to the porosity topology.

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.

Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy

DOE PAGES

Newberg, John T.; Bluhm, Hendrik

2015-08-18

The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution. Isothermal uptake experiments were performed on vapor deposited ice at 227 K in the presence of the equilibrium water vapor pressure of 0.05 Torr and 2-propanol partial pressures ranging from 5 × 10 -5 to 2 × 10 -3 Torr. The C 1s APXPS spectra of adsorbed 2-propanol showed two characteristic peaks associated with the C OH alcohol group and C Me methyl groups in a 1 : 2 ratio, respectively. Coveragemore » increased with 2-propanol partial pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 10 3 Torr -1. The 1 : 2 ratio of C OH : C Me remained constant with increasing coverage, indicating there is no chemical reaction upon adsorption. The observed Langmuir kinetics using APXPS is consistent with previous observations of other small chain alcohols via indirect adsorption methods using, e.g., Knudsen cell and coated wall flow tube reactors.« less

Vapor pressure and vapor fractionation of silicate melts of tektite composition

USGS Publications Warehouse

Walter, Louis S.; Carron, M.K.

1964-01-01

The total vapor pressure of Philippine tektite melts of approximately 70 per cent silica has been determined at temperatures ranging from 1500 to 2100??C. This pressure is 190 ?? 40 mm Hg at 1500??C, 450 ?? 50 mm at 1800??C and 850 ?? 70 mm at 2100?? C. Determinations were made by visually observing the temperature at which bubbles began to form at a constant low ambient pressure. By varying the ambient pressure, a boiling point curve was constructed. This curve differs from the equilibrium vapor pressure curve due to surface tension effects. This difference was evaluated by determining the equilibrium bubble size in the melt and calculating the pressure due to surface tension, assuming the latter to be 380 dyn/cm. The relative volatility from tektite melts of the oxides of Na, K, Fe, Al and Si has been determined as a function of temperature, total pressure arid roughly, of oxygen fugacity. The volatility of SiO2 is decreased and that of Na2O and K2O is increased in an oxygen-poor environment. Preliminary results indicate that volatilization at 2100??C under atmospheric pressure caused little or no change in the percentage Na2O and K2O. The ratio Fe3 Fe2 of the tektite is increased in ambient air at a pressure of 9 ?? 10-4 mm Hg (= 106.5 atm O2, partial pressure) at 2000??C. This suggests that tektites were formed either at lower oxygen pressures or that they are a product of incomplete oxidation of parent material with a still lower ferricferrous ratio. ?? 1964.

Gas-phase measurements of combustion interaction with materials for radiation-cooled chambers

NASA Technical Reports Server (NTRS)

Barlow, R. S.; Lucht, R. P.; Jassowski, D. M.; Rosenberg, S. D.

1991-01-01

Foil samples of Ir and Pt are exposed to combustion products in a controlled premixed environment at atmospheric pressure. Electrical heating of the foil samples is used to control the surface temperature and to elevate it above the radiative equilibrium temperature within the test apparatus. Profiles of temperature and OH concentration in the boundary layer adjacent to the specimen surface are measured by laser-induced fluorescence. Measured OH concentrations are significantly higher than equilibrium concentrations calculated for the known mixture ratio and the measured temperature profiles. This result indicates that superequilibrium concentrations of H-atoms and O-atoms are also present in the boundary layer, due to partial equilibrium of the rapid binary reactions of the H2/O2 chemical kinetic system. These experiments are conducted as part of a research program to investigate fundamental aspects of the interaction of combustion gases with advanced high-temperature materials for radiation-cooled thrusters.

Conformational plasticity of DM43, a metalloproteinase inhibitor from Didelphis marsupialis: chemical and pressure-induced equilibrium (un)folding studies.

PubMed

Chapeaurouge, Alex; Martins, Samantha M; Holub, Oliver; Rocha, Surza L G; Valente, Richard H; Neves-Ferreira, Ana G C; Ferreira, Sérgio T; Domont, Gilberto B; Perales, Jonas

2009-10-01

We have investigated the folding of DM43, a homodimeric metalloproteinase inhibitor isolated from the serum of the South American opossum Didelphis marsupialis. Denaturation of the protein induced by GdnHCl (guanidine hydrochloride) was monitored by extrinsic and intrinsic fluorescence spectroscopy. While the equilibrium (un)folding of DM43 followed by tryptophan fluorescence was well described by a cooperative two-state transition, bis-ANS (4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid) fluorescence measurements revealed an intensity maximum at the midpoint of the unfolding transition (2 M GdnHCl), indicating a partially folded intermediate state. We further investigated the DM43 intermediate stabilized at 2 M GdnHCl using size exclusion chromatography. This analysis revealed that the folding intermediate can be best described as partially folded DM43 monomers. Thermodynamic analysis of the GdnHCl-induced denaturation of DM43 revealed Gibbs free-energy changes of 13.57 kcal/mol for dimer dissociation and 1.86 kcal/mol for monomer unfolding, pointing to a critical role of dimerization as a determinant of the structure and stability of this protein. In addition, by using hydrostatic pressure (up to 3.5 kbar) we were able to stabilize partially folded states different from those stabilized in the presence of GdnHCl. Taken together, these results indicate that the conformational plasticity of DM43 could provide this protein with the ability to adapt its conformation to a variety of different environments and biological partners during its biological lifetime.

Stability analysis of coupled torsional vibration and pressure in oilwell drillstring system

NASA Astrophysics Data System (ADS)

Toumi, S.; Beji, L.; Mlayeh, R.; Abichou, A.

2018-01-01

To address security issues in oilwell drillstring system, the drilling operation handling which is in generally not autonomous but ensured by an operator may be drill bit destructive or fatal for the machine. To control of stick-slip phenomenon, the drillstring control at the right speed taking only the drillstring vibration is not sufficient as the mud dynamics and the pressure change around the drill pipes cannot be neglected. A coupled torsional vibration and pressure model is presented, and the well-posedness problem is addressed. As a Partial Differential Equation-Ordinary Differential Equation (PDE-ODE) coupled system, and in order to maintain a non destructive downhole pressure, we investigate the control stability with and without the damping term in the wave PDE. In terms of, the torsional variable, the downhole pressure, and the annulus pressure, the coupled system equilibrium is shown to be exponentially stable.

FirefOx Design Reference fO2 Sensor for Hot, Deep Atmospheres

NASA Astrophysics Data System (ADS)

Izenberg, N.; Papadakis, S.; Deglau, D.; Francomacaro, A. S.

2016-12-01

Understanding the composition of the lowest portion of Venus' atmosphere is critical to knowing the stable mineralogy of the rocks there. Oxygen gas is a critical trace component, with fugacity, or partial pressure, estimated in the range of 10-19 to 10-22 from early probe measurements down to 22km altitude (Pioneer Venus, Venera), chemical equilibrium measurements, and other modeling. "FirefOx" is a simple oxygen fugacity sensor with the express purpose of determining the partial pressure of oxygen in the lowest scale heights of the Venus atmosphere, and especially the lowest hundreds of meters; the surface atmosphere interface, where the atmosphere and surface move to thermodynamic equilibrium. Knowledge of the fO2 at the surface atmosphere interface is crucial to determining the stable mineralogy of surface materials (e.g. magnetite vs. hematite) and gas chemistry in the near-surface atmosphere FirefOx is a Metal/Metal Oxide oxygen fugacity sensor intended to be mounted on the outside of a Venus descent probe, with electronics housed inside a thermally controlled environment. The sole sensor capability is the precise, accurate detection of the partial pressure of oxygen gas (fO2) in the near-surface environment of Venus, at up to 95-bar pressure (predominantly CO2. Surface temperatures at mean planetary elevation are near 735 K, thus a required operational temperature range of 710-740 K covers a range of near-surface elevations. FirefOx system requirements are low ( 100-200 grams, mass, milliwatt power, several kilobytes total science data). A design reference sensor, composed of custom, Yittria-ZrO ceramic electrolyte, with an encapsulated Pd/PdO standard and patterned Pt electrodes has demonstrated scientifically useful signal-to-noise millivolt level potential at temperatures as low as 620 K, relatable to fO2 by a Nernst equation E = RT/4F ln(PO2/PrefO2) where E = open circuit potential across the sensor electrolyte, R = universal gas constant, T = temperature, F = Faraday constant, PrefO2 = reference oxygen pressure, and PO2 = unknown oxygen pressure of the outside environment. The FirefOx sensor shows promise for direct fO2 measurement on potential upcoming Venus in situ and other deep atmosphere probes.

Experimental study of catalytic hydrogenation by using an in-situ hydrogen measuring technique. Final report

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

Chiang, S.H.; Klinzing, G.E.; Cheng, Y.S.

1984-12-01

An in-situ technique for measuring hydrogen concentration (partial pressure) had been previously used to measure static properties (hydrogen solubilities, vapor pressures of hydrocarbons, etc.). Because of its good precision (2% relative error) and relatively short respond time (9.7 to 2.0 seconds at 589 to 728K), the technique was successfully applied to a dynamic study of hydrogenation reactions in this work. Furthermore, the technique is to be tested for industrial uses. Hydrogen/1-methylnaphthalene system was experimentally investigated in a one-liter autoclave equipped with a magnetically driven stirrer and temperature controlling devices. Catalytic hydrogenation of 1-methylnaphthalene was studied in the presence of sulfidedmore » Co-Mo-Al2O3 catalyst. In addition, the vapor/liquid equilibrium relationship was determined by using this technique. Hydrogenation reaction runs were performed at temperatures of 644.1, 658.0 and 672.0K and pressures up to 9.0 MPa. The ring hydrogenation, resulting in 1- and 5-methyltetralin, was found to be the dominant reaction. This is in agreement with cited literature. Effects of hydrogen partial pressure, operating temperature, as well as presulfided catalyst are also investigated and discussed in this work. The vapor pressure of 1-methylnaphthalene was measured over a temperature range of 555.2 to 672.0K. The results are in good agreement with literature data. Measurements for hydrogen solubility in 1-methylnaphthalene were conducted over temperature and pressure range of 598 to 670K and 5.2 to 8.8 MPa, respectively. Similar to previously reported results, the hydrogen solubility increases with increasing temperature when total pressure is held constant. A linear relation is found between the hydrogen solubility and hydrogen partial pressure. 21 refs., 13 figs., 10 tabs.« less

Infinitely Dilute Partial Molar Properties of Proteins from Computer Simulation

PubMed Central

2015-01-01

A detailed understanding of temperature and pressure effects on an infinitely dilute protein’s conformational equilibrium requires knowledge of the corresponding infinitely dilute partial molar properties. Established molecular dynamics methodologies generally have not provided a way to calculate these properties without either a loss of thermodynamic rigor, the introduction of nonunique parameters, or a loss of information about which solute conformations specifically contributed to the output values. Here we implement a simple method that is thermodynamically rigorous and possesses none of the above disadvantages, and we report on the method’s feasibility and computational demands. We calculate infinitely dilute partial molar properties for two proteins and attempt to distinguish the thermodynamic differences between a native and a denatured conformation of a designed miniprotein. We conclude that simple ensemble average properties can be calculated with very reasonable amounts of computational power. In contrast, properties corresponding to fluctuating quantities are computationally demanding to calculate precisely, although they can be obtained more easily by following the temperature and/or pressure dependence of the corresponding ensemble averages. PMID:25325571

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

PubMed Central

Axson, Jessica L.; Takahashi, Kaito; De Haan, David O.; Vaida, Veronica

2010-01-01

In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process not previously considered to occur in water-restricted environments. In this study, we spectroscopically identified methylglyoxal diol (MGD) and obtained the gas-phase partial pressures of MG and MGD. These results, in conjunction with the relative humidity, were used to obtain the equilibrium constant, KP, for the water-mediated hydration of MG in the gas phase. The Gibbs free energy for this process, ΔG°, obtained as a result, suggests a larger than expected gas-phase diol concentration. This may have significant implications for understanding the role of organics in atmospheric chemistry. PMID:20142510

Ureilite petrogenesis: A limited role for smelting during anatexis and catastrophic disruption

NASA Astrophysics Data System (ADS)

Warren, Paul H.; Huber, Heinz

2006-06-01

A popular model for ureilites assumes that during anatexis in an asteroidal mantle, pressure-buffered equilibrium smelting (partial reduction coincident with partial melting) engendered their conspicuous mafic-silicate-core mg diversity (75-96 mol%). Several mass-balance problems arise from this hypothesis. Smelting inevitably consumes a large proportion of any plausible initial carbon while generating significant proportions of Fe metal and copious proportions of CO gas. The most serious problem concerns the yield of CO gas. If equilibrium smelting produced the ureilites' entire 21 mol% range in olivine-core mg, the proportion of gas within the asteroidal mantle (assuming plausibly low pressure <˜80 bar) should have reached ≥85 vol%. Based on the remarkably stepwise cooling history inferred from ureilite texture and mineralogy, a runaway, CO-leaky process that can loosely be termed smelting appears to have occurred, probably triggered by a major impact. The runaway scenario appears likely because, by Le Châtelier's principle, CO leakage would tend to accelerate the smelting process. Also, the copious volumes of gas produced by smelting would have led to explosive, mass-leaky eruptions into the vacuum surrounding the asteroid. Loss of mass would mean diminution of interior pressure, which would induce further smelting, leading to further loss of mass (basalt), and so on. Such a disruptive runaway process may have engendered the ureilites' distinctive reduced olivine rims. But the only smelting, according to this scenario, was a short-lived disequilibrium process that reduced only the olivine rims, not the cores; and the ureilites were cooling, not melting, during the abortive "smelting" episode.

Sensor for measuring hydrogen partial pressure in parabolic trough power plant expansion tanks

NASA Astrophysics Data System (ADS)

Glatzmaier, Greg C.; Cooney, Daniel A.

2017-06-01

The National Renewable Energy Laboratory and Acciona Energy North America are working together to design and implement a process system that provides a permanent solution to the issue of hydrogen buildup at parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks that serve as reservoirs for the heat transfer fluid (HTF) that circulates in the collector field and power block components. Our modeling shows that removing hydrogen from the expansion tanks at a design rate reduces and maintains dissolved hydrogen in the circulating HTF to a selected target level. Our collaborative work consists of several tasks that are needed to advance this process concept to a development stage, where it is ready for implementation at a commercial power plant. Our main effort is to design and evaluate likely process-unit operations that remove hydrogen from the expansion tanks at a specified rate. Additionally, we designed and demonstrated a method and instrumentation to measure hydrogen partial pressure and concentration in the expansion-tank headspace gas. We measured hydrogen partial pressure in the headspace gas mixture using a palladium-alloy membrane, which is permeable exclusively to hydrogen. The membrane establishes a pure hydrogen gas phase that is in equilibrium with the hydrogen in the gas mixture. We designed and fabricated instrumentation, and demonstrated its effectiveness in measuring hydrogen partial pressures over a range of three orders of magnitude. Our goal is to install this instrument at the Nevada Solar One power plant and to demonstrate its effectiveness in measuring hydrogen levels in the expansion tanks under normal plant operating conditions.

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.

Thermodynamics Behavior of Germanium During Equilibrium Reactions between FeOx-CaO-SiO2-MgO Slag and Molten Copper

NASA Astrophysics Data System (ADS)

Shuva, M. A. H.; Rhamdhani, M. A.; Brooks, G. A.; Masood, S.; Reuter, M. A.

2016-10-01

The distribution ratio of germanium (Ge), L_{{Ge}}^{s/m} during equilibrium reactions between magnesia-saturated FeOx-CaO-SiO2 (FCS) slag and molten copper has been measured under oxygen partial pressures from 10-10 to 10-7 atm and at temperatures 1473 to 1623 K (1200 to 1350 °C). It was observed that the Ge distribution ratio increases with increasing oxygen partial pressure, and with decreasing temperature. It was also observed that the distribution ratio is strongly dependent on slag basicity. The distribution ratio was observed to increase with increasing optical basicity. At fixed CaO concentration in the slag, the distribution ratio was found to increase with increasing Fe/SiO2 ratio, tending to a plateau at L_{{Ge}}^{s/m} = 0.8. This behavior is consistent with the assessment of ionic bond fraction carried out in this study, and suggested the acidic nature of germanium oxide (GeO2) in the slag system studied. The characterisation results of the quenched slag suggested that Ge is present in the FeOx-CaO-SiO2-MgO slag predominantly as GeO2. At 1573 K (1300 °C) and p_{{{{O}}2 }} = 10-8 atm, the activity coefficient of GeO2 in the slag was calculated to be in the range of 0.24 to 1.50. The results from the current study suggested that less-basic slag, high operating temperature, and low oxygen partial pressure promote a low Ge distribution ratio. These conditions are desired for maximizing Ge recovery, for example, during pyrometallurgical processing of Ge-containing e-waste through secondary copper smelting. Overall, the thermodynamics data generated from this study can be used for process modeling purposes for improving recovery of Ge in primary and secondary copper smelting processes.

Removal of Oxygen from Electronic Materials by Vapor-Phase Processes

NASA Technical Reports Server (NTRS)

Palosz, Witold

1997-01-01

Thermochemical analyses of equilibrium partial pressures over oxides with and without the presence of the respective element condensed phase, and hydrogen, chalcogens, hydrogen chalcogenides, and graphite are presented. Theoretical calculations are supplemented with experimental results on the rate of decomposition and/or sublimation/vaporization of the oxides under dynamic vacuum, and on the rate of reaction with hydrogen, graphite, and chalcogens. Procedures of removal of a number of oxides under different conditions are discussed.

Hydraulic effects in a radiative atmosphere with ionization

NASA Astrophysics Data System (ADS)

Bhat, P.; Brandenburg, A.

2016-03-01

Context. In his 1978 paper, Eugene Parker postulated the need for hydraulic downward motion to explain magnetic flux concentrations at the solar surface. A similar process has also recently been seen in simplified (e.g., isothermal) models of flux concentrations from the negative effective magnetic pressure instability (NEMPI). Aims: We study the effects of partial ionization near the radiative surface on the formation of these magnetic flux concentrations. Methods: We first obtain one-dimensional (1D) equilibrium solutions using either a Kramers-like opacity or the H- opacity. The resulting atmospheres are then used as initial conditions in two-dimensional (2D) models where flows are driven by an imposed gradient force that resembles a localized negative pressure in the form of a blob. To isolate the effects of partial ionization and radiation, we ignore turbulence and convection. Results: Because of partial ionization, an unstable stratification always forms near the surface. We show that the extrema in the specific entropy profiles correspond to the extrema in the degree of ionization. In the 2D models without partial ionization, strong flux concentrations form just above the height where the blob is placed. Interestingly, in models with partial ionization, such flux concentrations always form at the surface well above the blob. This is due to the corresponding negative gradient in specific entropy. Owing to the absence of turbulence, the downflows reach transonic speeds. Conclusions: We demonstrate that, together with density stratification, the imposed source of negative pressure drives the formation of flux concentrations. We find that the inclusion of partial ionization affects the entropy profile dramatically, causing strong flux concentrations to form closer to the surface. We speculate that turbulence effects are needed to limit the strength of flux concentrations and homogenize the specific entropy to a stratification that is close to marginal.

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

NASA Astrophysics Data System (ADS)

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter; Danilewsky, Andreas; Langenhorst, Falko; Ehm, Lars; Trullenque, Ghislain; Kenkmann, Thomas

2017-07-01

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. Here, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions of α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s-1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO6 octahedra rather than the rearrangement of the SiO4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.

Enhanced densification under shock compression in porous silicon

NASA Astrophysics Data System (ADS)

Lane, J. Matthew D.; Thompson, Aidan P.; Vogler, Tracy J.

2014-10-01

Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. We demonstrate a molecular mechanism that drives this behavior. We also present evidence from atomistic simulation that silicon belongs to this anomalous class of materials. Atomistic simulations indicate that local shear strain in the neighborhood of collapsing pores nucleates a local solid-solid phase transformation even when bulk pressures are below the thermodynamic phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.

Heat Treatments of ZnSe Starting Materials for Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Palosz, W.; Feth, S.; Lehoczky, S. L.

1998-01-01

The effect of different heat treatments on stoichiometry and residual gas pressure in ZnSe physical vapor transport system was investigated. The dependence of the amount and composition of the residual gas on various heat treatment procedures is reported. Heat treatment of ZnSe starting materials by baking under the condition of dynamic vacuum to adjust its stoichiometry was performed and the effectiveness of the treatment was confirmed by the measurements of the partial pressure of Se2, P(sub Se2), in equilibrium with the heat treated samples. Optimum heat treatment procedures on the ZnSe starting material for the physical vapor transport process are discussed and verified experimentally.

Heat Treatments of ZnSe Starting Materials for Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Palosz, W.; Feth, S.; Lehoczky, S. L.

1997-01-01

The effect of different heat treatments on stoichiometry and residual gas pressure in ZnSe physical vapor transport system was investigated. The dependence of the amount and composition of the residual gas on various heat treatment procedures is reported. Heat treatment of ZnSe starting materials by baking under the condition of dynamic vacuum to adjust its stoichiometry was performed and the effectiveness of the treatment was confirmed by the measurements of the partial pressure of Se2, P(sub Se2), in equilibrium with the heat treated samples. Optimum heat treatment procedures on the ZnSe starting material for the physical vapor transport process are discussed and verified experimentally.

Steady hydromagnetic flows in open magnetic fields. II - Global flows with static zones

NASA Technical Reports Server (NTRS)

Tsinganos, K.; Low, B. C.

1989-01-01

A theoretical study of an axisymmetric steady stellar wind with a static zone is presented, with emphasis on the situation where the global magnetic field is symmetrical about the stellar equator and is partially open. In this scenario, the wind escapes in open magnetic fluxes originating from a region at the star pole and a region at an equatorial belt of closed magnetic field in static equilibrium. The two-dimensional balance of the pressure gradient and the inertial, gravitational, and Lorentz forces in different parts of the flow are studied, along with the static interplay between external sources of energy (heating and/or cooling) distributed in the flow and the pressure distribution.

Sensor for Measuring Hydrogen Partial Pressure in Parabolic Trough Power Plant Expansion Tanks

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

Glatzmaier, Greg C.; Cooney, Daniel A.

The National Renewable Energy Laboratory and Acciona Energy North America are working together to design and implement a process system that provides a permanent solution to the issue of hydrogen buildup at parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks that serve as reservoirs for the heat transfer fluid (HTF) that circulates in the collector field and power block components. Our modeling shows that removing hydrogen from the expansion tanks at a design rate reduces and maintains dissolved hydrogen in the circulating HTF to a selected target level. Our collaborative workmore » consists of several tasks that are needed to advance this process concept to a development stage, where it is ready for implementation at a commercial power plant. Our main effort is to design and evaluate likely process-unit operations that remove hydrogen from the expansion tanks at a specified rate. Additionally, we designed and demonstrated a method and instrumentation to measure hydrogen partial pressure and concentration in the expansion-tank headspace gas. We measured hydrogen partial pressure in the headspace gas mixture using a palladium-alloy membrane, which is permeable exclusively to hydrogen. The membrane establishes a pure hydrogen gas phase that is in equilibrium with the hydrogen in the gas mixture. We designed and fabricated instrumentation, and demonstrated its effectiveness in measuring hydrogen partial pressures over a range of three orders of magnitude. Our goal is to install this instrument at the Nevada Solar One power plant and to demonstrate its effectiveness in measuring hydrogen levels in the expansion tanks under normal plant operating conditions.« less

Carbon dioxide supersaturation in the surface waters of lakes

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

Cole, J.J.; Caraco, N.F.; Kling, G.W.

1994-09-09

Data on the partial pressure of carbon dioxide (CO{sub 2}) in the surface waters from a large number of lakes (1835) with a worldwide distribution show that only a small proportion of the 4665 samples analyzed (less than 10 percent) were within {+-}20 percent of equilibrium with the atmosphere and that most samples (87 percent) were supersaturated. The mean partial pressure of CO{sub 2} averaged 1036 microatmospheres, about three times the value in the overlying atmosphere, indicating that lakes are sources rather than sinks of atmospheric CO{sub 2}. On a global scale, the potential efflux of CO{sub 2} from lakesmore » (about 0.14 x 10{sup 15} grams of carbon per year) is about half as large as riverine transport of organic plus inorganic carbon to the ocean. Lakes are a small but potentially important conduit for carbon for terrestrial sources to the atmospheric sink. 18 refs., 2 figs., 1 tab.« less

Post-combustion CO2 capture with activated carbons using fixed bed adsorption

NASA Astrophysics Data System (ADS)

Al Mesfer, Mohammed K.; Danish, Mohd; Fahmy, Yasser M.; Rashid, Md. Mamoon

2018-03-01

In the current work, the capturing of carbon dioxide from flue gases of post combustion emission using fixed bed adsorption has been carried out. Two grades of commercial activated carbon (sorbent-1 and sorbent-2) were used as adsorbent. Feed consisting of CO2 and N2 mixture was used for carrying out the adsorption. The influence of bed temperature, feed rate, equilibrium partial pressure and initial % CO2 in feed were considered for analyzing adsorption-desorption process. It was found that the total adsorption-desorption cycle time decreases with increased column temperature and feed rates. The time required to achieve the condition of bed saturation decreases with increased bed temperature and feed rates. The amount of CO2 adsorbed/Kg of the adsorbent declines with increased bed temperature with in studied range for sorbent-1 and sorbent-2. It was suggested that the adsorption capacity of the both the sorbents increases with increased partial pressure of the gas.

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

Karwacki, C.J.; Buchanan, J.H.; Mahle, J.J.

Experimental data are reported for the desorption of bis-2-chloroethyl sulfide, (a sulfur mustard or HD) and its decomposition products from activated coconut shell carbon (CSC). The results show that under equilibrium conditions changes in the HD partial pressure are affected primarily by its loading and temperature of the adsorbent. The partial pressure of adsorbed HD is found to increase by about a decade for each 25 C increase in temperature for CSC containing 0.01--0.1 g/g HD. Adsorption equilibria of HD appear to be little affected by coadsorbed water. Although complicated by its decomposition, the distribution of adsorbed HD (of knownmore » amount) appears to occupy pores of similar energy whether dry or in the presence of adsorbed water. On dry CSC adsorbed HD appears stable, while in the presence of water its decomposition is marked by hydrolysis at low temperature and thermal decomposition at elevated temperatures. The principal volatile products desorbed are 1,4-thioxane, 2-chloroethyl vinyl sulfide and 1,4-dithiane, with the latter favoring elevated temperatures.« less

Solid state solubility of copper oxides in hydroxyapatite

NASA Astrophysics Data System (ADS)

Zykin, Mikhail A.; Vasiliev, Alexander V.; Trusov, Lev A.; Dinnebier, Robert E.; Jansen, Martin; Kazin, Pavel E.

2018-06-01

Samples containing copper oxide doped hydroxyapatite with the composition Ca10(PO4)6(CuxOH1-x-δ)2, x = 0.054 - 0.582, in the mixture with CuO/Cu2O were prepared by a solid-state high-temperature treatment at varying annealing temperatures and at different partial water vapor and oxygen pressures. The crystal structures of the apatite compounds were refined using powder X-ray diffraction patterns and the content of copper ions x in the apatite was determined. Copper ions enter exclusively into the apatite trigonal channels formally substituting protons of OH-groups and the hexagonal cell parameters grow approximately linearly with x, the channel volume mostly expanding while the remaining volume of the crystal lattice changing only slightly. The equilibrium copper content in the apatite increases drastically, by almost a factor of 10 with the annealing temperature rising from 800° to 1200°C. The reduction of the water partial pressure leads to a further increase of x, while the dependence of x on the oxygen partial pressure exhibits a maximum. The observed relations are consistent with the proposed chemical reactions implying the copper introduction is followed by the release of a considerable quantity of gaseous products - water and oxygen. The analysis of interatomic distances suggests that the maximum content of copper ions in the channel cannot exceed 2/3.

Determining the Partial Pressure of Volatile Components via Substrate-Integrated Hollow Waveguide Infrared Spectroscopy with Integrated Microfluidics.

PubMed

Kokoric, Vjekoslav; Theisen, Johannes; Wilk, Andreas; Penisson, Christophe; Bernard, Gabriel; Mizaikoff, Boris; Gabriel, Jean-Christophe P

2018-04-03

A microfluidic system combined with substrate-integrated hollow waveguide (iHWG) vapor phase infrared spectroscopy has been developed for evaluating the chemical activity of volatile compounds dissolved in complex fluids. Chemical activity is an important yet rarely exploited parameter in process analysis and control. Access to chemical activity parameters enables systematic studies on phase diagrams of complex fluids, the detection of aggregation processes, etc. The instrumental approach developed herein uniquely enables controlled evaporation/permeation from a sample solution into a hollow waveguide structure and the analysis of the partial pressures of volatile constituents. For the example of a binary system, it was shown that the chemical activity may be deduced from partial pressure measurements at thermodynamic equilibrium conditions. The combined microfluidic-iHWG midinfrared sensor system (μFLUID-IR) allows the realization of such studies in the absence of any perturbations provoked by sampling operations, which is unavoidable using state-of-the-art analytical techniques such as headspace gas chromatography. For demonstration purposes, a water/ethanol mixture was investigated, and the derived data was cross-validated with established literature values at different mixture ratios. Next to perturbation-free measurements, a response time of the sensor <150 s ( t 90 ) at a recovery time <300 s ( t recovery ) has been achieved, which substantiates the utility of μFLUID-IR for future process analysis-and-control applications.

Desulfurization kinetics of molten copper by gas bubbling

NASA Astrophysics Data System (ADS)

Fukunaka, Y.; Nishikawa, K.; Sohn, H. S.; Asaki, Z.

1991-02-01

Molten copper with 0.74 wt pct sulfur content was desulfurized at 1523 K by bubbling Ar-O2 gas through a submerged nozzle. The reaction rate was significantly influenced not only by the oxygen partial pressure but also by the gas flow rate. Little evolution of SO2 gas was observed in the initial 10 seconds of the oxidation; however, this was followed by a period of high evolution rate of SO2 gas. The partial pressure of SO2 gas decreased with further progress of the desulfurization. The effect of the immersion depth of the submerged nozzle was negligible. The overall reaction is decomposed to two elementary reactions: the desulfurization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of sulfur and oxygen contents in the melt and the SO2 partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model combined with the reported thermodynamic data of these reactions. Based on the present model, it was anticipated that the oxidation rate around a single gas bubble was mainly determined by the rate of gas-phase mass transfer, but all oxygen gas blown into the melt was virtually consumed to the desulfurization and dissolution reactions before it escaped from the melt surface.

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

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

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. In this paper, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions ofmore » α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s -1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO 6 octahedra rather than the rearrangement of the SiO 4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.« less

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

DOE PAGES

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter; ...

2017-03-27

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. In this paper, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions ofmore » α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s -1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO 6 octahedra rather than the rearrangement of the SiO 4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.« less

Analysis of three-phase equilibrium conditions for methane hydrate by isometric-isothermal molecular dynamics simulations.

PubMed

Yuhara, Daisuke; Brumby, Paul E; Wu, David T; Sum, Amadeu K; Yasuoka, Kenji

2018-05-14

To develop prediction methods of three-phase equilibrium (coexistence) conditions of methane hydrate by molecular simulations, we examined the use of NVT (isometric-isothermal) molecular dynamics (MD) simulations. NVT MD simulations of coexisting solid hydrate, liquid water, and vapor methane phases were performed at four different temperatures, namely, 285, 290, 295, and 300 K. NVT simulations do not require complex pressure control schemes in multi-phase systems, and the growth or dissociation of the hydrate phase can lead to significant pressure changes in the approach toward equilibrium conditions. We found that the calculated equilibrium pressures tended to be higher than those reported by previous NPT (isobaric-isothermal) simulation studies using the same water model. The deviations of equilibrium conditions from previous simulation studies are mainly attributable to the employed calculation methods of pressure and Lennard-Jones interactions. We monitored the pressure in the methane phase, far from the interfaces with other phases, and confirmed that it was higher than the total pressure of the system calculated by previous studies. This fact clearly highlights the difficulties associated with the pressure calculation and control for multi-phase systems. The treatment of Lennard-Jones interactions without tail corrections in MD simulations also contributes to the overestimation of equilibrium pressure. Although improvements are still required to obtain accurate equilibrium conditions, NVT MD simulations exhibit potential for the prediction of equilibrium conditions of multi-phase systems.

Analysis of three-phase equilibrium conditions for methane hydrate by isometric-isothermal molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Yuhara, Daisuke; Brumby, Paul E.; Wu, David T.; Sum, Amadeu K.; Yasuoka, Kenji

2018-05-01

To develop prediction methods of three-phase equilibrium (coexistence) conditions of methane hydrate by molecular simulations, we examined the use of NVT (isometric-isothermal) molecular dynamics (MD) simulations. NVT MD simulations of coexisting solid hydrate, liquid water, and vapor methane phases were performed at four different temperatures, namely, 285, 290, 295, and 300 K. NVT simulations do not require complex pressure control schemes in multi-phase systems, and the growth or dissociation of the hydrate phase can lead to significant pressure changes in the approach toward equilibrium conditions. We found that the calculated equilibrium pressures tended to be higher than those reported by previous NPT (isobaric-isothermal) simulation studies using the same water model. The deviations of equilibrium conditions from previous simulation studies are mainly attributable to the employed calculation methods of pressure and Lennard-Jones interactions. We monitored the pressure in the methane phase, far from the interfaces with other phases, and confirmed that it was higher than the total pressure of the system calculated by previous studies. This fact clearly highlights the difficulties associated with the pressure calculation and control for multi-phase systems. The treatment of Lennard-Jones interactions without tail corrections in MD simulations also contributes to the overestimation of equilibrium pressure. Although improvements are still required to obtain accurate equilibrium conditions, NVT MD simulations exhibit potential for the prediction of equilibrium conditions of multi-phase systems.

Bubble formation in water with addition of a hydrophobic solute.

PubMed

Okamoto, Ryuichi; Onuki, Akira

2015-07-01

We show that phase separation can occur in a one-component liquid outside its coexistence curve (CX) with addition of a small amount of a solute. The solute concentration at the transition decreases with increasing the difference of the solvation chemical potential between liquid and gas. As a typical bubble-forming solute, we consider O2 in ambient liquid water, which exhibits mild hydrophobicity and its critical temperature is lower than that of water. Such a solute can be expelled from the liquid to form gaseous domains while the surrounding liquid pressure is higher than the saturated vapor pressure p cx. This solute-induced bubble formation is a first-order transition in bulk and on a partially dried wall, while a gas film grows continuously on a completely dried wall. We set up a bubble free energy ΔG for bulk and surface bubbles with a small volume fraction ϕ. It becomes a function of the bubble radius R under the Laplace pressure balance. Then, for sufficiently large solute densities above a threshold, ΔG exhibits a local maximum at a critical radius and a minimum at an equilibrium radius. We also examine solute-induced nucleation taking place outside CX, where bubbles larger than the critical radius grow until attainment of equilibrium.

Partial Model of Insulator/Insulator Contact Charging

NASA Technical Reports Server (NTRS)

Hogue, Michael; Calle, C. I.; Buhler, C. R.; Mucciolo, E. R.

2005-01-01

Two papers present a two-phase equilibrium model that partly explains insulator/ insulator contact charging. In this model, a vapor of ions within a gas is in equilibrium with a submonolayer of ions of the same species that have been adsorbed on the surface of an insulator. The surface is modeled as having localized states, each with a certain energy of adsorption for an ion. In an earlier version of the model described in the first paper, the ions do not interact with each other. Using the grand canonical ensemble, the chemical potentials of both vapor and absorbed phases are derived and equated to determine the vapor pressure. If a charge is assigned to the vapor particles (in particular, if single ionization is assumed), then the surface charge density associated with adsorbed ions can be calculated as a function of pressure. In a later version of the model presented in the second paper, the submodel of the vapor phase is extended to include electrostatic interactions between vapor ions and adsorbed ones as well as the screening effect, at a given distance from the surface, of ions closer to the surface. Theoretical values of this model closely match preliminary experimental data on the discharge of insulators as a function of pressure.

Ternary liquid-liquid equilibrium for eugenol + tert-butanol + water system at 303.15 and 323.15K and atmospheric pressure

NASA Astrophysics Data System (ADS)

Sucipto, Retno Kumala Hesti; Kuswandi, Wibawa, Gede

2017-05-01

The objective of this study was to determine ternary liquid-liquid equilibrium for eugenol + tert-butanol + water system at 303.15 and 323.15K and atmospheric pressure. Using 25 mL equilibrium cell equipped jacketted water connected to water bath to maintain equilibrium temperature constant. The procedure of this experiment was conducted by inserting mixture of eugenol + tert-butanol + water system at certain composition into equilibrium cell. The solution was stirred for 4 hours and then was allowed for 20 hours in order to separate aqueous and organic phases completely. The temperature equilibrium cell of and the atmosphere pressure were recorded as equilibrium temperature and pressure for each measurenment. The equilibrium compositions of each phase were analyzed using Gas Chromatography. The experimental data obtained in this work were correlated with NRTL and UNIQUAC models with root mean square deviation between esperimental and calculated equilibrium compositions of 0.03% and 0.04% respectively.

Modeling and Uncertainty Quantification of Vapor Sorption and Diffusion in Heterogeneous Polymers

DOE PAGES

Sun, Yunwei; Harley, Stephen J.; Glascoe, Elizabeth A.

2015-08-13

A high-fidelity model of kinetic and equilibrium sorption and diffusion is developed and exercised. The gas-diffusion model is coupled with a triple-sorption mechanism: Henry’s law absorption, Langmuir adsorption, and pooling or clustering of molecules at higher partial pressures. Sorption experiments are conducted and span a range of relative humidities (0-95%) and temperatures (30-60°C). Kinetic and equilibrium sorption properties and effective diffusivity are determined by minimizing the absolute difference between measured and modeled uptakes. Uncertainty quantification and sensitivity analysis methods are described and exercised herein to demonstrate the capability of this modeling approach. Water uptake in silica-filled and unfilled poly(dimethylsiloxane) networksmore » is investigated; however, the model is versatile enough to be used with a wide range of materials and vapors.« less

Redifferentiation of dedifferentiated bovine articular chondrocytes enhanced by cyclic hydrostatic pressure under a gas-controlled system.

PubMed

Kawanishi, Makoto; Oura, Atsuhiro; Furukawa, Katsuko; Fukubayashi, Toru; Nakamura, Kozo; Tateishi, Tetsuya; Ushida, Takashi

2007-05-01

Hydrostatic pressure is one of the most frequently used mechanical stimuli in chondrocyte experiments. A variety of hydrostatic pressure loading devices have been used in cartilage cell experiments. However, no gas-controlled system with other than a low pressure load was used up to this time. Hence we used a polyolefin bag from which gas penetration was confirmed. Chondrocytes were extracted from bovine normal knee joint cartilage. After 3 passages, dedifferentiated chondrocytes were applied to form a pellet. These pellets were cultured in chemically defined serum-free medium with ITS+Premix for 3 days. Then 5 MPa of cyclic hydrostatic pressure was applied at 0.5 Hz for 4 h per day for 4 days. Semiquantitative reverse transcriptase-polymerase chain reaction showed a 5-fold increase in the levels of aggrecan mRNA due to cyclic hydrostatic pressure load (p<0.01). Type II collagen mRNA levels were also upregulated 4-fold by a cyclic hydrostatic pressure load (p<0.01). Type I collagen mRNA levels were similarly reduced in the cyclic hydrostatic pressure load group and in the control group. The partial oxygen pressure (PO2) and partial carbon dioxide pressure (PCO2) of the medium in the bag reached equilibrium in 24 h, and no significant change was observed for 3 days afterwards. PO2 and PCO2 were very well controlled. The loaded pellet showed better safranin O/fast green staining than did the control pellet. Metachromatic staining by Alcian blue staining was found to be stronger in the loaded than in the control pellets. The extracellular matrices excretion of loaded pellets was higher than that of control pellets. These results suggest that gas-controlled cyclic hydrostatic pressure enhanced the cartilaginous matrix formation of dedifferentiated cells differentiated in vitro.

Instability and thermal conductivity of pressure-densified and elastically altered orientational glass of Buckminsterfullerene

NASA Astrophysics Data System (ADS)

Johari, G. P.; Andersson, Ove; Sundqvist, Bertil

2018-04-01

We report on the temperature, pressure, and time (T, p, and t)-dependent features of thermal conductivity, κ, of partially ordered, non-equilibrium state of C60-OG, the orientational glass of Buckminsterfullerene (at T below the orientational freezing temperature Tog) made more unstable (i) by partially depressurizing its high-p formed state to elastically expand it and (ii) by further pressurizing that state to elastically contract it. The sub-Tog effects observed on heating of C60-OG differ from those of glasses because phonon propagation depends on the ratio of two well-defined orientational states of C60 molecules and the density of the solid. A broad peak-like feature appears at T near Tog in the κ-T plots of C60-OG formed at 0.7 GPa, depressurized to 0.2 GPa and heated at 0.2 GPa, which we attribute to partial overlap of the sub-Tog and Tog features. A sub-Tog local minimum appears in the κ-T plots at T well below Tog of C60-OG formed at 0.1 GPa, pressurized to 0.5 GPa and heated at 0.5 GPa and it corresponds to the state of maximum disorder. Although Buckminsterfullerene is regarded as an orientationally disordered crystal, variation of its properties with T and p is qualitatively different from other such crystals. We discuss the findings in terms of the nature of its disorder, sensitivity of its rotational dynamics to temperature, and the absence of the Johari-Goldstein relaxation. All seem to affect the phenomenology of its glass-like transition.

Influence of arc current and pressure on non-chemical equilibrium air arc behavior

NASA Astrophysics Data System (ADS)

Yi, WU; Yufei, CUI; Jiawei, DUAN; Hao, SUN; Chunlin, WANG; Chunping, NIU

2018-01-01

The influence of arc current and pressure on the non-chemical equilibrium (non-CE) air arc behavior of a nozzle structure was investigated based on the self-consistent non-chemical equilibrium model. The arc behavior during both the arc burning and arc decay phases were discussed at different currents and different pressures. We also devised the concept of a non-equilibrium parameter for a better understanding of non-CE effects. During the arc burning phase, the increasing current leads to a decrease of the non-equilibrium parameter of the particles in the arc core, while the increasing pressure leads to an increase of the non-equilibrium parameter of the particles in the arc core. During the arc decay phase, the non-CE effect will decrease by increasing the arc burning current and the nozzle pressure. Three factors together—convection, diffusion and chemical reactions—influence non-CE behavior.

The isotropic-nematic and nematic-nematic phase transition of binary mixtures of tangent hard-sphere chain fluids: An analytical equation of state

NASA Astrophysics Data System (ADS)

van Westen, Thijs; Vlugt, Thijs J. H.; Gross, Joachim

2014-01-01

An analytical equation of state (EoS) is derived to describe the isotropic (I) and nematic (N) phase of linear- and partially flexible tangent hard-sphere chain fluids and their mixtures. The EoS is based on an extension of Onsager's second virial theory that was developed in our previous work [T. van Westen, B. Oyarzún, T. J. H. Vlugt, and J. Gross, J. Chem. Phys. 139, 034505 (2013)]. Higher virial coefficients are calculated using a Vega-Lago rescaling procedure, which is hereby generalized to mixtures. The EoS is used to study (1) the effect of length bidispersity on the I-N and N-N phase behavior of binary linear tangent hard-sphere chain fluid mixtures, (2) the effect of partial molecular flexibility on the binary phase diagram, and (3) the solubility of hard-sphere solutes in I- and N tangent hard-sphere chain fluids. By changing the length bidispersity, two types of phase diagrams were found. The first type is characterized by an I-N region at low pressure and a N-N demixed region at higher pressure that starts from an I-N-N triphase equilibrium. The second type does not show the I-N-N equilibrium. Instead, the N-N region starts from a lower critical point at a pressure above the I-N region. The results for the I-N region are in excellent agreement with the results from molecular simulations. It is shown that the N-N demixing is driven both by orientational and configurational/excluded volume entropy. By making the chains partially flexible, it is shown that the driving force resulting from the configurational entropy is reduced (due to a less anisotropic pair-excluded volume), resulting in a shift of the N-N demixed region to higher pressure. Compared to linear chains, no topological differences in the phase diagram were found. We show that the solubility of hard-sphere solutes decreases across the I-N phase transition. Furthermore, it is shown that by using a liquid crystal mixture as the solvent, the solubility difference can by maximized by tuning the composition. Theoretical results for the Henry's law constant of the hard-sphere solute are in good agreement with the results from molecular simulation.

Pressure-dependent boron isotopic fractionation observed by column chromatography

NASA Astrophysics Data System (ADS)

Musashi, M.; Oi, T.; Matsuo, M.; Nomura, M.

2007-12-01

Boron isotopic fractionation factor ( S ) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25°C, using 0.1 mmol/L boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at atmospheric pressure at 25°C with the boron concentration of 10 mmol/L, but were larger than the values at the same condition with much higher concentration of 100 and 501 mmol/L, indicating that borate-polymerization reducing the isotopic fractionation was negligible. However, calculations based on the theory of isotope distribution between two phases estimated that 21% (5MPa) and 47% (17MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)3-form, instead of in the four-coordinated B(OH)4--form, at high pressures even with the very diluted solution. We discussed this discrepancy by introducing (1) hydration or (2) a partial molar volume difference between isotopic molecules. It was inferred that borate ions were partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Alternatively, it was likely that the S value decreased with increasing pressure, because the difference of the partial isotopic molar volumes between 10B(OH)3 and 11B(OH)3 was larger than that between 10B(OH)4- and 11B(OH)4-. If either will be the case, the influence of a pressure upon the isotope effect may not be negligible for boron isotopic exchange equilibrium. This knowledge is crucial for the principle of the boron isotopic pH-metry reconstructing a chemical variation at the paleo-deep oceanic environment where the early life may have been evolved.

Interfacial Alloy Hydride Destabilization in Mg/Pd Thin Films

NASA Astrophysics Data System (ADS)

Chung, C.-J.; Lee, Sang-Chul; Groves, James R.; Brower, Edwin N.; Sinclair, Robert; Clemens, Bruce M.

2012-03-01

Recently, a large increase in the equilibrium hydrogen pressure has been reported for MG thin films capped with a Pd layer. We show that this increase is due to intermixing of Mg and Pd, as opposed to a strain effect as previously claimed. Transmission electron microscopy and depth profiling x-ray photoemission spectroscopy are used to directly measure interfacial intermixing between Mg and Pd, and we find that intermixing and equilibrium hydrogen pressure both increase with annealing. We present a thermodynamic model of the effect of alloying on equilibrium pressure, and find that the observed equilibrium pressure increase is consistent with the observed thickness of the intermixed region, which is of the order of a few nm. We also show that stress measured during hydrogenation corresponds to a negligible increase in equilibrium pressure.

Effects of Non-Equilibrium Plasmas on Low-Pressure, Premixed Flames. Part 1: CH* Chemiluminescence, Temperature, and OH

DTIC Science & Technology

2018-01-16

1    Effects of Non -Equilibrium Plasmas on Low-Pressure, Premixed Flames. Part 1: CH* Chemiluminescence, Temperature, and OH Ting Li, Igor V...investigate the effects of nanosecond, repetitively-pulsed, non -equilibrium plasma discharges on laminar, low-pressure, premixed burner-stabilized hydrogen/O2...sources, both of which generate uniform, low-temperature, volumetric, non -equilibrium plasma discharges, are used to study changes in

Enhanced densification under shock compression in porous silicon

DOE PAGES

Lane, J. Matthew; Thompson, Aidan Patrick; Vogler, Tracy

2014-10-27

Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. The mechanism driving this behavior was not completely determined. We present evidence from atomistic simulation that pure silicon belongs to this anomalous class of materials and demonstrate the associated mechanisms responsible for the effect in porous silicon. Atomistic response indicates that local shear strain in the neighborhood of collapsing pores catalyzes a local solid-solid phase transformation even when bulk pressures are below the thermodynamicmore » phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.« less

Synthesis of Size-Tunable CO2-Philic Imprinted Polymeric Particles (MIPs) for Low-Pressure CO2 Capture Using Oil-in-Oil Suspension Polymerization.

PubMed

Nabavi, Seyed Ali; Vladisavljević, Goran T; Zhu, Yidi; Manović, Vasilije

2017-10-03

Highly selective molecularly imprinted poly[acrylamide-co-(ethylene glycol dimethacrylate)] polymer particles (MIPs) for CO 2 capture were synthesized by suspension polymerization via oil-in-oil emulsion. Creation of CO 2 -philic, amide-decorated cavities in the polymer matrix led to a high affinity to CO 2 . At 0.15 bar CO 2 partial pressure, the CO 2 /N 2 selectivity was 49 (corresponding to 91% purity of the gas stream after regeneration), and reached 97 at ultralow CO 2 partial pressures. The imprinted polymers showed considerably higher CO 2 uptakes compared to their nonimprinted counterparts, and the maximum equilibrium CO 2 capture capacity of 1.1 mmol g -1 was achieved at 273 K. The heat of adsorption was below 32 kJ mol -1 and the temperature of onset of intense thermal degradation was 351-376 °C. An increase in monomer-to-cross-linker molar ratio in the dispersed phase up to 1:2.5 led to a higher affinity toward CO 2 due to higher density of selective amide groups in the polymer network. MIPs are a promising option for industrial packed and fluidized bed CO 2 capture systems due to large particles with a diameter up to 1200 μm and irregular oblong shapes formed due to arrested coalescence during polymerization, occurring as a result of internal elasticity of the partially polymerized semisolid drops.

Application of a High-Throughput Analyzer in Evaluating Solid Adsorbents for Post-Combustion Carbon Capture via Multicomponent Adsorption of CO2, N-2, and H2O

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

Mason, JA; McDonald, TM; Bae, TH

Despite the large number of metal-organic frameworks that have been studied in the context of post-combustion carbon capture, adsorption equilibria of gas mixtures including CO2, N-2, and H2O, which are the three biggest components of the flue gas emanating from a coal- or natural gas-fired power plant, have never been reported. Here, we disclose the design and validation of a high-throughput multicomponent adsorption instrument that can measure equilibrium adsorption isotherms for mixtures of gases at conditions that are representative of an actual flue gas from a power plant. This instrument is used to study 15 different metal-organic frameworks, zeolites, mesoporousmore » silicas, and activated carbons representative of the broad range of solid adsorbents that have received attention for CO2 capture. While the multicomponent results presented in this work provide many interesting fundamental insights, only adsorbents functionalized with alkylamines are shown to have any significant CO2 capacity in the presence of N-2 and H2O at equilibrium partial pressures similar to those expected in a carbon capture process. Most significantly, the amine-appended metal organic framework mmen-Mg-2(dobpdc) (mmen = N,N'-dimethylethylenediamine, dobpdc (4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate) exhibits a record CO2 capacity of 4.2 +/- 0.2 mmol/g (16 wt %) at 0.1 bar and 40 degrees C in the presence of a high partial pressure of H2O.« less

Application of a high-throughput analyzer in evaluating solid adsorbents for post-combustion carbon capture via multicomponent adsorption of CO2, N2, and H2O.

PubMed

Mason, Jarad A; McDonald, Thomas M; Bae, Tae-Hyun; Bachman, Jonathan E; Sumida, Kenji; Dutton, Justin J; Kaye, Steven S; Long, Jeffrey R

2015-04-15

Despite the large number of metal-organic frameworks that have been studied in the context of post-combustion carbon capture, adsorption equilibria of gas mixtures including CO2, N2, and H2O, which are the three biggest components of the flue gas emanating from a coal- or natural gas-fired power plant, have never been reported. Here, we disclose the design and validation of a high-throughput multicomponent adsorption instrument that can measure equilibrium adsorption isotherms for mixtures of gases at conditions that are representative of an actual flue gas from a power plant. This instrument is used to study 15 different metal-organic frameworks, zeolites, mesoporous silicas, and activated carbons representative of the broad range of solid adsorbents that have received attention for CO2 capture. While the multicomponent results presented in this work provide many interesting fundamental insights, only adsorbents functionalized with alkylamines are shown to have any significant CO2 capacity in the presence of N2 and H2O at equilibrium partial pressures similar to those expected in a carbon capture process. Most significantly, the amine-appended metal organic framework mmen-Mg2(dobpdc) (mmen = N,N'-dimethylethylenediamine, dobpdc (4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate) exhibits a record CO2 capacity of 4.2 ± 0.2 mmol/g (16 wt %) at 0.1 bar and 40 °C in the presence of a high partial pressure of H2O.

Influence of oxygen partial pressure on surface tension and its temperature coefficient of molten iron

NASA Astrophysics Data System (ADS)

Ozawa, S.; Suzuki, S.; Hibiya, T.; Fukuyama, H.

2011-01-01

Influences of oxygen partial pressure, PO2, of ambient atmosphere and temperature on surface tension and its temperature coefficient for molten iron were experimentally investigated by an oscillating droplet method using an electromagnetic levitation furnace. We successfully measured the surface tension of molten iron over a very wide temperature range of 780 K including undercooling condition in a well controlled PO2 atmosphere. When PO2 is fixed at 10-2 Pa at the inlet of the chamber, a "boomerang shape" temperature dependence of surface tension was experimentally observed; surface tension increased and then decreased with increasing temperature. The pure surface tension of molten iron was deduced from the negative temperature coefficient in the boomerang shape temperature dependence. When the surface tension was measured under the H2-containing gas atmosphere, surface tension did not show a linear relationship against temperature. The temperature dependence of the surface tension shows anomalous kink at around 1850 K due to competition between the temperature dependence of PO2 and that of the equilibrium constant of oxygen adsorption.

Theoretical considerations on the pathophysiology of normal pressure hydrocephalus (NPH) and NPH-related dementia.

PubMed

Hamlat, Abderrahmane; Adn, Mahmoudreza; Sid-ahmed, Seddik; Askar, Brahim; Pasqualini, Edouardo

2006-01-01

Normal pressure hydrocephalus (NPH) is considered to be an example of reversible dementia although clinical improvement after shunting varies from subject to subject, and recent studies have pointed to a possible link with other dementia. The authors consider that the craniospinal compartment is a partially closed sphere with control device systems represented by the spinal axis and the sagittal sinus-arachnoid villi complex which interact with each other in the clinical patient setting. We hypothesise that changing spinal compliance by altering the flow process and CSF dynamics lead to hydrocephalus. Therefore four NPH types have been distinguished according to the alterations in spinal compliance, decrease in CSF absorption at the sagittal sinus or both occurrences. The authors consider that NPH and NPH-related diseases (NPH-RD) are initiated by the same common final pathway and demonstrate that NPH could represent an initial stage of NPH-RD. Progression of clinical signs can be explained as damage to the cerebral tissue by both intermittent increased intracranial pressure and pulse pressure waves leading to periventricular ischaemia. In addition, they believe that both volume equilibrium and spinal compliance are restored in patients who improve after CSF shunt, whereas in patients whose condition does not improve, only volume equilibrium is restored and not spinal compliance, which was the underlying cause of hydrocephalus in such cases. They therefore wonder whether cervical decompression should not be indicated in patients who show no improvement. Although attractive, this analysis warrants confirmation from clinical, radiological, and hydrodynamic studies.

Turbulence Modeling Effects on the Prediction of Equilibrium States of Buoyant Shear Flows

NASA Technical Reports Server (NTRS)

Zhao, C. Y.; So, R. M. C.; Gatski, T. B.

2001-01-01

The effects of turbulence modeling on the prediction of equilibrium states of turbulent buoyant shear flows were investigated. The velocity field models used include a two-equation closure, a Reynolds-stress closure assuming two different pressure-strain models and three different dissipation rate tensor models. As for the thermal field closure models, two different pressure-scrambling models and nine different temperature variance dissipation rate, Epsilon(0) equations were considered. The emphasis of this paper is focused on the effects of the Epsilon(0)-equation, of the dissipation rate models, of the pressure-strain models and of the pressure-scrambling models on the prediction of the approach to equilibrium turbulence. Equilibrium turbulence is defined by the time rate (if change of the scaled Reynolds stress anisotropic tensor and heat flux vector becoming zero. These conditions lead to the equilibrium state parameters. Calculations show that the Epsilon(0)-equation has a significant effect on the prediction of the approach to equilibrium turbulence. For a particular Epsilon(0)-equation, all velocity closure models considered give an equilibrium state if anisotropic dissipation is accounted for in one form or another in the dissipation rate tensor or in the Epsilon(0)-equation. It is further found that the models considered for the pressure-strain tensor and the pressure-scrambling vector have little or no effect on the prediction of the approach to equilibrium turbulence.

Experimental partitioning of rare earth elements and scandium among armalcolite, ilmenite, olivine and mare basalt liquid

NASA Technical Reports Server (NTRS)

Irving, A. J.; Merrill, R. B.; Singleton, D. E.

1978-01-01

An experimental study was carried out to measure partition coefficients for two rare-earth elements (Sm and Tm) and Sc among armalcolite, ilmenite, olivine and liquid coexisting in a system modeled on high-Ti mare basalt 74275. This 'primitive' sample was chosen for study because its major and trace element chemistry as well as its equilibrium phase relations at atmospheric pressure are known from previous studies. Beta-track analytical techniques were used so that partition coefficients could be measured in an environment whose bulk trace element composition is similar to that of the natural basalt. Partition coefficients for Cr and Mn were determined in the same experiments by microprobe analysis. The only equilibrium partial melting model appears to be one in which ilmenite is initially present in the source region but is consumed by melting before segregation of the high-Ti mare basalt liquid from the residue.

The surface stability and morphology of tobermorite 11 Å from first principles

NASA Astrophysics Data System (ADS)

Mutisya, Sylvia M.; Miranda, Caetano R.

2018-06-01

Tobermorite minerals are important in many industrial processes typically occurring in hydrous environment. Their functionality is therefore governed in various aspects by their morphology and surface stability/reactivity. Here, we present the results of the surface energies and morphology of normal tobermorite 11 Å in a water vapor environment investigated by employing first principles atomistic thermodynamic calculations. For the low index tobermorite surfaces studied, the calculated surface energies fall within a narrow range (0.41-0.97 J/m2) with the (0 0 4) surface being the most stable. The equilibrium morphology is a thin pseudohexagonal plate elongated along the b axis. The hydrated surfaces are more stable at high water vapor chemical potentials with the stability enhanced as the water partial pressures are varied from ambient to supercritical hydrothermal conditions. Increasing the water vapor chemical potential gives rise to a smaller size of the tobermorite crystal, with the equilibrium morphology remaining unaltered.

Solubility of noble gases in serpentine - Implications for meteoritic noble gas abundances

NASA Technical Reports Server (NTRS)

Zaikowski, A.; Schaeffer, O. A.

1979-01-01

An investigation of the solubilities of the noble gases from synthesis and solubility studies of the sheet silicate mineral serpentine in carbonaceous chondrites is presented. Hydrothermal synthesis and exchange experiments were made at 340C and 1 kbar with noble gas partial pressures from 2 times 10 to the -8th power to 0.1 atm. The measured distribution coefficients for noble gases are not sufficiently high to account for the trapped noble gases in carbonaceous chondrites by exchange in solar nebula if meteoritic minerals have comparable distribution coefficients. Also, serpentine gains and loses noble gases to approach equilibrium values with the terrestrial atmosphere, indicating that this exposure may have influenced the noble gas abundances in phyllosilicate minerals of these chondrites. The dispersion of K-Ar ages of carbonaceous chondrites could be the result of phyllosilicates approaching equilibrium solubility of atmospheric Ar-40.

Direct computation of thermodynamic properties of chemically reacting air with consideration to CFD

NASA Astrophysics Data System (ADS)

Iannelli, Joe

2003-10-01

This paper details a two-equation procedure to calculate exactly mass and mole fractions, pressure, temperature, specific heats, speed of sound and the thermodynamic and jacobian partial derivatives of pressure and temperature for a five-species chemically reacting equilibrium air. The procedure generates these thermodynamic properties using as independent variables either pressure and temperature or density and internal energy, for CFD applications. An original element in this procedure consists in the exact physically meaningful solution of the mass-fraction and mass-action equations. Air-equivalent molecular masses for oxygen and nitrogen are then developed to account, within a mixture of only oxygen and nitrogen, for the presence of carbon dioxide, argon and the other noble gases within atmospheric air. The mathematical formulation also introduces a versatile system non-dimensionalization that makes the procedure uniformly applicable to flows ranging from shock-tube flows with zero initial velocity to aerothermodynamic flows with supersonic/hypersonic free-stream Mach numbers. Over a temperature range of more than 10000 K and pressure and density ranges corresponding to an increase in altitude in standard atmosphere of 30000 m above sea level, the predicted distributions of mole fractions, constant-volume specific heat, and speed of sound for the model five species agree with independently published results, and all the calculated thermodynamic properties, including their partial derivatives, remain continuous, smooth, and physically meaningful.

Some comments on thermodynamic consistency for equilibrium mixture equations of state

DOE PAGES

Grove, John W.

2018-03-28

We investigate sufficient conditions for thermodynamic consistency for equilibrium mixtures. Such models assume that the mass fraction average of the material component equations of state, when closed by a suitable equilibrium condition, provide a composite equation of state for the mixture. Here, we show that the two common equilibrium models of component pressure/temperature equilibrium and volume/temperature equilibrium (Dalton, 1808) define thermodynamically consistent mixture equations of state and that other equilibrium conditions can be thermodynamically consistent provided appropriate values are used for the mixture specific entropy and pressure.

Phosphorus atomic layer doping in Ge using RPCVD

NASA Astrophysics Data System (ADS)

Yamamoto, Yuji; Kurps, Rainer; Mai, Christian; Costina, Ioan; Murota, Junichi; Tillack, Bernd

2013-05-01

Phosphorus atomic layer doping (P-ALD) in Ge is investigated at temperatures between 100 °C and 400 °C using a single wafer reduced pressure chemical vapor deposition (RPCVD) system. Hydrogen-terminated and hydrogen-free Ge (1 0 0) surfaces are exposed to PH3 at different PH3 partial pressures after interrupting Ge growth. The adsorption and reaction of PH3 proceed on a hydrogen-free Ge surface. For all temperatures and PH3 partial pressures used for the P-ALD, the P dose increased with increasing PH3 exposure time and saturated. The saturation value of the incorporated P dose at 300 °C is ˜1.5 × 1014 cm-3, which is close to a quarter of a monolayer of the Ge (1 0 0) surface. The P dose could be simulated assuming a Langmuir-type kinetics model with a saturation value of Nt = 1.55 × 1014 cm-2 (a quarter of a monolayer), reaction rate constant kr = 77 s-1 and thermal equilibrium constant K = 3.0 × 10-2 Pa-1. An electrically active P concentration of 5-6 × 1019 cm-3, which is a 5-6 times higher thermal solubility of P in Ge, is obtained by multiple P spike fabrication using the P-ALD process.

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

Grove, John W.

We investigate sufficient conditions for thermodynamic consistency for equilibrium mixtures. Such models assume that the mass fraction average of the material component equations of state, when closed by a suitable equilibrium condition, provide a composite equation of state for the mixture. Here, we show that the two common equilibrium models of component pressure/temperature equilibrium and volume/temperature equilibrium (Dalton, 1808) define thermodynamically consistent mixture equations of state and that other equilibrium conditions can be thermodynamically consistent provided appropriate values are used for the mixture specific entropy and pressure.

Theoretical investigation of flash vaporisation in a screw expander

NASA Astrophysics Data System (ADS)

Vasuthevan, Hanushan; Brümmer, Andreas

2017-08-01

In the present study flash vaporisation of liquid injection in a twin screw expander for a Trilateral Flash Cycle (TFC) is examined theoretically. The TFC process comprises a pressure increase in the working fluid, followed by heating the liquid close to boiling point. The hot liquid is injected into the working chamber of a screw expander. During this process the pressure of the liquid drops below the saturation pressure, while the temperature of the liquid remains virtually constant. Hence the liquid is superheated and in a metastable state. The liquid jet seeks to achieve a stable state in thermodynamic equilibrium and is therefore partially vaporised. This effect is referred to as flash vaporisation. Accordingly, a two-phase mixture, consisting of vapour and liquid, exists in the working chamber. Thermodynamic simulations were carried out using water as the working fluid for representative screw expander geometry. The simulations presented are performed from two different aspects during the filling process of a screw expander. The first case is the vaporisation of the injected liquid in a state of thermodynamic equilibrium, whereby the two-phase mixture is treated entirely as a compressible and homogeneous gas. The second case considers flashing efficiency. It describes the quantity of flashed vapour and consists of a liquid and vapour domain. Both models are compared and analysed with respect to the operational behaviour of a screw expander.

One-dimensional Vlasov-Maxwell equilibrium for the force-free Harris sheet.

PubMed

Harrison, Michael G; Neukirch, Thomas

2009-04-03

In this Letter, the first nonlinear force-free Vlasov-Maxwell equilibrium is presented. One component of the equilibrium magnetic field has the same spatial structure as the Harris sheet, but whereas the Harris sheet is kept in force balance by pressure gradients, in the force-free solution presented here force balance is maintained by magnetic shear. Magnetic pressure, plasma pressure and plasma density are constant. The method used to find the equilibrium is based on the analogy of the one-dimensional Vlasov-Maxwell equilibrium problem to the motion of a pseudoparticle in a two-dimensional conservative potential. The force-free solution can be generalized to a complete family of equilibria that describe the transition between the purely pressure-balanced Harris sheet to the force-free Harris sheet.

METHOD FOR PUMPING GASES AT LOW VACUUM PRESSURES

DOEpatents

Milleron, N.

1962-06-01

A method is given for pumping overpressure "pulses" or "bursts" of gases without a significant rise in base pressure within a "gettering-type" vacuum pump having surfaces within the pumping cavity coated with or comprising clean gettering metal, e.g., Mo or Ta. The cavity is first pumped down by any convenient means to an equilibrium base pressure in the range desired, generally below 10/sup -6/ mm Hg. At this pressure, the metal immediately adsorbs overpressures or "bursts" of gases striking same with thermal motion without raising the base pressure significantiy. Desorption takes place at an equilibrium rate which, of course, is dependent upon the equilibrium pressure, and such desorbed gases are continuously removed by diffuaion pump or other pumping, whereby said overpressures or "bursts" of gases are removed without a rise in the equilibrium pressure and/or back diffusion of the gaseous pulse from the pumping cavity. (AEC)

Pluto's atmosphere - Models based on refraction, inversion, and vapor-pressure equilibrium

NASA Technical Reports Server (NTRS)

Eshleman, Von R.

1989-01-01

Viking spacecraft radio-occultation measurements indicate that, irrespective of substantial differences, the polar ice cap regions on Mars have inversions similar to those of Pluto, and may also share vapor pressure equilibrium characteristics at the surface. This temperature-inversion phenomenon occurs in a near-surface boundary layer; surface pressure-temperature may correspond to the vapor-pressure equilibrium with CH4 ice, or the temperature may be slightly higher to match the value derived from IRAS data.

Raining a magma ocean: Thermodynamics of rocky planets after a giant impact

NASA Astrophysics Data System (ADS)

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

2017-12-01

Rocky planets in exoplanetary systems have equilibrium temperatures up to a few 1000 K. The thermal evolution after a giant impact is sensitive to the equilibrium temperature. Post-impact rocky bodies are thermally stratified, with cooler, lower-entropy silicate overlain by vaporized, higher-entropy silicate. The radii of impact-vaporized rocky planets are much larger than the radii of equivalent condensed bodies. Furthermore, after some high-energy, high-angular momentum collisions, the post-impact body exceeds the corotation limit for a rocky planet and forms a synestia. Initially, volatiles and silicates are miscible at the high temperatures of the outer layer. If the equilibrium temperature with the star is lower than the silicate condensation temperature ( 2000 K), silicate droplets form at the photosphere and fall while volatile components remain in the vapor. Radiation and turbulent convection cool the vapor outer layer to the silicate vapor curve. A distinct magma ocean forms as the thermal profile crosses the silicate vapor curve and the critical curves for the volatiles. Near the temperatures and pressures of the critical curves, volatiles and silicates are partially soluble in each other. As the system continues cooling, the volatile vapor and silicate liquid separate toward the end member compositions, which are determined by the equilibrium temperature and the total vapor pressure of volatiles. If the equilibrium temperature with the star is near or above the condensation temperature for silicates, there would be limited condensation at the photosphere. Initially, the cooler lower mantle would slowly, diffusively equilibrate with the hotter upper mantle. In some cases, the thermal profile may cross the silicate vapor curve in the middle of the silicate layer, producing a silicate rain layer within the body. With continued evolution toward an adiabatic thermal profile, the body would separate into a silicate liquid layer underlying a silicate-volatile vapor layer. As the hottest rocky planets become tidally locked to their star, cooling progresses asymmetrically. The timing and degree of differentiation of rocky planets into silicate mantles and volatile atmospheres depends on the thermal evolution of vaporized rocky planets and may vary widely with equilibrium temperature.

Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

DOE PAGES

Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

2015-04-28

The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO 2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO 2-induced drifts in thermocouple readings.more » Oxygen equilibrium is monitored using both an O 2 sensor and the transient behavior of the resistance as a proxy. A pO 2 range of 10 -25–10 0 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi 2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO 2 on a 1 % Nb-doped SrTiO 3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO 2 range of 10 -19–10 -8 atm at 973 K for the donor-doped single crystals is observed.« less

EAST kinetic equilibrium reconstruction combining with Polarimeter-Interferometer internal measurement constraints

NASA Astrophysics Data System (ADS)

Lian, H.; Liu, H. Q.; Li, K.; Zou, Z. Y.; Qian, J. P.; Wu, M. Q.; Li, G. Q.; Zeng, L.; Zang, Q.; Lv, B.; Jie, Y. X.; EAST Team

2017-12-01

Plasma equilibrium reconstruction plays an important role in the tokamak plasma research. With a high temporal and spatial resolution, the POlarimeter-INTerferometer (POINT) system on EAST has provided effective measurements for 102s H-mode operation. Based on internal Faraday rotation measurements provided by the POINT system, the equilibrium reconstruction with a more accurate core current profile constraint has been demonstrated successfully on EAST. Combining other experimental diagnostics and external magnetic fields measurement, the kinetic equilibrium has also been reconstructed on EAST. Take the pressure and edge current information from kinetic EFIT into the equilibrium reconstruction with Faraday rotation constraint, the new equilibrium reconstruction not only provides a more accurate internal current profile but also contains edge current and pressure information. One time slice result using new kinetic equilibrium reconstruction with POINT data constraints is demonstrated in this paper and the result shows there is a reversed shear of q profile and the pressure profile is also contained. The new improved equilibrium reconstruction is greatly helpful to the future theoretical analysis.

Foundations of atmospheric pressure non-equilibrium plasmas

NASA Astrophysics Data System (ADS)

Bruggeman, Peter J.; Iza, Felipe; Brandenburg, Ronny

2017-12-01

Non-equilibrium plasmas have been intensively studied over the past century in the context of material processing, environmental remediation, ozone generation, excimer lamps and plasma display panels. Research on atmospheric pressure non-equilibrium plasmas intensified over the last two decades leading to a large variety of plasma sources that have been developed for an extended application range including chemical conversion, medicine, chemical analysis and disinfection. The fundamental understanding of these discharges is emerging but there remain a lot of unexplained phenomena in these intrinsically complex plasmas. The properties of non-equilibrium plasmas at atmospheric pressure span over a huge range of electron densities as well as heavy particle and electron temperatures. This paper provides an overview of the key underlying processes that are important for the generation and stabilization of atmospheric pressure non-equilibrium plasmas. The unique physical and chemical properties of theses discharges are also summarized.

Heating of the solar chromosphere by ionization pumping

NASA Technical Reports Server (NTRS)

Lindsey, C. A.

1981-01-01

A new theory is proposed to explain the heating of the solar chromosphere, and possibly the corona, by the dissipation of hydrodynamic compression waves. The basis of the dissipative mechanism, here referred to as ionization pumping, is hysteresis caused by irreversible relaxation of the chromospheric medium to ionization equilibrium following pressure perturbations. In the middle chromosphere, where hydrogen is partially ionized, it is shown that ionization pumping will cause strong dissipation of waves whose periods are 200s or less. This could cause heating of the chromosphere sufficient to compensate for the radiative losses. The mechanism retains a high efficiency for waves of arbitrarily small amplitude and, thus, can be more efficient than shock dissipation for small perturbations in pressure. The formation of shocks therefore is not required for the dissipation of waves whose periods are several minutes or less.

Chemistry of the surface and lower atmosphere of Venus

NASA Technical Reports Server (NTRS)

Fegley, B., Jr.; Treiman, A.

1992-01-01

A comprehensive overview of the chemical interactions between the atmosphere and surface of Venus is presented. Earth-based, earth-orbital, and spacecraft data on the composition of the atmosphere and surface of Venus are presented and applied to quantitative evaluations of the chemical interactions between carbon, hydrogen, sulfur, chlorine, fluorine, and nitrogen-containing gases and possible minerals on the Venus surface. The calculation results are used to predict stable minerals and mineral assemblages on the Venus surface to determine which, if any, atmospheric gases are buffered by mineral assemblages on the surface, and to critically review and assess prior work on atmosphere-surface chemistry on Venus. It is concluded that the CO2 pressure on Venus is comparable to the CO2 equilibrium partial pressure developed by the calcite + wollastonite + quartz assemblage at the mean Venus surface temperature of 740 K.

Thermodynamic equilibrium calculations of hydrogen production from the combined processes of dimethyl ether steam reforming and partial oxidation

NASA Astrophysics Data System (ADS)

Semelsberger, Troy A.; Borup, Rodney L.

Thermodynamic analyses of producing a hydrogen-rich fuel-cell feed from the combined processes of dimethyl ether (DME) partial oxidation and steam reforming were investigated as a function of oxygen-to-carbon ratio (0.00-2.80), steam-to-carbon ratio (0.00-4.00), temperature (100 °C-600 °C), pressure (1-5 atm) and product species. Thermodynamically, dimethyl ether processed with air and steam generates hydrogen-rich fuel-cell feeds; however, the hydrogen concentration is less than that for pure DME steam reforming. Results of the thermodynamic processing of dimethyl ether indicate the complete conversion of dimethyl ether to hydrogen, carbon monoxide and carbon dioxide for temperatures greater than 200 °C, oxygen-to-carbon ratios greater than 0.00 and steam-to-carbon ratios greater than 1.25 at atmospheric pressure (P = 1 atm). Increasing the operating pressure has negligible effects on the hydrogen content. Thermodynamically, dimethyl ether can produce concentrations of hydrogen and carbon monoxide of 52% and 2.2%, respectively, at a temperature of 300 °C, and oxygen-to-carbon ratio of 0.40, a pressure of 1 atm and a steam-to-carbon ratio of 1.50. The order of thermodynamically stable products (excluding H 2, CO, CO 2, DME, NH 3 and H 2O) in decreasing mole fraction is methane, ethane, isopropyl alcohol, acetone, n-propanol, ethylene, ethanol and methyl-ethyl ether; trace amounts of formaldehyde, formic acid and methanol are observed. Ammonia and hydrogen cyanide are also thermodynamically favored products. Ammonia is favored at low temperatures in the range of oxygen-to-carbon ratios of 0.40-2.50 regardless of the steam-to-carbon ratio employed. The maximum ammonia content (i.e., 40%) occurs at an oxygen-to-carbon ratio of 0.40, a steam-to-carbon ratio of 1.00 and a temperature of 100 °C. Hydrogen cyanide is favored at high temperatures and low oxygen-to-carbon ratios with a maximum of 3.18% occurring at an oxygen-to-carbon ratio of 0.40 and a steam-to-carbon ratio of 0.00 in the temperature range of 400 °C-500 °C. Increasing the system pressure shifts the equilibrium toward ammonia and hydrogen cyanide.

Equivalence of equations describing trace element distribution during equilibrium partial melting

NASA Technical Reports Server (NTRS)

Consolmagno, G. J.; Drake, M. J.

1976-01-01

It is shown that four equations used for calculating the evolution of trace-element abundances during equilibrium partial melting are mathematically equivalent. The equations include those of Hertogen and Gijbels (1976), Shaw (1970), Schilling (1971), and O'Nions and Clarke (1972). The general form to which all these equations reduce is presented, and an analysis is performed to demonstrate their mathematical equivalence. It is noted that the utility of the general equation flows from the nature of equilibrium (i.e., the final state is independent of the path by which that state is attained).

Heterogeneous nucleation in multi-component vapor on a partially wettable charged conducting particle. II. The generalized Laplace, Gibbs-Kelvin, and Young equations and application to nucleation.

PubMed

Noppel, M; Vehkamäki, H; Winkler, P M; Kulmala, M; Wagner, P E

2013-10-07

Based on the results of a previous paper [M. Noppel, H. Vehkamäki, P. M. Winkler, M. Kulmala, and P. E. Wagner, J. Chem. Phys. 139, 134107 (2013)], we derive a thermodynamically consistent expression for reversible or minimal work needed to form a dielectric liquid nucleus of a new phase on a charged insoluble conducting sphere within a uniform macroscopic one- or multicomponent mother phase. The currently available model for ion-induced nucleation assumes complete spherical symmetry of the system, implying that the seed ion is immediately surrounded by the condensing liquid from all sides. We take a step further and treat more realistic geometries, where a cap-shaped liquid cluster forms on the surface of the seed particle. We derive the equilibrium conditions for such a cluster. The equalities of chemical potentials of each species between the nucleus and the vapor represent the conditions of chemical equilibrium. The generalized Young equation that relates contact angle with surface tensions, surface excess polarizations, and line tension, also containing the electrical contribution from triple line excess polarization, expresses the condition of thermodynamic equilibrium at three-phase contact line. The generalized Laplace equation gives the condition of mechanical equilibrium at vapor-liquid dividing surface: it relates generalized pressures in neighboring bulk phases at an interface with surface tension, excess surface polarization, and dielectric displacements in neighboring phases with two principal radii of surface curvature and curvatures of equipotential surfaces in neighboring phases at that point. We also re-express the generalized Laplace equation as a partial differential equation, which, along with electrostatic Laplace equations for bulk phases, determines the shape of a nucleus. We derive expressions that are suitable for calculations of the size and composition of a critical nucleus (generalized version of the classical Kelvin-Thomson equation).

Pleural pressure theory revisited: a role for capillary equilibrium.

PubMed

Casha, Aaron R; Caruana-Gauci, Roberto; Manche, Alexander; Gauci, Marilyn; Chetcuti, Stanley; Bertolaccini, Luca; Scarci, Marco

2017-04-01

Theories elucidating pleural pressures should explain all observations including the equal and opposite recoil of the chest wall and lungs, the less than expected pleural hydrostatic gradient and its variation at lobar margins, why pleural pressures are negative and how pleural fluid circulation functions. A theoretical model describing equilibrium between buoyancy, hydrostatic forces, and capillary forces is proposed. The capillary equilibrium model described depends on control of pleural fluid volume and protein content, powered by an active pleural pump. The interaction between buoyancy forces, hydrostatic pressure and capillary pressure was calculated, and values for pleural thickness and pressure were determined using values for surface tension, contact angle, pleural fluid and lung densities found in the literature. Modelling can explain the issue of the differing hydrostatic vertical pleural pressure gradient at the lobar margins for buoyancy forces between the pleural fluid and the lung floating in the pleural fluid according to Archimedes' hydrostatic paradox. The capillary equilibrium model satisfies all salient requirements for a pleural pressure model, with negative pressures maximal at the apex, equal and opposite forces in the lung and chest wall, and circulatory pump action. This model predicts that pleural effusions cannot occur in emphysema unless concomitant heart failure increases lung density. This model also explains how the non-confluence of the lung with the chest wall (e.g., lobar margins) makes the pleural pressure more negative, and why pleural pressures would be higher after an upper lobectomy compared to a lower lobectomy. Pathological changes in pleural fluid composition and lung density alter the equilibrium between capillarity and buoyancy hydrostatic pressure to promote pleural effusion formation.

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

Brown, Matthew A.; Redondo, Amaia Beloqui; Duyckaerts, Nicolas

A new liquid microjet endstation designed for ultraviolet (UPS) and X-ray (XPS) photoelectron, and partial electron yield X-ray absorption (XAS) spectroscopies at the Swiss Light Source is presented. The new endstation, which is based on a Scienta HiPP-2 R4000 electron spectrometer, is the first liquid microjet endstation capable of operating in vacuum and in ambient pressures up to the equilibrium vapor pressure of liquid water at room temperature. In addition, the Scienta HiPP-2 R4000 energy analyzer of this new endstation allows for XPS measurements up to 7000 eV electron kinetic energy that will enable electronic structure measurements of bulk solutionsmore » and buried interfaces from liquid microjet samples. The endstation is designed to operate at the soft X-ray SIM beamline and at the tender X-ray Phoenix beamline. The endstation can also be operated using a Scienta 5 K ultraviolet helium lamp for dedicated UPS measurements at the vapor-liquid interface using either He I or He II α lines. The design concept, first results from UPS, soft X-ray XPS, and partial electron yield XAS measurements, and an outlook to the potential of this endstation are presented.« less

Destabilization of yttria-stabilized zirconia induced by molten sodium vanadate-sodium sulfate melts

NASA Technical Reports Server (NTRS)

Nagelberg, A. S.; Hamilton, J. C.

1985-01-01

The extent of surface destabilization of ZrO2 - 8 wt percent Y2O3 ceramic disks was determined after exposure to molten salt mixtures of sodium sulfate containing up to 15 mole percent sodium metavanadate (NaVO3) at 1173 K. The ceramic surface was observed to transform from the cubic/tetragonal to monoclinic phase, concurrent with chemical changes in the molten salt layer in contact with the ceramic. Significant attack rates were observed in both pure sulfate and metavanadate sulfate melts. The rate of attack was found to be quite sensitive to the mole fraction of vanadate in the molten salt solution and the partial pressure of sulfur trioxide in equilibrium with the salt melt. The observed parabolic rate of attack is interpreted to be caused by a reaction controlled by diffusion in the salt that penetrates into the porous layer formed by the destabilization. The parabolic rate constant in mixed sodium metavanadate - sodium sulfate melts was found to be proportional to the SO3 partial pressure and the square of the metavanadate concentration. In-situ Raman spectroscopic measurements allowed simultaneous observations of the ceramic phases and salt chemistry during the attack process.

The e[sup [minus

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

Holroyd, R.A.; Schwarz, H.A.; Stradowska, E.

The rate constants for attachment of excess electrons to 1,3-butadiene (k[sub a]) and detachment from the butadiene anion (k[sub d]) in n-hexane are reported. The equilibrium constant, K[sub eq] = k[sub a]/k[sub d], increases rapidly with pressure and decreases as the temperature increases. At -7[degree]C attachment is observed at 1 bar. At high pressures the attachment rate is diffusion controlled. The activation energy for detachment is about 21 kcal/mol; detachment is facilitated by the large entropy of activation. The reaction volumes for attachment range from -181 cm[sup 3]/mol at 400 bar to-122 cm[sup 3]/mol at 1500 bar and are largelymore » attributed to the electrostriction volume of the butadiene anion ([Delta][bar V][sub el]). Values of [Delta][bar V][sub el] calculated by a model, which includes a glassy shell of solvent molecules around the ion, are in agreement with experimental reaction volumes. The analysis indicates the partial molar volume of the electron in hexane is small and probably negative. It is shown that the entropies of reaction are closely related to the partial molar volumes of reaction. 22 refs., 5 figs., 5 tabs.« less

Effects of gas adsorption isotherm and liquid contact angle on capillary force for sphere-on-flat and cone-on-flat geometries.

PubMed

Hsiao, Erik; Marino, Matthew J; Kim, Seong H

2010-12-15

This paper explains the origin of the vapor pressure dependence of the asperity capillary force in vapor environments. A molecular adsorbate layer is readily formed on solid surface in ambient conditions unless the surface energy of the solid is low enough and unfavorable for vapor adsorption. Then, the capillary meniscus formed around the solid asperity contact should be in equilibrium with the adsorbate layer, not with the bare solid surface. A theoretical model incorporating the vapor adsorption isotherm into the solution of the Young-Laplace equation is developed. Two contact geometries--sphere-on-flat and cone-on-flat--are modeled. The calculation results show that the experimentally-observed strong vapor pressure dependence can be explained only when the adsorption isotherm of the vapor on the solid surface is taken into account. The large relative partial pressure dependence mainly comes from the change in the meniscus size due to the presence of the adsorbate layer. Copyright © 2010 Elsevier Inc. All rights reserved.

Pressure Dependence of Insulator-Insulator Contact Charging

NASA Technical Reports Server (NTRS)

Hogue, Michael D.

2005-01-01

The mechanism of insulator-insulator triboelectric (contact) charging is being studied by the Electrostatics and Surface Physics Laboratory at KSC. The hypothesis that surface ion exchange is the primary mechanism is being tested experimentally. A two-phase model based on a small partial pressure of singly charged ions in an ambient ideal gas in equilibrium with a submonolayer adsorbed film will provide predictions about charging as a function Of ion mass, pressure, temperature, and surface adsorption energy. Interactions between ions will be considered in terms of coulombic and screened potential energies. This work is yielding better understanding of the triboelectrification of insulators, which is an important problem in. space exploration technology. The work is also relevant to important industrial processes such as xerography and the application of paints and coatings. Determining a better understanding of the fundamental mechanism of insulator-insulator triboelectrification will hopefully lead to better means of eliminating or at least mitigating its hazards and enhancing its useful applications.

A stabilized element-based finite volume method for poroelastic problems

NASA Astrophysics Data System (ADS)

Honório, Hermínio T.; Maliska, Clovis R.; Ferronato, Massimiliano; Janna, Carlo

2018-07-01

The coupled equations of Biot's poroelasticity, consisting of stress equilibrium and fluid mass balance in deforming porous media, are numerically solved. The governing partial differential equations are discretized by an Element-based Finite Volume Method (EbFVM), which can be used in three dimensional unstructured grids composed of elements of different types. One of the difficulties for solving these equations is the numerical pressure instability that can arise when undrained conditions take place. In this paper, a stabilization technique is developed to overcome this problem by employing an interpolation function for displacements that considers also the pressure gradient effect. The interpolation function is obtained by the so-called Physical Influence Scheme (PIS), typically employed for solving incompressible fluid flows governed by the Navier-Stokes equations. Classical problems with analytical solutions, as well as three-dimensional realistic cases are addressed. The results reveal that the proposed stabilization technique is able to eliminate the spurious pressure instabilities arising under undrained conditions at a low computational cost.

Vaporization of liquid Pb-Li eutectic alloy from 1000K to 1200K - A high temperature mass spectrometric study

NASA Astrophysics Data System (ADS)

Jain, U.; Mukherjee, A.; Dey, G. K.

2017-09-01

Liquid lead-lithium eutectic will be used as a coolant in fusion reactor blanket loop. Vapor pressure of the eutectic is an important parameter to accurately predict its in-loop behavior. Past measurements of vapor pressure of the eutectic relied on indirect methods. In this paper, we report for the first time the in-situ vaporization behavior of the liquid alloy between 1042 and 1176 K by Knudsen effusion mass spectrometry (KEMS). It was seen that the vaporization occurred by independent evaporation of lead and lithium. No complex intermetallic vapor was seen in the mass spectra. The partial pressures and enthalpy of vaporization of Pb and Li were evaluated directly from the measured ion intensities formed from the equilibrium vapor over the alloy. The activity of Li over a temperature range of 1042-1176 K was found to be 4.8 × 10-5 to that of pure Li, indicating its very low activity in the alloy.

The solubility of hydrogen in rhodium, ruthenium, iridium and nickel.

NASA Technical Reports Server (NTRS)

Mclellan, R. B.; Oates, W. A.

1973-01-01

The temperature variation of the solubility of hydrogen in rhodium, ruthenium, iridium, and nickel in equilibrium with H2 gas at 1 atm pressure has been measured by a technique involving saturating the solvent metal with hydrogen, quenching, and analyzing in resultant solid solutions. The solubilities determined are small (atom fraction of H is in the range from 0.0005 to 0.00001, and the results are consistent with the simple quasi-regular model for dilute interstitial solid solutions. The relative partial enthalpy and excess entropy of the dissolved hydrogen atoms have been calculated from the solubility data and compared with well-known correlations between these quantities.

Chemical Principles Revisited: Chemical Equilibrium.

ERIC Educational Resources Information Center

Mickey, Charles D.

1980-01-01

Describes: (1) Law of Mass Action; (2) equilibrium constant and ideal behavior; (3) general form of the equilibrium constant; (4) forward and reverse reactions; (5) factors influencing equilibrium; (6) Le Chatelier's principle; (7) effects of temperature, changing concentration, and pressure on equilibrium; and (8) catalysts and equilibrium. (JN)

Pleural pressure theory revisited: a role for capillary equilibrium

PubMed Central

Caruana-Gauci, Roberto; Manche, Alexander; Gauci, Marilyn; Chetcuti, Stanley; Bertolaccini, Luca

2017-01-01

Background Theories elucidating pleural pressures should explain all observations including the equal and opposite recoil of the chest wall and lungs, the less than expected pleural hydrostatic gradient and its variation at lobar margins, why pleural pressures are negative and how pleural fluid circulation functions. Methods A theoretical model describing equilibrium between buoyancy, hydrostatic forces, and capillary forces is proposed. The capillary equilibrium model described depends on control of pleural fluid volume and protein content, powered by an active pleural pump. Results The interaction between buoyancy forces, hydrostatic pressure and capillary pressure was calculated, and values for pleural thickness and pressure were determined using values for surface tension, contact angle, pleural fluid and lung densities found in the literature. Modelling can explain the issue of the differing hydrostatic vertical pleural pressure gradient at the lobar margins for buoyancy forces between the pleural fluid and the lung floating in the pleural fluid according to Archimedes’ hydrostatic paradox. The capillary equilibrium model satisfies all salient requirements for a pleural pressure model, with negative pressures maximal at the apex, equal and opposite forces in the lung and chest wall, and circulatory pump action. Conclusions This model predicts that pleural effusions cannot occur in emphysema unless concomitant heart failure increases lung density. This model also explains how the non-confluence of the lung with the chest wall (e.g., lobar margins) makes the pleural pressure more negative, and why pleural pressures would be higher after an upper lobectomy compared to a lower lobectomy. Pathological changes in pleural fluid composition and lung density alter the equilibrium between capillarity and buoyancy hydrostatic pressure to promote pleural effusion formation. PMID:28523153

Compressive behavior of fine sand.

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

Martin, Bradley E.; Kabir, Md. E.; Song, Bo

2010-04-01

The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trendsmore » were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.« less

Barium Depletion in the NSTAR Discharge Cathode After 30,000 Hours of Operation

NASA Technical Reports Server (NTRS)

Polk, James E.; Capece, Angela M.; Mikellides, Ioannis G.; Katz, Ira

2010-01-01

Dispenser hollow cathodes rely on a consumable supply of barium released by impregnant materials in the pores of a tungsten matrix to maintain a low work function surface. Examinations of cathode inserts from long duration ion engine tests show deposits of tungsten at the downstream end that appear to block the flow of barium from the interior. In addition, a numerical model of barium transport in the insert plasma indicates that the barium partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant barium-producing reaction, and it was postulated previously that this would suppress barium loss in the upstream part of the insert. New measurements of the depth of barium depletion from a cathode insert operated for 30,352 hours reveal that barium loss is confined to a narrow region near the downstream end, confirming this hypothesis.

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

Ivanov, A. A., E-mail: aai@a5.kiam.ru; Martynov, A. A., E-mail: martynov@a5.kiam.ru; Medvedev, S. Yu., E-mail: medvedev@a5.kiam.ru

In the MHD tokamak plasma theory, the plasma pressure is usually assumed to be isotropic. However, plasma heating by neutral beam injection and RF heating can lead to a strong anisotropy of plasma parameters and rotation of the plasma. The development of MHD equilibrium theory taking into account the plasma inertia and anisotropic pressure began a long time ago, but until now it has not been consistently applied in computational codes for engineering calculations of the plasma equilibrium and evolution in tokamak. This paper contains a detailed derivation of the axisymmetric plasma equilibrium equation in the most general form (withmore » arbitrary rotation and anisotropic pressure) and description of the specialized version of the SPIDER code. The original method of calculation of the equilibrium with an anisotropic pressure and a prescribed rotational transform profile is proposed. Examples of calculations and discussion of the results are also presented.« less

Structural relaxation and thermal conductivity of high-pressure formed, high-density di-n-butyl phthalate glass and pressure induced departures from equilibrium state

NASA Astrophysics Data System (ADS)

Johari, G. P.; Andersson, Ove

2017-06-01

We report a study of structural relaxation of high-density glasses of di-n-butyl phthalate (DBP) by measuring thermal conductivity, κ, under conditions of pressure and temperature (p,T) designed to modify both the vibrational and configurational states of a glass. Various high-density glassy states of DBP were formed by (i) cooling the liquid under a fixed high p and partially depressurizing the glass, (ii) isothermal annealing of the depressurized glass, and (iii) pressurizing the glass formed by cooling the liquid under low p. At a given low p, κ of the glass formed by cooling under high p is higher than that of the glass formed by cooling under low p, and the difference increases as glass formation p is increased. κ of the glass formed under 1 GPa is ˜20% higher at ambient p than κ of the glass formed at ambient p. On heating at low p, κ decreases until the glass to liquid transition range is reached. This is the opposite of the increase in κ observed when a glass formed under a certain p is heated under the same p. At a given high p, κ of the low-density glass formed by cooling at low p is lower than that of the high-density glass formed by cooling at that high p. On heating at high p, κ increases until the glass to liquid transition range is reached. The effects observed are due to a thermally assisted approach toward equilibrium at p different from the glass formation p. In all cases, the density, enthalpy, and entropy would change until the glasses become metastable liquids at a fixed p, thus qualitatively relating κ to variation in these properties.

On axisymmetric resistive magnetohydrodynamic equilibria with flow free of Pfirsch-Schlüter diffusion

NASA Astrophysics Data System (ADS)

Throumoulopoulos, G. N.; Tasso, H.

2003-06-01

The equilibrium of an axisymmetric magnetically confined plasma with anisotropic resistivity and incompressible flows parallel to the magnetic field is investigated within the framework of the magnetohydrodynamic (MHD) theory by keeping the convective flow term in the momentum equation. It turns out that the stationary states are determined by a second-order elliptic partial differential equation for the poloidal magnetic flux function ψ along with a decoupled Bernoulli equation for the pressure identical in form with the respective ideal MHD equations; equilibrium consistent expressions for the resistivities η∥ and η⊥ parallel and perpendicular to the magnetic field are also derived from Ohm's and Faraday's laws. Unlike in the case of stationary states with isotropic resistivity and parallel flows [G. N. Throumoulopoulos and H. Tasso, J. Plasma Phys. 64, 601 (2000)] the equilibrium is compatible with nonvanishing poloidal current densities. Also, although exactly Spitzer resistivities either η∥(ψ) or η⊥(ψ) are not allowed, exact solutions with vanishing poloidal electric fields can be constructed with η∥ and η⊥ profiles compatible with roughly collisional resistivity profiles, i.e., profiles having a minimum close to the magnetic axis, taking very large values on the boundary and such that η⊥>η∥. For equilibria with vanishing flows satisfying the relation (dP/dψ)(dI2/dψ)>0, where P and I are the pressure and the poloidal current functions, the difference η⊥-η∥ for the reversed-field pinch scaling, Bp≈Bt, is nearly two times larger than that for the tokamak scaling, Bp≈0.1Bt (Bp and Bt are the poloidal and toroidal magnetic-field components). The particular resistive equilibrium solutions obtained in the present work, inherently free of—but not inconsistent with—Pfirsch-Schlüter diffusion, indicate that parallel flows might result in a reduction of the diffusion observed in magnetically confined plasmas.

Thermodynamic equilibrium calculations of dimethyl ether steam reforming and dimethyl ether hydrolysis

NASA Astrophysics Data System (ADS)

Semelsberger, Troy A.; Borup, Rodney L.

The production of a hydrogen-rich fuel-cell feed by dimethyl ether (DME) steam reforming was investigated using calculations of thermodynamic equilibrium as a function of steam-to-carbon ratio (0.00-4.00), temperature (100-600 °C), pressure (1-5 atm), and product species. Species considered were acetone, acetylene, carbon dioxide, carbon monoxide, dimethyl ether, ethane, ethanol, ethylene, formaldehyde, formic acid, hydrogen, isopropanol, methane, methanol, methyl-ethyl ether, n-propanol and water. Thermodynamic equilibrium calculations of DME steam reforming indicate complete conversion of dimethyl ether to hydrogen, carbon monoxide and carbon dioxide at temperatures greater than 200 °C and steam-to-carbon ratios greater than 1.25 at atmospheric pressure ( P = 1 atm). Increasing the operating pressure shifts the equilibrium toward the reactants; increasing the pressure from 1 to 5 atm decreases the conversion of dimethyl ether from 99.5 to 76.2%. The trend of thermodynamically stable products in decreasing mole fraction is methane, ethane, isopropyl alcohol, acetone, n-propanol, ethylene, ethanol, methyl-ethyl ether and methanol-formaldehyde, formic acid, and acetylene were not observed. Based on the equilibrium calculations, the optimal processing conditions for dimethyl ether steam reforming occur at a steam-to-carbon ratio of 1.50, a pressure of 1 atm, and a temperature of 200 °C. These thermodynamic equilibrium calculations show dimethyl ether processed with steam will produce hydrogen-rich fuel-cell feeds—with hydrogen concentrations exceeding 70%. The conversion of dimethyl ether via hydrolysis (considering methanol as the only product) is limited by thermodynamic equilibrium. Equilibrium conversion increases with temperature and steam-to-carbon ratio. A maximum dimethyl ether conversion of 62% is achieved at a steam-to-carbon ratio of 5.00 and a processing temperature of 600 °C.

Hydrostatic paradox: experimental verification of pressure equilibrium

NASA Astrophysics Data System (ADS)

Kodejška, Č.; Ganci, S.; Říha, J.; Sedláčková, H.

2017-11-01

This work is focused on the experimental verification of the balance between the atmospheric pressure acting on the sheet of paper, which encloses the cylinder completely or partially filled with water from below, where the hydrostatic pressure of the water column acts against the atmospheric pressure. First of all this paper solves a theoretical analysis of the problem, which is based, firstly, on the equation for isothermal process and, secondly, on the equality of pressures inside and outside the cylinder. From the measured values the confirmation of the theoretical quadratic dependence of the air pressure inside the cylinder on the level of the liquid in the cylinder is obtained, the maximum change in the volume of air within the cylinder occurs for the height of the water column L of one half of the total height of the vessel H. The measurements were made for different diameters of the cylinder and with plates made of different materials located at the bottom of the cylinder to prevent liquid from flowing out of the cylinder. The measured values were subjected to statistical analysis, which demonstrated the validity of the zero hypothesis, i.e. that the measured values are not statistically significantly different from the theoretically calculated ones at the statistical significance level α  =  0.05.

Bridge pressure flow scour for clear water conditions

DOT National Transportation Integrated Search

2009-10-01

The equilibrium scour at a bridge caused by pressure flow with critical approach velocity in clear-water simulation conditions was studied both analytically and experimentally. The flume experiments revealed that (1) the measured equilibrium scour pr...

Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium

NASA Technical Reports Server (NTRS)

Hunt, J. L.; Boney, L. R.

1973-01-01

Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.

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

Simunovic, Srdjan; Piro, Markus H.A.

Thermochimica is a software library that determines a unique combination of phases and their compositions at thermochemical equilibrium. Thermochimica can be used for stand-alone calculations or it can be directly coupled to other codes. This release of the software does not have a graphical user interface (GUI) and it can be executed from the command line or from an Application Programming Interface (API). Also, it is not intended for thermodynamic model development or for constructing phase diagrams. The main purpose of the software is to be directly coupled with a multi-physics code to provide material properties and boundary conditions formore » various physical phenomena. Significant research efforts have been dedicated to enhance computational performance through advanced algorithm development, such as improved estimation techniques and non-linear solvers. Various useful parameters can be provided as output from Thermochimica, such as: determination of which phases are stable at equilibrium, the mass of solution species and phases at equilibrium, mole fractions of solution phase constituents, thermochemical activities (which are related to partial pressures for gaseous species), chemical potentials of solution species and phases, and integral Gibbs energy (referenced relative to standard state). The overall goal is to provide an open source computational tool to enhance the predictive capability of multi-physics codes without significantly impeding computational performance.« less

Equiparatition of energy for turbulent astrophysical fluids: Accounting for the unseen energy in molecular clouds

NASA Technical Reports Server (NTRS)

Zweibel, Ellen G.; Mckee, Christopher F.

1995-01-01

Molecular clouds are observed to be partially supported by turbulent pressure. The kinetic energy of the turbulence is directly measurable, but the potential energy, which consists of magnetic, thermal, and gravitational potential energy, is largly unseen. We have extended previous results on equipartition between kinetic and potential energy to show that it is likely to be a very good approximation in molecular clouds. We have used two separate approaches to demonstrate this result: For small-amplitude perturbations of a static equilibrium, we have used the energy principle analysis of Bernstein et al. (1958); this derivation applies to perturbations of arbitary wavelength. To treat perturbations of a nonstatic equilibrium, we have used the Lagrangian analysis of Dewar (1970); this analysis applies only to short-wavelength perturbations. Both analysis assume conservation of energy. Wave damping has only a small effect on equipartition if the wave frequency is small compared to the neutral-ion collision frequency; for the particular case we considered, radiative losses have no effect on equipartition. These results are then incorporated in a simple way into analyses of cloud equilibrium and global stability. We discuss the effect of Alfvenic turbulence on the Jeans mass and show that it has little effect on the magnetic critical mass.

Study Program to Develop and Evaluate Die and Container Materials for the Growth of Silicon Ribbons

NASA Technical Reports Server (NTRS)

Ounby, P. D.; Yu, B. B.; Barsoum, M. W.

1979-01-01

The completion of a major hardware delivery milestone was accomplished with the delivery of three CNTD Si3N4 coated hot pressed Si3N4 crucibles. A limited characterization of the coating was performed at MRL prior to delivery. The coatings were fine grained alpha - Si3N4. It was determined that a two piece die design is required. The importance of the role of oxygen in influencing the attack of the CNTD materials by molten silicon was demonstrated. The stability is greatly enhanced by maintaining the oxygen partial pressure near or below the Si + O2 = SiO2 equilibrium.

Models of the Earth's Core.

PubMed

Stevenson, D J

1981-11-06

Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with the following properties. Core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and laboratory data.

Continuous-flow free acid monitoring method and system

DOEpatents

Strain, J.E.; Ross, H.H.

1980-01-11

A free acid monitoring method and apparatus is provided for continuously measuring the excess acid present in a process stream. The disclosed monitoring system and method is based on the relationship of the partial pressure ratio of water and acid in equilibrium with an acid solution at constant temperature. A portion of the process stream is pumped into and flows through the monitor under the influence of gravity and back to the process stream. A continuous flowing sample is vaporized at a constant temperature and the vapor is subsequently condensed. Conductivity measurements of the condensate produces a nonlinear response function from which the free acid molarity of the sample process stream is determined.

Continuous-flow free acid monitoring method and system

DOEpatents

Strain, James E.; Ross, Harley H.

1981-01-01

A free acid monitoring method and apparatus is provided for continuously measuring the excess acid present in a process stream. The disclosed monitoring system and method is based on the relationship of the partial pressure ratio of water and acid in equilibrium with an acid solution at constant temperature. A portion of the process stream is pumped into and flows through the monitor under the influence of gravity and back to the process stream. A continuous flowing sample is vaporized at a constant temperature and the vapor is subsequently condensed. Conductivity measurements of the condensate produces a nonlinear response function from which the free acid molarity of the sample process stream is determined.

Plasma equilibrium with fast ion orbit width, pressure anisotropy, and toroidal flow effects

DOE PAGES

Gorelenkov, Nikolai N.; Zakharov, Leonid E.

2018-04-27

Here, we formulate the problem of tokamak plasma equilibrium including the toroidal flow and fast ion (or energetic particle, EP) pressure anisotropy and the finite drift orbit width (FOW) effects. The problem is formulated via the standard Grad-Shafranov equation (GShE) amended by the solvability condition which imposes physical constraints on allowed spacial dependencies of the anisotropic pressure. The GShE problem employs the pressure coupling scheme and includes the dominant diagonal terms and non-diagonal corrections to the standard pressure tensor. The anisotropic tensor elements are obtained via the distribution function represented in the factorized form via the constants of motion. Consideredmore » effects on the plasma equilibrium are estimated analytically, if possible, to understand their importance for GShE tokamak plasma problem.« less

Plasma equilibrium with fast ion orbit width, pressure anisotropy, and toroidal flow effects

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

Gorelenkov, Nikolai N.; Zakharov, Leonid E.

Here, we formulate the problem of tokamak plasma equilibrium including the toroidal flow and fast ion (or energetic particle, EP) pressure anisotropy and the finite drift orbit width (FOW) effects. The problem is formulated via the standard Grad-Shafranov equation (GShE) amended by the solvability condition which imposes physical constraints on allowed spacial dependencies of the anisotropic pressure. The GShE problem employs the pressure coupling scheme and includes the dominant diagonal terms and non-diagonal corrections to the standard pressure tensor. The anisotropic tensor elements are obtained via the distribution function represented in the factorized form via the constants of motion. Consideredmore » effects on the plasma equilibrium are estimated analytically, if possible, to understand their importance for GShE tokamak plasma problem.« less

A new endstation at the Swiss Light Source for ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy measurements of liquid solutions.

PubMed

Brown, Matthew A; Redondo, Amaia Beloqui; Jordan, Inga; Duyckaerts, Nicolas; Lee, Ming-Tao; Ammann, Markus; Nolting, Frithjof; Kleibert, Armin; Huthwelker, Thomas; Müächler, Jean-Pierre; Birrer, Mario; Honegger, Juri; Wetter, Reto; Wörner, Hans Jakob; van Bokhoven, Jeroen A

2013-07-01

A new liquid microjet endstation designed for ultraviolet (UPS) and X-ray (XPS) photoelectron, and partial electron yield X-ray absorption (XAS) spectroscopies at the Swiss Light Source is presented. The new endstation, which is based on a Scienta HiPP-2 R4000 electron spectrometer, is the first liquid microjet endstation capable of operating in vacuum and in ambient pressures up to the equilibrium vapor pressure of liquid water at room temperature. In addition, the Scienta HiPP-2 R4000 energy analyzer of this new endstation allows for XPS measurements up to 7000 eV electron kinetic energy that will enable electronic structure measurements of bulk solutions and buried interfaces from liquid microjet samples. The endstation is designed to operate at the soft X-ray SIM beamline and at the tender X-ray Phoenix beamline. The endstation can also be operated using a Scienta 5 K ultraviolet helium lamp for dedicated UPS measurements at the vapor-liquid interface using either He I or He II α lines. The design concept, first results from UPS, soft X-ray XPS, and partial electron yield XAS measurements, and an outlook to the potential of this endstation are presented.

Pupils' Pressure Models and Their Implications for Instruction.

ERIC Educational Resources Information Center

Kariotoglou, P.; Psillos, D.

1993-01-01

Discusses a study designed to investigate pupils' conceptions about fluids and particularly liquids in equilibrium, with reference to the concept of pressure. Based upon the results obtained, several mental models of how pupils understand liquids in equilibrium were proposed. (ZWH)

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions.

PubMed

Hu, Ruien; Crawshaw, John

2017-06-06

A rheometer system to measure the rheology of crude oil in equilibrium with carbon dioxide (CO2) at high temperatures and pressures is described. The system comprises a high-pressure rheometer which is connected to a circulation loop. The rheometer has a rotational flow-through measurement cell with two alternative geometries: coaxial cylinder and double gap. The circulation loop contains a mixer, to bring the crude oil sample into equilibrium with CO2, and a gear pump that transports the mixture from the mixer to the rheometer and recycles it back to the mixer. The CO2 and crude oil are brought to equilibrium by stirring and circulation and the rheology of the saturated mixture is measured by the rheometer. The system is used to measure the rheological properties of Zuata crude oil (and its toluene dilution) in equilibrium with CO2 at elevated pressures up to 220 bar and a temperature of 50 °C. The results show that CO2 addition changes the oil rheology significantly, initially reducing the viscosity as the CO2 pressure is increased and then increasing the viscosity above a threshold pressure. The non-Newtonian response of the crude is also seen to change with the addition of CO2.

The influence of pressure relaxation on the structure of an axial vortex

NASA Astrophysics Data System (ADS)

Ash, Robert L.; Zardadkhan, Irfan; Zuckerwar, Allan J.

2011-07-01

Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and published axial vortex experiments have been employed to estimate the pressure relaxation coefficient in water. Non-equilibrium pressure gradient forces have been shown to balance the viscous stresses in the vortex core region, and the predicted pressure deficits that result from this non-equilibrium balance can be substantially larger than the pressure deficits predicted using a Bernoulli equation approach. Previously reported pressure deficit distributions for dust devils and tornados have been employed to validate the non-equilibrium pressure deficit predictions.

Studies on the phase diagram of Pb-Fe-O system and standard molar Gibbs energy of formation of 'PbFe5O8.5' and Pb2Fe2O5

NASA Astrophysics Data System (ADS)

Sahu, Sulata Kumari; Ganesan, Rajesh; Gnanasekaran, T.

2012-07-01

Partial phase diagram of Pb-Fe-O system has been established by phase equilibration studies over a wide temperature range coupled with high temperature solid electrolyte based emf cells. Ternary oxides are found to coexist with liquid lead only at temperatures above 900 K. At temperatures below 900 K, iron oxides coexist with liquid lead. Standard molar Gibbs energy of formation of ternary oxides 'PbFe5O8.5' and Pb2Fe2O5 were determined by measuring equilibrium oxygen partial pressures over relevant phase fields using emf cells and are given by the following expressions: ΔfGmo 'PbFeO'±1.0(kJ mol)=-2208.1+0.6677(T/K) (917⩽T/K⩽1117) ΔfGmo PbFeO±0.8(kJ mol)=-1178.4+0.3724(T/K) (1050⩽T/K⩽1131) .

Thermal/Pyrolysis Gas Flow Analysis of Carbon Phenolic Material

NASA Technical Reports Server (NTRS)

Clayton, J. Louie

2001-01-01

Provided in this study are predicted in-depth temperature and pyrolysis gas pressure distributions for carbon phenolic materials that are externally heated with a laser source. Governing equations, numerical techniques and comparisons to measured temperature data are also presented. Surface thermochemical conditions were determined using the Aerotherm Chemical Equilibrium (ACE) program. Surface heating simulation used facility calibrated radiative and convective flux levels. Temperatures and pyrolysis gas pressures are predicted using an upgraded form of the SINDA/CMA program that was developed by NASA during the Solid Propulsion Integrity Program (SPIP). Multispecie mass balance, tracking of condensable vapors, high heat rate kinetics, real gas compressibility and reduced mixture viscosity's have been added to the algorithm. In general, surface and in-depth temperature comparisons are very good. Specie partial pressures calculations show that a saturated water-vapor mixture is the main contributor to peak in-depth total pressure. Further, for most of the cases studied, the water-vapor mixture is driven near the critical point and is believed to significantly increase the local heat capacity of the composite material. This phenomenon if not accounted for in analysis models may lead to an over prediction in temperature response in charring regions of the material.

Partially wrong? Partial equilibrium and the economic analysis of public health emergencies of international concern.

PubMed

Beutels, P; Edmunds, W J; Smith, R D

2008-11-01

We argue that traditional health economic analysis is ill-equipped to estimate the cost effectiveness and cost benefit of interventions that aim at controlling and/or preventing public health emergencies of international concern (such as pandemic influenza or severe acute respiratory syndrome). The implicit assumption of partial equilibrium within both the health sector itself and--if a wider perspective is adopted--the economy as a whole would be violated by such emergencies. We propose an alternative, with the specific aim of accounting for the behavioural changes and capacity problems that are expected to occur when such an outbreak strikes. Copyright (c) 2008 John Wiley & Sons, Ltd.

New Stagnation Arc Jet Model Design for Testing ADEPT 3-D Carbon Cloth

NASA Technical Reports Server (NTRS)

Beck, R.; Chen, Y.-K.; Wercinski, P.; Agrawal, P.; Chavez-Garcia, J.

2017-01-01

The ADEPT concept has been considered as an entry, descent and landing system to enable Human Mars class missions. Ground rules for the Mars studies required aerocapture, orbit, and then entry. The design utilizes a 3-D woven carbon cloth fabric as both heatshield and primary structure and design guidelines required 6 layers remaining after all entry events. The peak heating predicted for the ADEPT carbon cloth was 35 Wcm2 and resulting temperatures were predicted to be 1400K. Predictions for carbon mass loss were performed using equilibrium thermochemistry, which is only accurate for T2000K. Carbon oxidation is kinetically controlled at T2000K, and mass loss drops off considerably from equilibrium values. Design of the cloth thickness and mass would be significantly reduced if kinetics were considered. This effort was to design a stagnation test article design that could be used in the AHF with varying levels of oxygen where the results could be used to develop an engineering model to describe the recession rate of the carbon as a function of the partial pressure of monotomic oxygen.

The influence of crystallography and kinetics on phengite breakdown reactions in a low-pressure metamorphic aureole

NASA Astrophysics Data System (ADS)

Worden, R. H.; Droop, G. T. R.; Champness, P. E.

1992-04-01

A natural example of phengite that had undergone partial thermal decomposition at a pressure of about 0.5 kbar and a temperature of about 680° C in a contact aureole was exmined in the transmission electron microscope (TEM). Partially pseudomorphed phengites were found to consist of combinations of phengite, biotite, K-feldspar, mullite, sillimanite, spinel and cordierite. Different areas within individual, partially pseudomorphed, phengite grains show various degrees of reaction and different reaction products; the cores are the least reacted and the margins have reacted most. In the cores the assemblage Al-, Mg-enriched phengite+biotite +K-feldspar+mullite±spinel has formed, whereas the assemblage K-feldspar+mullite+sillimanite+spinel +biotite+cordierite has formed at the edges. According to our thermodynamic calculations, the breakdown of phengite should have produced cordierite+spinel +corundum+K-feldspar in regions isolated from the influx of SiO2 and cordierite+andalusite+quartz+K-feldspar in regions near the edge of the grains that were essentially saturated with SiO2. Chemical equilibrium was not achieved in any part of the partially pseudomorphed phengites on a micron scale or larger. Breakdown theoretically should have been complete by about 550° C; the reaction temperature was overstepped by at least 130° C for 20 25 years. The variations in the degree and type of reaction are probably due partly to the availability of suitable nucleation sites in different regions, partly to the need to remove H2O from reaction sites and partly to the influence of SiO2, which diffused into the grains during metamorphism. The presence of SiO2 lowers the equilibrium temperatures. Thus there is a higher driving force for breakdown near the grain boundaries than in the cores. Most of the products show an orientation relationship with the parent phengite and have consistent habit planes; they have their closest-packed planes and closest-packed directions parallel to one another and to those of phengite. Such relationships minimize the strain and surface energies at nucleation and favour most rapid nucleation and growth of the reaction products. The great structural similarity of biotite to phengite resulted in its having the highest rate of nucleation and growth of any product and it occurred in all areas of the phengite pseudomorphs studied. Mullite and sillimanite were produced metastably. Mullite has more rapid nucleation kinetics than other aluminosilicates because it is structurally disordered. Sillimanite formed rather than andalusite in regions of the partially pseudomorphed phengites where the reaction reached an advanced stage, because the reaction from phengite to andalusite requires an energetically unfavourable change in aluminium co-ordination state.

High-pressure studies of aggregation of recombinant human interleukin-1 receptor antagonist: Thermodynamics, kinetics, and application to accelerated formulation studies

PubMed Central

Seefeldt, Matthew B.; Kim, Yong-Sung; Tolley, Kevin P.; Seely, Jim; Carpenter, John F.; Randolph, Theodore W.

2005-01-01

Recombinant human interleukin-1 receptor antagonist (IL-1ra) in aqueous solutions unfolds and aggregates when subjected to hydrostatic pressures greater than about 180 MPa. This study examined the mechanism and thermodynamics of pressure-induced unfolding and aggregation of IL-1ra. The activation free energy for growth of aggregates (ΔG∓aggregation) was found to be 37 ± 3 kJ/mol, whereas the activation volume (ΔV∓aggregation) was −120 ± 20 mL/mol. These values compare closely with equilibrium values for denaturation: The free energy for denaturation, ΔGdenaturation, was 20 ± 5 kJ/mol, whereas the partial specific volume change for denaturation, ΔVdenaturation, was −110 ± 30 mL/mol. When IL-1ra begins to denature at pressures near 140 MPa, cysteines that are normally buried in the native state become exposed. Under oxidizing conditions, this results in the formation of covalently cross-linked aggregates containing nonnative, intermolecular disulfide bonds. The apparent activation free energy for nucleation of aggregates, ΔG∓nuc, was 42 ± 4 kJ/mol, and the activation volume for nucleation, ΔV∓nuc,was −175 ± 37 mL/mol, suggesting that a highly solvent-exposed conformation is needed for nucleation. We hypothesize that the large specific volume of IL-1ra, 0.752 ± 0.004 mL/g, coupled with its relatively low conformational stability, leads to its susceptibility to denaturation at relatively low pressures. The positive partial specific adiabatic compressibility of IL-1ra, 4.5 ± 0.7 ± 10−12 cm2/dyn, suggests that a significant component of the ΔVdenaturation is attributable to the elimination of solvent-free cavities. Lastly, we propose that hydrostatic pressure is a useful variable to conduct accelerated formulation studies of therapeutic proteins. PMID:16081653

A real time study of the human equilibrium using an instrumented insole with 3 pressure sensors.

PubMed

Abou Ghaida, Hussein; Mottet, Serge; Goujon, Jean-Marc

2014-01-01

The present work deals with the study of the human equilibrium using an ambulatory e-health system. One of the point on which we focus is the fall risk, when losing equilibrium control. A specific postural learning model is presented, and an ambulatory instrumented insole is developed using 3 pressures sensors per foot, in order to determine the real-time displacement and the velocity of the centre of pressure (CoP). The increase of these parameters signals a loss of physiological sensation, usually of vision or of the inner ear. The results are compared to those obtained from classical more complex systems.

A finite difference scheme for the equilibrium equations of elastic bodies

NASA Technical Reports Server (NTRS)

Phillips, T. N.; Rose, M. E.

1984-01-01

A compact difference scheme is described for treating the first-order system of partial differential equations which describe the equilibrium equations of an elastic body. An algebraic simplification enables the solution to be obtained by standard direct or iterative techniques.

High vacuum measurements and calibrations, molecular flow fluid transient effects

DOE PAGES

Leishear, Robert A.; Gavalas, Nickolas A.

2015-04-29

High vacuum pressure measurements and calibrations below 1 × 10 -8 Torr are problematic. Specifically, measurement accuracies change drastically for vacuum gauges when pressures are suddenly lowered in vacuum systems. How can gauges perform like this? A brief system description is first required to answer this question. Calibrations were performed using a vacuum calibration chamber with attached vacuum gauges. To control chamber pressures, vacuum pumps decreased the chamber pressure while nitrogen tanks increased the chamber pressure. By balancing these opposing pressures, equilibrium in the chamber was maintained at selected set point pressures to perform calibrations. When pressures were suddenly decreasedmore » during set point adjustments, a sudden rush of gas from the chamber also caused a surge of gas from the gauges to decrease the pressures in those gauges. Gauge pressures did not return to equilibrium as fast as chamber pressures due to the sparse distribution of gas molecules in the system. This disparity in the rate of pressure changes caused the pressures in different gauges to be different than expected. This discovery was experimentally proven to show that different gauge designs return to equilibrium at different rates, and that gauge accuracies vary for different gauge designs due to fluid transients in molecular flow.« less

Thin film devices used as oxygen partial pressure sensors

NASA Technical Reports Server (NTRS)

Canady, K. S.; Wortman, J. J.

1970-01-01

Electrical conductivity of zinc oxide films to be used in an oxygen partial pressure sensor is measured as a function of temperature, oxygen partial pressure, and other atmospheric constituents. Time response following partial pressure changes is studied as a function of temperature and environmental changes.

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.

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model.

PubMed

Park, Marcelo; Mendes, Pedro Vitale; Costa, Eduardo Leite Vieira; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Azevedo, Luciano Cesar Pontes

2016-01-01

The aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure. The factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested. Oxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL). In conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin.

Imaging the equilibrium state and magnetization dynamics of partially built hard disk write heads

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

Valkass, R. A. J., E-mail: rajv202@ex.ac.uk; Yu, W.; Shelford, L. R.

Four different designs of partially built hard disk write heads with a yoke comprising four repeats of NiFe (1 nm)/CoFe (50 nm) were studied by both x-ray photoemission electron microscopy (XPEEM) and time-resolved scanning Kerr microscopy (TRSKM). These techniques were used to investigate the static equilibrium domain configuration and the magnetodynamic response across the entire structure, respectively. Simulations and previous TRSKM studies have made proposals for the equilibrium domain configuration of similar structures, but no direct observation of the equilibrium state of the writers has yet been made. In this study, static XPEEM images of the equilibrium state of writer structures weremore » acquired using x-ray magnetic circular dichroism as the contrast mechanism. These images suggest that the crystalline anisotropy dominates the equilibrium state domain configuration, but competition with shape anisotropy ultimately determines the stability of the equilibrium state. Dynamic TRSKM images were acquired from nominally identical devices. These images suggest that a longer confluence region may hinder flux conduction from the yoke into the pole tip: the shorter confluence region exhibits clear flux beaming along the symmetry axis, whereas the longer confluence region causes flux to conduct along one edge of the writer. The observed variations in dynamic response agree well with the differences in the equilibrium magnetization configuration visible in the XPEEM images, confirming that minor variations in the geometric design of the writer structure can have significant effects on the process of flux beaming.« less

Vapor-liquid-solid growth of <110> silicon nanowire arrays

NASA Astrophysics Data System (ADS)

Eichfeld, Sarah M.; Hainey, Mel F.; Shen, Haoting; Kendrick, Chito E.; Fucinato, Emily A.; Yim, Joanne; Black, Marcie R.; Redwing, Joan M.

2013-09-01

The epitaxial growth of <110> silicon nanowires on (110) Si substrates by the vapor-liquid-solid growth process was investigated using SiCl4 as the source gas. A high percentage of <110> nanowires was obtained at high temperatures and reduced SiCl4 partial pressures. Transmission electron microscopy characterization of the <110> Si nanowires revealed symmetric V-shaped {111} facets at the tip and large {111} facets on the sidewalls of the nanowires. The symmetric {111} tip faceting was explained as arising from low catalyst supersaturation during growth which is expected to occur given the near-equilibrium nature of the SiCl4 process. The predominance of {111} facets obtained under these conditions promotes the growth of <110> SiNWs.

Interpretation and modelling of fission product Ba and Mo releases from fuel

NASA Astrophysics Data System (ADS)

Brillant, G.

2010-02-01

The release mechanisms of two fission products (namely barium and molybdenum) in severe accident conditions are studied using the VERCORS experimental observations. Barium is observed to be mostly released under reducing conditions while molybdenum release is most observed under oxidizing conditions. As well, the volatility of some precipitates in fuel is evaluated by thermodynamic equilibrium calculations. The polymeric species (MoO 3) n are calculated to largely contribute to molybdenum partial pressure and barium volatility is greatly enhanced if the gas atmosphere is reducing. Analytical models of fission product release from fuel are proposed for barium and molybdenum. Finally, these models have been integrated in the ASTEC/ELSA code and validation calculations have been performed on several experimental tests.

Models of the earth's core

NASA Technical Reports Server (NTRS)

Stevenson, D. J.

1981-01-01

Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with five basic properties. These are that core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and labroatory data.

PROM7: 1D modeler of solar filaments or prominences

NASA Astrophysics Data System (ADS)

Gouttebroze, P.

2018-05-01

PROM7 is an update of PROM4 (ascl:1306.004) and computes simple models of solar prominences and filaments using Partial Radiative Distribution (PRD). The models consist of plane-parallel slabs standing vertically above the solar surface. Each model is defined by 5 parameters: temperature, density, geometrical thickness, microturbulent velocity and height above the solar surface. It solves the equations of radiative transfer, statistical equilibrium, ionization and pressure equilibria, and computes electron and hydrogen level population and hydrogen line profiles. Moreover, the code treats calcium atom which is reduced to 3 ionization states (Ca I, Ca II, CA III). Ca II ion has 5 levels which are useful for computing 2 resonance lines (H and K) and infrared triplet (to 8500 A).

Point Defect Distributions in ZnSe Crystals: Effects of Gravity Vector Orientation During Physical Vapor Transport Growth

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Feth, S.; Hirschfeld, D.; Smith, T. M.; Wang, Ling Jun; Volz, M. P.; Lehoczky, S. L.

1999-01-01

ZnSe crystals were grown by the physical vapor transport technique under horizontal and vertical (stabilized and destabilized) configurations. Secondary ion mass spectroscopy and photoluminescence measurements were performed on the grown ZnSe samples to map the distributions of [Si], [Fe], [Cu], [Al] and [Li or Na] impurities as well as Zn vacancy, [V (sub Zn)]. Annealings of ZnSe under controlled Zn pressures were studied to correlate the measured photoluminescence emission intensity to the equilibrium Zn partial pressure. In the horizontal grown crystals the segregations of [Si], [Fe], [Al] and [V (sub Zn)] were observed along the gravity vector direction whereas in the vertically stabilized grown crystal the segregation of these point defects was radially symmetrical. No apparent pattern was observed on the measured distributions in the vertically destabilized grown crystal. The observed segregations in the three growth configurations were interpreted based on the possible buoyancy-driven convection in the vapor phase.

A Tightly Coupled Non-Equilibrium Magneto-Hydrodynamic Model for Inductively Coupled RF Plasmas

DTIC Science & Technology

2016-02-29

development a tightly coupled magneto-hydrodynamic model for Inductively Coupled Radio- Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE...for Inductively Coupled Radio-Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State... thermodynamic variable. This choice allows one to hide the non-linearity of the gas (total) thermal conductivity κ and can partially alle- 2 viate numerical

A Study of Interactions between Mixing and Chemical Reaction Using the Rate-Controlled Constrained-Equilibrium Method

NASA Astrophysics Data System (ADS)

Hadi, Fatemeh; Janbozorgi, Mohammad; Sheikhi, M. Reza H.; Metghalchi, Hameed

2016-10-01

The rate-controlled constrained-equilibrium (RCCE) method is employed to study the interactions between mixing and chemical reaction. Considering that mixing can influence the RCCE state, the key objective is to assess the accuracy and numerical performance of the method in simulations involving both reaction and mixing. The RCCE formulation includes rate equations for constraint potentials, density and temperature, which allows taking account of mixing alongside chemical reaction without splitting. The RCCE is a dimension reduction method for chemical kinetics based on thermodynamics laws. It describes the time evolution of reacting systems using a series of constrained-equilibrium states determined by RCCE constraints. The full chemical composition at each state is obtained by maximizing the entropy subject to the instantaneous values of the constraints. The RCCE is applied to a spatially homogeneous constant pressure partially stirred reactor (PaSR) involving methane combustion in oxygen. Simulations are carried out over a wide range of initial temperatures and equivalence ratios. The chemical kinetics, comprised of 29 species and 133 reaction steps, is represented by 12 RCCE constraints. The RCCE predictions are compared with those obtained by direct integration of the same kinetics, termed detailed kinetics model (DKM). The RCCE shows accurate prediction of combustion in PaSR with different mixing intensities. The method also demonstrates reduced numerical stiffness and overall computational cost compared to DKM.

Determining osmotic pressure of drug solutions by air humidity in equilibrium method.

PubMed

Zhan, Xiancheng; Li, Hui; Yu, Lan; Wei, Guocui; Li, Chengrong

2014-06-01

To establish a new osmotic pressure measuring method with a wide measuring range. The osmotic pressure of drug solutions is determined by measuring the relative air humidity in equilibrium with the solution. The freezing point osmometry is used as a control. The data obtained by the proposed method are comparable to those by the control method, and the measuring range of the proposed method is significantly wider than that of the control method. The proposed method is performed in an isothermal and equilibrium state, so it overcomes the defects of the freezing point and dew point osmometries which result from the heterothermal process in the measurement, and therefore is not limited to diluted solutions.

21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a catheter-tip...

21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a catheter-tip...

21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a catheter-tip...

21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a catheter-tip...

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model

PubMed Central

Park, Marcelo; Mendes, Pedro Vitale; Costa, Eduardo Leite Vieira; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Azevedo, Luciano Cesar Pontes

2016-01-01

Objective The aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure. Methods The factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested. Results Oxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL). Conclusion In conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin. PMID:27096671

Low Pressure-High Temperature Metamorphism and the Advection of Heat to the Continental Crust: A Case Study from Northwest New Guinea

NASA Astrophysics Data System (ADS)

Jost, B.; Webb, M.; White, L. T.

2017-12-01

In northwest New Guinea, Palaeozoic basement rocks forming part of the northern margin of the Australian continent are exposed in a rugged mountain range. This remote and understudied region provides a unique window into the complex Palaeozoic evolution and tectonic history of this region, which we help unravel with new field, petrographic, geochemical, and geochronological data. The basement rocks consist of extensive meta-turbidites that were subject to low pressure-high temperature metamorphism along their eastern margin. They are cross-cut by predominantly acidic granitoids. U-Pb zircon dating reveals that these granitoids intruded in three episodes in the Devonian-Carboniferous, the Carboniferous, and the Triassic. The first episode has not previously been reported in the region. The granitoids are strongly peraluminous, suggesting that partial melting of the meta-sedimentary country rock contributed to their petrogenesis (S-type). The occurrence and character of country rock xenoliths and migmatites supports this interpretation. Equilibrium thermodynamic modelling of the metapelites and the migmatites indicates that a substantial amount of heat was added to the lower and middle crust to cause partial melting and regional metamorphism at relatively low pressure. We propose repeated intrusion of hot magma as the mechanism responsible for advecting the necessary heat from the mantle. This likely occurred in an active continental margin setting during the Devonian-Carboniferous and the Triassic, possibly separated by an interval of magmatic quiescence during most of the Permian. New biostratigraphic and low-temperature thermochronological data reveal very recent Pliocene-Pleistocene uplift and unroofing of these basement rocks.

Grand Canonical Investigation of the Quasi Liquid Layer of Ice: Is It Liquid?

PubMed

Pickering, Ignacio; Paleico, Martin; Sirkin, Yamila A Perez; Scherlis, Damian A; Factorovich, Matías H

2018-05-10

In this study, the solid-vapor equilibrium and the quasi liquid layer (QLL) of ice Ih exposing the basal and primary prismatic faces were explored by means of grand canonical molecular dynamics simulations with the monatomic mW potential. For this model, the solid-vapor equilibrium was found to follow the Clausius-Clapeyron relation in the range examined, from 250 to 270 K, with a Δ H sub of 50 kJ/mol in excellent agreement with the experimental value. The phase diagram of the mW model was constructed for the low pressure region around the triple point. The analysis of the crystallization dynamics during condensation and evaporation revealed that, for the basal face, both processes are highly activated, and in particular cubic ice is formed during condensation, producing stacking-disordered ice. The basal and primary prismatic surfaces of ice Ih were investigated at different temperatures and at their corresponding equilibrium vapor pressures. Our results show that the region known as QLL can be interpreted as the outermost layers of the solid where a partial melting takes place. Solid islands in the nanometer length scale are surrounded by interconnected liquid areas, generating a bidimensional nanophase segregation that spans throughout the entire width of the outermost layer even at 250 K. Two approaches were adopted to quantify the QLL and discussed in light of their ability to reflect this nanophase segregation phenomena. Our results in the μVT ensemble were compared with NPT and NVT simulations for two system sizes. No significant differences were found between the results as a consequence of model system size or of the working ensemble. Nevertheless, certain advantages of performing μVT simulations in order to reproduce the experimental situation are highlighted. On the one hand, the QLL thickness measured out of equilibrium might be affected because of crystallization being slower than condensation. On the other, preliminary simulations of AFM indentation experiments show that the tip can induce capillary condensation over the ice surface, enlarging the apparent QLL.

21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid in...

21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid in...

21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid in...

21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid in...

21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid in...

The Ferguson principle and an analysis of biological activity of gases and vapors.

PubMed

Abraham, M H; Nielsen, G D; Alarie, Y

1994-05-01

The Ferguson principle, that Pnar/PO (Pnar is the partial pressure of a series of compounds giving rise to a particular effect on a given system by a physical mechanism, and PO is the saturated vapor pressure of the liquid narcotic) is constant for a series of nonreactive narcotics or toxicants in a given system, is examined and shown to have no thermodynamic basis, contrary to the position of Brink and Posternak. Conditions under which Pnar/PO might be expected to be roughly constant, as an empirical observation, are set out and it is shown that such an observation is consistent with a receptor area in which the liquid narcotic solubilities are roughly constant. An interpretation of relationships between agonist descriptors and biological effects is carried out with three simple biological models. It is shown that the biological potency of nonreactive gases and vapors can be controlled either by an equilibrium between the agonist in the gas phase and the agonist in a receptor or by an equilibrium between the agonist in the gas phase and the agonist in a receptor phase. It is further shown that with the solvation equation of Abraham, solvents can be chosen that mimic the chemical properties of the receptor or receptor phase. For the example of upper respiratory tract irritation of male Swiss OF1 mice, such solvents include N-formylmorpholine, a trialkylphosphate, and wet octanol, but not water itself.

A TEM study of disequilibrium plagioclase breakdown at high pressure: the role of infiltrating fluid

NASA Astrophysics Data System (ADS)

Wayte, Gavin J.; Worden, Richard H.; Rubie, David C.; Droop, Giles T. R.

1989-04-01

High-pressure metamorphism (˜600° C, ˜20 kbar) of the Allalin Gabbro (Western Alps) resulted in the breakdown of plagioclase (˜An63) to fine-grained zoisite, jadeite, kyanite and quartz. In rare cases this reaction failed to reach completion. The resulting textures of partial reaction have been studied by transmission and analytical electron microscopy. In localised regions of a plagioclase crystal where the extent of reaction is <10%, only zoisite developed and the orientation relationship 1 410_2004_Article_BF00372216_TeX2GIFE1.gif left( {100} right)_{{text{Zo}}} //left( {101} right)_{{text{P1}}} and 1 410_2004_Article_BF00372216_TeX2GIFE2.gif left( {012} right)_{{text{Zo}}} //left( {010} right)_{{text{P1}}} is frequently present. In regions where 10 50% of plagioclase has transformed, the reaction plagioclase+H2O→zoisite+kyanite+quartz +(NaSiCa-1Al-1)pl has occurred. The systematic orientation relationship between plagioclase and zoisite is absent at ≥50% transformation. Complete breakdown of plagioclase occurred in localized micron-scale domains by the reaction plagioclase+H2O→zoisite+jadeite+kyanite+quartz and the reaction products are variably orientated with respect to each other. Incomplete reaction, together with the concentration of reaction products around cracks in original plagioclase grains, suggests that extent of reaction was controlled primarily by the availability of H2O. The textural observations are interpreted in terms of two possible disequilibrium reaction models. (1) Plagioclase persists metastably with its original igneous composition to a pressure > 17 kbar at 600° C. Reaction to the equilibrium assemblage then develops adjacent to cracks in response to the presence of aqueous fluid. At intracrystalline sites, only partial reaction occurs because Jadeite, and sometimes kyanite and quartz, fail to nucleate for kinetic reasons. (2) Localized regions of a plagioclase crystal partially equilibrate at several stages during the increase of pressure (˜9 17 kbar at 600° C), possibly due to discrete episodes of fluid infiltration. In both these models, the extent of reaction may be limited by NaSi-CaAl interdiffusion in plagioclase.

Defect chemistry and characterization of Hg sub 1x Cd sub x Te

NASA Technical Reports Server (NTRS)

Vydyanath, H. R.

1982-01-01

Single crystal samples of undoped and doped Hg sub 1-x Cd sub x Te were annealed at varying temperatures and partial pressures of Hg. Hall effect and mobility measurements were carried out on these samples after quenching to room temperature. Based on the variation of the carrier concentration and the carrier mobility as a function of the partial pressure of Hg temperature, and dopant concentration, defect models were established for the doped and the undoped crystals. These models indicate that the native acceptor defects in both Hg0.8Cd0.2Te and Hg0.6Cd0.4Te doubly ionized and the native donor defects are negligible in concentration, implying that p to n conversion in these alloys occurs due only to residual donors. Incorporation mechanism of copper, indium, iodine, and phosphorus were investigated. A large concentration of indium is found to be paired with the native acceptor defects. Results on crystals doped with phosphorus indicate that phosphorus behaves amphoterically, acting as a donor on Hg lattice sites and as an acceptor intersitially on Te lattice sites. A majority of the phosphorus is found to be present as neutral species formed from the pairing reaction between phosphorus on Hg lattice sites and phosphorus in interstitial sites. Equilibrium constants for the intrinsic excitation reaction, as well as for the incorporation of the different dopants and the native acceptor defects were established.

Geochemical Effects of Millimolar Hydrogen Concentrations in Groundwater: An Experimental Study in the Context of Subsurface Hydrogen Storage.

PubMed

Berta, Marton; Dethlefsen, Frank; Ebert, Markus; Schäfer, Dirk; Dahmke, Andreas

2018-04-17

Hydrogen storage in geological formations is one of the most promising technologies for balancing major fluctuations between energy supply from renewable energy plants and energy demand of customers. If hydrogen gas is stored in a porous medium or if it leaks into a shallow aquifer, redox reactions can oxidize hydrogen and reduce electron acceptors such as nitrate, Fe III and Mn IV (hydro)oxides, sulfate, and carbonate. These reactions are of key significance, because they can cause unintentional losses in hydrogen stored in porous media and they also can cause unwanted changes in the composition of protected potable groundwater. To represent an aquifer environment enclosing a hydrogen plume, laboratory experiments using sediment-filled columns were constructed and percolated by groundwater in equilibrium with high (2-15 bar) hydrogen partial pressures. Here, we show that hydrogen is consumed rapidly in these experiments via sulfate reduction (18 ± 5 μM h -1 ) and acetate production (0.030 ± 0.006 h -1 ), while no methanogenesis took place. The observed reaction rates were independent from the partial pressure of hydrogen and hydrogen consumption only stopped in supplemental microcosm experiments where salinity was increased above 35 g L -1 . The outcomes presented here are implemented for planning the sustainable use of the subsurface space within the ANGUS+ project.

Melting in super-earths.

PubMed

Stixrude, Lars

2014-04-28

We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of super-earths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

Constraints on Ureilite Petrogenesis and Carbon-Metal-Silicate Equilibria on the UPB

NASA Astrophysics Data System (ADS)

Goodrich, C. A.; Holloway, J. R.

1992-07-01

The most important constraints on models of ureilite petrogenesis are 1) Ureilites have lost a basaltic complement (they are ultramafic, extremely depleted in plagiophile elements, enriched in HREE, and have negative Eu anomalies and superchondritic Ca/Al ratios). 2) Ureilites experienced long equilibration times at high T (indicated by coarse grain size, extreme homogeneity of core crystals, correlations between olivine and pyroxene compositions, and metamorphic-like textures), followed by rapid cooling (indicated by structural features of pyroxene and narrow reduction rims on olivine). 3) Ureilites are probably residues (based on mass balance) but partly crystallized from melts. 4) Ureilites are derived from a minimum of six reservoirs that were distinct in oxygen isotopic composition and did not equilibrate with one another (this is consistent with the observation that olivine and pyroxene cores do not show correlations of mg with MnO, Cr2O3, Sm/Eu or Lu/Eu). 5) There is a correlation between oxygen isotopic composition and mg ratio in ureilites. Similar correlations are observed for Allende chondrules and group means of H3-L3-LL3 chondrites (Fig. 1), and are argued to result from nebular processes [1]. 6) If graphite-metal-silicate-CO/CO2 equilibrium was established during melting, then mg ratios of ureilites were determined by depth because CCO redox reactions are strongly pressure-dependent. Cohenite-bearing metallic spherule inclusions in the silicates and euhedral shapes of large graphite crystals in low-shock ureilites have been taken as evidence of equilibrium. Olivine reduction rims, highly variable interstitial metal compositions, and a lack of correlation between mg and metal content argue against equilibrium. 7) Ureilites either lost a low melting-T metal fraction or gained a refractory-rich metal component. (they have high abundances of siderophile elements but show fractionation between [Os, Ir, W, Re] and [Ni, Ga, Ge, Au]). 8) Primordial noble gases were retained in some carbon phases. 9) Ureilites formed at ~4.55 Ga but both Sm-Nd and Rb-Sr isotopic systematics have been subsequently disturbed. Constraints 1-4 are best met if ureilites are partial melt residues produced by ~25% equilibrium partial melting on an oxygen-isotopically heterogeneous parent body in >=6 distinct melting zones. If there was no global magma ocean, km-sized melting zones would not equilibrate oxygen with one another in 10 m.y. Constraints 5 and 6 appear difficult to reconcile. If the UPB inherited a nebular oxygen isotope-mg correlation how could this correlation have survived partial melting? If the melting zones all experienced approximately the same degree of melting (Mn/Mg, Cr/Mg, and HRE provide evidence for this), and silicate equilibria determined mg, then the original correlation may simply have shifted to higher mg, consistent with the position of the ureilite trend relative to the Allende trends (Fig. 1). However, if mg was depth-dependent then it is unlikely that any oxygen isotope-mg correlation would remain. Also, noble gases in carbon would be lost (violating constraint 8) during carbon redox reactions. All constraints would be better met if graphite-metal-silicate-CO/CO2 equilibrium was not established during partial melting. If graphite was primary but a CO/CO2 fluid phase was not present then there would have been no pressure/depth dependence of fO(sub)2. As long as the pressure was sufficiently high (~100-200 bars) to stabilize the most ferroan ureilite (Fo 76) then the more magnesian ureilites would have been stable in the presence of graphite and metal. On the other hand, constraints 7, 8, and 9 could be neatly met if most of the carbon was not primary but a carbon-metal-noble gas assemblage was added as a late component to the ultramafic rocks. The cohenite-bearing metallic spherules are rare and tiny (10-50 micrometers) compared to interstitial metal (mm-sized irregular grains). They appear to have been droplets of immiscible, hypereutectic Fe(Ni)-C liquids that were trapped by crystallizing silicates. In contrast, the interstitial metal and graphite show no evidence of having been a liquid Fe-C alloy and their confinement to grain boundaries and reduction rims is consistent with late addition. Goodrich and Berkley (2) argued that the spherules were carbon-saturated at 1200-1225 degrees C and therefore that the silicate liquid must have contained graphite. However, in the Fe-C system the stable graphite liquidus is much steeper than the metastable cohenite liquidus, and although these alloys were cohenite-saturated, they were not graphite-saturated. Hence, the silicate magma probably did not contain graphite and carbon was not the dominant control on fO(sub)2. Thus, it may be possible to reconcile the main constraints on ureilite petrogenesis without high pressures. [1] R.N. Clayton & T.K. Mayeda (1988] GCA 52, 1313. [2] C.A. Goodrich & J.L. Berkely (1986) GCA 50, 681.

Do plumes exist beneath Northwest Kyushu southwest Japan?

NASA Astrophysics Data System (ADS)

Mashima, H.

2014-12-01

A thermal plume model was proposed for the Hot-spot type volcanism at Northwest Kyushu, southwest Japan in the post period of opening of the Sea of Japan. The model regards the Northwest Kyushu Basalts (NWKBs) were magmas fractionated from parental magmas with MgO = 12.8 - 18.8 wt. %, indicating that partial melting occurred at temperatures from 1330 to 1500 °C and at pressures from 1.5 to 3.0 GPa (Sakuyama et al., 2009; 2014). Previous petrological and observations, however, indicate that the NWKBs separated from the source mantle at pressures shallower than those inferred from the plume model. The Mg-Fe-Ni compositions of some NWKBs suggest that they could have been in equilibrium with mantle olivines with Fo = 81 - 87, meaning that they would have been not fractionated but primitive magmas. The NWKBs are associated with primitive high magnesium andesites, indicating that partial melting continued at low pressure such as 0.5 GPa (Mashima, 2009a, b). NWKBs include not garnet lherzolite xenoliths but spinel lherzolite, showing that primitive melt separation occurred at pressure lower than 2GPa (Arai et al., 2001). These lines of evidence indicate that the separation of primitive NWKBs occurred at temperature up to 1250　°C and pressures from 0.5 to 1.5 GPa, significantly lower than those assumed by the plume model. Instead of the plume model, geology of NW Kyushu infers that the volcanism was a consequence of the tectonic evolution of NW Kyushu. The volcanism was leaks of asthenosphere thickened extensional tectonics from the Paleogene to the early Miocene. Orientations of NWKB dikes indicate their eruption was induced by the reactivation of preexisting faults under horizontal compressive stress field oriented to a NW-SE direction. This　horizontally compressive stress field would have been caused by mechanical interactions between the subducting Philippine Sea pate and the Eurasian Plate. The NW Kyushu volcanism could be explained in the context of plate tectonics without the plume hypothesis.

Education Policy and Intergenerational Transfers in Equilibrium. NBER Working Paper No. 18782

ERIC Educational Resources Information Center

Abbott, Brant; Gallipoli, Giovanni; Meghir, Costas; Violante, Giovanni L.

2013-01-01

This paper compares partial and general equilibrium effects of alternative financial aid policies intended to promote college participation. We build an overlapping generations life-cycle, heterogeneous-agent, incomplete-markets model with education, labor supply, and consumption/saving decisions. Altruistic parents make inter vivos transfers to…

Investigation of the hydrochlorination of SiCl4

NASA Technical Reports Server (NTRS)

Mui, J. Y. P.

1983-01-01

A basic, experimental study on the hydrochlorination of silicon tetrachloride and metallurgical grade silicon with hydrogen gas to form trichlorosilane was carried out to greatly expand the range of reaction conditions. The equilibrium constant, K sub p, for the hydrochlorination reaction was measured as a function of temperature, pressure and concentration. The variation of the equilibrium constant as a function of temperature provided the measurement on the heat of reaction, delta H, by the Second Law Method. The value of delta H was measured to give 10.6 Kcal/mole. The equilibrium constant was also studied as a function of concentration. In agreement with the theory, the equilibrium constant remained constant with respect to the varying H2/SiCl4 feed ratios. On the other hand, the effect of pressure on the equilibrium constant was found to be more complex.

Vapor Pressure Measurements of LiBH4, NaBH 4 and Ca(BH4)2 using Knudsen Torsion Effusion Gravimetric Method

NASA Astrophysics Data System (ADS)

Danyan, Mohammad Masoumi

Hydrogen storage is one of the critical technologies needed on the path towards commercialization for mobile applications. In the past few years, a range of new light weight hydrogen containing material has been discovered with good storage properties. Among them, lithium borohydride (LiBH 4) sodium borohydride (NaBH4) and calcium borohydride (Ca(BH 4)2) have shown promising results to be used as solid state hydrogen storage material. In this work, we have determined equilibrium vapor pressures of LiBH 4 NaBH4 and Ca(BH4)2 obtained by Torsion effusion thermogravimetric method. Results for all the three hydrides exhibited that a small fraction of the materials showed congruency, and sublimed as gaseous compound, but the majority of the material showed incongruent vaporization. Two Knudsen cells of 0.3 and 0.6mm orifice size was employed to measure the total vapor pressures. A Whitman-Motzfeldt method is used to extrapolate the measured vapor pressures to zero orifice size to calculate the equilibrium vapor pressures. In the case of LiBH4 we found that 2% of the material evaporated congruently (LiBH4(s) → LiBH4(g)) according to the equation: logPLiBH4/P 0 =-3263.5 +/-309/T + (1.079 +/-0.69) and rest as incongruent vaporization to LiH, B, and hydrogen gas according to the equation logPeq/P0 =(-3263.5 +/-309)/T+ (2.458 +/-0.69) with DeltaH evap.= 62.47+/-5.9 kJ/mol of H2, DeltaSevap. = 47.05+/-13 J/mol of H2.K. The NaBH4 also had somewhat similar behavior, with 9% congruent evaporation and equilibrium vapor pressure equation of logPLiBH4=-7700+/-335/ T+ (6.7+/-1.5) and 91% incongruent decomposition to Na and Boron metal, and hydrogen gas. The enthalpy of vaporization; DeltaHevap. = 147.2+/-6.4kJ/molH2 and DeltaSevap.= 142 +/-28 kJ/molH2.K (550-650K). The Ca(BH4) 2 exhibited similar vaporization behavior with congruency of 3.2%. The decomposition products are CaH2 and Boron metal with evolution of hydrogen gas varying with the pressure equation as logPeq /P0 =(-1562.7 +/-177)/ T+ (2.57 +/-0.155). The enthalpy and entropy of vaporization, DeltaH evap.= 29.9+/-3.3kJ/molH2, DeltaSevap.=49.14 +/-2.9 J/molH2.K (400-650K) respectively. More details of the properties of the vaporization such partial pressures of effusing gases, Gibbs energies of vaporization, molecular weight of effusing gases, as well as decomposition products, evaporation reactions, thermodynamic modeling of the disproportionation of these three compounds are discussed in this dissertation.

Vanadium oxide thin films produced by magnetron sputtering from a V2O5 target at room temperature

NASA Astrophysics Data System (ADS)

de Castro, Marcelo S. B.; Ferreira, Carlos L.; de Avillez, Roberto R.

2013-09-01

Vanadium oxide thin films were grown by RF magnetron sputtering from a V2O5 target at room temperature, an alternative route of production of vanadium oxide thin films for infrared detector applications. The films were deposited on glass substrates, in an argon-oxygen atmosphere with an oxygen partial pressure from nominal 0% to 20% of the total pressure. X-ray diffraction (XRD) and X-ray photon spectroscopy (XPS) analyses showed that the films were a mixture of several vanadium oxides (V2O5, VO2, V5O9 and V2O3), which resulted in different colors, from yellow to black, depending on composition. The electrical resistivity varied from 1 mΩ cm to more than 500 Ω cm and the thermal coefficient of resistance (TCR), varied from -0.02 to -2.51% K-1. Computational thermodynamics was used to simulate the phase diagram of the vanadium-oxygen system. Even if plasma processes are far from equilibrium, this diagram provides the range of oxygen pressures that lead to the growth of different vanadium oxide phases. These conditions were used in the present work.

Simulation of water vapor condensation on LOX droplet surface using liquid nitrogen

NASA Technical Reports Server (NTRS)

Powell, Eugene A.

1988-01-01

The formation of ice or water layers on liquid oxygen (LOX) droplets in the Space Shuttle Main Engine (SSME) environment was investigated. Formulation of such ice/water layers is indicated by phase-equilibrium considerations under conditions of high partial pressure of water vapor (steam) and low LOX droplet temperature prevailing in the SSME preburner or main chamber. An experimental investigation was begun using liquid nitrogen as a LOX simulant. A monodisperse liquid nitrogen droplet generator was developed which uses an acoustic driver to force the stream of liquid emerging from a capillary tube to break up into a stream of regularly space uniformly sized spherical droplets. The atmospheric pressure liquid nitrogen in the droplet generator reservoir was cooled below its boiling point to prevent two phase flow from occurring in the capillary tube. An existing steam chamber was modified for injection of liquid nitrogen droplets into atmospheric pressure superheated steam. The droplets were imaged using a stroboscopic video system and a laser shadowgraphy system. Several tests were conducted in which liquid nitrogen droplets were injected into the steam chamber. Under conditions of periodic droplet formation, images of 600 micron diameter liquid nitrogen droplets were obtained with the stroboscopic video systems.

The latent heat of vaporization of supercritical fluids

NASA Astrophysics Data System (ADS)

Banuti, Daniel; Raju, Muralikrishna; Hickey, Jean-Pierre; Ihme, Matthias

2016-11-01

The enthalpy of vaporization is the energy required to overcome intermolecular attractive forces and to expand the fluid volume against the ambient pressure when transforming a liquid into a gas. It diminishes for rising pressure until it vanishes at the critical point. Counterintuitively, we show that a latent heat is in fact also required to heat a supercritical fluid from a liquid to a gaseous state. Unlike its subcritical counterpart, the supercritical pseudoboiling transition is spread over a finite temperature range. Thus, in addition to overcoming intermolecular attractive forces, added energy simultaneously heats the fluid. Then, considering a transition from a liquid to an ideal gas state, we demonstrate that the required enthalpy is invariant to changes in pressure for 0 < p < 3pcr . This means that the classical pressure-dependent latent heat is merely the equilibrium part of the phase transition. The reduction at higher pressures is compensated by an increase in a nonequilibrium latent heat required to overcome residual intermolecular forces in the real fluid vapor during heating. At supercritical pressures, all of the transition occurs at non-equilibrium; for p -> 0 , all of the transition occurs at equilibrium.

Effect of organic matters on CO2 hydrate phase equilibrium conditions in Na-montmorillonite clay

NASA Astrophysics Data System (ADS)

Park, T.; Kyung, D.; Lee, W.

2013-12-01

Formation of gas hydrates provides an attractive idea for storing greenhouse gases in a long-term stable geological formation. Since the phase equilibrium conditions of gas hydrates indicate the stability of hydrates, estimation of the phase equilibrium conditions of gas hydrates in marine geological conditions is necessary. In this study, we have identified the effects of organic matters (glycine, glucose, and urea) and solid surface (montmorillonite (MMT)) on the three-phase (liquid-hydrate-vapor) equilibrium conditions of CO2 hydrate. CO2 phase equilibrium experiments were conducted using 0.5mol% organic matter solutions with and without 10g soil mineral were experimentally conducted. Addition of organic matters shifted the phase equilibrium conditions of CO2 hydrate to the higher pressure or lower pressure region because of higher competition of water molecules due to the dissolved organic matters. Presence of MMT also leaded to the higher equilibrium pressure due to the interaction of cations with water molecules. By addition of organic matters to the clay suspension, the hydrate phase equilibrium conditions were less inhibited compared to those of MMT and organic matters independently. The diminished magnitudes by addition of organic matters to the clay suspension (MMT > MMT+urea > MMT+glycine > MMT+glucose > DIW) were different to the order of inhibition degree without MMT (Glucose > glycine > urea > DIW). X-ray diffraction (XRD), scanning electron microscope (SEM), and ion chromatography (IC) analysis were conducted to support the hypothesis that the organic matters interact with cations in MMT interlayer space, and leads to the less inhibition of phase equilibrium conditions. The present study provides basic information for the formation and dissociation of CO2 hydrates in the geological formation when sequestering CO2 as a form of CO2 hydrate.

Effects of sample size, number of markers, and allelic richness on the detection of spatial genetic pattern

USGS Publications Warehouse

Landguth, Erin L.; Gedy, Bradley C.; Oyler-McCance, Sara J.; Garey, Andrew L.; Emel, Sarah L.; Mumma, Matthew; Wagner, Helene H.; Fortin, Marie-Josée; Cushman, Samuel A.

2012-01-01

The influence of study design on the ability to detect the effects of landscape pattern on gene flow is one of the most pressing methodological gaps in landscape genetic research. To investigate the effect of study design on landscape genetics inference, we used a spatially-explicit, individual-based program to simulate gene flow in a spatially continuous population inhabiting a landscape with gradual spatial changes in resistance to movement. We simulated a wide range of combinations of number of loci, number of alleles per locus and number of individuals sampled from the population. We assessed how these three aspects of study design influenced the statistical power to successfully identify the generating process among competing hypotheses of isolation-by-distance, isolation-by-barrier, and isolation-by-landscape resistance using a causal modelling approach with partial Mantel tests. We modelled the statistical power to identify the generating process as a response surface for equilibrium and non-equilibrium conditions after introduction of isolation-by-landscape resistance. All three variables (loci, alleles and sampled individuals) affect the power of causal modelling, but to different degrees. Stronger partial Mantel r correlations between landscape distances and genetic distances were found when more loci were used and when loci were more variable, which makes comparisons of effect size between studies difficult. Number of individuals did not affect the accuracy through mean equilibrium partial Mantel r, but larger samples decreased the uncertainty (increasing the precision) of equilibrium partial Mantel r estimates. We conclude that amplifying more (and more variable) loci is likely to increase the power of landscape genetic inferences more than increasing number of individuals.

Effects of sample size, number of markers, and allelic richness on the detection of spatial genetic pattern

USGS Publications Warehouse

Landguth, E.L.; Fedy, B.C.; Oyler-McCance, S.J.; Garey, A.L.; Emel, S.L.; Mumma, M.; Wagner, H.H.; Fortin, M.-J.; Cushman, S.A.

2012-01-01

The influence of study design on the ability to detect the effects of landscape pattern on gene flow is one of the most pressing methodological gaps in landscape genetic research. To investigate the effect of study design on landscape genetics inference, we used a spatially-explicit, individual-based program to simulate gene flow in a spatially continuous population inhabiting a landscape with gradual spatial changes in resistance to movement. We simulated a wide range of combinations of number of loci, number of alleles per locus and number of individuals sampled from the population. We assessed how these three aspects of study design influenced the statistical power to successfully identify the generating process among competing hypotheses of isolation-by-distance, isolation-by-barrier, and isolation-by-landscape resistance using a causal modelling approach with partial Mantel tests. We modelled the statistical power to identify the generating process as a response surface for equilibrium and non-equilibrium conditions after introduction of isolation-by-landscape resistance. All three variables (loci, alleles and sampled individuals) affect the power of causal modelling, but to different degrees. Stronger partial Mantel r correlations between landscape distances and genetic distances were found when more loci were used and when loci were more variable, which makes comparisons of effect size between studies difficult. Number of individuals did not affect the accuracy through mean equilibrium partial Mantel r, but larger samples decreased the uncertainty (increasing the precision) of equilibrium partial Mantel r estimates. We conclude that amplifying more (and more variable) loci is likely to increase the power of landscape genetic inferences more than increasing number of individuals. ?? 2011 Blackwell Publishing Ltd.

Development of solid-gas equilibrium propulsion system for small spacecraft

NASA Astrophysics Data System (ADS)

Chujo, Toshihiro; Mori, Osamu; Kubo, Yuki

2017-11-01

A phase equilibrium propulsion system is a kind of cold-gas jet in which the phase equilibrium state of the fuel is maintained in a tank and its vapor is ejected when a valve is opened. One such example is a gas-liquid equilibrium propulsion system that uses liquefied gas as fuel. This system was mounted on the IKAROS solar sail and has been demonstrated in orbit. The system has a higher storage efficiency and a lighter configuration than a high-pressure cold-gas jet because the vapor pressure is lower, and is suitable for small spacecraft. However, the system requires a gas-liquid separation device in order to avoid leakage of the liquid, which makes the system complex. As another example of a phase equilibrium propulsion system, we introduce a solid-gas equilibrium propulsion system, which uses a sublimable substance as fuel and ejects its vapor. This system has an even lower vapor pressure and does not require such a separation device, instead requiring only a filter to keep the solid inside the tank. Moreover, the system is much simpler and lighter, making it more suitable for small spacecraft, especially CubeSat-class spacecraft, and the low thrust of the system allows spacecraft motion to be controlled precisely. In addition, the thrust level can be controlled by controlling the temperature of the fuel, which changes the vapor pressure. The present paper introduces the concept of the proposed system, and describes ejection experiments and its evaluation. The basic function of the proposed system is demonstrated in order to verify its usefulness.

Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

USGS Publications Warehouse

Circone, S.; Kirby, S.H.; Stern, L.A.

2005-01-01

The composition of methane hydrate, namely nW for CH 4??nWH2O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but nW may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n W = 5.81-6.10 H2O describes the entire range of measured values, with an average composition of CH4??5.99(??0.07) H2O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence. ?? 2005 American Chemical Society.

Ballooning instabilities in tokamaks with sheared toroidal flows

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

Waelbroeck, F.L.; Chen, L.

1990-11-01

The stability of ballooning modes in the presence of sheared toroidal flows is investigated. The eigenmodes are shown to be related by a Fourier transformation to the non-exponentially growing Floquet solutions found by Cooper. It is further shown that the problem cannot be reduced further than to a two dimensional partial differential equation. Next, the generalized ballooning equation is solved analytically for a circular tokamak equilibrium with sonic flows, but with a small rotation shear compared to the sound speed. With this ordering, the centrifugal forces are comparable to the pressure gradient forces driving the instability, but coupling of themore » mode with the sound wave is avoided. A new stability criterion is derived which explicitly demonstrates that flow shear is stabilizing at constant centrifugal force gradient. 34 refs.« less

Spacecraft Sterilization Using Non-Equilibrium Atmospheric Pressure Plasma

NASA Technical Reports Server (NTRS)

Cooper, Moogega; Vaze, Nachiket; Anderson, Shawn; Fridman, Gregory; Vasilets, Victor N.; Gutsol, Alexander; Tsapin, Alexander; Fridman, Alexander

2007-01-01

As a solution to chemically and thermally destructive sterilization methods currently used for spacecraft, non-equilibrium atmospheric pressure plasmas are used to treat surfaces inoculated with Bacillus subtilis and Deinococcus radiodurans. Evidence of significant morphological changes and reduction in viability due to plasma exposure will be presented, including a 4-log reduction of B. subtilis after 2 minutes of dielectric barrier discharge treatment.

Nonlinear ballooning modes in tokamaks: stability and saturation

NASA Astrophysics Data System (ADS)

Ham, C. J.; Cowley, S. C.; Brochard, G.; Wilson, H. R.

2018-07-01

The nonlinear dynamics of magneto-hydrodynamic ballooning mode perturbations is conjectured to be characterised by the motion of isolated elliptical flux tubes. The theory of stability, dynamics and saturation of such tubes in tokamaks is developed using a generalised Archimedes’ principle. The equation of motion for a tube moving against a drag force in a general axisymmetric equilibrium is derived and then applied to a simplified ‘s–α’ equilibrium. The perturbed nonlinear tube equilibrium (saturated) states are investigated in an ‘s–α’ equilibrium with specific pressure and magnetic shear profiles. The energy of these nonlinear (ballooning) saturated states is calculated. In some cases, particularly at low magnetic shear, these finitely displaced states can have a lower energy than the equilibrium state even if the profile is linearly stable to ballooning modes (infinitesimal tube displacements) at all radii. Thus nonlinear ballooning modes can be metastable. The amplitude of the saturated tube displacement in such cases can be as large as the pressure gradient scale length. We conjecture that triggering a transition into these filamentary states can lead to hard instability limits. A short survey of different pressure profiles is presented to illustrate the variety of behaviour of perturbed elliptical flux tubes.

Analysis on the Oversize Blast Furnace Desulfurization and a Sulfide Capacity Prediction Model Based on Congregated Electron Phase

NASA Astrophysics Data System (ADS)

Zhenyang, Wang; Jianliang, Zhang; Gang, An; Zhengjian, Liu; Zhengming, Cheng; Junjie, Huang; Jingwei, Zhang

2016-02-01

Through analyzed and regressed the actual productive desulfurization data from the oversize blast furnace (5500 m3) in north China, the relationship between the sulfur distribution parameters and the slag composition in actual production situation was investigated. As the slag and hot metal phases have their own balance sulfur content or sulfur partial pressure in gas phase, respectively, the non-equilibrium of sulfur among gas, slag, and metal phases leads to the transmission and distribution of sulfur. Combined with sulfur transmission reactions between gas, slag and metal phases, C/CO pairs equilibrium, and Wagner model, the measured sulfide capacity can be acquired using sulfur distribution ratio, sulfur activity coefficient, and oxygen activity in hot metal. Based on the theory of congregated electron phase, a new sulfide capacity prediction model (CEPM) has been developed, which has a good liner relationship with the measured sulfide capacity. Thus, using the burden structure for BF, the ironmaking slag composition can be obtained simply and can be used to reliably predict the ironmaking slag desulfurization ability a few hours later after charging under a certain temperature by CEPM.

A Model for Siderophile Element Distribution in Planetary Differentiation

NASA Technical Reports Server (NTRS)

Humayun, M.; Rushmer, T.; Rankenburg, K.; Brandon, A. D.

2005-01-01

Planetary differentiation begins with partial melting of small planetesimals. At low degrees of partial melting, a sulfur-rich liquid segregates by physical mechanisms including deformation-assisted porous flow. Experimental studies of the physical mechanisms by which Fe-S melts segregate from the silicate matrix of a molten H chondrite are part of a companion paper. Geochemical studies of these experimental products revealed that metallic liquids were in equilibrium with residual metal in the H chondrite matrix. This contribution explores the geochemical signatures produced by early stages of core formation. Particularly, low-degree partial melt segregation of Fe-S liquids leaves residual metal in the silicate matrix. Some achondrites appear to be residues of partial melting, e.g., ureilites, which are known to contain metal. The metal in these achondrites may show a distinct elemental signature. To quantify the effect of sulfur on siderophile element contents of residual metal we have developed a model based on recent parametrizations of equilibrium solid metal-liquid metal partitioning experiments.

CO2-dominated Atmosphere in Equilibrium with NH3-H2O Ocean: Application to Early Titan and Ocean Planets

NASA Astrophysics Data System (ADS)

Marounina, N.; Grasset, O.; Tobie, G.; Carpy, S.

2015-12-01

During the accretion of Titan, impact heating may have been sufficient to allow the global melting of water ice (Monteux et al. 2014) and the release of volatile compounds, with CO2 and NH3 as main constituents (Tobie et al. 2012). Thus, on primitive Titan, it is thought that a massive atmosphere was in contact with a global water ocean. Similar configurations may occur on temperate water-rich planets called ocean planets (Léger et al. 2004, Kitzmann et al. 2015).Due to its rather low solubility in liquid water, carbon dioxide is expected to be one of the major components in the atmosphere. The atmospheric amount of CO2 is a key parameter for assessing the thermal evolution of the planetary surface because of its strong greenhouse effect. However, ammonia significantly affects the solubility of CO2 in water and hence the atmosphere-ocean thermo-chemical equilibrium. For primitive Titan, estimating the mass, temperature and composition of the primitive atmosphere is important to determine mechanisms that led to the present-day N2-CH4 dominated atmosphere. Similarly, for ocean planets, the influence of ammonia on the atmospheric abundance in CO2 has consequences for the definition of the habitable zone.To investigate the atmospheric composition of the water-rich worlds for a wide range of initial compositions, we have developed a vapor-liquid equilibrium model of the NH3-CO2-H2O system, where we account for the non-ideal comportment of both vapor and liquid phases and the ion speciation of volatiles dissolved in the aqueous phase. We show that adding NH3 to the CO2-H2O binary system induces an efficient absorption of the CO2 in the liquid phase and thus a lower CO2 partial pressure in the vapor phase. Indeed, the CO2 partial pressure remains low for the CO2/NH3 ratio of liquid concentrations lower than 0.5.Assuming various initial compositions of Titan's global water ocean, we explore the thermal and compositional evolution of a massive primitive atmosphere using the thermodynamical model. We are currently investigating how a massive atmosphere may be generated during the satellite growth and how it may then evolve toward a composition dominated by N2. Applications to ocean planets will also be presented at the conference.

Thermodynamics of the formaldehyde-water and formaldehyde-ice systems for atmospheric applications.

PubMed

Barret, Manuel; Houdier, Stephan; Domine, Florent

2011-01-27

Formaldehyde (HCHO) is a species involved in numerous key atmospheric chemistry processes that can significantly impact the oxidative capacity of the atmosphere. Since gaseous HCHO is soluble in water, the water droplets of clouds and the ice crystals of snow exchange HCHO with the gas phase and the partitioning of HCHO between the air, water, and ice phases must be known to understand its chemistry. This study proposes thermodynamic formulations for the partitioning of HCHO between the gas phase and the ice and liquid water phases. A reanalysis of existing data on the vapor-liquid equilibrium has shown the inadequacy of the Henry's law formulation, and we instead propose the following equation to predict the mole fraction of HCHO in liquid water at equilibrium, X(HCHO,liq), as a function of the partial pressure P(HCHO) (Pa) and temperature T (K): X(HCHO,liq) = 1.700 × 10(-15) e((8014/T))(P(HCHO))(1.105). Given the paucity of data on the gas-ice equilibrium, the solubility of HCHO and the diffusion coefficient (D(HCHO)) in ice were measured by exposing large single ice crystals to low P(HCHO). Our recommended value for D(HCHO) over the temperature range 243-266 K is D(HCHO) = 6 × 10(-12) cm(2) s(-1). The solubility of HCHO in ice follows the relationship X(HCHO,ice) = 9.898 × 10(-13) e((4072/T))(P(HCHO))(0.803). Extrapolation of these data yields the P(HCHO) versus 1/T phase diagram for the H(2)O-HCHO system. The comparison of our results to existing data on the partitioning of HCHO between the snow and the atmosphere in the high arctic highlights the interplay between thermodynamic equilibrium and kinetics processes in natural systems.

Linkage Disequilibrium in a Finite Population That Is Partially Selfing

PubMed Central

Golding, G. B.; Strobeck, C.

1980-01-01

The linkage disequilibrium expected in a finite, partially selfing population is analyzed, assuming the infinite allele model. Formulas for the expected sum of squares of the linkage disequilibria and the squared standard linkage disequilibrium are derived from the equilibrium values of sixteen inbreeding coefficients required to describe the behavior of the system. These formulas are identical to those obtained with random mating if the effective population size Ne = (1-½S)N and the effective recombination value re = (1-S)r/(1-½S), where S is the proportion of selfing, are substituted for the population size and the recombination value. Therefore, the effect of partial selfing at equilibrium is to reduce the population size by a factor 1-½S and the recombination value by a factor (1-S)/(1-½S). PMID:17249017

Non-equilibrium synergistic effects in atmospheric pressure plasmas.

PubMed

Guo, Heng; Zhang, Xiao-Ning; Chen, Jian; Li, He-Ping; Ostrikov, Kostya Ken

2018-03-19

Non-equilibrium is one of the important features of an atmospheric gas discharge plasma. It involves complicated physical-chemical processes and plays a key role in various actual plasma processing. In this report, a novel complete non-equilibrium model is developed to reveal the non-equilibrium synergistic effects for the atmospheric-pressure low-temperature plasmas (AP-LTPs). It combines a thermal-chemical non-equilibrium fluid model for the quasi-neutral plasma region and a simplified sheath model for the electrode sheath region. The free-burning argon arc is selected as a model system because both the electrical-thermal-chemical equilibrium and non-equilibrium regions are involved simultaneously in this arc plasma system. The modeling results indicate for the first time that it is the strong and synergistic interactions among the mass, momentum and energy transfer processes that determine the self-consistent non-equilibrium characteristics of the AP-LTPs. An energy transfer process related to the non-uniform spatial distributions of the electron-to-heavy-particle temperature ratio has also been discovered for the first time. It has a significant influence for self-consistently predicting the transition region between the "hot" and "cold" equilibrium regions of an AP-LTP system. The modeling results would provide an instructive guidance for predicting and possibly controlling the non-equilibrium particle-energy transportation process in various AP-LTPs in future.

Oxygen Partial Pressure and Oxygen Concentration Flammability: Can They Be Correlated?

NASA Technical Reports Server (NTRS)

Harper, Susana A.; Juarez, Alfredo; Perez, Horacio, III; Hirsch, David B.; Beeson, Harold D.

2016-01-01

NASA possesses a large quantity of flammability data performed in ISS airlock (30% Oxygen 526mmHg) and ISS cabin (24.1% Oxygen 760 mmHg) conditions. As new programs develop, other oxygen and pressure conditions emerge. In an effort to apply existing data, the question arises: Do equivalent oxygen partial pressures perform similarly with respect to flammability? This paper evaluates how material flammability performance is impacted from both the Maximum Oxygen Concentration (MOC) and Maximum Total Pressures (MTP) perspectives. From these studies, oxygen partial pressures can be compared for both the MOC and MTP methods to determine the role of partial pressure in material flammability. This evaluation also assesses the influence of other variables on flammability performance. The findings presented in this paper suggest flammability is more dependent on oxygen concentration than equivalent partial pressure.

Improved resolution of single channel dwell times reveals mechanisms of binding, priming, and gating in muscle AChR

PubMed Central

Mukhtasimova, Nuriya; daCosta, Corrie J.B.

2016-01-01

The acetylcholine receptor (AChR) from vertebrate skeletal muscle initiates voluntary movement, and its kinetics of activation are crucial for maintaining the safety margin for neuromuscular transmission. Furthermore, the kinetic mechanism of the muscle AChR serves as an archetype for understanding activation mechanisms of related receptors from the Cys-loop superfamily. Here we record currents through single muscle AChR channels with improved temporal resolution approaching half an order of magnitude over our previous best. A range of concentrations of full and partial agonists are used to elicit currents from human wild-type and gain-of-function mutant AChRs. For each agonist–receptor combination, rate constants are estimated from maximum likelihood analysis using a kinetic scheme comprised of agonist binding, priming, and channel gating steps. The kinetic scheme and rate constants are tested by stochastic simulation, followed by incorporation of the experimental step response, sampling rate, background noise, and filter bandwidth. Analyses of the simulated data confirm all rate constants except those for channel gating, which are overestimated because of the established effect of noise on the briefest dwell times. Estimates of the gating rate constants were obtained through iterative simulation followed by kinetic fitting. The results reveal that the agonist association rate constants are independent of agonist occupancy but depend on receptor state, whereas those for agonist dissociation depend on occupancy but not on state. The priming rate and equilibrium constants increase with successive agonist occupancy, and for a full agonist, the forward rate constant increases more than the equilibrium constant; for a partial agonist, the forward rate and equilibrium constants increase equally. The gating rate and equilibrium constants also increase with successive agonist occupancy, but unlike priming, the equilibrium constants increase more than the forward rate constants. As observed for a full and a partial agonist, the gain-of-function mutation affects the relationship between rate and equilibrium constants for priming but not for channel gating. Thus, resolving brief single channel currents distinguishes priming from gating steps and reveals how the corresponding rate and equilibrium constants depend on agonist occupancy. PMID:27353445

Phase Equilibria in the ZnO-"FeO"-SiO2 System in Reducing Atmosphere and in the ZnO-"FeO"-SiO2-"Cu2O" System in Equilibrium with Liquid Copper Metal at 1250 °C (1523 K)

NASA Astrophysics Data System (ADS)

Hidayat, Taufiq; Hayes, Peter C.; Jak, Evgueni

2018-05-01

Recent experimental studies in the ZnO-"FeO"-SiO2 system in reducing atmosphere demonstrated significant discrepancies with the current FactSage thermodynamic model developed using previous experimental data in this system in equilibrium with metallic iron and air. The present experimental study on phase equilibria in the ZnO-"FeO"-SiO2-"Cu2O" system in equilibrium with liquid copper at 1250 °C (1523 K) at low copper oxide concentrations in slag was initiated and undertaken to resolve these discrepancies. A high-temperature equilibration-rapid quenching-electron-probe X-ray microanalysis (EPMA) technique using a primary phase substrate support and closed system approach with Cu metal introduced to determine effective equilibrium oxygen partial pressure from the Cumetal/Cu2Oslag equilibria was applied to provide accurate information on the liquidus and corresponding solid compositions in the spinel, willemite, and tridymite primary phase fields. The present results confirmed the accuracy of the FactSage model, resolved discrepancies, and demonstrated significant uncertainties in the recent studies by other authors on the system in the open reducing atmosphere. The present study shows how this closed system approach can be used to obtain key thermodynamic data on phase equilibria in systems containing volatile metal species, overcoming the limitations and uncertainties encountered in conventional open gas/condensed phase equilibration with these systems. The study highlights the importance of the focus on obtaining accurate experimental data and the risks of misleading information from inadequate experimental control and analysis. The study also demonstrates that continuing in-depth critical review and analysis of the elemental reactions taking place in complex systems is an essential step in phase equilibrium research.

Mechanism of formation and spatial distribution of lead atoms in quartz tube atomizers

NASA Astrophysics Data System (ADS)

Johansson, M.; Baxter, D. C.; Ohlsson, K. E. A.; Frech, W.

1997-05-01

The cross-sectional and longitudinal spatial distributions of lead atoms in a quartz tube (QT) atomizers coupled to a gas chromatograph have been investigated. A uniform analyte atom distribution over the cross-section was found in a QT having an inner diameter (i.d.) of 7 mm, whereas a 10 mm i.d. QT showed an inhomogeneous distribution. These results accentuate the importance of using QTs with i.d.s below 10 mm to fulfil the prerequirement of the Beer—Lambert law to avoid bent calibration curves. The influence of the make up gas on the formation of lead atoms from alkyllead compounds has been studied, and carbon monoxide was found equally efficient in promoting free atom formation as hydrogen. This suggests that hydrogen radicals are not essential for mediating the atomization of alkyllead in QT atomizers at ˜ 1200 K. Furthermore, thermodynamic equilibrium calculations describing the investigated system were performed supporting the experimental results. Based on the presented data, a mechanism for free lead atom formation in continuously heated QT atomizers is proposed; thermal atomization occurs under thermodynamic equilibrium conditions in a reducing gas. The longitudinal atom distribution has been further investigated applying other make up gases, N 2 and He. These results show the effect of the influx of atmospheric oxygen on the free lead atom formation. Calculations of the partial pressure of oxygen in the atomizer gas phase assuming thermodynamic equilibrium have been undertaken using a convective-diffusional model.

Interpretation of trace element and isotope features of basalts: relevance of field relations, petrology, major element data, phase equilibria, and magma chamber modeling in basalt petrogenesis

NASA Astrophysics Data System (ADS)

O'Hara, M. J.; Herzberg, C.

2002-06-01

The concentrations and ratios of the major elements determine the physical properties and the phase equilibria behavior of peridotites and basalts in response to the changing energy contents of the systems. The behavior of the trace elements and isotopic features are influenced in their turn by the phase equilibria, by the physical character of the partial melting and partial crystallization processes, and by the way in which a magma interacts with its wall rocks. Concentrating on the trace element and isotope contents of basalts to the exclusion of the field relations, petrology, major element data, and phase equilibria is as improvident as slaughtering the buffalo for the sake of its tongue. The crust is a cool boundary layer and a density filter, which impedes the upward transfer of hot, dense "primary" picritic and komatiitic liquids. Planetary crusts are sites of large-scale contamination and extensive partial crystallization of primitive melts striving to escape to the surface. Escape of truly unmodified primitive melts to the surface is a rare event, requiring the resolution of daunting problems in chemical and mechanical engineering. Primary status for volumetrically abundant basalts such as mid-ocean ridge basalt, ocean island basalt, and continental flood basalts is denied by their low-pressure cotectic character, first remarked upon on petrological grounds in 1928 and on experimental grounds in 1962. These basalt liquids are products of crystal-liquid separation at low pressure. Primary status for these common basalts is further denied by the phase equilibria of such compositions at elevated pressures, when the required residual mantle mineralogy (magnesian olivine and orthopyroxene) is not stable at the liquidus. It is also denied by the picritic or komatiitic nature of partial melts of candidate upper-mantle compositions at high pressures - a conclusion supported by calculation of the melt composition, which would need to be extracted in order to explain the chemical variation between fertile and residual peridotite in natural ultramafic rock suites. The subtleties of magma chamber partial crystallization processes can produce an astounding array of "pseudospidergrams," a small selection of which have been explored here. Major modification of the trace element geochemistry and trace element ratios, even those of the highly incompatible elements, must always be entertained whenever the evidence suggests the possibility of partial crystallization. At one extreme, periodically recharged, periodically tapped magma chambers might undergo partial crystallization by ˜95% consolidation of a succession of small packets of the magma. Refluxing of the 5% residual melts from such a process into the main body of melt would lead to eventual discrimination between highly incompatible elements in that residual liquid comparable with that otherwise achieved by 0.1 to 0.3% liquid extraction in equilibrium partial melting. Great caution needs to be exercised in attempting the reconstruction of more primitive compositions by addition of troctolite, gabbro, and olivine to apparently primitive lava compositions. Special attention is focussed on the phase equilibria involving olivine, plagioclase (i.e., troctolite), and liquid because a high proportion of erupted basalts carry these two phases as phenocrysts, yet the equilibria are restricted to crustal pressures and are only encountered by wide ranges of basaltic compositions at pressures less than 0.5 GPa. The mere presence of plagioclase phenocrysts may be sufficient to disqualify candidate primitive magmas. Determination of the actual contributions of crustal processes to petrogenesis requires a return to detailed field, experimental, and forensic petrologic studies of individual erupted basalt flows; of a multitude of cumulate gabbros and their contacts; and of upper-mantle outcrops.

Pressure (Or No Royal Road)

ERIC Educational Resources Information Center

Bradley, J.

1973-01-01

Discusses how difficult the various problems of pressure, partial pressure, gas laws, and vapor pressure are for students. Outlines the evolution of the concept of pressure, the gas equation for a perfect gas, partial pressures, saturated vapor pressure, Avogadro's hypothesis, Raoult's law, and the vapor pressure of ideal solutions. (JR)

Dynamical System Analysis of Reynolds Stress Closure Equations

NASA Technical Reports Server (NTRS)

Girimaji, Sharath S.

1997-01-01

In this paper, we establish the causality between the model coefficients in the standard pressure-strain correlation model and the predicted equilibrium states for homogeneous turbulence. We accomplish this by performing a comprehensive fixed point analysis of the modeled Reynolds stress and dissipation rate equations. The results from this analysis will be very useful for developing improved pressure-strain correlation models to yield observed equilibrium behavior.

Identifying Liquid-Gas System Misconceptions and Addressing Them Using a Laboratory Exercise on Pressure-Temperature Diagrams of a Mixed Gas Involving Liquid-Vapor Equilibrium

ERIC Educational Resources Information Center

Yoshikawa, Masahiro; Koga, Nobuyoshi

2016-01-01

This study focuses on students' understandings of a liquid-gas system with liquid-vapor equilibrium in a closed system using a pressure-temperature ("P-T") diagram. By administrating three assessment questions concerning the "P-T" diagrams of liquid-gas systems to students at the beginning of undergraduate general chemistry…

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

Li, B.; The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610207; Wang, L.

With large-scale molecular dynamics simulations, we investigate shock response of He nanobubbles in single crystal Cu. For sufficient bubble size or internal pressure, a prismatic dislocation loop may form around a bubble in unshocked Cu. The internal He pressure helps to stabilize the bubble against plastic deformation. However, the prismatic dislocation loops may partially heal but facilitate nucleation of new shear and prismatic dislocation loops. For strong shocks, the internal pressure also impedes internal jetting, while a bubble assists local melting; a high speed jet breaks a He bubble into pieces dispersed among Cu. Near-surface He bubbles may burst andmore » form high velocity ejecta containing atoms and small fragments, while the ejecta velocities do not follow the three-dimensional Maxwell-Boltzmann distributions expected for thermal equilibrium. The biggest fragment size deceases with increasing shock strength. With a decrease in ligament thickness or an increase in He bubble size, the critical shock strength required for bubble bursting decreases, while the velocity range, space extension and average velocity component along the shock direction, increase. Small bubbles are more efficient in mass ejecting. Compared to voids and perfect single crystal Cu, He bubbles have pronounced effects on shock response including bubble/void collapse, Hugoniot elastic limit (HEL), deformation mechanisms, and surface jetting. HEL is the highest for perfect single crystal Cu with the same orientations, followed by He bubbles without pre-existing prismatic dislocation loops, and then voids. Complete void collapse and shear dislocations occur for embedded voids, as opposed to partial collapse, and shear and possibly prismatic dislocations for He bubbles. He bubbles lower the threshhold shock strength for ejecta formation, and increase ejecta velocity and ejected mass.« less

IRREVERSIBLE PROCESSES IN A PLASMA

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

Balescu, R.

1959-04-01

ABS>The characteristic divergences caused by long-range phenomena in gases can be eliminated in equilibrium situations by partial summations of terms individually divergent but whose sum converges. It is shown how the recently developed diagram technique enables treatment of non-equilibrium cases by a rigorous asymptotic method. The general ideas underlying the approach are briefly indicated. (T.R. H.)

Geometrically thin, hot accretion disks - Topology of the thermal equilibrium curves

NASA Technical Reports Server (NTRS)

Kusunose, Masaaki; Mineshige, Shin

1992-01-01

All the possible thermal equilibrium states of geometrically thin alpha-disks around stellar-mass black holes are presented. A (vertically) one-zone disk model is employed and it is assumed that a main energy source is viscous heating of protons and that cooling is due to bremsstrahlung and Compton scattering. There exist various branches of the thermal equilibrium solution, depending on whether disks are effectively optically thick or thin, radiation pressure-dominated or gas pressure-dominated, composed of one-temperature plasmas or of two-temperature plasmas, and with high concentration of e(+)e(-) pairs or without pairs. The thermal equilibrium curves at high temperatures (greater than or approximately equal to 10 exp 8 K) are substantially modified by the presence of e(+)e(-) pairs. The thermal stability of these branches are examined.

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

Influence of Two-Phase Thermocapillary Flow on Cryogenic Liquid Retention in Microscopic Pores

NASA Technical Reports Server (NTRS)

Schmidt, G. R.; Nadarajah, A.; Chung, T. J.; Karr, G. R.

1994-01-01

Previous experiments indicate that the bubble point pressure of spacecraft liquid hydrogen acquisition devices is reduced substantially when the ullage is pressurized with heated hydrogen vapor. The objective is to determine whether the two-phase thermocapillary convection arising from thermodynamic non-equilibrium along the porous surfaces of such devices could lead to this observed degradation in retention performance. We also examine why retention capability appears to be unaffected by pressurization with heated helium or direct heating through the porous structure. Computational assessments based on coupled solution of the flowfield and liquid free surface indicate that for highly wetting fluids in small pores, dynamic pressure and vapor recoil dictate surface morphology and drive meniscus deformation. With superheating, the two terms exert the same influence on curvature and promote mechanical equilibrium, but with subcooling, the pressure distribution produces a suction about the pore center-line that degrades retention. This result points to thermocapillary-induced deformation arising from condensation as the cause for retention loss. It also indicates that increasing the level of non-equilibrium by reducing accommodation coefficient restricts deformation and explains why retention failure does not occur with direct screen heating or helium pressurization.

Determination of methane concentrations in water in equilibrium with sI methane hydrate in the absence of a vapor phase by in situ Raman spectroscopy

USGS Publications Warehouse

Lu, W.; Chou, I.-Ming; Burruss, R.C.

2008-01-01

Most submarine gas hydrates are located within the two-phase equilibrium region of hydrate and interstitial water with pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 275 to 293 K. However, current measurements of solubilities of methane in equilibrium with hydrate in the absence of a vapor phase are limited below 20 MPa and 283.15 K, and the differences among these data are up to 30%. When these data were extrapolated to other P-T conditions, it leads to large and poorly known uncertainties. In this study, in situ Raman spectroscopy was used to measure methane concentrations in pure water in equilibrium with sI (structure one) methane hydrate, in the absence of a vapor phase, at temperatures from 276.6 to 294.6 (??0.3) K and pressures at 10, 20, 30 and 40 (??0.4%) MPa. The relationship among concentration of methane in water in equilibrium with hydrate, in mole fraction [X(CH4)], the temperature in K, and pressure in MPa was derived as: X(CH4) = exp [11.0464 + 0.023267 P - (4886.0 + 8.0158 P)/T]. Both the standard enthalpy and entropy of hydrate dissolution at the studied T-P conditions increase slightly with increasing pressure, ranging from 41.29 to 43.29 kJ/mol and from 0.1272 to 0.1330 kJ/K ?? mol, respectively. When compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by sampling and ex situ analysis, (2) it is simple and efficient, and (3) high-pressure data can be obtained safely. ?? 2007 Elsevier Ltd. All rights reserved.

Shock-induced deformation of Shergottites: Shock-pressures and perturbations of magmatic ages on Mars

NASA Astrophysics Data System (ADS)

El Goresy, Ahmed; Gillet, Ph.; Miyahara, M.; Ohtani, E.; Ozawa, S.; Beck, P.; Montagnac, G.

2013-01-01

Shergottites and Chassignites practiced major deformation effects whose nature, magnitude and relevance were controversially evaluated and disputatively debated. Our studies of many shocked shergottites present, contrary to numerous previous reports, ample evidence for pervasive shock-induced melting amounting of at least 23 vol.% of the shergottite consisting of maskelynite and pyrrhotite, partial melting of pyroxene, titanomagnetite, ilmenite and finding of several high-pressure polymorphs and pressure-induced dissociation reactions. Our results cast considerable doubt on using the refractive index (RI) or cathodoluminescence (CL) spectra of maskelynite, in estimating the magnitudes of peak-shock pressure in both shergottites and ordinary chondrites. RI of maskelynite was set after quenching of the feldspar liquid before decompression to maskelynite glass followed by glass relaxation after decompression at the closure temperature of relaxation. The RI procedure widely practiced in the past 38 years revealed unrealistic very high-pressure estimates discrepant with the high-pressure mineral inventory in shocked shergottites and ordinary chondrites and with results obtained by robust laboratory static experiments. Shergottites contain the silica high-pressure polymorphs: the scrutinyite-structured polymorph seifertite, a monoclinic ultra dense polymorph of silica with ZrO2-structure, stishovite, a dense liquidus assemblage consisting of stishovite + Na-hexa-aluminosilicate (Na-CAS) and both K-lingunite and Ca-lingunite. Applying individual high-pressure silica polymorphs alone like stishovite, to estimate the equilibrium shock pressure, is inadequate due to the considerable shift of their nominal upper pressure bounds intrinsically induced by spatially variable absorptions of minor oxides like Al2O3, Na2O, FeO, MgO and TiO2. This practice revealed variable pressure estimates even within the same shergottite subjected to the same peak-shock pressure. Occurrence of Na-CAS + stishovite, lack of the NaAlSiO4 Ca-ferrite structured polymorph or jadeite indicates that the peak-shock pressures barely exceeded 22 GPa. We present convincing and ample evidence refuting the claim that the shock-induced high-pressure inventory in shergottites and ordinary chondrites are disequilibrium assemblages resulted from local pressure spikes in excess of 80 GPa and during the decompression stage. Such scenario calls for a series of incomplete and quenched retrograde reactions starting with the crystallization of Mg-silicate perovskite + magnesiowüstite, if the claimed peak-shock pressure was in excess of 80 GPa. This would be followed by replacement of this pair by majorite-pyropess + magnesiowüstite or akimotoite + magnesiowüstite below 23 GPa and 2000 °C, polycrystalline ringwoodite above 16 GPa, respectively and finally replacement by polycrystalline olivine below 16 GPa. Such incomplete retrograde reactions were never encountered in any shergottite, chassignite or shocked ordinary chondrite so far. Olivine-ringwoodite phase transformation in the L6 Y-791384 commences with the coherent mechanism producing ringwoodite lamellae with their (1 1 1) planes parallel to the (1 0 0) of olivine followed by the incoherent mechanism due to build up of strain in the parental olivine. This is in accord with the olivine-ringwoodite settings produced in static laboratory experiments in a multi-anvil device. Olivine-ringwoodite phase transitions were also encountered in comparable settings in the shergottite NWA 1068. Application of experimentally obtained kinetic parameters of the olivine-ringwoodite phase transitions reveals possible duration of the natural dynamic events up to few seconds thus unambiguously refuting the claimed disequilibrium decompression mechanism. The shock-induced pervasive melting of labradorite, pyrrhotite, titanomagnetite, ilmenite and partial melting of clinopyroxene strongly suggests shock-induced partial to complete resetting of the Ar-Ar, Rb-Sr, Sm-Nd, Re-Os, U-Pb and Lu-Hf radiometric systems. This also casts considerable doubt on the radiometric ages shorter than 575 Ma reported in the past 38 years to allegedly be the igneous crystallization ages. These short ages probably resulted from partial or total shock-induced age resetting.

The effects of a decompression on seismic parameter profiles in a gas-charged magma

NASA Astrophysics Data System (ADS)

Sturton, Susan; Neuberg, Jürgen

2003-11-01

Seismic velocities in a gas-charged magma vary with depth and time. Relationships between pressure, density, exsolved gas content, and seismic velocity are derived and used in conjunction with expressions describing diffusive bubble growth to find a series of velocity profiles which depend on time. An equilibrium solution is obtained by considering a column of magma in which the gas distribution corresponds to the magmastatic pressure profile with depth. Decompression events of various sizes are simulated, and the resulting disequilibrium between the gas pressure and magmastatic pressure leads to bubble growth and therefore to a change of seismic velocity and density with time. Bubble growth stops when the system reaches a new equilibrium. The corresponding volume increase is accommodated by accelerating the magma column upwards and an extrusion of lava. A timescale for the system to return to equilibrium can be obtained. The effect of changes in magma viscosity and bubble number density is examined.

Reduction of phosphate ores by carbon: Part I. Process variables for design of rotary kiln system

NASA Astrophysics Data System (ADS)

Mu, Jacob; Leder, Frederic; Park, Won C.; Hard, Robert A.; Megy, Joseph; Reiss, Howard

1986-12-01

Feasibility is established for the reduction of phosphate ores in a rotary kiln, avoiding electric submerged arc furnace technology. This represents a totally new approach to phosphoric acid. Reduction rates of phosphate ore-silica mixtures by carbon in the temperature range of 1100 to 1500 °C under several CO partial pressures in nitrogen were measured in thermogravimetric analyzers. Parameters such as carbon and silica contents, particle and pellet sizes, and gas flow rate were also evaluated with various domestic and foreign phosphate ores. Furthermore, a variety of carbon sources such as subbituminous coals, bituminous coals, anthracite, petroleum coke, and metallurgical coke were tested as reducing agents. Thermodynamic considerations elucidate the temperature dependence of overall conversion as well as the role of excess silica in establishing equilibrium pressure. These findings provide the background for analysis of the kinetics of conversion in Part II of this work. These studies, in conjunction with a previously published work, indicate the importance of intergranular melt phases in the kinetics of otherwise solid state reactions.

Enhanced densification, strength and molecular mechanisms in shock compressed porous silicon

NASA Astrophysics Data System (ADS)

Lane, J. Matthew D.; Vogler, Tracy J.

2015-06-01

In most porous materials, void collapse during shock compression couples mechanical energy to thermal energy. Increased temperature drives up pressures and lowers densities in the final Hugoniot states as compared to full-density samples. Some materials, however, exhibit an anomalous enhanced densification in their Hugoniot states when porosity is introduced. We have recently shown that silicon is such a material, and demonstrated a molecular mechanism for the effect using molecular simulation. We will review results from large-scale non-equilibrium molecular dynamics (NEMD) and Hugoniotstat simulations of shock compressed porous silicon, highlighting the mechanism by which porosity produces local shear which nucleate partial phase transition and localized melting at shock pressures below typical thresholds in these materials. Further, we will characterize the stress states and strength of the material as a function of porosity from 5 to 50 percent and with various porosity microstructures. Sandia National Laboratories is a multi program 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 Security Administration under contract DE-AC04-94AL85000.

Geometrical Description of Chemical Equilibrium and Le Cha^telier's Principle: Two-Component Systems

ERIC Educational Resources Information Center

Novak, Igor

2018-01-01

Chemical equilibrium is one of the most important concepts in chemistry. The changes in properties of the chemical system at equilibrium induced by variations in pressure, volume, temperature, and concentration are always included in classroom teaching and discussions. This work introduces a novel, geometrical approach to understanding the…

Estimated Performance of Radial-Flow Exit Nozzles for Air in Chemical Equilibrium

NASA Technical Reports Server (NTRS)

Englert, Gerald W.; Kochendorfer, Fred D.

1959-01-01

The thrust, boundary-layer, and heat-transfer characteristics were computed for nozzles having radial flow in the divergent part. The working medium was air in chemical equilibrium, and the boundary layer was assumed to be all turbulent. Stagnation pressure was varied from 1 to 32 atmospheres, stagnation temperature from 1000 to 6000 R, and wall temperature from 1000 to 3000 R. Design pressure ratio was varied from 5 to 320, and operating pressure ratio was varied from 0.25 to 8 times the design pressure ratio. Results were generalized independent of divergence angle and were also generalized independent of stagnation pressure in the temperature range of 1000 to 3000 R. A means of determining the aerodynamically optimum wall angle is provided.

Outgassing rate analysis of a velvet cathode and a carbon fiber cathode

NASA Astrophysics Data System (ADS)

Li, An-Kun; Fan, Yu-Wei; Qian, Bao-Liang; Zhang, Zi-cheng; Xun, Tao

2017-11-01

In this paper, the outgassing-rates of a carbon fiber array cathode and a polymer velvet cathode are tested and discussed. Two different methods of measurements are used in the experiments. In one scheme, a method based on dynamic equilibrium of pressure is used. Namely, the cathode works in the repetitive mode in a vacuum diode, a dynamic equilibrium pressure would be reached when the outgassing capacity in the chamber equals the pumping capacity of the pump, and the outgassing rate could be figured out according to this equilibrium pressure. In another scheme, a method based on static equilibrium of pressure is used. Namely, the cathode works in a closed vacuum chamber (a hard tube), and the outgassing rate could be calculated from the pressure difference between the pressure in the chamber before and after the work of the cathode. The outgassing rate is analyzed from the real time pressure evolution data which are measured using a magnetron gauge in both schemes. The outgassing rates of the carbon fiber array cathode and the velvet cathode are 7.3 ± 0.4 neutrals/electron and 85 ± 5 neutrals/electron in the first scheme and 9 ± 0.5 neutrals/electron and 98 ± 7 neutrals/electron in the second scheme. Both the results of two schemes show that the outgassing rate of the carbon fiber array cathode is an order smaller than that of the velvet cathode under similar conditions, which shows that this carbon fiber array cathode is a promising replacement of the velvet cathode in the application of magnetically insulated transmission line oscillators and relativistic magnetrons.

L4 Milestone Report for MixEOS 2016 experiments and simulations

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

Loomis, Eric Nicholas; Bradley, Paul Andrew; Merritt, Elizabeth Catherine

2016-08-01

Accurate simulations of fluid and plasma flows require accurate thermodynamic properties of the fluids or plasmas. This thermodynamic information is represented by the equations of state of the materials. For pure materials, the equations of state may be represented by analytical models for idealized circumstances, or by tabular means, such as the Sesame tables. However, when a computational cell has a mixture of two or more fluids, the equations of state are not well understood, particularly under the circumstances of high energy densities. This is a particularly difficult issue for Eulerian codes, wherein mixed cells arise simply due to themore » advection process. LANL Eulerian codes typically assume an “Amagat’s Law” (or Law of Partial Volumes) for the mixture in which the pressures and temperatures of fluids are at an equilibrium that is consistent with the fluids being segregated within the cell. However, for purposes of computing other EOS properties, e.g., bulk modulus, or sound speed, the fluids are considered to be fully “mixed”. LANL has also been investigating implementing instead “Dalton’s Law” in which the total pressure is considered to be the sum of the partial pressures within the cell. For ideal gases, these two laws give the same result. Other possibilities are nonpressure- temperature-equilibrated approaches in which the two fluids are not assumed to “mix” at all, and the EOS properties of the cell are computed from, say, volume-weighted averages of the individual fluid properties. The assumption of the EOS properties within a mixed cell can have a pronounced effect on the behavior of the cell, resulting in, for example, different shock speeds, pressures, temperatures and densities within the cell. There is no apparent consensus as to which approach is best under HED conditions, though we note that under typical atmospheric and near atmospheric conditions the differences may be slight.« less

Design and Construction of Multi-Variable Vortex-Ring Bubble Generator for Use in Interactive Exhibit

DTIC Science & Technology

2013-12-01

providing the opportunity to teach complex subjects related to stable and unstable equilibrium, stochastic systems, and conservation laws. The...bubbles through adjustment of three variables. The seal pressure, actuating pressure, and cycle time of the triggering solenoid valve each contribute to...stable and unstable equilibrium, stochastic systems, and conservation laws. The diaphragm valve designed in this thesis provides the centerpiece for

Pressures of Partial Crystallization of Magmas Along Transforms: Implications for Crustal Accretion

NASA Astrophysics Data System (ADS)

Scott, J. L.; Zerda, C.; Brown, D.; Ciaramitaro, S. C.; Barton, M.

2016-12-01

Plate spreading at mid-ocean ridges is responsible for the creation of most of the crust on earth. The ridge system is very complex and many questions remain unresolved. Among these is the nature of magma plumbing systems beneath transform faults. Pervious workers have suggested that increased conductive cooling along transforms promotes higher pressures of partial crystallization, and that this explains the higher partial pressures of crystallization inferred for magmas erupted along slow spreading ridges compared to magmas erupted along faster spreading ridges. To test this hypothesis, we undertook a detailed analysis of pressures of partial crystallization for magmas erupted at 3 transforms along the fast to intermediate spreading East Pacific Rise(Blanco, Clipperton, and Siqueiros) and 3 transforms along the slow spreading Mid Atlantic Ridge(Famous Transform B, Kane, and 15°20'N). Pressures of partial crystallization were calculated from the compositions of glasses (quenched liquids) lying along the P (and T) dependent olivine, plagioclase, and augite cotectic using the method described by Kelley and Barton (2008). Published analyses of mid-ocean ridge basalt glasses sampled from these transforms and surrounding ridge segments were used as input data. Samples with anomalous chemical compositions and samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. The pressures of partial crystallization for the remaining 916 samples ranged from 0 to 520 MPa with the great majority ( 95%) of sample returning pressures of less than 300 MPa. Pressures of < 300 MPa are within error of the pressure range associated with partial crystallization within oceanic crust with a thickness of 7 km. Higher (sub-crustal) pressures (>300 MPa) are associated with a small number of samples from the Pacific segments. Except for the Blanco, pressures of partial crystallization do not increase as transforms are approached. These observations contrast with those of previous workers, who reported anomalously high pressures (up to 1000 MPa) for a large number of samples erupted near both Atlantic and Pacific Transforms. We conclude that higher rates of cooling along transform does not have a major effect on the onset of partial crystallization along the mid-ocean ridges

Volume of reaction by the Archibald ultracentrifuge method (lobster hemocyanin).

PubMed

Saxena, V P; Kegeles, G; Kikas, R

1976-07-01

Samples of lobster hemocyanin (Homarus americanus) under conditions of reversible reaction between whole (25 S) and half (17 S) molecules have been subjected to accurately known nitrogen pressures in analytical ultracentrifuge cells. A modified pressurization chamber of the type developed by Schumaker and colleagues has been constructed for this purpose. The molecular weight was then determined at the top (liquid-gas) meniscus, by means of the Archibald method. The logarithmic dependence upon pressure of the derived equilibrium constant then gave directly the volume of reaction. Experiments were performed in veronal-citrate buffers at pH 8, where the molar volume of formation of whole (dodecameric) molecules from half molecules appears to be negative, and at pH 8.46 in veronal-citrate buffer in the presence of 0.003 molar free calcium ion, where the molar volume of formation was estimated to be + 390 cm3/mole. In glycine-sodium hydroxide buffer at pH 9.6 containing 0.0047 molar free calcium, the molar volume of formation of whole molecules was estimated to be +120 +/- 70 cm3, corresponding to an estimated difference in partial specific volume between whole molecules and half molecules of only 1.3 (10)-4cm3/gram. The correctness of the sign of this value in glycine buffer has been verified by pressure-jump light-scattering experiments.

Influence of N2 partial pressure on structural and microhardness properties of TiN/ZrN multilayers deposited by Ar/N2 vacuum arc discharge

NASA Astrophysics Data System (ADS)

Naddaf, M.; Abdallah, B.; Ahmad, M.; A-Kharroub, M.

2016-08-01

The influence of N2 partial pressure on structural, mechanical and wetting properties of multilayered TiN/ZrN thin films deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures is investigated. X-ray diffraction (XRD) results show that the average texturing coefficient of (1 1 1) orientation and the grain size of both TiN and ZrN individual layers increase with increasing the N2 partial pressure. The Rutherford back scattering (RBS) measurements and analysis reveal that incorporation of the nitrogen in the film increases with increasing the N2 partial pressure and both TiN and ZrN individual layers have a nitrogen over-stoichiometry for N2 partial pressure ⩾50%. The change in the film micro-hardness is correlated to the changes in crystallographic texture, grain size, stoichiometry and the residual stress in the film as a function of the N2 partial pressure. In particular, stoichiometry of ZrN and TiN individual is found to play the vital role in determining the multilayer hardness. The multilayer film deposited at N2 partial pressure of 25% has the best stoichiometric ratio of both TiN and ZrN layers and the highest micro-hardness of about 32 GPa. In addition, water contact angle (WCA) measurements and analysis show a decrease in the work of adhesion on increasing the N2 partial pressure.

Putting A Human Face on Equilibrium

NASA Astrophysics Data System (ADS)

Glickstein, Neil

2005-03-01

A short biography of chemist Fritz Haber is used to personalize the abstract concepts of equilibrium chemistry for high school students in an introductory course. In addition to giving the Haber Bosch process an historic, an economic, and a scientific background the reading and subsequent discussion allows students for whom the human perspective is of paramount importance a chance to investigate the irony of balance or equilibrium in Haber's life story. Since the inclusion of the Haber biography, performance in the laboratory and on examinations for those students who are usually only partially engaged has dramatically improved.

Investigation of the hydrochlorination of SiCL4

NASA Technical Reports Server (NTRS)

Mui, J. Y. P.

1982-01-01

Reaction kinetic measurements on the hydrochlorination of SiCl4 and metallurgical grade (m.g.) silicon metal were made at a wide range of experimental variables. The effect of pressure on the reaction rate was studied at 25 psig, 100 psig, 150 psig and 200 psig, respectively. Results of these experiments show a large pressure effect on the hydrochlorination reaction. As expected, higher pressures produce a higher equilibrium SiHC13 conversion, since the hydrochlorination reaction results in a net volume contraction as product SiHC1 is formed. However, the reaction rate, namely, the rate at which the hydrochlorination reaction reaches its equilibrium SiHC13 conversion, was found to be much faster at low pressures.

Kinetic Analysis of Phospholipase C from Catharanthus roseus Transformed Roots Using Different Assays1

PubMed Central

Hernández-Sotomayor, S.M. Teresa; De Los Santos-Briones, César; Muñoz-Sánchez, J. Armando; Loyola-Vargas, Victor M.

1999-01-01

The properties of phospholipase C (PLC) partially purified from Catharanthus roseus transformed roots were analyzed using substrate lipids dispersed in phospholipid vesicles, phospholipid-detergent mixed micelles, and phospholipid monolayers spread at an air-water interface. Using [33P]phosphatidylinositol 4,5-bisphosphate (PIP2) of high specific radioactivity, PLC activity was monitored directly by measuring the loss of radioactivity from monolayers as a result of the release of inositol phosphate and its subsequent dissolution on quenching in the subphase. PLC activity was markedly affected by the surface pressure of the monolayer, with reduced activity at extremes of initial pressure. The optimum surface pressure for PIP2 hydrolysis was 20 mN/m. Depletion of PLC from solution by incubation with sucrose-loaded PIP2 vesicles followed by ultracentrifugation demonstrated stable attachment of PLC to the vesicles. A mixed micellar system was established to assay PLC activity using deoxycholate. Kinetic analyses were performed to determine whether PLC activity was dependent on both bulk PIP2 and PIP2 surface concentrations in the micelles. The interfacial Michaelis constant was calculated to be 0.0518 mol fraction, and the equilibrium dissociation constant of PLC for the lipid was 45.5 μm. These findings will add to our understanding of the mechanisms of regulation of plant PLC. PMID:10444091

Simplified conditions holding at the gas-liquid interface during evaporation

NASA Astrophysics Data System (ADS)

Morris, S. J. S.

2017-11-01

We show that on the gas side of the interface between a pure liquid and a binary mixture of its vapour with an insoluble gas, the normal derivative of vapour partial pressure pv satisfies ∂pv/∂n +αc/2 πpD (P -pv) (p -pv) = 0 . Constants α, c, D denote the dimensionless accommodation coefficient, a molecular speed and the diffusivity. Provided the continuum approximation holds within the gas, and α = O(1) , this boundary condition implies that evaporation can take one of two forms. (a) If the coexistence pressure P evaluated at the interface is less than the constant total gas pressure p, liquid at the interface is in local thermodynamic equilibrium with its vapour, and the evaporation rate is determined by diffusion through the gas. (b) Conversely, if P > p , gas at the interface consists of pure vapour, and the evaporation rate is determined by processes within the liquid. In the Wayner theory of the heated evaporating meniscus, such as that in a heat pipe, case (b) is assumed. As an application of our result, we show that some of the published experiments intended to test the Wayner theory instead operate under conditions in which case (a) holds. As a result, they do not perform the test intended.

Pressure effect in cuprates - manifestation of Le Chatelier's principle

NASA Astrophysics Data System (ADS)

Kallio, A.; Bräysy, V.; Hissa, J.

We show that the pressure dependence of Tc, the Hall coefficient scaling, resistivities etc. can be explained by the chemical equilibrium of bosons and their decay products the fermions applying essentially the classical theory. Above a temperature TBL the bosons form a lattice, which causes diffusion term in τab-1. Treatment of equilibrium in a magnetic field explains the dependence of quantities like the penetration depth λab uponm the field.

Atmospheric Condensational Properties of Ultrafine Chain and Fractal Aerosol Particles

NASA Technical Reports Server (NTRS)

Marlow, William H.

1997-01-01

The purpose for the research sponsored by this grant was to lay the foundations for qualitative understanding and quantitative description of the equilibrium vapor pressure of water vapor over the irregularly shaped, carbonaceous particles that are present in the atmosphere. This work apparently was the first systematic treatment of the subject. Research was conducted in two complementary components: 1. Calculations were performed of the equilibrium vapor pressure of water over particles comprised of aggregates of spheres in the 50-200 nm radius range. The purposes of this work were two-fold. First, since no systematic treatment of this subject had previously been conducted, its availability would be directly useful for quantitative treatment for a limited range of atmospheric aerosols. Second, it would provide qualitative indications of the effects of highly irregular particle shape on equilibrium vapor pressure of aggregates comprised of smaller spheres.

Characterization of urania vaporization with transpiration coupled thermogravimetry

DOE PAGES

McMurray, J. W.

2015-12-05

Determining equilibrium vapor pressures of materials is made easier by transpiration measurements. However, the traditional technique involves condensing the volatiles entrained in a carrier gas outside of the hot measurement zone. One potential problem is deposition en route to a cooled collector. Thermogravimetric analysis (TGA) can be used to measure in situ mass loss due to vaporization and therefore obviate the need to analyze the entire gas train due to premature plating of vapor species. Therefore, a transpiration coupled TGA technique was used to determine equilibrium pressures of UO3 gas over fluorite structure UO2+x and U3O8 at T = (1573more » and 1773) K. Moreover, we compared to calculations from models and databases in the open literature. Our study gives clarity to the thermochemical data for UO3 gas and validates the mass loss transpiration method using thermogravimetry for determining equilibrium vapor pressures of non-stoichiometric oxides.« less

Demonstration of current drive by a rotating magnetic dipole field

NASA Astrophysics Data System (ADS)

Giersch, L.; Slough, J. T.; Winglee, R.

2007-04-01

Abstract.A dipole-like rotating magnetic field was produced by a pair of circular, orthogonal coils inside a metal vacuum chamber. When these coils were immersed in plasma, large currents were driven outside the coils: the currents in the plasma were generated and sustained by the rotating magnetic dipole (RMD) field. The peak RMD-driven current was at roughly two RMD coil radii, and this current (60 kA m-) was sufficient to reverse the ambient magnetic field (33 G). Plasma density, electron temperature, magnetic field and current probes indicated that plasma formed inside the coils, then expanded outward until the plasma reached equilibrium. This equilibrium configuration was adequately described by single-fluid magnetohydrodynamic equilibrium, wherein the cross product of the driven current and magnetic filed was approximately equal to the pressure gradient. The ratio of plasma pressure to magnetic field pressure, β, was locally greater than unity.

Kinetic equilibrium reconstruction for the NBI- and ICRH-heated H-mode plasma on EAST tokamak

NASA Astrophysics Data System (ADS)

Zhen, ZHENG; Nong, XIANG; Jiale, CHEN; Siye, DING; Hongfei, DU; Guoqiang, LI; Yifeng, WANG; Haiqing, LIU; Yingying, LI; Bo, LYU; Qing, ZANG

2018-04-01

The equilibrium reconstruction is important to study the tokamak plasma physical processes. To analyze the contribution of fast ions to the equilibrium, the kinetic equilibria at two time-slices in a typical H-mode discharge with different auxiliary heatings are reconstructed by using magnetic diagnostics, kinetic diagnostics and TRANSP code. It is found that the fast-ion pressure might be up to one-third of the plasma pressure and the contribution is mainly in the core plasma due to the neutral beam injection power is primarily deposited in the core region. The fast-ion current contributes mainly in the core region while contributes little to the pedestal current. A steep pressure gradient in the pedestal is observed which gives rise to a strong edge current. It is proved that the fast ion effects cannot be ignored and should be considered in the future study of EAST.

3D equilibrium reconstruction with islands

NASA Astrophysics Data System (ADS)

Cianciosa, M.; Hirshman, S. P.; Seal, S. K.; Shafer, M. W.

2018-04-01

This paper presents the development of a 3D equilibrium reconstruction tool and the results of the first-ever reconstruction of an island equilibrium. The SIESTA non-nested equilibrium solver has been coupled to the V3FIT 3D equilibrium reconstruction code. Computed from a coupled VMEC and SIESTA model, synthetic signals are matched to measured signals by finding an optimal set of equilibrium parameters. By using the normalized pressure in place of normalized flux, non-equilibrium quantities needed by diagnostic signals can be efficiently mapped to the equilibrium. The effectiveness of this tool is demonstrated by reconstructing an island equilibrium of a DIII-D inner wall limited L-mode case with an n = 1 error field applied. Flat spots in Thomson and ECE temperature diagnostics show the reconstructed islands have the correct size and phase. ).

Ab initio investigation of the thermodynamics of cation distribution and of the electronic and magnetic structures in the LiMn2O4 spinel

NASA Astrophysics Data System (ADS)

Santos-Carballal, David; Ngoepe, Phuti E.; de Leeuw, Nora H.

2018-02-01

The spinel-structured lithium manganese oxide (LiMn2O4 ) is a material currently used as cathode for secondary lithium-ion batteries, but whose properties are not yet fully understood. Here, we report a computational investigation of the inversion thermodynamics and electronic behavior of LiMn2O4 derived from spin-polarized density functional theory calculations with a Hubbard Hamiltonian and long-range dispersion corrections (DFT+U-D3). Based on the analysis of the configurational free energy, we have elucidated a partially inverse equilibrium cation distribution for the LiMn2O4 spinel. This equilibrium degree of inversion is rationalized in terms of the crystal field stabilization effects and the difference between the size of the cations. We compare the atomic charges with the oxidation numbers for each degree of inversion. We found segregation of the Mn charge once these ions occupy the tetrahedral and octahedral sites of the spinel. We have obtained the atomic projections of the electronic band structure and density of states, showing that the normal LiMn2O4 has half-metallic properties, while the fully inverse spinel is an insulator. This material is in the ferrimagnetic state for the inverse and partially inverse cation arrangement. The optimized lattice and oxygen parameters, as well as the equilibrium degree of inversion, are in agreement with the available experimental data. The partial equilibrium degree of inversion is important in the interpretation of the lithium ion migration and surface properties of the LiMn2O4 spinel.

Thermal non-equilibrium in porous medium adjacent to vertical plate: ANN approach

NASA Astrophysics Data System (ADS)

Ahmed, N. J. Salman; Ahamed, K. S. Nazim; Al-Rashed, Abdullah A. A. A.; Kamangar, Sarfaraz; Athani, Abdulgaphur

2018-05-01

Thermal non-equilibrium in porous medium is a condition that refers to temperature discrepancy in solid matrix and fluid of porous medium. This type of flow is complex flow requiring complex set of partial differential equations that govern the flow behavior. The current work is undertaken to predict the thermal non-equilibrium behavior of porous medium adjacent to vertical plate using artificial neural network. A set of neurons in 3 layers are trained to predict the heat transfer characteristics. It is found that the thermal non-equilibrium heat transfer behavior in terms of Nusselt number of fluid as well as solid phase can be predicted accurately by using well-trained neural network.

Non-equilibrium Properties of a Pumped-Decaying Bose-Condensed Electron–Hole Gas in the BCS–BEC Crossover Region

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

Hanai, R.; Littlewood, P. B.; Ohashi, Y.

2016-03-01

We theoretically investigate a Bose-condensed exciton gas out of equilibrium. Within the framework of the combined BCS-Leggett strong-coupling theory with the non-equilibrium Keldysh formalism, we show how the Bose-Einstein condensation (BEC) of excitons is suppressed to eventually disappear, when the system is in the non-equilibrium steady state. The supply of electrons and holes from the bath is shown to induce quasi-particle excitations, leading to the partial occupation of the upper branch of Bogoliubov single-particle excitation spectrum. We also discuss how this quasi-particle induction is related to the suppression of exciton BEC, as well as the stability of the steady state.

Effect of static pressure on acoustic energy radiated by cavitation bubbles in viscous liquids under ultrasound.

PubMed

Yasui, Kyuichi; Towata, Atsuya; Tuziuti, Toru; Kozuka, Teruyuki; Kato, Kazumi

2011-11-01

The effect of static pressure on acoustic emissions including shock-wave emissions from cavitation bubbles in viscous liquids under ultrasound has been studied by numerical simulations in order to investigate the effect of static pressure on dispersion of nano-particles in liquids by ultrasound. The results of the numerical simulations for bubbles of 5 μm in equilibrium radius at 20 kHz have indicated that the optimal static pressure which maximizes the energy of acoustic waves radiated by a bubble per acoustic cycle increases as the acoustic pressure amplitude increases or the viscosity of the solution decreases. It qualitatively agrees with the experimental results by Sauter et al. [Ultrason. Sonochem. 15, 517 (2008)]. In liquids with relatively high viscosity (∼200 mPa s), a bubble collapses more violently than in pure water when the acoustic pressure amplitude is relatively large (∼20 bar). In a mixture of bubbles of different equilibrium radius (3 and 5 μm), the acoustic energy radiated by a 5 μm bubble is much larger than that by a 3 μm bubble due to the interaction with bubbles of different equilibrium radius. The acoustic energy radiated by a 5 μm bubble is substantially increased by the interaction with 3 μm bubbles.

Computation of thermodynamic equilibrium in systems under stress

NASA Astrophysics Data System (ADS)

Vrijmoed, Johannes C.; Podladchikov, Yuri Y.

2016-04-01

Metamorphic reactions may be partly controlled by the local stress distribution as suggested by observations of phase assemblages around garnet inclusions related to an amphibolite shear zone in granulite of the Bergen Arcs in Norway. A particular example presented in fig. 14 of Mukai et al. [1] is discussed here. A garnet crystal embedded in a plagioclase matrix is replaced on the left side by a high pressure intergrowth of kyanite and quartz and on the right side by chlorite-amphibole. This texture apparently represents disequilibrium. In this case, the minerals adapt to the low pressure ambient conditions only where fluids were present. Alternatively, here we compute that this particular low pressure and high pressure assemblage around a stressed rigid inclusion such as garnet can coexist in equilibrium. To do the computations we developed the Thermolab software package. The core of the software package consists of Matlab functions that generate Gibbs energy of minerals and melts from the Holland and Powell database [2] and aqueous species from the SUPCRT92 database [3]. Most up to date solid solutions are included in a general formulation. The user provides a Matlab script to do the desired calculations using the core functions. Gibbs energy of all minerals, solutions and species are benchmarked versus THERMOCALC, PerpleX [4] and SUPCRT92 and are reproduced within round off computer error. Multi-component phase diagrams have been calculated using Gibbs minimization to benchmark with THERMOCALC and Perple_X. The Matlab script to compute equilibrium in a stressed system needs only two modifications of the standard phase diagram script. Firstly, Gibbs energy of phases considered in the calculation is generated for multiple values of thermodynamic pressure. Secondly, for the Gibbs minimization the proportion of the system at each particular thermodynamic pressure needs to be constrained. The user decides which part of the stress tensor is input as thermodynamic pressure. To compute a case of high and low pressure around a stressed inclusion we first did a Finite Element Method calculation of a rigid inclusion in a viscous matrix under simple shear. From the computed stress distribution we took the local pressure (mean stress) in each grid point of the FEM calculation. This was used as input thermodynamic pressure in the Gibbs minimization and the result showed it is possible to have an equilibrium situation in which chlorite-amphibole is stable in the low pressure domain and kyanite in the high pressure domain of the stress field around the inclusion. Interestingly, the calculation predicts the redistribution of fluid from an average content of fluid in the system. The fluid in equilibrium tends to accumulate in the low pressure areas whereas it leaves the high pressure areas dry. Transport of fluid components occurs not necessarily by fluid flow, but may happen for example by diffusion. We conclude that an apparent disequilibrium texture may be explained by equilibrium under pressure variations, and apparent fluid addition by redistribution of fluid controlled by the local stress distribution. [1] Mukai et al. (2014), Journal of Petrology, 55 (8), p. 1457-1477. [2] Holland and Powell (1998), Journal of Metamorphic Geology, 16, p. 309-343 [3] Johnson et al. (1992), Computers & Geosciences, 18 (7), p. 899-947 [4] Connolly (2005), Earth and Planetary Science Letters, 236, p. 524-541

Thermobarometry of Whangarei volcanic field lavas, New Zealand: Constraints on plumbing systems of small monogenetic basalt volcanoes

NASA Astrophysics Data System (ADS)

Shane, Phil; Coote, Alisha

2018-04-01

The intra-plate, basaltic Whangarei volcanic field (WVF) is a little-studied cluster of Quaternary monogenetic volcanoes in northern New Zealand. Clinopyroxene-melt equilibria provides an insight to the ascent and storage of the magmas that is not evident from whole-rock-scale geochemistry. Basalts from two of the younger volcanoes contain a population of equilibrium and disequilibrium clinopyroxene phenocrysts. Many of the crystals are resorbed, and are characterised by diffuse, patchy zoning, and low MgO (Mg#70-80) and Cr2O3 contents. Such crystals also occur as relic cores in other phenocrysts. These grew in a magma that was more evolved than that of the host rock composition. Equilibrium clinopyroxenes are enriched in MgO (Mg#83-88) and Cr2O3 ( 0.4-0.9 wt%), and occur as reverse-zoned crystals, and rim/mantle overgrowths on relic cores of other crystals. These crystals and rim/mantles zones nucleated in magma with a composition similar to that of the host rock. The textural relationships demonstrate that a mafic magma intruded a more silicic resident magma, resulting in crystal-exchange and entrainment of antecrysts. Clinopyroxene-melt equilibria indicate that the crystallisation occurred at temperatures in the range 1135-1195 °C, and pressures in the range 290-680 MPa. The dominant pressure mode (400-550 MPa) equates to depths of about 15-19 km which coincides with a present-day body of partial melt in the crust. Higher pressures indicated by subordinate crystal populations indicate staged ascent and crystallisation above the Moho ( 26 km depth). Thus, the magmatic system is envisaged as a crystal mush column through the lower and mid crust. Such crystallisation histories are perhaps not expected in low flux, monogenetic magma systems, and reflect the importance of the crustal density structure beneath the volcanoes. Future activity could be preceded by seismic events in the lower crust as the magmas intrude localised crystal mush bodies.

Effects of Chamber Pressure and Partial Pressure of Water Vapor on Secondary Drying in Lyophilization.

PubMed

Searles, James A; Aravapalli, Sridhar; Hodge, Cody

2017-10-01

Secondary drying is the final step of lyophilization before stoppering, during which water is desorbed from the product to yield the final moisture content. We studied how chamber pressure and partial pressure of water vapor during this step affected the time course of water content of aqueous solutions of polyvinylpyrrolidone (PVP) in glass vials. The total chamber pressure had no effect when the partial pressure of water vapor was very low. However, when the vapor phase contained a substantial fraction of water vapor, the PVP moisture content was much higher. We carried out dynamic vapor sorption experiments (DVS) to demonstrate that the higher PVP moisture content was a straightforward result of the higher water vapor content in the lyophilizer. The results highlight that the partial pressure of water vapor is extremely important during secondary drying in lyophilization, and that lower chamber pressure set points for secondary drying may sometimes be justified as a strategy for ensuring low partial pressure of water vapor, especially for lyophilizers that do not inject dry gas to control pressure. These findings have direct application for process transfers/scale ups from freeze-dryers that do not inject dry gas for pressure control to those that do, and vice versa.

Applying Chemical Potential and Partial Pressure Concepts to Understand the Spontaneous Mixing of Helium and Air in a Helium-Inflated Balloon

ERIC Educational Resources Information Center

Jee-Yon Lee; Hee-Soo Yoo; Jong Sook Park; Kwang-Jin Hwang; Jin Seog Kim

2005-01-01

The spontaneous mixing of helium and air in a helium-inflated balloon is described in an experiment in which the partial pressure of the gases in the balloon are determined from the mole factions and the total pressure measured in the balloon. The results described provide a model for teaching concepts of partial pressure, chemical potential, and…

A General Method for Automatic Computation of Equilibrium Compositions and Theoretical Rocket Performance of Propellants

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Zeleznik, Frank J.; Huff, Vearl N.

1959-01-01

A general computer program for chemical equilibrium and rocket performance calculations was written for the IBM 650 computer with 2000 words of drum storage, 60 words of high-speed core storage, indexing registers, and floating point attachments. The program is capable of carrying out combustion and isentropic expansion calculations on a chemical system that may include as many as 10 different chemical elements, 30 reaction products, and 25 pressure ratios. In addition to the equilibrium composition, temperature, and pressure, the program calculates specific impulse, specific impulse in vacuum, characteristic velocity, thrust coefficient, area ratio, molecular weight, Mach number, specific heat, isentropic exponent, enthalpy, entropy, and several thermodynamic first derivatives.

Combined hydraulic and regenerative braking system

DOEpatents

Venkataperumal, R.R.; Mericle, G.E.

1979-08-09

A combined hydraulic and regenerative braking system and method for an electric vehicle is disclosed. The braking system is responsive to the applied hydraulic pressure in a brake line to control the braking of the vehicle to be completely hydraulic up to a first level of brake line pressure, to be partially hydraulic at a constant braking force and partially regenerative at a linearly increasing braking force from the first level of applied brake line pressure to a higher second level of brake line pressure, to be partially hydraulic at a linearly increasing braking force and partially regenerative at a linearly decreasing braking force from the second level of applied line pressure to a third and higher level of applied line pressure, and to be completely hydraulic at a linearly increasing braking force from the third level to all higher applied levels of line pressure.

Combined hydraulic and regenerative braking system

DOEpatents

Venkataperumal, Rama R.; Mericle, Gerald E.

1981-06-02

A combined hydraulic and regenerative braking system and method for an electric vehicle, with the braking system being responsive to the applied hydraulic pressure in a brake line to control the braking of the vehicle to be completely hydraulic up to a first level of brake line pressure, to be partially hydraulic at a constant braking force and partially regenerative at a linearly increasing braking force from the first level of applied brake line pressure to a higher second level of brake line pressure, to be partially hydraulic at a linearly increasing braking force and partially regenerative at a linearly decreasing braking force from the second level of applied line pressure to a third and higher level of applied line pressure, and to be completely hydraulic at a linearly increasing braking force from the third level to all higher applied levels of line pressure.

Plasma Equilibria With Stochastic Magnetic Fields

NASA Astrophysics Data System (ADS)

Krommes, J. A.; Reiman, A. H.

2009-05-01

Plasma equilibria that include regions of stochastic magnetic fields are of interest in a variety of applications, including tokamaks with ergodic limiters and high-pressure stellarators. Such equilibria are examined theoretically, and a numerical algorithm for their construction is described.^2,3 % The balance between stochastic diffusion of magnetic lines and small effects^2 omitted from the simplest MHD description can support pressure and current profiles that need not be flattened in stochastic regions. The diffusion can be described analytically by renormalizing stochastic Langevin equations for pressure and parallel current j, with particular attention being paid to the satisfaction of the periodicity constraints in toroidal configurations with sheared magnetic fields. The equilibrium field configuration can then be constructed by coupling the prediction for j to Amp'ere's law, which is solved numerically. A. Reiman et al., Pressure-induced breaking of equilibrium flux surfaces in the W7AS stellarator, Nucl. Fusion 47, 572--8 (2007). J. A. Krommes and A. H. Reiman, Plasma equilibrium in a magnetic field with stochastic regions, submitted to Phys. Plasmas. J. A. Krommes, Fundamental statistical theories of plasma turbulence in magnetic fields, Phys. Reports 360, 1--351.

Large Volume Non-Equilibrium Air Plasma at Atmospheric Pressure: A Novel Method with Low Power Requirements

DTIC Science & Technology

2007-02-28

of magnitude in size. Also unlike corona -like devices such as the plasma needle , which generates 2-3 mm long plasma at the tip of a sharp wire...Distribution Unlimited Table of Contents Abstract AC System with Water Electrode Current voltage characteristics Plasma diagnostics results Experimental setup...Laroussi, PI. 4 AC SYSTEM WITH WATER ELECTRODE Recently, non-equilibrium atmospheric pressure plasmas have been used in a variety of material processing

Ideal relaxation of the Hopf fibration

NASA Astrophysics Data System (ADS)

Smiet, Christopher Berg; Candelaresi, Simon; Bouwmeester, Dirk

2017-07-01

Ideal magnetohydrodynamics relaxation is the topology-conserving reconfiguration of a magnetic field into a lower energy state where the net force is zero. This is achieved by modeling the plasma as perfectly conducting viscous fluid. It is an important tool for investigating plasma equilibria and is often used to study the magnetic configurations in fusion devices and astrophysical plasmas. We study the equilibrium reached by a localized magnetic field through the topology conserving relaxation of a magnetic field based on the Hopf fibration in which magnetic field lines are closed circles that are all linked with one another. Magnetic fields with this topology have recently been shown to occur in non-ideal numerical simulations. Our results show that any localized field can only attain equilibrium if there is a finite external pressure, and that for such a field a Taylor state is unattainable. We find an equilibrium plasma configuration that is characterized by a lowered pressure in a toroidal region, with field lines lying on surfaces of constant pressure. Therefore, the field is in a Grad-Shafranov equilibrium. Localized helical magnetic fields are found when plasma is ejected from astrophysical bodies and subsequently relaxes against the background plasma, as well as on earth in plasmoids generated by, e.g., a Marshall gun. This work shows under which conditions an equilibrium can be reached and identifies a toroidal depression as the characteristic feature of such a configuration.

Effects of porosity on shock-induced melting of honeycomb-shaped Cu nanofoams

NASA Astrophysics Data System (ADS)

Zhao, Fengpeng

Metallic foams are of fundamental and applied interests in various areas, including structure engineering (e.g., lightweight structural members and energy absorbers), and shock physics (e.g., as laser ablators involving shock-induced melting and vaporization).Honeycomb-shaped metallic foams consist of regular array of hexagonal cells in two dimensions and have extensive applications and represent a unique, simple yet useful model structure for exploring mechanisms and making quantitative assessment. We investigate shock-induced melting in honeycomb-shaped Cu nanofoams with extensive molecular dynamics simulations. A total of ten porosities (phi) are explored, ranging from 0 to 0.9 at an increment of 0.1. Upon shock compression, void collapse induces local melting followed by supercooling for sufficiently high porosity at low shock strengths. While superheating of solid remnants occurs for sufficiently strong shocks at phi<0.1. Both supercooling of melts and superheating of solid remnants are transient, and the equilibrated shock states eventually fall on the equilibrium melting curve for partial melting. However, phase equilibrium has not been achieved on the time scale of simulations in supercooled Cu liquid (from completely melted nanofoams). The temperatures for incipient and complete melting are related to porosity via a power law and approach the melting temperature at zero pressure as phi tends to 1.

Investigation of La xSr 1-xCo yM 1-yO 3-δ (M = Mn Fe) perovskite materials as thermochemical energy storage media

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

Babiniec, Sean Michael; Coker, Eric Nicholas; Miller, James E.

2015-06-23

Materials in the La xSr 1–xCo yMn 1–yO 3–δ (LSCM) and La xSr 1–xCo yFe 1–yO 3–δ (LSCF) families are candidates for high-temperature thermochemical energy storage due to their facility for cyclic endothermic reduction and exothermic oxidation. A set of 16 LSCM and 21 LSCF compositions were synthesized by a modified Pechini method and characterized by powder X-ray diffraction and thermogravimetric analysis. All materials were found to be various symmetries of the perovskite phase. LSCM was indexed as tetragonal, cubic, rhombohedral, or orthorhombic as a function of increased lanthanum content. For LSCF, compositions containing low lanthanum content were indexed asmore » cubic while materials with high lanthanum content were indexed as rhombohedral. An initial screening of redox activity was completed by thermogravimetric analysis for each composition. The top three compositions with the greatest recoverable redox capacity for each family were further characterized in equilibrium thermogravimetric experiments over a range of temperatures and oxygen partial pressures. As a result, these equilibrium experiments allowed the extraction of thermodynamic parameters for LSCM and LSCF compositions operated in thermochemical energy storage conditions.« less

First-principles study of low Miller index Ni3S2 surfaces in hydrotreating conditions.

PubMed

Aray, Yosslen; Vega, David; Rodriguez, Jesus; Vidal, Alba B; Grillo, Maria Elena; Coll, Santiago

2009-03-12

Density functional theory (DFT) calculations combined with surface thermodynamic arguments and the Gibbs-Curie-Wulff equilibrium morphology formalism have been employed to explore the effect of the reaction conditions, temperature (T), and gas-phase partial pressures (PH2 and PH2S) on the stability of nickel sulfide (Ni3S2) surfaces. Furthermore, the strength and nature of chemical bonds for selected Ni3S2 surface cuts were investigated with the quantum theory of atoms in molecules methodology. A particular analysis of the electrostatic potential within this theoretical framework is performed to study the potential activity of nickel sulfide nanoparticles as hydrodesulfurization (HDS) catalysts. The calculated thermodynamic surface stabilities and the resulting equilibrium morphology model suggest that unsupported Ni3S2 nanoparticles mainly expose (111) and (111) type surface faces in HDS conditions. Analysis of the electrostatic potential mapped onto a selected electron density isocontour (0.001 au) on those expose surface reveals a poor potential reactivity toward electron-donating reagents (i.e., low Lewis acidity). Consequently, a very low attraction between coordinatively unsaturated active sites (Lewis sites) exposed at the catalytic particles and the S atoms coming from reagent polluting molecules does inactive these kinds of particles for HDS.

ATMOSPHERIC CIRCULATION OF HOT JUPITERS: DAYSIDE–NIGHTSIDE TEMPERATURE DIFFERENCES

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

Komacek, Thaddeus D.; Showman, Adam P., E-mail: tkomacek@lpl.arizona.edu

The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing dayside-to-nightside brightness temperature difference with increasing equilibrium temperature. Here, we present a three-dimensional model that explains this relationship, in order to provide insight into the processes that control heat redistribution in tidally locked planetary atmospheres. This three-dimensional model combines predictive analytic theory for the atmospheric circulation and dayside–nightside temperature differences over a range of equilibrium temperatures, atmospheric compositions, and potential frictional drag strengths with numerical solutions of the circulation that verify this analytic theory. The theory shows that the longitudinal propagation of waves mediates dayside–nightside temperaturemore » differences in hot Jupiter atmospheres, analogous to the wave adjustment mechanism that regulates the thermal structure in Earth’s tropics. These waves can be damped in hot Jupiter atmospheres by either radiative cooling or potential frictional drag. This frictional drag would likely be caused by Lorentz forces in a partially ionized atmosphere threaded by a background magnetic field, and would increase in strength with increasing temperature. Additionally, the amplitude of radiative heating and cooling increases with increasing temperature, and hence both radiative heating/cooling and frictional drag damp waves more efficiently with increasing equilibrium temperature. Radiative heating and cooling play the largest role in controlling dayside–nightside temperature differences in both our analytic theory and numerical simulations, with frictional drag only being important if it is stronger than the Coriolis force. As a result, dayside–nightside temperature differences in hot Jupiter atmospheres increase with increasing stellar irradiation and decrease with increasing pressure.« less

Kinetics of Inorganic Calcite Dissolution in Seawater under Pressure

NASA Astrophysics Data System (ADS)

Dong, S.; Subhas, A.; Rollins, N.; Berelson, W.; Adkins, J. F.

2016-02-01

While understanding calcium carbonate dissolution is vital in constructing global carbon cycles and predicting the effect of seawater acidification as a result of increasing atmospheric CO2, there is still a major debate over the basic formulation of a dissolution rate law. The kinetics of calcium carbonate dissolution are typically described by the equation: Rate=k(1-Ω)n, while Ω=[Ca2+][CO32-]/Ksp. In this study, 13C-labeled calcite is dissolved in unlabeled seawater and the evolving d13C composition of the fluid is traced over time to establish dissolution rate. Instead of changing ion concentration to obtain varying Ω (as in our previous study; Subhas et al. 2015), we changed Ksp by conducting experiments under different pressures (described in theory as ∂lnKsp/∂P=-ΔV/RT, where ΔV is partial molal volume). This involved the construction of a pressure vessel that could hold our sample bag and provide aliquots while remaining pressurized. Pressure experiments were conducted between 0-2000PSI. Results support the conclusion in our previous study that near-equilibrium dissolution rates are highly nonlinear, but give a disparate relationship between undersaturation and dissolution rate if Ω is calculated assuming the specific ΔV embedded in CO2SYS. A revised ΔV from -37cm3 to -65cm3 would make the dissolution formulation equation agree, but clearly appears unreasonable. Our results are explained by a pressure effect on carbonate dissolution kinetics over and above the influence of pressure on Ω. If this is a phenomenon that occurs in nature, then we would predict that dissolution should be occurring shallower in the water column (as sometimes observed) than indicated by standard Ω calculations.

Theoretical Performance of Liquid Hydrogen with Liquid Oxygen as a Rocket Propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; McBride, Bonnie J.

1959-01-01

Theoretical rocket performance for both equilibrium and frozen composition during expansion was calculated for the propellant combination liquid hydrogen and liquid oxygen at four chamber pressures (60, 150, 300, and 600 lb/sq in. abs) and a wide range of pressure ratios (1 to 4000) and oxidant-fuel ratios (1.190 to 39.683). Data are given to estimate performance parameters at chamber pressures other than those for which data are tabulated. The parameters included are specific impulse, specific impulse in vacuum, combustion-chamber temperature, nozzle-exit temperature, molecular weight, molecular-weight derivatives, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, thermal conductivity, Mach number, and equilibrium gas compositions.

3D equilibrium reconstruction with islands

DOE PAGES

Cianciosa, M.; Hirshman, S. P.; Seal, S. K.; ...

2018-02-15

This study presents the development of a 3D equilibrium reconstruction tool and the results of the first-ever reconstruction of an island equilibrium. The SIESTA non-nested equilibrium solver has been coupled to the V3FIT 3D equilibrium reconstruction code. Computed from a coupled VMEC and SIESTA model, synthetic signals are matched to measured signals by finding an optimal set of equilibrium parameters. By using the normalized pressure in place of normalized flux, non-equilibrium quantities needed by diagnostic signals can be efficiently mapped to the equilibrium. The effectiveness of this tool is demonstrated by reconstructing an island equilibrium of a DIII-D inner wallmore » limited L-mode case with an n = 1 error field applied. Finally, flat spots in Thomson and ECE temperature diagnostics show the reconstructed islands have the correct size and phase.« less

3D equilibrium reconstruction with islands

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

Cianciosa, M.; Hirshman, S. P.; Seal, S. K.

This study presents the development of a 3D equilibrium reconstruction tool and the results of the first-ever reconstruction of an island equilibrium. The SIESTA non-nested equilibrium solver has been coupled to the V3FIT 3D equilibrium reconstruction code. Computed from a coupled VMEC and SIESTA model, synthetic signals are matched to measured signals by finding an optimal set of equilibrium parameters. By using the normalized pressure in place of normalized flux, non-equilibrium quantities needed by diagnostic signals can be efficiently mapped to the equilibrium. The effectiveness of this tool is demonstrated by reconstructing an island equilibrium of a DIII-D inner wallmore » limited L-mode case with an n = 1 error field applied. Finally, flat spots in Thomson and ECE temperature diagnostics show the reconstructed islands have the correct size and phase.« less

Conformational Mobility in Cytochrome P450 3A4 Explored by Pressure-Perturbation EPR Spectroscopy

PubMed Central

Davydov, Dmitri R.; Yang, Zhongyu; Davydova, Nadezhda; Halpert, James R.; Hubbell, Wayne L.

2016-01-01

We used high hydrostatic pressure as a tool for exploring the conformational landscape of human cytochrome P450 3A4 (CYP3A4) by electron paramagnetic resonance and fluorescence spectroscopy. Site-directed incorporation of a luminescence resonance energy transfer donor-acceptor pair allowed us to identify a pressure-dependent equilibrium between two states of the enzyme, where an increase in pressure increased the spatial separation between the two distantly located fluorophores. This transition is characterized by volume change (ΔV°) and P1/2 values of −36.8 ± 5.0 mL/mol and 1.45 ± 0.33 kbar, respectively, which corresponds to a Keq° of 0.13 ± 0.06, so that only 15% of the enzyme adopts the pressure-promoted conformation at ambient pressure. This pressure-promoted displacement of the equilibrium is eliminated by the addition of testosterone, an allosteric activator. Using site-directed spin labeling, we demonstrated that the pressure- and testosterone-sensitive transition is also revealed by pressure-induced changes in the electron paramagnetic resonance spectra of a nitroxide side chain placed at position 85 or 409 of the enzyme. Furthermore, we observed a pressure-induced displacement of the emission maxima of a solvatochromic fluorophore (7-diethylamino-3-((((2-maleimidyl)ethyl)amino)carbonyl) coumarin) placed at the same positions, which suggests a relocation to a more polar environment. Taken together, the results reveal an effector-dependent conformational equilibrium between open and closed states of CYP3A4 that involves a pronounced change at the interface between the region of α-helices A/A′ and the meander loop of the enzyme, where residues 85 and 409 are located. Our study demonstrates the high potential of pressure-perturbation strategies for studying protein conformational landscapes. PMID:27074675

Structural, mechanical, electrical and wetting properties of ZrNx films deposited by Ar/N2 vacuum arc discharge: Effect of nitrogen partial pressure

NASA Astrophysics Data System (ADS)

Abdallah, B.; Naddaf, M.; A-Kharroub, M.

2013-03-01

Non-stiochiometric zirconium nitride (ZrNx) thin films have been deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures at different N2 partial pressure ratio. The microstructure, mechanical, electrical and wetting properties of these films are studied by means of X-ray diffraction (XRD), micro-Raman spectroscopy, Rutherford back scattering (RBS) technique, conventional micro-hardness testing, electrical resistivity, atomic force microscopy (AFM) and contact angle (CA) measurements. RBS results and analysis show that the (N/Zr) ratio in the film increases with increasing the N2 partial pressure. A ZrNx film with (Zr/N) ratio in the vicinity of stoichiometric ZrN is obtained at N2 partial pressure of 10%. XRD and Raman results indicate that all deposited films have strained cubic crystal phase of ZrN, regardless of the N2 partial pressure. On increasing the N2 partial pressure, the relative intensity of (1 1 1) orientation with respect to (2 0 0) orientation is seen to decrease. The effect of N2 partial pressure on micro-hardness and the resistivity of the deposited film is revealed and correlated to the alteration of grain size, crystallographic texture, stoichiometry and residual stress developed in the film. In particular, it is found that residual stress and nitrogen incorporation in the film play crucial role in the alteration of micro-hardness and resistivity respectively. In addition, CA and AFM results demonstrate that as N2 partial pressure increases, both the surface hydrophobicity and roughness of the deposited film increase, leading to a significant decrease in the film surface free energy (SFE).

Effect of methane partial pressure on the performance of a membrane biofilm reactor coupling methane-dependent denitrification and anammox.

PubMed

Cai, Chen; Hu, Shihu; Chen, Xueming; Ni, Bing-Jie; Pu, Jiaoyang; Yuan, Zhiguo

2018-10-15

Complete nitrogen removal has recently been demonstrated by integrating anaerobic ammonium oxidation (anammox) and denitrifying anaerobic methane oxidation (DAMO) processes. In this work, the effect of methane partial pressure on the performance of a membrane biofilm reactor (MBfR) consisting of DAMO and anammox microorganisms was evaluated. The activities of DAMO archaea and DAMO bacteria in the biofilm increased significantly with increased methane partial pressure, from 367 ± 9 and 58 ± 22 mg-N L -1 d -1 to 580 ± 12 and 222 ± 22 mg-N L -1 d -1 , respectively, while the activity of anammox bacteria only increased slightly, when the methane partial pressure was elevated from 0.24 to 1.39 atm in the short-term batch tests. The results were supported by a long-term (seven weeks) continuous test, when the methane partial pressure was dropped from 1.39 to 0.78 atm. The methane utilization efficiency was always above 96% during both short-term and long-term tests. Taken together, nitrogen removal rate (especially the nitrate reduction rate by DAMO archaea) and methane utilization efficiency could be maintained at high levels in a broad range of methane partial pressure (0.24-1.39 atm in this study). In addition, a previously established DAMO/anammox biofilm model was used to analyze the experimental data. The observed impacts of methane partial pressure on biofilm activity were well explained by the modeling results. These results suggest that methane partial pressure can potentially be used as a manipulated variable to control reaction rates, ultimately to maintain high nitrogen removal efficiency, according to nitrogen loading rate. Copyright © 2018 Elsevier B.V. All rights reserved.

Pressure driven currents near magnetic islands in 3D MHD equilibria: Effects of pressure variation within flux surfaces and of symmetry

NASA Astrophysics Data System (ADS)

Reiman, Allan H.

2016-07-01

In toroidal, magnetically confined plasmas, the heat and particle transport is strongly anisotropic, with transport along the field lines sufficiently strong relative to cross-field transport that the equilibrium pressure can generally be regarded as constant on the flux surfaces in much of the plasma. The regions near small magnetic islands, and those near the X-lines of larger islands, are exceptions, having a significant variation of the pressure within the flux surfaces. It is shown here that the variation of the equilibrium pressure within the flux surfaces in those regions has significant consequences for the pressure driven currents. It is further shown that the consequences are strongly affected by the symmetry of the magnetic field if the field is invariant under combined reflection in the poloidal and toroidal angles. (This symmetry property is called "stellarator symmetry.") In non-stellarator-symmetric equilibria, the pressure-driven currents have logarithmic singularities at the X-lines. In stellarator-symmetric MHD equilibria, the singular components of the pressure-driven currents vanish. These equilibria are to be contrasted with equilibria having B ṡ∇p =0 , where the singular components of the pressure-driven currents vanish regardless of the symmetry. They are also to be contrasted with 3D MHD equilibrium solutions that are constrained to have simply nested flux surfaces, where the pressure-driven current goes like 1 /x near rational surfaces, where x is the distance from the rational surface, except in the case of quasi-symmetric flux surfaces. For the purpose of calculating the pressure-driven currents near magnetic islands, we work with a closed subset of the MHD equilibrium equations that involves only perpendicular force balance, and is decoupled from parallel force balance. It is not correct to use the parallel component of the conventional MHD force balance equation, B ṡ∇p =0 , near magnetic islands. Small but nonzero values of B ṡ∇p are important in this region, and small non-MHD contributions to the parallel force balance equation cannot be neglected there. Two approaches are pursued to solve our equations for the pressure driven currents. First, the equilibrium equations are applied to an analytically tractable magnetic field with an island, obtaining explicit expressions for the rotational transform and magnetic coordinates, and for the pressure-driven current and its limiting behavior near the X-line. The second approach utilizes an expansion about the X-line to provide a more general calculation of the pressure-driven current near an X-line and of the rotational transform near a separatrix. The study presented in this paper is motivated, in part, by tokamak experiments with nonaxisymmetric magnetic perturbations, where significant differences are observed between the behavior of stellarator-symmetric and non-stellarator-symmetric configurations with regard to stabilization of edge localized modes by resonant magnetic perturbations. Implications for the coupling between neoclassical tearing modes, and for magnetic island stability calculations, are also discussed.

Liquid-Vapor Equilibrium of Multicomponent Cryogenic Systems

NASA Technical Reports Server (NTRS)

Thompson, W. Reid; Calado, Jorge C. G.; Zollweg, John A.

1990-01-01

Liquid-vapor and solid-vapor equilibria at low to moderate pressures and low temperatures are important in many solar system environments, including the surface and clouds of Titan, the clouds of Uranus and Neptune, and the surfaces of Mars and Triton. The familiar cases of ideal behavior are limiting cases of a general thermodynamic representation for the vapor pressure of each component in a homogeneous multicomponent system. The fundamental connections of laboratory measurements to thermodynamic models are through the Gibbs-Duhem relation and the Gibbs-Helmholtz relation. Using laboratory measurements of the total pressure, temperature, and compositions of the liquid and vapor phases at equilibrium, the values of these parameters can be determined. The resulting model for vapor-liquid equilibrium can then conveniently and accurately be used to calculate pressures, compositions, condensation altitudes, and their dependencies on changing climatic conditions. A specific system being investigated is CH4-C2H6-N2, at conditions relevant to Titan's surface and atmosphere. Discussed are: the modeling of existing data on CH4-N2, with applications to the composition of Titan's condensate clouds; some new measurements on the CH4-C2H6 binary, using a high-precision static/volumetric system, and on the C2H6-N2 binary, using the volumetric system and a sensitive cryogenic flow calorimeter; and describe a new cryogenic phase-equilibrium vessel with which we are beginning a detailed, systematic study of the three constituent binaries and the ternary CH4-C2H6-N2 system at temperatures ranging from 80 to 105 K and pressures from 0.1 to 7 bar.

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).

Hydro-isomerization of n-hexane on bi-functional catalyst: Effect of total and hydrogen partial pressures

NASA Astrophysics Data System (ADS)

Thoa, Dao Thi Kim; Loc, Luu Cam

2017-09-01

The effect of both total pressure and hydrogen partial pressure during n-hexane hydro-isomerization over platinum impregnated on HZSM-5 was studied. n-Hexane hydro-isomerization was conducted at atmospheric pressure and 0.7 MPa to observe the influence of total pressure. In order to see the effect of hydrogen partial pressure, the reaction was taken place at different partial pressure of hydrogen varied from 307 hPa to 718 hPa by dilution with nitrogen to keep the total pressure at 0.1 MPa. Physico-chemical characteristics of catalyst were determined by the methods of nitrogen physi-sorption BET, SEM, XRD, TEM, NH3-TPD, TPR, and Hydrogen Pulse Chemi-sorption. Activity of catalyst in the hydro-isomerization of n-hexane was studied in a micro-flow reactor in the temperature range of 225-325 °C; the molar ratio H2/ hydrocarbon: 5.92, concentration of n-hexane: 9.2 mol.%, GHSV 2698 h-1. The obtained catalyst expressed high acid density, good reducing property, high metal dispersion, and good balance between metallic and acidic sites. It is excellent contact for n-hexane hydro-isomerization. At 250 °C, n-hexane conversion and selectivity were as high as 59-76 % and 85-99 %, respectively. It was found that catalytic activity was promoted either by total pressure or hydrogen partial pressure. At total pressure of 0.7 MPa while hydrogen partial pressure of 718 hPa, catalyst produced 63 RON liquid product containing friendly environmental iso-paraffins which is superior blending stock for green gasoline. Hydrogen did not only preserve catalyst actives by depressing hydrocracking and removing coke precursors but also facilitated hydride transfer step in the bi-functional bi-molecular mechanism.

Sulfur control in ion-conducting membrane systems

DOEpatents

Stein, VanEric Edward; Richards, Robin Edward; Brengel, David Douglas; Carolan, Michael Francis

2003-08-05

A method for controlling the sulfur dioxide partial pressure in a pressurized, heated, oxygen-containing gas mixture which is contacted with an ion-conducting metallic oxide membrane which permeates oxygen ions. The sulfur dioxide partial pressure in the oxygen-depleted non-permeate gas from the membrane module is maintained below a critical sulfur dioxide partial pressure, p.sub.SO2 *, to protect the membrane material from reacting with sulfur dioxide and reducing the oxygen flux of the membrane. Each ion-conducting metallic oxide material has a characteristic critical sulfur dioxide partial pressure which is useful in determining the required level of sulfur removal from the feed gas and/or from the fuel gas used in a direct-fired feed gas heater.

Pressure Effects on Oxygen Concentration Flammability Thresholds of Materials for Aerospace Applications

NASA Technical Reports Server (NTRS)

Hirsch, David; Williams, Jim; Beeson, Harold

2006-01-01

Spacecraft materials selection is based on an upward flammability test conducted in a quiescent environment in the highest-expected oxygen-concentration environment. However, NASA s advanced space exploration program is anticipating using various habitable environments. Because limited data is available to support current program requirements, a different test logic is suggested to address these expanded atmospheric environments through the determination of materials self-extinguishment limits. This paper provides additional pressure effects data on oxygen concentration and partial pressure self-extinguishment limits under quiescent conditions. For the range of total pressures tested, the oxygen concentration and oxygen partial pressure flammability thresholds show a near linear function of total pressure. The oxygen concentration/oxygen partial pressure flammability thresholds depend on the total pressure and appear to increase with increasing oxygen concentration (and oxygen partial pressure). For the Constellation Program, the flammability threshold information will allow NASA to identify materials with increased flammability risk because of oxygen concentration and total pressure changes, minimize potential impacts, and allow for development of sound requirements for new spacecraft and extraterrestrial landers and habitats.

Stability of the thermodynamic equilibrium - A test of the validity of dynamic models as applied to gyroviscous perpendicular magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Faghihi, Mustafa; Scheffel, Jan; Spies, Guenther O.

1988-05-01

Stability of the thermodynamic equilibrium is put forward as a simple test of the validity of dynamic equations, and is applied to perpendicular gyroviscous magnetohydrodynamics (i.e., perpendicular magnetohydrodynamics with gyroviscosity added). This model turns out to be invalid because it predicts exponentially growing Alfven waves in a spatially homogeneous static equilibrium with scalar pressure.

Method and apparatus for monitoring oxygen partial pressure in air masks

NASA Technical Reports Server (NTRS)

Kelly, Mark E. (Inventor); Pettit, Donald R. (Inventor)

2006-01-01

Method and apparatus are disclosed for monitoring an oxygen partial pressure in an air mask and providing a tactile warning to the user. The oxygen partial pressure in the air mask is detected using an electrochemical sensor, the output signal from which is provided to a comparator. The comparator compares the output signal with a preset reference value or range of values representing acceptable oxygen partial pressures. If the output signal is different than the reference value or outside the range of values, the air mask is vibrated by a vibrating motor to alert the user to a potentially hypoxic condition.

Effect of substrate temperature and oxygen partial pressure on RF sputtered NiO thin films

NASA Astrophysics Data System (ADS)

Cheemadan, Saheer; Santhosh Kumar, M. C.

2018-04-01

Nickel oxide (NiO) thin films were deposited by RF sputtering process and the physical properties were investigated for varying substrate temperatures and oxygen partial pressure. The variation of the crystallographic orientation and microstructure of the NiO thin films with an increase in substrate temperature were studied. It was observed that NiO thin films deposited at 350 °C shows relatively good crystalline characteristics with a preferential orientation along (111) plane. With the optimum substrate temperature of 350 °C, the NiO thin films were deposited under various oxygen partial pressures at the same experimental conditions. The structural, optical and electrical properties of NiO thin films under varying oxygen partial pressure of 10%–50% were investigated. From XRD it is clear that the films prepared in the pure argon atmosphere were amorphous while the films in oxygen partial pressure exhibited polycrystalline NiO phase. SEM and AFM investigations unveil that the higher substrate temperature improves the microstructure of the thin films. It is revealed that the NiO thin films deposited at oxygen partial pressure of 40% and a substrate temperature of 350 °C, showed higher electrical conductivity with p-type characteristics.

Fugacity and concentration gradients in a gravity field

NASA Technical Reports Server (NTRS)

May, C. E.

1986-01-01

Equations are reviewed which show that at equilibrium fugacity and concentration gradients can exist in gravitational fields. At equilibrium, the logarithm of the ratio of the fugacities of a species at two different locations in a gravitational field is proportional to the difference in the heights of the two locations and the molecular weight of the species. An analogous relation holds for the concentration ratios in a multicomponent system. The ratio is calculated for a variety of examples. The kinetics for the general process are derived, and the time required to approach equilibrium is calculated for several systems. The following special topics are discussed: ionic solutions, polymers, multiphase systems, hydrostatic pressure, osmotic pressure, and solubility gradients in a gravity field.

Inclusion of pressure and flow in a new 3D MHD equilibrium code

NASA Astrophysics Data System (ADS)

Raburn, Daniel; Fukuyama, Atsushi

2012-10-01

Flow and nonsymmetric effects can play a large role in plasma equilibria and energy confinement. A concept for such a 3D equilibrium code was developed and presented in 2011. The code is called the Kyoto ITerative Equilibrium Solver (KITES) [1], and the concept is based largely on the PIES code [2]. More recently, the work-in-progress KITES code was used to calculate force-free equilibria. Here, progress and results on the inclusion of pressure and flow in the code are presented. [4pt] [1] Daniel Raburn and Atsushi Fukuyama, Plasma and Fusion Research: Regular Articles, 7:240381 (2012).[0pt] [2] H. S. Greenside, A. H. Reiman, and A. Salas, J. Comput. Phys, 81(1):102-136 (1989).

FastChem: An ultra-fast equilibrium chemistry

NASA Astrophysics Data System (ADS)

Kitzmann, Daniel; Stock, Joachim

2018-04-01

FastChem is an equilibrium chemistry code that calculates the chemical composition of the gas phase for given temperatures and pressures. Written in C++, it is based on a semi-analytic approach, and is optimized for extremely fast and accurate calculations.

Calculating Pressure-Driven Current Near Magnetic Islands for 3D MHD Equilibria

NASA Astrophysics Data System (ADS)

Radhakrishnan, Dhanush; Reiman, Allan

2016-10-01

In general, 3D MHD equilibria in toroidal plasmas do not result in nested pressure surfaces. Instead, islands and chaotic regions appear in the equilibrium. Near small magnetic islands, the pressure varies within the flux surfaces, which has a significant effect on the pressure-driven current, introducing singularities. Previously, the MHD equilibrium current near a magnetic island was calculated, including the effect of ``stellarator symmetry,'' wherein the singular components of the pressure-driven current vanish [A. H. Reiman, Phys. Plasmas 23, 072502 (2016)]. Here we first solve for pressure in a cylindrical plasma from the heat diffusion equation, after adding a helical perturbation. We then numerically calculate the corresponding Pfirsch-Schluter current. At the small island limit, we compare the pressure-driven current with the previously calculated solution, and far from the island, we recover the solution for nested flux surfaces. Lastly, we compute the current for a toroidal plasma for symmetric and non-symmetric geometries.

On the nature of the material surrounding VEGA

NASA Astrophysics Data System (ADS)

Harper, D. A.; Loewenstein, R. F.; Davidson, J. A.

1984-10-01

Observations of Vega at 193 microns indicate that the far-infrared emission from the circumstellar material discovered by IRAS (Aumann et al. 1984) may decline more rapidly than a Planck spectrum at wavelengths greater than 100 microns. This suggests that the emitting particles may be smaller than the millimeter-sized objects proposed by Aumann et al. (1984). Small grains would be driven from the stellar system by radiation pressure, or their orbits would decay as a result of Poynting -Robertson drag. In order to maintain a state of dynamic equilibrium, a continuous supply of new particles would be required. It is hypothesized that the small grains are ejected by sublimation of volatile material from larger comet-like bodies in a partially coalesced preplanetary disk. A reservoir containing less than a few hundred earth masses could sustain the source over the lifetime of the star.

Adsorption of xenon and krypton on shales

NASA Technical Reports Server (NTRS)

Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

1981-01-01

A method that uses a mass spectrometer as a manometer is employed in the measurement of Xe and Kr adsorption parameters on shales and related samples, where gas partial pressures were lower than 10 to the -11th atm, corresponding adsorption coverages are only small fractions of a monolayer, and Henry's Law behavior is expected and observed. Results show heats of adsorption in the 2-7 kcal/mol range, and Henry constants at 0-25 C of 1 cu cm STP/g per atmosphere are extrapolated. Although the adsorption properties obtained are variable by sample, the range obtained suggests that shales may be capable of an equilibrium adsorption with modern air high enough to account for a significant fraction of the atmospheric inventory of Xe, and perhaps even of Kr. This effect will nevertheless not account for the factor-of-25 defficiency of atmospheric Xe, in comparison with the planetary gas patterns observed in meteorites.

Lunar oxygen production by pyrolysis of regolith

NASA Technical Reports Server (NTRS)

Senior, Constance L.

1991-01-01

Oxygen represents one of the most desirable products of lunar mining and manufacturing. Among the many processes which have been proposed for oxygen production, pyrolysis stands out as one which is uncomplicated and easy to bootstrap. Pyrolysis or vapor-phase reduction involves heating regolith to temperatures sufficient to allow partial decomposition and vaporization. Some metal oxides give up oxygen upon heating, either in the gas phase to form reduced gaseous species or in the condensed phase to form a metallic phase. Based on preliminary experiments and equilibrium calculations, the temperatures needed for pyrolysis are expected to be in the range of 2000 to 2200 K, giving total gas pressures of 0.001 to 0.1 torr. Bulk regolith can be used as a feedstock without beneficiation with concentrated solar radiation supplying most of energy needed. Further, selective condensation of metal-containing species from the gas phase may yield metallic iron and silicon as byproducts.

A combined experimental and computational thermodynamic investigation of the U-Th-O system

DOE PAGES

McMurray, Jake Wesley; Voit, Stewart L.; Besmann, Theodore M.

2016-03-21

Here, the thermodynamics of the U–Th–O system have been assessed using the Calphad method. The compound energy formalism (CEF) and a partially ionic two-sublattice liquid model (TSLM) were used for the fluorite U 1–yTh yO 2±x, γ-(U,Th) 4O 9, and the U–Th–O melt. The O 2 activity of fluorite U 1–yTh yO 2±x with temperature and composition was determined by thermogravimetric analysis. Thermodynamic studies for the Th–O binary and U–Th–O ternary available in the open literature were critically reviewed. A self-consistent data set was selected and compiled with the equilibrium oxygen pressures determined by thermogravimetry in order to optimize themore » adjustable parameters of models selected to represent the phases in the Th–O and U–Th–O systems.« less

Thermodynamic evaluation of oxygen behavior in Ti powder deoxidized by Ca reductant

NASA Astrophysics Data System (ADS)

Kim, Sun-Joong; Oh, Jung-Min; Lim, Jae-Won

2016-07-01

To produce low oxygen Ti powder of less than 1000 mass ppm, commercial Ti powder was deoxidized by two types of Ca reductants: a solid Ca and a Ca vapor. Compared with the iso-oxygen partial pressure in the Ti-O binary phase diagram, the PO2 in the raw Ti powder increased with temperature compared to the reduction reaction of Ca. Therefore, the O2 content in the Ti powder decreased as the deoxidation temperature increased from 873 K, showing a local minima at 1273 K. The oxygen concentration at 1373 K was greater than that at 1273 K because the oxygen solubility of the Ti powder was increased by the equilibrium relation between Ca and CaO. On the basis of the thermodynamic assessment, the deoxidation of Ti powder can be improved by increasing the temperature and lowering the oxygen solubility with the saturation of CaO.

Calibration-free optical chemical sensors

DOEpatents

DeGrandpre, Michael D.

2006-04-11

An apparatus and method for taking absorbance-based chemical measurements are described. In a specific embodiment, an indicator-based pCO₂ (partial pressure of CO₂) sensor displays sensor-to-sensor reproducibility and measurement stability. These qualities are achieved by: 1) renewing the sensing solution, 2) allowing the sensing solution to reach equilibrium with the analyte, and 3) calculating the response from a ratio of the indicator solution absorbances which are determined relative to a blank solution. Careful solution preparation, wavelength calibration, and stray light rejection also contribute to this calibration-free system. Three pCO₂ sensors were calibrated and each had response curves which were essentially identical within the uncertainty of the calibration. Long-term laboratory and field studies showed the response had no drift over extended periods (months). The theoretical response, determined from thermodynamic characterization of the indicator solution, also predicted the observed calibration-free performance.

Water Dimers in the Atmosphere II: Results from the VRT(ASP-W)III Potential Surface

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

Goldman, N; Saykally, R J; Leforestier, C

We report refined results for the equilibrium constant for water dimerization (K{sub P}), computed as a function of temperature via fully-coupled 6-D calculation of the canonical (H{sub 2}O){sub 2} partition function on VRT(ASP-W)III, the most accurate water dimer potential energy surface currently available. Partial pressure isotherms calculated for a range of temperatures and relative humidities indicate that water dimers can exist in sufficient concentrations (e.g., 10{sup 18}m{sup -3} at 30 C and 100% relative humidity) to affect physical and chemical processes in the atmosphere. The determinations of additional thermodynamic properties ({Delta}G, {Delta}H, {Delta}S, C{sub P}, C{sub V}) for (H{sub 2}O){submore » 2} are presented, and the role of quasi-bound states in the calculation of K{sub P} is discussed at length.« less

The determination of density and molecular weight distributions of lipoproteins by sedimentation equilibrium.

PubMed

Jeffrey, P D; Nichol, L W; Smith, G D

1975-01-25

A method is presented by which an experimental record of total concentration as a function of radial distance, obtained in a sedimentation equilibrium experiment conducted with a noninteracting mixture in the absence of a density gradient, may be analyzed to obtain the unimodal distributions of molecular weight and of partial molar volume when these vary concomitantly and continuously. Particular attention is given to the caracterization of classes of lipoproteins exhibiting Gaussian distributions of these quantities, although the analysis is applicable to other types of unimodal distribution. Equations are also formulated permitting the definition of the corresponding distributions of partial specific volume and of density. The analysis procedure is based on a method (employing Laplace transforms) developed previously, but differs from it in that it avoids the necessity of differentiating experimental results, which introduces error. The method offers certain advantages over other procedures used to characterize and compare lipoprotein samples (exhibiting unimodal distributions) with regard to the duration of the experiment, economy of the sample, and, particularly, the ability to define in principle all of the relevant distributions from one sedimentation equilibrium experiment and an external measurement of the weight average partial specific volume. These points and the steps in the analysis procedure are illustrated with experimental results obtained in the sedimentation equilibrium of a sample of human serum low density lipoprotein. The experimental parameters (such as solution density, column height, and angular velocity) used in the conduction of these experiments were selected on the basis of computer-simulated examples, which are also presented. These provide a guide for other workers interested in characterizing lipoproteins of this class.

The defect chemistry of UO2 ± x from atomistic simulations

NASA Astrophysics Data System (ADS)

Cooper, M. W. D.; Murphy, S. T.; Andersson, D. A.

2018-06-01

Control of the defect chemistry in UO2 ± x is important for manipulating nuclear fuel properties and fuel performance. For example, the uranium vacancy concentration is critical for fission gas release and sintering, while all oxygen and uranium defects are known to strongly influence thermal conductivity. Here the point defect concentrations in thermal equilibrium are predicted using defect energies from density functional theory (DFT) and vibrational entropies calculated using empirical potentials. Electrons and holes have been treated in a similar fashion to other charged defects allowing for structural relaxation around the localized electronic defects. Predictions are made for the defect concentrations and non-stoichiometry of UO2 ± x as a function of oxygen partial pressure and temperature. If vibrational entropy is omitted, oxygen interstitials are predicted to be the dominant mechanism of excess oxygen accommodation over only a small temperature range (1265 K-1350 K), in contrast to experimental observation. Conversely, if vibrational entropy is included oxygen interstitials dominate from 1165 K to 1680 K (Busker potential) or from 1275 K to 1630 K (CRG potential). Below these temperature ranges, excess oxygen is predicted to be accommodated by uranium vacancies, while above them the system is hypo-stoichiometric with oxygen deficiency accommodated by oxygen vacancies. Our results are discussed in the context of oxygen clustering, formation of U4O9, and issues for fuel behavior. In particular, the variation of the uranium vacancy concentrations as a function of temperature and oxygen partial pressure will underpin future studies into fission gas diffusivity and broaden the understanding of UO2 ± x sintering.

Oxygen partial pressure effects on the RF sputtered p-type NiO hydrogen gas sensors

NASA Astrophysics Data System (ADS)

Turgut, Erdal; Çoban, Ömer; Sarıtaş, Sevda; Tüzemen, Sebahattin; Yıldırım, Muhammet; Gür, Emre

2018-03-01

NiO thin films were grown by Radio Frequency (RF) Magnetron Sputtering method under different oxygen partial pressures, which are 0.6 mTorr, 1.3 mTorr and 2.0 mTorr. The effects of oxygen partial pressures on the thin films were analyzed through Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Hall measurements. The change in the surface morphology of the thin films has been observed with the SEM and AFM measurements. While nano-pyramids have been obtained on the thin film grown at the lowest oxygen partial pressure, the spherical granules lower than 60 nm in size has been observed for the samples grown at higher oxygen partial pressures. The shift in the dominant XRD peak is realized to the lower two theta angle with increasing the oxygen partial pressures. XPS measurements showed that the Ni2p peak involves satellite peaks and two oxidation states of Ni, Ni2+ and Ni3+, have been existed together with the corresponding splitting in O1s spectrum. P-type conductivity of the grown NiO thin films are confirmed by the Hall measurements with concentrations on the order of 1013 holes/cm-3. Gas sensor measurements revealed minimum of 10% response to the 10 ppm H2 level. Enhanced responsivity of the gas sensor devices of NiO thin films is shown as the oxygen partial pressure increases.

Distribution of gases in the unsaturated zone at a low-level radioactive-waste disposal site near Sheffield, Illinois

USGS Publications Warehouse

Striegl, Robert G.

1988-01-01

The unsaturated zone is a medium that provides pneumatic communication for the movement of gases from wastes buried in landfills to the atmosphere, biota, and groundwater. Gases in unsaturated glacial and eolian deposits near a waste-disposal trench at the low-level radioactive-waste disposal site near Sheffield, Bureau County, Illinois, were identified, and the spatial and temporal distributions of the partial pressures of those gases were determined for the period January 1984 through January 1986. Methods for the collection and analyses of the gases are described, as are geologic and hydrologic characteristics of the unsaturated zone that affect gas transport. The identified gases, which are of natural and of waste origin, include nitrogen, oxygen, and argon, carbon dioxide, methane, propane, butane, tritiated water vapor, 14carbon dioxide, and 222 radon. Concentrations of methane and 14carbon dioxide originated at the waste, as shown by partial-pressure gradients of the gases; 14carbon dioxide partial pressures exceeded natural background partial pressures by factors greater than 1 million at some locations. Variations in partial pressures of oxygen and carbon dioxide were seasonal among piezometers because of increased root and soil-microbe respiration during summer. Variations in methane and 14carbon dioxide partial pressures were apparently related to discrete releases from waste sources at unpredictable intervals of time. No greater than background partial pressures for tritiated water vapor or 222 radon were measured. (USGS)

[Effects of gap junction blocking on the oxygen partial pressure in acupoints of the bladder meridian].

PubMed

Wang, Qi; Yu, Wei-Chang; Jiang, Hong-Zhi; Chen, Sheng-Li; Zhang, Ming-Min; Kong, E-Sheng; Huang, Guang-Ying

2010-12-01

To explore the relation between gap junction and meridian phenomenon. The oxygen partial pressure in acupoints [see text for formula] and in their corresponding non-acupoints of the Bladder Meridian was observed with the needle-type tissue oxygen tension sensor in the gap junction blocking goats by 1-Heptanol injection and the Connexin 43 (Cx43) gene knockout mice. (1) The oxygen partial pressure in acupoints of Bladder Meridian on goats was higher than that in non-acupoints after 1-Heptanol injection with significant differences between them (both P < 0.01). (2) The oxygen partial pressure in acupoints of Bladder Meridian on goats increased significantly after injecting 1-Heptanol as compare with that either injecting normal saline or injecting nothing with significant differences between them (all P < 0.01). (3) The oxygen partial pressure in acupoints of the Bladder Meridian was significantly higher than that in the non-acupoint controls in Cx43 wild type (WT) mice (all P < 0.01). In Cx43 heterozygote (HT) mice, the oxygen partial pressure between acupoints and non-acupoint controls showed no significant differences (all P > 0.05). (4) In acupoints, the oxygen partial pressure in Cx43 WT mice was significantly higher than that in Cx43 HT mice (all P < 0.05), while in the corresponding non-acupoints, this difference had no statistically significant (all P > 0.05). Gap junction maybe the essential factor in signal transduction of acupuncture.

Against the grain: The physical properties of anisotropic partially molten rocks

NASA Astrophysics Data System (ADS)

Ghanbarzadeh, S.; Hesse, M. A.; Prodanovic, M.

2014-12-01

Partially molten rocks commonly develop textures that appear close to textural equilibrium, where the melt network evolves to minimize the energy of the melt-solid interfaces, while maintaining the dihedral angle θ at solid-solid-melt contact lines. Textural equilibrium provides a powerful model for the melt distribution that controls the petro-physical properties of partially molten rocks, e.g., permeability, elastic moduli, and electrical resistivity. We present the first level-set computations of three-dimensional texturally equilibrated melt networks in rocks with an anisotropic fabric. Our results show that anisotropy induces wetting of smaller grain boundary faces for θ > 0 at realistic porosities ϕ < 3%. This was previously not thought to be possible at textural equilibrium and reconciles the theory with experimental observations. Wetting of the grain boundary faces leads to a dramatic redistribution of the melt from the edges to the faces that introduces strong anisotropy in the petro-physical properties such as permeability, effective electrical conductivity and mechanical properties. Figure, on left, shows that smaller grain boundaries become wetted at relatively low melt fractions of 3% in stretched polyhedral grains with elongation factor 1.5. Right plot represents the ratio of melt electrical conductivity to effective conductivity of medium (known as formation factor) as an example of anisotropy in physical properties. The plot shows that even slight anisotropy in grains induces considerable anisotropy in electrical properties.

Effect of stirring on the safety of flammable liquid mixtures.

PubMed

Liaw, Horng-Jang; Gerbaud, Vincent; Chen, Chan-Cheng; Shu, Chi-Min

2010-05-15

Flash point is the most important variable employed to characterize fire and explosion hazard of liquids. The models developed for predicting the flash point of partially miscible mixtures in the literature to date are all based on the assumption of liquid-liquid equilibrium. In real-world environments, however, the liquid-liquid equilibrium assumption does not always hold, such as the collection or accumulation of waste solvents without stirring, where complete stirring for a period of time is usually used to ensure the liquid phases being in equilibrium. This study investigated the effect of stirring on the flash-point behavior of binary partially miscible mixtures. Two series of partially miscible binary mixtures were employed to elucidate the effect of stirring. The first series was aqueous-organic mixtures, including water+1-butanol, water+2-butanol, water+isobutanol, water+1-pentanol, and water+octane; the second series was the mixtures of two flammable solvents, which included methanol+decane, methanol+2,2,4-trimethylpentane, and methanol+octane. Results reveal that for binary aqueous-organic solutions the flash-point values of unstirred mixtures were located between those of the completely stirred mixtures and those of the flammable component. Therefore, risk assessment could be done based on the flammable component flash-point value. However, for the assurance of safety, it is suggested to completely stir those mixtures before handling to reduce the risk. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Effect of stress on the diffusion kinetics of methane during gas desorption in coal matrix under different equilibrium pressures

NASA Astrophysics Data System (ADS)

Li, Chengwu; Xue, Honglai; Hu, Po; Guan, Cheng; Liu, Wenbiao

2018-06-01

Stress has a significant influence on gas diffusion, which is a key factor for methane recovery in coal mines. In this study, a series of experiments were performed to investigate effect of stress on the gas diffusivity during desorption in tectonic coal. Additionally, the desorbed data were modeled using the unipore and bidisperse models. The results show that the bidisperse model better describes the diffusion kinetics than the unipore model in this study. Additionally, the modeling results using the bidisperse approach suggest that the stress impact on the macropore diffusivity is greater than the stress on the micropore diffusivity. Under the same equilibrium pressure, the diffusivity varies with stress according to a four-stage function, which shows an ‘M-shape’. As the equilibrium gas pressure increased from 0.6 to 1.7 MPa, the critical point between stage 2 and stage 3 and between stage 3 and stage 4 transferred to a low stress. This difference is attributed to the gas pressure effects on the physical and mechanical properties of coal. These observations indicate that both the stress and gas pressure can significantly impact gas diffusion and may have significant implications on methane recovery in coal mines.

Understanding the Clausius-Clapeyron Equation by Employing an Easily Adaptable Pressure Cooker

ERIC Educational Resources Information Center

Galleano, Monica; Boveris, Alberto; Puntarulo, Susana

2008-01-01

This article describes a simple and inexpensive laboratory exercise developed to understand the effect of pressure on phase equilibrium as described by the Clausius-Clapeyron equation. The only piece of equipment required is a pressure cooker adapted with a pressure gauge and a thermometer in the lid, allowing the measurement of the pressure and…

Effects of various assumptions on the calculated liquid fraction in isentropic saturated equilibrium expansions

NASA Technical Reports Server (NTRS)

Bursik, J. W.; Hall, R. M.

1980-01-01

The saturated equilibrium expansion approximation for two phase flow often involves ideal-gas and latent-heat assumptions to simplify the solution procedure. This approach is well documented by Wegener and Mack and works best at low pressures where deviations from ideal-gas behavior are small. A thermodynamic expression for liquid mass fraction that is decoupled from the equations of fluid mechanics is used to compare the effects of the various assumptions on nitrogen-gas saturated equilibrium expansion flow starting at 8.81 atm, 2.99 atm, and 0.45 atm, which are conditions representative of transonic cryogenic wind tunnels. For the highest pressure case, the entire set of ideal-gas and latent-heat assumptions are shown to be in error by 62 percent for the values of heat capacity and latent heat. An approximation of the exact, real-gas expression is also developed using a constant, two phase isentropic expansion coefficient which results in an error of only 2 percent for the high pressure case.

Electron density measurement of non-equilibrium atmospheric pressure plasma using dispersion interferometer

NASA Astrophysics Data System (ADS)

Yoshimura, Shinji; Kasahara, Hiroshi; Akiyama, Tsuyoshi

2017-10-01

Medical applications of non-equilibrium atmospheric plasmas have recently been attracting a great deal of attention, where many types of plasma sources have been developed to meet the purposes. For example, plasma-activated medium (PAM), which is now being studied for cancer treatment, has been produced by irradiating non-equilibrium atmospheric pressure plasma with ultrahigh electron density to a culture medium. Meanwhile, in order to measure electron density in magnetic confinement plasmas, a CO2 laser dispersion interferometer has been developed and installed on the Large Helical Device (LHD) at the National Institute for Fusion Science, Japan. The dispersion interferometer has advantages that the measurement is insensitive to mechanical vibrations and changes in neutral gas density. Taking advantage of these properties, we applied the dispersion interferometer to electron density diagnostics of atmospheric pressure plasmas produced by the NU-Global HUMAP-WSAP-50 device, which is used for producing PAM. This study was supported by the Grant of Joint Research by the National Institutes of Natural Sciences (NINS).

Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)

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

Danielson, Thomas; Hin, Celine; Savara, Aditya

Lattice based kinetic Monte Carlo (KMC) simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and for estimating the coverage at a certain pressure. The generalized form has been calculatedmore » by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10-26 to 1013. Finally, the equations have been shown to be general for any value of the adsorption equilibrium constant.« less

Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)

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

Danielson, Thomas; Hin, Celine; Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

Lattice based kinetic Monte Carlo simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and, conversely, for estimating the coverage at a certain pressure. The generalized form has been calculatedmore » by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10{sup −26} to 10{sup 13}. The equations have been shown to be general for any value of the adsorption equilibrium constant.« less

Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)

DOE PAGES

Danielson, Thomas; Hin, Celine; Savara, Aditya

2016-08-10

Lattice based kinetic Monte Carlo (KMC) simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and for estimating the coverage at a certain pressure. The generalized form has been calculatedmore » by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10-26 to 1013. Finally, the equations have been shown to be general for any value of the adsorption equilibrium constant.« less

Development of Highly Durable and Reactive Regenerable Magnesium-Based Sorbents for CO2 Separation in Coal Gasification Process

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

Javad Abbasian; Armin Hassanzadeh Khayyat; Rachid B. Slimane

The specific objective of this project was to develop physically durable and chemically regenerable MgO-based sorbents that can remove carbon dioxide from raw coal gas at operating condition prevailing in IGCC processes. A total of sixty two (62) different sorbents were prepared in this project. The sorbents were prepared either by various sol-gel techniques (22 formulations) or modification of dolomite (40 formulations). The sorbents were prepared in the form of pellets and in granular forms. The solgel based sorbents had very high physical strength, relatively high surface area, and very low average pore diameter. The magnesium content of the sorbentsmore » was estimated to be 4-6 % w/w. To improve the reactivity of the sorbents toward CO{sub 2}, The sorbents were impregnated with potassium salts. The potassium content of the sorbents was about 5%. The dolomite-based sorbents were prepared by calcination of dolomite at various temperature and calcination environment (CO{sub 2} partial pressure and moisture). Potassium carbonate was added to the half-calcined dolomite through wet impregnation method. The estimated potassium content of the impregnated sorbents was in the range of 1-6% w/w. In general, the modified dolomite sorbents have significantly higher magnesium content, larger pore diameter and lower surface area, resulting in significantly higher reactivity compared to the sol-gel sorbents. The reactivities of a number of sorbents toward CO{sub 2} were determined in a Thermogravimetric Analyzer (TGA) unit. The results indicated that at the low CO{sub 2} partial pressures (i.e., 1 atm), the reactivities of the sorbents toward CO{sub 2} are very low. At elevated pressures (i.e., CO{sub 2} partial pressure of 10 bar) the maximum conversion of MgO obtained with the sol-gel based sorbents was about 5%, which corresponds to a maximum CO{sub 2} absorption capacity of less than 1%. The overall capacity of modified dolomite sorbents were at least one order of magnitude higher than those of the sol-gel based sorbents. The results of the tests conducted with various dolomite-based sorbent indicate that the reactivity of the modified dolomite sorbent increases with increasing potassium concentration, while higher calcination temperature adversely affects the sorbent reactivity. Furthermore, the results indicate that as long as the absorption temperature is well below the equilibrium temperature, the reactivity of the sorbent improves with increasing temperature (350-425 C). As the temperature approaches the equilibrium temperature, because of the significant increase in the rate of reverse (i.e., regeneration) reaction, the rate of CO{sub 2} absorption decreases. The results of cyclic tests show that the reactivity of the sorbent gradually decreases in the cyclic process. To improve long-term durability (i.e., reactivity and capacity) of the sorbent, the sorbent was periodically re-impregnated with potassium additive and calcined. The results indicate that, in general, re-treatment improves the performance of the sorbent, and that, the extent of improvement gradually decreases in the cyclic process. The presence of steam significantly enhances the sorbent reactivity and significantly decreases the rate of decline in sorbent deactivation in the cyclic process.« less

Process and system for producing high-density pellets from a gaseous medium

DOEpatents

Foster, Christopher A.

1999-01-01

A process and system for producing pellets of high density carbon dioxide or other gases utilize a chamber containing a plurality of cell-like freezing compartments within which ice is to be formed. A gas desired to be frozen into ice is introduced into the chamber while the internal pressure of the chamber is maintained at a level which is below the equilibrium triple pressure of the gas. The temperature of the freezing compartments is lowered to a temperature which is below the equilibrium vapor pressure temperature of the gas at the chamber pressure so that the gas condenses into ice within the compartments. The temperature of the freezing compartments is thereafter raised so that the ice is thereby released from and falls out of the compartments as pellets for collection.

Rolling Resistance of Tires Measured Under Transient and Equilibrium Conditions on Calspan's Tire Research

DOT National Transportation Integrated Search

1976-03-01

Rolling loss tests were performed on 31 different passenger and 4 light truck tires under transient and equilibrium conditions. The tests were designed to determine the effects of load, speed, inflation pressure, tire temperature, slip angle, torque,...

Dissipative instability in a partially ionised prominence plasma slab

NASA Astrophysics Data System (ADS)

Ballai, I.; Pintér, B.; Oliver, R.; Alexandrou, M.

2017-07-01

Aims: We aim to investigate the nature of dissipative instability appearing in a prominence planar thread filled with partially ionised plasma in the incompressible limit. The importance of partial ionisation is investigated in terms of the ionisation factor and the wavelength of sausage and kink waves propagating in the slab. Methods: In order to highlight the role of partial ionisation, we have constructed models describing various situations we can meet in solar prominence fine structure. Matching the solutions for the transversal component of the velocity and total pressure at the interfaces between the prominence slab and surrounding plasmas, we derived a dispersion relation whose imaginary part describes the evolution of the instability. Results were obtained in the limit of weak dissipation. We have investigated the appearance of instabilities in prominence dark plumes using single and two-fluid approximations. Results: Using simple analytical methods, we show that dissipative instabilities appear for flow speeds that are less than the Kelvin-Helmholtz instability threshold. The onset of instability is determined by the equilibrium flow strength, the ionisation factor of the plasma, the wavelength of waves and the ion-neutral collisional rate. For a given wavelength and for ionisation degrees closer to a neutral gas, the propagating waves become unstable for a narrow band of flow speeds, meaning that neutrals have a stabilising effect. Our results show that the partially ionised plasma describing prominence dark plumes becomes unstable only in a two-fluid (charged particles-neutrals) model, that is for periods that are smaller than the ion-neutral collision time. Conclusions: The present study improves our understanding of the complexity of dynamical processes and stability of solar prominences and the role partial ionisation in destabilising the plasma. We showed the necessity of two-fluid approximation when discussing the nature of instabilities: waves in a single fluid approximation show a great deal of stability. Our results clearly show that the problem of partial ionisation introduces new aspects of plasma stability with consequences on the evolution of partially ionised plasmas and solar prominences, in particular.

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.

Fluctuation Pressure Assisted Ejection of DNA From Bacteriophage

NASA Astrophysics Data System (ADS)

Harrison, Michael J.

2011-03-01

The role of thermal pressure fluctuations excited within tightly packaged DNA while it is ejected from protein capsid shells is discussed in a model calculation. At equilibrium before ejection we assume the DNA is folded many times into a bundle of parallel segments that forms an equilibrium conformation at minimum free energy, which presses tightly against capsid walls. Using a canonical ensemble at temperature T we calculate internal pressure fluctuations against a slowly moving or static capsid mantle for an elastic continuum model of the folded DNA bundle. It is found that fluctuating pressures on the capsid from thermal excitation of longitudinal acoustic vibrations in the bundle whose wavelengths are exceeded by the bend persistence length may have root-mean-square values that are several tens of atmospheres for typically small phage dimensions. Comparisons are given with measured data on three mutants of lambda phage with different base pair lengths and total genome ejection pressures.

A comparison of three algebraic stress closures for combustor flow calculations

NASA Technical Reports Server (NTRS)

Nikjooy, M.; So, R. M. C.; Hwang, B. C.

1985-01-01

A comparison is made of the performance of two locally nonequilibrium and one equilibrium algebraic stress closures in calculating combustor flows. Effects of four different pressure-strain models on these closure models are also analyzed. The results show that the pressure-strain models have a much greater influence on the calculated mean velocity and turbulence field than the algebraic stress closures, and that the best mean strain model for the pressure-strain terms is that proposed by Launder, Reece and Rodi (1975). However, the equilibrium algebraic stress closure with the Rotta return-to-isotropy model (1951) for the pressure-strain terms gives as good a correlation with measurements as when the Launder et al. mean strain model is included in the pressure-strain model. Finally, comparison of the calculations with the standard k-epsilon closure results show that the algebraic stress closures are better suited for simple turbulent flow calculations.

Thermodynamic versus non-equilibrium stability of palmitic acid monolayers in calcium-enriched sea spray aerosol proxy systems.

PubMed

Wellen Rudd, Bethany A; Vidalis, Andrew S; Allen, Heather C

2018-04-16

Of the major cations in seawater (Na+, Mg2+, Ca2+, K+), Ca2+ is found to be the most enriched in fine sea spray aerosols (SSA). In this work, we investigate the binding of Ca2+ to the carboxylic acid headgroup of palmitic acid (PA), a marine-abundant fatty acid, and the impact such binding has on the stability of PA monolayers in both equilibrium and non-equilibrium systems. A range of Ca2+ conditions from 10 μM to 300 mM was utilized to represent the relative concentration of Ca2+ in high and low relative humidity aerosol environments. The CO2- stretching modes of PA detected by surface-sensitive infrared reflection-absorption spectroscopy (IRRAS) reveal ionic binding motifs of the Ca2+ ion to the carboxylate group with varying degrees of hydration. Surface tensiometry was used to determine the thermodynamic equilibrium spreading pressure (ESP) of PA on the various aqueous CaCl2 subphases. Up to concentrations of 1 mM Ca2+, each system reached equilibrium, and Ca2+:PA surface complexation gave rise to a lower energy state revealed by elevated surface pressures relative to water. We show that PA films are not thermodynamically stable at marine aerosol-relevant Ca2+ concentrations ([Ca2+] ≥ 10 mM). IRRAS and vibrational sum frequency generation (VSFG) spectroscopy were used to investigate the surface presence of PA on high concentration Ca2+ aqueous subphases. Non-equilibrium relaxation (NER) experiments were also conducted and monitored by Brewster angle microscopy (BAM) to determine the effect of the Ca2+ ions on PA stability. At high surface pressures, the relaxation mechanisms of PA varied among the systems and were dependent on Ca2+ concentration.

Real-Time Optical Monitoring and Simulations of Gas Phase Kinetics in InN Vapor Phase Epitaxy at High Pressure

NASA Technical Reports Server (NTRS)

Dietz, Nikolaus; Woods, Vincent; McCall, Sonya D.; Bachmann, Klaus J.

2003-01-01

Understanding the kinetics of nucleation and coalescence of heteroepitaxial thin films is a crucial step in controlling a chemical vapor deposition process, since it defines the perfection of the heteroepitaxial film both in terms of extended defect formation and chemical integrity of the interface. The initial nucleation process also defines the film quality during the later stages of film growth. The growth of emerging new materials heterostructures such as InN or In-rich Ga(x)In(1-x)N require deposition methods operating at higher vapor densities due to the high thermal decomposition pressure in these materials. High nitrogen pressure has been demonstrated to suppress thermal decomposition of InN, but has not been applied yet in chemical vapor deposition or etching experiments. Because of the difficulty with maintaining stochiometry at elevated temperature, current knowledge regarding thermodynamic data for InN, e.g., its melting point, temperature-dependent heat capacity, heat and entropy of formation are known with far less accuracy than for InP, InAs and InSb. Also, no information exists regarding the partial pressures of nitrogen and phosphorus along the liquidus surfaces of mixed-anion alloys of InN, of which the InN(x)P(1-x) system is the most interesting option. A miscibility gap is expected for InN(x)P(1-x) pseudobinary solidus compositions, but its extent is not established at this point by experimental studies under near equilibrium conditions. The extension of chemical vapor deposition to elevated pressure is also necessary for retaining stoichiometric single phase surface composition for materials that are characterized by large thermal decomposition pressures at optimum processing temperatures.

Numerical Simulation of Hydraulic Fracturing in Low-/High-Permeability, Quasi-Brittle and Heterogeneous Rocks

NASA Astrophysics Data System (ADS)

Pakzad, R.; Wang, S. Y.; Sloan, S. W.

2018-04-01

In this study, an elastic-brittle-damage constitutive model was incorporated into the coupled fluid/solid analysis of ABAQUS to iteratively calculate the equilibrium effective stress of Biot's theory of consolidation. The Young's modulus, strength and permeability parameter of the material were randomly assigned to the representative volume elements of finite element models following the Weibull distribution function. The hydraulic conductivity of elements was associated with their hydrostatic effective stress and damage level. The steady-state permeability test results for sandstone specimens under different triaxial loading conditions were reproduced by employing the same set of material parameters in coupled transient flow/stress analyses of plane-strain models, thereby indicating the reliability of the numerical model. The influence of heterogeneity on the failure response and the absolute permeability was investigated, and the post-peak permeability was found to decrease with the heterogeneity level in the coupled analysis with transient flow. The proposed model was applied to the plane-strain simulation of the fluid pressurization of a cavity within a large-scale block under different conditions. Regardless of the heterogeneity level, the hydraulically driven fractures propagated perpendicular to the minimum principal far-field stress direction for high-permeability models under anisotropic far-field stress conditions. Scattered damage elements appeared in the models with higher degrees of heterogeneity. The partially saturated areas around propagating fractures were simulated by relating the saturation degree to the negative pore pressure in low-permeability blocks under high pressure. By replicating previously reported trends in the fracture initiation and breakdown pressure for different pressurization rates and hydraulic conductivities, the results showed that the proposed model for hydraulic fracture problems is reliable for a wide range of pressurization rates and permeability conditions.

Novel high pressure hexagonal OsB2 by mechanochemistry

NASA Astrophysics Data System (ADS)

Xie, Zhilin; Graule, Moritz; Orlovskaya, Nina; Andrew Payzant, E.; Cullen, David A.; Blair, Richard G.

2014-07-01

Hexagonal OsB2, a theoretically predicted high-pressure phase, has been synthesized for the first time by a mechanochemical method, i.e., high energy ball milling. X-ray diffraction indicated that formation of hexagonal OsB2 begins after 2.5 h of milling, and the reaction reaches equilibrium after 18 h of milling. Rietveld refinement of the powder data indicated that hexagonal OsB2 crystallizes in the P63/mmc space group (No. 194) with lattice parameters of a=2.916 Å and c=7.376 Å. Transmission electron microscopy confirmed the appearance of the hexagonal OsB2 phase after high energy ball milling. in situ X-ray diffraction experiments showed that the phase is stable from -225 °C to 1050 °C. The hexagonal OsB2 powder was annealed at 1050 °C for 6 days in vacuo to improve crystallinity and remove strain induced during the mechanochemical synthesis. The structure partially converted to the orthorhombic phase (20 wt%) after fast current assisted sintering of hexagonal OsB2 at 1500 °C for 5 min. Mechanochemical approaches to the synthesis of hard boride materials allow new phases to be produced that cannot be prepared using conventional methods.

Thermochemical and kinetic aspects of the sulfurization of Cu-Sb and Cu-Bi thin films

NASA Astrophysics Data System (ADS)

Colombara, Diego; Peter, Laurence M.; Rogers, Keith D.; Hutchings, Kyle

2012-02-01

CuSbS2 and Cu3BiS3 are being investigated as part of a search for new absorber materials for photovoltaic devices. Thin films of these chalcogenides were produced by conversion of stacked and co-electroplated metal precursor layers in the presence of elemental sulfur vapour. Ex-situ XRD and SEM/EDS analyses of the processed samples were employed to study the reaction sequence with the aim of achieving compact layer morphologies. A new “Time-Temperature-Reaction” (TTR) diagram and modified Pilling-Bedworth coefficients have been introduced for the description and interpretation of the reaction kinetics. For equal processing times, the minimum temperature required for CuSbS2 to appear is substantially lower than for Cu3BiS3, suggesting that interdiffusion across the interfaces between the binary sulfides is a key step in the formation of the ternary compounds. The effects of the heating rate and sulfur partial pressure on the phase evolution as well as the potential losses of Sb and Bi during the processes have been investigated experimentally and the results related to the equilibrium pressure diagrams obtained via thermochemical computation.

Pulsatile Flow and Gas Transport of Blood over an Array of Cylinders

NASA Astrophysics Data System (ADS)

Chan, Kit Yan

2005-11-01

In the artificial lung, blood passes through an array of micro-fibers and the gas transfer is strongly dependent on the flow field. The blood flow is unsteady and pulsatile. We have numerically simulated pulsatile flow and gas transfer of blood (modeled as a Casson fluid) over arrays of cylindrical micro-fibers. Oxygen and carbon dioxide are assumed to be in local equilibrium with hemoglobin in blood; and the carbon dioxide facilitated oxygen transport is incorporated into the model by allowing the coupling of carbon dioxide partial pressure and oxygen saturation. The pulsatile flow inputs considered are the sinusoidal and the cardiac waveforms. The squared and staggered arrays of arrangement of the cylinders are considered in this study. Gas transport can be enhanced by: increasing the oscillation frequency; increasing the Reynolds number; increasing the oscillation amplitude; decreasing the void fraction; the use of the cardiac pulsatile input. The overall gas transport is greatly enhanced by the presence of hemoglobin in blood even though the non-Newtonian effect of blood tends to decrease the size and strength of vortices. The pressure drop is also presented as it is an important design parameter confronting the heart.

Simultaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Quinn, Richard

1994-01-01

The Martian regolith is the most substantial volatile reservoir on the planet; it holds CO2 as adsorbate, and can exchange that CO2 with the atmosphere-cap system over timescales of 10(exp 5) to 10(exp 6) years. The climatic response to insolation changes caused by obliquity and eccentricity variations depends in part on the total reservoir of adsorbed CO2. Previous estimates of the adsorbate inventory have been made by measuring the adsorptive behavior of one or more Mars-analyog materials, and deriving an empirical equation that described that adsorption as a function of the partial pressure of CO2 and the temperature of the regolith. The current CO2 inventory is that which satisfies adsorptive equilibrium, observed atmospheric pressure, and no permanent CO2 caps. There is laboratory evidence that H2O poisons the CO2 adsorptive capacity of most materials. No consideration of CO2 - H2O co-adsorption was given in previous estimates of the Martian CO2 inventory, although H2O is present in the vapor phase, and so as adsorbate, throughout the regolith.

The effect of partial portal decompression on portal blood flow and effective hepatic blood flow in man: a prospective study.

PubMed

Rosemurgy, A S; McAllister, E W; Godellas, C V; Goode, S E; Albrink, M H; Fabri, P J

1995-12-01

With the advent of transjugular intrahepatic porta-systemic stent shunt and the wider application of the surgically placed small diameter prosthetic H-graft portacaval shunt (HGPCS), partial portal decompression in the treatment of portal hypertension has received increased attention. The clinical results supporting the use of partial portal decompression are its low incidence of variceal rehemorrhage due to decreased portal pressures and its low rate of hepatic failure, possibly due to maintenance of blood flow to the liver. Surprisingly, nothing is known about changes in portal hemodynamics and effective hepatic blood flow following partial portal decompression. To prospectively evaluate changes in portal hemodynamics and effective hepatic blood flow brought about by partial portal decompression, the following were determined in seven patients undergoing HGPCS: intraoperative pre- and postshunt portal vein pressures and portal vein-inferior vena cava pressure gradients, intraoperative pre- and postshunt portal vein flow, and pre- and postoperative effective hepatic blood flow. With HGPCS, portal vein pressures and portal vein-inferior vena cava pressure gradients decreased significantly, although portal pressures remained above normal. In contrast to the significant decreases in portal pressures, portal vein blood flow and effective hepatic blood flow do not decrease significantly. Changes in portal vein pressures and portal vein-inferior vena cava pressure gradients are great when compared to changes in portal vein flow and effective hepatic blood flow. Reduction of portal hypertension with concomitant maintenance of hepatic blood flow may explain why hepatic dysfunction is avoided following partial portal decompression.

The Effect of Oxygen Partial Pressure on Microstructure and Properties of Fe40Al Alloy Sintered under Vacuum

PubMed Central

Siemiaszko, Dariusz; Kowalska, Beata; Jóźwik, Paweł; Kwiatkowska, Monika

2015-01-01

This paper presents the results of studies on the influence of oxygen partial pressure (vacuum level in the chamber) on the properties of FeAl intermetallics. One of the problems in the application of classical methods of prepared Fe-Al intermetallic is the occurrence of oxides. Applying a vacuum during sintering should reduce this effect. In order to analyze the effect of oxygen partial pressure on sample properties, five samples were processed (by a pressure-assisted induction sintering—PAIS method) under the following pressures: 3, 8, 30, 80, and 300 mbar (corresponding to oxygen partial pressures of 0.63, 1.68, 6.3, 16.8, and 63 mbar, respectively). The chemical and phase composition, hardness, density, and microstructure observations indicate that applying a vacuum significantly impacts intermetallic samples. The compact sintered at pressure 3 mbar is characterized by the most homogeneous microstructure, the highest density, high hardness, and nearly homogeneous chemical composition. PMID:28788015

Unitarity limits on the mass and radius of dark matter particles

NASA Technical Reports Server (NTRS)

Griest, Kim; Kamionkowski, Marc

1989-01-01

Using partial wave unitarity and the observed density of the Universe, it is show that a stable elementary particle which was once in thermal equilibrium cannot have a mass greater than 340 TeV. An extended object which was once in thermal equilibrium cannot have a radius less than 7.5 x 10(exp -7) fm. A lower limit to the relic abundance of such particles is also found.

Understand rotating isothermal collapses yet

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

Tohline, J.E.

1985-01-01

A scalar virial equation is used to describe the dynamic properties of equilibrium gas clouds, taking into account the relative effects of surface pressure, rotation, self gravity and internal isothermal pressure. Details concerning the internal structure of the clouds are ignored in order to obtain a globalized analytical expression. The obtained solution to the equation is found to agree with the surface-pressure-dominated model of Stahler (1983), and the rotation-dominated model of Hayashi, Narita, and Miyama (1982). On the basis of the analytical expression of virial equilibrium in the clouds, some of the limiting properties of isothermal clouds are described, andmore » a realistic starting model for cloud collapse is proposed. 18 references.« less

Theoretical performance of liquid hydrogen and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid hydrogen and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion-chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ration of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 364.6 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Theoretical performance of liquid ammonia and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid ammonia and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 311.5 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Dependence of magnetic anisotropy on MgO sputtering pressure in Co20Fe60B20/MgO stacks

NASA Astrophysics Data System (ADS)

Kaidatzis, A.; Serletis, C.; Niarchos, D.

2017-10-01

We investigated the dependence of magnetic anisotropy of Ta/Co20Fe60B20/MgO stacks on the Ar partial pressure during MgO deposition, in the range between 0.5 and 15 mTorr. The stacks are studied before and after annealing at 300°C and it is shown that magnetic anisotropy significantly depends on Ar partial pressure. High pressure results in stacks with very low perpendicular magnetic anisotropy even after annealing, while low pressure results in stacks with perpendicular anisotropy even at the as-deposited state. A monotonic increase of magnetic anisotropy energy is observed as Ar partial pressure is decreased.

Influence of oxygen partial pressure on the microstructural and magnetic properties of Er-doped ZnO thin films

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

Chen, Wei-Bin; Li, Fei; Chen, Hong-Ming

2015-06-15

Er-doped ZnO thin films have been prepared by using inductively coupled plasma enhanced physical vapor deposition at different O{sub 2}:Ar gas flow ratio (R = 0:30, 1:30, 1:15, 1:10 and 1:6). The influence of oxygen partial pressure on the structural, optical and magnetic properties was studied. It is found that an appropriate oxygen partial pressure (R=1:10) can produce the best crystalline quality with a maximum grain size. The internal strain, estimated by fitting the X-ray diffraction peaks, varied with oxygen partial pressure during growth. PL measurements show that plenty of defects, especially zinc vacancy, exist in Er-doped ZnO films. Allmore » the samples show room-temperature ferromagnetism. Importantly, the saturation magnetization exhibits similar dependency on oxygen partial pressure with the internal strain, which indicates that internal strain has an important effect on the magnetic properties of Er-doped ZnO thin films.« less

Evaporation in equilibrium, in vacuum, and in hydrogen gas

NASA Technical Reports Server (NTRS)

Nagahara, Hiroko

1993-01-01

Evaporation experiments were conducted for SiO2 in three different conditions: in equilibrium, in vacuum, and in hydrogen gas. Evaporation rate in vacuum is about two orders of magnitude smaller than that in equilibrium, which is consistent with previous works. The rate in hydrogen gas changes depending on hydrogen pressure. The rate at 10 exp -7 bar of hydrogen pressure is as small as that of free evaporation, but at 10 exp -5 bar of hydrogen pressure it is larger than that in equilibrium. In equilibrium and in vacuum, the evaporation rate is limited by decomposition of SiO2 on the crystal surface, but it is limited by a diffusion process for evaporation in hydrogen gas. Therefore, evaporation rate of minerals in the solar nebula can be shown neither by that in equilibrium nor by that in vacuum. The maximum temperature of the solar nebula at the midplane at 2-3 AU where chondrites are believed to have originated is calculated to be as low as 150 K, 1500 K, or in between them. The temperature is, in any case, not high enough for total evaporation of the interstellar materials. Therefore, evaporation of interstellar materials is one of the most important processes for the origin and fractionation of solid materials. The fundamental process of evaporation of minerals has been intensively studied for these several years. Those experiments were carried out either in equilibrium or in vacuum; however, evaporation in the solar nebula is in hydrogen (and much smaller amount of helium) gas. In order to investigate evaporation rate and compositional (including isotopic) fractionation during evaporation, vaporization experiments for various minerals in various conditions are conducted. At first, SiO2 was adopted for a starting material, because thermochemical data and its nature of congruent vaporization are well known. Experiments were carried out in a vacuum furnace system.

Equilibrium chemical reaction of supersonic hydrogen-air jets (the ALMA computer program)

NASA Technical Reports Server (NTRS)

Elghobashi, S.

1977-01-01

The ALMA (axi-symmetrical lateral momentum analyzer) program is concerned with the computation of two dimensional coaxial jets with large lateral pressure gradients. The jets may be free or confined, laminar or turbulent, reacting or non-reacting. Reaction chemistry is equilibrium.

CFD simulation of a miniature coaxial Stirling-type pulse tube cryocooler operating at 128 Hz

NASA Astrophysics Data System (ADS)

Zhao, Yibo; Dang, Haizheng

2016-01-01

A two-dimensional axis-symmetric CFD model of a miniature coaxial Stirling-type pulse tube cryocooler with an overall weight of 920 g operating at 128 Hz is established, and systematic simulations of the performance characteristics at different temperatures are conducted. Both thermal equilibrium and non-equilibrium mechanisms for the porous matrix are considered, and the regenerator losses including the gas and solid conduction, the pressure drop and the imperfect interfacial heat transfer are calculated, respectively. The results indicate that the pressure drop loss is dominant during the first 85% and 78% of regenerator length for the thermal equilibrium and non-equilibrium models, respectively, and it decreases monotonously from warm to cold end due to the steadily decreasing Darcy and Forchheimer terms, whereas other entropy generations share similar changing tendencies, going up gradually near the warm end, increasing dramatically from about 60% of length and then decreasing sharply near the cold end. The reasons for these entropy variations are discussed.

TEA: A Code Calculating Thermochemical Equilibrium Abundances

NASA Astrophysics Data System (ADS)

Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver

2016-07-01

We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature-pressure pairs. We tested the code against the method of Burrows & Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows & Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

TEA: A CODE CALCULATING THERMOCHEMICAL EQUILIBRIUM ABUNDANCES

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

Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver, E-mail: jasmina@physics.ucf.edu

2016-07-01

We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows and Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows and Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but withmore » higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.« less

Real Time Computation of Kinetic Constraints to Support Equilibrium Reconstruction

NASA Astrophysics Data System (ADS)

Eggert, W. J.; Kolemen, E.; Eldon, D.

2016-10-01

A new method for quickly and automatically applying kinetic constraints to EFIT equilibrium reconstructions using readily available data is presented. The ultimate goal is to produce kinetic equilibrium reconstructions in real time and use them to constrain the DCON stability code as part of a disruption avoidance scheme. A first effort presented here replaces CPU-time expensive modules, such as the fast ion pressure profile calculation, with a simplified model. We show with a DIII-D database analysis that we can achieve reasonable predictions for selected applications by modeling the fast ion pressure profile and determining the fit parameters as functions of easily measured quantities including neutron rate and electron temperature on axis. Secondly, we present a strategy for treating Thomson scattering and Charge Exchange Recombination data to automatically form constraints for a kinetic equilibrium reconstruction, a process that historically was performed by hand. Work supported by US DOE DE-AC02-09CH11466 and DE-FC02-04ER54698.

Effects of oxygen partial pressure on Li-air battery performance

NASA Astrophysics Data System (ADS)

Kwon, Hyuk Jae; Lee, Heung Chan; Ko, Jeongsik; Jung, In Sun; Lee, Hyun Chul; Lee, Hyunpyo; Kim, Mokwon; Lee, Dong Joon; Kim, Hyunjin; Kim, Tae Young; Im, Dongmin

2017-10-01

For application in electric vehicles (EVs), the Li-air battery system needs an air intake system to supply dry oxygen at controlled concentration and feeding rate as the cathode active material. To facilitate the design of such air intake systems, we have investigated the effects of oxygen partial pressure (≤1 atm) on the performance of the Li-air cell, which has not been systematically examined. The amounts of consumed O2 and evolved CO2 from the Li-air cell are measured with a custom in situ differential electrochemical gas chromatography-mass spectrometry (DEGC-MS). The amounts of consumed O2 suggest that the oxygen partial pressure does not affect the reaction mechanism during discharge, and the two-electron reaction occurs under all test conditions. On the other hand, the charging behavior varies by the oxygen partial pressure. The highest O2 evolution ratio is attained under 70% O2, along with the lowest CO2 evolution. The cell cycle life also peaks at 70% O2 condition. Overall, an oxygen partial pressure of about 0.5-0.7 atm maximizes the Li-air cell capacity and stability at 1 atm condition. The findings here indicate that the appropriate oxygen partial pressure can be a key factor when developing practical Li-air battery systems.

An Evolutionary Comparison of the Handicap Principle and Hybrid Equilibrium Theories of Signaling.

PubMed

Kane, Patrick; Zollman, Kevin J S

2015-01-01

The handicap principle has come under significant challenge both from empirical studies and from theoretical work. As a result, a number of alternative explanations for honest signaling have been proposed. This paper compares the evolutionary plausibility of one such alternative, the "hybrid equilibrium," to the handicap principle. We utilize computer simulations to compare these two theories as they are instantiated in Maynard Smith's Sir Philip Sidney game. We conclude that, when both types of communication are possible, evolution is unlikely to lead to handicap signaling and is far more likely to result in the partially honest signaling predicted by hybrid equilibrium theory.

Linear and nonlinear stability criteria for compressible MHD flows in a gravitational field

NASA Astrophysics Data System (ADS)

Moawad, S. M.; Moawad

2013-10-01

The equilibrium and stability properties of ideal magnetohydrodynamics (MHD) of compressible flow in a gravitational field with a translational symmetry are investigated. Variational principles for the steady-state equations are formulated. The MHD equilibrium equations are obtained as critical points of a conserved Lyapunov functional. This functional consists of the sum of the total energy, the mass, the circulation along field lines (cross helicity), the momentum, and the magnetic helicity. In the unperturbed case, the equilibrium states satisfy a nonlinear second-order partial differential equation (PDE) associated with hydrodynamic Bernoulli law. The PDE can be an elliptic or a parabolic equation depending on increasing the poloidal flow speed. Linear and nonlinear Lyapunov stability conditions under translational symmetric perturbations are established for the equilibrium states.

Partial Reform Equilibrium in Russia: A Case Study of the Political Interests of and in the Russian Gas and Oil Industry

NASA Astrophysics Data System (ADS)

Everett, Rabekah

While several theories abound that attempt to explain the obstacles to democracy in Russia, Joel Hellman's partial reform equilibrium model is an institutional theory that illustrates how weak institutions, combined with an instrumentalist cultural approach to the law and authoritarian-minded leadership, allowed the struggle over interests to craft and determine the nature of Russia's political structure. This thesis builds on the work of Hellman by using the partial reform theory to understand the evolution of interest infiltration and their impact on the formation of policies and institutions in favour of the elites or winners from 2004 to the present time period that allow them to wield law as a political weapon. The hypothesis posits that through their vested interests in state politics, the political and economic elites of the oil and gas industry have successfully stalled reform in Russia resulting in partial reform equilibrium. This is illustrated in a case study that was designed to collect the names, backgrounds, and social networks of gas and oil executives in order to determine how many of them have a history of, or are currently working as, ministers in the government or representatives in the Federation Council. The objective being to measure the degree to which gas and oil interests are present in government decision-making and conversely, the degree to which the government is present in the gas and oil industry. The thesis stresses the importance of institutional structure in determining Russia's political evolution, and uses vested interests as a primary source of structural institutional change, while also stressing on the social and international implications of this evolution.

Magnetar giant flares in multipolar magnetic fields. I. Fully and partially open eruptions of flux ropes

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

Huang, Lei; Yu, Cong, E-mail: muduri@shao.ac.cn, E-mail: cyu@ynao.ac.cn

2014-04-01

We propose a catastrophic eruption model for the enormous energy release of magnetars during giant flares, in which a toroidal and helically twisted flux rope is embedded within a force-free magnetosphere. The flux rope stays in stable equilibrium states initially and evolves quasi-statically. Upon the loss of equilibrium, the flux rope cannot sustain the stable equilibrium states and erupts catastrophically. During the process, the magnetic energy stored in the magnetosphere is rapidly released as the result of destabilization of global magnetic topology. The magnetospheric energy that could be accumulated is of vital importance for the outbursts of magnetars. We carefullymore » establish the fully open fields and partially open fields for various boundary conditions at the magnetar surface and study the relevant energy thresholds. By investigating the magnetic energy accumulated at the critical catastrophic point, we find that it is possible to drive fully open eruptions for dipole-dominated background fields. Nevertheless, it is hard to generate fully open magnetic eruptions for multipolar background fields. Given the observational importance of the multipolar magnetic fields in the vicinity of the magnetar surface, it would be worthwhile to explore the possibility of the alternative eruption approach in multipolar background fields. Fortunately, we find that flux ropes may give rise to partially open eruptions in the multipolar fields, which involve only partial opening of background fields. The energy release fractions are greater for cases with central-arcaded multipoles than those with central-caved multipoles that emerged in background fields. Eruptions would fail only when the centrally caved multipoles become extremely strong.« less

Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.; Gowda, Vijaya Kumar Malahalli Shankare; Rodriguez, Justin; Matson, Douglas M.

2015-01-01

The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has been recently upgraded with an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, theoretically in the range from 10-36 to 100 bar. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte, which is yttria-stabilized zirconia. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, PID-based current loop, and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects of oxygen partial pressure on the surface tension of undercooled liquid nickel will be analyzed, and the results will be presented. The surface tension will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension will be measured using the oscillating drop method. While undercooled, each sample will be oscillated several times consecutively to investigate how the surface tension behaves with time while at a particular oxygen partial pressure.

Sapwood development in Pinus radiata trees grown for three years at ambient and elevated carbon dioxide partial pressures.

PubMed

Atwell, B J; Henery, M L; Whitehead, D

2003-01-01

Clonal trees of Pinus radiata D. Don were grown in open-top chambers at a field site in New Zealand for 3 years at ambient (37 Pa) or elevated (65 Pa) carbon dioxide (CO2) partial pressure. Nitrogen (N) was supplied to half of the trees in each CO2 treatment, at 15 g N m-2 in the first year and 60 g N m-2 in the subsequent 2 years (high-N treatment). Trees in the low-N treatment were not supplied with N but received the same amount of other nutrients as trees in the high-N treatment. In the first year, stem basal area increased more in trees growing at elevated CO2 partial pressure and high-N supply than in control trees, suggesting a positive interaction between these resources. However, the relative rate of growth became the same across trees in all treatments after 450 days, resulting in trees growing at elevated CO2 partial pressure and high-N supply having larger basal areas than trees in the other treatments. Sapwood N content per unit dry mass was consistently about 0.09% in all treatments, indicating that N status was not suppressed by elevated CO2 partial pressure. Thus, during the first year of growth, an elevated CO2 partial pressure enhanced carbon (C) and N storage in woody stems, but there was no further stimulus to C and N deposition after the first year. The chemical composition of sapwood was unaffected by elevated CO2 partial pressure, indicating that no additional C was sequestered through lignification. However, independent of the treatments, early wood was 13% richer in lignin than late wood. Elevated CO2 partial pressure decreased the proportion of sapwood occupied by the lumina of tracheids by up to 12%, indicating increased sapwood density in response to CO2 enrichment. This effect was probably a result of thicker tracheid walls rather than narrower lumina.

Comparison of fluid neutral models for one-dimensional plasma edge modeling with a finite volume solution of the Boltzmann equation

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

Horsten, N., E-mail: niels.horsten@kuleuven.be; Baelmans, M.; Dekeyser, W.

2016-01-15

We derive fluid neutral approximations for a simplified 1D edge plasma model, suitable to study the neutral behavior close to the target of a nuclear fusion divertor, and compare its solutions to the solution of the corresponding kinetic Boltzmann equation. The plasma is considered as a fixed background extracted from a detached 2D simulation. We show that the Maxwellian equilibrium distribution is already obtained very close to the target, justifying the use of a fluid approximation. We compare three fluid neutral models: (i) a diffusion model; (ii) a pressure-diffusion model (i.e., a combination of a continuity and momentum equation) assumingmore » equal neutral and ion temperatures; and (iii) the pressure-diffusion model coupled to a neutral energy equation taking into account temperature differences between neutrals and ions. Partial reflection of neutrals reaching the boundaries is included in both the kinetic and fluid models. We propose two methods to obtain an incident neutral flux boundary condition for the fluid models: one based on a diffusion approximation and the other assuming a truncated Chapman-Enskog distribution. The pressure-diffusion model predicts the plasma sources very well. The diffusion boundary condition gives slightly better results overall. Although including an energy equation still improves the results, the assumption of equal ion and neutral temperature already gives a very good approximation.« less

Soil-Moisture Retention Curves, Capillary Pressure Curves, and Mercury Porosimetry: A Theoretical and Computational Investigation of the Determination of the Geometric Properties of the Pore Space

NASA Astrophysics Data System (ADS)

Strand, T. E.; Wang, H. F.

2003-12-01

Immiscible displacement protocols have long been used to infer the geometric properties of the void space in granular porous media. The three most commonly used experimental techniques are the measurement of soil-moisture retention curves and relative permeability-capillary pressure-saturation relations, as well as mercury intrusion porosimetry experiments. A coupled theoretical and computational investigation was performed that provides insight into the limitations associated with each technique and quantifies the relationship between experimental observations and the geometric properties of the void space. It is demonstrated that the inference of the pore space geometry from both mercury porosimetry experiments and measurements of capillary pressure curves is influenced by trapping/mobilization phenomena and subject to scaling behavior. In addition, both techniques also assume that the capillary pressure at a location on the meniscus can be approximated by a pressure difference across a region or sample. For example, when performing capillary pressure measurements, the capillary pressure, taken to be the difference between the injected fluid pressure at the inlet and the defending fluid pressure at the outlet, is increased in a series of small steps and the fluid saturation is measured each time the system reaches steady. Regions of defending fluid that become entrapped by the invading fluid can be subsequently mobilized at higher flow rates (capillary pressures), contributing to a scale-dependence of the capillary pressure-saturation curve that complicates the determination of the properties of the pore space. This scale-dependence is particularly problematic for measurements performed at the core scale. Mercury porosimetry experiments are subject to similar limitations. Trapped regions of defending fluid are also present during the measurement of soil-moisture retention curves, but the effects of scaling behavior on the evaluation of the pore space properties from the immiscible displacement structure are much simpler to account for due to the control of mobilization phenomena. Some mobilization may occur due to film flow, but this can be limited by keeping time scales relatively small or exploited at longer time scales in order to quantify the rate of film flow. Computer simulations of gradient-stabilized drainage and imbibition to the (respective) equilibrium positions were performed using a pore-scale modified invasion percolation (MIP) model in order to quantify the relationship between the saturation profile and the geometric properties of the void space. These simulations are similar to the experimental measurement of soil-moisture retention curves. Results show that the equilibrium height and the width of the equilibrium fringe depend on two length scale distributions, one controlling the imbibition equilibrium structure and the other controlling the drainage structure. The equilibrium height is related to the mean value of the appropriate distribution as described by Jurin's law, and the width of the equilibrium fringe scales as a function of a combined parameter, the Bond number, Bo, divided by the coefficient of variation (cov). Simulations also demonstrate that the apparent radius distribution obtained from saturation profiles using direct inversion by Jurin's law is a subset of the actual distribution in the porous medium. The relationship between the apparent and actual radius distributions is quantified in terms of the combined parameter, Bo/cov, and the mean coordination number of the porous medium.

Comparative Measurements of Total Temperature in a Supersonic Turbulent Boundary Layer Using a Conical Equilibrium and Combined Temperature-Pressure Probe

DTIC Science & Technology

1974-07-01

AD/A-002 982 COMPARATIVE MEASUREMENTS CF TOTAL TEMPERATURE IN A SUPERSONIC TURBULENT BOUNDARY LAYER USING A CONICAL EQUILIB- RIUM AND COMBINED...SUPERSONIC TURBULENT BOUNDARY LAYER USING A CONICAL EQUILIORIUM AND COMBINED TEMPERATURE-PRESSURE PROBE H.L.P. Vowt R.E. L" 0H.U. M.i July 1974 NAVAL...1 ~~o iotaPRO eig ature In A Supersonic Turbulent Boundary ____________ Layer Using A Conical Equilibrium and 6. 111111ORWING OR. 0111001117,~t

Crystallization of calcium oxalate dihydrate in a buffered calcium-containing glucose solution by irradiation with non-equilibrium atmospheric pressure plasma

NASA Astrophysics Data System (ADS)

Kurake, Naoyuki; Tanaka, Hiromasa; Ishikawa, Kenji; Nakamura, Kae; Kajiyama, Hiroaki; Kikkawa, Fumitaka; Mizuno, Masaaki; Ikehara, Yuzuru; Hori, Masaru

2017-10-01

Oxalate was synthesized in the glucose solution by irradiation with non-equilibrium atmospheric pressure plasma (NEAPP), in which the NEAPP plume contacted the solution surface, via the generation of several intermediate organic products such as gluconic acid. A thermodynamically unstable phase of calcium oxalate dihydrate crystallized rapidly during incubation of a NEAPP-irradiated glucose solution that contained calcium ions and was buffered at neutral pH. Longer irradiation times increased the growth rate and the number of seed crystals.

Synthesis of calcium oxalate crystals in culture medium irradiated with non-equilibrium atmospheric-pressure plasma

NASA Astrophysics Data System (ADS)

Kurake, Naoyuki; Tanaka, Hiromasa; Ishikawa, Kenji; Nakamura, Kae; Kajiyama, Hiroaki; Kikkawa, Fumitaka; Mizuno, Masaaki; Yamanishi, Yoko; Hori, Masaru

2016-09-01

Octahedral particulates several tens of microns in size were synthesized in a culture medium irradiated through contact with a plume of non-equilibrium atmospheric-pressure plasma (NEAPP). The particulates were identified in the crystalline phase as calcium oxalate dihydrate (COD). The original medium contained constituents such as NaCl, d-glucose, CaCl2, and NaHCO3 but not oxalate or oxalic acid. The oxalate was clearly synthesized and crystallized in the medium as thermodynamically unstable COD crystals after the NEAPP irradiation.

A well-balanced finite volume scheme for the Euler equations with gravitation. The exact preservation of hydrostatic equilibrium with arbitrary entropy stratification

NASA Astrophysics Data System (ADS)

Käppeli, R.; Mishra, S.

2016-03-01

Context. Many problems in astrophysics feature flows which are close to hydrostatic equilibrium. However, standard numerical schemes for compressible hydrodynamics may be deficient in approximating this stationary state, where the pressure gradient is nearly balanced by gravitational forces. Aims: We aim to develop a second-order well-balanced scheme for the Euler equations. The scheme is designed to mimic a discrete version of the hydrostatic balance. It therefore can resolve a discrete hydrostatic equilibrium exactly (up to machine precision) and propagate perturbations, on top of this equilibrium, very accurately. Methods: A local second-order hydrostatic equilibrium preserving pressure reconstruction is developed. Combined with a standard central gravitational source term discretization and numerical fluxes that resolve stationary contact discontinuities exactly, the well-balanced property is achieved. Results: The resulting well-balanced scheme is robust and simple enough to be very easily implemented within any existing computer code that solves time explicitly or implicitly the compressible hydrodynamics equations. We demonstrate the performance of the well-balanced scheme for several astrophysically relevant applications: wave propagation in stellar atmospheres, a toy model for core-collapse supernovae, convection in carbon shell burning, and a realistic proto-neutron star.

Using Dalton's Law of Partial Pressures to Determine the Vapor Pressure of a Volatile Liquid

ERIC Educational Resources Information Center

Hilgeman, Fred R.; Bertrand, Gary; Wilson, Brent

2007-01-01

This experiment, designed for a general chemistry laboratory, illustrates the use of Dalton's law of partial pressures to determine the vapor pressure of a volatile liquid. A predetermined volume of air is injected into a calibrated tube filled with a liquid whose vapor pressure is to be measured. The volume of the liquid displaced is greater than…

Tibiofemoral contact pressures in radial tears of the meniscus treated with all-inside repair, inside-out repair and partial meniscectomy.

PubMed

Zhang, Alan L; Miller, Stephanie L; Coughlin, Dezba G; Lotz, Jeffrey C; Feeley, Brian T

2015-10-01

To test contact pressures in the knee after treatment of a radial meniscus tear with an all-inside meniscal repair technique and compare the results with inside-out repair and partial meniscectomy. Six non-paired cadaveric knees were analyzed with intra-compartment pressures measured at loads of 250 N, 500 N and 1000 N at 0°, eight degrees, 15°, and 30° of knee flexion. Compartmental contact pressures were measured for the intact medial meniscus, radial tear in the posterior horn, all-inside repair using the NovoStitch suture passer device (Ceterix Orthopaedics Inc., Menlo Park, CA), inside-out repair method, and partial meniscectomy. One-way ANOVA was used for statistical analysis. The greatest differences in peak pressures between treatments were observed under 1000 N load at 30° flexion (0.8± (SD) 0.1 MPa (intact meniscus), 0.8± (SD) 0.1 MPa (all-inside), 0.9± (SD) 0.1 MPa (inside-out) and 1.6± (SD) 0.2 MPa (partial meniscectomy)). Treatment with partial meniscectomy resulted in the highest peak pressures compared to all other states (p<0.0001 at each angle). Repair of the radial tear using the all-inside technique as well as the inside-out technique resulted in significantly decreased compartment pressures compared to partial meniscectomies (p<0.0001 at each angle). There were no significant differences between peak pressures in the intact state and after repair with the all-inside or inside-out techniques. An all-inside repair technique using the NovoStitch suture passer can decrease contact pressures for a radial meniscus tear similarly to the inside-out repair technique when compared to partial meniscectomy. This novel arthroscopic suture passer warrants further analysis in the clinical setting as it may be a reliable method for repair of radial meniscal tears through an arthroscopic all-inside technique. Copyright © 2015 Elsevier B.V. All rights reserved.

The influence of participant characteristics on the relationship between cuff pressure and level of blood flow restriction.

PubMed

Hunt, Julie E A; Stodart, Clare; Ferguson, Richard A

2016-07-01

Previous investigations to establish factors influencing the blood flow restriction (BFR) stimulus have determined cuff pressures required for complete arterial occlusion, which does not reflect the partial restriction prescribed for this training technique. This study aimed to establish characteristics that should be accounted for when prescribing cuff pressures required for partial BFR. Fifty participants were subjected to incremental blood flow restriction of the upper and lower limbs by proximal pneumatic cuff inflation. Popliteal and brachial artery diameter, blood velocity and blood flow was assessed with Doppler ultrasound. Height, body mass, limb circumference, muscle-bone cross-sectional area, adipose thickness (AT) and arterial blood pressure were measured and used in different models of hierarchical linear regression to predict the pressure at which 60 % BFR (partial occlusion) occurred. Combined analysis revealed a difference in cuff pressures required to elicit 60 % BFR in the popliteal (111 ± 12 mmHg) and brachial arteries (101 ± 12 mmHg). MAP (r = 0.58) and AT (r = -0.45) were the largest independent determinants of lower and upper body partial occlusion pressures. However, greater variance was explained by upper and lower limb regression models composed of DBP and BMI (48 %), and arm AT and DBP (30 %), respectively. Limb circumference has limited impact on the cuff pressure required for partial blood flow restriction which is in contrast to its recognised relationship with complete arterial occlusion. The majority of the variance in partial occlusion pressure remains unexplained by the predictor variables assessed in the present study.

Vibrational density of states and Lindemann melting law

NASA Astrophysics Data System (ADS)

Luo, Sheng-Nian; Strachan, Alejandro; Swift, Damian C.

2005-05-01

We examine the Lindemann melting law at different pressures using the vibrational density of states (DOS), equilibrium melting curve, and Lindemann parameter δL (fractional root-mean-squared displacement, rmsd, at equilibrium melting) calculated independently from molecular dynamics simulations of the Lennard-Jones system. The DOS is obtained using spectra analysis of atomic velocities and accounts for anharmonicity. The increase of δL with pressure is non-negligible: δL is about 0.116 and 0.145 at ambient and extreme pressures, respectively. If the component of rmsd normal to a reflecting plane as in the Debye-Waller-factor-type measurements using x rays is adopted for δL, these values are about 0.067(±0.002) and 0.084(±0.003), and are comparable with experimental and calculated values for face-centered-cubic elements. We find that the Lindemann relation holds accurately at ambient and high pressures. The non-negligible pressure dependence of δL suggests that caution should be exerted in applying the Lindemann law to obtaining the high pressure melting curve anchored at ambient pressure.

Self-Organization of Blood Pressure Regulation: Experimental Evidence

PubMed Central

Fortrat, Jacques-Olivier; Levrard, Thibaud; Courcinous, Sandrine; Victor, Jacques

2016-01-01

Blood pressure regulation is a prime example of homeostatic regulation. However, some characteristics of the cardiovascular system better match a non-linear self-organized system than a homeostatic one. To determine whether blood pressure regulation is self-organized, we repeated the seminal demonstration of self-organized control of movement, but applied it to the cardiovascular system. We looked for two distinctive features peculiar to self-organization: non-equilibrium phase transitions and hysteresis in their occurrence when the system is challenged. We challenged the cardiovascular system by means of slow, 20-min Tilt-Up and Tilt-Down tilt table tests in random order. We continuously determined the phase between oscillations at the breathing frequency of Total Peripheral Resistances and Heart Rate Variability by means of cross-spectral analysis. We looked for a significant phase drift during these procedures, which signed a non-equilibrium phase transition. We determined at which head-up tilt angle it occurred. We checked that this angle was significantly different between Tilt-Up and Tilt-Down to demonstrate hysteresis. We observed a significant non-equilibrium phase transition in nine healthy volunteers out of 11 with significant hysteresis (48.1 ± 7.5° and 21.8 ± 3.9° during Tilt-Up and Tilt-Down, respectively, p < 0.05). Our study shows experimental evidence of self-organized short-term blood pressure regulation. It provides new insights into blood pressure regulation and its related disorders. PMID:27065880

Titan's Interior Chemical Composition: Possible Important Phase Transitions

NASA Astrophysics Data System (ADS)

Howard, Michael; Fried, L. E.; Khare, B. N.; McKay, C. P.

2008-09-01

We study the interior composition of Titan using thermal chemical equilibrium calculations that are valid to high pressures and temperatures. The equations of state are based on exponential-6 fluid theory and have been validated against experimental data up to a few Mbars in pressure and approximately 20000K in temperature. In addition to CHNO molecules, we account for multi-phases of carbon, water and a variety of metals such as Al and Fe, and their oxides. With these fluid equations of state, chemical equilibrium is calculated for a set of product species. As the temperature and pressure evolves for increasing depth in the interior, the chemical equilibrium shifts. We assume that Titan is initially composed of comet material, which we assume to be solar, except for hydrogen, which we take to be depleted by a factor 1/1000. We find that a significant amount of nitrogen is in the form of N2, rather than NH3. Moreover, above 12 kbars pressure, as is the interior pressure of Titan, a significant amount of the carbon is in the form of graphite, rather than CO2 and CH4. We discuss the implications of these results for understanding the atmospheric and surface composition of Titan. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Vapor-liquid equilibrium thermodynamics of N2 + CH4 - Model and Titan applications

NASA Technical Reports Server (NTRS)

Thompson, W. R.; Zollweg, John A.; Gabis, David H.

1992-01-01

A thermodynamic model is presented for vapor-liquid equilibrium in the N2 + CH4 system, which is implicated in calculations of the Titan tropospheric clouds' vapor-liquid equilibrium thermodynamics. This model imposes constraints on the consistency of experimental equilibrium data, and embodies temperature effects by encompassing enthalpy data; it readily calculates the saturation criteria, condensate composition, and latent heat for a given pressure-temperature profile of the Titan atmosphere. The N2 content of condensate is about half of that computed from Raoult's law, and about 30 percent greater than that computed from Henry's law.

Alumina Volatility in Water Vapor at Elevated Temperatures: Application to Combustion Environments

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Myers, Dwight L.

2003-01-01

The volatility of alumina in high temperature water vapor was determined by measuring weight loss of sapphire coupons at temperatures between 1250 and 1500 C, water vapor partial pressures between 0.15 and 0.68 atm in oxygen, at one atmosphere total pressure, and a gas velocity of 4.4 centimeters per second. The variation of the volatility with water vapor partial pressure was consistent with Al(OH)3(g) formation. The enthalpy of reaction to form Al(OH)3(g) from alumina and water vapor was found to be 210 plus or minus 20 kJ/mol. Surface rearrangement of ground sapphire surfaces increased with water vapor partial pressure, temperature and volatility rate. Recession rates of alumina due to volatility were determined as a function of water vapor partial pressure and temperature to evaluate limits for use of alumina in long term applications in combustion environments.

Non-invasive multiwavelength photoplethysmography under low partial pressure of oxygen.

PubMed

Fang, Yung Chieh; Tai, Cheng-Chi

2016-08-01

A reduction in partial pressure of oxygen in the environment may be caused by a gain in altitude, which reduces the atmospheric pressure; it may also be caused by the carbon dioxide generated from breathing in an enclosed space. Does inhaling oxygen of lower partial pressure affect the oxygen-carrying function of haemoglobin in vivo? This study uses non-invasive multiwavelength photoplethysmography to measure the effects that inhaling this type of oxygen can have on the plethysmography of the appendages of the body (fingertips). The results indicate that under low partial pressure of oxygen, be it the result of a gain in carbon dioxide concentration or altitude, the change in visible light absorption is the biggest for short wavelengths (approximately 620 or 640 nm) near deoxyhaemoglobin, which has higher absorption coefficient. Moreover, increasing carbon dioxide concentration from 5000 to 10,000 ppm doubly reduces the absorption rate of these short wavelengths.

The annealing mechanism of the radiation-induced vacancy-oxygen defect in silicon

NASA Astrophysics Data System (ADS)

Voronkov, V. V.; Falster, R.; Londos, C. A.

2012-06-01

Annealing experiments on the VO defect (the A-centre) produced by radiation in silicon—reported long ago—have been re-examined in order to deduce the two most important properties of VO: its diffusivity and the equilibrium constant for VO dissociation into V + O. The loss rate of VO is accounted for by two major reactions. One is the conventional reaction of the trapping of mobile VO by oxygen, thus producing VO2. The other is an annihilation of vacancies, which coexist in an equilibrium ratio with VO, by radiation-produced interstitial point defects. In some cases, a minor reaction, VO + V, should also be taken into account. The emerging minor defects V2O are also highly mobile. They partially dissociate back and partially get trapped by oxygen producing stable V2O2 defects.

Report on ISS O2 Production, Gas Supply and Partial Pressure Management

NASA Technical Reports Server (NTRS)

Schaezler, Ryan N.; Cook, Anthony J.

2015-01-01

Oxygen is used on International Space Station (ISS) for metabolic support and denitrogenation procedures prior to Extra-Vehicular Activities. Nitrogen is used to maintain total pressure and account for losses associated with leakage and operational losses. Oxygen and nitrogen have been supplied by various visiting vehicles such as the Progress and Shuttle in addition to the on-orbit oxygen production capability. Starting in 2014, new high pressure oxygen/nitrogen tanks are available to launch on commercial cargo vehicles and will replace the high pressure gas source that Shuttle used to provide. To maintain a habitable atmosphere the oxygen and nitrogen partial pressures are controlled between upper and lower bounds. The full range of the allowable partial pressures along with the increased ISS cabin volume are utilized as a buffer allowing days to pass between oxygen production or direct addition of oxygen and nitrogen to the atmosphere from reserves. This paper summarizes the amount of gas supplied and produced from all of the sources and describes past experience of managing partial pressures along with the range of management options available to the ISS.

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

DOE PAGES

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; ...

2018-04-19

Smore » mall 3D perturbations to the magnetic field in DIII-D ( δ B / B ~ 2 × 10 - 4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. Finally, the resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.« less

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

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

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.

Smore » mall 3D perturbations to the magnetic field in DIII-D ( δ B / B ~ 2 × 10 - 4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. Finally, the resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.« less

Constraints on the Parental Melts of Enriched Shergottites from Image Analysis and High Pressure Experiments

NASA Technical Reports Server (NTRS)

Collinet, M.; Medard, E.; Devouard, B.; Peslier, A.

2012-01-01

Martian basalts can be classified in at least two geochemically different families: enriched and depleted shergottites. Enriched shergottites are characterized by higher incompatible element concentrations and initial Sr-87/Sr-86 and lower initial Nd-143/Nd-144 and Hf-176/Hf-177 than depleted shergottites [e.g. 1, 2]. It is now generally admitted that shergottites result from the melting of at least two distinct mantle reservoirs [e.g. 2, 3]. Some of the olivine-phyric shergottites (either depleted or enriched), the most magnesian Martian basalts, could represent primitive melts, which are of considerable interest to constrain mantle sources. Two depleted olivine-phyric shergottites, Yamato (Y) 980459 and Northwest Africa (NWA) 5789, are in equilibrium with their most magnesian olivine (Fig. 1) and their bulk rock compositions are inferred to represent primitive melts [4, 5]. Larkman Nunatak (LAR) 06319 [3, 6, 7] and NWA 1068 [8], the most magnesian enriched basalts, have bulk Mg# that are too high to be in equilibrium with their olivine megacryst cores. Parental melt compositions have been estimated by subtracting the most magnesian olivine from the bulk rock composition, assuming that olivine megacrysts have partially accumulated [3, 9]. However, because this technique does not account for the actual petrography of these meteorites, we used image analysis to study these rocks history, reconstruct their parent magma and understand the nature of olivine megacrysts.

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

NASA Astrophysics Data System (ADS)

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; Sugiyama, L. E.; Ferraro, N. M.; Lyons, B. C.; McKee, G. R.; Paz-Soldan, C.; Wingen, A.; Zeng, L.

2018-05-01

Small 3D perturbations to the magnetic field in DIII-D ( δB /B ˜2 ×10-4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. The resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.

Thermal equation of state of TiC: A synchrotron x-ray diffraction study

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

Yu Xiaohui; National Lab for Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080; Department of Physics, University of Science and Technology of China, Hefei 230026

2010-06-15

The pressure-volume-temperature measurements were carried out for titanium carbide (TiC) at pressures and temperatures up to 8.1 GPa and 1273 K using energy-dispersive synchrotron x-ray diffraction. Thermoelastic parameters were derived for TiC based on a modified high-temperature Birch-Murnaghan equation of state and a thermal pressure approach. With the pressure derivative of the bulk modulus, K{sub 0}{sup '}, fixed at 4.0, we obtain: the ambient bulk modulus K{sub 0}=268(6) GPa, which is comparable to previously reported value; temperature derivative of bulk modulus at constant pressure ({partial_derivative}K{sub T}/{partial_derivative}T){sub P}=-0.026(9) GPa K{sup -1}, volumetric thermal expansivity {alpha}{sub T}(K{sup -1})=a+bT with a=1.62(12)x10{sup -5} K{supmore » -1} and b=1.07(17)x10{sup -8} K{sup -2}, pressure derivative of thermal expansion ({partial_derivative}{alpha}/{partial_derivative}P){sub T}=(-3.62{+-}1.14)x10{sup -7} GPa{sup -1} K{sup -1}, and temperature derivative of bulk modulus at constant volume ({partial_derivative}K{sub T}/{partial_derivative}T){sub V}=-0.015(8) GPa K{sup -1}. These results provide fundamental thermophysical properties for TiC for the first time and are important to theoretical and computational modeling of transition metal carbides.« less

Thermal equation-of-state of TiC: a synchrotron x-ray diffraction study

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

Yu, Xiaohui; Lin, Zhijun; Zhang, Jianzhong

2009-01-01

The pressure (P)-volume (V)-temperature (T) measurements were carried out for titanium carbide at pressures and temperatures up to 8.1 GPa and 1273 K using energy-dispersive synchrotron x-ray diffraction. Thermoelastic parameters were derived for TiC based on a modified high-temperature Birch-Murnaghan equation of state and a thermal-pressure approach. With the pressure derivative of the bulk modulus, K'{sub 0}, fixed at 4.0, we obtain: the ambient bulk modulus K{sub 0} = 268(6) GPa, temperature derivative of bulk modulus at constant pressure ({partial_derivative}K{sub T}/{partial_derivative}T){sub p} = -0.026(9) GPa K{sup -1}, volumetric thermal expansivity a{sub T}(K{sup -1}) = a + bT with a =more » 1.62(12) x 10{sup -5} K{sup -1} and b = 1.07(17) x 10{sup -8} K{sup -2}, pressure derivative of thermal expansion ({partial_derivative}a/{partial_derivative}P){sub T} = (-3.62 {+-} 1.14) x 10{sup -7} GPa{sup -1} K{sup -1}, and temperature derivative of bulk modulus at constant volume ({partial_derivative}K{sub T}/{partial_derivative}T){sub v} = -0.015 (8) GPa K{sup -1}. These results provide fundamental thermo physical properties for TiC and are important to theoretical and computational modeling of transition metal carbides.« less

Effect of O 2 gas partial pressure on structures and dielectric characteristics of rf sputtered ZrO 2 thin films

NASA Astrophysics Data System (ADS)

Ma, C. Y.; Lapostolle, F.; Briois, P.; Zhang, Q. Y.

2007-08-01

Amorphous and polycrystalline zirconium oxide thin films have been deposited by reactive rf magnetron sputtering in a mixed argon/oxygen or pure oxygen atmosphere with no intentional heating of the substrate. The films were characterized by high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and capacitance versus voltage ( C- V) measurements to investigate the variation of structure, surface morphology, thickness of SiO 2-like interfacial layer as well as dielectric characteristics with different oxygen partial pressures. The films deposited at low oxygen partial pressures (less than 15%) are amorphous and dense with a smooth surface. In contrast, the films prepared at an oxygen partial pressure higher than 73% are crystallized with the microstructure changing from the mixture of monoclinic and tetragonal phases to a single monoclinic structure. The film structural transition is believed to be consequences of decrease in the oxygen vacancy concentration in the film and of increase of the energetically neutral particles in the plasma due to an increased oxygen partial pressure. SE measurements showed that significant interfacial SiO 2 growth has taken place above approximately 51%. The best C- V results in terms of relative dielectric constant values are obtained for thin films prepared at an oxygen partial pressure of 15%.

Active Brownian particles near straight or curved walls: Pressure and boundary layers

NASA Astrophysics Data System (ADS)

Duzgun, Ayhan; Selinger, Jonathan V.

2018-03-01

Unlike equilibrium systems, active matter is not governed by the conventional laws of thermodynamics. Through a series of analytic calculations and Langevin dynamics simulations, we explore how systems cross over from equilibrium to active behavior as the activity is increased. In particular, we calculate the profiles of density and orientational order near straight or circular walls and show the characteristic width of the boundary layers. We find a simple relationship between the enhancements of density and pressure near a wall. Based on these results, we determine how the pressure depends on wall curvature and hence make approximate analytic predictions for the motion of curved tracers, as well as the rectification of active particles around small openings in confined geometries.

Resolving Discrepancies in the Measurements of the Interfacial Tension for the CO2 + H2O Mixture by Computer Simulation.

PubMed

Müller, Erich A; Mejía, Andrés

2014-04-03

Literature values regarding the pressure dependence of the interfacial tension of the system of carbon dioxide (CO2) + water (H2O) show an unexplained divergence and scatter at the transition between low-pressure gas-liquid equilibrium and the high-pressure liquid-liquid equilibrium. We employ the Statistical Associating Fluid Theory (SAFT) and canonical molecular dynamics simulations based on the corresponding coarse grained force field to map out the phase diagram of the mixture and the interfacial tension for this system. We showcase how at ambient temperatures a triple point (gas-liquid-liquid) is expected and detail the implications that the appearance of the third phase has on the interfacial tensions of the system.

Gas Exchange of Algae

PubMed Central

Ammann, Elizabeth C. B.; Lynch, Victoria H.

1966-01-01

Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg). PMID:5927028

Oxygen partial pressure influenced structural and optical properties of DC magnetron sputtered ZrO{sub 2} films

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

Kondaiah, P.; Madhavi, V.; Uthanna, S.

2013-02-05

Thin films of zirconium oxide (ZrO{sub 2}) were deposited on (100) p-silicon and quartz substrates by sputtering of metallic zirconium target under different oxygen partial pressures in the range 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa. The effect of oxygen partial pressure on the structural and optical properties of the deposited films was systematically investigated. The deposition rate of the films decreased from 3.3 to 1.83 nm/min with the increase of oxygen partial pressure from 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa respectively. The X-ray diffraction profiles revealed that the films exhibit (111) refection of zirconium oxide in monoclinic phase.more » The optical band gap of the films increased from 5.62 to 5.80 eV and refractive index increased from 2.01 to 2.08 with the increase of oxygen partial pressure from 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa respectively.« less

Equilibrium properties of dense hydrogen isotope gases based on the theory of simple fluids.

PubMed

Kowalczyk, Piotr; MacElroy, J M D

2006-08-03

We present a new method for the prediction of the equilibrium properties of dense gases containing hydrogen isotopes. The proposed approach combines the Feynman-Hibbs effective potential method and a deconvolution scheme introduced by Weeks et al. The resulting equations of state and the chemical potentials as functions of pressure for each of the hydrogen isotope gases depend on a single set of Lennard-Jones parameters. In addition to its simplicity, the proposed method with optimized Lennard-Jones potential parameters accurately describes the equilibrium properties of hydrogen isotope fluids in the regime of moderate temperatures and pressures. The present approach should find applications in the nonlocal density functional theory of inhomogeneous quantum fluids and should also be of particular relevance to hydrogen (clean energy) storage and to the separation of quantum isotopes by novel nanomaterials.

Implementation of Radiation, Ablation, and Free Energy Minimization Modules for Coupled Simulations of Hypersonic Flow

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Johnston, Christopher O.; Thompson, Richard A.

2009-01-01

A description of models and boundary conditions required for coupling radiation and ablation physics to a hypersonic flow simulation is provided. Chemical equilibrium routines for varying elemental mass fraction are required in the flow solver to integrate with the equilibrium chemistry assumption employed in the ablation models. The capability also enables an equilibrium catalytic wall boundary condition in the non-ablating case. The paper focuses on numerical implementation issues using FIRE II, Mars return, and Apollo 4 applications to provide context for discussion. Variable relaxation factors applied to the Jacobian elements of partial equilibrium relations required for convergence are defined. Challenges of strong radiation coupling in a shock capturing algorithm are addressed. Results are presented to show how the current suite of models responds to a wide variety of conditions involving coupled radiation and ablation.

Functional organization of mitotic microtubules. Physical chemistry of the in vivo equilibrium system.

PubMed Central

Inoué, S; Fuseler, J; Salmon, E D; Ellis, G W

1975-01-01

Equilibrium between mitotic microtubules and tubulin is analyzed, using birefringence of mitotic spindle to measure microtubule concentration in vivo. A newly designed temperature-controlled slide and miniature, thermostated hydrostatic pressure chamber permit rapid alteration of temperature and of pressure. Stress birefringence of the windows is minimized, and a system for rapid recording of compensation is incorporated, so that birefringence can be measured to 0.1 nm retardation every few seconds. Both temperature and pressure data yield thermodynamic values (delta H similar to 35 kcal/mol, delta S similar to 120 entropy units [eu], delta V similar to 400 ml/mol of subunit polymerized) consistent with the explanation that polymerization of tubulin is entropy driven and mediated by hydrophobic interactions. Kinetic data suggest pseudo-zero-order polymerization and depolymerization following rapid temperature shifts, and a pseudo-first-order depolymerization during anaphase at constant temperature. The equilibrium properties of the in vivo mitotic microtubules are compared with properties of isolated brain tubules. Images FIGURE 1 FIGURE 2 FIGURE 5 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 19 PMID:1139037

First-principles investigations of equilibrium Ca, Mg, Si and O isotope fractionations between silicate melts and minerals

NASA Astrophysics Data System (ADS)

Qi, Y.; Liu, X.; Kang, J.; He, L.

2017-12-01

Equilibrium isotope fractionation factors are essential for using stable isotope data to study many geosciences processes such as planetary differentiation and mantle evolution. The mass-dependent equilibrium isotope fractionation is primarily controlled by the difference in bond energies triggered by the isotope substitution. With the recent advances in computational capabilities, first-principles calculation has become a reliable tool to investigate equilibrium isotopic fractionations, greatly improving our understanding of the factors controlling isotope fractionations. It is important to understand the isotope fractionation between melts and minerals because magmatism is critical for creating and shaping the Earth. However, because isotope fractionation between melts and minerals is small at high temperature, it is difficult to experimentally calibrate such small signature. Due to the disordered and dynamic character of melts, calculations of equilibrium isotope fractionation of melts are more challenging than that for gaseous molecules or minerals. Here, we apply first-principles molecular dynamics method to calculate equilibrium Ca, Mg, Si, and O isotope fractionations between silicate melts and minerals. Our results show that equilibrium Mg, Si, and O isotope fractionations between olivine and pure Mg2SiO4 melt are close to zero at high temperature (e.g. δ26Mgmelt-ol = 0.03 ± 0.04‰, δ30Simelt-ol = -0.06 ± 0.07‰, δ18Omelt-ol = 0.07‰ ± 0.08 at 1500 K). Equilibrium Ca, Mg, Si, and O isotope fractionations between diopside and basalt melt (67% CaMgSi2O6 + 33% CaAl2Si2O8) are also negligible at high temperature (e.g. δ44/40Camelt-cpx = -0.01 ± 0.02‰, δ26Mgmelt-cpx = -0.05 ± 0.14‰, δ30Simelt-cpx = 0.04 ± 0.04‰, δ18Omelt-cpx = 0.03 ± 0.07‰ at 1500 K). These results are consistent with the observations in natural samples that there is no significant Ca, Mg, Si, and O isotope fractionation during mantle partial melting, demonstrating the reliability of our methods. Thus, our results can be used to understand stable isotope fractionation during partial melting of mantle peridotite or fractional crystallization during magmatic differentiation. The first-principles molecular dynamics method is a promising tool to obtain equilibrium fractionation of more isotope systems for complicate liquids.

An Evolutionary Comparison of the Handicap Principle and Hybrid Equilibrium Theories of Signaling

PubMed Central

Kane, Patrick; Zollman, Kevin J. S.

2015-01-01

The handicap principle has come under significant challenge both from empirical studies and from theoretical work. As a result, a number of alternative explanations for honest signaling have been proposed. This paper compares the evolutionary plausibility of one such alternative, the “hybrid equilibrium,” to the handicap principle. We utilize computer simulations to compare these two theories as they are instantiated in Maynard Smith’s Sir Philip Sidney game. We conclude that, when both types of communication are possible, evolution is unlikely to lead to handicap signaling and is far more likely to result in the partially honest signaling predicted by hybrid equilibrium theory. PMID:26348617

Computational methods for reactive transport modeling: A Gibbs energy minimization approach for multiphase equilibrium calculations

NASA Astrophysics Data System (ADS)

Leal, Allan M. M.; Kulik, Dmitrii A.; Kosakowski, Georg

2016-02-01

We present a numerical method for multiphase chemical equilibrium calculations based on a Gibbs energy minimization approach. The method can accurately and efficiently determine the stable phase assemblage at equilibrium independently of the type of phases and species that constitute the chemical system. We have successfully applied our chemical equilibrium algorithm in reactive transport simulations to demonstrate its effective use in computationally intensive applications. We used FEniCS to solve the governing partial differential equations of mass transport in porous media using finite element methods in unstructured meshes. Our equilibrium calculations were benchmarked with GEMS3K, the numerical kernel of the geochemical package GEMS. This allowed us to compare our results with a well-established Gibbs energy minimization algorithm, as well as their performance on every mesh node, at every time step of the transport simulation. The benchmark shows that our novel chemical equilibrium algorithm is accurate, robust, and efficient for reactive transport applications, and it is an improvement over the Gibbs energy minimization algorithm used in GEMS3K. The proposed chemical equilibrium method has been implemented in Reaktoro, a unified framework for modeling chemically reactive systems, which is now used as an alternative numerical kernel of GEMS.

Scavenging dissolved oxygen via acoustic droplet vaporization.

PubMed

Radhakrishnan, Kirthi; Holland, Christy K; Haworth, Kevin J

2016-07-01

Acoustic droplet vaporization (ADV) of perfluorocarbon emulsions has been explored for diagnostic and therapeutic applications. Previous studies have demonstrated that vaporization of a liquid droplet results in a gas microbubble with a diameter 5-6 times larger than the initial droplet diameter. The expansion factor can increase to a factor of 10 in gassy fluids as a result of air diffusing from the surrounding fluid into the microbubble. This study investigates the potential of this process to serve as an ultrasound-mediated gas scavenging technology. Perfluoropentane droplets diluted in phosphate-buffered saline (PBS) were insonified by a 2 MHz transducer at peak rarefactional pressures lower than and greater than the ADV pressure amplitude threshold in an in vitro flow phantom. The change in dissolved oxygen (DO) of the PBS before and after ADV was measured. A numerical model of gas scavenging, based on conservation of mass and equal partial pressures of gases at equilibrium, was developed. At insonation pressures exceeding the ADV threshold, the DO of air-saturated PBS decreased with increasing insonation pressures, dropping as low as 25% of air saturation within 20s. The decrease in DO of the PBS during ADV was dependent on the volumetric size distribution of the droplets and the fraction of droplets transitioned during ultrasound exposure. Numerically predicted changes in DO from the model agreed with the experimentally measured DO, indicating that concentration gradients can explain this phenomenon. Using computationally modified droplet size distributions that would be suitable for in vivo applications, the DO of the PBS was found to decrease with increasing concentrations. This study demonstrates that ADV can significantly decrease the DO in an aqueous fluid, which may have direct therapeutic applications and should be considered for ADV-based diagnostic or therapeutic applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantification of CO2 generation in sedimentary basins through carbonate/clays reactions with uncertain thermodynamic parameters

NASA Astrophysics Data System (ADS)

Ceriotti, G.; Porta, G. M.; Geloni, C.; Dalla Rosa, M.; Guadagnini, A.

2017-09-01

We develop a methodological framework and mathematical formulation which yields estimates of the uncertainty associated with the amounts of CO2 generated by Carbonate-Clays Reactions (CCR) in large-scale subsurface systems to assist characterization of the main features of this geochemical process. Our approach couples a one-dimensional compaction model, providing the dynamics of the evolution of porosity, temperature and pressure along the vertical direction, with a chemical model able to quantify the partial pressure of CO2 resulting from minerals and pore water interaction. The modeling framework we propose allows (i) estimating the depth at which the source of gases is located and (ii) quantifying the amount of CO2 generated, based on the mineralogy of the sediments involved in the basin formation process. A distinctive objective of the study is the quantification of the way the uncertainty affecting chemical equilibrium constants propagates to model outputs, i.e., the flux of CO2. These parameters are considered as key sources of uncertainty in our modeling approach because temperature and pressure distributions associated with deep burial depths typically fall outside the range of validity of commonly employed geochemical databases and typically used geochemical software. We also analyze the impact of the relative abundancy of primary phases in the sediments on the activation of CCR processes. As a test bed, we consider a computational study where pressure and temperature conditions are representative of those observed in real sedimentary formation. Our results are conducive to the probabilistic assessment of (i) the characteristic pressure and temperature at which CCR leads to generation of CO2 in sedimentary systems, (ii) the order of magnitude of the CO2 generation rate that can be associated with CCR processes.

Scavenging dissolved oxygen via acoustic droplet vaporization

PubMed Central

Radhakrishnan, Kirthi; Holland, Christy K.; Haworth, Kevin J.

2016-01-01

Acoustic droplet vaporization (ADV) of perfluorocarbon emulsions has been explored for diagnostic and therapeutic applications. Previous studies have demonstrated that vaporization of a liquid droplet results in a gas microbubble with a diameter 5 to 6 times larger than the initial droplet diameter. The expansion factor can increase to a factor of 10 in gassy fluids as a result of air diffusing from the surrounding fluid into the microbubble. This study investigates the potential of this process to serve as an ultrasound-mediated gas scavenging technology. Perfluoropentane droplets diluted in phosphate-buffered saline (PBS) were insonified by a 2 MHz transducer at peak rarefactional pressures lower than and greater than the ADV pressure amplitude threshold in an in vitro flow phantom. The change in dissolved oxygen (DO) of the PBS before and after ADV was measured. A numerical model of gas scavenging, based on conservation of mass and equal partial pressures of gases at equilibrium, was developed. At insonation pressures exceeding the ADV threshold, the DO of air-saturated PBS decreased with increasing insonation pressures, dropping as low as 25% of air saturation within 20 s. The decrease in DO of the PBS during ADV was dependent on the volumetric size distribution of the droplets and the fraction of droplets transitioned during ultrasound exposure. Numerically predicted changes in DO from the model agreed with the experimentally measured DO, indicating that concentration gradients can explain this phenomenon. Using computationally modified droplet size distributions that would be suitable for in vivo applications, the DO of the PBS was found to decrease with increasing concentrations. This study demonstrates that ADV can significantly decrease the DO in an aqueous fluid, which may have direct therapeutic applications and should be considered for ADV-based diagnostic or therapeutic applications. PMID:26964964

Effects of hydrogen partial pressure on autotrophic growth and product formation of Acetobacterium woodii.

PubMed

Kantzow, Christina; Weuster-Botz, Dirk

2016-08-01

Low aqueous solubility of the gases for autotrophic fermentations (e.g., hydrogen gas) results in low productivities in bioreactors. A frequently suggested approach to overcome mass transfer limitation is to increase the solubility of the limiting gas in the reaction medium by increasing the partial pressure in the gas phase. An increased inlet hydrogen partial pressure of up to 2.1 bar (total pressure of 3.5 bar) was applied for the autotrophic conversion of hydrogen and carbon dioxide with Acetobacterium woodii in a batch-operated stirred-tank bioreactor with continuous gas supply. Compared to the autotrophic batch process with an inlet hydrogen partial pressure of 0.4 bar (total pressure of 1.0 bar) the final acetate concentration after 3.1 days was reduced to 50 % (29.2 g L(-1) compared to 59.3 g L(-1)), but the final formate concentration was increased by a factor of 18 (7.3 g L(-1) compared to 0.4 g L(-1)). Applying recombinant A. woodii strains overexpressing either genes for enzymes in the methyl branch of the Wood-Ljungdahl pathway or the genes phosphotransacetylase and acetate kinase at an inlet hydrogen partial pressure of 1.4 bar reduced the final formate concentration by up to 40 % and increased the final dry cell mass and acetate concentrations compared to the wild type strain. Solely the overexpression of the two genes for ATP regeneration at the end of the Wood-Ljungdahl pathway resulted in an initial switch off of formate production at increased hydrogen partial pressure until the maximum of the hydrogen uptake rate was reached.

Photosynthetic induction and its diffusional, carboxylation and electron transport processes as affected by CO2 partial pressure, temperature, air humidity and blue irradiance.

PubMed

Kaiser, Elias; Kromdijk, Johannes; Harbinson, Jeremy; Heuvelink, Ep; Marcelis, Leo F M

2017-01-01

Plants depend on photosynthesis for growth. In nature, factors such as temperature, humidity, CO 2 partial pressure, and spectrum and intensity of irradiance often fluctuate. Whereas irradiance intensity is most influential and has been studied in detail, understanding of interactions with other factors is lacking. We tested how photosynthetic induction after dark-light transitions was affected by CO 2 partial pressure (20, 40, 80 Pa), leaf temperatures (15·5, 22·8, 30·5 °C), leaf-to-air vapour pressure deficits (VPD leaf-air ; 0·5, 0·8, 1·6, 2·3 kPa) and blue irradiance (0-20 %) in tomato leaves (Solanum lycopersicum). Rates of photosynthetic induction strongly increased with CO 2 partial pressure, due to increased apparent Rubisco activation rates and reduced diffusional limitations. High leaf temperature produced slightly higher induction rates, and increased intrinsic water use efficiency and diffusional limitation. High VPD leaf-air slowed down induction rates and apparent Rubisco activation and (at 2·3 kPa) induced damped stomatal oscillations. Blue irradiance had no effect. Slower apparent Rubisco activation in elevated VPD leaf-air may be explained by low leaf internal CO 2 partial pressure at the beginning of induction. The environmental factors CO 2 partial pressure, temperature and VPD leaf-air had significant impacts on rates of photosynthetic induction, as well as on underlying diffusional, carboxylation and electron transport processes. Furthermore, maximizing Rubisco activation rates would increase photosynthesis by at most 6-8 % in ambient CO 2 partial pressure (across temperatures and humidities), while maximizing rates of stomatal opening would increase photosynthesis by at most 1-3 %. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Thermodynamic Effect of Platinum Addition to beta-NiAl: An Initial Investigation

NASA Technical Reports Server (NTRS)

2005-01-01

An initial investigation was conducted to determine the effect of platinum addition on the activities of aluminum and nickel in beta-NiAl(Pt) over the temperature range 1354 to 1692 K. These measurements were made with a multiple effusion-cell configured mass spectrometer (multi-cell KEMS). The results of this study show that Pt additions act to decreased alpha(Al) and increased the alpha(Ni) in beta-NiAl(Pt) for constant X(sub Ni)/X(sub Al) approx. = 1.13, while at constant X(sub Al) the affect of Pt on Al is greatly reduced. The measured partial enthalpies of mixing indicate Al-atoms have a strong self interaction while Ni- and Pt-atoms in have similar interactions with Al-atoms. Conversely the binding of Ni-atoms in beta-NiAl decreases with Pt addition independent of Al concentration. These initial results prove the technique can be applied to the Ni-Al-Pt system but more activity measurements are required to fully understand the thermodynamics of this system and how Pt additions improved the scaling behavior of nickel-based superalloys. In addition, with the choice of a suitable oxide material for the effusion-cell, the "closed" isothermal nature of the effusion-cell allows the direct investigation of an alloy-oxide equilibrium which resembles the "local-equilibrium" description of the metal-scale interface observed during high temperature oxidation. It is proposed that with an Al(l) + Al2O3(s) experimental reference state together with the route measurement of the relative partial-pressures of Al(g) and Al2O(g) allows the activities of O and Al2O3 to be determined along with the activities of Ni and Al. These measurements provide a direct method of investigating the thermodynamics of the metal-scale interface of a TGO-scale.

The lagRST Model: A Turbulence Model for Non-Equilibrium Flows

NASA Technical Reports Server (NTRS)

Lillard, Randolph P.; Oliver, A. Brandon; Olsen, Michael E.; Blaisdell, Gregory A.; Lyrintzis, Anastasios S.

2011-01-01

This study presents a new class of turbulence model designed for wall bounded, high Reynolds number flows with separation. The model addresses deficiencies seen in the modeling of nonequilibrium turbulent flows. These flows generally have variable adverse pressure gradients which cause the turbulent quantities to react at a finite rate to changes in the mean flow quantities. This "lag" in the response of the turbulent quantities can t be modeled by most standard turbulence models, which are designed to model equilibrium turbulent boundary layers. The model presented uses a standard 2-equation model as the baseline for turbulent equilibrium calculations, but adds transport equations to account directly for non-equilibrium effects in the Reynolds Stress Tensor (RST) that are seen in large pressure gradients involving shock waves and separation. Comparisons are made to several standard turbulence modeling validation cases, including an incompressible boundary layer (both neutral and adverse pressure gradients), an incompressible mixing layer and a transonic bump flow. In addition, a hypersonic Shock Wave Turbulent Boundary Layer Interaction with separation is assessed along with a transonic capsule flow. Results show a substantial improvement over the baseline models for transonic separated flows. The results are mixed for the SWTBLI flows assessed. Separation predictions are not as good as the baseline models, but the over prediction of the peak heat flux downstream of the reattachment shock that plagues many models is reduced.

Stereo particle image velocimetry of nonequilibrium turbulence relaxation in a supersonic boundary layer

NASA Astrophysics Data System (ADS)

Lapsa, Andrew P.; Dahm, Werner J. A.

2011-01-01

Measurements using stereo particle image velocimetry are presented for a developing turbulent boundary layer in a wind tunnel with a Mach 2.75 free stream. As the boundary layer exits from the tunnel nozzle and moves through the wave-free test section, small initial departures from equilibrium turbulence relax, and the boundary layer develops toward the equilibrium zero-pressure-gradient form. This relaxation process is quantified by comparison of first and second order mean, fluctuation, and gradient statistics to classical inner and outer layer scalings. Simultaneous measurement of all three instantaneous velocity components enables direct assessment of the complete turbulence anisotropy tensor. Profiles of the turbulence Mach number show that, despite the M = 2.75 free stream, the incompressibility relation among spatial gradients in the velocity fluctuations applies. This result is used in constructing various estimates of the measured-dissipation rate, comparisons among which show only remarkably small differences over most of the boundary layer. The resulting measured-dissipation profiles, together with measured profiles of the turbulence kinetic energy and mean-flow gradients, enable an assessment of how the turbulence anisotropy relaxes toward its equilibrium zero-pressure-gradient state. The results suggest that the relaxation of the initially disturbed turbulence anisotropy profile toward its equilibrium zero-pressure-gradient form begins near the upper edge of the boundary layer and propagates downward through the defect layer.

Bulk YBa2Cu3O(x) superconductors through pressurized partial melt growth processing

NASA Technical Reports Server (NTRS)

Hu, S.; Hojaji, H.; Barkatt, A.; Boroomand, M.; Hung, M.; Buechele, A. C.; Thorpe, A. N.; Davis, D. D.; Alterescu, S.

1992-01-01

A novel pressurized partial melt growth process has been developed for producing large pieces of bulk Y-Ba-Cu-O superconductors. During long-time partial melt growth stage, an additional driving force for solidification is obtained by using pressurized oxygen gas. The microstructure and superconducting properties of the resulting samples were investigated. It was found that this new technique can eliminate porosity and inhomogeneity, promote large-scale grain-texturing, and improve interdomain coupling as well.

Tables and charts of equilibrium thermodynamic properties of ammonia for temperatures from 500 to 50,000 K.

NASA Technical Reports Server (NTRS)

Simmonds, A. L.; Miller, C. G., III; Nealy, J. E.

1976-01-01

Equilibrium thermodynamic properties for pure ammonia were generated for a range of temperature from 500 to 50,000 K and pressure from 0.01 to 40 MN/sq m and are presented in tabulated and graphical form. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, specific heat at constant pressure, specific heat at constant volume, isentropic exponent, and species mole fractions. These properties were calculated by the method which is based on minimization of the Gibbs free energy. The data presented herein are for an 18-species ammonia model. Heats of formation and spectroscopic constants used as input data are presented. Comparison of several thermodynamic properties calculated with the present program and a second computer code is performed for a range of pressure and for temperatures up to 30,000 K.

On the non-equilibrium dynamics of cavitation around the underwater projectile in variable motion

NASA Astrophysics Data System (ADS)

Chen, Y.; Lu, C. J.; Li, J.; Chen, X.; Gong, Z. X.

2015-12-01

In this work, the dynamic behavior of the non-equilibrium cavitation occurring around the underwater projectiles navigating with variable speed was numerically and theoretically investigated. The cavity collapse induced by the decelerating motion of the projectiles can be classified into two types: periodic oscillation and damped oscillation. In each type the evolution of the total mass of vapor in cavity are found to have strict correlation with the pressure oscillation in far field. By defining the equivalent radius of cavity, we introduce the specific kinetic energy of collapse and demonstrate that its change-rate is in good agreement with the pressure disturbance. We numerically investigated the influence of angle of attack on the collapse effect. The result shows that when the projectile decelerates, an asymmetric-focusing effect of the pressure induced by collapse occurs on its pressure side. We analytically explained such asymmetric-focusing effect.

Crystal-liquid-vapor equilibrium experiments at high temperature (less than or equal to 1800 C) and low, controlled oxygen and hydrogen pressure (10(-1) to 10(-9) PA)

NASA Technical Reports Server (NTRS)

Mysen, B. O.

1987-01-01

Evidence from carbonaceous chrondrites points to refractory oxides in the system CaO-MgO-Al2O3-TiO2-SiO2-Fe-O as being among the earliest phases to condense from the solar nebula. It is necessary to establish the equilibrium relationships between the relevant crystalline and amorphous phases before the chemical constraints can be meaningfully applied to models of solar system history. Preliminary experiments on earth show that such experiments are feasible. Earth-based experiments suffer from several unavoidable problems. These problems can be overcome by experimentation in the Space Station where the experiments can be conducted under near static pressure conditions and where total pressure equals the sum of controlled hydrogen and oxygen pressures and can be controlled for periods exceeding several hours.

The turbulent boundary layer on a porous plate: An experimental study of the heat transfer behavior with adverse pressure gradients

NASA Technical Reports Server (NTRS)

Blackwell, B. F.; Kays, W. M.; Moffat, R. J.

1972-01-01

An experimental investigation of the heat transfer behavior of the near equilibrium transpired turbulent boundary layer with adverse pressure gradient has been carried out. Stanton numbers were measured by an energy balance on electrically heated plates that form the bottom wall of the wind tunnel. Two adverse pressure gradients were studied. Two types of transpiration boundary conditions were investigated. The concept of an equilibrium thermal boundary layer was introduced. It was found that Stanton number as a function of enthalpy thickness Reynolds number is essentially unaffected by adverse pressure gradient with no transpiration. Shear stress, heat flux, and turbulent Prandtl number profiles were computed from mean temperature and velocity profiles. It was concluded that the turbulent Prandtl number is greater than unity in near the wall and decreases continuously to approximately 0.5 at the free stream.

Acoustic performance of low pressure axial fan rotors with different blade chord length and radial load distribution

NASA Astrophysics Data System (ADS)

Carolus, Thomas

The paper examines the acoustic and aerodynamic performance of low-pressure axial fan rotors with a hub/tip ratio of 0.45. Six rotors were designed for the same working point by means of the well-known airfoil theory. The condition of an equilibrium between the static pressure gradient and the centrifugal forces is maintained. All rotors have unequally spaced blades to diminish tonal noise. The rotors are tested in a short cylindrical housing without guide vanes. All rotors show very similar flux-pressure difference characteristics. The peak efficiency and the noise performance is considerably influenced by the chosen blade design. The aerodynamically and acoustically optimal rotor is the one with the reduced load at the hub and increased load in the tip region under satisfied equilibrium conditions. It runs at the highest aerodynamic efficiency, and its noise spectrum is fairly smooth. The overall sound pressure level of this rotor is up to 8 dB (A) lower compared to the other rotors under consideration.

Reconstruction of Pressure Profile Evolution during Levitated Dipole Experiments

NASA Astrophysics Data System (ADS)

Mauel, M.; Garnier, D.; Boxer, A.; Ellsworth, J.; Kesner, J.

2008-11-01

Magnetic levitation of the LDX superconducting dipole causes significant changes in the measured diamagnetic flux and what appears to be an isotropic plasma pressure profile (p˜p||). This poster describes the reconstruction of plasma current and plasma pressure profiles from external measurements of the equilibrium magnetic field, which vary substantially as a function of time depending upon variations in neutral pressure and multifrequency ECRH power levels. Previous free-boundary reconstructions of plasma equilibrium showed the plasma to be anisotropic and highly peaked at the location of the cyclotron resonance of the microwave heating sources. Reconstructions of the peaked plasma pressures confined by a levitated dipole incorporate the small axial motion of the dipole (±5 mm), time varying levitation coil currents, eddy currents flowing in the vacuum vessel, constant magnetic flux linking the superconductor, and new flux loops located near the hot plasma in order to closely couple to plasma current and dipole current variations. I. Karim, et al., J. Fusion Energy, 26 (2007) 99.

Phase equilibria and geochemical constraints on the petrogenesis of high-Ti picrite from the Paleogene East Greenland flood basalt province

NASA Astrophysics Data System (ADS)

Zhang, Yi-Shen; Hou, Tong; Veksler, Ilya V.; Lesher, Charles E.; Namur, Olivier

2018-02-01

Phase equilibrium experiments have been performed on an extremely high-Ti (5.4 wt.% TiO2) picrite from the base of the Paleogene ( 55 Ma) East Greenland Flood Basalt Province. This sample has a high CaO/Al2O3 ratio (1.14), a steep rare-earth elements (REE) profile, is enriched in incompatible trace elements, and is in chemical equilibrium with highly primitive olivine. This all suggests that the picrite is a near-primary melt that did not suffer major chemical evolution during ascent from the mantle source and through the crust. Near-liquidus phase relations were determined over the pressure range of 1 atm, 1 to 1.5 GPa and at temperatures from 1094 to 1400°C. They provide an important constraint on the petrogenesis of these lavas. The high-Ti picritic melt is multi-saturated with olivine (Ol) + orthopyroxene (Opx) at 1 GPa but has only Ol or Opx on the liquidus at lower and higher pressures, respectively. This indicates the primitive melt was last equilibrated with its mantle source at relatively shallow pressure ( 1 GPa). Melting probably started at 2-3 GPa and the picritic melt was produced by 15-30% melting of the mantle source. Such a degree of partial melting requires a mantle with a high potential temperature (1480-1530˚C). The relatively low CaO content and high FeO/MnO ratios of the most primitive East Greenland picrites, the high Ni content of olivine phenocrysts and the presence of low-Ca pyroxene (i.e., pigeonite) at high pressure in our experiments all suggest that the mantle source contained a major component of garnet pyroxenite. Residual garnet in the source could adequately explain the low Al2O3 content (7.92 wt.%) and steep REE patterns of the picrite sample. However, simple melting of a lherzolitic source, even with a major pyroxenite component, cannot explain the formation of magmas with the very high Ti contents observed in some East Greenland basalts. We therefore propose that magmas highly-enriched in Ti were produced by melting of a metasomatized mantle source containing Ti-enriched amphibole and/or phlogopite.

An interactive computer code for calculation of gas-phase chemical equilibrium (EQLBRM)

NASA Technical Reports Server (NTRS)

Pratt, B. S.; Pratt, D. T.

1984-01-01

A user friendly, menu driven, interactive computer program known as EQLBRM which calculates the adiabatic equilibrium temperature and product composition resulting from the combustion of hydrocarbon fuels with air, at specified constant pressure and enthalpy is discussed. The program is developed primarily as an instructional tool to be run on small computers to allow the user to economically and efficiency explore the effects of varying fuel type, air/fuel ratio, inlet air and/or fuel temperature, and operating pressure on the performance of continuous combustion devices such as gas turbine combustors, Stirling engine burners, and power generation furnaces.

Biomass-derived carbon composites for enrichment of dilute methane from underground coal mines.

PubMed

Bae, Jun-Seok; Jin, Yonggang; Huynh, Chi; Su, Shi

2018-07-01

Ventilation air methane (VAM), which is the main source of greenhouse gas emissions from coal mines, has been a great challenge to deal with due to its huge flow rates and dilute methane levels (typically 0.3-1.0 vol%) with almost 100% humidity. As part of our continuous endeavor to further improve the methane adsorption capacity of carbon composites, this paper presents new carbon composites derived from macadamia nut shells (MNSs) and incorporated with carbon nanotubes (CNTs). These new carbon composites were fabricated in a honeycomb monolithic structure to tolerate dusty environment and to minimize pressure drop. This paper demonstrates the importance of biomass particle size distributions when formed in a composite and methane adsorption capacities at low pressures relevant to VAM levels. The selectivity of methane over nitrogen was about 10.4 at each relevant partial pressure, which was much greater than that (6.5) obtained conventionally (at very low pressures), suggesting that capturing methane in the presence of pre-adsorbed nitrogen would be a practical option. The equilibrium and dynamic performance of biomass-derived carbon composites were enhanced by 30 and 84%, respectively, compared to those of our previous carbon fiber composites. In addition, the presence of moisture in ventilation air resulted in a negligible effect on the dynamic VAM capture performance of the carbon composites, suggesting that our carbon composites have a great potential for site applications at coal mines because the cost and performance of solid adsorbents are critical factors to consider. Copyright © 2018 Elsevier Ltd. All rights reserved.

Local thermodynamic equilibrium for globally disequilibrium open systems under stress

NASA Astrophysics Data System (ADS)

Podladchikov, Yury

2016-04-01

Predictive modeling of far and near equilibrium processes is essential for understanding of patterns formation and for quantifying of natural processes that are never in global equilibrium. Methods of both equilibrium and non-equilibrium thermodynamics are needed and have to be combined. For example, predicting temperature evolution due to heat conduction requires simultaneous use of equilibrium relationship between internal energy and temperature via heat capacity (the caloric equation of state) and disequilibrium relationship between heat flux and temperature gradient. Similarly, modeling of rocks deforming under stress, reactions in system open for the porous fluid flow, or kinetic overstepping of the equilibrium reaction boundary necessarily needs both equilibrium and disequilibrium material properties measured under fundamentally different laboratory conditions. Classical irreversible thermodynamics (CIT) is the well-developed discipline providing the working recipes for the combined application of mutually exclusive experimental data such as density and chemical potential at rest under constant pressure and temperature and viscosity of the flow under stress. Several examples will be presented.

Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen.

PubMed

Buchheit, R G; Schreiner, H R; Doebbler, G F

1966-02-01

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622-627. 1966.-Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically "inert gas" present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar > Ne > He. Nitrogen (N(2)) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He ( approximately 300 atm). With respect to inhibition of growth, the noble gases and N(2) differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O(2)-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases.

An Updated Equilibrium Machine

ERIC Educational Resources Information Center

Schultz, Emeric

2008-01-01

A device that can demonstrate equilibrium, kinetic, and thermodynamic concepts is described. The device consists of a leaf blower attached to a plastic container divided into two chambers by a barrier of variable size and form. Styrofoam balls can be exchanged across the barrier when the leaf blower is turned on and various air pressures are…

Long-range interacting systems in the unconstrained ensemble.

PubMed

Latella, Ivan; Pérez-Madrid, Agustín; Campa, Alessandro; Casetti, Lapo; Ruffo, Stefano

2017-01-01

Completely open systems can exchange heat, work, and matter with the environment. While energy, volume, and number of particles fluctuate under completely open conditions, the equilibrium states of the system, if they exist, can be specified using the temperature, pressure, and chemical potential as control parameters. The unconstrained ensemble is the statistical ensemble describing completely open systems and the replica energy is the appropriate free energy for these control parameters from which the thermodynamics must be derived. It turns out that macroscopic systems with short-range interactions cannot attain equilibrium configurations in the unconstrained ensemble, since temperature, pressure, and chemical potential cannot be taken as a set of independent variables in this case. In contrast, we show that systems with long-range interactions can reach states of thermodynamic equilibrium in the unconstrained ensemble. To illustrate this fact, we consider a modification of the Thirring model and compare the unconstrained ensemble with the canonical and grand-canonical ones: The more the ensemble is constrained by fixing the volume or number of particles, the larger the space of parameters defining the equilibrium configurations.

A CRDS approach to gas phase equilibrium constants: the case of N 2O 4 ↔ 2NO 2 at 283 K

NASA Astrophysics Data System (ADS)

Tuchler, Matthew F.; Schmidt, Kierstin L.; Morgan, Mackenzie

2005-01-01

We report a general technique for determining the gas phase equilibrium constant, KP, of the A ↔ 2C system using cavity ringdown spectroscopy (CRDS). Working at a constant temperature, the absorption of one of the equilibrium species is measured at two different total pressures. KP is determined from the total pressures of the equilibrium mixture and the ratio of the absorptions. Theoretical limits on sensitivity of this technique are described as a function of experimental conditions. We present results from the reaction N 2O 4 ↔ 2NO 2 measured at T = 283 K. KP measured in this experiment, 21 (±5) Torr, is found to be lower than that recommended by the NASA Panel for Data Evaluation, 32 Torr. [S.P. Sander, A.R. Ravishankara, D.M. Golden, C.E. Kolb, M.J. Kurylo, R.E. Huie, V.L. Orkin, M.J. Molina, G.K. Moortgat, B.J. Finlayson-Pitts, Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies. Evaluation No. 14; Jet Propulsion Laboratory, Pasadena, CA, 2003].

Local approximation of a metapopulation's equilibrium.

PubMed

Barbour, A D; McVinish, R; Pollett, P K

2018-04-18

We consider the approximation of the equilibrium of a metapopulation model, in which a finite number of patches are randomly distributed over a bounded subset [Formula: see text] of Euclidean space. The approximation is good when a large number of patches contribute to the colonization pressure on any given unoccupied patch, and when the quality of the patches varies little over the length scale determined by the colonization radius. If this is the case, the equilibrium probability of a patch at z being occupied is shown to be close to [Formula: see text], the equilibrium occupation probability in Levins's model, at any point [Formula: see text] not too close to the boundary, if the local colonization pressure and extinction rates appropriate to z are assumed. The approximation is justified by giving explicit upper and lower bounds for the occupation probabilities, expressed in terms of the model parameters. Since the patches are distributed randomly, the occupation probabilities are also random, and we complement our bounds with explicit bounds on the probability that they are satisfied at all patches simultaneously.

A System for Incubations at High Gas Partial Pressure

PubMed Central

Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

2012-01-01

High-pressure is a key feature of deep subsurface environments. High partial pressure of dissolved gasses plays an important role in microbial metabolism, because thermodynamic feasibility of many reactions depends on the concentration of reactants. For gases, this is controlled by their partial pressure, which can exceed 1 MPa at in situ conditions. Therefore, high hydrostatic pressure alone is not sufficient to recreate true deep subsurface in situ conditions, but the partial pressure of dissolved gasses has to be controlled as well. We developed an incubation system that allows for incubations at hydrostatic pressure up to 60 MPa, temperatures up to 120°C, and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. To keep costs low, the system is mainly made from off-the-shelf components with only very few custom-made parts. A flexible and inert PVDF (polyvinylidene fluoride) incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow-through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g., fluid–gas–rock-interactions in relation to carbon dioxide sequestration. As an application of the system we extracted organic compounds from sub-bituminous coal using H2O as well as a H2O–CO2 mixture at elevated temperature (90°C) and pressure (5 MPa). Subsamples were taken at different time points during the incubation and analyzed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulfate reduction rate upon the addition of methane to the sample. PMID:22347218

Combustion and inorganic bromine emission of waste printed circuit boards in a high temperature furnace

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

Ni Mingjiang, E-mail: xiaohanxi_2@163.com; Xiao Hanxi; Chemistry and Chemical Engineering School, Hunan University of Science and Technology, Xiangtan

2012-03-15

Highlights: Black-Right-Pointing-Pointer The combustion efficiency of waste printed circuit boards (PCBs) depends on temperature, excess air factor, and high temperature zone residence time. Temperature has the most significant impact. Under the proposed condition, combustion of waste PCBs alone is quite complete within the furnace. Black-Right-Pointing-Pointer High temperature prompts a more complete bromine release and conversion. When temperature is high enough, 99.9% organobrominated compounds, the potential precursors for brominated dixoins formation, are destroyed efficiently and convert to inorganic bromine in flue gas, as HBr and Br{sub 2}. Black-Right-Pointing-Pointer Temperature has crucial influence over the inhibition of HBr conversion to Br{sub 2},more » while the oxygen partial pressure plays a reverse role in the conversion to a very small extent. Increasing temperature will decrease the volume percentage ratio of Br{sub 2}/HBr in flue gas greatly. Black-Right-Pointing-Pointer The thermodynamic equilibrium approach of bromine conversion was investigated. The two forms of inorganic bromine in flue gas substantially reach thermodynamic equilibrium within 0.25 s. Under the proposed operating condition, the reaction of Br transfer and conversion finish. - Abstract: High temperature combustion experiments of waste printed circuit boards (PCBs) were conducted using a lab-scale system featuring a continuously-fed drop tube furnace. Combustion efficiency and the occurrence of inorganic bromine (HBr and Br{sub 2}) were systematically studied by monitoring the main combustion products continuously. The influence of furnace temperature (T) was studied from 800 to 1400 Degree-Sign C, the excess air factor (EAF) was varied from 1.2 to 1.9 and the residence time in the high temperature zone (RT{sub HT}) was set at 0.25, 0.5, or 0.75 s. Combustion efficiency depends on temperature, EAF and RT{sub HT}; temperature has the most significant effect. Conversion of organic bromine from flame retardants into HBr and Br{sub 2} depends on temperature and EAF. Temperature has crucial influence over the ratio of HBr to Br{sub 2}, whereas oxygen partial pressure plays a minor role. The two forms of inorganic bromine seem substantially to reach thermodynamic equilibrium within 0.25 s. High temperature is required to improve the combustion performance: at 1200 Degree-Sign C or higher, an EAF of 1.3 or more, and a RT{sub HT} exceeding 0.75 s, combustion is quite complete, the CO concentration in flue gas and remained carbon in ash are sufficiently low, and organobrominated compounds are successfully decomposed (more than 99.9%). According to these results, incineration of waste PCBs without preliminary separation and without additives would perform very well under certain conditions; the potential precursors for brominated dioxins formation could be destroyed efficiently. Increasing temperature could decrease the volume percentage ratio of Br{sub 2}/HBr in flue gas greatly.« less

Thermal Equation of State of TiC: A Synchrotron X-ray Diffraction

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

Yu, X.; Lin, Z; Zhang, J

2010-01-01

The pressure-volume-temperature measurements were carried out for titanium carbide (TiC) at pressures and temperatures up to 8.1 GPa and 1273 K using energy-dispersive synchrotron x-ray diffraction. Thermoelastic parameters were derived for TiC based on a modified high-temperature Birch-Murnaghan equation of state and a thermal pressure approach. With the pressure derivative of the bulk modulus, K{prime}{sub 0}, fixed at 4.0, we obtain: the ambient bulk modulus K{sub 0} = 268(6) GPa, which is comparable to previously reported value; temperature derivative of bulk modulus at constant pressure ({partial_derivative}K{sub T}/{partial_derivative}T){sub P} = -0.026(9) GPa K{sup -1}, volumetric thermal expansivity {alpha}{sub T}(K{sup -1}) =more » a+b T with a = 1.62(12) x 10{sup -5} K{sup -1} and b = 1.07(17) x 10{sup -8}K{sup -2}, pressure derivative of thermal expansion ({partial_derivative}{sub {alpha}}/{partial_derivative}{sub P}){sub T} = (-3.62 {+-} 1.14) x 10{sup -7} GPa{sup -1} K{sup -1}, and temperature derivative of bulk modulus at constant volume ({partial_derivative}K{sub T}/{partial_derivative}T){sub V} = -0.015(8) GPa K{sup -1}. These results provide fundamental thermophysical properties for TiC for the first time and are important to theoretical and computational modeling of transition metal carbides.« less

Resonant behaviour of MHD waves on magnetic flux tubes. III - Effect of equilibrium flow

NASA Technical Reports Server (NTRS)

Goossens, Marcel; Hollweg, Joseph V.; Sakurai, Takashi

1992-01-01

The Hollweg et al. (1990) analysis of MHD surface waves in a stationary equilibrium is extended. The conservation laws and jump conditions at Alfven and slow resonance points obtained by Sakurai et al. (1990) are generalized to include an equilibrium flow, and the assumption that the Eulerian perturbation of total pressure is constant is recovered as the special case of the conservation law for an equilibrium with straight magnetic field lines and flow along the magnetic field lines. It is shown that the conclusions formulated by Hollweg et al. are still valid for the straight cylindrical case. The effect of curvature is examined.

Spatial Characteristics of F/A-18 Vertical Tail Buffet Pressures Measured in Flight

NASA Technical Reports Server (NTRS)

Moses, Robert W.; Shah, Gautam H.

1998-01-01

Buffeting is an aeroelastic phenomenon which plagues high performance aircraft, especially those with twin vertical tails, at high angles of attack. Previous wind-tunnel and flight tests were conducted to characterize the buffet loads on the vertical tails by measuring surface pressures, bending moments, and accelerations. Following these tests, buffeting estimates were computed using the measured buffet pressures and compared to the measured responses. The estimates did not match the measured data because the assumed spatial correlation of the buffet pressures was not correct. A better understanding of the partial (spatial) correlation of the differential buffet pressures on the tail was necessary to improve the buffeting estimates. Several wind-tunnel investigations were conducted for this purpose. When combined and compared, the results of these tests show that the partial correlation depends on and scales with flight conditions. One of the remaining questions is whether the windtunnel data is consistent with flight data. Presented herein, cross-spectra and coherence functions calculated from pressures that were measured on the high alpha research vehicle (HARV) indicate that the partial correlation of the buffet pressures in flight agrees with the partial correlation observed in the wind tunnel.

Correlation of Fin Buffet Pressures on an F/A-18 with Scaled Wind-Tunnel Measurements

NASA Technical Reports Server (NTRS)

Moses, Robert W.; Shah, Gautam H.

1999-01-01

Buffeting is an aeroelastic phenomenon occurring at high angles of attack that plagues high performance aircraft, especially those with twin vertical tails. Previous wind-tunnel and flight tests were conducted to characterize the buffet loads on the vertical tails by measuring surface pressures, bending moments, and accelerations. Following these tests, buffeting responses were computed using the measured buffet pressures and compared to the measured buffeting responses. The calculated results did not match the measured data because the assumed spatial correlation of the buffet pressures was not correct. A better understanding of the partial (spatial) correlation of the differential buffet pressures on the tail was necessary to improve the buffeting predictions. Several wind-tunnel investigations were conducted for this purpose. When compared, the results of these tests show that the partial correlation scales with flight conditions. One of the remaining questions is whether the wind-tunnel data is consistent with flight data. Presented herein, cross-spectra and coherence functions calculated from pressures that were measured on the High Alpha Research Vehicle indicate that the partial correlation of the buffet pressures in flight agrees with the partial correlation observed in the wind tunnel.

Equilibrium Partitioning Sediment Guidelines (ESGs) for the ...

EPA Pesticide Factsheets

... PLC = partial life-cycle ... 5 ii mini iiiiiiiii iiiiiii mi 1 1 iii mini ii i B : - Benthic vs WQC i— w ~_ ~ _ o° _ -0 ° - - - ii mini iiiiiiiii iiiiiii iiiiiiiii mini ii 0.1 ... PhD thesis. ...

Bulk viscosity of the Lennard-Jones fluid for a wide range of states computed by equilibrium molecular dynamics

NASA Astrophysics Data System (ADS)

Hoheisel, C.; Vogelsang, R.; Schoen, M.

1987-12-01

Accurate data for the bulk viscosity ηv have been obtained by molecular dynamics calculations. Many thermodynamic states of the Lennard-Jones fluid were considered. The Green-Kubo integrand of ηv is analyzed in terms of partial correlation functions constituting the total one. These partial functions behave rather differently from those found for the shear viscosity or the thermal conductivity. Generally the total autocorrelation function of ηv shows a steeper initial decay and a more pronounced long time form than those of the shear viscosity or the thermal conductivity. For states near transition to solid phases, like the pseudotriple point of argon, the Green-Kubo integrand of ηv has a significantly longer ranged time behavior than that of the shear viscosity. Hence, for the latter states, a systematic error is expected for ηv using equilibrium molecular dynamics for its computation.

Local equilibrium of mafic enclaves and granitoids of the Turtle pluton, southeast California: Mineral, chemical, and isotopic evidence

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

Allen, C.M.

Major element and trace element compositions of whole rocks, mineral compositions, and Rb-Sr isotopic compositions of enclave and host granitoid pairs from the Early Cretaceous, calc-alkaline Turtle pluton of southeastern California suggest that the local environmental profoundly affects some enclave types. In the Turtle pluton, where the source of fine-grained, mafic enclaves can be deduced to be magmatic by the presence of partially disaggregated basaltic dikes, mineral chemistry suggests partial or complete local equilibrium among mineral species in the enclave and its host granitoid. Because of local Rb-Sr isotopic equilibration between fine-grained enclaves and host granitoid, one cannot use Srmore » isotopes to distinguish an enclave source independent of its host rocks from an enclave source related to the enclosing pluton. However, preliminary Nd isotopic data suggest an independent, mantle source for enclaves.« less

Non-equilibrium surface tension of the vapour-liquid interface of active Lennard-Jones particles

NASA Astrophysics Data System (ADS)

Paliwal, Siddharth; Prymidis, Vasileios; Filion, Laura; Dijkstra, Marjolein

2017-08-01

We study a three-dimensional system of self-propelled Brownian particles interacting via the Lennard-Jones potential. Using Brownian dynamics simulations in an elongated simulation box, we investigate the steady states of vapour-liquid phase coexistence of active Lennard-Jones particles with planar interfaces. We measure the normal and tangential components of the pressure tensor along the direction perpendicular to the interface and verify mechanical equilibrium of the two coexisting phases. In addition, we determine the non-equilibrium interfacial tension by integrating the difference of the normal and tangential components of the pressure tensor and show that the surface tension as a function of strength of particle attractions is well fitted by simple power laws. Finally, we measure the interfacial stiffness using capillary wave theory and the equipartition theorem and find a simple linear relation between surface tension and interfacial stiffness with a proportionality constant characterized by an effective temperature.

Nucleation theory without Maxwell demons

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

Katz, J.L.; Wiedersich, H.

1977-09-01

The equations for steady-state nucleation are derived from the rates of growth and decay of clusters with emphasis on a clear distinction between thermodynamic quantities and inherently kinetic quantities. It is shown that the emission rates of molecules from embryos can be related to the equilibrium size distribution of clusters in a saturated vapor. It is therefore not necessary to invoke the existence of an embryo size distribution constrained be in equilibrium with a supersaturated vapor. The driving force for nucleation is shown to be a kinetic quantity called the condensation rate ratio, i.e., the ratio of the rates ofmore » acquisition of molecules by clusters in the supersaturated vapor to that in a saturated vapor at the same temperature, and not a thermodynamic quantity known as the supersaturation, i.e., the ratio of the actual pressure to the equilibrium vapor pressure.« less

Nonlinear dynamics of confined thin liquid-vapor bilayer systems with phase change

NASA Astrophysics Data System (ADS)

Kanatani, Kentaro; Oron, Alexander

2011-03-01

We numerically investigate the nonlinear evolution of the interface of a thin liquid-vapor bilayer system confined by rigid horizontal walls from both below and above. The lateral variation of the vapor pressure arising from phase change is taken into account in the present analysis. When the liquid (vapor) is heated (cooled) and gravity acts toward the liquid, the deflection of the interface monotonically grows, leading to a rupture of the vapor layer, whereas nonruptured stationary states are found when the liquid (vapor) is cooled (heated) and gravity acts toward the vapor. In the latter case, vapor-flow-driven convective cells are found in the liquid phase in the stationary state. The average vapor pressure and interface temperature deviate from their equilibrium values once the interface departs from the flat equilibrium state. Thermocapillarity does not have a significant effect near the thermodynamic equilibrium, but becomes important if the system significantly deviates from it.

On the equilibrium structures of self-gravitating masses of gas containing axisymmetric magnetic fields

NASA Technical Reports Server (NTRS)

Lerche, I.; Low, B. C.

1980-01-01

The general equations describing the equilibrium shapes of self-gravitating gas clouds containing axisymmetric magnetic fields are presented. The general equations admit of a large class of solutions. It is shown that if one additional (ad hoc) asumption is made that the mass be spherically symmetrically distributed, then the gas pressure and the boundary conditions are sufficiently constraining that the general topological structure of the solution is effectively determined. The further assumption of isothermal conditions for this case demands that all solutions possess force-free axisymmetric magnetic fields. It is also shown how the construction of aspherical (but axisymmetric) configurations can be achieved in some special cases, and it is demonstrated that the detailed form of the possible equilibrium shapes depends upon the arbitrary choice of the functional form of the variation of the gas pressure along the field lines.

Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05

USGS Publications Warehouse

Iverson, R.M.; Dzurisin, D.; Gardner, C.A.; Gerlach, T.M.; LaHusen, R.G.; Lisowski, M.; Major, J.J.; Malone, S.D.; Messerich, J.A.; Moran, S.C.; Pallister, J.S.; Qamar, A.I.; Schilling, S.P.; Vallance, J.W.

2006-01-01

The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption. ??2006 Nature Publishing Group.

Automatic procedure for stable tetragonal or hexagonal structures: application to tetragonal Y and Cd

NASA Astrophysics Data System (ADS)

Marcus, P. M.; Jona, F.

2005-05-01

A simple effective procedure (MNP) for finding equilibrium tetragonal and hexagonal states under pressure is described and applied. The MNP procedure finds a path to minima of the Gibbs free energy G at T=0 K (G=E+pV, E=energy per atom, p=pressure, V=volume per atom) for tetragonal and hexagonal structures by using the approximate expansion of G in linear and quadratic strains at an arbitrary initial structure to find a change in the strains which moves toward a minimum of G. Iteration automatically proceeds to a minimum within preset convergence criteria on the calculation of the minimum. Comparison is made with experimental results for the ground states of seven metallic elements in hexagonal close-packed (hcp), face- and body-centered cubic structures, and with a previous procedure for finding minima based on tracing G along the epitaxial Bain path (EBP) to a minimum; the MNP is more easily generalized than the EBP procedure to lower symmetry and more atoms in the unit cell. Comparison is also made with a molecular-dynamics program for crystal equilibrium structures under pressure and with CRYSTAL, a program for crystal equilibrium structures at zero pressure. Application of MNP to the elements Y and Cd, which have hcp ground states at zero pressure, finds minima of E at face-centered cubic (fcc) structure for both Y and Cd. Evaluation of all the elastic constants shows that fcc Y is stable, hence a metastable phase, but fcc Cd is unstable.

Remotely Adjustable Hydraulic Pump

NASA Technical Reports Server (NTRS)

Kouns, H. H.; Gardner, L. D.

1987-01-01

Outlet pressure adjusted to match varying loads. Electrohydraulic servo has positioned sleeve in leftmost position, adjusting outlet pressure to maximum value. Sleeve in equilibrium position, with control land covering control port. For lowest pressure setting, sleeve shifted toward right by increased pressure on sleeve shoulder from servovalve. Pump used in aircraft and robots, where hydraulic actuators repeatedly turned on and off, changing pump load frequently and over wide range.

Rapid compression transforms interfacial monolayers of pulmonary surfactant.

PubMed

Crane, J M; Hall, S B

2001-04-01

Films of pulmonary surfactant in the lung are metastable at surface pressures well above the equilibrium spreading pressure of 45 mN/m but commonly collapse at that pressure when compressed in vitro. The studies reported here determined the effect of compression rate on the ability of monolayers containing extracted calf surfactant at 37 degrees C to maintain very high surface pressures on the continuous interface of a captive bubble. Increasing the rate from 2 A(2)/phospholipid/min (i.e., 3% of (initial area at 40 mN/m)/min) to 23%/s produced only transient increases to 48 mN/m. Above a threshold rate of 32%/s, however, surface pressures reached > 68 mN/m. After the rapid compression, static films maintained surface pressures within +/- 1 mN/m both at these maximum values and at lower pressures following expansion at < 5%/min to > or = 45 mN/m. Experiments with dimyristoyl phosphatidylcholine at 37 degrees C produced similar results. These findings indicate that compression at rates comparable to values in the lungs can transform at least some phospholipid monolayers from a form that collapses readily at the equilibrium spreading pressure to one that is metastable for prolonged periods at higher pressures. Our results also suggest that transformation of surfactant films can occur without refinement of their composition.

The Abundance of Molecular Hydrogen and Its Correlation with Midplane Pressure in Galaxies: Non-equilibrium, Turbulent, Chemical Models

NASA Astrophysics Data System (ADS)

Mac Low, Mordecai-Mark; Glover, Simon C. O.

2012-02-01

Observations of spiral galaxies show a strong linear correlation between the ratio of molecular to atomic hydrogen surface density R mol and midplane pressure. To explain this, we simulate three-dimensional, magnetized turbulence, including simplified treatments of non-equilibrium chemistry and the propagation of dissociating radiation, to follow the formation of H2 from cold atomic gas. The formation timescale for H2 is sufficiently long that equilibrium is not reached within the 20-30 Myr lifetimes of molecular clouds. The equilibrium balance between radiative dissociation and H2 formation on dust grains fails to predict the time-dependent molecular fractions we find. A simple, time-dependent model of H2 formation can reproduce the gross behavior, although turbulent density perturbations increase molecular fractions by a factor of few above it. In contradiction to equilibrium models, radiative dissociation of molecules plays little role in our model for diffuse radiation fields with strengths less than 10 times that of the solar neighborhood, because of the effective self-shielding of H2. The observed correlation of R mol with pressure corresponds to a correlation with local gas density if the effective temperature in the cold neutral medium of galactic disks is roughly constant. We indeed find such a correlation of R mol with density. If we examine the value of R mol in our local models after a free-fall time at their average density, as expected for models of molecular cloud formation by large-scale gravitational instability, our models reproduce the observed correlation over more than an order-of-magnitude range in density.

Plasma Equilibrium in a Magnetic Field with Stochastic Field-Line Trajectories

NASA Astrophysics Data System (ADS)

Krommes, J. A.; Reiman, A. H.

2008-11-01

The nature of plasma equilibrium in a magnetic field with stochastic field lines is examined, expanding upon the ideas first described by Reiman et al. The magnetic partial differential equation (PDE) that determines the equilibrium Pfirsch-Schlüter currents is treated as a passive stochastic PDE for μj/B. Renormalization leads to a stochastic Langevin equation for μ in which the resonances at the rational surfaces are broadened by the stochastic diffusion of the field lines; even weak radial diffusion can significantly affect the equilibrium, which need not be flattened in the stochastic region. Particular attention is paid to satisfying the periodicity constraints in toroidal configurations with sheared magnetic fields. A numerical scheme that couples the renormalized Langevin equation to Ampere's law is described. A. Reiman et al, Nucl. Fusion 47, 572--8 (2007). J. A. Krommes, Phys. Reports 360, 1--351.

Spreading of a pendant liquid drop underneath a textured substrate

NASA Astrophysics Data System (ADS)

Mistry, Aashutosh; Muralidhar, K.

2018-04-01

A pendant drop spreading underneath a partially wetting surface from an initial shape to its final equilibrium configuration and contact angle is studied. A mathematical formulation that quantifies spreading behavior of liquid drops over textured surfaces is discussed. The drop volume and the equilibrium contact angle are treated as parameters in the study. The unbalanced force at the three-phase contact line is modeled as being proportional to the degree of departure from the equilibrium state. Model predictions are verified against the available experimental data in the literature. Results show that the flow dynamics is strongly influenced by the fluid properties, drop volume, and contact angle of the liquid with the partially wetting surface. The drop exhibits rich dynamical behavior including inertial oscillations and gravitational instability, given that gravity tries to detach the drop against wetting contributions. Flow characteristics of drop motion, namely, the radius of the footprint, slip length, and dynamic contact angle in the pendant configuration are presented. Given the interplay among the competing time-dependent forces, a spreading drop can momentarily be destabilized and not achieve a stable equilibrium shape. Instability is then controlled by the initial drop shape as well. The spreading model is used to delineate stable and unstable regimes in the parameter space. Predictions of the drop volume based on the Young-Laplace equation are seen to be conservative relative to the estimates of the dynamical model discussed in the present study.

High rate reactive sputtering of MoN(x) coatings

NASA Technical Reports Server (NTRS)

Rudnik, Paul J.; Graham, Michael E.; Sproul, William D.

1991-01-01

High rate reactive sputtering of MoN(x) films was performed using feedback control of the nitorgen partial pressure. Coatings were made at four different target powers: 2.5, 5.0, 7.5 and 10 kW. No hysteresis was observed in the nitrogen partial pressure vs. flow plot, as is typically seen for the Ti-N system. Four phases were determined by X-ray diffraction: molybdenum, Mo-N solid solution, Beta-Mo2N and gamma-Mo2N. The hardness of the coatings depended upon composition, substrate bias, and target power. The phases present in the hardest films differed depending upon deposition parameters. For example, the Beta-Mo2N phase was hardest (load 25 gf) at 5.0 kW with a value of 3200 kgf/sq mm, whereas the hardest coatings at 10 kW were the gamma-Mo2N phase (3000 kgf/sq mm). The deposition rate generally decreased with increasing nitrogen partial pressure, but there was a range of partial pressures where the rate was relatively constant. At a target power of 5.0 kW, for example, the deposition rates were 3300 A/min for a N2 partial pressure of 0.05 - 1.0 mTorr.

Growth of the microalgae Neochloris oleoabundans at high partial oxygen pressures and sub-saturating light intensity.

PubMed

Sousa, Cláudia; de Winter, Lenneke; Janssen, Marcel; Vermuë, Marian H; Wijffels, René H

2012-01-01

The effect of partial oxygen pressure on growth of Neochloris oleoabundans was studied at sub-saturating light intensity in a fully-controlled stirred tank photobioreactor. At the three partial oxygen pressures tested (P(O)₂= 0.24; 0.63; 0.84 bar), the specific growth rate was 1.38; 1.36 and 1.06 day(-1), respectively. An increase of the P(CO)₂from 0.007 to 0.02 bar at P(O₂) of 0.84 bar resulted in an increase in the growth rate from 1.06 to 1.36 day(-1). These results confirm that the reduction of algal growth at high oxygen concentrations at sub-saturating light conditions is mainly caused by competitive inhibition of Rubisco. This negative effect on growth can be overcome by restoring the O(2)/CO(2) ratio by an increase in the partial carbon dioxide pressure. In comparison to general practice (P(O(2)) = 0.42 bar), working at partial O(2) pressure of 0.84 bar could reduce the energy requirement for degassing by a factor of 3-4. Copyright © 2011 Elsevier Ltd. All rights reserved.

Hysteresis of Contact Angle of Sessile Droplets on Smooth Homogeneous Solid Substrates via Disjoining/Conjoining Pressure.

PubMed

Kuchin, I; Starov, V

2015-05-19

A theory of contact angle hysteresis of liquid droplets on smooth, homogeneous solid substrates is developed in terms of the shape of the disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θr < θ < θa, which are different from the unique equilibrium contact angle θ ≠ θe, correspond to the state of slow "microscopic" advancing or receding motion of the liquid if θe < θ < θa or θr < θ < θe, respectively. This "microscopic" motion almost abruptly becomes fast "macroscopic" advancing or receding motion after the contact angle reaches the critical values θa or θr, correspondingly. The values of the static receding, θr, and static advancing, θa, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining/conjoining pressure isotherm. It is shown now that (i) both advancing and receding contact angles of a droplet on a on smooth, homogeneous solid substrate can be calculated based on shape of disjoining/conjoining pressure isotherm, and (ii) both advancing and receding contact angles depend on the drop volume and are not unique characteristics of the liquid-solid system. The latter is different from advancing/receding contact angles in thin capillaries. It is shown also that the receding contact angle is much closer to the equilibrium contact angle than the advancing contact angle. The latter conclusion is unexpected and is in a contradiction with the commonly accepted view that the advancing contact angle can be taken as the first approximation for the equilibrium contact angle. The dependency of hysteresis contact angles on the drop volume has a direct experimental confirmation.

Reversible Aggregation Plays a Crucial Role on the Folding Landscape of p53 Core Domain

PubMed Central

Ishimaru, Daniella; Lima, Luis M. T. R.; Maia, Lenize F.; Lopez, Priscila M.; Ano Bom, Ana P.; Valente, Ana P.; Silva, Jerson L.

2004-01-01

The role of tumor suppressor protein p53 in cell cycle control depends on its flexible and partially unstructured conformation, which makes it crucial to understand its folding landscape. Here we report an intermediate structure of the core domain of the tumor suppressor protein p53 (p53C) during equilibrium and kinetic folding/unfolding transitions induced by guanidinium chloride. This partially folded structure was undetectable when investigated by intrinsic fluorescence. Indeed, the fluorescence data showed a simple two-state transition. On the other hand, analysis of far ultraviolet circular dichroism in 1.0 M guanidinium chloride demonstrated a high content of secondary structure, and the use of an extrinsic fluorescent probe, 4,4′-dianilino-1,1′ binaphthyl-5,5′-disulfonic acid, indicated an increase in exposure of the hydrophobic core at 1 M guanidinium chloride. This partially folded conformation of p53C was plagued by aggregation, as suggested by one-dimensional NMR and demonstrated by light-scattering and gel-filtration chromatography. Dissociation by high pressure of these aggregates reveals the reversibility of the process and that the aggregates have water-excluded cavities. Kinetic measurements show that the intermediate formed in a parallel reaction between unfolded and folded structures and that it is under fine energetic control. They are not only crucial to the folding pathway of p53C but may explain as well the vulnerability of p53C to undergo departure of the native to an inactive state, which makes the cell susceptible to malignant transformation. PMID:15298872

Experimental, in-situ carbon solution mechanisms and isotope fractionation in and between (C-O-H)-saturated silicate melt and silicate-saturated (C-O-H) fluid to upper mantle temperatures and pressures

NASA Astrophysics Data System (ADS)

Mysen, Bjorn

2017-02-01

Our understanding of materials transport processes in the Earth relies on characterizing the behavior of fluid and melt in silicate-(C-O-H) systems at high temperature and pressure. Here, Raman spectroscopy was employed to determine structure of and carbon isotope partitioning between melts and fluids in alkali aluminosilicate-C-O-H systems. The experimental data were recorded in-situ while the samples were at equilibrium in a hydrothermal diamond anvil cell at temperatures and pressures to 825 °C and >1300 MPa, respectively. The carbon solution equilibrium in both (C-O-H)-saturated melt and coexisting, silicate-saturated (C-O-H) fluid is 2CO3 + H2O + 2Qn + 1 = 2HCO3 + 2Qn. In the Qn-notation, the superscript, n, is the number of bridging oxygen in silicate structural units. At least one oxygen in CO3 and HCO3 groups likely is shared with silicate tetrahedra. The structural behavior of volatile components described with this equilibrium governs carbon isotope fractionation factors between melt and fluid. For example, the ΔH equals 3.2 ± 0.7 kJ/mol for the bulk 13C/12C exchange equilibrium between fluid and melt. From these experimental data, it is suggested that at deep crustal and upper mantle temperatures and pressures, the δ13C-differences between coexisting silicate-saturated (C-O-H) fluid and (C-O-H)-saturated silicate melts may change by more than 100‰ as a function of temperature in the range of magmatic processes. Absent information on temperature and pressure, the use of carbon isotopes of mantle-derived magma to derive isotopic composition of magma source regions in the Earth's interior, therefore, should be exercised with care.

ESTIMATION OF FREE HYDROCARBON VOLUME FROM FLUID LEVELS IN MONITORING WELLS

EPA Science Inventory

Under the assumption of local vertical equilibrium, fluid pressure distributions specified from well fluid levels in monitoring wells may be used to predict water and hydrocarbon saturation profiles given expressions for air-water-hydrocarbon saturation-pressure relations. Verti...

Decline in arterial partial pressure of oxygen after exercise: a surrogate marker of pulmonary vascular obstructive disease in patients with atrial septal defect and severe pulmonary hypertension.

PubMed

Laksmivenkateshiah, Srinivas; Singhi, Anil K; Vaidyanathan, Balu; Francis, Edwin; Karimassery, Sundaram R; Kumar, Raman K

2011-06-01

To examine the utility of decline in arterial partial pressure of oxygen after exercise as a marker of pulmonary vascular obstructive disease in patients with atrial septal defect and pulmonary hypertension. Treadmill exercise was performed in 18 patients with atrial septal defect and pulmonary hypertension. Arterial blood gas samples were obtained before and after peak exercise. A decline in the arterial pressure of oxygen of more than 10 millimetres of mercury after exercise was considered significant based on preliminary tests conducted on the controls. Cardiac catheterisation was performed in all patients and haemodynamic data sets were obtained on room air, oxygen, and a mixture of oxygen and nitric oxide (30-40 parts per million). There were 10 patients who had more than a 10 millimetres of mercury drop in arterial partial pressure of oxygen after exercise and who had a basal pulmonary vascular resistance index of more than 7 Wood units per square metre. Out of eight patients who had less than a 10 millimetres of mercury drop in arterial partial pressure of oxygen after exercise, seven had a basal pulmonary vascular resistance index of less than 7 Wood units per square metre, p equals 0.0001. A decline in arterial partial pressure of oxygen of more than 10 millimetres of mercury predicted a basal pulmonary vascular resistance index of more than 7 Wood units per square metre with a specificity of 100% and a sensitivity of 90%. A decline in arterial partial pressure of oxygen following exercise appears to predict a high pulmonary vascular resistance index in patients with atrial septal defect and pulmonary hypertension. This test is a useful non-invasive marker of pulmonary vascular obstructive disease in this subset.

Achieving Chemical Equilibrium: The Role of Imposed Conditions in the Ammonia Formation Reaction

ERIC Educational Resources Information Center

Tellinghuisen, Joel

2006-01-01

Under conditions of constant temperature T and pressure P, chemical equilibrium occurs in a closed system (fixed mass) when the Gibbs free energy G of the reaction mixture is minimized. However, when chemical reactions occur under other conditions, other thermodynamic functions are minimized or maximized. For processes at constant T and volume V,…

Exploring the Clapeyron Equation and the Phase Rule Using a Mechanical Drawing Toy

ERIC Educational Resources Information Center

Darvesh, Katherine V.

2013-01-01

The equilibrium between phases is a key concept from the introductory physical chemistry curriculum. Phase diagrams display which phase is the most stable at a given temperature and pressure. If more than one phase has the lowest Gibbs energy, then those phases are in equilibrium under those conditions. An activity designed to demonstrate the…

User's manual for the FLORA equilibrium and stability code

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

Freis, R.P.; Cohen, B.I.

1985-04-01

This document provides a user's guide to the content and use of the two-dimensional axisymmetric equilibrium and stability code FLORA. FLORA addresses the low-frequency MHD stability of long-thin axisymmetric tandem mirror systems with finite pressure and finite-larmor-radius effects. FLORA solves an initial-value problem for interchange, rotational, and ballooning stability.

FLORA

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

1985-04-01

FLORA solves, in a 2D domain for the linearized stability of a long-thin (paraxial)axisymmetric equilibrium. This is of interest for determining the magnetohydrodynamic stability of a magnetic mirror plasma confinement system including finite-Larmor radius and rotation effects. An axisymmetric plasma equilibrium is specified by providing pressure profiles, the plasma mass density, the vacuum magnetic fields, and plasma electric potential as functions of (?).

Subatmospheric vapor pressures for fluoromethane (R41), 1,1-difluoroethane (R152a), and 1,1,1-trifluoroethane (R143a) evaluated from internal-energy measurements

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

Duarte-Garza, H.A.; Magee, J.W.

1999-09-01

Vapor pressures were evaluated from measured internal-energy changes {Delta}U{sup (2)} in the vapor + liquid two-phase region. The method employed a thermodynamic relationship between the derivative quantity ({partial_derivative}U{sup (2)}/{partial_derivative}V){sub T}, the vapor pressure p{sub {sigma}}, and its temperature derivative ({partial_derivative}p/{partial_derivative}T){sub {sigma}}. This method was applied at temperatures between the triple point and the normal boiling point of three substances: fluoromethane (R41), 1,1-difluoroethane (R152a), and 1,1,1-trifluoroethane (R143a). In the case of R41, vapor pressures up to 1 MPa were calculated to validate the technique at higher pressures. For R152a, the calculated vapor pressure at the triple-point temperature differed from a directmore » experimental measurement by less than the claimed uncertainty (5 Pa) of the measurement. The calculated vapor pressures for R41 helped to resolve discrepancies in several published vapor pressure sources. Agreement with experimentally measured vapor pressures for R152a and for R143a near the normal boiling point (101.325 kPa) was within the experimental uncertainty of approximately 0.04 kPa (0.04%) for the published measurements.« less

Effect of partial meniscectomy at the medial posterior horn on tibiofemoral contact mechanics and meniscal hoop strains in human knees.

PubMed

Seitz, Andreas Martin; Lubomierski, Anja; Friemert, Benedikt; Ignatius, Anita; Dürselen, Lutz

2012-06-01

We examined the influence of partial meniscectomy of 10 mm width on 10 human cadaveric knee joints, as it is performed during the treatment of radial tears in the posterior horn of the medial meniscus, on maximum contact pressure, contact area (CA), and meniscal hoop strain in the lateral and medial knee compartments. In case of 0° and 30° flexion angle, 20% and 50% partial meniscectomy did not influence maximum contact pressure and area. Only in case of 60° knee flexion, 50% partial resection increased medial maximum contact pressure and decreased the medial CA statistically significant. However, 100% partial resection increased maximum contact pressure and decreased CA significantly in the meniscectomized medial knee compartment in all tested knee positions. No significant differences were noted for meniscal hoop strain. From a biomechanical point of view, our in vitro study suggests that the medial joint compartment is not in danger of accelerated cartilage degeneration up to a resection limit of 20% meniscal depth and 10 mm width. Contact mechanics are likely to be more sensitive to partial meniscectomy at higher flexion angles, which has to be further investigated. Copyright © 2011 Orthopaedic Research Society.

Point Defect Structure of Cr203

DTIC Science & Technology

1987-10-01

Calculation of Electron Hole Mobility ........................ 104 6.2.3 Construction of the Defect Concentration vs. Oxygen Pressure Diagram...1000’ to 16000C ............ 123 7.7 Calculated diffusion coefficient vs. oxygen partial pressure diagram for pure Cr203 at 1100 0 C...127 7.10 Calculated parabolic rate constant vs. oxygen partial pressure diagram for pure Cr203 at

Computing diffusivities from particle models out of equilibrium

NASA Astrophysics Data System (ADS)

Embacher, Peter; Dirr, Nicolas; Zimmer, Johannes; Reina, Celia

2018-04-01

A new method is proposed to numerically extract the diffusivity of a (typically nonlinear) diffusion equation from underlying stochastic particle systems. The proposed strategy requires the system to be in local equilibrium and have Gaussian fluctuations but it is otherwise allowed to undergo arbitrary out-of-equilibrium evolutions. This could be potentially relevant for particle data obtained from experimental applications. The key idea underlying the method is that finite, yet large, particle systems formally obey stochastic partial differential equations of gradient flow type satisfying a fluctuation-dissipation relation. The strategy is here applied to three classic particle models, namely independent random walkers, a zero-range process and a symmetric simple exclusion process in one space dimension, to allow the comparison with analytic solutions.

Vapor Pressure of Antimony Triiodide

DTIC Science & Technology

2017-12-07

function of inverse temperature ........................................................................................... 4 Fig. 3 Effective ∆Hvapor of...pressure on inverse -temperature with the slope of (∆Hvapor/R). One method of experimentally determining ∆Hvapor, therefore, is to measure the...equilibrium vapor pressure of any material as a function of inverse -temperature where the slope of the data can be used to directly determine ∆Hvapor

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.

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.

Atomistic understanding of cation exchange in PbS nanocrystals using simulations with pseudoligands

PubMed Central

Fan, Zhaochuan; Lin, Li-Chiang; Buijs, Wim; Vlugt, Thijs J. H.; van Huis, Marijn A.

2016-01-01

Cation exchange is a powerful tool for the synthesis of nanostructures such as core–shell nanocrystals, however, the underlying mechanism is poorly understood. Interactions of cations with ligands and solvent molecules are systematically ignored in simulations. Here, we introduce the concept of pseudoligands to incorporate cation-ligand-solvent interactions in molecular dynamics. This leads to excellent agreement with experimental data on cation exchange of PbS nanocrystals, whereby Pb ions are partially replaced by Cd ions from solution. The temperature and the ligand-type control the exchange rate and equilibrium composition of cations in the nanocrystal. Our simulations reveal that Pb ions are kicked out by exchanged Cd interstitials and migrate through interstitial sites, aided by local relaxations at core–shell interfaces and point defects. We also predict that high-pressure conditions facilitate strongly enhanced cation exchange reactions at elevated temperatures. Our approach is easily extendable to other semiconductor compounds and to other families of nanocrystals. PMID:27160371

Oxygen self-diffusion mechanisms in monoclinic Zr O2 revealed and quantified by density functional theory, random walk analysis, and kinetic Monte Carlo calculations

NASA Astrophysics Data System (ADS)

Yang, Jing; Youssef, Mostafa; Yildiz, Bilge

2018-01-01

In this work, we quantify oxygen self-diffusion in monoclinic-phase zirconium oxide as a function of temperature and oxygen partial pressure. A migration barrier of each type of oxygen defect was obtained by first-principles calculations. Random walk theory was used to quantify the diffusivities of oxygen interstitials by using the calculated migration barriers. Kinetic Monte Carlo simulations were used to calculate diffusivities of oxygen vacancies by distinguishing the threefold- and fourfold-coordinated lattice oxygen. By combining the equilibrium defect concentrations obtained in our previous work together with the herein calculated diffusivity of each defect species, we present the resulting oxygen self-diffusion coefficients and the corresponding atomistically resolved transport mechanisms. The predicted effective migration barriers and diffusion prefactors are in reasonable agreement with the experimentally reported values. This work provides insights into oxygen diffusion engineering in Zr O2 -related devices and parametrization for continuum transport modeling.

Thermodynamic Analysis for the Refining Ability of Salt Flux for Aluminum Recycling

PubMed Central

Hiraki, Takehito; Miki, Takahiro; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2014-01-01

The removability of impurities during the aluminum remelting process by oxidation was previously investigated by our research group. In the present work, alternative impurity removal with chlorination has been evaluated by thermodynamic analysis. For 43 different elements, equilibrium distribution ratios among metal, chloride flux and oxide slag phases in the aluminum remelting process were calculated by assuming the binary systems of aluminum and an impurity element. It was found that the removability of impurities isn’t significantly affected by process parameters such as chloride partial pressure, temperature and flux composition. It was shown that Ho, Dy, Li, La, Mg, Gd, Ce, Yb, Ca and Sr can be potentially eliminated into flux by chlorination from the remelted aluminum. Chlorination and oxidation are not effective to remove other impurities from the melting aluminum, due to the limited parameters which can be controlled during the remelting process. It follows that a proper management of aluminum scrap such as sorting based on the composition of the products is important for sustainable aluminum recycling. PMID:28788144

Growth Responses of Neurospora crassa to Increased Partial Pressures of the Noble Gases and Nitrogen

PubMed Central

Buchheit, R. G.; Schreiner, H. R.; Doebbler, G. F.

1966-01-01

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622–627. 1966.—Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically “inert gas” present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar ≫ Ne ≫ He. Nitrogen (N2) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He (∼ 300 atm). With respect to inhibition of growth, the noble gases and N2 differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O2-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases. PMID:5883104

Report on ISS Oxygen Production, Resupply, and Partial Pressure Management

NASA Technical Reports Server (NTRS)

Schaezler, Ryan; Ghariani, Ahmed; Leonard, Daniel; Lehman, Daniel

2011-01-01

The majority of oxygen used on International Space Station (ISS) is for metabolic support and denitrogenation procedures prior to Extra-Vehicular Activities. Oxygen is supplied by various visiting vehicles such as the Progress and Shuttle in addition to oxygen production capability on both the United States On-Orbit Segment (USOS) and Russian Segment (RS). To maintain a habitable atmosphere the oxygen partial pressure is controlled between upper and lower bounds. The full range of the allowable oxygen partial pressure along with the increased ISS cabin volume is utilized as a buffer allowing days to pass between oxygen production or direct addition of oxygen to the atmosphere from reserves. This paper summarizes amount of oxygen supplied and produced from all of the sources and describes past experience of managing oxygen partial pressure along with the range of management options available to the ISS.

Thin film oxygen partial pressure sensor

NASA Technical Reports Server (NTRS)

Wortman, J. J.; Harrison, J. W.; Honbarrier, H. L.; Yen, J.

1972-01-01

The development is described of a laboratory model oxygen partial pressure sensor using a sputtered zinc oxide thin film. The film is operated at about 400 C through the use of a miniature silicon bar. Because of the unique resistance versus temperature relation of the silicon bar, control of the operational temperature is achieved by controlling the resistance. A circuit for accomplishing this is described. The response of sputtered zinc oxide films of various thicknesses to oxygen, nitrogen, argon, carbon dioxide, and water vapor caused a change in the film resistance. Over a large range, film conductance varied approximately as the square root of the oxygen partial pressure. The presence of water vapor in the gas stream caused a shift in the film conductance at a given oxygen partial pressure. A theoretical model is presented to explain the characteristic features of the zinc oxide response to oxygen.

Partial pressures of oxygen, phosphorus and fluorine in some lunar lavas

NASA Technical Reports Server (NTRS)

Nash, W. P.; Hausel, W. D.

1973-01-01

Lunar sample 14310 is a feldspar-rich basalt which shows no evidence of shock deformation or recrystallization. Pyroxenes include Mg-rich orthopyroxene, pigeonite and augite; pyroxferroite occurs in the interstitial residuum. Plagioclase feldspars are zoned from An(96) to An(67), and variations in feldspar compositions do not necessarily indicate loss of Na during eruption of the lava. Opaque phases include ilmenite, ulvospinel, metallic iron, troilite, and schreibersite. Both whitlockite and apatite are present, and the interstitial residua contain baddeleyite, tranquillityite and barium-rich sanidine. Theoretical calculations provide estimates of partial pressures of oxygen, phosphorus, and fluorine in lunar magmas. In general, partial pressures of oxygen are restricted by the limiting assemblages of iron-wuestite and ilmenite-iron-rutile; phosphorus partial pressures are higher in lunar magmas than in terrestrial lavas. The occurrence of whitlockite indicates significantly lower fugacities of fluorine in lunar magmas than in terrestrial magmas.

Experimental testing of olivine-melt equilibrium models at high temperatures

NASA Astrophysics Data System (ADS)

Krasheninnikov, S. P.; Sobolev, A. V.; Batanova, V. G.; Kargaltsev, A. A.; Borisov, A. A.

2017-08-01

Data are presented on the equilibrium compositions of olivine and melts in the products of 101 experiments performed at 1300-1600°C, atmospheric pressure, and controlled oxygen fugacity by means of new equipment at the Vernadsky Institute. It was shown that the available models of the olivine-melt equilibrium describe with insufficient adequacy the natural systems at temperatures over 1400°C. The most adequate is the model by Ford et al. (1983). However, this model overestimates systematically the equilibrium temperature with underestimating by 20-40°C at 1450-1600°C. These data point to the need for developing a new, improved quantitative model of the olivine-melt equilibrium for high-temperature magnesian melts, as well as to the possibility of these studies on the basis of the equipment presented.

Physical analysis of the process of cavitation in xylem sap.

PubMed

Shen, Fanyi; Gao, Rongfu; Liu, Wenji; Zhang, Wenjie

2002-06-01

Recent studies have confirmed that cavitation in xylem is caused by air bubbles. We analyzed expansion of a preexistent bubble adhering to a crack in a conduit wall and a bubble formed by the passage of air through a pore of a pit membrane, a process known as air seeding. We consider that there are two equilibrium states for a very small air bubble in the xylem: one is temporarily stable with a bubble radius r1 at point s1 on the curve P(r) relating pressure within the bubble (P) with bubble radius (r); the other is unstable with a bubble radius r2 at point s2 on Pr (where r1 < r2). In each equilibrium state, the bubble collapse pressure (2sigma/r, where sigma is surface tension of water) is balanced by the pressure difference across its surface. In the case of a bubble from a crack in a conduit wall, which is initially at point s1, expansion will occur steadily as water potential decreases. The bubble will burst only if the xylem pressure drops below a threshold value. A formula giving the threshold pressure for bubble bursting is proposed. In the case of an air seed entering a xylem conduit through a pore in a pit membrane, its initial radius may be r2 (i.e., the radius of the pore by which the air seed entered the vessel) at point s2 on Pr. Because the bubble is in an unstable equilibrium when entering the conduit, it can either expand or contract to point s1. As water vaporizes into the air bubble at s2, P rises until it exceeds the gas pressure that keeps the bubble in equilibrium, at which point the bubble will burst and induce a cavitation event in accordance with the air-seeding hypothesis. However, other possible perturbations could make the air-seeded bubble contract to s1, in which case the bubble will burst at a threshold pressure proposed for a bubble expanding from a crack in a conduit wall. For this reason some cavitation events may take place at a xylem threshold pressure (Pl'*) other than that determined by the formula, Plp'* = -2sigma/rp, proposed by Sperry and Tyree (1988), which is applicable only to air-seeded bubbles at s2. The more general formula we propose for calculating the threshold pressure for bubble breaking is consistent with the results of published experiments.

Agent-Centric Approach for Cybersecurity Decision-Support with Partial Observability

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

Tipireddy, Ramakrishna; Chatterjee, Samrat; Paulson, Patrick R.

Generating automated cyber resilience policies for real-world settings is a challenging research problem that must account for uncertainties in system state over time and dynamics between attackers and defenders. In addition to understanding attacker and defender motives and tools, and identifying “relevant” system and attack data, it is also critical to develop rigorous mathematical formulations representing the defender’s decision-support problem under uncertainty. Game-theoretic approaches involving cyber resource allocation optimization with Markov decision processes (MDP) have been previously proposed in the literature. Moreover, advancements in reinforcement learning approaches have motivated the development of partially observable stochastic games (POSGs) in various multi-agentmore » problem domains with partial information. Recent advances in cyber-system state space modeling have also generated interest in potential applicability of POSGs for cybersecurity. However, as is the case in strategic card games such as poker, research challenges using game-theoretic approaches for practical cyber defense applications include: 1) solving for equilibrium and designing efficient algorithms for large-scale, general problems; 2) establishing mathematical guarantees that equilibrium exists; 3) handling possible existence of multiple equilibria; and 4) exploitation of opponent weaknesses. Inspired by advances in solving strategic card games while acknowledging practical challenges associated with the use of game-theoretic approaches in cyber settings, this paper proposes an agent-centric approach for cybersecurity decision-support with partial system state observability.« less

Table and charts of equilibrium normal shock and shock tube properties for pure argon with velocities to 18 km/sec

NASA Technical Reports Server (NTRS)

Miller, C. G., III; Wilder, S. E.

1976-01-01

Equilibrium thermodynamic and flow properties are presented in tabulated and graphical form for moving, standing, and reflected normal shock waves in pure argon. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, isentropic exponent, velocity, and species mole fractions. Incident (moving) shock velocities are varied from 2 to 18 km/sec for a range of initial pressure of 5 N/sq m to 500 kN/sq m. Working charts illustrating shock tube performance with argon test gas and heated helium and hydrogen driver gases are also presented.

Analytical and computational studies on the vacuum performance of a chevron ejector

NASA Astrophysics Data System (ADS)

Kong, F. S.; Jin, Y. Z.; Kim, H. D.

2016-11-01

The effects of chevrons on the performance of a supersonic vacuum ejector-diffuser system are investigated numerically and evaluated theoretically in this work. A three-dimensional geometrical domain is numerically solved using a fully implicit finite volume scheme based on the unsteady Reynolds stress model. A one-dimensional mathematical model provides a useful tool to reveal the steady flow physics inside the vacuum ejector-diffuser system. The effects of the chevron nozzle on the generation of recirculation regions and Reynolds stress behaviors are studied and compared with those of a conventional convergent nozzle. The present performance parameters obtained from the simulated results and the mathematical results are validated with existing experimental data and show good agreement. Primary results show that the duration of the transient period and the secondary chamber pressure at a dynamic equilibrium state depend strongly on the primary jet conditions, such as inlet pressure and primary nozzle shape. Complicated oscillatory flow, generated by the unsteady movement of recirculation, finally settles into a dynamic equilibrium state. As a vortex generator, the chevron demonstrated its strong entrainment capacity to accelerate the starting transient flows to a certain extent and reduce the dynamic equilibrium pressure of the secondary chamber significantly.

Influence of oxygen partial pressure on the composition and orientation of strontium-doped lead zirconate titanate thin films.

PubMed

Sriram, S; Bhaskaran, M; du Plessis, J; Short, K T; Sivan, V P; Holland, A S

2009-01-01

The influence of oxygen partial pressure during the deposition of piezoelectric strontium-doped lead zirconate titanate thin films is reported. The thin films have been deposited by RF magnetron sputtering in an atmosphere of high purity argon and oxygen (in the ratio of 9:1), on platinum-coated silicon substrates (heated to 650 degrees C). The influence of oxygen partial pressure is studied to understand the manner in which the stoichiometry of the thin films is modified, and to understand the influence of stoichiometry on the perovskite orientation. This article reports on the results obtained from films deposited at oxygen partial pressures of 1-5 mTorr. The thin films have been studied using a combination of X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GA-XRD), and atomic force microscopy (AFM). XPS analysis highlights the marked influence of variations in oxygen pressure during sputtering, observed by variations in oxygen concentration in the thin films, and in some cases by the undesirable decrease in lead concentration in the thin films. GA-XRD is used to study the relative variations in perovskite peak intensities, and has been used to determine the deposition conditions to attain the optimal combination of stoichiometry and orientation. AFM scans show the marked influence of the oxygen partial pressure on the film morphology.

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

Titan's Interior Chemical Composition: A Thermochemical Assessment*

NASA Astrophysics Data System (ADS)

Howard, Michael; Zaug, J. M.; Khare, B. N.; McKay, C. P.

2007-10-01

We study the interior composition of Titan using thermal chemical equilibrium calculations that are valid to high pressures and temperatures. The equations of state are based on exponential-6 fluid theory and have been validated against experimental data up to a few Mbars in pressure and approximately 20000K in temperature. In addition to CHNO molecules, we account for multi-phases of carbon, water and a variety of metals such as Al and Fe, and their oxides. With these fluid equations of state, chemical equilibrium is calculated for a set of product species. As the temperature and pressure evolves for increasing depth in the interior, the chemical equilibrium shifts. We assume that Titan is initially composed of comet material, which we assume to be solar, except for hydrogen, which we take to be depleted by a factor 1/690. We find that a significant amount of nitrogen is in the form of n2, rather than nh3. Moreover, above 12 kbars, as is the interior pressure of Titan, a significant amount of the carbon is in the form of graphite, rather than co2 and ch4. We discuss the implications of these results for understanding the atmospheric and surface composition of Titan. • This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Nonlocal collisionless and collisional electron transport in low temperature plasmas

NASA Astrophysics Data System (ADS)

Kaganovich, Igor

2009-10-01

The purpose of the talk is to describe recent advances in nonlocal electron kinetics in low-pressure plasmas. A distinctive property of partially ionized plasmas is that such plasmas are always in a non-equilibrium state: the electrons are not in thermal equilibrium with the neutral species and ions, and the electrons are also not in thermodynamic equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Typical phenomena in such discharges include nonlocal electron kinetics, nonlocal electrodynamics with collisionless electron heating, and nonlinear processes in the sheaths and in the bounded plasmas. Significant progress in understanding the interaction of electromagnetic fields with real bounded plasma created by this field and the resulting changes in the structure of the applied electromagnetic field has been one of the major achievements of the last decade in this area of research [1-3]. We show on specific examples that this progress was made possible by synergy between full scale particle-in-cell simulations, analytical models, and experiments. In collaboration with Y. Raitses, A.V. Khrabrov, Princeton Plasma Physics Laboratory, Princeton, NJ, USA; V.I. Demidov, UES, Inc., 4401 Dayton-Xenia Rd., Beavercreek, OH 45322, USA and AFRL, Wright-Patterson AFB, OH 45433, USA; and D. Sydorenko, University of Alberta, Edmonton, Canada. [4pt] [1] D. Sydorenko, A. Smolyakov, I. Kaganovich, and Y. Raitses, IEEE Trans. Plasma Science 34, 895 (2006); Phys. Plasmas 13, 014501 (2006); 14 013508 (2007); 15, 053506 (2008). [0pt] [2] I. D. Kaganovich, Y. Raitses, D. Sydorenko, and A. Smolyakov, Phys. Plasmas 14, 057104 (2007). [0pt] [3] V.I. Demidov, C.A. DeJoseph, and A.A. Kudryavtsev, Phys. Rev. Lett. 95, 215002 (2005); V.I. Demidov, C.A. DeJoseph, J. Blessington, and M.E. Koepke, Europhysics News, 38, 21 (2007).

Measuring Ancient Air Pressure Using Fossilized Cyanobacteria

NASA Astrophysics Data System (ADS)

Silverman, S. N.; Som, S. M.; Gordon, R.; Bebout, B.

2016-12-01

The evolution of Earth's atmosphere has been governed by biological evolution. The dominant air component, nitrogen, has undergone substantial variation over geological time. Today, the partial pressure of nitrogen is 0.79 bar, but this value could have been much higher during early Earth1. The nitrogen partial pressure is postulated to have dropped to a maximum of 0.5 bar before the Great Oxidation Event 2.4 billion years ago, and subsequently recovered to the 0.8 bar value of our modern atmosphere over the next 330 million years2. We are placing constraints on the trajectory of this recovery by investigating how nitrogen partial pressure influences the morphology of a certain species of filamentous cyanobacteria that has been found fossilized in 2 billion year old rocks. These filamentous cyanobacteria convert nitrogen from its dissolved gaseous state (N2) to a biologically useful state (i.e. NH3) when the latter is present at growth-limiting concentrations in their aquatic environment. Such cyanobacteria develop heterocysts (specialized, visually distinct cells), which fix the nitrogen and laterally distribute it to neighboring cells along the one-dimensional filament. We suggest that the distance between heterocysts reflects the nitrogen partial pressure dissolved in water, which is related to atmospheric pN2 by Henry's law. In the laboratory, we are quantifying the relationship between heterocyst distance, variance and covariance to atmospheric pN2 by subjecting cyanobacteria (in media devoid of nitrate) to different partial pressures of N2 at a constant temperature and lighting for the representative species Anabaena variabilis. As far as we know, such experiments have not been previously conducted. This new geobarometer will complement existing methods of quantifying ancient nitrogen partial pressure. 1Goldblatt, Colin, et al. "Nitrogen-enhanced greenhouse warming on early Earth." Nature Geoscience 2 (2009): 891-896. 2Som, S., et al. "Earth's air pressure 2.7 billion years ago constrained to less than half of modern levels." Nature Geoscience 9 (2016): 448-451.

Investigation of fast ion pressure effects in ASDEX Upgrade by spectral MSE measurements

NASA Astrophysics Data System (ADS)

Reimer, René; Dinklage, Andreas; Wolf, Robert; Dunne, Mike; Geiger, Benedikt; Hobirk, Jörg; Reich, Matthias; ASDEX Upgrade Team; McCarthy, Patrick J.

2017-04-01

High precision measurements of fast ion effects on the magnetic equilibrium in the ASDEX Upgrade tokamak have been conducted in a high-power (10 MW) neutral-beam injection discharge. An improved analysis of the spectral motional Stark effect data based on forward-modeling, including the Zeeman effect, fine-structure and non-statistical sub-level distribution, revealed changes in the order of 1% in |B| . The results were found to be consistent with results from the equilibrium solver CLISTE. The measurements allowed us to derive the fast ion pressure fraction to be Δ {{p}\\text{FI}}/{{p}\\text{mhd}}≈ 10 % and variations of the fast ion pressure are consistent with calculations of the transport code TRANSP. The results advance the understanding of fast ion confinement and magneto-hydrodynamic stability in the presence of fast ions.

Methods and apparatus for reducing corrosion in refractory linings

DOEpatents

Poeppel, Roger B.; Greenberg, Sherman; Diercks, Dwight R.

1987-01-01

Methods and apparatus are provided for reducing corrosion in a refractory lining of a liquid-containing vessel used in direct steelmaking processes. The vessel operates at between about 1600.degree. C. and about 1800.degree. C. and an oxygen partial pressure of about 10.sup.-12 atmospheres, creating slag which is rich in FeO. The refractory lining includes a significant level of chromium oxide (Cr.sub.2 O.sub.3), and has small interconnected pores which may be filled with a gas mixture having a higher total pressure and oxygen partial pressure than the total pressure and oxygen partial pressure associted with the liquid against the lining of the vessel. The gas mixture is forced through the pores of the lining so that the pores are continuously filled with the mixture. In this manner, the gas mixture creates a blanket which increases the oxygen partial pressure at the lining enough to maintain the chromium in the lining in a selected valence state in which the chromium has decreased solubility in the FeO slag, thereby reducing corrosion by the FeO and increasing the useful life of the refractory lining.

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.

Incidence and Determinants of Port Occlusions in Cancer Outpatients: A Prospective Cohort Study.

PubMed

Milani, Alessandra; Mazzocco, Ketti; Gandini, Sara; Pravettoni, Gabriella; Libutti, Livio; Zencovich, Claudia; Sbriglia, Ada; Pari, Chiara; Magon, Giorgio; Saiani, Luisa

Normal saline is considered a safe alternative for heparin as a locking solution in totally implantable venous access devices. The incidence rate of partial occlusion with the use of normal saline (easy injection, impossible aspiration) is estimated at 4%. The aim of this study was to investigate determinants of partial occlusions with the use of normal saline solution and the maintenance of positive pressure in the catheter. We enrolled 218 patients with different solid tumors who underwent pharmacologic treatment through the port with different frequencies: from once every week to at least once every month. The port was flushed with normal saline solution keeping a positive pressure in the catheter. We performed 4111 observations and documented normal port functioning in 99% of observations (n = 4057) and partial occlusions in 1% of observations (n = 54). Partial occlusions were significantly associated with frequency of port flushing (P < .05), chemotherapy (P < .001), and blood sample collection (P < .001). The use of positive pressure in addition to normal saline reduces the incidence rate of partial occlusions. The type of treatment, blood sample collection, and treatment schedule are important determinants of partial occlusions. Nurses play a key role in maintaining a functioning port using positive pressure during the flushing techniques. Certain risk factors must be monitored to prevent partial occlusions, and certain patients are more likely to present with port-related problems.

Thermodynamic properties of methane hydrate in quartz powder.

PubMed

Voronov, Vitaly P; Gorodetskii, Evgeny E; Safonov, Sergey S

2007-10-04

Using the experimental method of precision adiabatic calorimetry, the thermodynamic (equilibrium) properties of methane hydrate in quartz sand with a grain size of 90-100 microm have been studied in the temperature range of 260-290 K and at pressures up to 10 MPa. The equilibrium curves for the water-methane hydrate-gas and ice-methane hydrate-gas transitions, hydration number, latent heat of hydrate decomposition along the equilibrium three-phase curves, and the specific heat capacity of the hydrate have been obtained. It has been experimentally shown that the equilibrium three-phase curves of the methane hydrate in porous media are shifted to the lower temperature and high pressure with respect to the equilibrium curves of the bulk hydrate. In these experiments, we have found that the specific heat capacity of the hydrate, within the accuracy of our measurements, coincides with the heat capacity of ice. The latent heat of the hydrate dissociation for the ice-hydrate-gas transition is equal to 143 +/- 10 J/g, whereas, for the transition from hydrate to water and gas, the latent heat is 415 +/- 15 J/g. The hydration number has been evaluated in the different hydrate conditions and has been found to be equal to n = 6.16 +/- 0.06. In addition, the influence of the water saturation of the porous media and its distribution over the porous space on the measured parameters has been experimentally studied.

Effects of Shock-Breakout Pressure on Ejection of Micron-Scale Material from Shocked Tin Surfaces

NASA Astrophysics Data System (ADS)

Zellner, Michael; Hammerberg, James; Hixson, Robert; Morley, Kevin; Obst, Andrew; Olson, Russell; Payton, Jeremy; Rigg, Paulo; Buttler, William; Grover, Michael; Iverson, Adam; Macrum, Gregory; Stevens, Gerald; Turley, William; Veeser, Lynn; Routley, Nathan

2007-06-01

Los Alamos National Lab (LANL) is actively engaged in the development of a model to predict the formation of micron-scale fragments ejected (ejecta) from shocked metal surfaces. The LANL ejecta model considers that the amount of ejecta is mainly related to the material's phase on shock release at the free-surface. This effort investigates the relation between ejecta production and shock-breakout pressure for Sn shocked with high explosives to pressures near the solid-on-release/partial-liquid-on-release phase transition region. We found that the amount of ejecta produced for shock-breakout pressures that resulted in partial-liquid-on-release increased significantly compared to that which resulted in solid-on-release. Additionally, we found that the amount of ejecta remained relatively constant within the partial-liquid-on-release, regardless of shock-breakout pressure.

Pressure Effects on the Ejection of Material from Shocked Tin Surfaces

NASA Astrophysics Data System (ADS)

Zellner, M. B.; Grover, M.; Hammerberg, J. E.; Hixson, R. S.; Iverson, A. J.; Macrum, G. S.; Morley, K. B.; Obst, A. W.; Olson, R. T.; Payton, J. R.; Rigg, P. A.; Routley, N.; Stevens, G. D.; Turley, W. D.; Veeser, L.; Buttler, W. T.

2007-12-01

Los Alamos National Lab (LANL) is actively engaged in the development of a model to predict the formation of micron-scale fragments ejected (ejecta) from shocked metals that have surface defects. The LANL ejecta model considers that the amount of ejecta is mainly related to the material's phase on shock release at the free-surface. This effort investigates the relation between ejecta production and shock-breakout pressure for Sn shocked with high explosives to pressures near the solid-on-release/partial-liquid-on-release phase transition region. We found that the amount of ejecta produced for shock-breakout pressures that resulted in partial-liquid-on-release increased significantly compared to that which resulted in solid-on-release. Additionally, we found that the amount of ejecta remained relatively constant within the partial-liquid-on-release, regardless of shock-breakout pressure.

Equivalent air depth: fact or fiction.

PubMed

Berghage, T E; McCraken, T M

1979-12-01

In mixed-gas diving theory, the equivalent air depth (EAD) concept suggests that oxygen does not contribute to the total tissue gas tension and can therefore be disregarded in calculations of the decompression process. The validity of this assumption has been experimentally tested by exposing 365 rats to various partial pressures of oxygen for various lengths of time. If the EAD assumption is correct, under a constant exposure pressure each incremental change in the oxygen partial pressure would produce a corresponding incremental change in pressure reduction tolerance. Results of this study suggest that the EAD concept does not adequately describe the decompression advantages obtained from breathing elevated oxygen partial pressures. The authors suggest that the effects of breathing oxygen vary in a nonlinear fashion across the range from anoxia to oxygen toxicity, and that a simple inert gas replacement concept is no longer tenable.

A Simple System for Observing Dynamic Phase Equilibrium via an Inquiry-Based Laboratory or Demonstration

ERIC Educational Resources Information Center

Cloonan, Carrie A.; Andrew, Julie A.; Nichol, Carolyn A.; Hutchinson, John S.

2011-01-01

This article describes an activity that can be used as an inquiry-based laboratory or demonstration for either high school or undergraduate chemistry students to provide a basis for understanding both vapor pressure and the concept of dynamic phase equilibrium. The activity includes a simple setup to create a closed system of only water liquid and…

Composition and Thermodynamic Properties of Air in Chemical Equilibrium

NASA Technical Reports Server (NTRS)

Moeckel, W E; Weston, Kenneth C

1958-01-01

Charts have been prepared relating the thermodynamic properties of air in chemical equilibrium for temperatures to 15,000 degrees k and for pressures 10(-5) to 10 (plus 4) atmospheres. Also included are charts showing the composition of air, the isentropic exponent, and the speed of sound. These charts are based on thermodynamic data calculated by the National Bureau of Standards.

Fuel cell serves as oxygen level detector

NASA Technical Reports Server (NTRS)

1965-01-01

Monitoring the oxygen level in the air is accomplished by a fuel cell detector whose voltage output is proportional to the partial pressure of oxygen in the sampled gas. The relationship between output voltage and partial pressure of oxygen can be calibrated.

Remapping HELENA to incompressible plasma rotation parallel to the magnetic field

NASA Astrophysics Data System (ADS)

Poulipoulis, G.; Throumoulopoulos, G. N.; Konz, C.

2016-07-01

Plasma rotation in connection to both zonal and mean (equilibrium) flows can play a role in the transitions to the advanced confinement regimes in tokamaks, as the L-H transition and the formation of internal transport barriers (ITBs). For incompressible rotation, the equilibrium is governed by a generalised Grad-Shafranov (GGS) equation and a decoupled Bernoulli-type equation for the pressure. For parallel flow, the GGS equation can be transformed to one identical in form with the usual Grad-Shafranov equation. In the present study on the basis of the latter equation, we have extended HELENA, an equilibrium fixed boundary solver. The extended code solves the GGS equation for a variety of the two free-surface-function terms involved for arbitrary Alfvén Mach number and density functions. We have constructed diverted-boundary equilibria pertinent to ITER and examined their characteristics, in particular, as concerns the impact of rotation on certain equilibrium quantities. It turns out that the rotation and its shear affect noticeably the pressure and toroidal current density with the impact on the current density being stronger in the parallel direction than in the toroidal one.

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

Hassan, N.M.; Ghosh, T.K.; Hines, A.L.

Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of themore » isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer`s classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation.« less

Method of enhancing selective isotope desorption from metals

DOEpatents

Knize, Randall J.; Cecchi, Joseph L.

1984-01-01

A method of enhancing the thermal desorption of a first isotope of a diatomic gas from a metal comprises the steps of (a) establishing a partial pressure of a second isotope of the diatomic gas in vicinity of the metal; heating the metal to a temperature such that the first isotope is desorbed from the metal; and reducing the partial pressure of the desorbed first isotope while maintaining the partial pressure of the second isotope substantially constant. The method is especially useful for enhancing the desorption of tritium from the Zr-Al getter in a plasma confinement device.

Study on the intrinsic defects in ZnO by combing first-principle and thermodynamic calculations

NASA Astrophysics Data System (ADS)

Ma, Changmin; Liu, Tingyu; Chang, Qiuxiang

2015-11-01

In this paper, the intrinsic point defects in ZnO crystal have been studied by the approach that integrates first-principles, thermodynamic calculations and the contributions of vibrational entropy. With temperature increasing and oxygen partial pressure decreasing, the formation energies of oxygen vacancy (VO), zinc interstitial (Zni) and zinc anti-site (ZnO) are decreasing, while it increases for zinc vacancy (VZn), oxygen interstitial (Oi) and oxygen anti-site (OZn). They are more sensitive to temperature than oxygen partial pressure. There are two interesting phenomena. First, VO or VZn have the lowest formation energies for whole Fermi level at special environment condition (such as at T = 300K, about PO2 = 10-10atm or T = 1500K, about PO2 = 104atm) and intrinsic p-type doping of ZnO is possible by VZn at these special conditions. Second, VO as donors have lowest formation energy for all Fermi level at high temperature and low oxygen partial pressure (T = 1500K, PO2 = 10-10atm). According to our analysis, the VO could produce n-type doping in ZnO at these special conditions and change p-type ZnO to n-type ZnO at condition from low temperature and high oxygen partial pressure to high temperature and low oxygen partial pressure.

Oxygen Partial Pressure Is a Rate-Limiting Parameter for Cell Proliferation in 3D Spheroids Grown in Physioxic Culture Condition.

PubMed

Gomes, Aurélie; Guillaume, Ludivine; Grimes, David Robert; Fehrenbach, Jérôme; Lobjois, Valérie; Ducommun, Bernard

2016-01-01

The in situ oxygen partial pressure in normal and tumor tissues is in the range of a few percent. Therefore, when studying cell growth in 3D culture systems, it is essential to consider how the physiological oxygen concentration, rather than the one in the ambient air, influences the proliferation parameters. Here, we investigated the effect of reducing oxygen partial pressure from 21% to 5% on cell proliferation rate and regionalization in a 3D tumor spheroid model. We found that 5% oxygen concentration strongly inhibited spheroid growth, changed the proliferation gradient and reduced the 50% In Depth Proliferation index (IDP50), compared with culture at 21% oxygen. We then modeled the oxygen partial pressure profiles using the experimental data generated by culturing spheroids in physioxic and normoxic conditions. Although hypoxia occurred at similar depth in spheroids grown in the two conditions, oxygen partial pressure was a major rate-limiting factor with a critical effect on cell proliferation rate and regionalization only in spheroids grown in physioxic condition and not in spheroids grown at atmospheric normoxia. Our findings strengthen the need to consider conducting experiment in physioxic conditions (i.e., tissue normoxia) for proper understanding of cancer cell biology and the evaluation of anticancer drugs in 3D culture systems.

Wiedemann-Franz ratio in high-pressure and low-temperature thermal xenon plasma with 10% caesium

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

Novakovic, N.V.; Milic, B.S.; Stojilkovic, S.M.

1995-12-31

Theoretical investigations of various transport properties of low-temperature noble-gas plasmas with additives has aroused a continuous interest over a considerable spall of time, due to numerous applications. In this paper the results of a theoretical evaluation of electrical conductivity, thermal conductivity and their ratio (the Wiedemann-Franz ratio) in xenon plasma with 10% of argon and 10% of caesium are presented, for the temperature range from 2000 K to 20000 K, and for pressures equal to or 5, 10, and 15 time higher than the normal atmospheric pressure. The plasma was regarded as weakly non-ideal and in the state of localmore » thermodynamical equilibrium with the assumption that the equilibrium is attained with the pressure kept constant. The plasma composition was determined on the ground of a set of Saha equations; the ionization energy lowerings were expressed with the aid of a modified plasma Debye radius r*{sub D} (rather than the standard r{sub D}), as proposed previously.« less

The Gaseous Explosive Reaction : The Effect of Inert Gases

NASA Technical Reports Server (NTRS)

Stevens, F W

1928-01-01

Attention is called in this report to previous investigations of gaseous explosive reactions carried out under constant volume conditions, where the effect of inert gases on the thermodynamic equilibrium was determined. The advantage of constant pressure methods over those of constant volume as applied to studies of the gaseous explosive reaction is pointed out and the possibility of realizing for this purpose a constant pressure bomb mentioned. The application of constant pressure methods to the study of gaseous explosive reactions, made possible by the use of a constant pressure bomb, led to the discovery of an important kinetic relation connecting the rate of propagation of the zone of explosive reaction within the active gases, with the initial concentrations of those gases: s = K(sub 1)(A)(sup n1)(B)(sup n2)(C)(sup n3)------. By a method analogous to that followed in determining the effect of inert gases on the equilibrium constant K, the present paper records an attempt to determine their kinetic effect upon the expression given above.

Two-phase choked flow of cryogenic fluids in converging-diverging nozzles

NASA Technical Reports Server (NTRS)

Simoneau, R. J.; Hendricks, R. C.

1979-01-01

Data are presented for the two phase choked flow of three cryogenic fluids - nitrogen, methane, and hydrogen - in four converging-diverging nozzles. The data cover a range of inlet stagnation conditions, all single phase, from well below to well above the thermodynamic critical conditions. In almost all cases the nozzle throat conditions were two phase. The results indicate that the choked flow rates were not very sensitive to nozzle geometry. However, the axial pressure profiles, especially the throat pressure and the point of vaporization, were very sensitive to both nozzle geometry and operating conditions. A modified Henry-Fauske model correlated all the choked flow rate data to within + or - 10 percent. Neither the equilibrium model nor the Henry-Fauske model predicted throat pressures well over the whole range of data. Above the thermodynamic critical temperature the homogeneous equilibrium model was preferred for both flow rate and pressure ratio. The data of the three fluids could be normalized by the principle of corresponding states.

Electron transfer between cytochrome. alpha. and copper A in cytochrome c oxidase: A perturbed equilibrium study

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

Morgan, J.E.; Li, P.M.; Jang, D.J.

1989-08-22

Intramolecular electron transfer in partially reduced cytochrome c oxidase has been studied by the perturbed equilibrium method. The authors have prepared a three-electron-reduced, CO-inhibited form of the enzyme in which cytochrome a and copper A are partially reduced and in an intramolecular redox equilibrium. When these samples were irradiated with a nitrogen laser to photodissociate the bound CO, changes in absorbance at 598 and 830 nm were observed which were consistent with a fast electron transfer from cytochrome a to copper A. The absorbance changes at 598 nm gave an apparent rate of 17,000 {plus minus} 2,000 s{sup {minus}1} (1more » {sigma}), at pH 7.0 and 25.5{degree}C. These changes were not observed in either the CO mixed-valence or the CO-inhibited fully reduced forms of the enzyme. The rate was fastest at about pH 8.0, falling off toward both lower and higher pHs. There was a small but clear temperature dependence. The process was also observed in the cytochrome c-cytochrome c oxidase high-affinity complex. The electron equilibration measured between cytochrome {alpha} and copper A is far faster than any rate measured or inferred previously for this process.« less

Work function and surface stability of tungsten-based thermionic electron emission cathodes

NASA Astrophysics Data System (ADS)

Jacobs, Ryan; Morgan, Dane; Booske, John

2017-11-01

Materials that exhibit a low work function and therefore easily emit electrons into vacuum form the basis of electronic devices used in applications ranging from satellite communications to thermionic energy conversion. W-Ba-O is the canonical materials system that functions as the thermionic electron emitter commercially used in a range of high-power electron devices. However, the work functions, surface stability, and kinetic characteristics of a polycrystalline W emitter surface are still not well understood or characterized. In this study, we examined the work function and surface stability of the eight lowest index surfaces of the W-Ba-O system using density functional theory methods. We found that under the typical thermionic cathode operating conditions of high temperature and low oxygen partial pressure, the most stable surface adsorbates are Ba-O species with compositions in the range of Ba0.125O-Ba0.25O per surface W atom, with O passivating all dangling W bonds and Ba creating work function-lowering surface dipoles. Wulff construction analysis reveals that the presence of O and Ba significantly alters the surface energetics and changes the proportions of surface facets present under equilibrium conditions. Analysis of previously published data on W sintering kinetics suggests that fine W particles in the size range of 100-500 nm may be at or near equilibrium during cathode synthesis and thus may exhibit surface orientation fractions well described by the calculated Wulff construction.

Dehydration of diasporite to corundite in nature and experiment

NASA Astrophysics Data System (ADS)

Feenstra, A.; Wunder, B.

2002-02-01

The diasporite-corundite rock transformation, which releases 6 8 wt% H2O in an average metabauxite, was studied experimentally. The results are compared with petrological observations on the island of Naxos (Greece), where the transformation occurred in metakarst bauxites during prograde regional metamorphism. Dehydration experiments were started with fine-grained natural diasporite embedded in marble. The samples were first annealed in the diaspore stability field, then slowly brought to the final pressure-temperature (P-T) conditions in the corundum field and kept there five to seven days. Overstepping the diaspore-corundum equilibrium by ˜30 °C at 8 kbar resulted in partial dehydration of diaspore. As with the corundum-in isograd on Naxos, the corundum grew preferentially along the bauxite-marble contact. Experiments at 17 40 kbar with T oversteps of 40 150 °C resulted in complete diaspore breakdown. A high-porosity zone containing corundum and silicates developed along the bauxite-marble boundary, resulting from the solid volume decreases associated with the diaspore-corundum and decarbonation reactions. In nature, the marble similarly behaved as a barrier for liberated fluid, as indicated by coarse corundum- chloritoid segregations along metabauxite rims. In the 30 40 kbar experiments, the porous contact zone acted as fluid pathway, allowing partial dissolution of metabauxite. This demonstrates pronounced Al, Fe, and Ti mobility at high P and T of 600 800 °C.

Effects of pressure on aqueous chemical equilibria at subzero temperatures with applications to Europa

USGS Publications Warehouse

Marion, G.M.; Kargel, J.S.; Catling, D.C.; Jakubowski, S.D.

2005-01-01

Pressure plays a critical role in controlling aqueous geochemical processes in deep oceans and deep ice. The putative ocean of Europa could have pressures of 1200 bars or higher on the seafloor, a pressure not dissimilar to the deepest ocean basin on Earth (the Mariana Trench at 1100 bars of pressure). At such high pressures, chemical thermodynamic relations need to explicitly consider pressure. A number of papers have addressed the role of pressure on equilibrium constants, activity coefficients, and the activity of water. None of these models deal, however, with processes at subzero temperatures, which may be important in cold environments on Earth and other planetary bodies. The objectives of this work were to (1) incorporate a pressure dependence into an existing geochemical model parameterized for subzero temperatures (FREZCHEM), (2) validate the model, and (3) simulate pressure-dependent processes on Europa. As part of objective 1, we examined two models for quantifying the volumetric properties of liquid water at subzero temperatures: one model is based on the measured properties of supercooled water, and the other model is based on the properties of liquid water in equilibrium with ice. The relative effect of pressure on solution properties falls in the order: equilibrium constants(K) > activity coefficients (??) > activity of water (aw). The errors (%) in our model associated with these properties, however, fall in the order: ?? > K > aw. The transposition between K and ?? is due to a more accurate model for estimating K than for estimating ??. Only activity coefficients are likely to be significantly in error. However, even in this case, the errors are likely to be only in the range of 2 to 5% up to 1000 bars of pressure. Evidence based on the pressure/temperature melting of ice and salt solution densities argue in favor of the equilibrium water model, which depends on extrapolations, for characterizing the properties of liquid water in electrolyte solutions at subzero temperatures, rather than the supercooled water model. Model-derived estimates of mixed salt solution densities and chemical equilibria as a function of pressure are in reasonably good agreement with experimental measurements. To demonstrate the usefulness of this low-temperature, high-pressure model, we examined two hypothetical cases for Europa. Case 1 dealt with the ice cover of Europa, where we asked the question: How far above the putative ocean in the ice layer could we expect to find thermodynamically stable brine pockets that could serve as habitats for life? For a hypothetical nonconvecting 20 km icy shell, this potential life zone only extends 2.8 km into the icy shell before the eutectic is reached. For the case of a nonconvecting icy shell, the cold surface of Europa precludes stable aqueous phases (habitats for life) anywhere near the surface. Case 2 compared chemical equilibria at 1 bar (based on previous work) with a more realistic 1460 bars of pressure at the base of a 100 km Europan ocean. A pressure of 1460 bars, compared to 1 bar, caused a 12 K decrease in the temperature at which ice first formed and a 11 K increase in the temperature at which MgSO4. 12H2O first formed. Remarkably, there was only a 1.2 K decrease in the eutectic temperatures between 1 and 1460 bars of pressure. Chemical systems and their response to pressure depend, ultimately, on the volumetric properties of individual constituents, which makes every system response highly individualistic. Copyright ?? 2005 Elsevier Ltd.

Equilibrium Reconstruction on the Large Helical Device

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

Samuel A. Lazerson, D. Gates, D. Monticello, H. Neilson, N. Pomphrey, A. Reiman S. Sakakibara, and Y. Suzuki

Equilibrium reconstruction is commonly applied to axisymmetric toroidal devices. Recent advances in computational power and equilibrium codes have allowed for reconstructions of three-dimensional fields in stellarators and heliotrons. We present the first reconstructions of finite beta discharges in the Large Helical Device (LHD). The plasma boundary and magnetic axis are constrained by the pressure profile from Thomson scattering. This results in a calculation of plasma beta without a-priori assumptions of the equipartition of energy between species. Saddle loop arrays place additional constraints on the equilibrium. These reconstruction utilize STELLOPT, which calls VMEC. The VMEC equilibrium code assumes good nested fluxmore » surfaces. Reconstructed magnetic fields are fed into the PIES code which relaxes this constraint allowing for the examination of the effect of islands and stochastic regions on the magnetic measurements.« less

Thermodynamic properties of gaseous fluorocarbons and isentropic equilibrium expansions of two binary mixtures of fluorocarbons and argon

NASA Technical Reports Server (NTRS)

Talcott, N. A., Jr.

1977-01-01

Equations and computer code are given for the thermodynamic properties of gaseous fluorocarbons in chemical equilibrium. In addition, isentropic equilibrium expansions of two binary mixtures of fluorocarbons and argon are included. The computer code calculates the equilibrium thermodynamic properties and, in some cases, the transport properties for the following fluorocarbons: CCl2F, CCl2F2, CBrF3, CF4, CHCl2F, CHF3, CCL2F-CCl2F, CCLF2-CClF2, CF3-CF3, and C4F8. Equilibrium thermodynamic properties are tabulated for six of the fluorocarbons(CCl3F, CCL2F2, CBrF3, CF4, CF3-CF3, and C4F8) and pressure-enthalpy diagrams are presented for CBrF3.

The free energies of partially open coronal magnetic fields

NASA Technical Reports Server (NTRS)

Low, B. C.; Smith, D. F.

1993-01-01

A simple model of the low corona is examined in terms of a static polytropic atmosphere in equilibrium with a global magnetic field. The question posed is whether magnetostatic states with partially open magnetic fields may contain magnetic energies in excess of those in fully open magnetic fields. Based on the analysis presented here, it is concluded that the cross-field electric currents in the pre-eruption corona are a viable source of the bulk of the energies in a mass ejection and its associated flare.

Effect of confinement in nano-porous materials on the solubility of a supercritical gas

NASA Astrophysics Data System (ADS)

Hu, Yaofeng; Huang, Liangliang; Zhao, Shuangliang; Liu, Honglai; Gubbins, Keith E.

2016-11-01

By combining Gibbs Ensemble Monte Carlo simulations and density functional theory, we investigate the influence of confinement in a slit-shaped carbon pore on the solubility of a supercritical solute gas in a liquid solvent. In the cases studied here, competing adsorption of the solvent and solute determines whether the solubility is enhanced or suppressed for larger pores. We find that the solubility in the confined system is strongly dependent on pore width, and that molecular packing effects are important for small pore widths. In addition, the solubility decreases on increase in the temperature, as for the bulk mixture, but the rate of decrease is greater in the pore due to a decrease in the partial molar enthalpy of the solute in the pore; this effect becomes greater as pore width is decreased. The solubility is increased on increasing the bulk pressure of the gas in equilibrium with the pore, and obeys Henry's law at lower pressures. However, the Henry constant differs significantly from that for the bulk mixture, and the range of pressure over which Henry's law applies is reduced relative to that for the bulk mixture. The latter observation indicates that solute-solute interactions become more important in the pore than for the bulk at a given bulk pressure. Finally, we note that different authors use different definitions of the solubility in pores, leading to some confusion over the reported phenomenon of 'oversolubility'. We recommend that solubility be defined as the overall mole fraction of solute in the pores, since it takes into account the increase in density of the solvent in the pores, and avoids ambiguity in the definition of the pore volume.

Reversible effects of oxygen partial pressure on genes associated with placental angiogenesis and differentiation in primary-term cytotrophoblast cell culture.

PubMed

Debiève, F; Depoix, C; Gruson, D; Hubinont, C

2013-09-01

Timely regulated changes in oxygen partial pressure are important for placental formation. Disturbances could be responsible for pregnancy-related diseases like preeclampsia and intrauterine growth restriction. We aimed to (i) determine the effect of oxygen partial pressure on cytotrophoblast differentiation; (ii) measure mRNA expression and protein secretion from genes associated with placental angiogenesis; and (iii) determine the reversibility of these effects at different oxygen partial pressures. Term cytotrophoblasts were incubated at 21% and 2.5% O2 for 96 hr, or were switched between the two oxygen concentrations after 48 hr. Real-time PCR and enzyme-linked immunosorbent assays (ELISAs) were used to evaluate cell fusion and differentiation, measuring transcript levels for those genes involved in cell fusion and placental angiogenesis, including VEGF, PlGF, VEGFR1, sVEGFR1, sENG, INHA, and GCM1. Cytotrophoblasts underwent fusion and differentiation in 2.5% O2 . PlGF expression was inhibited while sVEGFR1 expression increased. VEGF and sENG mRNA expressions increased in 2.5% compared to 21% O2 , but no protein was detected in the cell supernatants. Finally, GCM1 mRNA expression increased during trophoblast differentiation at 21% O2 , but was inhibited at 2.5% O2 . These mRNA expression effects were reversed by returning the cells to 21% O2 . Thus, low-oxygen partial pressure does not inhibit term-cytotrophoblast cell fusion and differentiation in vitro. Lowering the oxygen partial pressure from 21% to 2.5% caused normal-term trophoblasts to reversibly modify their expression of genes associated with placental angiogenesis. This suggests that modifications observed in pregnancy diseases such as preeclampsia or growth retardation are probably due to an extrinsic effect on trophoblasts. Copyright © 2013 Wiley Periodicals, Inc.

Measurement of alveolar oxygen partial pressure in the rat lung using Carr-Purcell-Meiboom-Gill spin-spin relaxation times of hyperpolarized 3He and 129Xe at 74 mT.

PubMed

Kraayvanger, Ryan J; Bidinosti, Christopher P; Dominguez-Viqueira, William; Parra-Robles, Juan; Fox, Matthew; Lam, Wilfred W; Santyr, Giles E

2010-11-01

Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, (3) He and (129) Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R(2) ) of (3) He at low magnetic field strengths (<0.1 T) in vivo. R(2) measurements can be achieved efficiently using the Carr-Purcell-Meiboom-Gill pulse sequence. In this work, alveolar oxygen partial pressure measurements based on Carr-Purcell-Meiboom-Gill R(2) values of hyperpolarized (3) He and (129) Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for (3) He and (129) Xe were determined to be (5.2 ± 0.6) × 10(-6) Pa(-1) sec(-1) and (7.3 ± 0.4) × 10(-6) Pa(-1) s(-1) compared with spin-lattice relaxivity constants of (4.0 ± 0.4) × 10(-6) Pa(-1) s(-1) and (4.3 ± 1.3) × 10(-6) Pa(-1) s(-1), respectively. In vivo experimental measurements of alveolar oxygen partial pressure using (3) He in whole rat lung show good agreement (r(2) = 0.973) with predictions based on lung volumes and ventilation parameters. For (129) Xe, multicomponent relaxation was observed with one component exhibiting an increase in R(2) with decreasing alveolar oxygen partial pressure. Copyright © 2010 Wiley-Liss, Inc.

Structure and stabilizing interactions of casein micelles probed by high-pressure light scattering and FTIR.

PubMed

Gebhardt, Ronald; Takeda, Naohiro; Kulozik, Ulrich; Doster, Wolfgang

2011-03-17

Caseins form heterogeneous micelles composed of three types of disordered protein chains (α, β, κ), which include protein-bound calcium phosphate particles. We probe the stability limits of the micelle by applying hydrostatic pressure. The resulting changes of the size distribution and the average molecular weight are recorded in situ with static and dynamic light scattering. Pressure induces irreversible dissociation of the micelles into monomers above a critical value depending on their size. The critical pressure increases with temperature, pH, and calcium concentration due to the interplay of hydrophobic and electrostatic interactions. The pressure transition curves are biphasic, reflecting the equilibrium of two micelle states with different stability, average size, entropy, and calcium bound. The fast process of pressure dissociation is used to probe the slow equilibrium of the two micelle states under various conditions. Binding and release of β-casein from the micelle is suggested as the molecular mechanism of stabilization associated with the two states. In situ FTIR spectroscopy covering the P-O stretching region indicates that bound calcium phosphate particles are released from serine phosphate residues at pressures above 100 MPa. The resulting imbalance of charge triggers the complete decomposition of the micelle. © 2011 American Chemical Society

Liquid suspensions of reversible metal hydrides

DOEpatents

Reilly, J.J.; Grohse, E.W.; Winsche, W.E.

1983-12-08

The reversibility of the process M + x/2 H/sub 2/ ..-->.. MH/sub x/, where M is a metal hydride former that forms a hydride MH/sub x/ in the presence of H/sub 2/, generally used to store and recall H/sub 2/, is found to proceed under a liquid, thereby to reduce contamination, provide better temperature control and provide in situ mobility of the reactants. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to temperature and pressure controlled atmosphere containing H/sub 2/, to store hydrogen (at high pressures) and to release (at low pressures) previously stored hydrogen. The direction of the flow of the H/sub 2/ through the liquid is dependent upon the H/sub 2/ pressure in the gas phase at a given temperature. When the former is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particle. When the H/sub 2/ pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

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.

The effects of endothelin-1 on the cardiorespiratory physiology of the freshwater trout (Oncorhynchus mykiss) and the marine dogfish (Squalus acanthias).

PubMed

Perry, S F; Montpetit, C J; McKendry, J; Desforges, P R; Gilmour, K M; Wood, C M; Olson, K R

2001-11-01

The aim of the present study was to evaluate the effects of endothelin-l-elicited cardiovascular events on respiratory gas transfer in the freshwater rainbow trout (Oncorhynchus mykiss) and the marine dogfish (Squalus acanthias). In both species, endothelin-1 (666 pmol kg(-1)) caused a rapid (within 4 min) reduction (ca. 30-50 mmHg) in arterial blood partial pressure of O2. The effects of endothelin-1 on arterial blood partial pressure of CO2 were not synchronised with the changes in O2 partial pressure and the responses were markedly different in trout and dogfish. In trout, arterial CO2 partial pressure was increased transiently by approximately 1.0 mmHg but the onset of the response was delayed and occurred 12 min after endothelin-1 injection. In contrast, CO2 partial pressure remained more-or-less constant in dogfish after injection of endothelin-1 and was increased only slightly (approximately 0.1 mmHg) after 60 min. Pre-treatment of trout with bovine carbonic anhydrase (5 mg ml(-1)) eliminated the increase in CO2 partial pressure that was normally observed after endothelin-1 injection. In both species, endothelin-1 injection caused a decrease in arterial blood pH that mirrored the changes in CO2 partial pressure. Endothelin-1 injection was associated with transient (trout) or persistent (dogfish) hyperventilation as indicated by pronounced increases in breathing frequency and amplitude. In trout, arterial blood pressure remained constant or was decreased slightly and was accompanied by a transient increase in systemic resistance, and a temporary reduction in cardiac output. The decrease in cardiac output was caused solely by a reduction in cardiac frequency; cardiac stroke volume was unaffected. In dogfish, arterial blood pressure was lowered by approximately 10 mmHg at 6-10 min after endothelin-1 injection but then was rapidly restored to pre-injection levels. The decrease in arterial blood pressure reflected an increase in branchial vascular resistance (as determined using in situ perfused gill preparations) that was accompanied by simultaneous decreases in systemic resistance and cardiac output. Cardiac frequency and stroke volume were reduced by endothelin-1 injection and thus both variables contributed to the changes in cardiac output. We conclude that the net consequences of endothelin-1 on arterial blood gases result from the opposing effects of reduced gill functional surface area (caused by vasoconstriction) and an increase in blood residence time within the gill (caused by decreased cardiac output.

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

Oxidation Behavior of Carbon Fiber-Reinforced Composites

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

2008-01-01

OXIMAP is a numerical (FEA-based) solution tool capable of calculating the carbon fiber and fiber coating oxidation patterns within any arbitrarily shaped carbon silicon carbide composite structure as a function of time, temperature, and the environmental oxygen partial pressure. The mathematical formulation is derived from the mechanics of the flow of ideal gases through a chemically reacting, porous solid. The result of the formulation is a set of two coupled, non-linear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined at each time step using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The non-linear differential equations are cast into matrix equations by applying the Bubnov-Galerkin weighted residual finite element method, allowing for the solution of the differential equations numerically.

Effects of various oxygen partial pressures on Ti-doped ZnO thin film transistors fabricated on flexible plastic substrate

NASA Astrophysics Data System (ADS)

Cui, Guodong; Han, Dedong; Yu, Wen; Shi, Pan; Zhang, Yi; Huang, Lingling; Cong, Yingying; Zhou, Xiaoliang; Zhang, Xiaomi; Zhang, Shengdong; Zhang, Xing; Wang, Yi

2016-04-01

By applying a novel active layer of titanium zinc oxide (TiZO), we have successfully fabricated fully transparent thin-film transistors (TFTs) with a bottom gate structure fabricated on a flexible plastic substrate at low temperatures. The effects of various oxygen partial pressures during channel deposition were studied to improve the device performance. We found that the oxygen partial pressure during channel deposition has a significant impact on the performance of TiZO TFTs, and that the TFT developed under 10% oxygen partial pressure exhibits superior performance with a low threshold voltage (V th) of 2.37 V, a high saturation mobility (μsat) of 125.4 cm2 V-1 s-1, a steep subthreshold swing (SS) of 195 mV/decade and a high I on/I off ratio of 3.05 × 108. These results suggest that TiZO thin films are promising for high-performance fully transparent flexible TFTs and displays.

[Correlation between the inspired fraction of oxygen, maternal partial oxygen pressure, and fetal partial oxygen pressure during cesarean section of normal pregnancies].

PubMed

Castro, Carlos Henrique Viana de; Cruvinel, Marcos Guilherme Cunha; Carneiro, Fabiano Soares; Silva, Yerkes Pereira; Cabral, Antônio Carlos Vieira; Bessa, Roberto Cardoso

2009-01-01

Despite changes in pulmonary function, maternal oxygenation is maintained during obstetric regional blocks. But in those situations, the administration of supplementary oxygen to parturients is a common practice. Good fetal oxygenation is the main justification; however, this has not been proven. The objective of this randomized, prospective study was to test the hypothesis of whether maternal hyperoxia is correlated with an increase in fetal gasometric parameters in elective cesarean sections. Arterial blood gases of 20 parturients undergoing spinal block with different inspired fractions of oxygen were evaluated and correlated with fetal arterial blood gases. An increase in maternal inspired fraction of oxygen did not show any correlation with an increase of fetal partial oxygen pressure. Induction of maternal hyperoxia by the administration of supplementary oxygen did not increase fetal partial oxygen pressure. Fetal gasometric parameters did not change even when maternal parameters changed, induced by hyperoxia, during cesarean section under spinal block.

Respiratory gas exchange of high altitude adapted chick embryos

NASA Technical Reports Server (NTRS)

Wangensteen, O. D.; Rahn, H.; Burton, R. R.; Smith, A. H.

1974-01-01

Study of gas exchange by embryos from chickens acclimatized to an altitude of 3800 m. The oxygen partial pressure and carbon dioxide partial pressure differences across the egg shell were measured and found to be less than the values previously reported for sea-level eggs by about a factor of two. Further measurements of embryonic oxygen consumption and shell conductivity to oxygen indicated that, compared to eggs at sea level, oxygen consumption was reduced by a factor of 0.58 while conductivity to oxygen was increased only by a factor of 1.07 in the high-altitude eggs. These independent measurements predict the change in oxygen partial pressure across the egg shell of the high-altitude eggs to be only 0.54 times that of sea-level eggs; the directly measured factor was 0.53. The authors conclude that at high altitude, a major adaptation of the chick embryo is a reduced metabolism which decreases the change in oxygen partial pressure across the egg shell since its gas conductivity remains essentially unchanged.

Biomass hydrolysis inhibition at high hydrogen partial pressure in solid-state anaerobic digestion.

PubMed

Cazier, E A; Trably, E; Steyer, J P; Escudie, R

2015-08-01

In solid-state anaerobic digestion, so-called ss-AD, biogas production is inhibited at high total solids contents. Such inhibition is likely caused by a slow diffusion of dissolved reaction intermediates that locally accumulate. In this study, we investigated the effect of H2 and CO2 partial pressure on ss-AD. Partial pressure of H2 and/or CO2 was artificially fixed, from 0 to 1 557mbars for H2 and from 0 to 427mbars for CO2. High partial pressure of H2 showed a significant effect on methanogenesis, while CO2 had no impact. At high [Formula: see text] , the overall substrate degradation decreased with no accumulation of metabolites from acidogenic bacteria, indicating that the hydrolytic activity was specifically impacted. Interestingly, such inhibition did not occur when CO2 was added with H2. This result suggests that CO2 gas transfer is probably a key factor in ss-AD from biomass. Copyright © 2015 Elsevier Ltd. All rights reserved.